Increase partial backup timeout to 3 hours

fix: do not create metrics contention from background task permit (#7730 )
The background task loop permit metrics do two of `with_label_values` very often. Change the codepath to cache the counters on first access into a `Lazy` with `enum_map::EnumMap`. The expectation is that this should not fix for metric collection failures under load, but it doesn't hurt. Cc: #7161
2026-02-02 02:00:38 +00:00 · 2024-05-13 16:57:31 +02:00 · 2024-05-13 17:49:50 +03:00 · 2024-05-13 14:16:03 +01:00 · 2024-05-13 14:52:06 +02:00 · 2024-05-13 13:41:14 +01:00
248 changed files with 9442 additions and 3132 deletions
--- a/.config/nextest.toml
+++ b/.config/nextest.toml
@@ -1,2 +1,2 @@
 [profile.default]
-slow-timeout = { period = "20s", terminate-after = 3 }
+slow-timeout = { period = "60s", terminate-after = 3 }
--- a/.github/actionlint.yml
+++ b/.github/actionlint.yml
@@ -1,11 +1,9 @@
 self-hosted-runner:
  labels:
    - arm64
-    - dev
    - gen3
    - large
-    # Remove `macos-14` from the list after https://github.com/rhysd/actionlint/pull/392 is merged.
-    - macos-14
+    - large-arm64
    - small
    - us-east-2
 config-variables:
--- a/.github/workflows/build-build-tools-image.yml
+++ b/.github/workflows/build-build-tools-image.yml
@@ -39,7 +39,7 @@ jobs:
      matrix:
        arch: [ x64, arm64 ]

-    runs-on: ${{ fromJson(format('["self-hosted", "dev", "{0}"]', matrix.arch)) }}
+    runs-on: ${{ fromJson(format('["self-hosted", "gen3", "{0}"]', matrix.arch == 'arm64' && 'large-arm64' || 'large')) }}

    env:
      IMAGE_TAG: ${{ inputs.image-tag }}
--- a/.github/workflows/build_and_test.yml
+++ b/.github/workflows/build_and_test.yml
@@ -236,27 +236,6 @@ jobs:
          submodules: true
          fetch-depth: 1

-      - name: Check Postgres submodules revision
-        shell: bash -euo pipefail {0}
-        run: |
-          # This is a temporary solution to ensure that the Postgres submodules revision is correct (i.e. the updated intentionally).
-          # Eventually it will be replaced by a regression test https://github.com/neondatabase/neon/pull/4603
-
-          FAILED=false
-          for postgres in postgres-v14 postgres-v15 postgres-v16; do
-            expected=$(cat vendor/revisions.json | jq --raw-output '."'"${postgres}"'"')
-            actual=$(git rev-parse "HEAD:vendor/${postgres}")
-            if [ "${expected}" != "${actual}" ]; then
-              echo >&2 "Expected ${postgres} rev to be at '${expected}', but it is at '${actual}'"
-              FAILED=true
-            fi
-          done
-
-          if [ "${FAILED}" = "true" ]; then
-            echo >&2 "Please update vendor/revisions.json if these changes are intentional"
-            exit 1
-          fi
-
      - name: Set pg 14 revision for caching
        id: pg_v14_rev
        run: echo pg_rev=$(git rev-parse HEAD:vendor/postgres-v14) >> $GITHUB_OUTPUT
@@ -362,6 +341,9 @@ jobs:
        env:
          NEXTEST_RETRIES: 3
        run: |
+          #nextest does not yet support running doctests
+          cargo test --doc $CARGO_FLAGS $CARGO_FEATURES
+
          for io_engine in std-fs tokio-epoll-uring ; do
            NEON_PAGESERVER_UNIT_TEST_VIRTUAL_FILE_IOENGINE=$io_engine ${cov_prefix} cargo nextest run $CARGO_FLAGS $CARGO_FEATURES
          done
@@ -564,9 +546,27 @@ jobs:
      # XXX: no coverage data handling here, since benchmarks are run on release builds,
      # while coverage is currently collected for the debug ones

+  report-benchmarks-failures:
+    needs: [ benchmarks, create-test-report ]
+    if: github.ref_name == 'main' && failure()
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: slackapi/slack-github-action@v1
+      with:
+        channel-id: C060CNA47S9 # on-call-staging-storage-stream
+        slack-message: |
+          Benchmarks failed on main: ${{ github.event.head_commit.url }}
+
+          Allure report: ${{ needs.create-test-report.outputs.report-url }}
+      env:
+        SLACK_BOT_TOKEN: ${{ secrets.SLACK_BOT_TOKEN }}
+
  create-test-report:
    needs: [ check-permissions, regress-tests, coverage-report, benchmarks, build-build-tools-image ]
    if: ${{ !cancelled() && contains(fromJSON('["skipped", "success"]'), needs.check-permissions.result) }}
+    outputs:
+      report-url: ${{ steps.create-allure-report.outputs.report-url }}

    runs-on: [ self-hosted, gen3, small ]
    container:
--- a/.github/workflows/neon_extra_builds.yml
+++ b/.github/workflows/neon_extra_builds.yml
@@ -136,7 +136,7 @@ jobs:
  check-linux-arm-build:
    needs: [ check-permissions, build-build-tools-image ]
    timeout-minutes: 90
-    runs-on: [ self-hosted, dev, arm64 ]
+    runs-on: [ self-hosted, large-arm64 ]

    env:
      # Use release build only, to have less debug info around
@@ -232,20 +232,20 @@ jobs:

      - name: Run cargo build
        run: |
-          mold -run cargo build --locked $CARGO_FLAGS $CARGO_FEATURES --bins --tests
+          mold -run cargo build --locked $CARGO_FLAGS $CARGO_FEATURES --bins --tests -j$(nproc)

      - name: Run cargo test
        env:
          NEXTEST_RETRIES: 3
        run: |
-          cargo nextest run $CARGO_FEATURES
+          cargo nextest run $CARGO_FEATURES -j$(nproc)

          # Run separate tests for real S3
          export ENABLE_REAL_S3_REMOTE_STORAGE=nonempty
          export REMOTE_STORAGE_S3_BUCKET=neon-github-ci-tests
          export REMOTE_STORAGE_S3_REGION=eu-central-1
          # Avoid `$CARGO_FEATURES` since there's no `testing` feature in the e2e tests now
-          cargo nextest run --package remote_storage --test test_real_s3
+          cargo nextest run --package remote_storage --test test_real_s3 -j$(nproc)

          # Run separate tests for real Azure Blob Storage
          # XXX: replace region with `eu-central-1`-like region
@@ -255,12 +255,12 @@ jobs:
          export REMOTE_STORAGE_AZURE_CONTAINER="${{ vars.REMOTE_STORAGE_AZURE_CONTAINER }}"
          export REMOTE_STORAGE_AZURE_REGION="${{ vars.REMOTE_STORAGE_AZURE_REGION }}"
          # Avoid `$CARGO_FEATURES` since there's no `testing` feature in the e2e tests now
-          cargo nextest run --package remote_storage --test test_real_azure
+          cargo nextest run --package remote_storage --test test_real_azure -j$(nproc)

  check-codestyle-rust-arm:
    needs: [ check-permissions, build-build-tools-image ]
    timeout-minutes: 90
-    runs-on: [ self-hosted, dev, arm64 ]
+    runs-on: [ self-hosted, large-arm64 ]

    container:
      image: ${{ needs.build-build-tools-image.outputs.image }}
@@ -269,6 +269,11 @@ jobs:
        password: ${{ secrets.NEON_DOCKERHUB_PASSWORD }}
      options: --init

+    strategy:
+      fail-fast: false
+      matrix:
+        build_type: [ debug, release ]
+
    steps:
      - name: Fix git ownership
        run: |
@@ -305,31 +310,35 @@ jobs:
            exit 1
          fi
          echo "CLIPPY_COMMON_ARGS=${CLIPPY_COMMON_ARGS}" >> $GITHUB_ENV
+
      - name: Run cargo clippy (debug)
+        if: matrix.build_type == 'debug'
        run: cargo hack --feature-powerset clippy $CLIPPY_COMMON_ARGS
      - name: Run cargo clippy (release)
+        if: matrix.build_type == 'release'
        run: cargo hack --feature-powerset clippy --release $CLIPPY_COMMON_ARGS

      - name: Check documentation generation
-        run: cargo doc --workspace --no-deps --document-private-items
+        if: matrix.build_type == 'release'
+        run: cargo doc --workspace --no-deps --document-private-items -j$(nproc)
        env:
            RUSTDOCFLAGS: "-Dwarnings -Arustdoc::private_intra_doc_links"

      # Use `${{ !cancelled() }}` to run quck tests after the longer clippy run
      - name: Check formatting
-        if: ${{ !cancelled() }}
+        if: ${{ !cancelled() && matrix.build_type == 'release' }}
        run: cargo fmt --all -- --check

      # https://github.com/facebookincubator/cargo-guppy/tree/bec4e0eb29dcd1faac70b1b5360267fc02bf830e/tools/cargo-hakari#2-keep-the-workspace-hack-up-to-date-in-ci
      - name: Check rust dependencies
-        if: ${{ !cancelled() }}
+        if: ${{ !cancelled() && matrix.build_type == 'release' }}
        run: |
          cargo hakari generate --diff  # workspace-hack Cargo.toml is up-to-date
          cargo hakari manage-deps --dry-run  # all workspace crates depend on workspace-hack

      # https://github.com/EmbarkStudios/cargo-deny
      - name: Check rust licenses/bans/advisories/sources
-        if: ${{ !cancelled() }}
+        if: ${{ !cancelled() && matrix.build_type == 'release' }}
        run: cargo deny check

  gather-rust-build-stats:
@@ -338,7 +347,7 @@ jobs:
      contains(github.event.pull_request.labels.*.name, 'run-extra-build-stats') ||
      contains(github.event.pull_request.labels.*.name, 'run-extra-build-*') ||
      github.ref_name == 'main'
-    runs-on: [ self-hosted, gen3, large ]
+    runs-on: [ self-hosted, large ]
    container:
      image: ${{ needs.build-build-tools-image.outputs.image }}
      credentials:
@@ -369,7 +378,7 @@ jobs:
        run: make walproposer-lib -j$(nproc)

      - name: Produce the build stats
-        run: cargo build --all --release --timings
+        run: cargo build --all --release --timings -j$(nproc)

      - name: Upload the build stats
        id: upload-stats
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -25,9 +25,9 @@ checksum = "f26201604c87b1e01bd3d98f8d5d9a8fcbb815e8cedb41ffccbeb4bf593a35fe"

 [[package]]
 name = "ahash"
-version = "0.8.9"
+version = "0.8.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d713b3834d76b85304d4d525563c1276e2e30dc97cc67bfb4585a4a29fc2c89f"
+checksum = "e89da841a80418a9b391ebaea17f5c112ffaaa96f621d2c285b5174da76b9011"
 dependencies = [
 "cfg-if",
 "const-random",
@@ -284,9 +284,9 @@ checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"

 [[package]]
 name = "aws-config"
-version = "1.1.4"
+version = "1.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8b30c39ebe61f75d1b3785362b1586b41991873c9ab3e317a9181c246fb71d82"
+checksum = "baaa0be6ee7d90b775ae6ccb6d2ba182b91219ec2001f92338773a094246af1d"
 dependencies = [
 "aws-credential-types",
 "aws-runtime",
@@ -309,14 +309,15 @@ dependencies = [
 "time",
 "tokio",
 "tracing",
+ "url",
 "zeroize",
 ]

 [[package]]
 name = "aws-credential-types"
-version = "1.1.8"
+version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fa8587ae17c8e967e4b05a62d495be2fb7701bec52a97f7acfe8a29f938384c8"
+checksum = "e16838e6c9e12125face1c1eff1343c75e3ff540de98ff7ebd61874a89bcfeb9"
 dependencies = [
 "aws-smithy-async",
 "aws-smithy-runtime-api",
@@ -326,9 +327,9 @@ dependencies = [

 [[package]]
 name = "aws-runtime"
-version = "1.1.8"
+version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b13dc54b4b49f8288532334bba8f87386a40571c47c37b1304979b556dc613c8"
+checksum = "785da4a15e7b166b505fd577e4560c7a7cd8fbdf842eb1336cbcbf8944ce56f1"
 dependencies = [
 "aws-credential-types",
 "aws-sigv4",
@@ -373,10 +374,11 @@ dependencies = [

 [[package]]
 name = "aws-sdk-s3"
-version = "1.14.0"
+version = "1.26.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "951f7730f51a2155c711c85c79f337fbc02a577fa99d2a0a8059acfce5392113"
+checksum = "7bc5ce518d4b8d16e0408de7bdf1b3097cec61a7daa979750a208f8d9934386d"
 dependencies = [
+ "ahash",
 "aws-credential-types",
 "aws-runtime",
 "aws-sigv4",
@@ -391,20 +393,25 @@ dependencies = [
 "aws-smithy-xml",
 "aws-types",
 "bytes",
+ "fastrand 2.0.0",
+ "hex",
+ "hmac",
 "http 0.2.9",
 "http-body 0.4.5",
+ "lru",
 "once_cell",
 "percent-encoding",
 "regex-lite",
+ "sha2",
 "tracing",
 "url",
 ]

 [[package]]
 name = "aws-sdk-sso"
-version = "1.12.0"
+version = "1.22.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f486420a66caad72635bc2ce0ff6581646e0d32df02aa39dc983bfe794955a5b"
+checksum = "ca3d6c4cba4e009391b72b0fcf12aff04ea3c9c3aa2ecaafa330326a8bd7e601"
 dependencies = [
 "aws-credential-types",
 "aws-runtime",
@@ -424,9 +431,9 @@ dependencies = [

 [[package]]
 name = "aws-sdk-ssooidc"
-version = "1.12.0"
+version = "1.22.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "39ddccf01d82fce9b4a15c8ae8608211ee7db8ed13a70b514bbfe41df3d24841"
+checksum = "73400dc239d14f63d932f4ca7b55af5e9ef1f857f7d70655249ccc287adb2570"
 dependencies = [
 "aws-credential-types",
 "aws-runtime",
@@ -446,9 +453,9 @@ dependencies = [

 [[package]]
 name = "aws-sdk-sts"
-version = "1.12.0"
+version = "1.22.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1a591f8c7e6a621a501b2b5d2e88e1697fcb6274264523a6ad4d5959889a41ce"
+checksum = "10f8858308af76fba3e5ffcf1bb56af5471574d2bdfaf0159470c25bc2f760e5"
 dependencies = [
 "aws-credential-types",
 "aws-runtime",
@@ -469,9 +476,9 @@ dependencies = [

 [[package]]
 name = "aws-sigv4"
-version = "1.2.0"
+version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "11d6f29688a4be9895c0ba8bef861ad0c0dac5c15e9618b9b7a6c233990fc263"
+checksum = "58b56f1cbe6fd4d0c2573df72868f20ab1c125ca9c9dbce17927a463433a2e57"
 dependencies = [
 "aws-credential-types",
 "aws-smithy-eventstream",
@@ -498,9 +505,9 @@ dependencies = [

 [[package]]
 name = "aws-smithy-async"
-version = "1.1.8"
+version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d26ea8fa03025b2face2b3038a63525a10891e3d8829901d502e5384a0d8cd46"
+checksum = "62220bc6e97f946ddd51b5f1361f78996e704677afc518a4ff66b7a72ea1378c"
 dependencies = [
 "futures-util",
 "pin-project-lite",
@@ -509,9 +516,9 @@ dependencies = [

 [[package]]
 name = "aws-smithy-checksums"
-version = "0.60.4"
+version = "0.60.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "be2acd1b9c6ae5859999250ed5a62423aedc5cf69045b844432de15fa2f31f2b"
+checksum = "83fa43bc04a6b2441968faeab56e68da3812f978a670a5db32accbdcafddd12f"
 dependencies = [
 "aws-smithy-http",
 "aws-smithy-types",
@@ -541,9 +548,9 @@ dependencies = [

 [[package]]
 name = "aws-smithy-http"
-version = "0.60.7"
+version = "0.60.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3f10fa66956f01540051b0aa7ad54574640f748f9839e843442d99b970d3aff9"
+checksum = "4a7de001a1b9a25601016d8057ea16e31a45fdca3751304c8edf4ad72e706c08"
 dependencies = [
 "aws-smithy-eventstream",
 "aws-smithy-runtime-api",
@@ -581,9 +588,9 @@ dependencies = [

 [[package]]
 name = "aws-smithy-runtime"
-version = "1.1.8"
+version = "1.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ec81002d883e5a7fd2bb063d6fb51c4999eb55d404f4fff3dd878bf4733b9f01"
+checksum = "c9ac79e9f3a4d576f3cd4a470a0275b138d9e7b11b1cd514a6858ae0a79dd5bb"
 dependencies = [
 "aws-smithy-async",
 "aws-smithy-http",
@@ -594,8 +601,9 @@ dependencies = [
 "h2 0.3.26",
 "http 0.2.9",
 "http-body 0.4.5",
+ "http-body 1.0.0",
 "hyper 0.14.26",
- "hyper-rustls",
+ "hyper-rustls 0.24.0",
 "once_cell",
 "pin-project-lite",
 "pin-utils",
@@ -606,9 +614,9 @@ dependencies = [

 [[package]]
 name = "aws-smithy-runtime-api"
-version = "1.2.0"
+version = "1.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9acb931e0adaf5132de878f1398d83f8677f90ba70f01f65ff87f6d7244be1c5"
+checksum = "04ec42c2f5c0e7796a2848dde4d9f3bf8ce12ccbb3d5aa40c52fa0cdd61a1c47"
 dependencies = [
 "aws-smithy-async",
 "aws-smithy-types",
@@ -623,16 +631,19 @@ dependencies = [

 [[package]]
 name = "aws-smithy-types"
-version = "1.1.8"
+version = "1.1.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "abe14dceea1e70101d38fbf2a99e6a34159477c0fb95e68e05c66bd7ae4c3729"
+checksum = "baf98d97bba6ddaba180f1b1147e202d8fe04940403a95a3f826c790f931bbd1"
 dependencies = [
 "base64-simd",
 "bytes",
 "bytes-utils",
 "futures-core",
 "http 0.2.9",
+ "http 1.1.0",
 "http-body 0.4.5",
+ "http-body 1.0.0",
+ "http-body-util",
 "itoa",
 "num-integer",
 "pin-project-lite",
@@ -646,18 +657,18 @@ dependencies = [

 [[package]]
 name = "aws-smithy-xml"
-version = "0.60.7"
+version = "0.60.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "872c68cf019c0e4afc5de7753c4f7288ce4b71663212771bf5e4542eb9346ca9"
+checksum = "d123fbc2a4adc3c301652ba8e149bf4bc1d1725affb9784eb20c953ace06bf55"
 dependencies = [
 "xmlparser",
 ]

 [[package]]
 name = "aws-types"
-version = "1.1.8"
+version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0dbf2f3da841a8930f159163175cf6a3d16ddde517c1b0fba7aa776822800f40"
+checksum = "5a43b56df2c529fe44cb4d92bd64d0479883fb9608ff62daede4df5405381814"
 dependencies = [
 "aws-credential-types",
 "aws-smithy-async",
@@ -684,7 +695,7 @@ dependencies = [
 "http-body 0.4.5",
 "hyper 0.14.26",
 "itoa",
- "matchit",
+ "matchit 0.7.0",
 "memchr",
 "mime",
 "percent-encoding",
@@ -740,7 +751,7 @@ dependencies = [
 "pin-project",
 "quick-xml",
 "rand 0.8.5",
- "reqwest",
+ "reqwest 0.11.19",
 "rustc_version",
 "serde",
 "serde_json",
@@ -865,6 +876,12 @@ version = "0.21.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3f1e31e207a6b8fb791a38ea3105e6cb541f55e4d029902d3039a4ad07cc4105"

+[[package]]
+name = "base64"
+version = "0.22.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72b3254f16251a8381aa12e40e3c4d2f0199f8c6508fbecb9d91f575e0fbb8c6"
+
 [[package]]
 name = "base64-simd"
 version = "0.8.0"
@@ -1210,7 +1227,7 @@ dependencies = [
 "postgres",
 "regex",
 "remote_storage",
- "reqwest",
+ "reqwest 0.12.4",
 "rust-ini",
 "serde",
 "serde_json",
@@ -1329,7 +1346,7 @@ dependencies = [
 "postgres_backend",
 "postgres_connection",
 "regex",
- "reqwest",
+ "reqwest 0.12.4",
 "safekeeper_api",
 "scopeguard",
 "serde",
@@ -1342,6 +1359,7 @@ dependencies = [
 "tokio-postgres",
 "tokio-util",
 "toml",
+ "toml_edit",
 "tracing",
 "url",
 "utils",
@@ -2363,6 +2381,17 @@ dependencies = [
 "winapi",
 ]

+[[package]]
+name = "hostname"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f9c7c7c8ac16c798734b8a24560c1362120597c40d5e1459f09498f8f6c8f2ba"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "windows 0.52.0",
+]
+
 [[package]]
 name = "http"
 version = "0.2.9"
@@ -2509,6 +2538,7 @@ dependencies = [
 "pin-project-lite",
 "smallvec",
 "tokio",
+ "want",
 ]

 [[package]]
@@ -2526,6 +2556,23 @@ dependencies = [
 "tokio-rustls 0.24.0",
 ]

+[[package]]
+name = "hyper-rustls"
+version = "0.26.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a0bea761b46ae2b24eb4aef630d8d1c398157b6fc29e6350ecf090a0b70c952c"
+dependencies = [
+ "futures-util",
+ "http 1.1.0",
+ "hyper 1.2.0",
+ "hyper-util",
+ "rustls 0.22.4",
+ "rustls-pki-types",
+ "tokio",
+ "tokio-rustls 0.25.0",
+ "tower-service",
+]
+
 [[package]]
 name = "hyper-timeout"
 version = "0.4.1"
@@ -2573,6 +2620,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ca38ef113da30126bbff9cd1705f9273e15d45498615d138b0c20279ac7a76aa"
 dependencies = [
 "bytes",
+ "futures-channel",
 "futures-util",
 "http 1.1.0",
 "http-body 1.0.0",
@@ -2580,6 +2628,9 @@ dependencies = [
 "pin-project-lite",
 "socket2 0.5.5",
 "tokio",
+ "tower",
+ "tower-service",
+ "tracing",
 ]

 [[package]]
@@ -2593,7 +2644,7 @@ dependencies = [
 "iana-time-zone-haiku",
 "js-sys",
 "wasm-bindgen",
- "windows",
+ "windows 0.48.0",
 ]

 [[package]]
@@ -2895,6 +2946,15 @@ version = "0.4.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b5e6163cb8c49088c2c36f57875e58ccd8c87c7427f7fbd50ea6710b2f3f2e8f"

+[[package]]
+name = "lru"
+version = "0.12.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d3262e75e648fce39813cb56ac41f3c3e3f65217ebf3844d818d1f9398cfb0dc"
+dependencies = [
+ "hashbrown 0.14.0",
+]
+
 [[package]]
 name = "match_cfg"
 version = "0.1.0"
@@ -2916,6 +2976,12 @@ version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b87248edafb776e59e6ee64a79086f65890d3510f2c656c000bf2a7e8a0aea40"

+[[package]]
+name = "matchit"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "540f1c43aed89909c0cc0cc604e3bb2f7e7a341a3728a9e6cfe760e733cd11ed"
+
 [[package]]
 name = "md-5"
 version = "0.10.5"
@@ -3049,16 +3115,6 @@ version = "0.3.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6877bb514081ee2a7ff5ef9de3281f14a4dd4bceac4c09388074a6b5df8a139a"

-[[package]]
-name = "mime_guess"
-version = "2.0.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4192263c238a5f0d0c6bfd21f336a313a4ce1c450542449ca191bb657b4642ef"
-dependencies = [
- "mime",
- "unicase",
-]
-
 [[package]]
 name = "minimal-lexical"
 version = "0.2.1"
@@ -3402,7 +3458,7 @@ dependencies = [
 "bytes",
 "http 0.2.9",
 "opentelemetry_api",
- "reqwest",
+ "reqwest 0.11.19",
 ]

 [[package]]
@@ -3420,7 +3476,7 @@ dependencies = [
 "opentelemetry_api",
 "opentelemetry_sdk",
 "prost",
- "reqwest",
+ "reqwest 0.11.19",
 "thiserror",
 "tokio",
 "tonic",
@@ -3649,7 +3705,7 @@ dependencies = [
 "rand 0.8.5",
 "regex",
 "remote_storage",
- "reqwest",
+ "reqwest 0.12.4",
 "rpds",
 "scopeguard",
 "serde",
@@ -3719,7 +3775,7 @@ dependencies = [
 "futures",
 "pageserver_api",
 "postgres",
- "reqwest",
+ "reqwest 0.12.4",
 "serde",
 "thiserror",
 "tokio",
@@ -4328,7 +4384,7 @@ dependencies = [
 "hashlink",
 "hex",
 "hmac",
- "hostname",
+ "hostname 0.3.1",
 "http 1.1.0",
 "http-body-util",
 "humantime",
@@ -4336,6 +4392,7 @@ dependencies = [
 "hyper 1.2.0",
 "hyper-tungstenite",
 "hyper-util",
+ "indexmap 2.0.1",
 "ipnet",
 "itertools",
 "lasso",
@@ -4361,7 +4418,7 @@ dependencies = [
 "redis",
 "regex",
 "remote_storage",
- "reqwest",
+ "reqwest 0.12.4",
 "reqwest-middleware",
 "reqwest-retry",
 "reqwest-tracing",
@@ -4388,6 +4445,7 @@ dependencies = [
 "tokio-postgres-rustls",
 "tokio-rustls 0.25.0",
 "tokio-util",
+ "tower-service",
 "tracing",
 "tracing-opentelemetry",
 "tracing-subscriber",
@@ -4678,6 +4736,7 @@ dependencies = [
 "scopeguard",
 "serde",
 "serde_json",
+ "sync_wrapper",
 "test-context",
 "tokio",
 "tokio-stream",
@@ -4703,69 +4762,106 @@ dependencies = [
 "http 0.2.9",
 "http-body 0.4.5",
 "hyper 0.14.26",
- "hyper-rustls",
 "hyper-tls",
 "ipnet",
 "js-sys",
 "log",
 "mime",
- "mime_guess",
 "native-tls",
 "once_cell",
 "percent-encoding",
 "pin-project-lite",
- "rustls 0.21.11",
- "rustls-pemfile 1.0.2",
 "serde",
 "serde_json",
 "serde_urlencoded",
 "tokio",
 "tokio-native-tls",
- "tokio-rustls 0.24.0",
 "tokio-util",
 "tower-service",
 "url",
 "wasm-bindgen",
 "wasm-bindgen-futures",
- "wasm-streams",
+ "wasm-streams 0.3.0",
 "web-sys",
- "webpki-roots 0.25.2",
- "winreg",
+ "winreg 0.50.0",
+]
+
+[[package]]
+name = "reqwest"
+version = "0.12.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "566cafdd92868e0939d3fb961bd0dc25fcfaaed179291093b3d43e6b3150ea10"
+dependencies = [
+ "base64 0.22.1",
+ "bytes",
+ "futures-channel",
+ "futures-core",
+ "futures-util",
+ "http 1.1.0",
+ "http-body 1.0.0",
+ "http-body-util",
+ "hyper 1.2.0",
+ "hyper-rustls 0.26.0",
+ "hyper-util",
+ "ipnet",
+ "js-sys",
+ "log",
+ "mime",
+ "once_cell",
+ "percent-encoding",
+ "pin-project-lite",
+ "rustls 0.22.4",
+ "rustls-pemfile 2.1.1",
+ "rustls-pki-types",
+ "serde",
+ "serde_json",
+ "serde_urlencoded",
+ "sync_wrapper",
+ "tokio",
+ "tokio-rustls 0.25.0",
+ "tokio-util",
+ "tower-service",
+ "url",
+ "wasm-bindgen",
+ "wasm-bindgen-futures",
+ "wasm-streams 0.4.0",
+ "web-sys",
+ "webpki-roots 0.26.1",
+ "winreg 0.52.0",
 ]

 [[package]]
 name = "reqwest-middleware"
-version = "0.2.2"
+version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4531c89d50effe1fac90d095c8b133c20c5c714204feee0bfc3fd158e784209d"
+checksum = "0209efb52486ad88136190094ee214759ef7507068b27992256ed6610eb71a01"
 dependencies = [
 "anyhow",
 "async-trait",
- "http 0.2.9",
- "reqwest",
+ "http 1.1.0",
+ "reqwest 0.12.4",
 "serde",
- "task-local-extensions",
 "thiserror",
+ "tower-service",
 ]

 [[package]]
 name = "reqwest-retry"
-version = "0.2.2"
+version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "48d0fd6ef4c6d23790399fe15efc8d12cd9f3d4133958f9bd7801ee5cbaec6c4"
+checksum = "40f342894422862af74c50e1e9601cf0931accc9c6981e5eb413c46603b616b5"
 dependencies = [
 "anyhow",
 "async-trait",
 "chrono",
 "futures",
 "getrandom 0.2.11",
- "http 0.2.9",
- "hyper 0.14.26",
+ "http 1.1.0",
+ "hyper 1.2.0",
 "parking_lot 0.11.2",
- "reqwest",
+ "reqwest 0.12.4",
 "reqwest-middleware",
 "retry-policies",
- "task-local-extensions",
 "tokio",
 "tracing",
 "wasm-timer",
@@ -4773,27 +4869,27 @@ dependencies = [

 [[package]]
 name = "reqwest-tracing"
-version = "0.4.7"
+version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5a0152176687dd5cfe7f507ac1cb1a491c679cfe483afd133a7db7aaea818bb3"
+checksum = "b253954a1979e02eabccd7e9c3d61d8f86576108baa160775e7f160bb4e800a3"
 dependencies = [
 "anyhow",
 "async-trait",
 "getrandom 0.2.11",
- "matchit",
+ "http 1.1.0",
+ "matchit 0.8.2",
 "opentelemetry",
- "reqwest",
+ "reqwest 0.12.4",
 "reqwest-middleware",
- "task-local-extensions",
 "tracing",
 "tracing-opentelemetry",
 ]

 [[package]]
 name = "retry-policies"
-version = "0.1.2"
+version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e09bbcb5003282bcb688f0bae741b278e9c7e8f378f561522c9806c58e075d9b"
+checksum = "493b4243e32d6eedd29f9a398896e35c6943a123b55eec97dcaee98310d25810"
 dependencies = [
 "anyhow",
 "chrono",
@@ -5119,7 +5215,7 @@ dependencies = [
 "postgres_ffi",
 "rand 0.8.5",
 "remote_storage",
- "reqwest",
+ "reqwest 0.12.4",
 "serde",
 "serde_json",
 "serde_with",
@@ -5170,7 +5266,7 @@ dependencies = [
 "rand 0.8.5",
 "regex",
 "remote_storage",
- "reqwest",
+ "reqwest 0.12.4",
 "safekeeper_api",
 "scopeguard",
 "sd-notify",
@@ -5300,12 +5396,12 @@ checksum = "bebd363326d05ec3e2f532ab7660680f3b02130d780c299bca73469d521bc0ed"

 [[package]]
 name = "sentry"
-version = "0.31.6"
+version = "0.32.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2e95efd0cefa32028cdb9766c96de71d96671072f9fb494dc9fb84c0ef93e52b"
+checksum = "00421ed8fa0c995f07cde48ba6c89e80f2b312f74ff637326f392fbfd23abe02"
 dependencies = [
 "httpdate",
- "reqwest",
+ "reqwest 0.12.4",
 "rustls 0.21.11",
 "sentry-backtrace",
 "sentry-contexts",
@@ -5319,9 +5415,9 @@ dependencies = [

 [[package]]
 name = "sentry-backtrace"
-version = "0.31.6"
+version = "0.32.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6ac2bac6f310c4c4c4bb094d1541d32ae497f8c5c23405e85492cefdfe0971a9"
+checksum = "a79194074f34b0cbe5dd33896e5928bbc6ab63a889bd9df2264af5acb186921e"
 dependencies = [
 "backtrace",
 "once_cell",
@@ -5331,11 +5427,11 @@ dependencies = [

 [[package]]
 name = "sentry-contexts"
-version = "0.31.6"
+version = "0.32.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6c3e17295cecdbacf66c5bd38d6e1147e09e1e9d824d2d5341f76638eda02a3a"
+checksum = "eba8870c5dba2bfd9db25c75574a11429f6b95957b0a78ac02e2970dd7a5249a"
 dependencies = [
- "hostname",
+ "hostname 0.4.0",
 "libc",
 "os_info",
 "rustc_version",
@@ -5345,9 +5441,9 @@ dependencies = [

 [[package]]
 name = "sentry-core"
-version = "0.31.6"
+version = "0.32.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8339474f587f36cb110fa1ed1b64229eea6d47b0b886375579297b7e47aeb055"
+checksum = "46a75011ea1c0d5c46e9e57df03ce81f5c7f0a9e199086334a1f9c0a541e0826"
 dependencies = [
 "once_cell",
 "rand 0.8.5",
@@ -5358,9 +5454,9 @@ dependencies = [

 [[package]]
 name = "sentry-panic"
-version = "0.31.6"
+version = "0.32.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "875b69f506da75bd664029eafb05f8934297d2990192896d17325f066bd665b7"
+checksum = "2eaa3ecfa3c8750c78dcfd4637cfa2598b95b52897ed184b4dc77fcf7d95060d"
 dependencies = [
 "sentry-backtrace",
 "sentry-core",
@@ -5368,9 +5464,9 @@ dependencies = [

 [[package]]
 name = "sentry-tracing"
-version = "0.31.6"
+version = "0.32.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "89feead9bdd116f8035e89567651340fc382db29240b6c55ef412078b08d1aa3"
+checksum = "f715932bf369a61b7256687c6f0554141b7ce097287e30e3f7ed6e9de82498fe"
 dependencies = [
 "sentry-backtrace",
 "sentry-core",
@@ -5380,13 +5476,13 @@ dependencies = [

 [[package]]
 name = "sentry-types"
-version = "0.31.6"
+version = "0.32.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "99dc599bd6646884fc403d593cdcb9816dd67c50cff3271c01ff123617908dcd"
+checksum = "4519c900ce734f7a0eb7aba0869dfb225a7af8820634a7dd51449e3b093cfb7c"
 dependencies = [
 "debugid",
- "getrandom 0.2.11",
 "hex",
+ "rand 0.8.5",
 "serde",
 "serde_json",
 "thiserror",
@@ -5778,10 +5874,12 @@ dependencies = [
 "pageserver_client",
 "postgres_connection",
 "r2d2",
- "reqwest",
+ "reqwest 0.12.4",
 "routerify",
 "serde",
 "serde_json",
+ "strum",
+ "strum_macros",
 "thiserror",
 "tokio",
 "tokio-util",
@@ -5800,7 +5898,7 @@ dependencies = [
 "hyper 0.14.26",
 "pageserver_api",
 "pageserver_client",
- "reqwest",
+ "reqwest 0.12.4",
 "serde",
 "serde_json",
 "thiserror",
@@ -5854,7 +5952,7 @@ checksum = "81cdd64d312baedb58e21336b31bc043b77e01cc99033ce76ef539f78e965ebc"
 [[package]]
 name = "svg_fmt"
 version = "0.4.2"
-source = "git+https://github.com/neondatabase/fork--nical--rust_debug?branch=neon#b9501105e746629004bc6d0473639320939dbe10"
+source = "git+https://github.com/neondatabase/fork--nical--rust_debug?branch=neon#c1820b28664b5df68de7f043fccf2ed5d67b6ae8"

 [[package]]
 name = "syn"
@@ -5883,6 +5981,9 @@ name = "sync_wrapper"
 version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2047c6ded9c721764247e62cd3b03c09ffc529b2ba5b10ec482ae507a4a70160"
+dependencies = [
+ "futures-core",
+]

 [[package]]
 name = "synstructure"
@@ -6435,10 +6536,11 @@ dependencies = [

 [[package]]
 name = "tracing"
-version = "0.1.40"
+version = "0.1.37"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c3523ab5a71916ccf420eebdf5521fcef02141234bbc0b8a49f2fdc4544364ef"
+checksum = "8ce8c33a8d48bd45d624a6e523445fd21ec13d3653cd51f681abf67418f54eb8"
 dependencies = [
+ "cfg-if",
 "log",
 "pin-project-lite",
 "tracing-attributes",
@@ -6458,9 +6560,9 @@ dependencies = [

 [[package]]
 name = "tracing-attributes"
-version = "0.1.27"
+version = "0.1.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "34704c8d6ebcbc939824180af020566b01a7c01f80641264eba0999f6c2b6be7"
+checksum = "0f57e3ca2a01450b1a921183a9c9cbfda207fd822cef4ccb00a65402cbba7a74"
 dependencies = [
 "proc-macro2",
 "quote",
@@ -6469,9 +6571,9 @@ dependencies = [

 [[package]]
 name = "tracing-core"
-version = "0.1.32"
+version = "0.1.31"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c06d3da6113f116aaee68e4d601191614c9053067f9ab7f6edbcb161237daa54"
+checksum = "0955b8137a1df6f1a2e9a37d8a6656291ff0297c1a97c24e0d8425fe2312f79a"
 dependencies = [
 "once_cell",
 "valuable",
@@ -6500,12 +6602,14 @@ dependencies = [

 [[package]]
 name = "tracing-opentelemetry"
-version = "0.20.0"
+version = "0.21.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fc09e402904a5261e42cf27aea09ccb7d5318c6717a9eec3d8e2e65c56b18f19"
+checksum = "75327c6b667828ddc28f5e3f169036cb793c3f588d83bf0f262a7f062ffed3c8"
 dependencies = [
 "once_cell",
 "opentelemetry",
+ "opentelemetry_sdk",
+ "smallvec",
 "tracing",
 "tracing-core",
 "tracing-log",
@@ -6551,7 +6655,7 @@ dependencies = [
 "opentelemetry",
 "opentelemetry-otlp",
 "opentelemetry-semantic-conventions",
- "reqwest",
+ "reqwest 0.12.4",
 "tokio",
 "tracing",
 "tracing-opentelemetry",
@@ -6637,15 +6741,6 @@ dependencies = [
 "libc",
 ]

-[[package]]
-name = "unicase"
-version = "2.6.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "50f37be617794602aabbeee0be4f259dc1778fabe05e2d67ee8f79326d5cb4f6"
-dependencies = [
- "version_check",
-]
-
 [[package]]
 name = "unicode-bidi"
 version = "0.3.13"
@@ -7004,6 +7099,19 @@ dependencies = [
 "web-sys",
 ]

+[[package]]
+name = "wasm-streams"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b65dc4c90b63b118468cf747d8bf3566c1913ef60be765b5730ead9e0a3ba129"
+dependencies = [
+ "futures-util",
+ "js-sys",
+ "wasm-bindgen",
+ "wasm-bindgen-futures",
+ "web-sys",
+]
+
 [[package]]
 name = "wasm-timer"
 version = "0.2.5"
@@ -7044,6 +7152,15 @@ version = "0.25.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "14247bb57be4f377dfb94c72830b8ce8fc6beac03cf4bf7b9732eadd414123fc"

+[[package]]
+name = "webpki-roots"
+version = "0.26.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b3de34ae270483955a94f4b21bdaaeb83d508bb84a01435f393818edb0012009"
+dependencies = [
+ "rustls-pki-types",
+]
+
 [[package]]
 name = "which"
 version = "4.4.0"
@@ -7095,6 +7212,25 @@ dependencies = [
 "windows-targets 0.48.0",
 ]

+[[package]]
+name = "windows"
+version = "0.52.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e48a53791691ab099e5e2ad123536d0fff50652600abaf43bbf952894110d0be"
+dependencies = [
+ "windows-core",
+ "windows-targets 0.52.4",
+]
+
+[[package]]
+name = "windows-core"
+version = "0.52.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "33ab640c8d7e35bf8ba19b884ba838ceb4fba93a4e8c65a9059d08afcfc683d9"
+dependencies = [
+ "windows-targets 0.52.4",
+]
+
 [[package]]
 name = "windows-sys"
 version = "0.42.0"
@@ -7327,6 +7463,16 @@ dependencies = [
 "windows-sys 0.48.0",
 ]

+[[package]]
+name = "winreg"
+version = "0.52.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a277a57398d4bfa075df44f501a17cfdf8542d224f0d36095a2adc7aee4ef0a5"
+dependencies = [
+ "cfg-if",
+ "windows-sys 0.48.0",
+]
+
 [[package]]
 name = "workspace_hack"
 version = "0.1.0"
@@ -7376,7 +7522,8 @@ dependencies = [
 "regex",
 "regex-automata 0.4.3",
 "regex-syntax 0.8.2",
- "reqwest",
+ "reqwest 0.11.19",
+ "reqwest 0.12.4",
 "rustls 0.21.11",
 "scopeguard",
 "serde",
@@ -7386,6 +7533,7 @@ dependencies = [
 "subtle",
 "syn 1.0.109",
 "syn 2.0.52",
+ "sync_wrapper",
 "time",
 "time-macros",
 "tokio",
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -52,14 +52,14 @@ azure_storage_blobs = "0.19"
 flate2 = "1.0.26"
 async-stream = "0.3"
 async-trait = "0.1"
-aws-config = { version = "1.1.4", default-features = false, features=["rustls"] }
-aws-sdk-s3 = "1.14"
+aws-config = { version = "1.3", default-features = false, features=["rustls"] }
+aws-sdk-s3 = "1.26"
 aws-sdk-iam = "1.15.0"
-aws-smithy-async = { version = "1.1.4", default-features = false, features=["rt-tokio"] }
-aws-smithy-types = "1.1.4"
-aws-credential-types = "1.1.4"
-aws-sigv4 = { version = "1.2.0", features = ["sign-http"] }
-aws-types = "1.1.7"
+aws-smithy-async = { version = "1.2.1", default-features = false, features=["rt-tokio"] }
+aws-smithy-types = "1.1.9"
+aws-credential-types = "1.2.0"
+aws-sigv4 = { version = "1.2.1", features = ["sign-http"] }
+aws-types = "1.2.0"
 axum = { version = "0.6.20", features = ["ws"] }
 base64 = "0.13.0"
 bincode = "1.3"
@@ -99,6 +99,7 @@ humantime = "2.1"
 humantime-serde = "1.1.1"
 hyper = "0.14"
 hyper-tungstenite = "0.13.0"
+indexmap = "2"
 inotify = "0.10.2"
 ipnet = "2.9.0"
 itertools = "0.10"
@@ -130,10 +131,10 @@ prost = "0.11"
 rand = "0.8"
 redis = { version = "0.25.2", features = ["tokio-rustls-comp", "keep-alive"] }
 regex = "1.10.2"
-reqwest = { version = "0.11", default-features = false, features = ["rustls-tls"] }
-reqwest-tracing = { version = "0.4.7", features = ["opentelemetry_0_20"] }
-reqwest-middleware = "0.2.0"
-reqwest-retry = "0.2.2"
+reqwest = { version = "0.12", default-features = false, features = ["rustls-tls"] }
+reqwest-tracing = { version = "0.5", features = ["opentelemetry_0_20"] }
+reqwest-middleware = "0.3.0"
+reqwest-retry = "0.5"
 routerify = "3"
 rpds = "0.13"
 rustc-hash = "1.1.0"
@@ -143,7 +144,7 @@ rustls-split = "0.3"
 scopeguard = "1.1"
 sysinfo = "0.29.2"
 sd-notify = "0.4.1"
-sentry = { version = "0.31", default-features = false, features = ["backtrace", "contexts", "panic", "rustls", "reqwest" ] }
+sentry = { version = "0.32", default-features = false, features = ["backtrace", "contexts", "panic", "rustls", "reqwest" ] }
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1"
 serde_path_to_error = "0.1"
@@ -177,9 +178,10 @@ tokio-util = { version = "0.7.10", features = ["io", "rt"] }
 toml = "0.7"
 toml_edit = "0.19"
 tonic = {version = "0.9", features = ["tls", "tls-roots"]}
+tower-service = "0.3.2"
 tracing = "0.1"
 tracing-error = "0.2.0"
-tracing-opentelemetry = "0.20.0"
+tracing-opentelemetry = "0.21.0"
 tracing-subscriber = { version = "0.3", default_features = false, features = ["smallvec", "fmt", "tracing-log", "std", "env-filter", "json", "ansi"] }
 twox-hash = { version = "1.6.3", default-features = false }
 url = "2.2"
--- a/Dockerfile.build-tools
+++ b/Dockerfile.build-tools
@@ -65,7 +65,7 @@ RUN curl -sL "https://github.com/peak/s5cmd/releases/download/v${S5CMD_VERSION}/
    && mv s5cmd /usr/local/bin/s5cmd

 # LLVM
-ENV LLVM_VERSION=17
+ENV LLVM_VERSION=18
 RUN curl -fsSL 'https://apt.llvm.org/llvm-snapshot.gpg.key' | apt-key add - \
    && echo "deb http://apt.llvm.org/bullseye/ llvm-toolchain-bullseye-${LLVM_VERSION} main" > /etc/apt/sources.list.d/llvm.stable.list \
    && apt update \
@@ -141,7 +141,7 @@ WORKDIR /home/nonroot

 # Rust
 # Please keep the version of llvm (installed above) in sync with rust llvm (`rustc --version --verbose | grep LLVM`)
-ENV RUSTC_VERSION=1.77.0
+ENV RUSTC_VERSION=1.78.0
 ENV RUSTUP_HOME="/home/nonroot/.rustup"
 ENV PATH="/home/nonroot/.cargo/bin:${PATH}"
 RUN curl -sSO https://static.rust-lang.org/rustup/dist/$(uname -m)-unknown-linux-gnu/rustup-init && whoami && \
--- a/11
+++ b/11
@@ -81,11 +81,14 @@ $(POSTGRES_INSTALL_DIR)/build/%/config.status:
 		echo "'git submodule update --init --recursive --depth 2 --progress .' in project root.\n"; \
 		exit 1; }
 	mkdir -p $(POSTGRES_INSTALL_DIR)/build/$*
-	(cd $(POSTGRES_INSTALL_DIR)/build/$* && \
-	env PATH="$(EXTRA_PATH_OVERRIDES):$$PATH" $(ROOT_PROJECT_DIR)/vendor/postgres-$*/configure \
+
+	VERSION=$*; \
+	EXTRA_VERSION=$$(cd $(ROOT_PROJECT_DIR)/vendor/postgres-$$VERSION && git rev-parse HEAD); \
+	(cd $(POSTGRES_INSTALL_DIR)/build/$$VERSION && \
+	env PATH="$(EXTRA_PATH_OVERRIDES):$$PATH" $(ROOT_PROJECT_DIR)/vendor/postgres-$$VERSION/configure \
 		CFLAGS='$(PG_CFLAGS)' \
-		$(PG_CONFIGURE_OPTS) \
-		--prefix=$(abspath $(POSTGRES_INSTALL_DIR))/$* > configure.log)
+		$(PG_CONFIGURE_OPTS) --with-extra-version=" ($$EXTRA_VERSION)" \
+		--prefix=$(abspath $(POSTGRES_INSTALL_DIR))/$$VERSION > configure.log)

 # nicer alias to run 'configure'
 # Note: I've been unable to use templates for this part of our configuration.
--- a/compute_tools/src/bin/compute_ctl.rs
+++ b/compute_tools/src/bin/compute_ctl.rs
@@ -47,10 +47,11 @@ use chrono::Utc;
 use clap::Arg;
 use signal_hook::consts::{SIGQUIT, SIGTERM};
 use signal_hook::{consts::SIGINT, iterator::Signals};
-use tracing::{error, info};
+use tracing::{error, info, warn};
 use url::Url;

 use compute_api::responses::ComputeStatus;
+use compute_api::spec::ComputeSpec;

 use compute_tools::compute::{
    forward_termination_signal, ComputeNode, ComputeState, ParsedSpec, PG_PID,
@@ -62,12 +63,41 @@ use compute_tools::logger::*;
 use compute_tools::monitor::launch_monitor;
 use compute_tools::params::*;
 use compute_tools::spec::*;
+use compute_tools::swap::resize_swap;

 // this is an arbitrary build tag. Fine as a default / for testing purposes
 // in-case of not-set environment var
 const BUILD_TAG_DEFAULT: &str = "latest";

 fn main() -> Result<()> {
+    let (build_tag, clap_args) = init()?;
+
+    let (pg_handle, start_pg_result) = {
+        // Enter startup tracing context
+        let _startup_context_guard = startup_context_from_env();
+
+        let cli_args = process_cli(&clap_args)?;
+
+        let cli_spec = try_spec_from_cli(&clap_args, &cli_args)?;
+
+        let wait_spec_result = wait_spec(build_tag, cli_args, cli_spec)?;
+
+        start_postgres(&clap_args, wait_spec_result)?
+
+        // Startup is finished, exit the startup tracing span
+    };
+
+    // PostgreSQL is now running, if startup was successful. Wait until it exits.
+    let wait_pg_result = wait_postgres(pg_handle)?;
+
+    let delay_exit = cleanup_after_postgres_exit(start_pg_result)?;
+
+    maybe_delay_exit(delay_exit);
+
+    deinit_and_exit(wait_pg_result);
+}
+
+fn init() -> Result<(String, clap::ArgMatches)> {
    init_tracing_and_logging(DEFAULT_LOG_LEVEL)?;

    let mut signals = Signals::new([SIGINT, SIGTERM, SIGQUIT])?;
@@ -82,9 +112,15 @@ fn main() -> Result<()> {
        .to_string();
    info!("build_tag: {build_tag}");

-    let matches = cli().get_matches();
-    let pgbin_default = String::from("postgres");
-    let pgbin = matches.get_one::<String>("pgbin").unwrap_or(&pgbin_default);
+    Ok((build_tag, cli().get_matches()))
+}
+
+fn process_cli(matches: &clap::ArgMatches) -> Result<ProcessCliResult> {
+    let pgbin_default = "postgres";
+    let pgbin = matches
+        .get_one::<String>("pgbin")
+        .map(|s| s.as_str())
+        .unwrap_or(pgbin_default);

    let ext_remote_storage = matches
        .get_one::<String>("remote-ext-config")
@@ -110,7 +146,32 @@ fn main() -> Result<()> {
        .expect("Postgres connection string is required");
    let spec_json = matches.get_one::<String>("spec");
    let spec_path = matches.get_one::<String>("spec-path");
+    let resize_swap_on_bind = matches.get_flag("resize-swap-on-bind");

+    Ok(ProcessCliResult {
+        connstr,
+        pgdata,
+        pgbin,
+        ext_remote_storage,
+        http_port,
+        spec_json,
+        spec_path,
+        resize_swap_on_bind,
+    })
+}
+
+struct ProcessCliResult<'clap> {
+    connstr: &'clap str,
+    pgdata: &'clap str,
+    pgbin: &'clap str,
+    ext_remote_storage: Option<&'clap str>,
+    http_port: u16,
+    spec_json: Option<&'clap String>,
+    spec_path: Option<&'clap String>,
+    resize_swap_on_bind: bool,
+}
+
+fn startup_context_from_env() -> Option<opentelemetry::ContextGuard> {
    // Extract OpenTelemetry context for the startup actions from the
    // TRACEPARENT and TRACESTATE env variables, and attach it to the current
    // tracing context.
@@ -147,7 +208,7 @@ fn main() -> Result<()> {
    if let Ok(val) = std::env::var("TRACESTATE") {
        startup_tracing_carrier.insert("tracestate".to_string(), val);
    }
-    let startup_context_guard = if !startup_tracing_carrier.is_empty() {
+    if !startup_tracing_carrier.is_empty() {
        use opentelemetry::propagation::TextMapPropagator;
        use opentelemetry::sdk::propagation::TraceContextPropagator;
        let guard = TraceContextPropagator::new()
@@ -157,8 +218,17 @@ fn main() -> Result<()> {
        Some(guard)
    } else {
        None
-    };
+    }
+}

+fn try_spec_from_cli(
+    matches: &clap::ArgMatches,
+    ProcessCliResult {
+        spec_json,
+        spec_path,
+        ..
+    }: &ProcessCliResult,
+) -> Result<CliSpecParams> {
    let compute_id = matches.get_one::<String>("compute-id");
    let control_plane_uri = matches.get_one::<String>("control-plane-uri");

@@ -199,6 +269,34 @@ fn main() -> Result<()> {
        }
    };

+    Ok(CliSpecParams {
+        spec,
+        live_config_allowed,
+    })
+}
+
+struct CliSpecParams {
+    /// If a spec was provided via CLI or file, the [`ComputeSpec`]
+    spec: Option<ComputeSpec>,
+    live_config_allowed: bool,
+}
+
+fn wait_spec(
+    build_tag: String,
+    ProcessCliResult {
+        connstr,
+        pgdata,
+        pgbin,
+        ext_remote_storage,
+        resize_swap_on_bind,
+        http_port,
+        ..
+    }: ProcessCliResult,
+    CliSpecParams {
+        spec,
+        live_config_allowed,
+    }: CliSpecParams,
+) -> Result<WaitSpecResult> {
    let mut new_state = ComputeState::new();
    let spec_set;

@@ -226,19 +324,17 @@ fn main() -> Result<()> {

    // If this is a pooled VM, prewarm before starting HTTP server and becoming
    // available for binding. Prewarming helps Postgres start quicker later,
-    // because QEMU will already have it's memory allocated from the host, and
+    // because QEMU will already have its memory allocated from the host, and
    // the necessary binaries will already be cached.
    if !spec_set {
        compute.prewarm_postgres()?;
    }

-    // Launch http service first, so we were able to serve control-plane
-    // requests, while configuration is still in progress.
+    // Launch http service first, so that we can serve control-plane requests
+    // while configuration is still in progress.
    let _http_handle =
        launch_http_server(http_port, &compute).expect("cannot launch http endpoint thread");

-    let extension_server_port: u16 = http_port;
-
    if !spec_set {
        // No spec provided, hang waiting for it.
        info!("no compute spec provided, waiting");
@@ -253,21 +349,45 @@ fn main() -> Result<()> {
                break;
            }
        }
+
+        // Record for how long we slept waiting for the spec.
+        let now = Utc::now();
+        state.metrics.wait_for_spec_ms = now
+            .signed_duration_since(state.start_time)
+            .to_std()
+            .unwrap()
+            .as_millis() as u64;
+
+        // Reset start time, so that the total startup time that is calculated later will
+        // not include the time that we waited for the spec.
+        state.start_time = now;
    }

+    Ok(WaitSpecResult {
+        compute,
+        http_port,
+        resize_swap_on_bind,
+    })
+}
+
+struct WaitSpecResult {
+    compute: Arc<ComputeNode>,
+    // passed through from ProcessCliResult
+    http_port: u16,
+    resize_swap_on_bind: bool,
+}
+
+fn start_postgres(
+    // need to allow unused because `matches` is only used if target_os = "linux"
+    #[allow(unused_variables)] matches: &clap::ArgMatches,
+    WaitSpecResult {
+        compute,
+        http_port,
+        resize_swap_on_bind,
+    }: WaitSpecResult,
+) -> Result<(Option<PostgresHandle>, StartPostgresResult)> {
    // We got all we need, update the state.
    let mut state = compute.state.lock().unwrap();
-
-    // Record for how long we slept waiting for the spec.
-    state.metrics.wait_for_spec_ms = Utc::now()
-        .signed_duration_since(state.start_time)
-        .to_std()
-        .unwrap()
-        .as_millis() as u64;
-    // Reset start time to the actual start of the configuration, so that
-    // total startup time was properly measured at the end.
-    state.start_time = Utc::now();
-
    state.status = ComputeStatus::Init;
    compute.state_changed.notify_all();

@@ -275,33 +395,72 @@ fn main() -> Result<()> {
        "running compute with features: {:?}",
        state.pspec.as_ref().unwrap().spec.features
    );
+    // before we release the mutex, fetch the swap size (if any) for later.
+    let swap_size_bytes = state.pspec.as_ref().unwrap().spec.swap_size_bytes;
    drop(state);

    // Launch remaining service threads
    let _monitor_handle = launch_monitor(&compute);
    let _configurator_handle = launch_configurator(&compute);

-    // Start Postgres
+    let mut prestartup_failed = false;
    let mut delay_exit = false;
-    let mut exit_code = None;
-    let pg = match compute.start_compute(extension_server_port) {
-        Ok(pg) => Some(pg),
-        Err(err) => {
-            error!("could not start the compute node: {:#}", err);
-            let mut state = compute.state.lock().unwrap();
-            state.error = Some(format!("{:?}", err));
-            state.status = ComputeStatus::Failed;
-            // Notify others that Postgres failed to start. In case of configuring the
-            // empty compute, it's likely that API handler is still waiting for compute
-            // state change. With this we will notify it that compute is in Failed state,
-            // so control plane will know about it earlier and record proper error instead
-            // of timeout.
-            compute.state_changed.notify_all();
-            drop(state); // unlock
-            delay_exit = true;
-            None
+
+    // Resize swap to the desired size if the compute spec says so
+    if let (Some(size_bytes), true) = (swap_size_bytes, resize_swap_on_bind) {
+        // To avoid 'swapoff' hitting postgres startup, we need to run resize-swap to completion
+        // *before* starting postgres.
+        //
+        // In theory, we could do this asynchronously if SkipSwapon was enabled for VMs, but this
+        // carries a risk of introducing hard-to-debug issues - e.g. if postgres sometimes gets
+        // OOM-killed during startup because swap wasn't available yet.
+        match resize_swap(size_bytes) {
+            Ok(()) => {
+                let size_gib = size_bytes as f32 / (1 << 20) as f32; // just for more coherent display.
+                info!(%size_bytes, %size_gib, "resized swap");
+            }
+            Err(err) => {
+                let err = err.context("failed to resize swap");
+                error!("{err:#}");
+
+                // Mark compute startup as failed; don't try to start postgres, and report this
+                // error to the control plane when it next asks.
+                prestartup_failed = true;
+                let mut state = compute.state.lock().unwrap();
+                state.error = Some(format!("{err:?}"));
+                state.status = ComputeStatus::Failed;
+                compute.state_changed.notify_all();
+                delay_exit = true;
+            }
        }
-    };
+    }
+
+    let extension_server_port: u16 = http_port;
+
+    // Start Postgres
+    let mut pg = None;
+    if !prestartup_failed {
+        pg = match compute.start_compute(extension_server_port) {
+            Ok(pg) => Some(pg),
+            Err(err) => {
+                error!("could not start the compute node: {:#}", err);
+                let mut state = compute.state.lock().unwrap();
+                state.error = Some(format!("{:?}", err));
+                state.status = ComputeStatus::Failed;
+                // Notify others that Postgres failed to start. In case of configuring the
+                // empty compute, it's likely that API handler is still waiting for compute
+                // state change. With this we will notify it that compute is in Failed state,
+                // so control plane will know about it earlier and record proper error instead
+                // of timeout.
+                compute.state_changed.notify_all();
+                drop(state); // unlock
+                delay_exit = true;
+                None
+            }
+        };
+    } else {
+        warn!("skipping postgres startup because pre-startup step failed");
+    }

    // Start the vm-monitor if directed to. The vm-monitor only runs on linux
    // because it requires cgroups.
@@ -334,7 +493,7 @@ fn main() -> Result<()> {
            // This token is used internally by the monitor to clean up all threads
            let token = CancellationToken::new();

-            let vm_monitor = &rt.as_ref().map(|rt| {
+            let vm_monitor = rt.as_ref().map(|rt| {
                rt.spawn(vm_monitor::start(
                    Box::leak(Box::new(vm_monitor::Args {
                        cgroup: cgroup.cloned(),
@@ -347,12 +506,41 @@ fn main() -> Result<()> {
        }
    }

+    Ok((
+        pg,
+        StartPostgresResult {
+            delay_exit,
+            compute,
+            #[cfg(target_os = "linux")]
+            rt,
+            #[cfg(target_os = "linux")]
+            token,
+            #[cfg(target_os = "linux")]
+            vm_monitor,
+        },
+    ))
+}
+
+type PostgresHandle = (std::process::Child, std::thread::JoinHandle<()>);
+
+struct StartPostgresResult {
+    delay_exit: bool,
+    // passed through from WaitSpecResult
+    compute: Arc<ComputeNode>,
+
+    #[cfg(target_os = "linux")]
+    rt: Option<tokio::runtime::Runtime>,
+    #[cfg(target_os = "linux")]
+    token: tokio_util::sync::CancellationToken,
+    #[cfg(target_os = "linux")]
+    vm_monitor: Option<tokio::task::JoinHandle<Result<()>>>,
+}
+
+fn wait_postgres(pg: Option<PostgresHandle>) -> Result<WaitPostgresResult> {
    // Wait for the child Postgres process forever. In this state Ctrl+C will
    // propagate to Postgres and it will be shut down as well.
+    let mut exit_code = None;
    if let Some((mut pg, logs_handle)) = pg {
-        // Startup is finished, exit the startup tracing span
-        drop(startup_context_guard);
-
        let ecode = pg
            .wait()
            .expect("failed to start waiting on Postgres process");
@@ -367,6 +555,25 @@ fn main() -> Result<()> {
        exit_code = ecode.code()
    }

+    Ok(WaitPostgresResult { exit_code })
+}
+
+struct WaitPostgresResult {
+    exit_code: Option<i32>,
+}
+
+fn cleanup_after_postgres_exit(
+    StartPostgresResult {
+        mut delay_exit,
+        compute,
+        #[cfg(target_os = "linux")]
+        vm_monitor,
+        #[cfg(target_os = "linux")]
+        token,
+        #[cfg(target_os = "linux")]
+        rt,
+    }: StartPostgresResult,
+) -> Result<bool> {
    // Terminate the vm_monitor so it releases the file watcher on
    // /sys/fs/cgroup/neon-postgres.
    // Note: the vm-monitor only runs on linux because it requires cgroups.
@@ -408,13 +615,19 @@ fn main() -> Result<()> {
        error!("error while checking for core dumps: {err:?}");
    }

+    Ok(delay_exit)
+}
+
+fn maybe_delay_exit(delay_exit: bool) {
    // If launch failed, keep serving HTTP requests for a while, so the cloud
    // control plane can get the actual error.
    if delay_exit {
        info!("giving control plane 30s to collect the error before shutdown");
        thread::sleep(Duration::from_secs(30));
    }
+}

+fn deinit_and_exit(WaitPostgresResult { exit_code }: WaitPostgresResult) -> ! {
    // Shutdown trace pipeline gracefully, so that it has a chance to send any
    // pending traces before we exit. Shutting down OTEL tracing provider may
    // hang for quite some time, see, for example:
@@ -526,6 +739,11 @@ fn cli() -> clap::Command {
                )
                .value_name("FILECACHE_CONNSTR"),
        )
+        .arg(
+            Arg::new("resize-swap-on-bind")
+                .long("resize-swap-on-bind")
+                .action(clap::ArgAction::SetTrue),
+        )
 }

 /// When compute_ctl is killed, send also termination signal to sync-safekeepers
--- a/compute_tools/src/lib.rs
+++ b/compute_tools/src/lib.rs
@@ -14,4 +14,5 @@ pub mod monitor;
 pub mod params;
 pub mod pg_helpers;
 pub mod spec;
+pub mod swap;
 pub mod sync_sk;
--- a/compute_tools/src/spec.rs
+++ b/compute_tools/src/spec.rs
@@ -490,7 +490,7 @@ pub fn handle_databases(spec: &ComputeSpec, client: &mut Client) -> Result<()> {
                "rename_db" => {
                    let new_name = op.new_name.as_ref().unwrap();

-                    if existing_dbs.get(&op.name).is_some() {
+                    if existing_dbs.contains_key(&op.name) {
                        let query: String = format!(
                            "ALTER DATABASE {} RENAME TO {}",
                            op.name.pg_quote(),
--- a/compute_tools/src/swap.rs
+++ b/compute_tools/src/swap.rs
@@ -0,0 +1,36 @@
+use anyhow::{anyhow, Context};
+use tracing::warn;
+
+pub const RESIZE_SWAP_BIN: &str = "/neonvm/bin/resize-swap";
+
+pub fn resize_swap(size_bytes: u64) -> anyhow::Result<()> {
+    // run `/neonvm/bin/resize-swap --once {size_bytes}`
+    //
+    // Passing '--once' causes resize-swap to delete itself after successful completion, which
+    // means that if compute_ctl restarts later, we won't end up calling 'swapoff' while
+    // postgres is running.
+    //
+    // NOTE: resize-swap is not very clever. If present, --once MUST be the first arg.
+    let child_result = std::process::Command::new("/usr/bin/sudo")
+        .arg(RESIZE_SWAP_BIN)
+        .arg("--once")
+        .arg(size_bytes.to_string())
+        .spawn();
+
+    if matches!(&child_result, Err(e) if e.kind() == std::io::ErrorKind::NotFound) {
+        warn!("ignoring \"not found\" error from resize-swap to avoid swapoff while compute is running");
+        return Ok(());
+    }
+
+    child_result
+        .context("spawn() failed")
+        .and_then(|mut child| child.wait().context("wait() failed"))
+        .and_then(|status| match status.success() {
+            true => Ok(()),
+            false => Err(anyhow!("process exited with {status}")),
+        })
+        // wrap any prior error with the overall context that we couldn't run the command
+        .with_context(|| {
+            format!("could not run `/usr/bin/sudo {RESIZE_SWAP_BIN} --once {size_bytes}`")
+        })
+}
--- a/control_plane/Cargo.toml
+++ b/control_plane/Cargo.toml
@@ -28,6 +28,7 @@ serde_with.workspace = true
 tar.workspace = true
 thiserror.workspace = true
 toml.workspace = true
+toml_edit.workspace = true
 tokio.workspace = true
 tokio-postgres.workspace = true
 tokio-util.workspace = true
--- a/control_plane/src/bin/neon_local.rs
+++ b/control_plane/src/bin/neon_local.rs
@@ -9,20 +9,23 @@ use anyhow::{anyhow, bail, Context, Result};
 use clap::{value_parser, Arg, ArgAction, ArgMatches, Command, ValueEnum};
 use compute_api::spec::ComputeMode;
 use control_plane::endpoint::ComputeControlPlane;
-use control_plane::local_env::{InitForceMode, LocalEnv};
-use control_plane::pageserver::{PageServerNode, PAGESERVER_REMOTE_STORAGE_DIR};
+use control_plane::local_env::{
+    InitForceMode, LocalEnv, NeonBroker, NeonLocalInitConf, NeonLocalInitPageserverConf,
+    SafekeeperConf,
+};
+use control_plane::pageserver::PageServerNode;
 use control_plane::safekeeper::SafekeeperNode;
 use control_plane::storage_controller::StorageController;
 use control_plane::{broker, local_env};
+use pageserver_api::config::{
+    DEFAULT_HTTP_LISTEN_PORT as DEFAULT_PAGESERVER_HTTP_PORT,
+    DEFAULT_PG_LISTEN_PORT as DEFAULT_PAGESERVER_PG_PORT,
+};
 use pageserver_api::controller_api::PlacementPolicy;
 use pageserver_api::models::{
    ShardParameters, TenantCreateRequest, TimelineCreateRequest, TimelineInfo,
 };
 use pageserver_api::shard::{ShardCount, ShardStripeSize, TenantShardId};
-use pageserver_api::{
-    DEFAULT_HTTP_LISTEN_PORT as DEFAULT_PAGESERVER_HTTP_PORT,
-    DEFAULT_PG_LISTEN_PORT as DEFAULT_PAGESERVER_PG_PORT,
-};
 use postgres_backend::AuthType;
 use postgres_connection::parse_host_port;
 use safekeeper_api::{
@@ -52,44 +55,6 @@ const DEFAULT_PG_VERSION: &str = "15";

 const DEFAULT_PAGESERVER_CONTROL_PLANE_API: &str = "http://127.0.0.1:1234/upcall/v1/";

-fn default_conf(num_pageservers: u16) -> String {
-    let mut template = format!(
-        r#"
-# Default built-in configuration, defined in main.rs
-control_plane_api = '{DEFAULT_PAGESERVER_CONTROL_PLANE_API}'
-
-[broker]
-listen_addr = '{DEFAULT_BROKER_ADDR}'
-
-[[safekeepers]]
-id = {DEFAULT_SAFEKEEPER_ID}
-pg_port = {DEFAULT_SAFEKEEPER_PG_PORT}
-http_port = {DEFAULT_SAFEKEEPER_HTTP_PORT}
-
-"#,
-    );
-
-    for i in 0..num_pageservers {
-        let pageserver_id = NodeId(DEFAULT_PAGESERVER_ID.0 + i as u64);
-        let pg_port = DEFAULT_PAGESERVER_PG_PORT + i;
-        let http_port = DEFAULT_PAGESERVER_HTTP_PORT + i;
-
-        template += &format!(
-            r#"
-[[pageservers]]
-id = {pageserver_id}
-listen_pg_addr = '127.0.0.1:{pg_port}'
-listen_http_addr = '127.0.0.1:{http_port}'
-pg_auth_type = '{trust_auth}'
-http_auth_type = '{trust_auth}'
-"#,
-            trust_auth = AuthType::Trust,
-        )
-    }
-
-    template
-}
-
 ///
 /// Timelines tree element used as a value in the HashMap.
 ///
@@ -133,7 +98,7 @@ fn main() -> Result<()> {
        let subcommand_result = match sub_name {
            "tenant" => rt.block_on(handle_tenant(sub_args, &mut env)),
            "timeline" => rt.block_on(handle_timeline(sub_args, &mut env)),
-            "start" => rt.block_on(handle_start_all(sub_args, &env)),
+            "start" => rt.block_on(handle_start_all(&env)),
            "stop" => rt.block_on(handle_stop_all(sub_args, &env)),
            "pageserver" => rt.block_on(handle_pageserver(sub_args, &env)),
            "storage_controller" => rt.block_on(handle_storage_controller(sub_args, &env)),
@@ -152,7 +117,7 @@ fn main() -> Result<()> {
    };

    match subcommand_result {
-        Ok(Some(updated_env)) => updated_env.persist_config(&updated_env.base_data_dir)?,
+        Ok(Some(updated_env)) => updated_env.persist_config()?,
        Ok(None) => (),
        Err(e) => {
            eprintln!("command failed: {e:?}");
@@ -341,48 +306,65 @@ fn parse_timeline_id(sub_match: &ArgMatches) -> anyhow::Result<Option<TimelineId
 }

 fn handle_init(init_match: &ArgMatches) -> anyhow::Result<LocalEnv> {
-    let num_pageservers = init_match
-        .get_one::<u16>("num-pageservers")
-        .expect("num-pageservers arg has a default");
-    // Create config file
-    let toml_file: String = if let Some(config_path) = init_match.get_one::<PathBuf>("config") {
+    let num_pageservers = init_match.get_one::<u16>("num-pageservers");
+
+    let force = init_match.get_one("force").expect("we set a default value");
+
+    // Create the in-memory `LocalEnv` that we'd normally load from disk in `load_config`.
+    let init_conf: NeonLocalInitConf = if let Some(config_path) =
+        init_match.get_one::<PathBuf>("config")
+    {
+        // User (likely the Python test suite) provided a description of the environment.
+        if num_pageservers.is_some() {
+            bail!("Cannot specify both --num-pageservers and --config, use key `pageservers` in the --config file instead");
+        }
        // load and parse the file
-        std::fs::read_to_string(config_path).with_context(|| {
+        let contents = std::fs::read_to_string(config_path).with_context(|| {
            format!(
                "Could not read configuration file '{}'",
                config_path.display()
            )
-        })?
+        })?;
+        toml_edit::de::from_str(&contents)?
    } else {
-        // Built-in default config
-        default_conf(*num_pageservers)
+        // User (likely interactive) did not provide a description of the environment, give them the default
+        NeonLocalInitConf {
+            control_plane_api: Some(Some(DEFAULT_PAGESERVER_CONTROL_PLANE_API.parse().unwrap())),
+            broker: NeonBroker {
+                listen_addr: DEFAULT_BROKER_ADDR.parse().unwrap(),
+            },
+            safekeepers: vec![SafekeeperConf {
+                id: DEFAULT_SAFEKEEPER_ID,
+                pg_port: DEFAULT_SAFEKEEPER_PG_PORT,
+                http_port: DEFAULT_SAFEKEEPER_HTTP_PORT,
+                ..Default::default()
+            }],
+            pageservers: (0..num_pageservers.copied().unwrap_or(1))
+                .map(|i| {
+                    let pageserver_id = NodeId(DEFAULT_PAGESERVER_ID.0 + i as u64);
+                    let pg_port = DEFAULT_PAGESERVER_PG_PORT + i;
+                    let http_port = DEFAULT_PAGESERVER_HTTP_PORT + i;
+                    NeonLocalInitPageserverConf {
+                        id: pageserver_id,
+                        listen_pg_addr: format!("127.0.0.1:{pg_port}"),
+                        listen_http_addr: format!("127.0.0.1:{http_port}"),
+                        pg_auth_type: AuthType::Trust,
+                        http_auth_type: AuthType::Trust,
+                        other: Default::default(),
+                    }
+                })
+                .collect(),
+            pg_distrib_dir: None,
+            neon_distrib_dir: None,
+            default_tenant_id: TenantId::from_array(std::array::from_fn(|_| 0)),
+            storage_controller: None,
+            control_plane_compute_hook_api: None,
+        }
    };

-    let pg_version = init_match
-        .get_one::<u32>("pg-version")
-        .copied()
-        .context("Failed to parse postgres version from the argument string")?;
-
-    let mut env =
-        LocalEnv::parse_config(&toml_file).context("Failed to create neon configuration")?;
-    let force = init_match.get_one("force").expect("we set a default value");
-    env.init(pg_version, force)
-        .context("Failed to initialize neon repository")?;
-
-    // Create remote storage location for default LocalFs remote storage
-    std::fs::create_dir_all(env.base_data_dir.join(PAGESERVER_REMOTE_STORAGE_DIR))?;
-
-    // Initialize pageserver, create initial tenant and timeline.
-    for ps_conf in &env.pageservers {
-        PageServerNode::from_env(&env, ps_conf)
-            .initialize(&pageserver_config_overrides(init_match))
-            .unwrap_or_else(|e| {
-                eprintln!("pageserver init failed: {e:?}");
-                exit(1);
-            });
-    }
-
-    Ok(env)
+    LocalEnv::init(init_conf, force)
+        .context("materialize initial neon_local environment on disk")?;
+    Ok(LocalEnv::load_config().expect("freshly written config should be loadable"))
 }

 /// The default pageserver is the one where CLI tenant/timeline operations are sent by default.
@@ -397,15 +379,6 @@ fn get_default_pageserver(env: &local_env::LocalEnv) -> PageServerNode {
    PageServerNode::from_env(env, ps_conf)
 }

-fn pageserver_config_overrides(init_match: &ArgMatches) -> Vec<&str> {
-    init_match
-        .get_many::<String>("pageserver-config-override")
-        .into_iter()
-        .flatten()
-        .map(String::as_str)
-        .collect()
-}
-
 async fn handle_tenant(
    tenant_match: &ArgMatches,
    env: &mut local_env::LocalEnv,
@@ -837,6 +810,8 @@ async fn handle_endpoint(ep_match: &ArgMatches, env: &local_env::LocalEnv) -> Re
                .copied()
                .unwrap_or(false);

+            let allow_multiple = sub_args.get_flag("allow-multiple");
+
            let mode = match (lsn, hot_standby) {
                (Some(lsn), false) => ComputeMode::Static(lsn),
                (None, true) => ComputeMode::Replica,
@@ -854,7 +829,9 @@ async fn handle_endpoint(ep_match: &ArgMatches, env: &local_env::LocalEnv) -> Re
                _ => {}
            }

-            cplane.check_conflicting_endpoints(mode, tenant_id, timeline_id)?;
+            if !allow_multiple {
+                cplane.check_conflicting_endpoints(mode, tenant_id, timeline_id)?;
+            }

            cplane.new_endpoint(
                &endpoint_id,
@@ -883,6 +860,8 @@ async fn handle_endpoint(ep_match: &ArgMatches, env: &local_env::LocalEnv) -> Re

            let remote_ext_config = sub_args.get_one::<String>("remote-ext-config");

+            let allow_multiple = sub_args.get_flag("allow-multiple");
+
            // If --safekeepers argument is given, use only the listed safekeeper nodes.
            let safekeepers =
                if let Some(safekeepers_str) = sub_args.get_one::<String>("safekeepers") {
@@ -908,11 +887,13 @@ async fn handle_endpoint(ep_match: &ArgMatches, env: &local_env::LocalEnv) -> Re
                .cloned()
                .unwrap_or_default();

-            cplane.check_conflicting_endpoints(
-                endpoint.mode,
-                endpoint.tenant_id,
-                endpoint.timeline_id,
-            )?;
+            if !allow_multiple {
+                cplane.check_conflicting_endpoints(
+                    endpoint.mode,
+                    endpoint.tenant_id,
+                    endpoint.timeline_id,
+                )?;
+            }

            let (pageservers, stripe_size) = if let Some(pageserver_id) = pageserver_id {
                let conf = env.get_pageserver_conf(pageserver_id).unwrap();
@@ -1068,10 +1049,7 @@ fn get_pageserver(env: &local_env::LocalEnv, args: &ArgMatches) -> Result<PageSe
 async fn handle_pageserver(sub_match: &ArgMatches, env: &local_env::LocalEnv) -> Result<()> {
    match sub_match.subcommand() {
        Some(("start", subcommand_args)) => {
-            if let Err(e) = get_pageserver(env, subcommand_args)?
-                .start(&pageserver_config_overrides(subcommand_args))
-                .await
-            {
+            if let Err(e) = get_pageserver(env, subcommand_args)?.start().await {
                eprintln!("pageserver start failed: {e}");
                exit(1);
            }
@@ -1097,10 +1075,7 @@ async fn handle_pageserver(sub_match: &ArgMatches, env: &local_env::LocalEnv) ->
                exit(1);
            }

-            if let Err(e) = pageserver
-                .start(&pageserver_config_overrides(subcommand_args))
-                .await
-            {
+            if let Err(e) = pageserver.start().await {
                eprintln!("pageserver start failed: {e}");
                exit(1);
            }
@@ -1227,7 +1202,7 @@ async fn handle_safekeeper(sub_match: &ArgMatches, env: &local_env::LocalEnv) ->
    Ok(())
 }

-async fn handle_start_all(sub_match: &ArgMatches, env: &local_env::LocalEnv) -> anyhow::Result<()> {
+async fn handle_start_all(env: &local_env::LocalEnv) -> anyhow::Result<()> {
    // Endpoints are not started automatically

    broker::start_broker_process(env).await?;
@@ -1244,10 +1219,7 @@ async fn handle_start_all(sub_match: &ArgMatches, env: &local_env::LocalEnv) ->

    for ps_conf in &env.pageservers {
        let pageserver = PageServerNode::from_env(env, ps_conf);
-        if let Err(e) = pageserver
-            .start(&pageserver_config_overrides(sub_match))
-            .await
-        {
+        if let Err(e) = pageserver.start().await {
            eprintln!("pageserver {} start failed: {:#}", ps_conf.id, e);
            try_stop_all(env, true).await;
            exit(1);
@@ -1388,13 +1360,6 @@ fn cli() -> Command {
        .required(false)
        .value_name("stop-mode");

-    let pageserver_config_args = Arg::new("pageserver-config-override")
-        .long("pageserver-config-override")
-        .num_args(1)
-        .action(ArgAction::Append)
-        .help("Additional pageserver's configuration options or overrides, refer to pageserver's 'config-override' CLI parameter docs for more")
-        .required(false);
-
    let remote_ext_config_args = Arg::new("remote-ext-config")
        .long("remote-ext-config")
        .num_args(1)
@@ -1428,9 +1393,7 @@ fn cli() -> Command {
    let num_pageservers_arg = Arg::new("num-pageservers")
        .value_parser(value_parser!(u16))
        .long("num-pageservers")
-        .help("How many pageservers to create (default 1)")
-        .required(false)
-        .default_value("1");
+        .help("How many pageservers to create (default 1)");

    let update_catalog = Arg::new("update-catalog")
        .value_parser(value_parser!(bool))
@@ -1444,20 +1407,25 @@ fn cli() -> Command {
        .help("If set, will create test user `user` and `neondb` database. Requires `update-catalog = true`")
        .required(false);

+    let allow_multiple = Arg::new("allow-multiple")
+        .help("Allow multiple primary endpoints running on the same branch. Shouldn't be used normally, but useful for tests.")
+        .long("allow-multiple")
+        .action(ArgAction::SetTrue)
+        .required(false);
+
    Command::new("Neon CLI")
        .arg_required_else_help(true)
        .version(GIT_VERSION)
        .subcommand(
            Command::new("init")
                .about("Initialize a new Neon repository, preparing configs for services to start with")
-                .arg(pageserver_config_args.clone())
                .arg(num_pageservers_arg.clone())
                .arg(
                    Arg::new("config")
                        .long("config")
                        .required(false)
                        .value_parser(value_parser!(PathBuf))
-                        .value_name("config"),
+                        .value_name("config")
                )
                .arg(pg_version_arg.clone())
                .arg(force_arg)
@@ -1539,7 +1507,6 @@ fn cli() -> Command {
                .subcommand(Command::new("status"))
                .subcommand(Command::new("start")
                    .about("Start local pageserver")
-                    .arg(pageserver_config_args.clone())
                )
                .subcommand(Command::new("stop")
                    .about("Stop local pageserver")
@@ -1547,7 +1514,6 @@ fn cli() -> Command {
                )
                .subcommand(Command::new("restart")
                    .about("Restart local pageserver")
-                    .arg(pageserver_config_args.clone())
                )
        )
        .subcommand(
@@ -1601,6 +1567,7 @@ fn cli() -> Command {
                    .arg(pg_version_arg.clone())
                    .arg(hot_standby_arg.clone())
                    .arg(update_catalog)
+                    .arg(allow_multiple.clone())
                )
                .subcommand(Command::new("start")
                    .about("Start postgres.\n If the endpoint doesn't exist yet, it is created.")
@@ -1609,6 +1576,7 @@ fn cli() -> Command {
                    .arg(safekeepers_arg)
                    .arg(remote_ext_config_args)
                    .arg(create_test_user)
+                    .arg(allow_multiple.clone())
                )
                .subcommand(Command::new("reconfigure")
                            .about("Reconfigure the endpoint")
@@ -1660,7 +1628,6 @@ fn cli() -> Command {
        .subcommand(
            Command::new("start")
                .about("Start page server and safekeepers")
-                .arg(pageserver_config_args)
        )
        .subcommand(
            Command::new("stop")
--- a/control_plane/src/endpoint.rs
+++ b/control_plane/src/endpoint.rs
@@ -554,6 +554,7 @@ impl Endpoint {
            format_version: 1.0,
            operation_uuid: None,
            features: self.features.clone(),
+            swap_size_bytes: None,
            cluster: Cluster {
                cluster_id: None, // project ID: not used
                name: None,       // project name: not used
--- a/control_plane/src/local_env.rs
+++ b/control_plane/src/local_env.rs
@@ -3,7 +3,7 @@
 //! Now it also provides init method which acts like a stub for proper installation
 //! script which will use local paths.

-use anyhow::{bail, ensure, Context};
+use anyhow::{bail, Context};

 use clap::ValueEnum;
 use postgres_backend::AuthType;
@@ -23,6 +23,8 @@ use utils::{
    id::{NodeId, TenantId, TenantTimelineId, TimelineId},
 };

+use crate::pageserver::PageServerNode;
+use crate::pageserver::PAGESERVER_REMOTE_STORAGE_DIR;
 use crate::safekeeper::SafekeeperNode;

 pub const DEFAULT_PG_VERSION: u32 = 15;
@@ -34,7 +36,7 @@ pub const DEFAULT_PG_VERSION: u32 = 15;
 // to 'neon_local init --config=<path>' option. See control_plane/simple.conf for
 // an example.
 //
-#[derive(Serialize, Deserialize, PartialEq, Eq, Clone, Debug)]
+#[derive(PartialEq, Eq, Clone, Debug)]
 pub struct LocalEnv {
    // Base directory for all the nodes (the pageserver, safekeepers and
    // compute endpoints).
@@ -42,59 +44,99 @@ pub struct LocalEnv {
    // This is not stored in the config file. Rather, this is the path where the
    // config file itself is. It is read from the NEON_REPO_DIR env variable or
    // '.neon' if not given.
-    #[serde(skip)]
    pub base_data_dir: PathBuf,

    // Path to postgres distribution. It's expected that "bin", "include",
    // "lib", "share" from postgres distribution are there. If at some point
    // in time we will be able to run against vanilla postgres we may split that
    // to four separate paths and match OS-specific installation layout.
-    #[serde(default)]
    pub pg_distrib_dir: PathBuf,

    // Path to pageserver binary.
-    #[serde(default)]
    pub neon_distrib_dir: PathBuf,

    // Default tenant ID to use with the 'neon_local' command line utility, when
    // --tenant_id is not explicitly specified.
-    #[serde(default)]
    pub default_tenant_id: Option<TenantId>,

    // used to issue tokens during e.g pg start
-    #[serde(default)]
    pub private_key_path: PathBuf,

    pub broker: NeonBroker,

    // Configuration for the storage controller (1 per neon_local environment)
-    #[serde(default)]
    pub storage_controller: NeonStorageControllerConf,

    /// This Vec must always contain at least one pageserver
+    /// Populdated by [`Self::load_config`] from the individual `pageserver.toml`s.
+    /// NB: not used anymore except for informing users that they need to change their `.neon/config`.
    pub pageservers: Vec<PageServerConf>,

-    #[serde(default)]
    pub safekeepers: Vec<SafekeeperConf>,

    // Control plane upcall API for pageserver: if None, we will not run storage_controller  If set, this will
    // be propagated into each pageserver's configuration.
-    #[serde(default)]
    pub control_plane_api: Option<Url>,

    // Control plane upcall API for storage controller.  If set, this will be propagated into the
    // storage controller's configuration.
-    #[serde(default)]
    pub control_plane_compute_hook_api: Option<Url>,

    /// Keep human-readable aliases in memory (and persist them to config), to hide ZId hex strings from the user.
-    #[serde(default)]
    // A `HashMap<String, HashMap<TenantId, TimelineId>>` would be more appropriate here,
    // but deserialization into a generic toml object as `toml::Value::try_from` fails with an error.
    // https://toml.io/en/v1.0.0 does not contain a concept of "a table inside another table".
+    pub branch_name_mappings: HashMap<String, Vec<(TenantId, TimelineId)>>,
+}
+
+/// On-disk state stored in `.neon/config`.
+#[derive(PartialEq, Eq, Clone, Debug, Default, Serialize, Deserialize)]
+#[serde(default, deny_unknown_fields)]
+pub struct OnDiskConfig {
+    pub pg_distrib_dir: PathBuf,
+    pub neon_distrib_dir: PathBuf,
+    pub default_tenant_id: Option<TenantId>,
+    pub private_key_path: PathBuf,
+    pub broker: NeonBroker,
+    pub storage_controller: NeonStorageControllerConf,
+    #[serde(
+        skip_serializing,
+        deserialize_with = "fail_if_pageservers_field_specified"
+    )]
+    pub pageservers: Vec<PageServerConf>,
+    pub safekeepers: Vec<SafekeeperConf>,
+    pub control_plane_api: Option<Url>,
+    pub control_plane_compute_hook_api: Option<Url>,
    branch_name_mappings: HashMap<String, Vec<(TenantId, TimelineId)>>,
 }

+fn fail_if_pageservers_field_specified<'de, D>(_: D) -> Result<Vec<PageServerConf>, D::Error>
+where
+    D: serde::Deserializer<'de>,
+{
+    Err(serde::de::Error::custom(
+        "The 'pageservers' field is no longer used; pageserver.toml is now authoritative; \
+         Please remove the `pageservers` from your .neon/config.",
+    ))
+}
+
+/// The description of the neon_local env to be initialized by `neon_local init --config`.
+#[derive(Clone, Debug, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct NeonLocalInitConf {
+    // TODO: do we need this? Seems unused
+    pub pg_distrib_dir: Option<PathBuf>,
+    // TODO: do we need this? Seems unused
+    pub neon_distrib_dir: Option<PathBuf>,
+    pub default_tenant_id: TenantId,
+    pub broker: NeonBroker,
+    pub storage_controller: Option<NeonStorageControllerConf>,
+    pub pageservers: Vec<NeonLocalInitPageserverConf>,
+    pub safekeepers: Vec<SafekeeperConf>,
+    pub control_plane_api: Option<Option<Url>>,
+    pub control_plane_compute_hook_api: Option<Option<Url>>,
+}
+
 /// Broker config for cluster internal communication.
 #[derive(Serialize, Deserialize, PartialEq, Eq, Clone, Debug)]
 #[serde(default)]
@@ -141,24 +183,18 @@ impl NeonBroker {
    }
 }

+// neon_local needs to know this subset of pageserver configuration.
+// For legacy reasons, this information is duplicated from `pageserver.toml` into `.neon/config`.
+// It can get stale if `pageserver.toml` is changed.
+// TODO(christian): don't store this at all in `.neon/config`, always load it from `pageserver.toml`
 #[derive(Serialize, Deserialize, PartialEq, Eq, Clone, Debug)]
 #[serde(default, deny_unknown_fields)]
 pub struct PageServerConf {
-    // node id
    pub id: NodeId,
-
-    // Pageserver connection settings
    pub listen_pg_addr: String,
    pub listen_http_addr: String,
-
-    // auth type used for the PG and HTTP ports
    pub pg_auth_type: AuthType,
    pub http_auth_type: AuthType,
-
-    pub(crate) virtual_file_io_engine: Option<String>,
-    pub(crate) get_vectored_impl: Option<String>,
-    pub(crate) get_impl: Option<String>,
-    pub(crate) validate_vectored_get: Option<bool>,
 }

 impl Default for PageServerConf {
@@ -169,10 +205,40 @@ impl Default for PageServerConf {
            listen_http_addr: String::new(),
            pg_auth_type: AuthType::Trust,
            http_auth_type: AuthType::Trust,
-            virtual_file_io_engine: None,
-            get_vectored_impl: None,
-            get_impl: None,
-            validate_vectored_get: None,
+        }
+    }
+}
+
+/// The toml that can be passed to `neon_local init --config`.
+/// This is a subset of the `pageserver.toml` configuration.
+// TODO(christian): use pageserver_api::config::ConfigToml (PR #7656)
+#[derive(Clone, Debug, serde::Deserialize, serde::Serialize)]
+pub struct NeonLocalInitPageserverConf {
+    pub id: NodeId,
+    pub listen_pg_addr: String,
+    pub listen_http_addr: String,
+    pub pg_auth_type: AuthType,
+    pub http_auth_type: AuthType,
+    #[serde(flatten)]
+    pub other: HashMap<String, toml::Value>,
+}
+
+impl From<&NeonLocalInitPageserverConf> for PageServerConf {
+    fn from(conf: &NeonLocalInitPageserverConf) -> Self {
+        let NeonLocalInitPageserverConf {
+            id,
+            listen_pg_addr,
+            listen_http_addr,
+            pg_auth_type,
+            http_auth_type,
+            other: _,
+        } = conf;
+        Self {
+            id: *id,
+            listen_pg_addr: listen_pg_addr.clone(),
+            listen_http_addr: listen_http_addr.clone(),
+            pg_auth_type: *pg_auth_type,
+            http_auth_type: *http_auth_type,
        }
    }
 }
@@ -360,41 +426,7 @@ impl LocalEnv {
            .collect()
    }

-    /// Create a LocalEnv from a config file.
-    ///
-    /// Unlike 'load_config', this function fills in any defaults that are missing
-    /// from the config file.
-    pub fn parse_config(toml: &str) -> anyhow::Result<Self> {
-        let mut env: LocalEnv = toml::from_str(toml)?;
-
-        // Find postgres binaries.
-        // Follow POSTGRES_DISTRIB_DIR if set, otherwise look in "pg_install".
-        // Note that later in the code we assume, that distrib dirs follow the same pattern
-        // for all postgres versions.
-        if env.pg_distrib_dir == Path::new("") {
-            if let Some(postgres_bin) = env::var_os("POSTGRES_DISTRIB_DIR") {
-                env.pg_distrib_dir = postgres_bin.into();
-            } else {
-                let cwd = env::current_dir()?;
-                env.pg_distrib_dir = cwd.join("pg_install")
-            }
-        }
-
-        // Find neon binaries.
-        if env.neon_distrib_dir == Path::new("") {
-            env.neon_distrib_dir = env::current_exe()?.parent().unwrap().to_owned();
-        }
-
-        if env.pageservers.is_empty() {
-            anyhow::bail!("Configuration must contain at least one pageserver");
-        }
-
-        env.base_data_dir = base_path();
-
-        Ok(env)
-    }
-
-    /// Locate and load config
+    ///  Construct `Self` from on-disk state.
    pub fn load_config() -> anyhow::Result<Self> {
        let repopath = base_path();

@@ -408,38 +440,129 @@ impl LocalEnv {
        // TODO: check that it looks like a neon repository

        // load and parse file
-        let config = fs::read_to_string(repopath.join("config"))?;
-        let mut env: LocalEnv = toml::from_str(config.as_str())?;
+        let config_file_contents = fs::read_to_string(repopath.join("config"))?;
+        let on_disk_config: OnDiskConfig = toml::from_str(config_file_contents.as_str())?;
+        let mut env = {
+            let OnDiskConfig {
+                pg_distrib_dir,
+                neon_distrib_dir,
+                default_tenant_id,
+                private_key_path,
+                broker,
+                storage_controller,
+                pageservers,
+                safekeepers,
+                control_plane_api,
+                control_plane_compute_hook_api,
+                branch_name_mappings,
+            } = on_disk_config;
+            LocalEnv {
+                base_data_dir: repopath.clone(),
+                pg_distrib_dir,
+                neon_distrib_dir,
+                default_tenant_id,
+                private_key_path,
+                broker,
+                storage_controller,
+                pageservers,
+                safekeepers,
+                control_plane_api,
+                control_plane_compute_hook_api,
+                branch_name_mappings,
+            }
+        };

-        env.base_data_dir = repopath;
+        // The source of truth for pageserver configuration is the pageserver.toml.
+        assert!(
+            env.pageservers.is_empty(),
+            "we ensure this during deserialization"
+        );
+        env.pageservers = {
+            let iter = std::fs::read_dir(&repopath).context("open dir")?;
+            let mut pageservers = Vec::new();
+            for res in iter {
+                let dentry = res?;
+                const PREFIX: &str = "pageserver_";
+                let dentry_name = dentry
+                    .file_name()
+                    .into_string()
+                    .ok()
+                    .with_context(|| format!("non-utf8 dentry: {:?}", dentry.path()))
+                    .unwrap();
+                if !dentry_name.starts_with(PREFIX) {
+                    continue;
+                }
+                if !dentry.file_type().context("determine file type")?.is_dir() {
+                    anyhow::bail!("expected a directory, got {:?}", dentry.path());
+                }
+                let id = dentry_name[PREFIX.len()..]
+                    .parse::<NodeId>()
+                    .with_context(|| format!("parse id from {:?}", dentry.path()))?;
+                // TODO(christian): use pageserver_api::config::ConfigToml (PR #7656)
+                #[derive(serde::Serialize, serde::Deserialize)]
+                // (allow unknown fields, unlike PageServerConf)
+                struct PageserverConfigTomlSubset {
+                    id: NodeId,
+                    listen_pg_addr: String,
+                    listen_http_addr: String,
+                    pg_auth_type: AuthType,
+                    http_auth_type: AuthType,
+                }
+                let config_toml_path = dentry.path().join("pageserver.toml");
+                let config_toml: PageserverConfigTomlSubset = toml_edit::de::from_str(
+                    &std::fs::read_to_string(&config_toml_path)
+                        .with_context(|| format!("read {:?}", config_toml_path))?,
+                )
+                .context("parse pageserver.toml")?;
+                let PageserverConfigTomlSubset {
+                    id: config_toml_id,
+                    listen_pg_addr,
+                    listen_http_addr,
+                    pg_auth_type,
+                    http_auth_type,
+                } = config_toml;
+                let conf = PageServerConf {
+                    id: {
+                        anyhow::ensure!(
+                            config_toml_id == id,
+                            "id mismatch: config_toml.id={config_toml_id} id={id}",
+                        );
+                        id
+                    },
+                    listen_pg_addr,
+                    listen_http_addr,
+                    pg_auth_type,
+                    http_auth_type,
+                };
+                pageservers.push(conf);
+            }
+            pageservers
+        };

        Ok(env)
    }

-    pub fn persist_config(&self, base_path: &Path) -> anyhow::Result<()> {
-        // Currently, the user first passes a config file with 'neon_local init --config=<path>'
-        // We read that in, in `create_config`, and fill any missing defaults. Then it's saved
-        // to .neon/config. TODO: We lose any formatting and comments along the way, which is
-        // a bit sad.
-        let mut conf_content = r#"# This file describes a local deployment of the page server
-# and safekeeeper node. It is read by the 'neon_local' command-line
-# utility.
-"#
-        .to_string();
-
-        // Convert the LocalEnv to a toml file.
-        //
-        // This could be as simple as this:
-        //
-        // conf_content += &toml::to_string_pretty(env)?;
-        //
-        // But it results in a "values must be emitted before tables". I'm not sure
-        // why, AFAICS the table, i.e. 'safekeepers: Vec<SafekeeperConf>' is last.
-        // Maybe rust reorders the fields to squeeze avoid padding or something?
-        // In any case, converting to toml::Value first, and serializing that, works.
-        // See https://github.com/alexcrichton/toml-rs/issues/142
-        conf_content += &toml::to_string_pretty(&toml::Value::try_from(self)?)?;
+    pub fn persist_config(&self) -> anyhow::Result<()> {
+        Self::persist_config_impl(
+            &self.base_data_dir,
+            &OnDiskConfig {
+                pg_distrib_dir: self.pg_distrib_dir.clone(),
+                neon_distrib_dir: self.neon_distrib_dir.clone(),
+                default_tenant_id: self.default_tenant_id,
+                private_key_path: self.private_key_path.clone(),
+                broker: self.broker.clone(),
+                storage_controller: self.storage_controller.clone(),
+                pageservers: vec![], // it's skip_serializing anyway
+                safekeepers: self.safekeepers.clone(),
+                control_plane_api: self.control_plane_api.clone(),
+                control_plane_compute_hook_api: self.control_plane_compute_hook_api.clone(),
+                branch_name_mappings: self.branch_name_mappings.clone(),
+            },
+        )
+    }

+    pub fn persist_config_impl(base_path: &Path, config: &OnDiskConfig) -> anyhow::Result<()> {
+        let conf_content = &toml::to_string_pretty(config)?;
        let target_config_path = base_path.join("config");
        fs::write(&target_config_path, conf_content).with_context(|| {
            format!(
@@ -464,17 +587,13 @@ impl LocalEnv {
        }
    }

-    //
-    // Initialize a new Neon repository
-    //
-    pub fn init(&mut self, pg_version: u32, force: &InitForceMode) -> anyhow::Result<()> {
-        // check if config already exists
-        let base_path = &self.base_data_dir;
-        ensure!(
-            base_path != Path::new(""),
-            "repository base path is missing"
-        );
+    /// Materialize the [`NeonLocalInitConf`] to disk. Called during [`neon_local init`].
+    pub fn init(conf: NeonLocalInitConf, force: &InitForceMode) -> anyhow::Result<()> {
+        let base_path = base_path();
+        assert_ne!(base_path, Path::new(""));
+        let base_path = &base_path;

+        // create base_path dir
        if base_path.exists() {
            match force {
                InitForceMode::MustNotExist => {
@@ -506,70 +625,96 @@ impl LocalEnv {
                }
            }
        }
-
-        if !self.pg_bin_dir(pg_version)?.join("postgres").exists() {
-            bail!(
-                "Can't find postgres binary at {}",
-                self.pg_bin_dir(pg_version)?.display()
-            );
-        }
-        for binary in ["pageserver", "safekeeper"] {
-            if !self.neon_distrib_dir.join(binary).exists() {
-                bail!(
-                    "Can't find binary '{binary}' in neon distrib dir '{}'",
-                    self.neon_distrib_dir.display()
-                );
-            }
-        }
-
        if !base_path.exists() {
            fs::create_dir(base_path)?;
        }

+        let NeonLocalInitConf {
+            pg_distrib_dir,
+            neon_distrib_dir,
+            default_tenant_id,
+            broker,
+            storage_controller,
+            pageservers,
+            safekeepers,
+            control_plane_api,
+            control_plane_compute_hook_api,
+        } = conf;
+
+        // Find postgres binaries.
+        // Follow POSTGRES_DISTRIB_DIR if set, otherwise look in "pg_install".
+        // Note that later in the code we assume, that distrib dirs follow the same pattern
+        // for all postgres versions.
+        let pg_distrib_dir = pg_distrib_dir.unwrap_or_else(|| {
+            if let Some(postgres_bin) = env::var_os("POSTGRES_DISTRIB_DIR") {
+                postgres_bin.into()
+            } else {
+                let cwd = env::current_dir().unwrap();
+                cwd.join("pg_install")
+            }
+        });
+
+        // Find neon binaries.
+        let neon_distrib_dir = neon_distrib_dir
+            .unwrap_or_else(|| env::current_exe().unwrap().parent().unwrap().to_owned());
+
        // Generate keypair for JWT.
        //
        // The keypair is only needed if authentication is enabled in any of the
        // components. For convenience, we generate the keypair even if authentication
        // is not enabled, so that you can easily enable it after the initialization
-        // step. However, if the key generation fails, we treat it as non-fatal if
-        // authentication was not enabled.
-        if self.private_key_path == PathBuf::new() {
-            match generate_auth_keys(
-                base_path.join("auth_private_key.pem").as_path(),
-                base_path.join("auth_public_key.pem").as_path(),
-            ) {
-                Ok(()) => {
-                    self.private_key_path = PathBuf::from("auth_private_key.pem");
-                }
-                Err(e) => {
-                    if !self.auth_keys_needed() {
-                        eprintln!("Could not generate keypair for JWT authentication: {e}");
-                        eprintln!("Continuing anyway because authentication was not enabled");
-                        self.private_key_path = PathBuf::from("auth_private_key.pem");
-                    } else {
-                        return Err(e);
-                    }
-                }
-            }
+        // step.
+        generate_auth_keys(
+            base_path.join("auth_private_key.pem").as_path(),
+            base_path.join("auth_public_key.pem").as_path(),
+        )
+        .context("generate auth keys")?;
+        let private_key_path = PathBuf::from("auth_private_key.pem");
+
+        // create the runtime type because the remaining initialization code below needs
+        // a LocalEnv instance op operation
+        // TODO: refactor to avoid this, LocalEnv should only be constructed from on-disk state
+        let env = LocalEnv {
+            base_data_dir: base_path.clone(),
+            pg_distrib_dir,
+            neon_distrib_dir,
+            default_tenant_id: Some(default_tenant_id),
+            private_key_path,
+            broker,
+            storage_controller: storage_controller.unwrap_or_default(),
+            pageservers: pageservers.iter().map(Into::into).collect(),
+            safekeepers,
+            control_plane_api: control_plane_api.unwrap_or_default(),
+            control_plane_compute_hook_api: control_plane_compute_hook_api.unwrap_or_default(),
+            branch_name_mappings: Default::default(),
+        };
+
+        // create endpoints dir
+        fs::create_dir_all(env.endpoints_path())?;
+
+        // create safekeeper dirs
+        for safekeeper in &env.safekeepers {
+            fs::create_dir_all(SafekeeperNode::datadir_path_by_id(&env, safekeeper.id))?;
        }

-        fs::create_dir_all(self.endpoints_path())?;
-
-        for safekeeper in &self.safekeepers {
-            fs::create_dir_all(SafekeeperNode::datadir_path_by_id(self, safekeeper.id))?;
+        // initialize pageserver state
+        for (i, ps) in pageservers.into_iter().enumerate() {
+            let runtime_ps = &env.pageservers[i];
+            assert_eq!(&PageServerConf::from(&ps), runtime_ps);
+            fs::create_dir(env.pageserver_data_dir(ps.id))?;
+            PageServerNode::from_env(&env, runtime_ps)
+                .initialize(ps)
+                .context("pageserver init failed")?;
        }

-        self.persist_config(base_path)
-    }
+        // setup remote remote location for default LocalFs remote storage
+        std::fs::create_dir_all(env.base_data_dir.join(PAGESERVER_REMOTE_STORAGE_DIR))?;

-    fn auth_keys_needed(&self) -> bool {
-        self.pageservers.iter().any(|ps| {
-            ps.pg_auth_type == AuthType::NeonJWT || ps.http_auth_type == AuthType::NeonJWT
-        }) || self.safekeepers.iter().any(|sk| sk.auth_enabled)
+        env.persist_config()
    }
 }

-fn base_path() -> PathBuf {
+pub fn base_path() -> PathBuf {
    match std::env::var_os("NEON_REPO_DIR") {
        Some(val) => PathBuf::from(val),
        None => PathBuf::from(".neon"),
@@ -612,31 +757,3 @@ fn generate_auth_keys(private_key_path: &Path, public_key_path: &Path) -> anyhow
    }
    Ok(())
 }
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn simple_conf_parsing() {
-        let simple_conf_toml = include_str!("../simple.conf");
-        let simple_conf_parse_result = LocalEnv::parse_config(simple_conf_toml);
-        assert!(
-            simple_conf_parse_result.is_ok(),
-            "failed to parse simple config {simple_conf_toml}, reason: {simple_conf_parse_result:?}"
-        );
-
-        let string_to_replace = "listen_addr = '127.0.0.1:50051'";
-        let spoiled_url_str = "listen_addr = '!@$XOXO%^&'";
-        let spoiled_url_toml = simple_conf_toml.replace(string_to_replace, spoiled_url_str);
-        assert!(
-            spoiled_url_toml.contains(spoiled_url_str),
-            "Failed to replace string {string_to_replace} in the toml file {simple_conf_toml}"
-        );
-        let spoiled_url_parse_result = LocalEnv::parse_config(&spoiled_url_toml);
-        assert!(
-            spoiled_url_parse_result.is_err(),
-            "expected toml with invalid Url {spoiled_url_toml} to fail the parsing, but got {spoiled_url_parse_result:?}"
-        );
-    }
-}
--- a/control_plane/src/pageserver.rs
+++ b/control_plane/src/pageserver.rs
@@ -4,21 +4,21 @@
 //!
 //!   .neon/
 //!
-use std::borrow::Cow;
 use std::collections::HashMap;

 use std::io;
 use std::io::Write;
 use std::num::NonZeroU64;
 use std::path::PathBuf;
-use std::process::Command;
+use std::str::FromStr;
 use std::time::Duration;

 use anyhow::{bail, Context};
 use camino::Utf8PathBuf;
 use futures::SinkExt;
 use pageserver_api::models::{
-    self, LocationConfig, ShardParameters, TenantHistorySize, TenantInfo, TimelineInfo,
+    self, AuxFilePolicy, LocationConfig, ShardParameters, TenantHistorySize, TenantInfo,
+    TimelineInfo,
 };
 use pageserver_api::shard::TenantShardId;
 use pageserver_client::mgmt_api;
@@ -30,7 +30,7 @@ use utils::{
    lsn::Lsn,
 };

-use crate::local_env::PageServerConf;
+use crate::local_env::{NeonLocalInitPageserverConf, PageServerConf};
 use crate::{background_process, local_env::LocalEnv};

 /// Directory within .neon which will be used by default for LocalFs remote storage.
@@ -74,71 +74,23 @@ impl PageServerNode {
        }
    }

-    /// Merge overrides provided by the user on the command line with our default overides derived from neon_local configuration.
-    ///
-    /// These all end up on the command line of the `pageserver` binary.
-    fn neon_local_overrides(&self, cli_overrides: &[&str]) -> Vec<String> {
+    fn pageserver_init_make_toml(
+        &self,
+        conf: NeonLocalInitPageserverConf,
+    ) -> anyhow::Result<toml_edit::Document> {
+        assert_eq!(&PageServerConf::from(&conf), &self.conf, "during neon_local init, we derive the runtime state of ps conf (self.conf) from the --config flag fully");
+
+        // TODO(christian): instead of what we do here, create a pageserver_api::config::ConfigToml (PR #7656)
+
        // FIXME: the paths should be shell-escaped to handle paths with spaces, quotas etc.
        let pg_distrib_dir_param = format!(
            "pg_distrib_dir='{}'",
            self.env.pg_distrib_dir_raw().display()
        );

-        let PageServerConf {
-            id,
-            listen_pg_addr,
-            listen_http_addr,
-            pg_auth_type,
-            http_auth_type,
-            virtual_file_io_engine,
-            get_vectored_impl,
-            get_impl,
-            validate_vectored_get,
-        } = &self.conf;
-
-        let id = format!("id={}", id);
-
-        let http_auth_type_param = format!("http_auth_type='{}'", http_auth_type);
-        let listen_http_addr_param = format!("listen_http_addr='{}'", listen_http_addr);
-
-        let pg_auth_type_param = format!("pg_auth_type='{}'", pg_auth_type);
-        let listen_pg_addr_param = format!("listen_pg_addr='{}'", listen_pg_addr);
-        let virtual_file_io_engine = if let Some(virtual_file_io_engine) = virtual_file_io_engine {
-            format!("virtual_file_io_engine='{virtual_file_io_engine}'")
-        } else {
-            String::new()
-        };
-        let get_vectored_impl = if let Some(get_vectored_impl) = get_vectored_impl {
-            format!("get_vectored_impl='{get_vectored_impl}'")
-        } else {
-            String::new()
-        };
-        let get_impl = if let Some(get_impl) = get_impl {
-            format!("get_impl='{get_impl}'")
-        } else {
-            String::new()
-        };
-        let validate_vectored_get = if let Some(validate_vectored_get) = validate_vectored_get {
-            format!("validate_vectored_get={validate_vectored_get}")
-        } else {
-            String::new()
-        };
-
        let broker_endpoint_param = format!("broker_endpoint='{}'", self.env.broker.client_url());

-        let mut overrides = vec![
-            id,
-            pg_distrib_dir_param,
-            http_auth_type_param,
-            pg_auth_type_param,
-            listen_http_addr_param,
-            listen_pg_addr_param,
-            broker_endpoint_param,
-            virtual_file_io_engine,
-            get_vectored_impl,
-            get_impl,
-            validate_vectored_get,
-        ];
+        let mut overrides = vec![pg_distrib_dir_param, broker_endpoint_param];

        if let Some(control_plane_api) = &self.env.control_plane_api {
            overrides.push(format!(
@@ -148,7 +100,7 @@ impl PageServerNode {

            // Storage controller uses the same auth as pageserver: if JWT is enabled
            // for us, we will also need it to talk to them.
-            if matches!(http_auth_type, AuthType::NeonJWT) {
+            if matches!(conf.http_auth_type, AuthType::NeonJWT) {
                let jwt_token = self
                    .env
                    .generate_auth_token(&Claims::new(None, Scope::GenerationsApi))
@@ -157,31 +109,40 @@ impl PageServerNode {
            }
        }

-        if !cli_overrides
-            .iter()
-            .any(|c| c.starts_with("remote_storage"))
-        {
+        if !conf.other.contains_key("remote_storage") {
            overrides.push(format!(
                "remote_storage={{local_path='../{PAGESERVER_REMOTE_STORAGE_DIR}'}}"
            ));
        }

-        if *http_auth_type != AuthType::Trust || *pg_auth_type != AuthType::Trust {
+        if conf.http_auth_type != AuthType::Trust || conf.pg_auth_type != AuthType::Trust {
            // Keys are generated in the toplevel repo dir, pageservers' workdirs
            // are one level below that, so refer to keys with ../
            overrides.push("auth_validation_public_key_path='../auth_public_key.pem'".to_owned());
        }

        // Apply the user-provided overrides
-        overrides.extend(cli_overrides.iter().map(|&c| c.to_owned()));
+        overrides.push(
+            toml_edit::ser::to_string_pretty(&conf)
+                .expect("we deserialized this from toml earlier"),
+        );

-        overrides
+        // Turn `overrides` into a toml document.
+        // TODO: above code is legacy code, it should be refactored to use toml_edit directly.
+        let mut config_toml = toml_edit::Document::new();
+        for fragment_str in overrides {
+            let fragment = toml_edit::Document::from_str(&fragment_str)
+                .expect("all fragments in `overrides` are valid toml documents, this function controls that");
+            for (key, item) in fragment.iter() {
+                config_toml.insert(key, item.clone());
+            }
+        }
+        Ok(config_toml)
    }

    /// Initializes a pageserver node by creating its config with the overrides provided.
-    pub fn initialize(&self, config_overrides: &[&str]) -> anyhow::Result<()> {
-        // First, run `pageserver --init` and wait for it to write a config into FS and exit.
-        self.pageserver_init(config_overrides)
+    pub fn initialize(&self, conf: NeonLocalInitPageserverConf) -> anyhow::Result<()> {
+        self.pageserver_init(conf)
            .with_context(|| format!("Failed to run init for pageserver node {}", self.conf.id))
    }

@@ -197,11 +158,11 @@ impl PageServerNode {
            .expect("non-Unicode path")
    }

-    pub async fn start(&self, config_overrides: &[&str]) -> anyhow::Result<()> {
-        self.start_node(config_overrides, false).await
+    pub async fn start(&self) -> anyhow::Result<()> {
+        self.start_node().await
    }

-    fn pageserver_init(&self, config_overrides: &[&str]) -> anyhow::Result<()> {
+    fn pageserver_init(&self, conf: NeonLocalInitPageserverConf) -> anyhow::Result<()> {
        let datadir = self.repo_path();
        let node_id = self.conf.id;
        println!(
@@ -212,29 +173,20 @@ impl PageServerNode {
        );
        io::stdout().flush()?;

-        if !datadir.exists() {
-            std::fs::create_dir(&datadir)?;
-        }
-
-        let datadir_path_str = datadir.to_str().with_context(|| {
-            format!("Cannot start pageserver node {node_id} in path that has no string representation: {datadir:?}")
-        })?;
-        let mut args = self.pageserver_basic_args(config_overrides, datadir_path_str);
-        args.push(Cow::Borrowed("--init"));
-
-        let init_output = Command::new(self.env.pageserver_bin())
-            .args(args.iter().map(Cow::as_ref))
-            .envs(self.pageserver_env_variables()?)
-            .output()
-            .with_context(|| format!("Failed to run pageserver init for node {node_id}"))?;
-
-        anyhow::ensure!(
-            init_output.status.success(),
-            "Pageserver init for node {} did not finish successfully, stdout: {}, stderr: {}",
-            node_id,
-            String::from_utf8_lossy(&init_output.stdout),
-            String::from_utf8_lossy(&init_output.stderr),
-        );
+        let config = self
+            .pageserver_init_make_toml(conf)
+            .context("make pageserver toml")?;
+        let config_file_path = datadir.join("pageserver.toml");
+        let mut config_file = std::fs::OpenOptions::new()
+            .create_new(true)
+            .write(true)
+            .open(&config_file_path)
+            .with_context(|| format!("open pageserver toml for write: {config_file_path:?}"))?;
+        config_file
+            .write_all(config.to_string().as_bytes())
+            .context("write pageserver toml")?;
+        drop(config_file);
+        // TODO: invoke a TBD config-check command to validate that pageserver will start with the written config

        // Write metadata file, used by pageserver on startup to register itself with
        // the storage controller
@@ -248,12 +200,13 @@ impl PageServerNode {
        // situation: the metadata is written by some other script.
        std::fs::write(
            metadata_path,
-            serde_json::to_vec(&serde_json::json!({
-                "host": "localhost",
-                "port": self.pg_connection_config.port(),
-                "http_host": "localhost",
-                "http_port": http_port,
-            }))
+            serde_json::to_vec(&pageserver_api::config::NodeMetadata {
+                postgres_host: "localhost".to_string(),
+                postgres_port: self.pg_connection_config.port(),
+                http_host: "localhost".to_string(),
+                http_port,
+                other: HashMap::new(),
+            })
            .unwrap(),
        )
        .expect("Failed to write metadata file");
@@ -261,11 +214,7 @@ impl PageServerNode {
        Ok(())
    }

-    async fn start_node(
-        &self,
-        config_overrides: &[&str],
-        update_config: bool,
-    ) -> anyhow::Result<()> {
+    async fn start_node(&self) -> anyhow::Result<()> {
        // TODO: using a thread here because start_process() is not async but we need to call check_status()
        let datadir = self.repo_path();
        print!(
@@ -282,15 +231,12 @@ impl PageServerNode {
                self.conf.id, datadir,
            )
        })?;
-        let mut args = self.pageserver_basic_args(config_overrides, datadir_path_str);
-        if update_config {
-            args.push(Cow::Borrowed("--update-config"));
-        }
+        let args = vec!["-D", datadir_path_str];
        background_process::start_process(
            "pageserver",
            &datadir,
            &self.env.pageserver_bin(),
-            args.iter().map(Cow::as_ref),
+            args,
            self.pageserver_env_variables()?,
            background_process::InitialPidFile::Expect(self.pid_file()),
            || async {
@@ -307,22 +253,6 @@ impl PageServerNode {
        Ok(())
    }

-    fn pageserver_basic_args<'a>(
-        &self,
-        config_overrides: &'a [&'a str],
-        datadir_path_str: &'a str,
-    ) -> Vec<Cow<'a, str>> {
-        let mut args = vec![Cow::Borrowed("-D"), Cow::Borrowed(datadir_path_str)];
-
-        let overrides = self.neon_local_overrides(config_overrides);
-        for config_override in overrides {
-            args.push(Cow::Borrowed("-c"));
-            args.push(Cow::Owned(config_override));
-        }
-
-        args
-    }
-
    fn pageserver_env_variables(&self) -> anyhow::Result<Vec<(String, String)>> {
        // FIXME: why is this tied to pageserver's auth type? Whether or not the safekeeper
        // needs a token, and how to generate that token, seems independent to whether
@@ -448,11 +378,11 @@ impl PageServerNode {
                .map(serde_json::from_str)
                .transpose()
                .context("parse `timeline_get_throttle` from json")?,
-            switch_to_aux_file_v2: settings
-                .remove("switch_to_aux_file_v2")
-                .map(|x| x.parse::<bool>())
+            switch_aux_file_policy: settings
+                .remove("switch_aux_file_policy")
+                .map(|x| x.parse::<AuxFilePolicy>())
                .transpose()
-                .context("Failed to parse 'switch_to_aux_file_v2' as bool")?,
+                .context("Failed to parse 'switch_aux_file_policy'")?,
        };
        if !settings.is_empty() {
            bail!("Unrecognized tenant settings: {settings:?}")
@@ -571,11 +501,11 @@ impl PageServerNode {
                    .map(serde_json::from_str)
                    .transpose()
                    .context("parse `timeline_get_throttle` from json")?,
-                switch_to_aux_file_v2: settings
-                    .remove("switch_to_aux_file_v2")
-                    .map(|x| x.parse::<bool>())
+                switch_aux_file_policy: settings
+                    .remove("switch_aux_file_policy")
+                    .map(|x| x.parse::<AuxFilePolicy>())
                    .transpose()
-                    .context("Failed to parse 'switch_to_aux_file_v2' as bool")?,
+                    .context("Failed to parse 'switch_aux_file_policy'")?,
            }
        };

--- a/control_plane/src/storage_controller.rs
+++ b/control_plane/src/storage_controller.rs
@@ -3,7 +3,6 @@ use crate::{
    local_env::{LocalEnv, NeonStorageControllerConf},
 };
 use camino::{Utf8Path, Utf8PathBuf};
-use hyper::Method;
 use pageserver_api::{
    controller_api::{
        NodeConfigureRequest, NodeRegisterRequest, TenantCreateResponse, TenantLocateResponse,
@@ -17,6 +16,7 @@ use pageserver_api::{
 };
 use pageserver_client::mgmt_api::ResponseErrorMessageExt;
 use postgres_backend::AuthType;
+use reqwest::Method;
 use serde::{de::DeserializeOwned, Deserialize, Serialize};
 use std::{fs, str::FromStr};
 use tokio::process::Command;
@@ -379,7 +379,7 @@ impl StorageController {
    /// Simple HTTP request wrapper for calling into storage controller
    async fn dispatch<RQ, RS>(
        &self,
-        method: hyper::Method,
+        method: reqwest::Method,
        path: String,
        body: Option<RQ>,
    ) -> anyhow::Result<RS>
--- a/control_plane/storcon_cli/src/main.rs
+++ b/control_plane/storcon_cli/src/main.rs
@@ -1,7 +1,6 @@
 use std::{collections::HashMap, str::FromStr, time::Duration};

 use clap::{Parser, Subcommand};
-use hyper::{Method, StatusCode};
 use pageserver_api::{
    controller_api::{
        NodeAvailabilityWrapper, NodeDescribeResponse, ShardSchedulingPolicy,
@@ -14,7 +13,7 @@ use pageserver_api::{
    shard::{ShardStripeSize, TenantShardId},
 };
 use pageserver_client::mgmt_api::{self, ResponseErrorMessageExt};
-use reqwest::Url;
+use reqwest::{Method, StatusCode, Url};
 use serde::{de::DeserializeOwned, Serialize};
 use utils::id::{NodeId, TenantId};

@@ -232,7 +231,7 @@ impl Client {
    /// Simple HTTP request wrapper for calling into storage controller
    async fn dispatch<RQ, RS>(
        &self,
-        method: hyper::Method,
+        method: Method,
        path: String,
        body: Option<RQ>,
    ) -> mgmt_api::Result<RS>
--- a/libs/compute_api/src/spec.rs
+++ b/libs/compute_api/src/spec.rs
@@ -33,6 +33,23 @@ pub struct ComputeSpec {
    #[serde(default)]
    pub features: Vec<ComputeFeature>,

+    /// If compute_ctl was passed `--resize-swap-on-bind`, a value of `Some(_)` instructs
+    /// compute_ctl to `/neonvm/bin/resize-swap` with the given size, when the spec is first
+    /// received.
+    ///
+    /// Both this field and `--resize-swap-on-bind` are required, so that the control plane's
+    /// spec generation doesn't need to be aware of the actual compute it's running on, while
+    /// guaranteeing gradual rollout of swap. Otherwise, without `--resize-swap-on-bind`, we could
+    /// end up trying to resize swap in VMs without it -- or end up *not* resizing swap, thus
+    /// giving every VM much more swap than it should have (32GiB).
+    ///
+    /// Eventually we may remove `--resize-swap-on-bind` and exclusively use `swap_size_bytes` for
+    /// enabling the swap resizing behavior once rollout is complete.
+    ///
+    /// See neondatabase/cloud#12047 for more.
+    #[serde(default)]
+    pub swap_size_bytes: Option<u64>,
+
    /// Expected cluster state at the end of transition process.
    pub cluster: Cluster,
    pub delta_operations: Option<Vec<DeltaOp>>,
--- a/libs/metrics/src/lib.rs
+++ b/libs/metrics/src/lib.rs
@@ -480,6 +480,15 @@ impl<A: CounterPairAssoc> CounterPairVec<A> {
        let id = self.vec.with_labels(labels);
        self.vec.remove_metric(id)
    }
+
+    pub fn sample(&self, labels: <A::LabelGroupSet as LabelGroupSet>::Group<'_>) -> u64 {
+        let id = self.vec.with_labels(labels);
+        let metric = self.vec.get_metric(id);
+
+        let inc = metric.inc.count.load(std::sync::atomic::Ordering::Relaxed);
+        let dec = metric.dec.count.load(std::sync::atomic::Ordering::Relaxed);
+        inc.saturating_sub(dec)
+    }
 }

 impl<T, A> ::measured::metric::group::MetricGroup<T> for CounterPairVec<A>
--- a/libs/pageserver_api/src/config.rs
+++ b/libs/pageserver_api/src/config.rs
@@ -0,0 +1,31 @@
+use std::collections::HashMap;
+
+use const_format::formatcp;
+
+#[cfg(test)]
+mod tests;
+
+pub const DEFAULT_PG_LISTEN_PORT: u16 = 64000;
+pub const DEFAULT_PG_LISTEN_ADDR: &str = formatcp!("127.0.0.1:{DEFAULT_PG_LISTEN_PORT}");
+pub const DEFAULT_HTTP_LISTEN_PORT: u16 = 9898;
+pub const DEFAULT_HTTP_LISTEN_ADDR: &str = formatcp!("127.0.0.1:{DEFAULT_HTTP_LISTEN_PORT}");
+
+// Certain metadata (e.g. externally-addressable name, AZ) is delivered
+// as a separate structure.  This information is not neeed by the pageserver
+// itself, it is only used for registering the pageserver with the control
+// plane and/or storage controller.
+//
+#[derive(PartialEq, Eq, Debug, serde::Serialize, serde::Deserialize)]
+pub struct NodeMetadata {
+    #[serde(rename = "host")]
+    pub postgres_host: String,
+    #[serde(rename = "port")]
+    pub postgres_port: u16,
+    pub http_host: String,
+    pub http_port: u16,
+
+    // Deployment tools may write fields to the metadata file beyond what we
+    // use in this type: this type intentionally only names fields that require.
+    #[serde(flatten)]
+    pub other: HashMap<String, serde_json::Value>,
+}
--- a/libs/pageserver_api/src/config/tests.rs
+++ b/libs/pageserver_api/src/config/tests.rs
@@ -0,0 +1,22 @@
+use super::*;
+
+#[test]
+fn test_node_metadata_v1_backward_compatibilty() {
+    let v1 = serde_json::to_vec(&serde_json::json!({
+        "host": "localhost",
+        "port": 23,
+        "http_host": "localhost",
+        "http_port": 42,
+    }));
+
+    assert_eq!(
+        serde_json::from_slice::<NodeMetadata>(&v1.unwrap()).unwrap(),
+        NodeMetadata {
+            postgres_host: "localhost".to_string(),
+            postgres_port: 23,
+            http_host: "localhost".to_string(),
+            http_port: 42,
+            other: HashMap::new(),
+        }
+    )
+}
--- a/libs/pageserver_api/src/key.rs
+++ b/libs/pageserver_api/src/key.rs
@@ -80,7 +80,7 @@ impl Key {
    }

    /// Get the range of metadata keys.
-    pub fn metadata_key_range() -> Range<Self> {
+    pub const fn metadata_key_range() -> Range<Self> {
        Key {
            field1: METADATA_KEY_BEGIN_PREFIX,
            field2: 0,
@@ -572,14 +572,17 @@ pub const AUX_FILES_KEY: Key = Key {
 // Reverse mappings for a few Keys.
 // These are needed by WAL redo manager.

+/// Non inherited range for vectored get.
 pub const NON_INHERITED_RANGE: Range<Key> = AUX_FILES_KEY..AUX_FILES_KEY.next();
+/// Sparse keyspace range for vectored get. Missing key error will be ignored for this range.
+pub const NON_INHERITED_SPARSE_RANGE: Range<Key> = Key::metadata_key_range();

 // AUX_FILES currently stores only data for logical replication (slots etc), and
 // we don't preserve these on a branch because safekeepers can't follow timeline
 // switch (and generally it likely should be optional), so ignore these.
 #[inline(always)]
 pub fn is_inherited_key(key: Key) -> bool {
-    !NON_INHERITED_RANGE.contains(&key)
+    !NON_INHERITED_RANGE.contains(&key) && !NON_INHERITED_SPARSE_RANGE.contains(&key)
 }

 #[inline(always)]
--- a/libs/pageserver_api/src/keyspace.rs
+++ b/libs/pageserver_api/src/keyspace.rs
@@ -240,7 +240,7 @@ impl<'a> ShardedRange<'a> {
    /// pages that would not actually be stored on this node.
    ///
    /// Don't use this function in code that works with physical entities like layer files.
-    fn raw_size(range: &Range<Key>) -> u32 {
+    pub fn raw_size(range: &Range<Key>) -> u32 {
        if is_contiguous_range(range) {
            contiguous_range_len(range)
        } else {
--- a/libs/pageserver_api/src/lib.rs
+++ b/libs/pageserver_api/src/lib.rs
@@ -1,6 +1,5 @@
 #![deny(unsafe_code)]
 #![deny(clippy::undocumented_unsafe_blocks)]
-use const_format::formatcp;

 pub mod controller_api;
 pub mod key;
@@ -11,7 +10,4 @@ pub mod shard;
 /// Public API types
 pub mod upcall_api;

-pub const DEFAULT_PG_LISTEN_PORT: u16 = 64000;
-pub const DEFAULT_PG_LISTEN_ADDR: &str = formatcp!("127.0.0.1:{DEFAULT_PG_LISTEN_PORT}");
-pub const DEFAULT_HTTP_LISTEN_PORT: u16 = 9898;
-pub const DEFAULT_HTTP_LISTEN_ADDR: &str = formatcp!("127.0.0.1:{DEFAULT_HTTP_LISTEN_PORT}");
+pub mod config;
--- a/libs/pageserver_api/src/models.rs
+++ b/libs/pageserver_api/src/models.rs
@@ -1,3 +1,4 @@
+pub mod detach_ancestor;
 pub mod partitioning;
 pub mod utilization;

@@ -8,6 +9,7 @@ use std::{
    collections::HashMap,
    io::{BufRead, Read},
    num::{NonZeroU64, NonZeroUsize},
+    str::FromStr,
    time::{Duration, SystemTime},
 };

@@ -303,7 +305,31 @@ pub struct TenantConfig {
    pub lazy_slru_download: Option<bool>,
    pub timeline_get_throttle: Option<ThrottleConfig>,
    pub image_layer_creation_check_threshold: Option<u8>,
-    pub switch_to_aux_file_v2: Option<bool>,
+    pub switch_aux_file_policy: Option<AuxFilePolicy>,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub enum AuxFilePolicy {
+    V1,
+    V2,
+    CrossValidation,
+}
+
+impl FromStr for AuxFilePolicy {
+    type Err = anyhow::Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let s = s.to_lowercase();
+        if s == "v1" {
+            Ok(Self::V1)
+        } else if s == "v2" {
+            Ok(Self::V2)
+        } else if s == "crossvalidation" || s == "cross_validation" {
+            Ok(Self::CrossValidation)
+        } else {
+            anyhow::bail!("cannot parse {} to aux file policy", s)
+        }
+    }
 }

 #[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
@@ -430,8 +456,6 @@ pub struct StatusResponse {
 #[derive(Serialize, Deserialize, Debug)]
 #[serde(deny_unknown_fields)]
 pub struct TenantLocationConfigRequest {
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub tenant_id: Option<TenantShardId>,
    #[serde(flatten)]
    pub config: LocationConfig, // as we have a flattened field, we should reject all unknown fields in it
 }
--- a/libs/pageserver_api/src/models/detach_ancestor.rs
+++ b/libs/pageserver_api/src/models/detach_ancestor.rs
@@ -0,0 +1,6 @@
+use utils::id::TimelineId;
+
+#[derive(Default, serde::Serialize)]
+pub struct AncestorDetached {
+    pub reparented_timelines: Vec<TimelineId>,
+}
--- a/libs/pageserver_api/src/shard.rs
+++ b/libs/pageserver_api/src/shard.rs
@@ -97,7 +97,7 @@ impl ShardCount {

    /// The internal value of a ShardCount may be zero, which means "1 shard, but use
    /// legacy format for TenantShardId that excludes the shard suffix", also known
-    /// as `TenantShardId::unsharded`.
+    /// as [`TenantShardId::unsharded`].
    ///
    /// This method returns the actual number of shards, i.e. if our internal value is
    /// zero, we return 1 (unsharded tenants have 1 shard).
@@ -116,7 +116,9 @@ impl ShardCount {
        self.0
    }

-    ///
+    /// Whether the `ShardCount` is for an unsharded tenant, so uses one shard but
+    /// uses the legacy format for `TenantShardId`. See also the documentation for
+    /// [`Self::count`].
    pub fn is_unsharded(&self) -> bool {
        self.0 == 0
    }
--- a/libs/postgres_ffi/src/xlog_utils.rs
+++ b/libs/postgres_ffi/src/xlog_utils.rs
@@ -331,7 +331,10 @@ impl CheckPoint {
    /// Returns 'true' if the XID was updated.
    pub fn update_next_xid(&mut self, xid: u32) -> bool {
        // nextXid should be greater than any XID in WAL, so increment provided XID and check for wraparround.
-        let mut new_xid = std::cmp::max(xid.wrapping_add(1), pg_constants::FIRST_NORMAL_TRANSACTION_ID);
+        let mut new_xid = std::cmp::max(
+            xid.wrapping_add(1),
+            pg_constants::FIRST_NORMAL_TRANSACTION_ID,
+        );
        // To reduce number of metadata checkpoints, we forward align XID on XID_CHECKPOINT_INTERVAL.
        // XID_CHECKPOINT_INTERVAL should not be larger than BLCKSZ*CLOG_XACTS_PER_BYTE
        new_xid =
@@ -367,8 +370,16 @@ pub fn generate_wal_segment(segno: u64, system_id: u64, lsn: Lsn) -> Result<Byte
    let seg_off = lsn.segment_offset(WAL_SEGMENT_SIZE);

    let first_page_only = seg_off < XLOG_BLCKSZ;
-    let (shdr_rem_len, infoflags) = if first_page_only {
-        (seg_off, pg_constants::XLP_FIRST_IS_CONTRECORD)
+    // If first records starts in the middle of the page, pretend in page header
+    // there is a fake record which ends where first real record starts. This
+    // makes pg_waldump etc happy.
+    let (shdr_rem_len, infoflags) = if first_page_only && seg_off > 0 {
+        assert!(seg_off >= XLOG_SIZE_OF_XLOG_LONG_PHD);
+        // xlp_rem_len doesn't include page header, hence the subtraction.
+        (
+            seg_off - XLOG_SIZE_OF_XLOG_LONG_PHD,
+            pg_constants::XLP_FIRST_IS_CONTRECORD,
+        )
    } else {
        (0, 0)
    };
@@ -397,20 +408,22 @@ pub fn generate_wal_segment(segno: u64, system_id: u64, lsn: Lsn) -> Result<Byte

    if !first_page_only {
        let block_offset = lsn.page_offset_in_segment(WAL_SEGMENT_SIZE) as usize;
+        // see comments above about XLP_FIRST_IS_CONTRECORD and xlp_rem_len.
+        let (xlp_rem_len, xlp_info) = if page_off > 0 {
+            assert!(page_off >= XLOG_SIZE_OF_XLOG_SHORT_PHD as u64);
+            (
+                (page_off - XLOG_SIZE_OF_XLOG_SHORT_PHD as u64) as u32,
+                pg_constants::XLP_FIRST_IS_CONTRECORD,
+            )
+        } else {
+            (0, 0)
+        };
        let header = XLogPageHeaderData {
            xlp_magic: XLOG_PAGE_MAGIC as u16,
-            xlp_info: if page_off >= pg_constants::SIZE_OF_PAGE_HEADER as u64 {
-                pg_constants::XLP_FIRST_IS_CONTRECORD
-            } else {
-                0
-            },
+            xlp_info,
            xlp_tli: PG_TLI,
            xlp_pageaddr: lsn.page_lsn().0,
-            xlp_rem_len: if page_off >= pg_constants::SIZE_OF_PAGE_HEADER as u64 {
-                page_off as u32
-            } else {
-                0u32
-            },
+            xlp_rem_len,
            ..Default::default() // Put 0 in padding fields.
        };
        let hdr_bytes = header.encode()?;
--- a/libs/remote_storage/Cargo.toml
+++ b/libs/remote_storage/Cargo.toml
@@ -38,6 +38,7 @@ azure_storage_blobs.workspace = true
 futures-util.workspace = true
 http-types.workspace = true
 itertools.workspace = true
+sync_wrapper = { workspace = true, features = ["futures"] }

 [dev-dependencies]
 camino-tempfile.workspace = true
--- a/libs/remote_storage/src/azure_blob.rs
+++ b/libs/remote_storage/src/azure_blob.rs
@@ -3,6 +3,7 @@
 use std::borrow::Cow;
 use std::collections::HashMap;
 use std::env;
+use std::io;
 use std::num::NonZeroU32;
 use std::pin::Pin;
 use std::str::FromStr;
@@ -20,6 +21,7 @@ use azure_storage_blobs::blob::CopyStatus;
 use azure_storage_blobs::prelude::ClientBuilder;
 use azure_storage_blobs::{blob::operations::GetBlobBuilder, prelude::ContainerClient};
 use bytes::Bytes;
+use futures::future::Either;
 use futures::stream::Stream;
 use futures_util::StreamExt;
 use futures_util::TryStreamExt;
@@ -128,12 +130,12 @@ impl AzureBlobStorage {
        let kind = RequestKind::Get;

        let _permit = self.permit(kind, cancel).await?;
+        let cancel_or_timeout = crate::support::cancel_or_timeout(self.timeout, cancel.clone());
+        let cancel_or_timeout_ = crate::support::cancel_or_timeout(self.timeout, cancel.clone());

        let mut etag = None;
        let mut last_modified = None;
        let mut metadata = HashMap::new();
-        // TODO give proper streaming response instead of buffering into RAM
-        // https://github.com/neondatabase/neon/issues/5563

        let download = async {
            let response = builder
@@ -152,39 +154,46 @@ impl AzureBlobStorage {
                Err(_elapsed) => Err(DownloadError::Timeout),
            });

-            let mut response = std::pin::pin!(response);
+            let mut response = Box::pin(response);

-            let mut bufs = Vec::new();
-            while let Some(part) = response.next().await {
-                let part = part?;
-                if etag.is_none() {
-                    etag = Some(part.blob.properties.etag);
-                }
-                if last_modified.is_none() {
-                    last_modified = Some(part.blob.properties.last_modified.into());
-                }
-                if let Some(blob_meta) = part.blob.metadata {
-                    metadata.extend(blob_meta.iter().map(|(k, v)| (k.to_owned(), v.to_owned())));
-                }
-                let data = part
-                    .data
-                    .collect()
-                    .await
-                    .map_err(|e| DownloadError::Other(e.into()))?;
-                bufs.push(data);
-            }
-
-            if bufs.is_empty() {
+            let Some(part) = response.next().await else {
                return Err(DownloadError::Other(anyhow::anyhow!(
-                    "Azure GET response contained no buffers"
+                    "Azure GET response contained no response body"
                )));
+            };
+            let part = part?;
+            if etag.is_none() {
+                etag = Some(part.blob.properties.etag);
            }
+            if last_modified.is_none() {
+                last_modified = Some(part.blob.properties.last_modified.into());
+            }
+            if let Some(blob_meta) = part.blob.metadata {
+                metadata.extend(blob_meta.iter().map(|(k, v)| (k.to_owned(), v.to_owned())));
+            }
+
            // unwrap safety: if these were None, bufs would be empty and we would have returned an error already
            let etag = etag.unwrap();
            let last_modified = last_modified.unwrap();

+            let tail_stream = response
+                .map(|part| match part {
+                    Ok(part) => Either::Left(part.data.map(|r| r.map_err(io::Error::other))),
+                    Err(e) => {
+                        Either::Right(futures::stream::once(async { Err(io::Error::other(e)) }))
+                    }
+                })
+                .flatten();
+            let stream = part
+                .data
+                .map(|r| r.map_err(io::Error::other))
+                .chain(sync_wrapper::SyncStream::new(tail_stream));
+            //.chain(SyncStream::from_pin(Box::pin(tail_stream)));
+
+            let download_stream = crate::support::DownloadStream::new(cancel_or_timeout_, stream);
+
            Ok(Download {
-                download_stream: Box::pin(futures::stream::iter(bufs.into_iter().map(Ok))),
+                download_stream: Box::pin(download_stream),
                etag,
                last_modified,
                metadata: Some(StorageMetadata(metadata)),
@@ -193,7 +202,10 @@ impl AzureBlobStorage {

        tokio::select! {
            bufs = download => bufs,
-            _ = cancel.cancelled() => Err(DownloadError::Cancelled),
+            cancel_or_timeout = cancel_or_timeout => match cancel_or_timeout {
+                TimeoutOrCancel::Timeout => Err(DownloadError::Timeout),
+                TimeoutOrCancel::Cancel => Err(DownloadError::Cancelled),
+            },
        }
    }

--- a/libs/remote_storage/src/lib.rs
+++ b/libs/remote_storage/src/lib.rs
@@ -55,11 +55,11 @@ pub use error::{DownloadError, TimeTravelError, TimeoutOrCancel};
 /// ~3500 PUT/COPY/POST/DELETE or 5500 GET/HEAD S3 requests
 /// <https://aws.amazon.com/premiumsupport/knowledge-center/s3-request-limit-avoid-throttling/>
 pub const DEFAULT_REMOTE_STORAGE_S3_CONCURRENCY_LIMIT: usize = 100;
-/// We set this a little bit low as we currently buffer the entire file into RAM
+/// Set this limit analogously to the S3 limit
 ///
 /// Here, a limit of max 20k concurrent connections was noted.
 /// <https://learn.microsoft.com/en-us/answers/questions/1301863/is-there-any-limitation-to-concurrent-connections>
-pub const DEFAULT_REMOTE_STORAGE_AZURE_CONCURRENCY_LIMIT: usize = 30;
+pub const DEFAULT_REMOTE_STORAGE_AZURE_CONCURRENCY_LIMIT: usize = 100;
 /// No limits on the client side, which currenltly means 1000 for AWS S3.
 /// <https://docs.aws.amazon.com/AmazonS3/latest/API/API_ListObjectsV2.html#API_ListObjectsV2_RequestSyntax>
 pub const DEFAULT_MAX_KEYS_PER_LIST_RESPONSE: Option<i32> = None;
--- a/libs/remote_storage/src/s3_bucket.rs
+++ b/libs/remote_storage/src/s3_bucket.rs
@@ -27,7 +27,7 @@ use aws_config::{
 };
 use aws_credential_types::provider::SharedCredentialsProvider;
 use aws_sdk_s3::{
-    config::{AsyncSleep, Builder, IdentityCache, Region, SharedAsyncSleep},
+    config::{AsyncSleep, IdentityCache, Region, SharedAsyncSleep},
    error::SdkError,
    operation::get_object::GetObjectError,
    types::{Delete, DeleteMarkerEntry, ObjectIdentifier, ObjectVersion, StorageClass},
@@ -75,13 +75,13 @@ struct GetObjectRequest {
 }
 impl S3Bucket {
    /// Creates the S3 storage, errors if incorrect AWS S3 configuration provided.
-    pub fn new(aws_config: &S3Config, timeout: Duration) -> anyhow::Result<Self> {
+    pub fn new(remote_storage_config: &S3Config, timeout: Duration) -> anyhow::Result<Self> {
        tracing::debug!(
            "Creating s3 remote storage for S3 bucket {}",
-            aws_config.bucket_name
+            remote_storage_config.bucket_name
        );

-        let region = Some(Region::new(aws_config.bucket_region.clone()));
+        let region = Some(Region::new(remote_storage_config.bucket_region.clone()));

        let provider_conf = ProviderConfig::without_region().with_region(region.clone());

@@ -113,6 +113,38 @@ impl S3Bucket {
        // AWS SDK requires us to specify how the RetryConfig should sleep when it wants to back off
        let sleep_impl: Arc<dyn AsyncSleep> = Arc::new(TokioSleep::new());

+        let sdk_config_loader: aws_config::ConfigLoader = aws_config::defaults(
+            #[allow(deprecated)] /* TODO: https://github.com/neondatabase/neon/issues/7665 */
+            BehaviorVersion::v2023_11_09(),
+        )
+        .region(region)
+        .identity_cache(IdentityCache::lazy().build())
+        .credentials_provider(SharedCredentialsProvider::new(credentials_provider))
+        .sleep_impl(SharedAsyncSleep::from(sleep_impl));
+
+        let sdk_config: aws_config::SdkConfig = std::thread::scope(|s| {
+            s.spawn(|| {
+                // TODO: make this function async.
+                tokio::runtime::Builder::new_current_thread()
+                    .enable_all()
+                    .build()
+                    .unwrap()
+                    .block_on(sdk_config_loader.load())
+            })
+            .join()
+            .unwrap()
+        });
+
+        let mut s3_config_builder = aws_sdk_s3::config::Builder::from(&sdk_config);
+
+        // Technically, the `remote_storage_config.endpoint` field only applies to S3 interactions.
+        // (In case we ever re-use the `sdk_config` for more than just the S3 client in the future)
+        if let Some(custom_endpoint) = remote_storage_config.endpoint.clone() {
+            s3_config_builder = s3_config_builder
+                .endpoint_url(custom_endpoint)
+                .force_path_style(true);
+        }
+
        // We do our own retries (see [`backoff::retry`]).  However, for the AWS SDK to enable rate limiting in response to throttling
        // responses (e.g. 429 on too many ListObjectsv2 requests), we must provide a retry config.  We set it to use at most one
        // attempt, and enable 'Adaptive' mode, which causes rate limiting to be enabled.
@@ -120,42 +152,36 @@ impl S3Bucket {
        retry_config
            .set_max_attempts(Some(1))
            .set_mode(Some(RetryMode::Adaptive));
+        s3_config_builder = s3_config_builder.retry_config(retry_config.build());

-        let mut config_builder = Builder::default()
-            .behavior_version(BehaviorVersion::v2023_11_09())
-            .region(region)
-            .identity_cache(IdentityCache::lazy().build())
-            .credentials_provider(SharedCredentialsProvider::new(credentials_provider))
-            .retry_config(retry_config.build())
-            .sleep_impl(SharedAsyncSleep::from(sleep_impl));
+        let s3_config = s3_config_builder.build();
+        let client = aws_sdk_s3::Client::from_conf(s3_config);

-        if let Some(custom_endpoint) = aws_config.endpoint.clone() {
-            config_builder = config_builder
-                .endpoint_url(custom_endpoint)
-                .force_path_style(true);
-        }
+        let prefix_in_bucket = remote_storage_config
+            .prefix_in_bucket
+            .as_deref()
+            .map(|prefix| {
+                let mut prefix = prefix;
+                while prefix.starts_with(REMOTE_STORAGE_PREFIX_SEPARATOR) {
+                    prefix = &prefix[1..]
+                }

-        let client = Client::from_conf(config_builder.build());
+                let mut prefix = prefix.to_string();
+                while prefix.ends_with(REMOTE_STORAGE_PREFIX_SEPARATOR) {
+                    prefix.pop();
+                }
+                prefix
+            });

-        let prefix_in_bucket = aws_config.prefix_in_bucket.as_deref().map(|prefix| {
-            let mut prefix = prefix;
-            while prefix.starts_with(REMOTE_STORAGE_PREFIX_SEPARATOR) {
-                prefix = &prefix[1..]
-            }
-
-            let mut prefix = prefix.to_string();
-            while prefix.ends_with(REMOTE_STORAGE_PREFIX_SEPARATOR) {
-                prefix.pop();
-            }
-            prefix
-        });
        Ok(Self {
            client,
-            bucket_name: aws_config.bucket_name.clone(),
-            max_keys_per_list_response: aws_config.max_keys_per_list_response,
+            bucket_name: remote_storage_config.bucket_name.clone(),
+            max_keys_per_list_response: remote_storage_config.max_keys_per_list_response,
            prefix_in_bucket,
-            concurrency_limiter: ConcurrencyLimiter::new(aws_config.concurrency_limit.get()),
-            upload_storage_class: aws_config.upload_storage_class.clone(),
+            concurrency_limiter: ConcurrencyLimiter::new(
+                remote_storage_config.concurrency_limit.get(),
+            ),
+            upload_storage_class: remote_storage_config.upload_storage_class.clone(),
            timeout,
        })
    }
--- a/libs/utils/src/poison.rs
+++ b/libs/utils/src/poison.rs
@@ -3,7 +3,7 @@
 //!  # Example
 //!
 //!  ```
-//!  # tokio_test::block_on(async {
+//!  # tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap().block_on(async {
 //!  use utils::poison::Poison;
 //!  use std::time::Duration;
 //!
--- a/libs/walproposer/src/api_bindings.rs
+++ b/libs/walproposer/src/api_bindings.rs
@@ -50,6 +50,14 @@ extern "C" fn get_flush_rec_ptr(wp: *mut WalProposer) -> XLogRecPtr {
    }
 }

+extern "C" fn update_donor(wp: *mut WalProposer, donor: *mut Safekeeper, donor_lsn: XLogRecPtr) {
+    unsafe {
+        let callback_data = (*(*wp).config).callback_data;
+        let api = callback_data as *mut Box<dyn ApiImpl>;
+        (*api).update_donor(&mut (*donor), donor_lsn)
+    }
+}
+
 extern "C" fn get_current_timestamp(wp: *mut WalProposer) -> TimestampTz {
    unsafe {
        let callback_data = (*(*wp).config).callback_data;
@@ -391,6 +399,7 @@ pub(crate) fn create_api() -> walproposer_api {
        get_shmem_state: Some(get_shmem_state),
        start_streaming: Some(start_streaming),
        get_flush_rec_ptr: Some(get_flush_rec_ptr),
+        update_donor: Some(update_donor),
        get_current_timestamp: Some(get_current_timestamp),
        conn_error_message: Some(conn_error_message),
        conn_status: Some(conn_status),
@@ -421,6 +430,32 @@ pub(crate) fn create_api() -> walproposer_api {
    }
 }

+pub fn empty_shmem() -> crate::bindings::WalproposerShmemState {
+    let empty_feedback = crate::bindings::PageserverFeedback {
+        present: false,
+        currentClusterSize: 0,
+        last_received_lsn: 0,
+        disk_consistent_lsn: 0,
+        remote_consistent_lsn: 0,
+        replytime: 0,
+        shard_number: 0,
+    };
+
+    crate::bindings::WalproposerShmemState {
+        propEpochStartLsn: crate::bindings::pg_atomic_uint64 { value: 0 },
+        donor_name: [0; 64],
+        donor_conninfo: [0; 1024],
+        donor_lsn: 0,
+        mutex: 0,
+        mineLastElectedTerm: crate::bindings::pg_atomic_uint64 { value: 0 },
+        backpressureThrottlingTime: crate::bindings::pg_atomic_uint64 { value: 0 },
+        currentClusterSize: crate::bindings::pg_atomic_uint64 { value: 0 },
+        shard_ps_feedback: [empty_feedback; 128],
+        num_shards: 0,
+        min_ps_feedback: empty_feedback,
+    }
+}
+
 impl std::fmt::Display for Level {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        write!(f, "{:?}", self)
--- a/libs/walproposer/src/walproposer.rs
+++ b/libs/walproposer/src/walproposer.rs
@@ -1,8 +1,5 @@
 use std::ffi::CString;

-use postgres_ffi::WAL_SEGMENT_SIZE;
-use utils::{id::TenantTimelineId, lsn::Lsn};
-
 use crate::{
    api_bindings::{create_api, take_vec_u8, Level},
    bindings::{
@@ -10,6 +7,8 @@ use crate::{
        WalProposerCreate, WalProposerFree, WalProposerPoll, WalProposerStart,
    },
 };
+use postgres_ffi::WAL_SEGMENT_SIZE;
+use utils::{id::TenantTimelineId, lsn::Lsn};

 /// Rust high-level wrapper for C walproposer API. Many methods are not required
 /// for simple cases, hence todo!() in default implementations.
@@ -28,6 +27,10 @@ pub trait ApiImpl {
        todo!()
    }

+    fn update_donor(&self, _donor: &mut Safekeeper, _donor_lsn: u64) {
+        todo!()
+    }
+
    fn get_current_timestamp(&self) -> i64 {
        todo!()
    }
@@ -274,6 +277,7 @@ mod tests {
        sync::{atomic::AtomicUsize, mpsc::sync_channel},
    };

+    use std::cell::UnsafeCell;
    use utils::id::TenantTimelineId;

    use crate::{api_bindings::Level, bindings::NeonWALReadResult, walproposer::Wrapper};
@@ -297,6 +301,8 @@ mod tests {
        replies_ptr: AtomicUsize,
        // channel to send LSN to the main thread
        sync_channel: std::sync::mpsc::SyncSender<u64>,
+        // Shmem state, used for storing donor info
+        shmem: UnsafeCell<crate::bindings::WalproposerShmemState>,
    }

    impl MockImpl {
@@ -327,11 +333,22 @@ mod tests {
    }

    impl ApiImpl for MockImpl {
+        fn get_shmem_state(&self) -> *mut crate::bindings::WalproposerShmemState {
+            self.shmem.get()
+        }
+
        fn get_current_timestamp(&self) -> i64 {
            println!("get_current_timestamp");
            0
        }

+        fn update_donor(&self, donor: &mut crate::bindings::Safekeeper, donor_lsn: u64) {
+            let mut shmem = unsafe { *self.get_shmem_state() };
+            shmem.propEpochStartLsn.value = donor_lsn;
+            shmem.donor_conninfo = donor.conninfo;
+            shmem.donor_lsn = donor_lsn;
+        }
+
        fn conn_status(
            &self,
            _: &mut crate::bindings::Safekeeper,
@@ -507,6 +524,7 @@ mod tests {
            ],
            replies_ptr: AtomicUsize::new(0),
            sync_channel: sender,
+            shmem: UnsafeCell::new(crate::api_bindings::empty_shmem()),
        });
        let config = crate::walproposer::Config {
            ttid,
--- a/pageserver/benches/bench_layer_map.rs
+++ b/pageserver/benches/bench_layer_map.rs
@@ -1,7 +1,7 @@
 use pageserver::keyspace::{KeyPartitioning, KeySpace};
 use pageserver::repository::Key;
 use pageserver::tenant::layer_map::LayerMap;
-use pageserver::tenant::storage_layer::LayerFileName;
+use pageserver::tenant::storage_layer::LayerName;
 use pageserver::tenant::storage_layer::PersistentLayerDesc;
 use pageserver_api::shard::TenantShardId;
 use rand::prelude::{SeedableRng, SliceRandom, StdRng};
@@ -28,7 +28,7 @@ fn build_layer_map(filename_dump: PathBuf) -> LayerMap {
    let mut updates = layer_map.batch_update();
    for fname in filenames {
        let fname = fname.unwrap();
-        let fname = LayerFileName::from_str(&fname).unwrap();
+        let fname = LayerName::from_str(&fname).unwrap();
        let layer = PersistentLayerDesc::from(fname);

        let lsn_range = layer.get_lsn_range();
--- a/pageserver/client/src/mgmt_api.rs
+++ b/pageserver/client/src/mgmt_api.rs
@@ -284,6 +284,34 @@ impl Client {
        Ok((status, progress))
    }

+    pub async fn tenant_secondary_status(
+        &self,
+        tenant_shard_id: TenantShardId,
+    ) -> Result<SecondaryProgress> {
+        let path = reqwest::Url::parse(&format!(
+            "{}/v1/tenant/{}/secondary/status",
+            self.mgmt_api_endpoint, tenant_shard_id
+        ))
+        .expect("Cannot build URL");
+
+        self.request(Method::GET, path, ())
+            .await?
+            .json()
+            .await
+            .map_err(Error::ReceiveBody)
+    }
+
+    pub async fn tenant_heatmap_upload(&self, tenant_id: TenantShardId) -> Result<()> {
+        let path = reqwest::Url::parse(&format!(
+            "{}/v1/tenant/{}/heatmap_upload",
+            self.mgmt_api_endpoint, tenant_id
+        ))
+        .expect("Cannot build URL");
+
+        self.request(Method::POST, path, ()).await?;
+        Ok(())
+    }
+
    pub async fn location_config(
        &self,
        tenant_shard_id: TenantShardId,
@@ -291,10 +319,7 @@ impl Client {
        flush_ms: Option<std::time::Duration>,
        lazy: bool,
    ) -> Result<()> {
-        let req_body = TenantLocationConfigRequest {
-            tenant_id: None,
-            config,
-        };
+        let req_body = TenantLocationConfigRequest { config };

        let mut path = reqwest::Url::parse(&format!(
            "{}/v1/tenant/{}/location_config",
--- a/pageserver/compaction/src/compact_tiered.rs
+++ b/pageserver/compaction/src/compact_tiered.rs
@@ -24,7 +24,9 @@ use tracing::{debug, info};
 use std::collections::{HashSet, VecDeque};
 use std::ops::Range;

-use crate::helpers::{accum_key_values, keyspace_total_size, merge_delta_keys, overlaps_with};
+use crate::helpers::{
+    accum_key_values, keyspace_total_size, merge_delta_keys_buffered, overlaps_with,
+};
 use crate::interface::*;
 use utils::lsn::Lsn;

@@ -104,7 +106,13 @@ pub async fn compact_tiered<E: CompactionJobExecutor>(
            ctx,
        )
        .await?;
-        if target_file_size == u64::MAX {
+        if current_level_target_height == u64::MAX {
+            // our target height includes all possible lsns
+            info!(
+                level = current_level_no,
+                depth = depth,
+                "compaction loop reached max current_level_target_height"
+            );
            break;
        }
        current_level_no += 1;
@@ -535,7 +543,10 @@ where
            }
        }
        // Open stream
-        let key_value_stream = std::pin::pin!(merge_delta_keys::<E>(deltas.as_slice(), ctx));
+        let key_value_stream =
+            std::pin::pin!(merge_delta_keys_buffered::<E>(deltas.as_slice(), ctx)
+                .await?
+                .map(Result::<_, anyhow::Error>::Ok));
        let mut new_jobs = Vec::new();

        // Slide a window through the keyspace
--- a/pageserver/compaction/src/helpers.rs
+++ b/pageserver/compaction/src/helpers.rs
@@ -9,10 +9,12 @@ use pageserver_api::shard::ShardIdentity;
 use pin_project_lite::pin_project;
 use std::collections::BinaryHeap;
 use std::collections::VecDeque;
+use std::fmt::Display;
 use std::future::Future;
 use std::ops::{DerefMut, Range};
 use std::pin::Pin;
 use std::task::{ready, Poll};
+use utils::lsn::Lsn;

 pub fn keyspace_total_size<K>(
    keyspace: &CompactionKeySpace<K>,
@@ -108,17 +110,40 @@ pub fn merge_delta_keys<'a, E: CompactionJobExecutor>(
    }
 }

+pub async fn merge_delta_keys_buffered<'a, E: CompactionJobExecutor + 'a>(
+    layers: &'a [E::DeltaLayer],
+    ctx: &'a E::RequestContext,
+) -> anyhow::Result<impl Stream<Item = <E::DeltaLayer as CompactionDeltaLayer<E>>::DeltaEntry<'a>>>
+{
+    let mut keys = Vec::new();
+    for l in layers {
+        // Boxing and casting to LoadFuture is required to obtain the right Sync bound.
+        // If we do l.load_keys(ctx).await? directly, there is a compilation error.
+        let load_future: LoadFuture<'a, _> = Box::pin(l.load_keys(ctx));
+        keys.extend(load_future.await?.into_iter());
+    }
+    keys.sort_by_key(|k| (k.key(), k.lsn()));
+    let stream = futures::stream::iter(keys.into_iter());
+    Ok(stream)
+}
+
 enum LazyLoadLayer<'a, E: CompactionJobExecutor> {
    Loaded(VecDeque<<E::DeltaLayer as CompactionDeltaLayer<E>>::DeltaEntry<'a>>),
    Unloaded(&'a E::DeltaLayer),
 }
 impl<'a, E: CompactionJobExecutor> LazyLoadLayer<'a, E> {
-    fn key(&self) -> E::Key {
+    fn min_key(&self) -> E::Key {
        match self {
            Self::Loaded(entries) => entries.front().unwrap().key(),
            Self::Unloaded(dl) => dl.key_range().start,
        }
    }
+    fn min_lsn(&self) -> Lsn {
+        match self {
+            Self::Loaded(entries) => entries.front().unwrap().lsn(),
+            Self::Unloaded(dl) => dl.lsn_range().start,
+        }
+    }
 }
 impl<'a, E: CompactionJobExecutor> PartialOrd for LazyLoadLayer<'a, E> {
    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
@@ -128,12 +153,12 @@ impl<'a, E: CompactionJobExecutor> PartialOrd for LazyLoadLayer<'a, E> {
 impl<'a, E: CompactionJobExecutor> Ord for LazyLoadLayer<'a, E> {
    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
        // reverse order so that we get a min-heap
-        other.key().cmp(&self.key())
+        (other.min_key(), other.min_lsn()).cmp(&(self.min_key(), self.min_lsn()))
    }
 }
 impl<'a, E: CompactionJobExecutor> PartialEq for LazyLoadLayer<'a, E> {
    fn eq(&self, other: &Self) -> bool {
-        self.key().eq(&other.key())
+        self.cmp(other) == std::cmp::Ordering::Equal
    }
 }
 impl<'a, E: CompactionJobExecutor> Eq for LazyLoadLayer<'a, E> {}
@@ -214,7 +239,7 @@ pub struct KeySize<K> {

 pub fn accum_key_values<'a, I, K, D, E>(input: I) -> impl Stream<Item = Result<KeySize<K>, E>>
 where
-    K: Eq,
+    K: Eq + PartialOrd + Display + Copy,
    I: Stream<Item = Result<D, E>>,
    D: CompactionDeltaEntry<'a, K>,
 {
@@ -229,12 +254,15 @@ where
                num_values: 1,
                size: first.size(),
            };
+            let mut last_key = accum.key;
            while let Some(this) = input.next().await {
                let this = this?;
                if this.key() == accum.key {
                    accum.size += this.size();
                    accum.num_values += 1;
                } else {
+                    assert!(last_key <= accum.key, "last_key={last_key} <= accum.key={}", accum.key);
+                    last_key = accum.key;
                    yield accum;
                    accum = KeySize {
                        key: this.key(),
@@ -243,6 +271,7 @@ where
                    };
                }
            }
+            assert!(last_key <= accum.key, "last_key={last_key} <= accum.key={}", accum.key);
            yield accum;
        }
    }
--- a/pageserver/compaction/tests/tests.rs
+++ b/pageserver/compaction/tests/tests.rs
@@ -1,5 +1,20 @@
+use once_cell::sync::OnceCell;
 use pageserver_compaction::interface::CompactionLayer;
 use pageserver_compaction::simulator::MockTimeline;
+use utils::logging;
+
+static LOG_HANDLE: OnceCell<()> = OnceCell::new();
+
+pub(crate) fn setup_logging() {
+    LOG_HANDLE.get_or_init(|| {
+        logging::init(
+            logging::LogFormat::Test,
+            logging::TracingErrorLayerEnablement::EnableWithRustLogFilter,
+            logging::Output::Stdout,
+        )
+        .expect("Failed to init test logging")
+    });
+}

 /// Test the extreme case that there are so many updates for a single key that
 /// even if we produce an extremely narrow delta layer, spanning just that one
@@ -11,13 +26,14 @@ use pageserver_compaction::simulator::MockTimeline;
 #[ignore]
 #[tokio::test]
 async fn test_many_updates_for_single_key() {
+    setup_logging();
    let mut executor = MockTimeline::new();
-    executor.target_file_size = 10_000_000; // 10 MB
+    executor.target_file_size = 1_000_000; // 1 MB

-    // Ingest 100 MB of updates to a single key.
+    // Ingest 10 MB of updates to a single key.
    for _ in 1..1000 {
        executor.ingest_uniform(100, 10, &(0..100_000)).unwrap();
-        executor.ingest_uniform(10_000, 10, &(0..1)).unwrap();
+        executor.ingest_uniform(1000, 10, &(0..1)).unwrap();
        executor.compact().await.unwrap();
    }

@@ -33,3 +49,26 @@ async fn test_many_updates_for_single_key() {
        }
    }
 }
+
+#[tokio::test]
+async fn test_simple_updates() {
+    setup_logging();
+    let mut executor = MockTimeline::new();
+    executor.target_file_size = 500_000; // 500 KB
+
+    // Ingest some traffic.
+    for _ in 1..400 {
+        executor.ingest_uniform(100, 500, &(0..100_000)).unwrap();
+    }
+
+    for l in executor.live_layers.iter() {
+        println!("layer {}: {}", l.short_id(), l.file_size());
+    }
+
+    println!("Running compaction...");
+    executor.compact().await.unwrap();
+
+    for l in executor.live_layers.iter() {
+        println!("layer {}: {}", l.short_id(), l.file_size());
+    }
+}
--- a/pageserver/ctl/src/draw_timeline_dir.rs
+++ b/pageserver/ctl/src/draw_timeline_dir.rs
@@ -28,6 +28,8 @@
 //! # From an `index_part.json` in S3
 //! (jq -r '.layer_metadata | keys[]' | cargo  run -p pagectl draw-timeline ) < index_part.json-00000016 > out.svg
 //!
+//! # enrich with lines for gc_cutoff and a child branch point
+//! cat <(jq -r '.historic_layers[] | .layer_file_name' < layers.json) <(echo -e 'gc_cutoff:0000001CE3FE32C9\nbranch:0000001DE3FE32C9') | cargo run --bin pagectl draw-timeline >| out.svg
 //! ```
 //!
 //! ## Viewing
@@ -48,7 +50,7 @@
 //! ```
 //!

-use anyhow::Result;
+use anyhow::{Context, Result};
 use pageserver::repository::Key;
 use pageserver::METADATA_FILE_NAME;
 use std::cmp::Ordering;
@@ -90,6 +92,33 @@ fn parse_filename(name: &str) -> (Range<Key>, Range<Lsn>) {
    (keys, lsns)
 }

+#[derive(Clone, Copy)]
+enum LineKind {
+    GcCutoff,
+    Branch,
+}
+
+impl From<LineKind> for Fill {
+    fn from(value: LineKind) -> Self {
+        match value {
+            LineKind::GcCutoff => Fill::Color(rgb(255, 0, 0)),
+            LineKind::Branch => Fill::Color(rgb(0, 255, 0)),
+        }
+    }
+}
+
+impl FromStr for LineKind {
+    type Err = anyhow::Error;
+
+    fn from_str(s: &str) -> std::prelude::v1::Result<Self, Self::Err> {
+        Ok(match s {
+            "gc_cutoff" => LineKind::GcCutoff,
+            "branch" => LineKind::Branch,
+            _ => anyhow::bail!("unsupported linekind: {s}"),
+        })
+    }
+}
+
 pub fn main() -> Result<()> {
    // Parse layer filenames from stdin
    struct Layer {
@@ -99,8 +128,29 @@ pub fn main() -> Result<()> {
    }
    let mut files: Vec<Layer> = vec![];
    let stdin = io::stdin();
-    for line in stdin.lock().lines() {
+
+    let mut lines: Vec<(Lsn, LineKind)> = vec![];
+
+    for (lineno, line) in stdin.lock().lines().enumerate() {
+        let lineno = lineno + 1;
+
        let line = line.unwrap();
+        if let Some((kind, lsn)) = line.split_once(':') {
+            let (kind, lsn) = LineKind::from_str(kind)
+                .context("parse kind")
+                .and_then(|kind| {
+                    if lsn.contains('/') {
+                        Lsn::from_str(lsn)
+                    } else {
+                        Lsn::from_hex(lsn)
+                    }
+                    .map(|lsn| (kind, lsn))
+                    .context("parse lsn")
+                })
+                .with_context(|| format!("parse {line:?} on {lineno}"))?;
+            lines.push((lsn, kind));
+            continue;
+        }
        let line = PathBuf::from_str(&line).unwrap();
        let filename = line.file_name().unwrap();
        let filename = filename.to_str().unwrap();
@@ -117,8 +167,9 @@ pub fn main() -> Result<()> {
    }

    // Collect all coordinates
-    let mut keys: Vec<Key> = vec![];
-    let mut lsns: Vec<Lsn> = vec![];
+    let mut keys: Vec<Key> = Vec::with_capacity(files.len());
+    let mut lsns: Vec<Lsn> = Vec::with_capacity(files.len() + lines.len());
+
    for Layer {
        key_range: keyr,
        lsn_range: lsnr,
@@ -131,6 +182,8 @@ pub fn main() -> Result<()> {
        lsns.push(lsnr.end);
    }

+    lsns.extend(lines.iter().map(|(lsn, _)| *lsn));
+
    // Analyze
    let key_map = build_coordinate_compression_map(keys);
    let lsn_map = build_coordinate_compression_map(lsns);
@@ -144,10 +197,13 @@ pub fn main() -> Result<()> {
    println!(
        "{}",
        BeginSvg {
-            w: key_map.len() as f32,
+            w: (key_map.len() + 10) as f32,
            h: stretch * lsn_map.len() as f32
        }
    );
+
+    let xmargin = 0.05; // Height-dependent margin to disambiguate overlapping deltas
+
    for Layer {
        filename,
        key_range: keyr,
@@ -169,7 +225,6 @@ pub fn main() -> Result<()> {
        let mut lsn_diff = (lsn_end - lsn_start) as f32;
        let mut fill = Fill::None;
        let mut ymargin = 0.05 * lsn_diff; // Height-dependent margin to disambiguate overlapping deltas
-        let xmargin = 0.05; // Height-dependent margin to disambiguate overlapping deltas
        let mut lsn_offset = 0.0;

        // Fill in and thicken rectangle if it's an
@@ -189,7 +244,7 @@ pub fn main() -> Result<()> {
        println!(
            "    {}",
            rectangle(
-                key_start as f32 + stretch * xmargin,
+                5.0 + key_start as f32 + stretch * xmargin,
                stretch * (lsn_max as f32 - (lsn_end as f32 - ymargin - lsn_offset)),
                key_diff as f32 - stretch * 2.0 * xmargin,
                stretch * (lsn_diff - 2.0 * ymargin)
@@ -200,6 +255,26 @@ pub fn main() -> Result<()> {
            .comment(filename)
        );
    }
+
+    for (lsn, kind) in lines {
+        let lsn_start = *lsn_map.get(&lsn).unwrap();
+        let lsn_end = lsn_start;
+        let stretch = 2.0;
+        let lsn_diff = 0.3;
+        let lsn_offset = -lsn_diff / 2.0;
+        let ymargin = 0.05;
+        println!(
+            "{}",
+            rectangle(
+                0.0f32 + stretch * xmargin,
+                stretch * (lsn_map.len() as f32 - (lsn_end as f32 - ymargin - lsn_offset)),
+                (key_map.len() + 10) as f32,
+                stretch * (lsn_diff - 2.0 * ymargin)
+            )
+            .fill(kind)
+        );
+    }
+
    println!("{}", EndSvg);

    eprintln!("num_images: {}", num_images);
--- a/pageserver/ctl/src/index_part.rs
+++ b/pageserver/ctl/src/index_part.rs
@@ -3,7 +3,7 @@ use std::collections::HashMap;
 use anyhow::Context;
 use camino::Utf8PathBuf;
 use pageserver::tenant::remote_timeline_client::index::IndexLayerMetadata;
-use pageserver::tenant::storage_layer::LayerFileName;
+use pageserver::tenant::storage_layer::LayerName;
 use pageserver::tenant::{metadata::TimelineMetadata, IndexPart};
 use utils::lsn::Lsn;

@@ -19,7 +19,7 @@ pub(crate) async fn main(cmd: &IndexPartCmd) -> anyhow::Result<()> {
            let des: IndexPart = IndexPart::from_s3_bytes(&bytes).context("deserialize")?;
            #[derive(serde::Serialize)]
            struct Output<'a> {
-                layer_metadata: &'a HashMap<LayerFileName, IndexLayerMetadata>,
+                layer_metadata: &'a HashMap<LayerName, IndexLayerMetadata>,
                disk_consistent_lsn: Lsn,
                timeline_metadata: &'a TimelineMetadata,
            }
--- a/pageserver/ctl/src/layer_map_analyzer.rs
+++ b/pageserver/ctl/src/layer_map_analyzer.rs
@@ -100,7 +100,7 @@ pub(crate) fn parse_filename(name: &str) -> Option<LayerFile> {

 // Finds the max_holes largest holes, ignoring any that are smaller than MIN_HOLE_LENGTH"
 async fn get_holes(path: &Utf8Path, max_holes: usize, ctx: &RequestContext) -> Result<Vec<Hole>> {
-    let file = VirtualFile::open(path).await?;
+    let file = VirtualFile::open(path, ctx).await?;
    let file_id = page_cache::next_file_id();
    let block_reader = FileBlockReader::new(&file, file_id);
    let summary_blk = block_reader.read_blk(0, ctx).await?;
--- a/pageserver/ctl/src/layers.rs
+++ b/pageserver/ctl/src/layers.rs
@@ -61,7 +61,7 @@ async fn read_delta_file(path: impl AsRef<Path>, ctx: &RequestContext) -> Result
    let path = Utf8Path::from_path(path.as_ref()).expect("non-Unicode path");
    virtual_file::init(10, virtual_file::api::IoEngineKind::StdFs);
    page_cache::init(100);
-    let file = VirtualFile::open(path).await?;
+    let file = VirtualFile::open(path, ctx).await?;
    let file_id = page_cache::next_file_id();
    let block_reader = FileBlockReader::new(&file, file_id);
    let summary_blk = block_reader.read_blk(0, ctx).await?;
--- a/pageserver/src/aux_file.rs
+++ b/pageserver/src/aux_file.rs
@@ -1,3 +1,4 @@
+use bytes::{Buf, BufMut, Bytes};
 use pageserver_api::key::{Key, AUX_KEY_PREFIX, METADATA_KEY_SIZE};
 use tracing::warn;

@@ -61,6 +62,84 @@ pub fn encode_aux_file_key(path: &str) -> Key {
    }
 }

+const AUX_FILE_ENCODING_VERSION: u8 = 0x01;
+
+pub fn decode_file_value(val: &[u8]) -> anyhow::Result<Vec<(&str, &[u8])>> {
+    let mut ptr = val;
+    if ptr.is_empty() {
+        // empty value = no files
+        return Ok(Vec::new());
+    }
+    assert_eq!(
+        ptr.get_u8(),
+        AUX_FILE_ENCODING_VERSION,
+        "unsupported aux file value"
+    );
+    let mut files = vec![];
+    while ptr.has_remaining() {
+        let key_len = ptr.get_u32() as usize;
+        let key = &ptr[..key_len];
+        ptr.advance(key_len);
+        let val_len = ptr.get_u32() as usize;
+        let content = &ptr[..val_len];
+        ptr.advance(val_len);
+
+        let path = std::str::from_utf8(key)?;
+        files.push((path, content));
+    }
+    Ok(files)
+}
+
+/// Decode an aux file key-value pair into a list of files. The returned `Bytes` contains reference
+/// to the original value slice. Be cautious about memory consumption.
+pub fn decode_file_value_bytes(val: &Bytes) -> anyhow::Result<Vec<(String, Bytes)>> {
+    let mut ptr = val.clone();
+    if ptr.is_empty() {
+        // empty value = no files
+        return Ok(Vec::new());
+    }
+    assert_eq!(
+        ptr.get_u8(),
+        AUX_FILE_ENCODING_VERSION,
+        "unsupported aux file value"
+    );
+    let mut files = vec![];
+    while ptr.has_remaining() {
+        let key_len = ptr.get_u32() as usize;
+        let key = ptr.slice(..key_len);
+        ptr.advance(key_len);
+        let val_len = ptr.get_u32() as usize;
+        let content = ptr.slice(..val_len);
+        ptr.advance(val_len);
+
+        let path = std::str::from_utf8(&key)?.to_string();
+        files.push((path, content));
+    }
+    Ok(files)
+}
+
+pub fn encode_file_value(files: &[(&str, &[u8])]) -> anyhow::Result<Vec<u8>> {
+    if files.is_empty() {
+        // no files = empty value
+        return Ok(Vec::new());
+    }
+    let mut encoded = vec![];
+    encoded.put_u8(AUX_FILE_ENCODING_VERSION);
+    for (path, content) in files {
+        if path.len() > u32::MAX as usize {
+            anyhow::bail!("{} exceeds path size limit", path);
+        }
+        encoded.put_u32(path.len() as u32);
+        encoded.put_slice(path.as_bytes());
+        if content.len() > u32::MAX as usize {
+            anyhow::bail!("{} exceeds content size limit", path);
+        }
+        encoded.put_u32(content.len() as u32);
+        encoded.put_slice(content);
+    }
+    Ok(encoded)
+}
+
 #[cfg(test)]
 mod tests {
    use super::*;
@@ -109,4 +188,21 @@ mod tests {
            encode_aux_file_key("other_file_not_supported").to_string()
        );
    }
+
+    #[test]
+    fn test_value_encoding() {
+        let files = vec![
+            ("pg_logical/1.file", "1111".as_bytes()),
+            ("pg_logical/2.file", "2222".as_bytes()),
+        ];
+        assert_eq!(
+            files,
+            decode_file_value(&encode_file_value(&files).unwrap()).unwrap()
+        );
+        let files = vec![];
+        assert_eq!(
+            files,
+            decode_file_value(&encode_file_value(&files).unwrap()).unwrap()
+        );
+    }
 }
--- a/pageserver/src/basebackup.rs
+++ b/pageserver/src/basebackup.rs
@@ -10,7 +10,7 @@
 //! This module is responsible for creation of such tarball
 //! from data stored in object storage.
 //!
-use anyhow::{anyhow, bail, ensure, Context};
+use anyhow::{anyhow, Context};
 use bytes::{BufMut, Bytes, BytesMut};
 use fail::fail_point;
 use pageserver_api::key::{key_to_slru_block, Key};
@@ -38,6 +38,14 @@ use postgres_ffi::PG_TLI;
 use postgres_ffi::{BLCKSZ, RELSEG_SIZE, WAL_SEGMENT_SIZE};
 use utils::lsn::Lsn;

+#[derive(Debug, thiserror::Error)]
+pub enum BasebackupError {
+    #[error("basebackup pageserver error {0:#}")]
+    Server(#[from] anyhow::Error),
+    #[error("basebackup client error {0:#}")]
+    Client(#[source] io::Error),
+}
+
 /// Create basebackup with non-rel data in it.
 /// Only include relational data if 'full_backup' is true.
 ///
@@ -53,7 +61,7 @@ pub async fn send_basebackup_tarball<'a, W>(
    prev_lsn: Option<Lsn>,
    full_backup: bool,
    ctx: &'a RequestContext,
-) -> anyhow::Result<()>
+) -> Result<(), BasebackupError>
 where
    W: AsyncWrite + Send + Sync + Unpin,
 {
@@ -92,8 +100,10 @@ where

    // Consolidate the derived and the provided prev_lsn values
    let prev_lsn = if let Some(provided_prev_lsn) = prev_lsn {
-        if backup_prev != Lsn(0) {
-            ensure!(backup_prev == provided_prev_lsn);
+        if backup_prev != Lsn(0) && backup_prev != provided_prev_lsn {
+            return Err(BasebackupError::Server(anyhow!(
+                "backup_prev {backup_prev} != provided_prev_lsn {provided_prev_lsn}"
+            )));
        }
        provided_prev_lsn
    } else {
@@ -159,15 +169,26 @@ where
        }
    }

-    async fn add_block(&mut self, key: &Key, block: Bytes) -> anyhow::Result<()> {
+    async fn add_block(&mut self, key: &Key, block: Bytes) -> Result<(), BasebackupError> {
        let (kind, segno, _) = key_to_slru_block(*key)?;

        match kind {
            SlruKind::Clog => {
-                ensure!(block.len() == BLCKSZ as usize || block.len() == BLCKSZ as usize + 8);
+                if !(block.len() == BLCKSZ as usize || block.len() == BLCKSZ as usize + 8) {
+                    return Err(BasebackupError::Server(anyhow!(
+                        "invalid SlruKind::Clog record: block.len()={}",
+                        block.len()
+                    )));
+                }
            }
            SlruKind::MultiXactMembers | SlruKind::MultiXactOffsets => {
-                ensure!(block.len() == BLCKSZ as usize);
+                if block.len() != BLCKSZ as usize {
+                    return Err(BasebackupError::Server(anyhow!(
+                        "invalid {:?} record: block.len()={}",
+                        kind,
+                        block.len()
+                    )));
+                }
            }
        }

@@ -194,12 +215,15 @@ where
        Ok(())
    }

-    async fn flush(&mut self) -> anyhow::Result<()> {
+    async fn flush(&mut self) -> Result<(), BasebackupError> {
        let nblocks = self.buf.len() / BLCKSZ as usize;
        let (kind, segno) = self.current_segment.take().unwrap();
        let segname = format!("{}/{:>04X}", kind.to_str(), segno);
        let header = new_tar_header(&segname, self.buf.len() as u64)?;
-        self.ar.append(&header, self.buf.as_slice()).await?;
+        self.ar
+            .append(&header, self.buf.as_slice())
+            .await
+            .map_err(BasebackupError::Client)?;

        self.total_blocks += nblocks;
        debug!("Added to basebackup slru {} relsize {}", segname, nblocks);
@@ -209,7 +233,7 @@ where
        Ok(())
    }

-    async fn finish(mut self) -> anyhow::Result<()> {
+    async fn finish(mut self) -> Result<(), BasebackupError> {
        let res = if self.current_segment.is_none() || self.buf.is_empty() {
            Ok(())
        } else {
@@ -226,7 +250,7 @@ impl<'a, W> Basebackup<'a, W>
 where
    W: AsyncWrite + Send + Sync + Unpin,
 {
-    async fn send_tarball(mut self) -> anyhow::Result<()> {
+    async fn send_tarball(mut self) -> Result<(), BasebackupError> {
        // TODO include checksum

        let lazy_slru_download = self.timeline.get_lazy_slru_download() && !self.full_backup;
@@ -262,7 +286,8 @@ where
            let slru_partitions = self
                .timeline
                .get_slru_keyspace(Version::Lsn(self.lsn), self.ctx)
-                .await?
+                .await
+                .map_err(|e| BasebackupError::Server(e.into()))?
                .partition(
                    self.timeline.get_shard_identity(),
                    Timeline::MAX_GET_VECTORED_KEYS * BLCKSZ as u64,
@@ -271,10 +296,15 @@ where
            let mut slru_builder = SlruSegmentsBuilder::new(&mut self.ar);

            for part in slru_partitions.parts {
-                let blocks = self.timeline.get_vectored(part, self.lsn, self.ctx).await?;
+                let blocks = self
+                    .timeline
+                    .get_vectored(part, self.lsn, self.ctx)
+                    .await
+                    .map_err(|e| BasebackupError::Server(e.into()))?;

                for (key, block) in blocks {
-                    slru_builder.add_block(&key, block?).await?;
+                    let block = block.map_err(|e| BasebackupError::Server(e.into()))?;
+                    slru_builder.add_block(&key, block).await?;
                }
            }
            slru_builder.finish().await?;
@@ -282,8 +312,11 @@ where

        let mut min_restart_lsn: Lsn = Lsn::MAX;
        // Create tablespace directories
-        for ((spcnode, dbnode), has_relmap_file) in
-            self.timeline.list_dbdirs(self.lsn, self.ctx).await?
+        for ((spcnode, dbnode), has_relmap_file) in self
+            .timeline
+            .list_dbdirs(self.lsn, self.ctx)
+            .await
+            .map_err(|e| BasebackupError::Server(e.into()))?
        {
            self.add_dbdir(spcnode, dbnode, has_relmap_file).await?;

@@ -292,7 +325,8 @@ where
            let rels = self
                .timeline
                .list_rels(spcnode, dbnode, Version::Lsn(self.lsn), self.ctx)
-                .await?;
+                .await
+                .map_err(|e| BasebackupError::Server(e.into()))?;
            for &rel in rels.iter() {
                // Send init fork as main fork to provide well formed empty
                // contents of UNLOGGED relations. Postgres copies it in
@@ -315,7 +349,12 @@ where
                }
            }

-            for (path, content) in self.timeline.list_aux_files(self.lsn, self.ctx).await? {
+            for (path, content) in self
+                .timeline
+                .list_aux_files(self.lsn, self.ctx)
+                .await
+                .map_err(|e| BasebackupError::Server(e.into()))?
+            {
                if path.starts_with("pg_replslot") {
                    let offs = pg_constants::REPL_SLOT_ON_DISK_OFFSETOF_RESTART_LSN;
                    let restart_lsn = Lsn(u64::from_le_bytes(
@@ -346,34 +385,41 @@ where
        for xid in self
            .timeline
            .list_twophase_files(self.lsn, self.ctx)
-            .await?
+            .await
+            .map_err(|e| BasebackupError::Server(e.into()))?
        {
            self.add_twophase_file(xid).await?;
        }

        fail_point!("basebackup-before-control-file", |_| {
-            bail!("failpoint basebackup-before-control-file")
+            Err(BasebackupError::Server(anyhow!(
+                "failpoint basebackup-before-control-file"
+            )))
        });

        // Generate pg_control and bootstrap WAL segment.
        self.add_pgcontrol_file().await?;
-        self.ar.finish().await?;
+        self.ar.finish().await.map_err(BasebackupError::Client)?;
        debug!("all tarred up!");
        Ok(())
    }

    /// Add contents of relfilenode `src`, naming it as `dst`.
-    async fn add_rel(&mut self, src: RelTag, dst: RelTag) -> anyhow::Result<()> {
+    async fn add_rel(&mut self, src: RelTag, dst: RelTag) -> Result<(), BasebackupError> {
        let nblocks = self
            .timeline
            .get_rel_size(src, Version::Lsn(self.lsn), self.ctx)
-            .await?;
+            .await
+            .map_err(|e| BasebackupError::Server(e.into()))?;

        // If the relation is empty, create an empty file
        if nblocks == 0 {
            let file_name = dst.to_segfile_name(0);
            let header = new_tar_header(&file_name, 0)?;
-            self.ar.append(&header, &mut io::empty()).await?;
+            self.ar
+                .append(&header, &mut io::empty())
+                .await
+                .map_err(BasebackupError::Client)?;
            return Ok(());
        }

@@ -388,13 +434,17 @@ where
                let img = self
                    .timeline
                    .get_rel_page_at_lsn(src, blknum, Version::Lsn(self.lsn), self.ctx)
-                    .await?;
+                    .await
+                    .map_err(|e| BasebackupError::Server(e.into()))?;
                segment_data.extend_from_slice(&img[..]);
            }

            let file_name = dst.to_segfile_name(seg as u32);
            let header = new_tar_header(&file_name, segment_data.len() as u64)?;
-            self.ar.append(&header, segment_data.as_slice()).await?;
+            self.ar
+                .append(&header, segment_data.as_slice())
+                .await
+                .map_err(BasebackupError::Client)?;

            seg += 1;
            startblk = endblk;
@@ -414,20 +464,22 @@ where
        spcnode: u32,
        dbnode: u32,
        has_relmap_file: bool,
-    ) -> anyhow::Result<()> {
+    ) -> Result<(), BasebackupError> {
        let relmap_img = if has_relmap_file {
            let img = self
                .timeline
                .get_relmap_file(spcnode, dbnode, Version::Lsn(self.lsn), self.ctx)
-                .await?;
+                .await
+                .map_err(|e| BasebackupError::Server(e.into()))?;

-            ensure!(
-                img.len()
-                    == dispatch_pgversion!(
-                        self.timeline.pg_version,
-                        pgv::bindings::SIZEOF_RELMAPFILE
-                    )
-            );
+            if img.len()
+                != dispatch_pgversion!(self.timeline.pg_version, pgv::bindings::SIZEOF_RELMAPFILE)
+            {
+                return Err(BasebackupError::Server(anyhow!(
+                    "img.len() != SIZE_OF_RELMAPFILE, img.len()={}",
+                    img.len(),
+                )));
+            }

            Some(img)
        } else {
@@ -440,14 +492,20 @@ where
                ver => format!("{ver}\x0A"),
            };
            let header = new_tar_header("PG_VERSION", pg_version_str.len() as u64)?;
-            self.ar.append(&header, pg_version_str.as_bytes()).await?;
+            self.ar
+                .append(&header, pg_version_str.as_bytes())
+                .await
+                .map_err(BasebackupError::Client)?;

            info!("timeline.pg_version {}", self.timeline.pg_version);

            if let Some(img) = relmap_img {
                // filenode map for global tablespace
                let header = new_tar_header("global/pg_filenode.map", img.len() as u64)?;
-                self.ar.append(&header, &img[..]).await?;
+                self.ar
+                    .append(&header, &img[..])
+                    .await
+                    .map_err(BasebackupError::Client)?;
            } else {
                warn!("global/pg_filenode.map is missing");
            }
@@ -466,18 +524,26 @@ where
                && self
                    .timeline
                    .list_rels(spcnode, dbnode, Version::Lsn(self.lsn), self.ctx)
-                    .await?
+                    .await
+                    .map_err(|e| BasebackupError::Server(e.into()))?
                    .is_empty()
            {
                return Ok(());
            }
            // User defined tablespaces are not supported
-            ensure!(spcnode == DEFAULTTABLESPACE_OID);
+            if spcnode != DEFAULTTABLESPACE_OID {
+                return Err(BasebackupError::Server(anyhow!(
+                    "spcnode != DEFAULTTABLESPACE_OID, spcnode={spcnode}"
+                )));
+            }

            // Append dir path for each database
            let path = format!("base/{}", dbnode);
            let header = new_tar_header_dir(&path)?;
-            self.ar.append(&header, &mut io::empty()).await?;
+            self.ar
+                .append(&header, &mut io::empty())
+                .await
+                .map_err(BasebackupError::Client)?;

            if let Some(img) = relmap_img {
                let dst_path = format!("base/{}/PG_VERSION", dbnode);
@@ -487,11 +553,17 @@ where
                    ver => format!("{ver}\x0A"),
                };
                let header = new_tar_header(&dst_path, pg_version_str.len() as u64)?;
-                self.ar.append(&header, pg_version_str.as_bytes()).await?;
+                self.ar
+                    .append(&header, pg_version_str.as_bytes())
+                    .await
+                    .map_err(BasebackupError::Client)?;

                let relmap_path = format!("base/{}/pg_filenode.map", dbnode);
                let header = new_tar_header(&relmap_path, img.len() as u64)?;
-                self.ar.append(&header, &img[..]).await?;
+                self.ar
+                    .append(&header, &img[..])
+                    .await
+                    .map_err(BasebackupError::Client)?;
            }
        };
        Ok(())
@@ -500,11 +572,12 @@ where
    //
    // Extract twophase state files
    //
-    async fn add_twophase_file(&mut self, xid: TransactionId) -> anyhow::Result<()> {
+    async fn add_twophase_file(&mut self, xid: TransactionId) -> Result<(), BasebackupError> {
        let img = self
            .timeline
            .get_twophase_file(xid, self.lsn, self.ctx)
-            .await?;
+            .await
+            .map_err(|e| BasebackupError::Server(e.into()))?;

        let mut buf = BytesMut::new();
        buf.extend_from_slice(&img[..]);
@@ -512,7 +585,10 @@ where
        buf.put_u32_le(crc);
        let path = format!("pg_twophase/{:>08X}", xid);
        let header = new_tar_header(&path, buf.len() as u64)?;
-        self.ar.append(&header, &buf[..]).await?;
+        self.ar
+            .append(&header, &buf[..])
+            .await
+            .map_err(BasebackupError::Client)?;

        Ok(())
    }
@@ -521,24 +597,28 @@ where
    // Add generated pg_control file and bootstrap WAL segment.
    // Also send zenith.signal file with extra bootstrap data.
    //
-    async fn add_pgcontrol_file(&mut self) -> anyhow::Result<()> {
+    async fn add_pgcontrol_file(&mut self) -> Result<(), BasebackupError> {
        // add zenith.signal file
        let mut zenith_signal = String::new();
        if self.prev_record_lsn == Lsn(0) {
-            if self.lsn == self.timeline.get_ancestor_lsn() {
-                write!(zenith_signal, "PREV LSN: none")?;
+            if self.timeline.is_ancestor_lsn(self.lsn) {
+                write!(zenith_signal, "PREV LSN: none")
+                    .map_err(|e| BasebackupError::Server(e.into()))?;
            } else {
-                write!(zenith_signal, "PREV LSN: invalid")?;
+                write!(zenith_signal, "PREV LSN: invalid")
+                    .map_err(|e| BasebackupError::Server(e.into()))?;
            }
        } else {
-            write!(zenith_signal, "PREV LSN: {}", self.prev_record_lsn)?;
+            write!(zenith_signal, "PREV LSN: {}", self.prev_record_lsn)
+                .map_err(|e| BasebackupError::Server(e.into()))?;
        }
        self.ar
            .append(
                &new_tar_header("zenith.signal", zenith_signal.len() as u64)?,
                zenith_signal.as_bytes(),
            )
-            .await?;
+            .await
+            .map_err(BasebackupError::Client)?;

        let checkpoint_bytes = self
            .timeline
@@ -560,7 +640,10 @@ where

        //send pg_control
        let header = new_tar_header("global/pg_control", pg_control_bytes.len() as u64)?;
-        self.ar.append(&header, &pg_control_bytes[..]).await?;
+        self.ar
+            .append(&header, &pg_control_bytes[..])
+            .await
+            .map_err(BasebackupError::Client)?;

        //send wal segment
        let segno = self.lsn.segment_number(WAL_SEGMENT_SIZE);
@@ -575,8 +658,16 @@ where
            self.lsn,
        )
        .map_err(|e| anyhow!(e).context("Failed generating wal segment"))?;
-        ensure!(wal_seg.len() == WAL_SEGMENT_SIZE);
-        self.ar.append(&header, &wal_seg[..]).await?;
+        if wal_seg.len() != WAL_SEGMENT_SIZE {
+            return Err(BasebackupError::Server(anyhow!(
+                "wal_seg.len() != WAL_SEGMENT_SIZE, wal_seg.len()={}",
+                wal_seg.len()
+            )));
+        }
+        self.ar
+            .append(&header, &wal_seg[..])
+            .await
+            .map_err(BasebackupError::Client)?;
        Ok(())
    }
 }
--- a/pageserver/src/bin/pageserver.rs
+++ b/pageserver/src/bin/pageserver.rs
@@ -3,6 +3,7 @@
 //! Main entry point for the Page Server executable.

 use std::env::{var, VarError};
+use std::io::Read;
 use std::sync::Arc;
 use std::time::Duration;
 use std::{env, ops::ControlFlow, str::FromStr};
@@ -151,37 +152,34 @@ fn initialize_config(
    workdir: &Utf8Path,
 ) -> anyhow::Result<ControlFlow<(), &'static PageServerConf>> {
    let init = arg_matches.get_flag("init");
-    let update_config = init || arg_matches.get_flag("update-config");

-    let (mut toml, config_file_exists) = if cfg_file_path.is_file() {
-        if init {
-            anyhow::bail!(
-                "Config file '{cfg_file_path}' already exists, cannot init it, use --update-config to update it",
-            );
+    let file_contents: Option<toml_edit::Document> = match std::fs::File::open(cfg_file_path) {
+        Ok(mut f) => {
+            if init {
+                anyhow::bail!("config file already exists: {cfg_file_path}");
+            }
+            let md = f.metadata().context("stat config file")?;
+            if md.is_file() {
+                let mut s = String::new();
+                f.read_to_string(&mut s).context("read config file")?;
+                Some(s.parse().context("parse config file toml")?)
+            } else {
+                anyhow::bail!("directory entry exists but is not a file: {cfg_file_path}");
+            }
+        }
+        Err(e) if e.kind() == std::io::ErrorKind::NotFound => None,
+        Err(e) => {
+            anyhow::bail!("open pageserver config: {e}: {cfg_file_path}");
        }
-        // Supplement the CLI arguments with the config file
-        let cfg_file_contents = std::fs::read_to_string(cfg_file_path)
-            .with_context(|| format!("Failed to read pageserver config at '{cfg_file_path}'"))?;
-        (
-            cfg_file_contents
-                .parse::<toml_edit::Document>()
-                .with_context(|| {
-                    format!("Failed to parse '{cfg_file_path}' as pageserver config")
-                })?,
-            true,
-        )
-    } else if cfg_file_path.exists() {
-        anyhow::bail!("Config file '{cfg_file_path}' exists but is not a regular file");
-    } else {
-        // We're initializing the tenant, so there's no config file yet
-        (
-            DEFAULT_CONFIG_FILE
-                .parse::<toml_edit::Document>()
-                .context("could not parse built-in config file")?,
-            false,
-        )
    };

+    let mut effective_config = file_contents.unwrap_or_else(|| {
+        DEFAULT_CONFIG_FILE
+            .parse()
+            .expect("unit tests ensure this works")
+    });
+
+    // Patch with overrides from the command line
    if let Some(values) = arg_matches.get_many::<String>("config-override") {
        for option_line in values {
            let doc = toml_edit::Document::from_str(option_line).with_context(|| {
@@ -189,22 +187,21 @@ fn initialize_config(
            })?;

            for (key, item) in doc.iter() {
-                if config_file_exists && update_config && key == "id" && toml.contains_key(key) {
-                    anyhow::bail!("Pageserver config file exists at '{cfg_file_path}' and has node id already, it cannot be overridden");
-                }
-                toml.insert(key, item.clone());
+                effective_config.insert(key, item.clone());
            }
        }
    }

-    debug!("Resulting toml: {toml}");
-    let conf = PageServerConf::parse_and_validate(&toml, workdir)
+    debug!("Resulting toml: {effective_config}");
+
+    // Construct the runtime representation
+    let conf = PageServerConf::parse_and_validate(&effective_config, workdir)
        .context("Failed to parse pageserver configuration")?;

-    if update_config {
+    if init {
        info!("Writing pageserver config to '{cfg_file_path}'");

-        std::fs::write(cfg_file_path, toml.to_string())
+        std::fs::write(cfg_file_path, effective_config.to_string())
            .with_context(|| format!("Failed to write pageserver config to '{cfg_file_path}'"))?;
        info!("Config successfully written to '{cfg_file_path}'")
    }
@@ -386,7 +383,7 @@ fn start_pageserver(
    let shutdown_pageserver = tokio_util::sync::CancellationToken::new();

    // Set up remote storage client
-    let remote_storage = create_remote_storage_client(conf)?;
+    let remote_storage = Some(create_remote_storage_client(conf)?);

    // Set up deletion queue
    let (deletion_queue, deletion_workers) = DeletionQueue::new(
@@ -711,12 +708,11 @@ fn start_pageserver(

 fn create_remote_storage_client(
    conf: &'static PageServerConf,
-) -> anyhow::Result<Option<GenericRemoteStorage>> {
+) -> anyhow::Result<GenericRemoteStorage> {
    let config = if let Some(config) = &conf.remote_storage_config {
        config
    } else {
-        tracing::warn!("no remote storage configured, this is a deprecated configuration");
-        return Ok(None);
+        anyhow::bail!("no remote storage configured, this is a deprecated configuration");
    };

    // Create the client
@@ -736,7 +732,7 @@ fn create_remote_storage_client(
            GenericRemoteStorage::unreliable_wrapper(remote_storage, conf.test_remote_failures);
    }

-    Ok(Some(remote_storage))
+    Ok(remote_storage)
 }

 fn cli() -> Command {
@@ -758,18 +754,13 @@ fn cli() -> Command {
        // See `settings.md` for more details on the extra configuration patameters pageserver can process
        .arg(
            Arg::new("config-override")
+                .long("config-override")
                .short('c')
                .num_args(1)
                .action(ArgAction::Append)
                .help("Additional configuration overrides of the ones from the toml config file (or new ones to add there). \
                Any option has to be a valid toml document, example: `-c=\"foo='hey'\"` `-c=\"foo={value=1}\"`"),
        )
-        .arg(
-            Arg::new("update-config")
-                .long("update-config")
-                .action(ArgAction::SetTrue)
-                .help("Update the config file when started"),
-        )
        .arg(
            Arg::new("enabled-features")
                .long("enabled-features")
--- a/pageserver/src/config.rs
+++ b/pageserver/src/config.rs
@@ -9,7 +9,7 @@ use pageserver_api::shard::TenantShardId;
 use remote_storage::{RemotePath, RemoteStorageConfig};
 use serde;
 use serde::de::IntoDeserializer;
-use std::{collections::HashMap, env};
+use std::env;
 use storage_broker::Uri;
 use utils::crashsafe::path_with_suffix_extension;
 use utils::id::ConnectionId;
@@ -51,7 +51,7 @@ pub mod defaults {
    use crate::tenant::config::defaults::*;
    use const_format::formatcp;

-    pub use pageserver_api::{
+    pub use pageserver_api::config::{
        DEFAULT_HTTP_LISTEN_ADDR, DEFAULT_HTTP_LISTEN_PORT, DEFAULT_PG_LISTEN_ADDR,
        DEFAULT_PG_LISTEN_PORT,
    };
@@ -335,26 +335,6 @@ impl<T: Clone> BuilderValue<T> {
    }
 }

-// Certain metadata (e.g. externally-addressable name, AZ) is delivered
-// as a separate structure.  This information is not neeed by the pageserver
-// itself, it is only used for registering the pageserver with the control
-// plane and/or storage controller.
-//
-#[derive(serde::Deserialize)]
-pub(crate) struct NodeMetadata {
-    #[serde(rename = "host")]
-    pub(crate) postgres_host: String,
-    #[serde(rename = "port")]
-    pub(crate) postgres_port: u16,
-    pub(crate) http_host: String,
-    pub(crate) http_port: u16,
-
-    // Deployment tools may write fields to the metadata file beyond what we
-    // use in this type: this type intentionally only names fields that require.
-    #[serde(flatten)]
-    pub(crate) other: HashMap<String, serde_json::Value>,
-}
-
 // needed to simplify config construction
 #[derive(Default)]
 struct PageServerConfigBuilder {
--- a/pageserver/src/control_plane_client.rs
+++ b/pageserver/src/control_plane_client.rs
@@ -14,10 +14,8 @@ use tokio_util::sync::CancellationToken;
 use url::Url;
 use utils::{backoff, failpoint_support, generation::Generation, id::NodeId};

-use crate::{
-    config::{NodeMetadata, PageServerConf},
-    virtual_file::on_fatal_io_error,
-};
+use crate::{config::PageServerConf, virtual_file::on_fatal_io_error};
+use pageserver_api::config::NodeMetadata;

 /// The Pageserver's client for using the control plane API: this is a small subset
 /// of the overall control plane API, for dealing with generations (see docs/rfcs/025-generation-numbers.md)
@@ -65,7 +63,7 @@ impl ControlPlaneClient {
        let mut client = reqwest::ClientBuilder::new();

        if let Some(jwt) = &conf.control_plane_api_token {
-            let mut headers = hyper::HeaderMap::new();
+            let mut headers = reqwest::header::HeaderMap::new();
            headers.insert(
                "Authorization",
                format!("Bearer {}", jwt.get_contents()).parse().unwrap(),
--- a/pageserver/src/deletion_queue.rs
+++ b/pageserver/src/deletion_queue.rs
@@ -38,7 +38,7 @@ use deleter::DeleterMessage;
 use list_writer::ListWriterQueueMessage;
 use validator::ValidatorQueueMessage;

-use crate::{config::PageServerConf, tenant::storage_layer::LayerFileName};
+use crate::{config::PageServerConf, tenant::storage_layer::LayerName};

 // TODO: configurable for how long to wait before executing deletions

@@ -479,7 +479,7 @@ impl DeletionQueueClient {
        tenant_shard_id: TenantShardId,
        timeline_id: TimelineId,
        current_generation: Generation,
-        layers: Vec<(LayerFileName, LayerFileMetadata)>,
+        layers: Vec<(LayerName, LayerFileMetadata)>,
    ) -> Result<(), DeletionQueueError> {
        if current_generation.is_none() {
            debug!("Enqueuing deletions in legacy mode, skipping queue");
@@ -511,7 +511,7 @@ impl DeletionQueueClient {
        tenant_shard_id: TenantShardId,
        timeline_id: TimelineId,
        current_generation: Generation,
-        layers: Vec<(LayerFileName, LayerFileMetadata)>,
+        layers: Vec<(LayerName, LayerFileMetadata)>,
    ) -> Result<(), DeletionQueueError> {
        metrics::DELETION_QUEUE
            .keys_submitted
@@ -734,20 +734,20 @@ mod test {
    use crate::{
        control_plane_client::RetryForeverError,
        repository::Key,
-        tenant::{harness::TenantHarness, storage_layer::DeltaFileName},
+        tenant::{harness::TenantHarness, storage_layer::DeltaLayerName},
    };

    use super::*;
    pub const TIMELINE_ID: TimelineId =
        TimelineId::from_array(hex!("11223344556677881122334455667788"));

-    pub const EXAMPLE_LAYER_NAME: LayerFileName = LayerFileName::Delta(DeltaFileName {
+    pub const EXAMPLE_LAYER_NAME: LayerName = LayerName::Delta(DeltaLayerName {
        key_range: Key::from_i128(0x0)..Key::from_i128(0xFFFFFFFFFFFFFFFF),
        lsn_range: Lsn(0x00000000016B59D8)..Lsn(0x00000000016B5A51),
    });

    // When you need a second layer in a test.
-    pub const EXAMPLE_LAYER_NAME_ALT: LayerFileName = LayerFileName::Delta(DeltaFileName {
+    pub const EXAMPLE_LAYER_NAME_ALT: LayerName = LayerName::Delta(DeltaLayerName {
        key_range: Key::from_i128(0x0)..Key::from_i128(0xFFFFFFFFFFFFFFFF),
        lsn_range: Lsn(0x00000000016B5A51)..Lsn(0x00000000016B5A61),
    });
@@ -797,7 +797,7 @@ mod test {
        /// Returns remote layer file name, suitable for use in assert_remote_files
        fn write_remote_layer(
            &self,
-            file_name: LayerFileName,
+            file_name: LayerName,
            gen: Generation,
        ) -> anyhow::Result<String> {
            let tenant_shard_id = self.harness.tenant_shard_id;
@@ -952,7 +952,7 @@ mod test {
        let client = ctx.deletion_queue.new_client();
        client.recover(HashMap::new())?;

-        let layer_file_name_1: LayerFileName = "000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000016B59D8-00000000016B5A51".parse().unwrap();
+        let layer_file_name_1: LayerName = "000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000016B59D8-00000000016B5A51".parse().unwrap();
        let tenant_shard_id = ctx.harness.tenant_shard_id;

        let content: Vec<u8> = "victim1 contents".into();
--- a/pageserver/src/deletion_queue/list_writer.rs
+++ b/pageserver/src/deletion_queue/list_writer.rs
@@ -34,7 +34,7 @@ use crate::deletion_queue::TEMP_SUFFIX;
 use crate::metrics;
 use crate::tenant::remote_timeline_client::remote_layer_path;
 use crate::tenant::remote_timeline_client::LayerFileMetadata;
-use crate::tenant::storage_layer::LayerFileName;
+use crate::tenant::storage_layer::LayerName;
 use crate::virtual_file::on_fatal_io_error;
 use crate::virtual_file::MaybeFatalIo;

@@ -59,7 +59,7 @@ pub(super) struct DeletionOp {
    // `layers` and `objects` are both just lists of objects.  `layers` is used if you do not
    // have a config object handy to project it to a remote key, and need the consuming worker
    // to do it for you.
-    pub(super) layers: Vec<(LayerFileName, LayerFileMetadata)>,
+    pub(super) layers: Vec<(LayerName, LayerFileMetadata)>,
    pub(super) objects: Vec<RemotePath>,

    /// The _current_ generation of the Tenant shard attachment in which we are enqueuing
--- a/pageserver/src/disk_usage_eviction_task.rs
+++ b/pageserver/src/disk_usage_eviction_task.rs
@@ -64,7 +64,7 @@ use crate::{
        mgr::TenantManager,
        remote_timeline_client::LayerFileMetadata,
        secondary::SecondaryTenant,
-        storage_layer::{AsLayerDesc, EvictionError, Layer, LayerFileName},
+        storage_layer::{AsLayerDesc, EvictionError, Layer, LayerName},
    },
 };

@@ -540,7 +540,12 @@ pub(crate) async fn disk_usage_eviction_task_iteration_impl<U: Usage>(
                    js.spawn(async move {
                        layer
                            .secondary_tenant
-                            .evict_layer(tenant_manager.get_conf(), layer.timeline_id, layer.name)
+                            .evict_layer(
+                                tenant_manager.get_conf(),
+                                layer.timeline_id,
+                                layer.name,
+                                layer.metadata,
+                            )
                            .await;
                        Ok(file_size)
                    });
@@ -599,7 +604,7 @@ pub(crate) async fn disk_usage_eviction_task_iteration_impl<U: Usage>(
 pub(crate) struct EvictionSecondaryLayer {
    pub(crate) secondary_tenant: Arc<SecondaryTenant>,
    pub(crate) timeline_id: TimelineId,
-    pub(crate) name: LayerFileName,
+    pub(crate) name: LayerName,
    pub(crate) metadata: LayerFileMetadata,
 }

@@ -632,9 +637,9 @@ impl EvictionLayer {
        }
    }

-    pub(crate) fn get_name(&self) -> LayerFileName {
+    pub(crate) fn get_name(&self) -> LayerName {
        match self {
-            Self::Attached(l) => l.layer_desc().filename(),
+            Self::Attached(l) => l.layer_desc().layer_name(),
            Self::Secondary(sl) => sl.name.clone(),
        }
    }
--- a/pageserver/src/http/openapi_spec.yml
+++ b/pageserver/src/http/openapi_spec.yml
@@ -420,25 +420,6 @@ paths:
          description: Tenant scheduled to load successfully

  /v1/tenant/{tenant_id}/synthetic_size:
-    parameters:
-      - name: tenant_id
-        in: path
-        required: true
-        schema:
-          type: string
-    get:
-      description: |
-        Calculate tenant's synthetic size
-      responses:
-        "200":
-          description: Tenant's synthetic size
-          content:
-            application/json:
-              schema:
-                $ref: "#/components/schemas/SyntheticSizeResponse"
-
-  # This route has no handler. TODO: remove?
-  /v1/tenant/{tenant_id}/size:
    parameters:
      - name: tenant_id
        in: path
@@ -468,19 +449,9 @@ paths:
          content:
            application/json:
              schema:
-                type: object
-                required:
-                  - id
-                  - size
-                properties:
-                  id:
-                    type: string
-                    format: hex
-                  size:
-                    type: integer
-                    nullable: true
-                    description: |
-                      Size metric in bytes or null if inputs_only=true was given.
+                $ref: "#/components/schemas/SyntheticSizeResponse"
+            text/html:
+              description: SVG representation of the tenant and it's timelines.
        "401":
          description: Unauthorized Error
          content:
@@ -782,9 +753,6 @@ components:
      required:
        - mode
      properties:
-        tenant_id:
-          type: string
-          description: Not used, scheduled for removal.
        mode:
          type: string
          enum: ["AttachedSingle", "AttachedMulti", "AttachedStale", "Secondary", "Detached"]
@@ -932,6 +900,9 @@ components:
          format: hex
        size:
          type: integer
+          nullable: true
+          description: |
+            Size metric in bytes or null if inputs_only=true was given.
        segment_sizes:
          type: array
          items:
--- a/pageserver/src/http/routes.rs
+++ b/pageserver/src/http/routes.rs
@@ -63,6 +63,7 @@ use crate::tenant::remote_timeline_client::list_remote_timelines;
 use crate::tenant::secondary::SecondaryController;
 use crate::tenant::size::ModelInputs;
 use crate::tenant::storage_layer::LayerAccessStatsReset;
+use crate::tenant::storage_layer::LayerName;
 use crate::tenant::timeline::CompactFlags;
 use crate::tenant::timeline::Timeline;
 use crate::tenant::SpawnMode;
@@ -1228,13 +1229,15 @@ async fn layer_download_handler(
    let timeline_id: TimelineId = parse_request_param(&request, "timeline_id")?;
    let layer_file_name = get_request_param(&request, "layer_file_name")?;
    check_permission(&request, Some(tenant_shard_id.tenant_id))?;
+    let layer_name = LayerName::from_str(layer_file_name)
+        .map_err(|s| ApiError::BadRequest(anyhow::anyhow!(s)))?;
    let state = get_state(&request);

    let timeline =
        active_timeline_of_active_tenant(&state.tenant_manager, tenant_shard_id, timeline_id)
            .await?;
    let downloaded = timeline
-        .download_layer(layer_file_name)
+        .download_layer(&layer_name)
        .await
        .map_err(ApiError::InternalServerError)?;

@@ -1258,11 +1261,14 @@ async fn evict_timeline_layer_handler(
    let layer_file_name = get_request_param(&request, "layer_file_name")?;
    let state = get_state(&request);

+    let layer_name = LayerName::from_str(layer_file_name)
+        .map_err(|s| ApiError::BadRequest(anyhow::anyhow!(s)))?;
+
    let timeline =
        active_timeline_of_active_tenant(&state.tenant_manager, tenant_shard_id, timeline_id)
            .await?;
    let evicted = timeline
-        .evict_layer(layer_file_name)
+        .evict_layer(&layer_name)
        .await
        .map_err(ApiError::InternalServerError)?;

@@ -1827,6 +1833,75 @@ async fn timeline_download_remote_layers_handler_get(
    json_response(StatusCode::OK, info)
 }

+async fn timeline_detach_ancestor_handler(
+    request: Request<Body>,
+    _cancel: CancellationToken,
+) -> Result<Response<Body>, ApiError> {
+    use crate::tenant::timeline::detach_ancestor::Options;
+    let tenant_shard_id: TenantShardId = parse_request_param(&request, "tenant_shard_id")?;
+    check_permission(&request, Some(tenant_shard_id.tenant_id))?;
+    let timeline_id: TimelineId = parse_request_param(&request, "timeline_id")?;
+
+    let span = tracing::info_span!("detach_ancestor", tenant_id=%tenant_shard_id.tenant_id, shard_id=%tenant_shard_id.shard_slug(), %timeline_id);
+
+    async move {
+        let mut options = Options::default();
+
+        let rewrite_concurrency =
+            parse_query_param::<_, std::num::NonZeroUsize>(&request, "rewrite_concurrency")?;
+        let copy_concurrency =
+            parse_query_param::<_, std::num::NonZeroUsize>(&request, "copy_concurrency")?;
+
+        [
+            (&mut options.rewrite_concurrency, rewrite_concurrency),
+            (&mut options.copy_concurrency, copy_concurrency),
+        ]
+        .into_iter()
+        .filter_map(|(target, val)| val.map(|val| (target, val)))
+        .for_each(|(target, val)| *target = val);
+
+        let state = get_state(&request);
+
+        let tenant = state
+            .tenant_manager
+            .get_attached_tenant_shard(tenant_shard_id)?;
+
+        tenant.wait_to_become_active(ACTIVE_TENANT_TIMEOUT).await?;
+
+        let ctx = RequestContext::new(TaskKind::DetachAncestor, DownloadBehavior::Download);
+        let ctx = &ctx;
+
+        let timeline = tenant
+            .get_timeline(timeline_id, true)
+            .map_err(|e| ApiError::NotFound(e.into()))?;
+
+        let (_guard, prepared) = timeline
+            .prepare_to_detach_from_ancestor(&tenant, options, ctx)
+            .await
+            .map_err(|e| ApiError::InternalServerError(e.into()))?;
+
+        let res = state
+            .tenant_manager
+            .complete_detaching_timeline_ancestor(tenant_shard_id, timeline_id, prepared, ctx)
+            .await;
+
+        match res {
+            Ok(reparented_timelines) => {
+                let resp = pageserver_api::models::detach_ancestor::AncestorDetached {
+                    reparented_timelines,
+                };
+
+                json_response(StatusCode::OK, resp)
+            }
+            Err(e) => Err(ApiError::InternalServerError(
+                e.context("timeline detach completion"),
+            )),
+        }
+    }
+    .instrument(span)
+    .await
+}
+
 async fn deletion_queue_flush(
    r: Request<Body>,
    cancel: CancellationToken,
@@ -2160,6 +2235,27 @@ async fn secondary_download_handler(
    json_response(status, progress)
 }

+async fn secondary_status_handler(
+    request: Request<Body>,
+    _cancel: CancellationToken,
+) -> Result<Response<Body>, ApiError> {
+    let state = get_state(&request);
+    let tenant_shard_id: TenantShardId = parse_request_param(&request, "tenant_shard_id")?;
+
+    let Some(secondary_tenant) = state
+        .tenant_manager
+        .get_secondary_tenant_shard(tenant_shard_id)
+    else {
+        return Err(ApiError::NotFound(
+            anyhow::anyhow!("Shard {} not found", tenant_shard_id).into(),
+        ));
+    };
+
+    let progress = secondary_tenant.progress.lock().unwrap().clone();
+
+    json_response(StatusCode::OK, progress)
+}
+
 async fn handler_404(_: Request<Body>) -> Result<Response<Body>, ApiError> {
    json_response(
        StatusCode::NOT_FOUND,
@@ -2494,6 +2590,10 @@ pub fn make_router(
            "/v1/tenant/:tenant_shard_id/timeline/:timeline_id/download_remote_layers",
            |r| api_handler(r, timeline_download_remote_layers_handler_get),
        )
+        .put(
+            "/v1/tenant/:tenant_shard_id/timeline/:timeline_id/detach_ancestor",
+            |r| api_handler(r, timeline_detach_ancestor_handler),
+        )
        .delete("/v1/tenant/:tenant_shard_id/timeline/:timeline_id", |r| {
            api_handler(r, timeline_delete_handler)
        })
@@ -2521,6 +2621,9 @@ pub fn make_router(
        .put("/v1/deletion_queue/flush", |r| {
            api_handler(r, deletion_queue_flush)
        })
+        .get("/v1/tenant/:tenant_shard_id/secondary/status", |r| {
+            api_handler(r, secondary_status_handler)
+        })
        .post("/v1/tenant/:tenant_shard_id/secondary/download", |r| {
            api_handler(r, secondary_download_handler)
        })
--- a/pageserver/src/metrics.rs
+++ b/pageserver/src/metrics.rs
@@ -51,8 +51,8 @@ pub(crate) enum StorageTimeOperation {
    #[strum(serialize = "gc")]
    Gc,

-    #[strum(serialize = "update gc info")]
-    UpdateGcInfo,
+    #[strum(serialize = "find gc cutoffs")]
+    FindGcCutoffs,

    #[strum(serialize = "create tenant")]
    CreateTenant,
@@ -194,6 +194,11 @@ pub(crate) struct GetVectoredLatency {
    map: EnumMap<TaskKind, Option<Histogram>>,
 }

+#[allow(dead_code)]
+pub(crate) struct ScanLatency {
+    map: EnumMap<TaskKind, Option<Histogram>>,
+}
+
 impl GetVectoredLatency {
    // Only these task types perform vectored gets. Filter all other tasks out to reduce total
    // cardinality of the metric.
@@ -204,6 +209,48 @@ impl GetVectoredLatency {
    }
 }

+impl ScanLatency {
+    // Only these task types perform vectored gets. Filter all other tasks out to reduce total
+    // cardinality of the metric.
+    const TRACKED_TASK_KINDS: [TaskKind; 1] = [TaskKind::PageRequestHandler];
+
+    pub(crate) fn for_task_kind(&self, task_kind: TaskKind) -> Option<&Histogram> {
+        self.map[task_kind].as_ref()
+    }
+}
+
+pub(crate) struct ScanLatencyOngoingRecording<'a> {
+    parent: &'a Histogram,
+    start: std::time::Instant,
+}
+
+impl<'a> ScanLatencyOngoingRecording<'a> {
+    pub(crate) fn start_recording(parent: &'a Histogram) -> ScanLatencyOngoingRecording<'a> {
+        let start = Instant::now();
+        ScanLatencyOngoingRecording { parent, start }
+    }
+
+    pub(crate) fn observe(self, throttled: Option<Duration>) {
+        let elapsed = self.start.elapsed();
+        let ex_throttled = if let Some(throttled) = throttled {
+            elapsed.checked_sub(throttled)
+        } else {
+            Some(elapsed)
+        };
+        if let Some(ex_throttled) = ex_throttled {
+            self.parent.observe(ex_throttled.as_secs_f64());
+        } else {
+            use utils::rate_limit::RateLimit;
+            static LOGGED: Lazy<Mutex<RateLimit>> =
+                Lazy::new(|| Mutex::new(RateLimit::new(Duration::from_secs(10))));
+            let mut rate_limit = LOGGED.lock().unwrap();
+            rate_limit.call(|| {
+                warn!("error deducting time spent throttled; this message is logged at a global rate limit");
+            });
+        }
+    }
+}
+
 pub(crate) static GET_VECTORED_LATENCY: Lazy<GetVectoredLatency> = Lazy::new(|| {
    let inner = register_histogram_vec!(
        "pageserver_get_vectored_seconds",
@@ -227,6 +274,29 @@ pub(crate) static GET_VECTORED_LATENCY: Lazy<GetVectoredLatency> = Lazy::new(||
    }
 });

+pub(crate) static SCAN_LATENCY: Lazy<ScanLatency> = Lazy::new(|| {
+    let inner = register_histogram_vec!(
+        "pageserver_scan_seconds",
+        "Time spent in scan, excluding time spent in timeline_get_throttle.",
+        &["task_kind"],
+        CRITICAL_OP_BUCKETS.into(),
+    )
+    .expect("failed to define a metric");
+
+    ScanLatency {
+        map: EnumMap::from_array(std::array::from_fn(|task_kind_idx| {
+            let task_kind = <TaskKind as enum_map::Enum>::from_usize(task_kind_idx);
+
+            if ScanLatency::TRACKED_TASK_KINDS.contains(&task_kind) {
+                let task_kind = task_kind.into();
+                Some(inner.with_label_values(&[task_kind]))
+            } else {
+                None
+            }
+        })),
+    }
+});
+
 pub(crate) struct PageCacheMetricsForTaskKind {
    pub read_accesses_materialized_page: IntCounter,
    pub read_accesses_immutable: IntCounter,
@@ -1442,29 +1512,80 @@ static REMOTE_TIMELINE_CLIENT_BYTES_FINISHED_COUNTER: Lazy<IntCounterVec> = Lazy
 });

 pub(crate) struct TenantManagerMetrics {
-    pub(crate) tenant_slots: UIntGauge,
+    tenant_slots_attached: UIntGauge,
+    tenant_slots_secondary: UIntGauge,
+    tenant_slots_inprogress: UIntGauge,
    pub(crate) tenant_slot_writes: IntCounter,
    pub(crate) unexpected_errors: IntCounter,
 }

+impl TenantManagerMetrics {
+    /// Helpers for tracking slots.  Note that these do not track the lifetime of TenantSlot objects
+    /// exactly: they track the lifetime of the slots _in the tenant map_.
+    pub(crate) fn slot_inserted(&self, slot: &TenantSlot) {
+        match slot {
+            TenantSlot::Attached(_) => {
+                self.tenant_slots_attached.inc();
+            }
+            TenantSlot::Secondary(_) => {
+                self.tenant_slots_secondary.inc();
+            }
+            TenantSlot::InProgress(_) => {
+                self.tenant_slots_inprogress.inc();
+            }
+        }
+    }
+
+    pub(crate) fn slot_removed(&self, slot: &TenantSlot) {
+        match slot {
+            TenantSlot::Attached(_) => {
+                self.tenant_slots_attached.dec();
+            }
+            TenantSlot::Secondary(_) => {
+                self.tenant_slots_secondary.dec();
+            }
+            TenantSlot::InProgress(_) => {
+                self.tenant_slots_inprogress.dec();
+            }
+        }
+    }
+
+    #[cfg(all(debug_assertions, not(test)))]
+    pub(crate) fn slots_total(&self) -> u64 {
+        self.tenant_slots_attached.get()
+            + self.tenant_slots_secondary.get()
+            + self.tenant_slots_inprogress.get()
+    }
+}
+
 pub(crate) static TENANT_MANAGER: Lazy<TenantManagerMetrics> = Lazy::new(|| {
-    TenantManagerMetrics {
-    tenant_slots: register_uint_gauge!(
+    let tenant_slots = register_uint_gauge_vec!(
        "pageserver_tenant_manager_slots",
        "How many slots currently exist, including all attached, secondary and in-progress operations",
+        &["mode"]
    )
-    .expect("failed to define a metric"),
-    tenant_slot_writes: register_int_counter!(
-        "pageserver_tenant_manager_slot_writes",
-        "Writes to a tenant slot, including all of create/attach/detach/delete"
-    )
-    .expect("failed to define a metric"),
-    unexpected_errors: register_int_counter!(
-        "pageserver_tenant_manager_unexpected_errors_total",
-        "Number of unexpected conditions encountered: nonzero value indicates a non-fatal bug."
-    )
-    .expect("failed to define a metric"),
-}
+    .expect("failed to define a metric");
+    TenantManagerMetrics {
+        tenant_slots_attached: tenant_slots
+            .get_metric_with_label_values(&["attached"])
+            .unwrap(),
+        tenant_slots_secondary: tenant_slots
+            .get_metric_with_label_values(&["secondary"])
+            .unwrap(),
+        tenant_slots_inprogress: tenant_slots
+            .get_metric_with_label_values(&["inprogress"])
+            .unwrap(),
+        tenant_slot_writes: register_int_counter!(
+            "pageserver_tenant_manager_slot_writes",
+            "Writes to a tenant slot, including all of create/attach/detach/delete"
+        )
+        .expect("failed to define a metric"),
+        unexpected_errors: register_int_counter!(
+            "pageserver_tenant_manager_unexpected_errors_total",
+            "Number of unexpected conditions encountered: nonzero value indicates a non-fatal bug."
+        )
+        .expect("failed to define a metric"),
+    }
 });

 pub(crate) struct DeletionQueueMetrics {
@@ -1989,7 +2110,7 @@ pub(crate) struct TimelineMetrics {
    pub imitate_logical_size_histo: StorageTimeMetrics,
    pub load_layer_map_histo: StorageTimeMetrics,
    pub garbage_collect_histo: StorageTimeMetrics,
-    pub update_gc_info_histo: StorageTimeMetrics,
+    pub find_gc_cutoffs_histo: StorageTimeMetrics,
    pub last_record_gauge: IntGauge,
    resident_physical_size_gauge: UIntGauge,
    /// copy of LayeredTimeline.current_logical_size
@@ -2050,8 +2171,8 @@ impl TimelineMetrics {
            &shard_id,
            &timeline_id,
        );
-        let update_gc_info_histo = StorageTimeMetrics::new(
-            StorageTimeOperation::UpdateGcInfo,
+        let find_gc_cutoffs_histo = StorageTimeMetrics::new(
+            StorageTimeOperation::FindGcCutoffs,
            &tenant_id,
            &shard_id,
            &timeline_id,
@@ -2098,7 +2219,7 @@ impl TimelineMetrics {
            logical_size_histo,
            imitate_logical_size_histo,
            garbage_collect_histo,
-            update_gc_info_histo,
+            find_gc_cutoffs_histo,
            load_layer_map_histo,
            last_record_gauge,
            resident_physical_size_gauge,
@@ -2205,6 +2326,7 @@ use std::time::{Duration, Instant};

 use crate::context::{PageContentKind, RequestContext};
 use crate::task_mgr::TaskKind;
+use crate::tenant::mgr::TenantSlot;

 /// Maintain a per timeline gauge in addition to the global gauge.
 struct PerTimelineRemotePhysicalSizeGauge {
@@ -2807,6 +2929,8 @@ pub fn preinitialize_metrics() {
        &WALRECEIVER_CANDIDATES_REMOVED,
        &tokio_epoll_uring::THREAD_LOCAL_LAUNCH_FAILURES,
        &tokio_epoll_uring::THREAD_LOCAL_LAUNCH_SUCCESSES,
+        &REMOTE_ONDEMAND_DOWNLOADED_LAYERS,
+        &REMOTE_ONDEMAND_DOWNLOADED_BYTES,
    ]
    .into_iter()
    .for_each(|c| {
--- a/pageserver/src/page_service.rs
+++ b/pageserver/src/page_service.rs
@@ -48,6 +48,7 @@ use utils::{

 use crate::auth::check_permission;
 use crate::basebackup;
+use crate::basebackup::BasebackupError;
 use crate::config::PageServerConf;
 use crate::context::{DownloadBehavior, RequestContext};
 use crate::import_datadir::import_wal_from_tar;
@@ -1236,6 +1237,13 @@ impl PageServerHandler {
    where
        IO: AsyncRead + AsyncWrite + Send + Sync + Unpin,
    {
+        fn map_basebackup_error(err: BasebackupError) -> QueryError {
+            match err {
+                BasebackupError::Client(e) => QueryError::Disconnected(ConnectionError::Io(e)),
+                BasebackupError::Server(e) => QueryError::Other(e),
+            }
+        }
+
        let started = std::time::Instant::now();

        // check that the timeline exists
@@ -1261,7 +1269,8 @@ impl PageServerHandler {
        let lsn_awaited_after = started.elapsed();

        // switch client to COPYOUT
-        pgb.write_message_noflush(&BeMessage::CopyOutResponse)?;
+        pgb.write_message_noflush(&BeMessage::CopyOutResponse)
+            .map_err(QueryError::Disconnected)?;
        self.flush_cancellable(pgb, &timeline.cancel).await?;

        // Send a tarball of the latest layer on the timeline. Compress if not
@@ -1276,7 +1285,8 @@ impl PageServerHandler {
                full_backup,
                ctx,
            )
-            .await?;
+            .await
+            .map_err(map_basebackup_error)?;
        } else {
            let mut writer = pgb.copyout_writer();
            if gzip {
@@ -1297,9 +1307,13 @@ impl PageServerHandler {
                    full_backup,
                    ctx,
                )
-                .await?;
+                .await
+                .map_err(map_basebackup_error)?;
                // shutdown the encoder to ensure the gzip footer is written
-                encoder.shutdown().await?;
+                encoder
+                    .shutdown()
+                    .await
+                    .map_err(|e| QueryError::Disconnected(ConnectionError::Io(e)))?;
            } else {
                basebackup::send_basebackup_tarball(
                    &mut writer,
@@ -1309,11 +1323,13 @@ impl PageServerHandler {
                    full_backup,
                    ctx,
                )
-                .await?;
+                .await
+                .map_err(map_basebackup_error)?;
            }
        }

-        pgb.write_message_noflush(&BeMessage::CopyDone)?;
+        pgb.write_message_noflush(&BeMessage::CopyDone)
+            .map_err(QueryError::Disconnected)?;
        self.flush_cancellable(pgb, &timeline.cancel).await?;

        let basebackup_after = started
--- a/pageserver/src/pgdatadir_mapping.rs
+++ b/pageserver/src/pgdatadir_mapping.rs
@@ -10,9 +10,9 @@ use super::tenant::{PageReconstructError, Timeline};
 use crate::context::RequestContext;
 use crate::keyspace::{KeySpace, KeySpaceAccum};
 use crate::metrics::WAL_INGEST;
-use crate::repository::*;
 use crate::span::debug_assert_current_span_has_tenant_and_timeline_id_no_shard_id;
 use crate::walrecord::NeonWalRecord;
+use crate::{aux_file, repository::*};
 use anyhow::{ensure, Context};
 use bytes::{Buf, Bytes, BytesMut};
 use enum_map::Enum;
@@ -24,6 +24,7 @@ use pageserver_api::key::{
    AUX_FILES_KEY, CHECKPOINT_KEY, CONTROLFILE_KEY, DBDIR_KEY, TWOPHASEDIR_KEY,
 };
 use pageserver_api::keyspace::SparseKeySpace;
+use pageserver_api::models::AuxFilePolicy;
 use pageserver_api::reltag::{BlockNumber, RelTag, SlruKind};
 use postgres_ffi::relfile_utils::{FSM_FORKNUM, VISIBILITYMAP_FORKNUM};
 use postgres_ffi::BLCKSZ;
@@ -279,7 +280,7 @@ impl Timeline {

        match RelDirectory::des(&buf).context("deserialization failure") {
            Ok(dir) => {
-                let exists = dir.rels.get(&(tag.relnode, tag.forknum)).is_some();
+                let exists = dir.rels.contains(&(tag.relnode, tag.forknum));
                Ok(exists)
            }
            Err(e) => Err(PageReconstructError::from(e)),
@@ -379,7 +380,7 @@ impl Timeline {

        match SlruSegmentDirectory::des(&buf).context("deserialization failure") {
            Ok(dir) => {
-                let exists = dir.segments.get(&segno).is_some();
+                let exists = dir.segments.contains(&segno);
                Ok(exists)
            }
            Err(e) => Err(PageReconstructError::from(e)),
@@ -670,7 +671,7 @@ impl Timeline {
        self.get(CHECKPOINT_KEY, lsn, ctx).await
    }

-    pub(crate) async fn list_aux_files(
+    async fn list_aux_files_v1(
        &self,
        lsn: Lsn,
        ctx: &RequestContext,
@@ -688,6 +689,63 @@ impl Timeline {
        }
    }

+    async fn list_aux_files_v2(
+        &self,
+        lsn: Lsn,
+        ctx: &RequestContext,
+    ) -> Result<HashMap<String, Bytes>, PageReconstructError> {
+        let kv = self
+            .scan(KeySpace::single(Key::metadata_aux_key_range()), lsn, ctx)
+            .await
+            .context("scan")?;
+        let mut result = HashMap::new();
+        for (_, v) in kv {
+            let v = v.context("get value")?;
+            let v = aux_file::decode_file_value_bytes(&v).context("value decode")?;
+            for (fname, content) in v {
+                result.insert(fname, content);
+            }
+        }
+        Ok(result)
+    }
+
+    pub(crate) async fn list_aux_files(
+        &self,
+        lsn: Lsn,
+        ctx: &RequestContext,
+    ) -> Result<HashMap<String, Bytes>, PageReconstructError> {
+        match self.get_switch_aux_file_policy() {
+            AuxFilePolicy::V1 => self.list_aux_files_v1(lsn, ctx).await,
+            AuxFilePolicy::V2 => self.list_aux_files_v2(lsn, ctx).await,
+            AuxFilePolicy::CrossValidation => {
+                let v1_result = self.list_aux_files_v1(lsn, ctx).await;
+                let v2_result = self.list_aux_files_v2(lsn, ctx).await;
+                match (v1_result, v2_result) {
+                    (Ok(v1), Ok(v2)) => {
+                        if v1 != v2 {
+                            tracing::error!(
+                                "unmatched aux file v1 v2 result:\nv1 {v1:?}\nv2 {v2:?}"
+                            );
+                            return Err(PageReconstructError::Other(anyhow::anyhow!(
+                                "unmatched aux file v1 v2 result"
+                            )));
+                        }
+                        Ok(v1)
+                    }
+                    (Ok(_), Err(v2)) => {
+                        tracing::error!("aux file v1 returns Ok while aux file v2 returns an err");
+                        Err(v2)
+                    }
+                    (Err(v1), Ok(_)) => {
+                        tracing::error!("aux file v2 returns Ok while aux file v1 returns an err");
+                        Err(v1)
+                    }
+                    (Err(_), Err(v2)) => Err(v2),
+                }
+            }
+        }
+    }
+
    /// Does the same as get_current_logical_size but counted on demand.
    /// Used to initialize the logical size tracking on startup.
    ///
@@ -1143,21 +1201,22 @@ impl<'a> DatadirModification<'a> {
        let mut dbdir = DbDirectory::des(&self.get(DBDIR_KEY, ctx).await.context("read db")?)
            .context("deserialize db")?;
        let rel_dir_key = rel_dir_to_key(rel.spcnode, rel.dbnode);
-        let mut rel_dir = if dbdir.dbdirs.get(&(rel.spcnode, rel.dbnode)).is_none() {
-            // Didn't exist. Update dbdir
-            dbdir.dbdirs.insert((rel.spcnode, rel.dbnode), false);
-            let buf = DbDirectory::ser(&dbdir).context("serialize db")?;
-            self.pending_directory_entries
-                .push((DirectoryKind::Db, dbdir.dbdirs.len()));
-            self.put(DBDIR_KEY, Value::Image(buf.into()));
+        let mut rel_dir =
+            if let hash_map::Entry::Vacant(e) = dbdir.dbdirs.entry((rel.spcnode, rel.dbnode)) {
+                // Didn't exist. Update dbdir
+                e.insert(false);
+                let buf = DbDirectory::ser(&dbdir).context("serialize db")?;
+                self.pending_directory_entries
+                    .push((DirectoryKind::Db, dbdir.dbdirs.len()));
+                self.put(DBDIR_KEY, Value::Image(buf.into()));

-            // and create the RelDirectory
-            RelDirectory::default()
-        } else {
-            // reldir already exists, fetch it
-            RelDirectory::des(&self.get(rel_dir_key, ctx).await.context("read db")?)
-                .context("deserialize db")?
-        };
+                // and create the RelDirectory
+                RelDirectory::default()
+            } else {
+                // reldir already exists, fetch it
+                RelDirectory::des(&self.get(rel_dir_key, ctx).await.context("read db")?)
+                    .context("deserialize db")?
+            };

        // Add the new relation to the rel directory entry, and write it back
        if !rel_dir.rels.insert((rel.relnode, rel.forknum)) {
@@ -1388,6 +1447,9 @@ impl<'a> DatadirModification<'a> {
    }

    pub fn init_aux_dir(&mut self) -> anyhow::Result<()> {
+        if let AuxFilePolicy::V2 = self.tline.get_switch_aux_file_policy() {
+            return Ok(());
+        }
        let buf = AuxFilesDirectory::ser(&AuxFilesDirectory {
            files: HashMap::new(),
        })?;
@@ -1403,89 +1465,121 @@ impl<'a> DatadirModification<'a> {
        content: &[u8],
        ctx: &RequestContext,
    ) -> anyhow::Result<()> {
-        let file_path = path.to_string();
-        let content = if content.is_empty() {
-            None
-        } else {
-            Some(Bytes::copy_from_slice(content))
-        };
-
-        let n_files;
-        let mut aux_files = self.tline.aux_files.lock().await;
-        if let Some(mut dir) = aux_files.dir.take() {
-            // We already updated aux files in `self`: emit a delta and update our latest value.
-            dir.upsert(file_path.clone(), content.clone());
-            n_files = dir.files.len();
-            if aux_files.n_deltas == MAX_AUX_FILE_DELTAS {
-                self.put(
-                    AUX_FILES_KEY,
-                    Value::Image(Bytes::from(
-                        AuxFilesDirectory::ser(&dir).context("serialize")?,
-                    )),
-                );
-                aux_files.n_deltas = 0;
+        let policy = self.tline.get_switch_aux_file_policy();
+        if let AuxFilePolicy::V2 | AuxFilePolicy::CrossValidation = policy {
+            let key = aux_file::encode_aux_file_key(path);
+            // retrieve the key from the engine
+            let old_val = match self.get(key, ctx).await {
+                Ok(val) => Some(val),
+                Err(PageReconstructError::MissingKey(_)) => None,
+                Err(e) => return Err(e.into()),
+            };
+            let files = if let Some(ref old_val) = old_val {
+                aux_file::decode_file_value(old_val)?
            } else {
-                self.put(
-                    AUX_FILES_KEY,
-                    Value::WalRecord(NeonWalRecord::AuxFile { file_path, content }),
-                );
-                aux_files.n_deltas += 1;
-            }
-            aux_files.dir = Some(dir);
-        } else {
-            // Check if the AUX_FILES_KEY is initialized
-            match self.get(AUX_FILES_KEY, ctx).await {
-                Ok(dir_bytes) => {
-                    let mut dir = AuxFilesDirectory::des(&dir_bytes)?;
-                    // Key is already set, we may append a delta
-                    self.put(
-                        AUX_FILES_KEY,
-                        Value::WalRecord(NeonWalRecord::AuxFile {
-                            file_path: file_path.clone(),
-                            content: content.clone(),
-                        }),
-                    );
-                    dir.upsert(file_path, content);
-                    n_files = dir.files.len();
-                    aux_files.dir = Some(dir);
-                }
-                Err(
-                    e @ (PageReconstructError::AncestorStopping(_)
-                    | PageReconstructError::Cancelled
-                    | PageReconstructError::AncestorLsnTimeout(_)),
-                ) => {
-                    // Important that we do not interpret a shutdown error as "not found" and thereby
-                    // reset the map.
-                    return Err(e.into());
-                }
-                // Note: we added missing key error variant in https://github.com/neondatabase/neon/pull/7393 but
-                // the original code assumes all other errors are missing keys. Therefore, we keep the code path
-                // the same for now, though in theory, we should only match the `MissingKey` variant.
-                Err(
-                    PageReconstructError::Other(_)
-                    | PageReconstructError::WalRedo(_)
-                    | PageReconstructError::MissingKey { .. },
-                ) => {
-                    // Key is missing, we must insert an image as the basis for subsequent deltas.
+                Vec::new()
+            };
+            let new_files = if content.is_empty() {
+                files
+                    .into_iter()
+                    .filter(|(p, _)| &path != p)
+                    .collect::<Vec<_>>()
+            } else {
+                files
+                    .into_iter()
+                    .filter(|(p, _)| &path != p)
+                    .chain(std::iter::once((path, content)))
+                    .collect::<Vec<_>>()
+            };
+            let new_val = aux_file::encode_file_value(&new_files)?;
+            self.put(key, Value::Image(new_val.into()));
+        }

-                    let mut dir = AuxFilesDirectory {
-                        files: HashMap::new(),
-                    };
-                    dir.upsert(file_path, content);
+        if let AuxFilePolicy::V1 | AuxFilePolicy::CrossValidation = policy {
+            let file_path = path.to_string();
+            let content = if content.is_empty() {
+                None
+            } else {
+                Some(Bytes::copy_from_slice(content))
+            };
+
+            let n_files;
+            let mut aux_files = self.tline.aux_files.lock().await;
+            if let Some(mut dir) = aux_files.dir.take() {
+                // We already updated aux files in `self`: emit a delta and update our latest value.
+                dir.upsert(file_path.clone(), content.clone());
+                n_files = dir.files.len();
+                if aux_files.n_deltas == MAX_AUX_FILE_DELTAS {
                    self.put(
                        AUX_FILES_KEY,
                        Value::Image(Bytes::from(
                            AuxFilesDirectory::ser(&dir).context("serialize")?,
                        )),
                    );
-                    n_files = 1;
-                    aux_files.dir = Some(dir);
+                    aux_files.n_deltas = 0;
+                } else {
+                    self.put(
+                        AUX_FILES_KEY,
+                        Value::WalRecord(NeonWalRecord::AuxFile { file_path, content }),
+                    );
+                    aux_files.n_deltas += 1;
+                }
+                aux_files.dir = Some(dir);
+            } else {
+                // Check if the AUX_FILES_KEY is initialized
+                match self.get(AUX_FILES_KEY, ctx).await {
+                    Ok(dir_bytes) => {
+                        let mut dir = AuxFilesDirectory::des(&dir_bytes)?;
+                        // Key is already set, we may append a delta
+                        self.put(
+                            AUX_FILES_KEY,
+                            Value::WalRecord(NeonWalRecord::AuxFile {
+                                file_path: file_path.clone(),
+                                content: content.clone(),
+                            }),
+                        );
+                        dir.upsert(file_path, content);
+                        n_files = dir.files.len();
+                        aux_files.dir = Some(dir);
+                    }
+                    Err(
+                        e @ (PageReconstructError::AncestorStopping(_)
+                        | PageReconstructError::Cancelled
+                        | PageReconstructError::AncestorLsnTimeout(_)),
+                    ) => {
+                        // Important that we do not interpret a shutdown error as "not found" and thereby
+                        // reset the map.
+                        return Err(e.into());
+                    }
+                    // Note: we added missing key error variant in https://github.com/neondatabase/neon/pull/7393 but
+                    // the original code assumes all other errors are missing keys. Therefore, we keep the code path
+                    // the same for now, though in theory, we should only match the `MissingKey` variant.
+                    Err(
+                        PageReconstructError::Other(_)
+                        | PageReconstructError::WalRedo(_)
+                        | PageReconstructError::MissingKey { .. },
+                    ) => {
+                        // Key is missing, we must insert an image as the basis for subsequent deltas.
+
+                        let mut dir = AuxFilesDirectory {
+                            files: HashMap::new(),
+                        };
+                        dir.upsert(file_path, content);
+                        self.put(
+                            AUX_FILES_KEY,
+                            Value::Image(Bytes::from(
+                                AuxFilesDirectory::ser(&dir).context("serialize")?,
+                            )),
+                        );
+                        n_files = 1;
+                        aux_files.dir = Some(dir);
+                    }
                }
            }
-        }

-        self.pending_directory_entries
-            .push((DirectoryKind::AuxFiles, n_files));
+            self.pending_directory_entries
+                .push((DirectoryKind::AuxFiles, n_files));
+        }

        Ok(())
    }
@@ -1577,7 +1671,7 @@ impl<'a> DatadirModification<'a> {
        }

        if !self.pending_deletions.is_empty() {
-            writer.delete_batch(&self.pending_deletions).await?;
+            writer.delete_batch(&self.pending_deletions, ctx).await?;
            self.pending_deletions.clear();
        }

--- a/pageserver/src/repository.rs
+++ b/pageserver/src/repository.rs
@@ -33,7 +33,6 @@ impl Value {
    }
 }

-#[cfg(test)]
 #[derive(Debug, PartialEq)]
 pub(crate) enum InvalidInput {
    TooShortValue,
@@ -42,10 +41,8 @@ pub(crate) enum InvalidInput {

 /// We could have a ValueRef where everything is `serde(borrow)`. Before implementing that, lets
 /// use this type for querying if a slice looks some particular way.
-#[cfg(test)]
 pub(crate) struct ValueBytes;

-#[cfg(test)]
 impl ValueBytes {
    pub(crate) fn will_init(raw: &[u8]) -> Result<bool, InvalidInput> {
        if raw.len() < 12 {
--- a/pageserver/src/task_mgr.rs
+++ b/pageserver/src/task_mgr.rs
@@ -319,6 +319,9 @@ pub enum TaskKind {
    // Eviction. One per timeline.
    Eviction,

+    // Ingest housekeeping (flushing ephemeral layers on time threshold or disk pressure)
+    IngestHousekeeping,
+
    /// See [`crate::disk_usage_eviction_task`].
    DiskUsageEviction,

@@ -363,8 +366,12 @@ pub enum TaskKind {

    EphemeralFilePreWarmPageCache,

+    LayerDownload,
+
    #[cfg(test)]
    UnitTest,
+
+    DetachAncestor,
 }

 #[derive(Default)]
--- a/pageserver/src/tenant.rs
+++ b/pageserver/src/tenant.rs
@@ -64,6 +64,7 @@ use self::timeline::uninit::UninitializedTimeline;
 use self::timeline::EvictionTaskTenantState;
 use self::timeline::TimelineResources;
 use self::timeline::WaitLsnError;
+use self::timeline::{GcCutoffs, GcInfo};
 use crate::config::PageServerConf;
 use crate::context::{DownloadBehavior, RequestContext};
 use crate::deletion_queue::DeletionQueueClient;
@@ -86,7 +87,6 @@ use crate::tenant::remote_timeline_client::INITDB_PATH;
 use crate::tenant::storage_layer::DeltaLayer;
 use crate::tenant::storage_layer::ImageLayer;
 use crate::InitializationOrder;
-use std::cmp::min;
 use std::collections::hash_map::Entry;
 use std::collections::BTreeSet;
 use std::collections::HashMap;
@@ -322,6 +322,9 @@ pub struct Tenant {
    /// All [`Tenant::timelines`] of a given [`Tenant`] instance share the same [`throttle::Throttle`] instance.
    pub(crate) timeline_get_throttle:
        Arc<throttle::Throttle<&'static crate::metrics::tenant_throttling::TimelineGet>>,
+
+    /// An ongoing timeline detach must be checked during attempts to GC or compact a timeline.
+    ongoing_timeline_detach: std::sync::Mutex<Option<(TimelineId, utils::completion::Barrier)>>,
 }

 impl std::fmt::Debug for Tenant {
@@ -1676,6 +1679,34 @@ impl Tenant {
        Ok(())
    }

+    // Call through to all timelines to freeze ephemeral layers if needed.  Usually
+    // this happens during ingest: this background housekeeping is for freezing layers
+    // that are open but haven't been written to for some time.
+    async fn ingest_housekeeping(&self) {
+        // Scan through the hashmap and collect a list of all the timelines,
+        // while holding the lock. Then drop the lock and actually perform the
+        // compactions.  We don't want to block everything else while the
+        // compaction runs.
+        let timelines = {
+            self.timelines
+                .lock()
+                .unwrap()
+                .values()
+                .filter_map(|timeline| {
+                    if timeline.is_active() {
+                        Some(timeline.clone())
+                    } else {
+                        None
+                    }
+                })
+                .collect::<Vec<_>>()
+        };
+
+        for timeline in &timelines {
+            timeline.maybe_freeze_ephemeral_layer().await;
+        }
+    }
+
    pub fn current_state(&self) -> TenantState {
        self.state.borrow().clone()
    }
@@ -2529,6 +2560,7 @@ impl Tenant {
                &crate::metrics::tenant_throttling::TIMELINE_GET,
            )),
            tenant_conf: Arc::new(ArcSwap::from_pointee(attached_conf)),
+            ongoing_timeline_detach: std::sync::Mutex::default(),
        }
    }

@@ -2812,7 +2844,48 @@ impl Tenant {
        cancel: &CancellationToken,
        ctx: &RequestContext,
    ) -> anyhow::Result<Vec<Arc<Timeline>>> {
-        // grab mutex to prevent new timelines from being created here.
+        // before taking the gc_cs lock, do the heavier weight finding of gc_cutoff points for
+        // currently visible timelines.
+        let timelines = self
+            .timelines
+            .lock()
+            .unwrap()
+            .values()
+            .filter(|tl| match target_timeline_id.as_ref() {
+                Some(target) => &tl.timeline_id == target,
+                None => true,
+            })
+            .cloned()
+            .collect::<Vec<_>>();
+
+        let mut gc_cutoffs: HashMap<TimelineId, GcCutoffs> =
+            HashMap::with_capacity(timelines.len());
+
+        for timeline in timelines.iter() {
+            let cutoff = timeline
+                .get_last_record_lsn()
+                .checked_sub(horizon)
+                .unwrap_or(Lsn(0));
+
+            let res = timeline.find_gc_cutoffs(cutoff, pitr, cancel, ctx).await;
+
+            match res {
+                Ok(cutoffs) => {
+                    let old = gc_cutoffs.insert(timeline.timeline_id, cutoffs);
+                    assert!(old.is_none());
+                }
+                Err(e) => {
+                    tracing::warn!(timeline_id = %timeline.timeline_id, "ignoring failure to find gc cutoffs: {e:#}");
+                }
+            }
+        }
+
+        if !self.is_active() {
+            anyhow::bail!("shutting down");
+        }
+
+        // grab mutex to prevent new timelines from being created here; avoid doing long operations
+        // because that will stall branch creation.
        let gc_cs = self.gc_cs.lock().await;

        // Scan all timelines. For each timeline, remember the timeline ID and
@@ -2874,11 +2947,6 @@ impl Tenant {
                }
            }

-            let cutoff = timeline
-                .get_last_record_lsn()
-                .checked_sub(horizon)
-                .unwrap_or(Lsn(0));
-
            let branchpoints: Vec<Lsn> = all_branchpoints
                .range((
                    Included((timeline_id, Lsn(0))),
@@ -2886,9 +2954,27 @@ impl Tenant {
                ))
                .map(|&x| x.1)
                .collect();
-            timeline
-                .update_gc_info(branchpoints, cutoff, pitr, cancel, ctx)
-                .await?;
+
+            {
+                let mut target = timeline.gc_info.write().unwrap();
+
+                match gc_cutoffs.remove(&timeline_id) {
+                    Some(cutoffs) => {
+                        *target = GcInfo {
+                            retain_lsns: branchpoints,
+                            cutoffs,
+                        };
+                    }
+                    None => {
+                        // reasons for this being unavailable:
+                        // - this timeline was created while we were finding cutoffs
+                        // - lsn for timestamp search fails for this timeline repeatedly
+                        //
+                        // in both cases, refreshing the branchpoints is correct.
+                        target.retain_lsns = branchpoints;
+                    }
+                };
+            }

            gc_timelines.push(timeline);
        }
@@ -2977,7 +3063,7 @@ impl Tenant {
        // and then the planned GC cutoff
        {
            let gc_info = src_timeline.gc_info.read().unwrap();
-            let cutoff = min(gc_info.pitr_cutoff, gc_info.horizon_cutoff);
+            let cutoff = gc_info.min_cutoff();
            if start_lsn < cutoff {
                return Err(CreateTimelineError::AncestorLsn(anyhow::anyhow!(
                    "invalid branch start lsn: less than planned GC cutoff {cutoff}"
@@ -3672,7 +3758,7 @@ pub(crate) mod harness {
                image_layer_creation_check_threshold: Some(
                    tenant_conf.image_layer_creation_check_threshold,
                ),
-                switch_to_aux_file_v2: Some(tenant_conf.switch_to_aux_file_v2),
+                switch_aux_file_policy: Some(tenant_conf.switch_aux_file_policy),
            }
        }
    }
@@ -3871,7 +3957,7 @@ mod tests {
    use crate::DEFAULT_PG_VERSION;
    use bytes::BytesMut;
    use hex_literal::hex;
-    use pageserver_api::key::NON_INHERITED_RANGE;
+    use pageserver_api::key::{AUX_KEY_PREFIX, NON_INHERITED_RANGE};
    use pageserver_api::keyspace::KeySpace;
    use pageserver_api::models::CompactionAlgorithm;
    use rand::{thread_rng, Rng};
@@ -4513,18 +4599,20 @@ mod tests {
    }

    async fn bulk_insert_compact_gc(
-        timeline: Arc<Timeline>,
+        tenant: &Tenant,
+        timeline: &Arc<Timeline>,
        ctx: &RequestContext,
        lsn: Lsn,
        repeat: usize,
        key_count: usize,
    ) -> anyhow::Result<()> {
        let compact = true;
-        bulk_insert_maybe_compact_gc(timeline, ctx, lsn, repeat, key_count, compact).await
+        bulk_insert_maybe_compact_gc(tenant, timeline, ctx, lsn, repeat, key_count, compact).await
    }

    async fn bulk_insert_maybe_compact_gc(
-        timeline: Arc<Timeline>,
+        tenant: &Tenant,
+        timeline: &Arc<Timeline>,
        ctx: &RequestContext,
        mut lsn: Lsn,
        repeat: usize,
@@ -4537,6 +4625,8 @@ mod tests {
        // Enforce that key range is monotonously increasing
        let mut keyspace = KeySpaceAccum::new();

+        let cancel = CancellationToken::new();
+
        for _ in 0..repeat {
            for _ in 0..key_count {
                test_key.field6 = blknum;
@@ -4558,24 +4648,19 @@ mod tests {
                blknum += 1;
            }

-            let cutoff = timeline.get_last_record_lsn();
-
-            timeline
-                .update_gc_info(
-                    Vec::new(),
-                    cutoff,
-                    Duration::ZERO,
-                    &CancellationToken::new(),
-                    ctx,
-                )
-                .await?;
            timeline.freeze_and_flush().await?;
            if compact {
-                timeline
-                    .compact(&CancellationToken::new(), EnumSet::empty(), ctx)
-                    .await?;
+                // this requires timeline to be &Arc<Timeline>
+                timeline.compact(&cancel, EnumSet::empty(), ctx).await?;
            }
-            timeline.gc().await?;
+
+            // this doesn't really need to use the timeline_id target, but it is closer to what it
+            // originally was.
+            let res = tenant
+                .gc_iteration(Some(timeline.timeline_id), 0, Duration::ZERO, &cancel, ctx)
+                .await?;
+
+            assert_eq!(res.layers_removed, 0, "this never removes anything");
        }

        Ok(())
@@ -4594,7 +4679,7 @@ mod tests {
            .await?;

        let lsn = Lsn(0x10);
-        bulk_insert_compact_gc(tline.clone(), &ctx, lsn, 50, 10000).await?;
+        bulk_insert_compact_gc(&tenant, &tline, &ctx, lsn, 50, 10000).await?;

        Ok(())
    }
@@ -4625,7 +4710,7 @@ mod tests {
            .await?;

        let lsn = Lsn(0x10);
-        bulk_insert_compact_gc(tline.clone(), &ctx, lsn, 50, 10000).await?;
+        bulk_insert_compact_gc(&tenant, &tline, &ctx, lsn, 50, 10000).await?;

        let guard = tline.layers.read().await;
        guard.layer_map().dump(true, &ctx).await?;
@@ -4738,15 +4823,7 @@ mod tests {
            .await;

        let images = vectored_res?;
-        let mut key = NON_INHERITED_RANGE.start;
-        while key < NON_INHERITED_RANGE.end {
-            assert!(matches!(
-                images[&key],
-                Err(PageReconstructError::MissingKey(_))
-            ));
-            key = key.next();
-        }
-
+        assert!(images.is_empty());
        Ok(())
    }

@@ -5079,6 +5156,7 @@ mod tests {
            .await?;

        const NUM_KEYS: usize = 1000;
+        let cancel = CancellationToken::new();

        let mut test_key = Key::from_hex("010000000033333333444444445500000000").unwrap();

@@ -5138,18 +5216,10 @@ mod tests {
            }

            // Perform a cycle of flush, and GC
-            let cutoff = tline.get_last_record_lsn();
-            tline
-                .update_gc_info(
-                    Vec::new(),
-                    cutoff,
-                    Duration::ZERO,
-                    &CancellationToken::new(),
-                    &ctx,
-                )
-                .await?;
            tline.freeze_and_flush().await?;
-            tline.gc().await?;
+            tenant
+                .gc_iteration(Some(tline.timeline_id), 0, Duration::ZERO, &cancel, &ctx)
+                .await?;
        }

        Ok(())
@@ -5170,6 +5240,8 @@ mod tests {

        let mut keyspace = KeySpaceAccum::new();

+        let cancel = CancellationToken::new();
+
        // Track when each page was last modified. Used to assert that
        // a read sees the latest page version.
        let mut updated = [Lsn(0); NUM_KEYS];
@@ -5233,21 +5305,11 @@ mod tests {
            }

            // Perform a cycle of flush, compact, and GC
-            let cutoff = tline.get_last_record_lsn();
-            tline
-                .update_gc_info(
-                    Vec::new(),
-                    cutoff,
-                    Duration::ZERO,
-                    &CancellationToken::new(),
-                    &ctx,
-                )
-                .await?;
            tline.freeze_and_flush().await?;
-            tline
-                .compact(&CancellationToken::new(), EnumSet::empty(), &ctx)
+            tline.compact(&cancel, EnumSet::empty(), &ctx).await?;
+            tenant
+                .gc_iteration(Some(tline.timeline_id), 0, Duration::ZERO, &cancel, &ctx)
                .await?;
-            tline.gc().await?;
        }

        Ok(())
@@ -5452,7 +5514,7 @@ mod tests {

        let lsn = Lsn(0x10);
        let compact = false;
-        bulk_insert_maybe_compact_gc(tline.clone(), &ctx, lsn, 50, 10000, compact).await?;
+        bulk_insert_maybe_compact_gc(&tenant, &tline, &ctx, lsn, 50, 10000, compact).await?;

        let test_key = Key::from_hex("010000000033333333444444445500000000").unwrap();
        let read_lsn = Lsn(u64::MAX - 1);
@@ -5462,4 +5524,108 @@ mod tests {

        Ok(())
    }
+
+    #[tokio::test]
+    async fn test_metadata_scan() -> anyhow::Result<()> {
+        let harness = TenantHarness::create("test_metadata_scan")?;
+        let (tenant, ctx) = harness.load().await;
+        let tline = tenant
+            .create_test_timeline(TIMELINE_ID, Lsn(0x10), DEFAULT_PG_VERSION, &ctx)
+            .await?;
+
+        const NUM_KEYS: usize = 1000;
+        const STEP: usize = 100; // random update + scan base_key + idx * STEP
+
+        let cancel = CancellationToken::new();
+
+        let mut base_key = Key::from_hex("000000000033333333444444445500000000").unwrap();
+        base_key.field1 = AUX_KEY_PREFIX;
+        let mut test_key = base_key;
+
+        // Track when each page was last modified. Used to assert that
+        // a read sees the latest page version.
+        let mut updated = [Lsn(0); NUM_KEYS];
+
+        let mut lsn = Lsn(0x10);
+        #[allow(clippy::needless_range_loop)]
+        for blknum in 0..NUM_KEYS {
+            lsn = Lsn(lsn.0 + 0x10);
+            test_key.field6 = (blknum * STEP) as u32;
+            let mut writer = tline.writer().await;
+            writer
+                .put(
+                    test_key,
+                    lsn,
+                    &Value::Image(test_img(&format!("{} at {}", blknum, lsn))),
+                    &ctx,
+                )
+                .await?;
+            writer.finish_write(lsn);
+            updated[blknum] = lsn;
+            drop(writer);
+        }
+
+        let keyspace = KeySpace::single(base_key..base_key.add((NUM_KEYS * STEP) as u32));
+
+        for _ in 0..10 {
+            // Read all the blocks
+            for (blknum, last_lsn) in updated.iter().enumerate() {
+                test_key.field6 = (blknum * STEP) as u32;
+                assert_eq!(
+                    tline.get(test_key, lsn, &ctx).await?,
+                    test_img(&format!("{} at {}", blknum, last_lsn))
+                );
+            }
+
+            let mut cnt = 0;
+            for (key, value) in tline
+                .get_vectored_impl(
+                    keyspace.clone(),
+                    lsn,
+                    ValuesReconstructState::default(),
+                    &ctx,
+                )
+                .await?
+            {
+                let blknum = key.field6 as usize;
+                let value = value?;
+                assert!(blknum % STEP == 0);
+                let blknum = blknum / STEP;
+                assert_eq!(
+                    value,
+                    test_img(&format!("{} at {}", blknum, updated[blknum]))
+                );
+                cnt += 1;
+            }
+
+            assert_eq!(cnt, NUM_KEYS);
+
+            for _ in 0..NUM_KEYS {
+                lsn = Lsn(lsn.0 + 0x10);
+                let blknum = thread_rng().gen_range(0..NUM_KEYS);
+                test_key.field6 = (blknum * STEP) as u32;
+                let mut writer = tline.writer().await;
+                writer
+                    .put(
+                        test_key,
+                        lsn,
+                        &Value::Image(test_img(&format!("{} at {}", blknum, lsn))),
+                        &ctx,
+                    )
+                    .await?;
+                writer.finish_write(lsn);
+                drop(writer);
+                updated[blknum] = lsn;
+            }
+
+            // Perform a cycle of flush, compact, and GC
+            tline.freeze_and_flush().await?;
+            tline.compact(&cancel, EnumSet::empty(), &ctx).await?;
+            tenant
+                .gc_iteration(Some(tline.timeline_id), 0, Duration::ZERO, &cancel, &ctx)
+                .await?;
+        }
+
+        Ok(())
+    }
 }
--- a/pageserver/src/tenant/blob_io.rs
+++ b/pageserver/src/tenant/blob_io.rs
@@ -130,8 +130,9 @@ impl<const BUFFERED: bool> BlobWriter<BUFFERED> {
    async fn write_all_unbuffered<B: BoundedBuf<Buf = Buf>, Buf: IoBuf + Send>(
        &mut self,
        src_buf: B,
+        ctx: &RequestContext,
    ) -> (B::Buf, Result<(), Error>) {
-        let (src_buf, res) = self.inner.write_all(src_buf).await;
+        let (src_buf, res) = self.inner.write_all(src_buf, ctx).await;
        let nbytes = match res {
            Ok(nbytes) => nbytes,
            Err(e) => return (src_buf, Err(e)),
@@ -142,9 +143,9 @@ impl<const BUFFERED: bool> BlobWriter<BUFFERED> {

    #[inline(always)]
    /// Flushes the internal buffer to the underlying `VirtualFile`.
-    pub async fn flush_buffer(&mut self) -> Result<(), Error> {
+    pub async fn flush_buffer(&mut self, ctx: &RequestContext) -> Result<(), Error> {
        let buf = std::mem::take(&mut self.buf);
-        let (mut buf, res) = self.inner.write_all(buf).await;
+        let (mut buf, res) = self.inner.write_all(buf, ctx).await;
        res?;
        buf.clear();
        self.buf = buf;
@@ -165,10 +166,11 @@ impl<const BUFFERED: bool> BlobWriter<BUFFERED> {
    async fn write_all<B: BoundedBuf<Buf = Buf>, Buf: IoBuf + Send>(
        &mut self,
        src_buf: B,
+        ctx: &RequestContext,
    ) -> (B::Buf, Result<(), Error>) {
        if !BUFFERED {
            assert!(self.buf.is_empty());
-            return self.write_all_unbuffered(src_buf).await;
+            return self.write_all_unbuffered(src_buf, ctx).await;
        }
        let remaining = Self::CAPACITY - self.buf.len();
        let src_buf_len = src_buf.bytes_init();
@@ -183,7 +185,7 @@ impl<const BUFFERED: bool> BlobWriter<BUFFERED> {
        }
        // Then, if the buffer is full, flush it out
        if self.buf.len() == Self::CAPACITY {
-            if let Err(e) = self.flush_buffer().await {
+            if let Err(e) = self.flush_buffer(ctx).await {
                return (Slice::into_inner(src_buf), Err(e));
            }
        }
@@ -199,7 +201,7 @@ impl<const BUFFERED: bool> BlobWriter<BUFFERED> {
                assert_eq!(copied, src_buf.len());
                Slice::into_inner(src_buf)
            } else {
-                let (src_buf, res) = self.write_all_unbuffered(src_buf).await;
+                let (src_buf, res) = self.write_all_unbuffered(src_buf, ctx).await;
                if let Err(e) = res {
                    return (src_buf, Err(e));
                }
@@ -216,6 +218,7 @@ impl<const BUFFERED: bool> BlobWriter<BUFFERED> {
    pub async fn write_blob<B: BoundedBuf<Buf = Buf>, Buf: IoBuf + Send>(
        &mut self,
        srcbuf: B,
+        ctx: &RequestContext,
    ) -> (B::Buf, Result<u64, Error>) {
        let offset = self.offset;

@@ -227,7 +230,7 @@ impl<const BUFFERED: bool> BlobWriter<BUFFERED> {
            if len < 128 {
                // Short blob. Write a 1-byte length header
                io_buf.put_u8(len as u8);
-                self.write_all(io_buf).await
+                self.write_all(io_buf, ctx).await
            } else {
                // Write a 4-byte length header
                if len > 0x7fff_ffff {
@@ -242,7 +245,7 @@ impl<const BUFFERED: bool> BlobWriter<BUFFERED> {
                let mut len_buf = (len as u32).to_be_bytes();
                len_buf[0] |= 0x80;
                io_buf.extend_from_slice(&len_buf[..]);
-                self.write_all(io_buf).await
+                self.write_all(io_buf, ctx).await
            }
        }
        .await;
@@ -251,7 +254,7 @@ impl<const BUFFERED: bool> BlobWriter<BUFFERED> {
            Ok(_) => (),
            Err(e) => return (Slice::into_inner(srcbuf.slice(..)), Err(e)),
        }
-        let (srcbuf, res) = self.write_all(srcbuf).await;
+        let (srcbuf, res) = self.write_all(srcbuf, ctx).await;
        (srcbuf, res.map(|_| offset))
    }
 }
@@ -261,8 +264,8 @@ impl BlobWriter<true> {
    ///
    /// This function flushes the internal buffer before giving access
    /// to the underlying `VirtualFile`.
-    pub async fn into_inner(mut self) -> Result<VirtualFile, Error> {
-        self.flush_buffer().await?;
+    pub async fn into_inner(mut self, ctx: &RequestContext) -> Result<VirtualFile, Error> {
+        self.flush_buffer(ctx).await?;
        Ok(self.inner)
    }

@@ -296,22 +299,22 @@ mod tests {
        // Write part (in block to drop the file)
        let mut offsets = Vec::new();
        {
-            let file = VirtualFile::create(pathbuf.as_path()).await?;
+            let file = VirtualFile::create(pathbuf.as_path(), &ctx).await?;
            let mut wtr = BlobWriter::<BUFFERED>::new(file, 0);
            for blob in blobs.iter() {
-                let (_, res) = wtr.write_blob(blob.clone()).await;
+                let (_, res) = wtr.write_blob(blob.clone(), &ctx).await;
                let offs = res?;
                offsets.push(offs);
            }
            // Write out one page worth of zeros so that we can
            // read again with read_blk
-            let (_, res) = wtr.write_blob(vec![0; PAGE_SZ]).await;
+            let (_, res) = wtr.write_blob(vec![0; PAGE_SZ], &ctx).await;
            let offs = res?;
            println!("Writing final blob at offs={offs}");
-            wtr.flush_buffer().await?;
+            wtr.flush_buffer(&ctx).await?;
        }

-        let file = VirtualFile::open(pathbuf.as_path()).await?;
+        let file = VirtualFile::open(pathbuf.as_path(), &ctx).await?;
        let rdr = BlockReaderRef::VirtualFile(&file);
        let rdr = BlockCursor::new(rdr);
        for (idx, (blob, offset)) in blobs.iter().zip(offsets.iter()).enumerate() {
--- a/pageserver/src/tenant/block_io.rs
+++ b/pageserver/src/tenant/block_io.rs
@@ -102,7 +102,7 @@ impl<'a> BlockReaderRef<'a> {
            #[cfg(test)]
            TestDisk(r) => r.read_blk(blknum),
            #[cfg(test)]
-            VirtualFile(r) => r.read_blk(blknum).await,
+            VirtualFile(r) => r.read_blk(blknum, ctx).await,
        }
    }
 }
@@ -177,10 +177,11 @@ impl<'a> FileBlockReader<'a> {
        &self,
        buf: PageWriteGuard<'static>,
        blkno: u32,
+        ctx: &RequestContext,
    ) -> Result<PageWriteGuard<'static>, std::io::Error> {
        assert!(buf.len() == PAGE_SZ);
        self.file
-            .read_exact_at_page(buf, blkno as u64 * PAGE_SZ as u64)
+            .read_exact_at_page(buf, blkno as u64 * PAGE_SZ as u64, ctx)
            .await
    }
    /// Read a block.
@@ -206,7 +207,7 @@ impl<'a> FileBlockReader<'a> {
            ReadBufResult::Found(guard) => Ok(guard.into()),
            ReadBufResult::NotFound(write_guard) => {
                // Read the page from disk into the buffer
-                let write_guard = self.fill_buffer(write_guard, blknum).await?;
+                let write_guard = self.fill_buffer(write_guard, blknum, ctx).await?;
                Ok(write_guard.mark_valid().into())
            }
        }
--- a/pageserver/src/tenant/config.rs
+++ b/pageserver/src/tenant/config.rs
@@ -9,6 +9,7 @@
 //! may lead to a data loss.
 //!
 use anyhow::bail;
+use pageserver_api::models::AuxFilePolicy;
 use pageserver_api::models::CompactionAlgorithm;
 use pageserver_api::models::EvictionPolicy;
 use pageserver_api::models::{self, ThrottleConfig};
@@ -370,9 +371,9 @@ pub struct TenantConf {
    // Expresed in multiples of checkpoint distance.
    pub image_layer_creation_check_threshold: u8,

-    /// Switch to aux file v2. Switching this flag requires the user has not written any aux file into
+    /// Switch to a new aux file policy. Switching this flag requires the user has not written any aux file into
    /// the storage before, and this flag cannot be switched back. Otherwise there will be data corruptions.
-    pub switch_to_aux_file_v2: bool,
+    pub switch_aux_file_policy: AuxFilePolicy,
 }

 /// Same as TenantConf, but this struct preserves the information about
@@ -471,7 +472,7 @@ pub struct TenantConfOpt {

    #[serde(skip_serializing_if = "Option::is_none")]
    #[serde(default)]
-    pub switch_to_aux_file_v2: Option<bool>,
+    pub switch_aux_file_policy: Option<AuxFilePolicy>,
 }

 impl TenantConfOpt {
@@ -529,9 +530,9 @@ impl TenantConfOpt {
            image_layer_creation_check_threshold: self
                .image_layer_creation_check_threshold
                .unwrap_or(global_conf.image_layer_creation_check_threshold),
-            switch_to_aux_file_v2: self
-                .switch_to_aux_file_v2
-                .unwrap_or(global_conf.switch_to_aux_file_v2),
+            switch_aux_file_policy: self
+                .switch_aux_file_policy
+                .unwrap_or(global_conf.switch_aux_file_policy),
        }
    }
 }
@@ -573,7 +574,7 @@ impl Default for TenantConf {
            lazy_slru_download: false,
            timeline_get_throttle: crate::tenant::throttle::Config::disabled(),
            image_layer_creation_check_threshold: DEFAULT_IMAGE_LAYER_CREATION_CHECK_THRESHOLD,
-            switch_to_aux_file_v2: false,
+            switch_aux_file_policy: AuxFilePolicy::V1,
        }
    }
 }
@@ -648,7 +649,7 @@ impl From<TenantConfOpt> for models::TenantConfig {
            lazy_slru_download: value.lazy_slru_download,
            timeline_get_throttle: value.timeline_get_throttle.map(ThrottleConfig::from),
            image_layer_creation_check_threshold: value.image_layer_creation_check_threshold,
-            switch_to_aux_file_v2: value.switch_to_aux_file_v2,
+            switch_aux_file_policy: value.switch_aux_file_policy,
        }
    }
 }
--- a/pageserver/src/tenant/delete.rs
+++ b/pageserver/src/tenant/delete.rs
@@ -585,9 +585,20 @@ impl DeleteTenantFlow {

                    // FIXME: we should not be modifying this from outside of mgr.rs.
                    // This will go away when we simplify deletion (https://github.com/neondatabase/neon/issues/5080)
-                    crate::metrics::TENANT_MANAGER
-                        .tenant_slots
-                        .set(locked.len() as u64);
+
+                    // Update stats
+                    match &removed {
+                        TenantsMapRemoveResult::Occupied(slot) => {
+                            crate::metrics::TENANT_MANAGER.slot_removed(slot);
+                        }
+                        TenantsMapRemoveResult::InProgress(barrier) => {
+                            crate::metrics::TENANT_MANAGER
+                                .slot_removed(&TenantSlot::InProgress(barrier.clone()));
+                        }
+                        TenantsMapRemoveResult::Vacant => {
+                            // Nothing changed in map, no metric update
+                        }
+                    }

                    match removed {
                        TenantsMapRemoveResult::Occupied(TenantSlot::Attached(tenant)) => {
--- a/pageserver/src/tenant/ephemeral_file.rs
+++ b/pageserver/src/tenant/ephemeral_file.rs
@@ -28,6 +28,7 @@ impl EphemeralFile {
        conf: &PageServerConf,
        tenant_shard_id: TenantShardId,
        timeline_id: TimelineId,
+        ctx: &RequestContext,
    ) -> Result<EphemeralFile, io::Error> {
        static NEXT_FILENAME: AtomicU64 = AtomicU64::new(1);
        let filename_disambiguator =
@@ -45,6 +46,7 @@ impl EphemeralFile {
                .read(true)
                .write(true)
                .create(true),
+            ctx,
        )
        .await?;

@@ -74,7 +76,7 @@ impl EphemeralFile {
    pub(crate) async fn write_blob(
        &mut self,
        srcbuf: &[u8],
-        _ctx: &RequestContext,
+        ctx: &RequestContext,
    ) -> Result<u64, io::Error> {
        let pos = self.rw.bytes_written();

@@ -83,15 +85,15 @@ impl EphemeralFile {
            // short one-byte length header
            let len_buf = [srcbuf.len() as u8];

-            self.rw.write_all_borrowed(&len_buf).await?;
+            self.rw.write_all_borrowed(&len_buf, ctx).await?;
        } else {
            let mut len_buf = u32::to_be_bytes(srcbuf.len() as u32);
            len_buf[0] |= 0x80;
-            self.rw.write_all_borrowed(&len_buf).await?;
+            self.rw.write_all_borrowed(&len_buf, ctx).await?;
        }

        // Write the payload
-        self.rw.write_all_borrowed(srcbuf).await?;
+        self.rw.write_all_borrowed(srcbuf, ctx).await?;

        Ok(pos)
    }
@@ -153,7 +155,7 @@ mod tests {
    async fn test_ephemeral_blobs() -> Result<(), io::Error> {
        let (conf, tenant_id, timeline_id, ctx) = harness("ephemeral_blobs")?;

-        let mut file = EphemeralFile::create(conf, tenant_id, timeline_id).await?;
+        let mut file = EphemeralFile::create(conf, tenant_id, timeline_id, &ctx).await?;

        let pos_foo = file.write_blob(b"foo", &ctx).await?;
        assert_eq!(
--- a/pageserver/src/tenant/ephemeral_file/page_caching.rs
+++ b/pageserver/src/tenant/ephemeral_file/page_caching.rs
@@ -35,10 +35,14 @@ impl RW {
        self.page_cache_file_id
    }

-    pub(crate) async fn write_all_borrowed(&mut self, srcbuf: &[u8]) -> Result<usize, io::Error> {
+    pub(crate) async fn write_all_borrowed(
+        &mut self,
+        srcbuf: &[u8],
+        ctx: &RequestContext,
+    ) -> Result<usize, io::Error> {
        // It doesn't make sense to proactively fill the page cache on the Pageserver write path
        // because Compute is unlikely to access recently written data.
-        self.rw.write_all_borrowed(srcbuf).await
+        self.rw.write_all_borrowed(srcbuf, ctx).await
    }

    pub(crate) fn bytes_written(&self) -> u64 {
@@ -74,7 +78,7 @@ impl RW {
                    page_cache::ReadBufResult::NotFound(write_guard) => {
                        let write_guard = writer
                            .file
-                            .read_exact_at_page(write_guard, blknum as u64 * PAGE_SZ as u64)
+                            .read_exact_at_page(write_guard, blknum as u64 * PAGE_SZ as u64, ctx)
                            .await?;
                        let read_guard = write_guard.mark_valid();
                        return Ok(BlockLease::PageReadGuard(read_guard));
@@ -134,6 +138,7 @@ impl crate::virtual_file::owned_buffers_io::write::OwnedAsyncWriter for PreWarmi
    >(
        &mut self,
        buf: B,
+        ctx: &RequestContext,
    ) -> std::io::Result<(usize, B::Buf)> {
        let buf = buf.slice(..);
        let saved_bounds = buf.bounds(); // save for reconstructing the Slice from iobuf after the IO is done
@@ -150,7 +155,7 @@ impl crate::virtual_file::owned_buffers_io::write::OwnedAsyncWriter for PreWarmi
        );

        // Do the IO.
-        let iobuf = match self.file.write_all(buf).await {
+        let iobuf = match self.file.write_all(buf, ctx).await {
            (iobuf, Ok(nwritten)) => {
                assert_eq!(nwritten, buflen);
                iobuf
--- a/pageserver/src/tenant/ephemeral_file/zero_padded_read_write.rs
+++ b/pageserver/src/tenant/ephemeral_file/zero_padded_read_write.rs
@@ -20,6 +20,7 @@
 mod zero_padded;

 use crate::{
+    context::RequestContext,
    page_cache::PAGE_SZ,
    virtual_file::owned_buffers_io::{
        self,
@@ -60,8 +61,12 @@ where
        self.buffered_writer.as_inner().as_inner()
    }

-    pub async fn write_all_borrowed(&mut self, buf: &[u8]) -> std::io::Result<usize> {
-        self.buffered_writer.write_buffered_borrowed(buf).await
+    pub async fn write_all_borrowed(
+        &mut self,
+        buf: &[u8],
+        ctx: &RequestContext,
+    ) -> std::io::Result<usize> {
+        self.buffered_writer.write_buffered_borrowed(buf, ctx).await
    }

    pub fn bytes_written(&self) -> u64 {
--- a/pageserver/src/tenant/layer_map.rs
+++ b/pageserver/src/tenant/layer_map.rs
@@ -588,7 +588,7 @@ impl LayerMap {
            let kr = Key::from_i128(current_key)..Key::from_i128(change_key);
            coverage.push((kr, current_val.take()));
            current_key = change_key;
-            current_val = change_val.clone();
+            current_val.clone_from(&change_val);
        }

        // Add the final interval
@@ -672,12 +672,12 @@ impl LayerMap {
        // Loop through the delta coverage and recurse on each part
        for (change_key, change_val) in version.delta_coverage.range(start..end) {
            // If there's a relevant delta in this part, add 1 and recurse down
-            if let Some(val) = current_val {
+            if let Some(val) = &current_val {
                if val.get_lsn_range().end > lsn.start {
                    let kr = Key::from_i128(current_key)..Key::from_i128(change_key);
                    let lr = lsn.start..val.get_lsn_range().start;
                    if !kr.is_empty() {
-                        let base_count = Self::is_reimage_worthy(&val, key) as usize;
+                        let base_count = Self::is_reimage_worthy(val, key) as usize;
                        let new_limit = limit.map(|l| l - base_count);
                        let max_stacked_deltas_underneath = self.count_deltas(&kr, &lr, new_limit);
                        max_stacked_deltas = std::cmp::max(
@@ -689,17 +689,17 @@ impl LayerMap {
            }

            current_key = change_key;
-            current_val = change_val.clone();
+            current_val.clone_from(&change_val);
        }

        // Consider the last part
-        if let Some(val) = current_val {
+        if let Some(val) = &current_val {
            if val.get_lsn_range().end > lsn.start {
                let kr = Key::from_i128(current_key)..Key::from_i128(end);
                let lr = lsn.start..val.get_lsn_range().start;

                if !kr.is_empty() {
-                    let base_count = Self::is_reimage_worthy(&val, key) as usize;
+                    let base_count = Self::is_reimage_worthy(val, key) as usize;
                    let new_limit = limit.map(|l| l - base_count);
                    let max_stacked_deltas_underneath = self.count_deltas(&kr, &lr, new_limit);
                    max_stacked_deltas = std::cmp::max(
--- a/pageserver/src/tenant/metadata.rs
+++ b/pageserver/src/tenant/metadata.rs
@@ -207,6 +207,24 @@ impl TimelineMetadata {
        self.body.ancestor_lsn
    }

+    /// When reparenting, the `ancestor_lsn` does not change.
+    pub fn reparent(&mut self, timeline: &TimelineId) {
+        assert!(self.body.ancestor_timeline.is_some());
+        // no assertion for redoing this: it's fine, we may have to repeat this multiple times over
+        self.body.ancestor_timeline = Some(*timeline);
+    }
+
+    pub fn detach_from_ancestor(&mut self, branchpoint: &(TimelineId, Lsn)) {
+        if let Some(ancestor) = self.body.ancestor_timeline {
+            assert_eq!(ancestor, branchpoint.0);
+        }
+        if self.body.ancestor_lsn != Lsn(0) {
+            assert_eq!(self.body.ancestor_lsn, branchpoint.1);
+        }
+        self.body.ancestor_timeline = None;
+        self.body.ancestor_lsn = Lsn(0);
+    }
+
    pub fn latest_gc_cutoff_lsn(&self) -> Lsn {
        self.body.latest_gc_cutoff_lsn
    }
--- a/pageserver/src/tenant/mgr.rs
+++ b/pageserver/src/tenant/mgr.rs
@@ -56,6 +56,7 @@ use utils::id::{TenantId, TimelineId};

 use super::delete::DeleteTenantError;
 use super::secondary::SecondaryTenant;
+use super::timeline::detach_ancestor::PreparedTimelineDetach;
 use super::TenantSharedResources;

 /// For a tenant that appears in TenantsMap, it may either be
@@ -246,6 +247,7 @@ impl TenantsMap {
        }
    }

+    #[cfg(all(debug_assertions, not(test)))]
    pub(crate) fn len(&self) -> usize {
        match self {
            TenantsMap::Initializing => 0,
@@ -746,6 +748,7 @@ pub async fn init_tenant_mgr(
            }
        };

+        METRICS.slot_inserted(&slot);
        tenants.insert(tenant_shard_id, slot);
    }

@@ -753,7 +756,7 @@ pub async fn init_tenant_mgr(

    let mut tenants_map = TENANTS.write().unwrap();
    assert!(matches!(&*tenants_map, &TenantsMap::Initializing));
-    METRICS.tenant_slots.set(tenants.len() as u64);
+
    *tenants_map = TenantsMap::Open(tenants);

    Ok(TenantManager {
@@ -824,6 +827,14 @@ fn tenant_spawn(
 async fn shutdown_all_tenants0(tenants: &std::sync::RwLock<TenantsMap>) {
    let mut join_set = JoinSet::new();

+    #[cfg(all(debug_assertions, not(test)))]
+    {
+        // Check that our metrics properly tracked the size of the tenants map.  This is a convenient location to check,
+        // as it happens implicitly at the end of tests etc.
+        let m = tenants.read().unwrap();
+        debug_assert_eq!(METRICS.slots_total(), m.len() as u64);
+    }
+
    // Atomically, 1. create the shutdown tasks and 2. prevent creation of new tenants.
    let (total_in_progress, total_attached) = {
        let mut m = tenants.write().unwrap();
@@ -1997,6 +2008,101 @@ impl TenantManager {
            })
            .collect())
    }
+
+    /// Completes an earlier prepared timeline detach ancestor.
+    pub(crate) async fn complete_detaching_timeline_ancestor(
+        &self,
+        tenant_shard_id: TenantShardId,
+        timeline_id: TimelineId,
+        prepared: PreparedTimelineDetach,
+        ctx: &RequestContext,
+    ) -> Result<Vec<TimelineId>, anyhow::Error> {
+        struct RevertOnDropSlot(Option<SlotGuard>);
+
+        impl Drop for RevertOnDropSlot {
+            fn drop(&mut self) {
+                if let Some(taken) = self.0.take() {
+                    taken.revert();
+                }
+            }
+        }
+
+        impl RevertOnDropSlot {
+            fn into_inner(mut self) -> SlotGuard {
+                self.0.take().unwrap()
+            }
+        }
+
+        impl std::ops::Deref for RevertOnDropSlot {
+            type Target = SlotGuard;
+
+            fn deref(&self) -> &Self::Target {
+                self.0.as_ref().unwrap()
+            }
+        }
+
+        let slot_guard = tenant_map_acquire_slot(&tenant_shard_id, TenantSlotAcquireMode::Any)?;
+        let slot_guard = RevertOnDropSlot(Some(slot_guard));
+
+        let tenant = {
+            let Some(old_slot) = slot_guard.get_old_value() else {
+                anyhow::bail!(
+                    "Tenant not found when trying to complete detaching timeline ancestor"
+                );
+            };
+
+            let Some(tenant) = old_slot.get_attached() else {
+                anyhow::bail!("Tenant is not in attached state");
+            };
+
+            if !tenant.is_active() {
+                anyhow::bail!("Tenant is not active");
+            }
+
+            tenant.clone()
+        };
+
+        let timeline = tenant.get_timeline(timeline_id, true)?;
+
+        let reparented = timeline
+            .complete_detaching_timeline_ancestor(&tenant, prepared, ctx)
+            .await?;
+
+        let mut slot_guard = slot_guard.into_inner();
+
+        let (_guard, progress) = utils::completion::channel();
+        match tenant.shutdown(progress, ShutdownMode::Hard).await {
+            Ok(()) => {
+                slot_guard.drop_old_value()?;
+            }
+            Err(_barrier) => {
+                slot_guard.revert();
+                // this really should not happen, at all, unless shutdown was already going?
+                anyhow::bail!("Cannot restart Tenant, already shutting down");
+            }
+        }
+
+        let tenant_path = self.conf.tenant_path(&tenant_shard_id);
+        let config = Tenant::load_tenant_config(self.conf, &tenant_shard_id)?;
+
+        let shard_identity = config.shard;
+        let tenant = tenant_spawn(
+            self.conf,
+            tenant_shard_id,
+            &tenant_path,
+            self.resources.clone(),
+            AttachedTenantConf::try_from(config)?,
+            shard_identity,
+            None,
+            self.tenants,
+            SpawnMode::Eager,
+            ctx,
+        )?;
+
+        slot_guard.upsert(TenantSlot::Attached(tenant))?;
+
+        Ok(reparented)
+    }
 }

 #[derive(Debug, thiserror::Error)]
@@ -2428,10 +2534,13 @@ impl SlotGuard {
                TenantsMap::Open(m) => m,
            };

+            METRICS.slot_inserted(&new_value);
+
            let replaced = m.insert(self.tenant_shard_id, new_value);
            self.upserted = true;
-
-            METRICS.tenant_slots.set(m.len() as u64);
+            if let Some(replaced) = replaced.as_ref() {
+                METRICS.slot_removed(replaced);
+            }

            replaced
        };
@@ -2541,9 +2650,13 @@ impl Drop for SlotGuard {
                }

                if self.old_value_is_shutdown() {
+                    METRICS.slot_removed(entry.get());
                    entry.remove();
                } else {
-                    entry.insert(self.old_value.take().unwrap());
+                    let inserting = self.old_value.take().unwrap();
+                    METRICS.slot_inserted(&inserting);
+                    let replaced = entry.insert(inserting);
+                    METRICS.slot_removed(&replaced);
                }
            }
            Entry::Vacant(_) => {
@@ -2554,8 +2667,6 @@ impl Drop for SlotGuard {
                );
            }
        }
-
-        METRICS.tenant_slots.set(m.len() as u64);
    }
 }

@@ -2635,7 +2746,9 @@ fn tenant_map_acquire_slot_impl(
            }
            _ => {
                let (completion, barrier) = utils::completion::channel();
-                v.insert(TenantSlot::InProgress(barrier));
+                let inserting = TenantSlot::InProgress(barrier);
+                METRICS.slot_inserted(&inserting);
+                v.insert(inserting);
                tracing::debug!("Vacant, inserted InProgress");
                Ok(SlotGuard::new(*tenant_shard_id, None, completion))
            }
@@ -2671,7 +2784,10 @@ fn tenant_map_acquire_slot_impl(
                _ => {
                    // Happy case: the slot was not in any state that violated our mode
                    let (completion, barrier) = utils::completion::channel();
-                    let old_value = o.insert(TenantSlot::InProgress(barrier));
+                    let in_progress = TenantSlot::InProgress(barrier);
+                    METRICS.slot_inserted(&in_progress);
+                    let old_value = o.insert(in_progress);
+                    METRICS.slot_removed(&old_value);
                    tracing::debug!("Occupied, replaced with InProgress");
                    Ok(SlotGuard::new(
                        *tenant_shard_id,
--- a/pageserver/src/tenant/remote_timeline_client.rs
+++ b/pageserver/src/tenant/remote_timeline_client.rs
@@ -210,6 +210,7 @@ use tracing::{debug, error, info, instrument, warn};
 use tracing::{info_span, Instrument};
 use utils::lsn::Lsn;

+use crate::context::RequestContext;
 use crate::deletion_queue::{DeletionQueueClient, DeletionQueueError};
 use crate::metrics::{
    MeasureRemoteOp, RemoteOpFileKind, RemoteOpKind, RemoteTimelineClientMetrics,
@@ -239,7 +240,7 @@ use utils::id::{TenantId, TimelineId};
 use self::index::IndexPart;

 use super::metadata::MetadataUpdate;
-use super::storage_layer::{Layer, LayerFileName, ResidentLayer};
+use super::storage_layer::{Layer, LayerName, ResidentLayer};
 use super::upload_queue::SetDeletedFlagProgress;
 use super::Generation;

@@ -436,6 +437,19 @@ impl RemoteTimelineClient {
        }
    }

+    /// Returns true if this timeline was previously detached at this Lsn and the remote timeline
+    /// client is currently initialized.
+    pub(crate) fn is_previous_ancestor_lsn(&self, lsn: Lsn) -> bool {
+        // technically this is a dirty read, but given how timeline detach ancestor is implemented
+        // via tenant restart, the lineage has always been uploaded.
+        self.upload_queue
+            .lock()
+            .unwrap()
+            .initialized_mut()
+            .map(|uq| uq.latest_lineage.is_previous_ancestor_lsn(lsn))
+            .unwrap_or(false)
+    }
+
    fn update_remote_physical_size_gauge(&self, current_remote_index_part: Option<&IndexPart>) {
        let size: u64 = if let Some(current_remote_index_part) = current_remote_index_part {
            current_remote_index_part
@@ -502,9 +516,10 @@ impl RemoteTimelineClient {
    /// On success, returns the size of the downloaded file.
    pub async fn download_layer_file(
        &self,
-        layer_file_name: &LayerFileName,
+        layer_file_name: &LayerName,
        layer_metadata: &LayerFileMetadata,
        cancel: &CancellationToken,
+        ctx: &RequestContext,
    ) -> anyhow::Result<u64> {
        let downloaded_size = {
            let _unfinished_gauge_guard = self.metrics.call_begin(
@@ -522,6 +537,7 @@ impl RemoteTimelineClient {
                layer_file_name,
                layer_metadata,
                cancel,
+                ctx,
            )
            .measure_remote_op(
                RemoteOpFileKind::Layer,
@@ -567,7 +583,7 @@ impl RemoteTimelineClient {
        // ahead of what's _actually_ on the remote during index upload.
        upload_queue.latest_metadata = metadata.clone();

-        self.schedule_index_upload(upload_queue, upload_queue.latest_metadata.clone());
+        self.schedule_index_upload(upload_queue);

        Ok(())
    }
@@ -588,7 +604,7 @@ impl RemoteTimelineClient {

        upload_queue.latest_metadata.apply(update);

-        self.schedule_index_upload(upload_queue, upload_queue.latest_metadata.clone());
+        self.schedule_index_upload(upload_queue);

        Ok(())
    }
@@ -608,18 +624,14 @@ impl RemoteTimelineClient {
        let upload_queue = guard.initialized_mut()?;

        if upload_queue.latest_files_changes_since_metadata_upload_scheduled > 0 {
-            self.schedule_index_upload(upload_queue, upload_queue.latest_metadata.clone());
+            self.schedule_index_upload(upload_queue);
        }

        Ok(())
    }

    /// Launch an index-file upload operation in the background (internal function)
-    fn schedule_index_upload(
-        self: &Arc<Self>,
-        upload_queue: &mut UploadQueueInitialized,
-        metadata: TimelineMetadata,
-    ) {
+    fn schedule_index_upload(self: &Arc<Self>, upload_queue: &mut UploadQueueInitialized) {
        let disk_consistent_lsn = upload_queue.latest_metadata.disk_consistent_lsn();

        info!(
@@ -628,12 +640,8 @@ impl RemoteTimelineClient {
            upload_queue.latest_files_changes_since_metadata_upload_scheduled,
        );

-        let index_part = IndexPart::new(
-            upload_queue.latest_files.clone(),
-            disk_consistent_lsn,
-            metadata,
-        );
-        let op = UploadOp::UploadMetadata(index_part, disk_consistent_lsn);
+        let index_part = IndexPart::from(&*upload_queue);
+        let op = UploadOp::UploadMetadata(Box::new(index_part), disk_consistent_lsn);
        self.metric_begin(&op);
        upload_queue.queued_operations.push_back(op);
        upload_queue.latest_files_changes_since_metadata_upload_scheduled = 0;
@@ -642,9 +650,67 @@ impl RemoteTimelineClient {
        self.launch_queued_tasks(upload_queue);
    }

+    pub(crate) async fn schedule_reparenting_and_wait(
+        self: &Arc<Self>,
+        new_parent: &TimelineId,
+    ) -> anyhow::Result<()> {
+        // FIXME: because of how Timeline::schedule_uploads works when called from layer flushing
+        // and reads the in-memory part we cannot do the detaching like this
+        let receiver = {
+            let mut guard = self.upload_queue.lock().unwrap();
+            let upload_queue = guard.initialized_mut()?;
+
+            let Some(prev) = upload_queue.latest_metadata.ancestor_timeline() else {
+                return Err(anyhow::anyhow!(
+                    "cannot reparent without a current ancestor"
+                ));
+            };
+
+            upload_queue.latest_metadata.reparent(new_parent);
+            upload_queue.latest_lineage.record_previous_ancestor(&prev);
+
+            self.schedule_index_upload(upload_queue);
+
+            self.schedule_barrier0(upload_queue)
+        };
+
+        Self::wait_completion0(receiver).await
+    }
+
+    /// Schedules uploading a new version of `index_part.json` with the given layers added,
+    /// detaching from ancestor and waits for it to complete.
    ///
-    /// Launch an upload operation in the background.
-    ///
+    /// This is used with `Timeline::detach_ancestor` functionality.
+    pub(crate) async fn schedule_adding_existing_layers_to_index_detach_and_wait(
+        self: &Arc<Self>,
+        layers: &[Layer],
+        adopted: (TimelineId, Lsn),
+    ) -> anyhow::Result<()> {
+        let barrier = {
+            let mut guard = self.upload_queue.lock().unwrap();
+            let upload_queue = guard.initialized_mut()?;
+
+            upload_queue.latest_metadata.detach_from_ancestor(&adopted);
+            upload_queue.latest_lineage.record_detaching(&adopted);
+
+            for layer in layers {
+                upload_queue
+                    .latest_files
+                    .insert(layer.layer_desc().layer_name(), layer.metadata());
+            }
+
+            self.schedule_index_upload(upload_queue);
+
+            let barrier = self.schedule_barrier0(upload_queue);
+            self.launch_queued_tasks(upload_queue);
+            barrier
+        };
+
+        Self::wait_completion0(barrier).await
+    }
+
+    /// Launch an upload operation in the background; the file is added to be included in next
+    /// `index_part.json` upload.
    pub(crate) fn schedule_layer_file_upload(
        self: &Arc<Self>,
        layer: ResidentLayer,
@@ -666,13 +732,15 @@ impl RemoteTimelineClient {

        upload_queue
            .latest_files
-            .insert(layer.layer_desc().filename(), metadata.clone());
+            .insert(layer.layer_desc().layer_name(), metadata.clone());
        upload_queue.latest_files_changes_since_metadata_upload_scheduled += 1;

        info!(
-            "scheduled layer file upload {layer} gen={:?} shard={:?}",
-            metadata.generation, metadata.shard
+            gen=?metadata.generation,
+            shard=?metadata.shard,
+            "scheduled layer file upload {layer}",
        );
+
        let op = UploadOp::UploadLayer(layer, metadata);
        self.metric_begin(&op);
        upload_queue.queued_operations.push_back(op);
@@ -688,7 +756,7 @@ impl RemoteTimelineClient {
    /// successfully.
    pub fn schedule_layer_file_deletion(
        self: &Arc<Self>,
-        names: &[LayerFileName],
+        names: &[LayerName],
    ) -> anyhow::Result<()> {
        let mut guard = self.upload_queue.lock().unwrap();
        let upload_queue = guard.initialized_mut()?;
@@ -716,7 +784,7 @@ impl RemoteTimelineClient {
        // the layer files as "dangling". this is fine, at worst case we create work for the
        // scrubber.

-        let names = gc_layers.iter().map(|x| x.layer_desc().filename());
+        let names = gc_layers.iter().map(|x| x.layer_desc().layer_name());

        self.schedule_unlinking_of_layers_from_index_part0(upload_queue, names);

@@ -731,14 +799,10 @@ impl RemoteTimelineClient {
        self: &Arc<Self>,
        upload_queue: &mut UploadQueueInitialized,
        names: I,
-    ) -> Vec<(LayerFileName, LayerFileMetadata)>
+    ) -> Vec<(LayerName, LayerFileMetadata)>
    where
-        I: IntoIterator<Item = LayerFileName>,
+        I: IntoIterator<Item = LayerName>,
    {
-        // Deleting layers doesn't affect the values stored in TimelineMetadata,
-        // so we don't need update it. Just serialize it.
-        let metadata = upload_queue.latest_metadata.clone();
-
        // Decorate our list of names with each name's metadata, dropping
        // names that are unexpectedly missing from our metadata.  This metadata
        // is later used when physically deleting layers, to construct key paths.
@@ -777,7 +841,7 @@ impl RemoteTimelineClient {
        // index_part update, because that needs to be uploaded before we can actually delete the
        // files.
        if upload_queue.latest_files_changes_since_metadata_upload_scheduled > 0 {
-            self.schedule_index_upload(upload_queue, metadata);
+            self.schedule_index_upload(upload_queue);
        }

        with_metadata
@@ -787,7 +851,7 @@ impl RemoteTimelineClient {
    /// `index_part.json` with [`Self::schedule_gc_update`] or [`Self::schedule_compaction_update`].
    pub(crate) fn schedule_deletion_of_unlinked(
        self: &Arc<Self>,
-        layers: Vec<(LayerFileName, LayerFileMetadata)>,
+        layers: Vec<(LayerName, LayerFileMetadata)>,
    ) -> anyhow::Result<()> {
        let mut guard = self.upload_queue.lock().unwrap();
        let upload_queue = guard.initialized_mut()?;
@@ -800,7 +864,7 @@ impl RemoteTimelineClient {
    fn schedule_deletion_of_unlinked0(
        self: &Arc<Self>,
        upload_queue: &mut UploadQueueInitialized,
-        mut with_metadata: Vec<(LayerFileName, LayerFileMetadata)>,
+        mut with_metadata: Vec<(LayerName, LayerFileMetadata)>,
    ) {
        // Filter out any layers which were not created by this tenant shard.  These are
        // layers that originate from some ancestor shard after a split, and may still
@@ -869,7 +933,7 @@ impl RemoteTimelineClient {
            self.schedule_layer_file_upload0(upload_queue, layer.clone());
        }

-        let names = compacted_from.iter().map(|x| x.layer_desc().filename());
+        let names = compacted_from.iter().map(|x| x.layer_desc().layer_name());

        self.schedule_unlinking_of_layers_from_index_part0(upload_queue, names);
        self.launch_queued_tasks(upload_queue);
@@ -879,12 +943,18 @@ impl RemoteTimelineClient {

    /// Wait for all previously scheduled uploads/deletions to complete
    pub(crate) async fn wait_completion(self: &Arc<Self>) -> anyhow::Result<()> {
-        let mut receiver = {
+        let receiver = {
            let mut guard = self.upload_queue.lock().unwrap();
            let upload_queue = guard.initialized_mut()?;
            self.schedule_barrier0(upload_queue)
        };

+        Self::wait_completion0(receiver).await
+    }
+
+    async fn wait_completion0(
+        mut receiver: tokio::sync::watch::Receiver<()>,
+    ) -> anyhow::Result<()> {
        if receiver.changed().await.is_err() {
            anyhow::bail!("wait_completion aborted because upload queue was stopped");
        }
@@ -1000,8 +1070,7 @@ impl RemoteTimelineClient {
            let deleted_at = Utc::now().naive_utc();
            stopped.deleted_at = SetDeletedFlagProgress::InProgress(deleted_at);

-            let mut index_part = IndexPart::try_from(&stopped.upload_queue_for_deletion)
-                .context("IndexPart serialize")?;
+            let mut index_part = IndexPart::from(&stopped.upload_queue_for_deletion);
            index_part.deleted_at = Some(deleted_at);
            index_part
        };
@@ -1082,6 +1151,93 @@ impl RemoteTimelineClient {
        Ok(())
    }

+    /// Uploads the given layer **without** adding it to be part of a future `index_part.json` upload.
+    ///
+    /// This is not normally needed.
+    pub(crate) async fn upload_layer_file(
+        self: &Arc<Self>,
+        uploaded: &ResidentLayer,
+        cancel: &CancellationToken,
+    ) -> anyhow::Result<()> {
+        let remote_path = remote_layer_path(
+            &self.tenant_shard_id.tenant_id,
+            &self.timeline_id,
+            self.tenant_shard_id.to_index(),
+            &uploaded.layer_desc().layer_name(),
+            uploaded.metadata().generation,
+        );
+
+        backoff::retry(
+            || async {
+                upload::upload_timeline_layer(
+                    &self.storage_impl,
+                    uploaded.local_path(),
+                    &remote_path,
+                    uploaded.metadata().file_size(),
+                    cancel,
+                )
+                .await
+            },
+            TimeoutOrCancel::caused_by_cancel,
+            FAILED_UPLOAD_WARN_THRESHOLD,
+            FAILED_REMOTE_OP_RETRIES,
+            "upload a layer without adding it to latest files",
+            cancel,
+        )
+        .await
+        .ok_or_else(|| anyhow::Error::new(TimeoutOrCancel::Cancel))
+        .and_then(|x| x)
+        .context("upload a layer without adding it to latest files")
+    }
+
+    /// Copies the `adopted` remote existing layer to the remote path of `adopted_as`. The layer is
+    /// not added to be part of a future `index_part.json` upload.
+    pub(crate) async fn copy_timeline_layer(
+        self: &Arc<Self>,
+        adopted: &Layer,
+        adopted_as: &Layer,
+        cancel: &CancellationToken,
+    ) -> anyhow::Result<()> {
+        let source_remote_path = remote_layer_path(
+            &self.tenant_shard_id.tenant_id,
+            &adopted
+                .get_timeline_id()
+                .expect("Source timeline should be alive"),
+            self.tenant_shard_id.to_index(),
+            &adopted.layer_desc().layer_name(),
+            adopted.metadata().generation,
+        );
+
+        let target_remote_path = remote_layer_path(
+            &self.tenant_shard_id.tenant_id,
+            &self.timeline_id,
+            self.tenant_shard_id.to_index(),
+            &adopted_as.layer_desc().layer_name(),
+            adopted_as.metadata().generation,
+        );
+
+        backoff::retry(
+            || async {
+                upload::copy_timeline_layer(
+                    &self.storage_impl,
+                    &source_remote_path,
+                    &target_remote_path,
+                    cancel,
+                )
+                .await
+            },
+            TimeoutOrCancel::caused_by_cancel,
+            FAILED_UPLOAD_WARN_THRESHOLD,
+            FAILED_REMOTE_OP_RETRIES,
+            "copy timeline layer",
+            cancel,
+        )
+        .await
+        .ok_or_else(|| anyhow::Error::new(TimeoutOrCancel::Cancel))
+        .and_then(|x| x)
+        .context("remote copy timeline layer")
+    }
+
    async fn flush_deletion_queue(&self) -> Result<(), DeletionQueueError> {
        match tokio::time::timeout(
            DELETION_QUEUE_FLUSH_TIMEOUT,
@@ -1253,7 +1409,7 @@ impl RemoteTimelineClient {
        while let Some(next_op) = upload_queue.queued_operations.front() {
            // Can we run this task now?
            let can_run_now = match next_op {
-                UploadOp::UploadLayer(_, _) => {
+                UploadOp::UploadLayer(..) => {
                    // Can always be scheduled.
                    true
                }
@@ -1380,13 +1536,25 @@ impl RemoteTimelineClient {

            let upload_result: anyhow::Result<()> = match &task.op {
                UploadOp::UploadLayer(ref layer, ref layer_metadata) => {
-                    let path = layer.local_path();
+                    let local_path = layer.local_path();
+
+                    // We should only be uploading layers created by this `Tenant`'s lifetime, so
+                    // the metadata in the upload should always match our current generation.
+                    assert_eq!(layer_metadata.generation, self.generation);
+
+                    let remote_path = remote_layer_path(
+                        &self.tenant_shard_id.tenant_id,
+                        &self.timeline_id,
+                        layer_metadata.shard,
+                        &layer.layer_desc().layer_name(),
+                        layer_metadata.generation,
+                    );
+
                    upload::upload_timeline_layer(
-                        self.conf,
                        &self.storage_impl,
-                        path,
-                        layer_metadata,
-                        self.generation,
+                        local_path,
+                        &remote_path,
+                        layer_metadata.file_size(),
                        &self.cancel,
                    )
                    .measure_remote_op(
@@ -1662,6 +1830,7 @@ impl RemoteTimelineClient {
                        latest_files: initialized.latest_files.clone(),
                        latest_files_changes_since_metadata_upload_scheduled: 0,
                        latest_metadata: initialized.latest_metadata.clone(),
+                        latest_lineage: initialized.latest_lineage.clone(),
                        projected_remote_consistent_lsn: None,
                        visible_remote_consistent_lsn: initialized
                            .visible_remote_consistent_lsn
@@ -1747,14 +1916,14 @@ pub fn remote_layer_path(
    tenant_id: &TenantId,
    timeline_id: &TimelineId,
    shard: ShardIndex,
-    layer_file_name: &LayerFileName,
+    layer_file_name: &LayerName,
    generation: Generation,
 ) -> RemotePath {
    // Generation-aware key format
    let path = format!(
        "tenants/{tenant_id}{0}/{TIMELINES_SEGMENT_NAME}/{timeline_id}/{1}{2}",
        shard.get_suffix(),
-        layer_file_name.file_name(),
+        layer_file_name,
        generation.get_suffix()
    );

@@ -1815,29 +1984,6 @@ pub fn parse_remote_index_path(path: RemotePath) -> Option<Generation> {
    }
 }

-/// Files on the remote storage are stored with paths, relative to the workdir.
-/// That path includes in itself both tenant and timeline ids, allowing to have a unique remote storage path.
-///
-/// Errors if the path provided does not start from pageserver's workdir.
-pub fn remote_path(
-    conf: &PageServerConf,
-    local_path: &Utf8Path,
-    generation: Generation,
-) -> anyhow::Result<RemotePath> {
-    let stripped = local_path
-        .strip_prefix(&conf.workdir)
-        .context("Failed to strip workdir prefix")?;
-
-    let suffixed = format!("{0}{1}", stripped, generation.get_suffix());
-
-    RemotePath::new(Utf8Path::new(&suffixed)).with_context(|| {
-        format!(
-            "to resolve remote part of path {:?} for base {:?}",
-            local_path, conf.workdir
-        )
-    })
-}
-
 #[cfg(test)]
 mod tests {
    use super::*;
@@ -1845,6 +1991,7 @@ mod tests {
        context::RequestContext,
        tenant::{
            harness::{TenantHarness, TIMELINE_ID},
+            storage_layer::layer::local_layer_path,
            Tenant, Timeline,
        },
        DEFAULT_PG_VERSION,
@@ -1873,8 +2020,8 @@ mod tests {
        TimelineMetadata::from_bytes(&metadata.to_bytes().unwrap()).unwrap()
    }

-    fn assert_file_list(a: &HashSet<LayerFileName>, b: &[&str]) {
-        let mut avec: Vec<String> = a.iter().map(|x| x.file_name()).collect();
+    fn assert_file_list(a: &HashSet<LayerName>, b: &[&str]) {
+        let mut avec: Vec<String> = a.iter().map(|x| x.to_string()).collect();
        avec.sort();

        let mut bvec = b.to_vec();
@@ -2000,7 +2147,7 @@ mod tests {
            .layer_metadata
            .keys()
            .map(|f| f.to_owned())
-            .collect::<HashSet<LayerFileName>>();
+            .collect::<HashSet<LayerName>>();
        let initial_layer = {
            assert!(initial_layers.len() == 1);
            initial_layers.into_iter().next().unwrap()
@@ -2026,12 +2173,21 @@ mod tests {
            ("000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000016B59DA-00000000016B5A53".parse().unwrap(), dummy_contents("baz"))
        ]
        .into_iter()
-        .map(|(name, contents): (LayerFileName, Vec<u8>)| {
-            std::fs::write(timeline_path.join(name.file_name()), &contents).unwrap();
+        .map(|(name, contents): (LayerName, Vec<u8>)| {
+
+            let local_path = local_layer_path(
+                harness.conf,
+                &timeline.tenant_shard_id,
+                &timeline.timeline_id,
+                &name,
+                &generation,
+            );
+            std::fs::write(&local_path, &contents).unwrap();

            Layer::for_resident(
                harness.conf,
                &timeline,
+                local_path,
                name,
                LayerFileMetadata::new(contents.len() as u64, generation, shard),
            )
@@ -2098,9 +2254,9 @@ mod tests {
                .map(|f| f.to_owned())
                .collect(),
            &[
-                &initial_layer.file_name(),
-                &layers[0].layer_desc().filename().file_name(),
-                &layers[1].layer_desc().filename().file_name(),
+                &initial_layer.to_string(),
+                &layers[0].layer_desc().layer_name().to_string(),
+                &layers[1].layer_desc().layer_name().to_string(),
            ],
        );
        assert_eq!(index_part.metadata, metadata);
@@ -2114,7 +2270,7 @@ mod tests {
        // keep using schedule_layer_file_deletion because we don't have a way to wait for the
        // spawn_blocking started by the drop.
        client
-            .schedule_layer_file_deletion(&[layers[0].layer_desc().filename()])
+            .schedule_layer_file_deletion(&[layers[0].layer_desc().layer_name()])
            .unwrap();
        {
            let mut guard = client.upload_queue.lock().unwrap();
@@ -2132,9 +2288,9 @@ mod tests {
        }
        assert_remote_files(
            &[
-                &initial_layer.file_name(),
-                &layers[0].layer_desc().filename().file_name(),
-                &layers[1].layer_desc().filename().file_name(),
+                &initial_layer.to_string(),
+                &layers[0].layer_desc().layer_name().to_string(),
+                &layers[1].layer_desc().layer_name().to_string(),
                "index_part.json",
            ],
            &remote_timeline_dir,
@@ -2147,9 +2303,9 @@ mod tests {

        assert_remote_files(
            &[
-                &initial_layer.file_name(),
-                &layers[1].layer_desc().filename().file_name(),
-                &layers[2].layer_desc().filename().file_name(),
+                &initial_layer.to_string(),
+                &layers[1].layer_desc().layer_name().to_string(),
+                &layers[2].layer_desc().layer_name().to_string(),
                "index_part.json",
            ],
            &remote_timeline_dir,
@@ -2168,19 +2324,22 @@ mod tests {
            ..
        } = TestSetup::new("metrics").await.unwrap();
        let client = timeline.remote_client.as_ref().unwrap();
-        let timeline_path = harness.timeline_path(&TIMELINE_ID);

-        let layer_file_name_1: LayerFileName = "000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000016B59D8-00000000016B5A51".parse().unwrap();
+        let layer_file_name_1: LayerName = "000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000016B59D8-00000000016B5A51".parse().unwrap();
+        let local_path = local_layer_path(
+            harness.conf,
+            &timeline.tenant_shard_id,
+            &timeline.timeline_id,
+            &layer_file_name_1,
+            &harness.generation,
+        );
        let content_1 = dummy_contents("foo");
-        std::fs::write(
-            timeline_path.join(layer_file_name_1.file_name()),
-            &content_1,
-        )
-        .unwrap();
+        std::fs::write(&local_path, &content_1).unwrap();

        let layer_file_1 = Layer::for_resident(
            harness.conf,
            &timeline,
+            local_path,
            layer_file_name_1.clone(),
            LayerFileMetadata::new(content_1.len() as u64, harness.generation, harness.shard),
        );
@@ -2249,12 +2408,7 @@ mod tests {

    async fn inject_index_part(test_state: &TestSetup, generation: Generation) -> IndexPart {
        // An empty IndexPart, just sufficient to ensure deserialization will succeed
-        let example_metadata = TimelineMetadata::example();
-        let example_index_part = IndexPart::new(
-            HashMap::new(),
-            example_metadata.disk_consistent_lsn(),
-            example_metadata,
-        );
+        let example_index_part = IndexPart::example();

        let index_part_bytes = serde_json::to_vec(&example_index_part).unwrap();

--- a/pageserver/src/tenant/remote_timeline_client/download.rs
+++ b/pageserver/src/tenant/remote_timeline_client/download.rs
@@ -18,9 +18,11 @@ use tracing::warn;
 use utils::backoff;

 use crate::config::PageServerConf;
+use crate::context::RequestContext;
 use crate::span::debug_assert_current_span_has_tenant_and_timeline_id;
 use crate::tenant::remote_timeline_client::{remote_layer_path, remote_timelines_path};
-use crate::tenant::storage_layer::LayerFileName;
+use crate::tenant::storage_layer::layer::local_layer_path;
+use crate::tenant::storage_layer::LayerName;
 use crate::tenant::Generation;
 use crate::virtual_file::{on_fatal_io_error, MaybeFatalIo, VirtualFile};
 use crate::TEMP_FILE_SUFFIX;
@@ -40,19 +42,27 @@ use super::{
 /// in the metadata. (In the future, we might do more cross-checks, like CRC validation)
 ///
 /// Returns the size of the downloaded file.
+#[allow(clippy::too_many_arguments)]
 pub async fn download_layer_file<'a>(
    conf: &'static PageServerConf,
    storage: &'a GenericRemoteStorage,
    tenant_shard_id: TenantShardId,
    timeline_id: TimelineId,
-    layer_file_name: &'a LayerFileName,
+    layer_file_name: &'a LayerName,
    layer_metadata: &'a LayerFileMetadata,
    cancel: &CancellationToken,
+    ctx: &RequestContext,
 ) -> Result<u64, DownloadError> {
    debug_assert_current_span_has_tenant_and_timeline_id();

    let timeline_path = conf.timeline_path(&tenant_shard_id, &timeline_id);
-    let local_path = timeline_path.join(layer_file_name.file_name());
+    let local_path = local_layer_path(
+        conf,
+        &tenant_shard_id,
+        &timeline_id,
+        layer_file_name,
+        &layer_metadata.generation,
+    );

    let remote_path = remote_layer_path(
        &tenant_shard_id.tenant_id,
@@ -75,7 +85,7 @@ pub async fn download_layer_file<'a>(
    let temp_file_path = path_with_suffix_extension(&local_path, TEMP_DOWNLOAD_EXTENSION);

    let bytes_amount = download_retry(
-        || async { download_object(storage, &remote_path, &temp_file_path, cancel).await },
+        || async { download_object(storage, &remote_path, &temp_file_path, cancel, ctx).await },
        &format!("download {remote_path:?}"),
        cancel,
    )
@@ -102,14 +112,17 @@ pub async fn download_layer_file<'a>(
    // We use fatal_err() below because the after the rename above,
    // the in-memory state of the filesystem already has the layer file in its final place,
    // and subsequent pageserver code could think it's durable while it really isn't.
-    let work = async move {
-        let timeline_dir = VirtualFile::open(&timeline_path)
-            .await
-            .fatal_err("VirtualFile::open for timeline dir fsync");
-        timeline_dir
-            .sync_all()
-            .await
-            .fatal_err("VirtualFile::sync_all timeline dir");
+    let work = {
+        let ctx = ctx.detached_child(ctx.task_kind(), ctx.download_behavior());
+        async move {
+            let timeline_dir = VirtualFile::open(&timeline_path, &ctx)
+                .await
+                .fatal_err("VirtualFile::open for timeline dir fsync");
+            timeline_dir
+                .sync_all()
+                .await
+                .fatal_err("VirtualFile::sync_all timeline dir");
+        }
    };
    crate::virtual_file::io_engine::get()
        .spawn_blocking_and_block_on_if_std(work)
@@ -133,6 +146,7 @@ async fn download_object<'a>(
    src_path: &RemotePath,
    dst_path: &Utf8PathBuf,
    cancel: &CancellationToken,
+    #[cfg_attr(target_os = "macos", allow(unused_variables))] ctx: &RequestContext,
 ) -> Result<u64, DownloadError> {
    let res = match crate::virtual_file::io_engine::get() {
        crate::virtual_file::io_engine::IoEngine::NotSet => panic!("unset"),
@@ -185,7 +199,7 @@ async fn download_object<'a>(
            use crate::virtual_file::owned_buffers_io::{self, util::size_tracking_writer};
            use bytes::BytesMut;
            async {
-                let destination_file = VirtualFile::create(dst_path)
+                let destination_file = VirtualFile::create(dst_path, ctx)
                    .await
                    .with_context(|| format!("create a destination file for layer '{dst_path}'"))
                    .map_err(DownloadError::Other)?;
@@ -208,10 +222,10 @@ async fn download_object<'a>(
                            Err(e) => return Err(e),
                        };
                        buffered
-                            .write_buffered(tokio_epoll_uring::BoundedBuf::slice_full(chunk))
+                            .write_buffered(tokio_epoll_uring::BoundedBuf::slice_full(chunk), ctx)
                            .await?;
                    }
-                    let size_tracking = buffered.flush_and_into_inner().await?;
+                    let size_tracking = buffered.flush_and_into_inner(ctx).await?;
                    Ok(size_tracking.into_inner())
                }
                .await?;
--- a/pageserver/src/tenant/remote_timeline_client/index.rs
+++ b/pageserver/src/tenant/remote_timeline_client/index.rs
@@ -6,10 +6,10 @@ use std::collections::HashMap;

 use chrono::NaiveDateTime;
 use serde::{Deserialize, Serialize};
-use utils::bin_ser::SerializeError;
+use utils::id::TimelineId;

 use crate::tenant::metadata::TimelineMetadata;
-use crate::tenant::storage_layer::LayerFileName;
+use crate::tenant::storage_layer::LayerName;
 use crate::tenant::upload_queue::UploadQueueInitialized;
 use crate::tenant::Generation;
 use pageserver_api::shard::ShardIndex;
@@ -76,7 +76,7 @@ pub struct IndexPart {
    ///
    /// Older versions of `IndexPart` will not have this property or have only a part of metadata
    /// that latest version stores.
-    pub layer_metadata: HashMap<LayerFileName, IndexLayerMetadata>,
+    pub layer_metadata: HashMap<LayerName, IndexLayerMetadata>,

    // 'disk_consistent_lsn' is a copy of the 'disk_consistent_lsn' in the metadata.
    // It's duplicated for convenience when reading the serialized structure, but is
@@ -85,6 +85,9 @@ pub struct IndexPart {

    #[serde(rename = "metadata_bytes")]
    pub metadata: TimelineMetadata,
+
+    #[serde(default)]
+    pub(crate) lineage: Lineage,
 }

 impl IndexPart {
@@ -97,22 +100,23 @@ impl IndexPart {
    /// - 3: no longer deserialize `timeline_layers` (serialized format is the same, but timeline_layers
    ///      is always generated from the keys of `layer_metadata`)
    /// - 4: timeline_layers is fully removed.
-    const LATEST_VERSION: usize = 4;
+    /// - 5: lineage was added
+    const LATEST_VERSION: usize = 5;

    // Versions we may see when reading from a bucket.
-    pub const KNOWN_VERSIONS: &'static [usize] = &[1, 2, 3, 4];
+    pub const KNOWN_VERSIONS: &'static [usize] = &[1, 2, 3, 4, 5];

    pub const FILE_NAME: &'static str = "index_part.json";

-    pub fn new(
-        layers_and_metadata: HashMap<LayerFileName, LayerFileMetadata>,
+    fn new(
+        layers_and_metadata: &HashMap<LayerName, LayerFileMetadata>,
        disk_consistent_lsn: Lsn,
        metadata: TimelineMetadata,
+        lineage: Lineage,
    ) -> Self {
-        // Transform LayerFileMetadata into IndexLayerMetadata
        let layer_metadata = layers_and_metadata
-            .into_iter()
-            .map(|(k, v)| (k, IndexLayerMetadata::from(v)))
+            .iter()
+            .map(|(k, v)| (k.to_owned(), IndexLayerMetadata::from(v)))
            .collect();

        Self {
@@ -121,6 +125,7 @@ impl IndexPart {
            disk_consistent_lsn,
            metadata,
            deleted_at: None,
+            lineage,
        }
    }

@@ -141,20 +146,26 @@ impl IndexPart {
    pub fn to_s3_bytes(&self) -> serde_json::Result<Vec<u8>> {
        serde_json::to_vec(self)
    }
+
+    #[cfg(test)]
+    pub(crate) fn example() -> Self {
+        let example_metadata = TimelineMetadata::example();
+        Self::new(
+            &HashMap::new(),
+            example_metadata.disk_consistent_lsn(),
+            example_metadata,
+            Default::default(),
+        )
+    }
 }

-impl TryFrom<&UploadQueueInitialized> for IndexPart {
-    type Error = SerializeError;
+impl From<&UploadQueueInitialized> for IndexPart {
+    fn from(uq: &UploadQueueInitialized) -> Self {
+        let disk_consistent_lsn = uq.latest_metadata.disk_consistent_lsn();
+        let metadata = uq.latest_metadata.clone();
+        let lineage = uq.latest_lineage.clone();

-    fn try_from(upload_queue: &UploadQueueInitialized) -> Result<Self, Self::Error> {
-        let disk_consistent_lsn = upload_queue.latest_metadata.disk_consistent_lsn();
-        let metadata = upload_queue.latest_metadata.clone();
-
-        Ok(Self::new(
-            upload_queue.latest_files.clone(),
-            disk_consistent_lsn,
-            metadata,
-        ))
+        Self::new(&uq.latest_files, disk_consistent_lsn, metadata, lineage)
    }
 }

@@ -172,8 +183,8 @@ pub struct IndexLayerMetadata {
    pub shard: ShardIndex,
 }

-impl From<LayerFileMetadata> for IndexLayerMetadata {
-    fn from(other: LayerFileMetadata) -> Self {
+impl From<&LayerFileMetadata> for IndexLayerMetadata {
+    fn from(other: &LayerFileMetadata) -> Self {
        IndexLayerMetadata {
            file_size: other.file_size,
            generation: other.generation,
@@ -182,8 +193,76 @@ impl From<LayerFileMetadata> for IndexLayerMetadata {
    }
 }

+/// Limited history of earlier ancestors.
+///
+/// A timeline can have more than 1 earlier ancestor, in the rare case that it was repeatedly
+/// reparented by having an later timeline be detached from it's ancestor.
+#[derive(Debug, PartialEq, Eq, Clone, Serialize, Deserialize, Default)]
+pub(crate) struct Lineage {
+    /// Has the `reparenting_history` been truncated to [`Lineage::REMEMBER_AT_MOST`].
+    #[serde(skip_serializing_if = "is_false", default)]
+    reparenting_history_truncated: bool,
+
+    /// Earlier ancestors, truncated when [`Self::reparenting_history_truncated`]
+    ///
+    /// These are stored in case we want to support WAL based DR on the timeline. There can be many
+    /// of these and at most one [`Self::original_ancestor`]. There cannot be more reparentings
+    /// after [`Self::original_ancestor`] has been set.
+    #[serde(skip_serializing_if = "Vec::is_empty", default)]
+    reparenting_history: Vec<TimelineId>,
+
+    /// The ancestor from which this timeline has been detached from and when.
+    ///
+    /// If you are adding support for detaching from a hierarchy, consider changing the ancestry
+    /// into a `Vec<(TimelineId, Lsn)>` to be a path instead.
+    #[serde(skip_serializing_if = "Option::is_none", default)]
+    original_ancestor: Option<(TimelineId, Lsn, NaiveDateTime)>,
+}
+
+fn is_false(b: &bool) -> bool {
+    !b
+}
+
+impl Lineage {
+    const REMEMBER_AT_MOST: usize = 100;
+
+    pub(crate) fn record_previous_ancestor(&mut self, old_ancestor: &TimelineId) {
+        if self.reparenting_history.last() == Some(old_ancestor) {
+            // do not re-record it
+            return;
+        }
+
+        let drop_oldest = self.reparenting_history.len() + 1 >= Self::REMEMBER_AT_MOST;
+
+        self.reparenting_history_truncated |= drop_oldest;
+        if drop_oldest {
+            self.reparenting_history.remove(0);
+        }
+        self.reparenting_history.push(*old_ancestor);
+    }
+
+    pub(crate) fn record_detaching(&mut self, branchpoint: &(TimelineId, Lsn)) {
+        assert!(self.original_ancestor.is_none());
+
+        self.original_ancestor =
+            Some((branchpoint.0, branchpoint.1, chrono::Utc::now().naive_utc()));
+    }
+
+    /// The queried lsn is most likely the basebackup lsn, and this answers question "is it allowed
+    /// to start a read/write primary at this lsn".
+    ///
+    /// Returns true if the Lsn was previously a branch point.
+    pub(crate) fn is_previous_ancestor_lsn(&self, lsn: Lsn) -> bool {
+        self.original_ancestor
+            .as_ref()
+            .is_some_and(|(_, ancestor_lsn, _)| lsn == *ancestor_lsn)
+    }
+}
+
 #[cfg(test)]
 mod tests {
+    use std::str::FromStr;
+
    use super::*;

    #[test]
@@ -219,6 +298,7 @@ mod tests {
            disk_consistent_lsn: "0/16960E8".parse::<Lsn>().unwrap(),
            metadata: TimelineMetadata::from_bytes(&[113,11,159,210,0,54,0,4,0,0,0,0,1,105,96,232,1,0,0,0,0,1,105,96,112,0,0,0,0,0,0,0,0,0,0,0,0,0,1,105,96,112,0,0,0,0,1,105,96,112,0,0,0,14,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]).unwrap(),
            deleted_at: None,
+            lineage: Lineage::default(),
        };

        let part = IndexPart::from_s3_bytes(example.as_bytes()).unwrap();
@@ -259,6 +339,7 @@ mod tests {
            disk_consistent_lsn: "0/16960E8".parse::<Lsn>().unwrap(),
            metadata: TimelineMetadata::from_bytes(&[113,11,159,210,0,54,0,4,0,0,0,0,1,105,96,232,1,0,0,0,0,1,105,96,112,0,0,0,0,0,0,0,0,0,0,0,0,0,1,105,96,112,0,0,0,0,1,105,96,112,0,0,0,14,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]).unwrap(),
            deleted_at: None,
+            lineage: Lineage::default(),
        };

        let part = IndexPart::from_s3_bytes(example.as_bytes()).unwrap();
@@ -300,7 +381,8 @@ mod tests {
            disk_consistent_lsn: "0/16960E8".parse::<Lsn>().unwrap(),
            metadata: TimelineMetadata::from_bytes(&[113,11,159,210,0,54,0,4,0,0,0,0,1,105,96,232,1,0,0,0,0,1,105,96,112,0,0,0,0,0,0,0,0,0,0,0,0,0,1,105,96,112,0,0,0,0,1,105,96,112,0,0,0,14,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]).unwrap(),
            deleted_at: Some(chrono::NaiveDateTime::parse_from_str(
-                "2023-07-31T09:00:00.123000000", "%Y-%m-%dT%H:%M:%S.%f").unwrap())
+                "2023-07-31T09:00:00.123000000", "%Y-%m-%dT%H:%M:%S.%f").unwrap()),
+            lineage: Lineage::default(),
        };

        let part = IndexPart::from_s3_bytes(example.as_bytes()).unwrap();
@@ -345,6 +427,7 @@ mod tests {
            ])
            .unwrap(),
            deleted_at: None,
+            lineage: Lineage::default(),
        };

        let empty_layers_parsed = IndexPart::from_s3_bytes(empty_layers_json.as_bytes()).unwrap();
@@ -383,11 +466,58 @@ mod tests {
            ]),
            disk_consistent_lsn: "0/16960E8".parse::<Lsn>().unwrap(),
            metadata: TimelineMetadata::from_bytes(&[113,11,159,210,0,54,0,4,0,0,0,0,1,105,96,232,1,0,0,0,0,1,105,96,112,0,0,0,0,0,0,0,0,0,0,0,0,0,1,105,96,112,0,0,0,0,1,105,96,112,0,0,0,14,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]).unwrap(),
-            deleted_at: Some(chrono::NaiveDateTime::parse_from_str(
-                "2023-07-31T09:00:00.123000000", "%Y-%m-%dT%H:%M:%S.%f").unwrap()),
+            deleted_at: Some(parse_naive_datetime("2023-07-31T09:00:00.123000000")),
+            lineage: Lineage::default(),
        };

        let part = IndexPart::from_s3_bytes(example.as_bytes()).unwrap();
        assert_eq!(part, expected);
    }
+
+    #[test]
+    fn v5_indexpart_is_parsed() {
+        let example = r#"{
+            "version":5,
+            "layer_metadata":{
+                "000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000014EF420-00000000014EF499":{"file_size":23289856,"generation":1},
+                "000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000014EF499-00000000015A7619":{"file_size":1015808,"generation":1}},
+                "disk_consistent_lsn":"0/15A7618",
+                "metadata_bytes":[226,88,25,241,0,46,0,4,0,0,0,0,1,90,118,24,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,78,244,32,0,0,0,0,1,78,244,32,0,0,0,16,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
+                "lineage":{
+                    "original_ancestor":["e2bfd8c633d713d279e6fcd2bcc15b6d","0/15A7618","2024-05-07T18:52:36.322426563"],
+                    "reparenting_history":["e1bfd8c633d713d279e6fcd2bcc15b6d"]
+                }
+        }"#;
+
+        let expected = IndexPart {
+            version: 5,
+            layer_metadata: HashMap::from([
+                ("000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000014EF420-00000000014EF499".parse().unwrap(), IndexLayerMetadata {
+                    file_size: 23289856,
+                    generation: Generation::new(1),
+                    shard: ShardIndex::unsharded(),
+                }),
+                ("000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000014EF499-00000000015A7619".parse().unwrap(), IndexLayerMetadata {
+                    file_size: 1015808,
+                    generation: Generation::new(1),
+                    shard: ShardIndex::unsharded(),
+                })
+            ]),
+            disk_consistent_lsn: Lsn::from_str("0/15A7618").unwrap(),
+            metadata: TimelineMetadata::from_bytes(&[226,88,25,241,0,46,0,4,0,0,0,0,1,90,118,24,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,78,244,32,0,0,0,0,1,78,244,32,0,0,0,16,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]).unwrap(),
+            deleted_at: None,
+            lineage: Lineage {
+                reparenting_history_truncated: false,
+                reparenting_history: vec![TimelineId::from_str("e1bfd8c633d713d279e6fcd2bcc15b6d").unwrap()],
+                original_ancestor: Some((TimelineId::from_str("e2bfd8c633d713d279e6fcd2bcc15b6d").unwrap(), Lsn::from_str("0/15A7618").unwrap(), parse_naive_datetime("2024-05-07T18:52:36.322426563"))),
+            },
+        };
+
+        let part = IndexPart::from_s3_bytes(example.as_bytes()).unwrap();
+        assert_eq!(part, expected);
+    }
+
+    fn parse_naive_datetime(s: &str) -> NaiveDateTime {
+        chrono::NaiveDateTime::parse_from_str(s, "%Y-%m-%dT%H:%M:%S.%f").unwrap()
+    }
 }
--- a/pageserver/src/tenant/remote_timeline_client/upload.rs
+++ b/pageserver/src/tenant/remote_timeline_client/upload.rs
@@ -12,18 +12,13 @@ use tokio_util::sync::CancellationToken;
 use utils::backoff;

 use super::Generation;
-use crate::{
-    config::PageServerConf,
-    tenant::remote_timeline_client::{
-        index::IndexPart, remote_index_path, remote_initdb_archive_path,
-        remote_initdb_preserved_archive_path, remote_path,
-    },
+use crate::tenant::remote_timeline_client::{
+    index::IndexPart, remote_index_path, remote_initdb_archive_path,
+    remote_initdb_preserved_archive_path,
 };
-use remote_storage::{GenericRemoteStorage, TimeTravelError};
+use remote_storage::{GenericRemoteStorage, RemotePath, TimeTravelError};
 use utils::id::{TenantId, TimelineId};

-use super::index::LayerFileMetadata;
-
 use tracing::info;

 /// Serializes and uploads the given index part data to the remote storage.
@@ -65,11 +60,10 @@ pub(crate) async fn upload_index_part<'a>(
 ///
 /// On an error, bumps the retries count and reschedules the entire task.
 pub(super) async fn upload_timeline_layer<'a>(
-    conf: &'static PageServerConf,
    storage: &'a GenericRemoteStorage,
-    source_path: &'a Utf8Path,
-    known_metadata: &'a LayerFileMetadata,
-    generation: Generation,
+    local_path: &'a Utf8Path,
+    remote_path: &'a RemotePath,
+    metadata_size: u64,
    cancel: &CancellationToken,
 ) -> anyhow::Result<()> {
    fail_point!("before-upload-layer", |_| {
@@ -78,8 +72,7 @@ pub(super) async fn upload_timeline_layer<'a>(

    pausable_failpoint!("before-upload-layer-pausable");

-    let storage_path = remote_path(conf, source_path, generation)?;
-    let source_file_res = fs::File::open(&source_path).await;
+    let source_file_res = fs::File::open(&local_path).await;
    let source_file = match source_file_res {
        Ok(source_file) => source_file,
        Err(e) if e.kind() == ErrorKind::NotFound => {
@@ -90,34 +83,49 @@ pub(super) async fn upload_timeline_layer<'a>(
            // it has been written to disk yet.
            //
            // This is tested against `test_compaction_delete_before_upload`
-            info!(path = %source_path, "File to upload doesn't exist. Likely the file has been deleted and an upload is not required any more.");
+            info!(path = %local_path, "File to upload doesn't exist. Likely the file has been deleted and an upload is not required any more.");
            return Ok(());
        }
-        Err(e) => {
-            Err(e).with_context(|| format!("open a source file for layer {source_path:?}"))?
-        }
+        Err(e) => Err(e).with_context(|| format!("open a source file for layer {local_path:?}"))?,
    };

    let fs_size = source_file
        .metadata()
        .await
-        .with_context(|| format!("get the source file metadata for layer {source_path:?}"))?
+        .with_context(|| format!("get the source file metadata for layer {local_path:?}"))?
        .len();

-    let metadata_size = known_metadata.file_size();
    if metadata_size != fs_size {
-        bail!("File {source_path:?} has its current FS size {fs_size} diferent from initially determined {metadata_size}");
+        bail!("File {local_path:?} has its current FS size {fs_size} diferent from initially determined {metadata_size}");
    }

    let fs_size = usize::try_from(fs_size)
-        .with_context(|| format!("convert {source_path:?} size {fs_size} usize"))?;
+        .with_context(|| format!("convert {local_path:?} size {fs_size} usize"))?;

    let reader = tokio_util::io::ReaderStream::with_capacity(source_file, super::BUFFER_SIZE);

    storage
-        .upload(reader, fs_size, &storage_path, None, cancel)
+        .upload(reader, fs_size, remote_path, None, cancel)
        .await
-        .with_context(|| format!("upload layer from local path '{source_path}'"))
+        .with_context(|| format!("upload layer from local path '{local_path}'"))
+}
+
+pub(super) async fn copy_timeline_layer(
+    storage: &GenericRemoteStorage,
+    source_path: &RemotePath,
+    target_path: &RemotePath,
+    cancel: &CancellationToken,
+) -> anyhow::Result<()> {
+    fail_point!("before-copy-layer", |_| {
+        bail!("failpoint before-copy-layer")
+    });
+
+    pausable_failpoint!("before-copy-layer-pausable");
+
+    storage
+        .copy_object(source_path, target_path, cancel)
+        .await
+        .with_context(|| format!("copy layer {source_path} to {target_path}"))
 }

 /// Uploads the given `initdb` data to the remote storage.
--- a/pageserver/src/tenant/secondary.rs
+++ b/pageserver/src/tenant/secondary.rs
@@ -7,6 +7,7 @@ use std::{sync::Arc, time::SystemTime};

 use crate::{
    config::PageServerConf,
+    context::RequestContext,
    disk_usage_eviction_task::DiskUsageEvictionInfo,
    task_mgr::{self, TaskKind, BACKGROUND_RUNTIME},
    virtual_file::MaybeFatalIo,
@@ -20,8 +21,9 @@ use self::{
 use super::{
    config::{SecondaryLocationConfig, TenantConfOpt},
    mgr::TenantManager,
+    remote_timeline_client::LayerFileMetadata,
    span::debug_assert_current_span_has_tenant_id,
-    storage_layer::LayerFileName,
+    storage_layer::{layer::local_layer_path, LayerName},
 };

 use pageserver_api::{
@@ -180,7 +182,8 @@ impl SecondaryTenant {
        self: &Arc<Self>,
        conf: &PageServerConf,
        timeline_id: TimelineId,
-        name: LayerFileName,
+        name: LayerName,
+        metadata: LayerFileMetadata,
    ) {
        debug_assert_current_span_has_tenant_id();

@@ -194,9 +197,13 @@ impl SecondaryTenant {

        let now = SystemTime::now();

-        let path = conf
-            .timeline_path(&self.tenant_shard_id, &timeline_id)
-            .join(name.file_name());
+        let local_path = local_layer_path(
+            conf,
+            &self.tenant_shard_id,
+            &timeline_id,
+            &name,
+            &metadata.generation,
+        );

        let this = self.clone();

@@ -207,7 +214,7 @@ impl SecondaryTenant {
            // it, the secondary downloader could have seen an updated heatmap that
            // resulted in a layer being deleted.
            // Other local I/O errors are process-fatal: these should never happen.
-            let deleted = std::fs::remove_file(path);
+            let deleted = std::fs::remove_file(local_path);

            let not_found = deleted
                .as_ref()
@@ -316,9 +323,13 @@ pub fn spawn_tasks(
    let (upload_req_tx, upload_req_rx) =
        tokio::sync::mpsc::channel::<CommandRequest<UploadCommand>>(16);

+    let downloader_task_ctx = RequestContext::new(
+        TaskKind::SecondaryDownloads,
+        crate::context::DownloadBehavior::Download,
+    );
    task_mgr::spawn(
        BACKGROUND_RUNTIME.handle(),
-        TaskKind::SecondaryDownloads,
+        downloader_task_ctx.task_kind(),
        None,
        None,
        "secondary tenant downloads",
@@ -330,6 +341,7 @@ pub fn spawn_tasks(
                download_req_rx,
                bg_jobs_clone,
                cancel_clone,
+                downloader_task_ctx,
            )
            .await;

--- a/pageserver/src/tenant/secondary/downloader.rs
+++ b/pageserver/src/tenant/secondary/downloader.rs
@@ -8,6 +8,7 @@ use std::{

 use crate::{
    config::PageServerConf,
+    context::RequestContext,
    disk_usage_eviction_task::{
        finite_f32, DiskUsageEvictionInfo, EvictionCandidate, EvictionLayer, EvictionSecondaryLayer,
    },
@@ -21,7 +22,7 @@ use crate::{
            FAILED_REMOTE_OP_RETRIES,
        },
        span::debug_assert_current_span_has_tenant_id,
-        storage_layer::LayerFileName,
+        storage_layer::{layer::local_layer_path, LayerName},
        tasks::{warn_when_period_overrun, BackgroundLoopKind},
    },
    virtual_file::{on_fatal_io_error, MaybeFatalIo, VirtualFile},
@@ -30,7 +31,10 @@ use crate::{

 use super::{
    heatmap::HeatMapLayer,
-    scheduler::{self, Completion, JobGenerator, SchedulingResult, TenantBackgroundJobs},
+    scheduler::{
+        self, period_jitter, period_warmup, Completion, JobGenerator, SchedulingResult,
+        TenantBackgroundJobs,
+    },
    SecondaryTenant,
 };

@@ -44,7 +48,6 @@ use chrono::format::{DelayedFormat, StrftimeItems};
 use futures::Future;
 use pageserver_api::models::SecondaryProgress;
 use pageserver_api::shard::TenantShardId;
-use rand::Rng;
 use remote_storage::{DownloadError, Etag, GenericRemoteStorage};

 use tokio_util::sync::CancellationToken;
@@ -74,12 +77,14 @@ pub(super) async fn downloader_task(
    command_queue: tokio::sync::mpsc::Receiver<CommandRequest<DownloadCommand>>,
    background_jobs_can_start: Barrier,
    cancel: CancellationToken,
+    root_ctx: RequestContext,
 ) {
    let concurrency = tenant_manager.get_conf().secondary_download_concurrency;

    let generator = SecondaryDownloader {
        tenant_manager,
        remote_storage,
+        root_ctx,
    };
    let mut scheduler = Scheduler::new(generator, concurrency);

@@ -92,6 +97,7 @@ pub(super) async fn downloader_task(
 struct SecondaryDownloader {
    tenant_manager: Arc<TenantManager>,
    remote_storage: GenericRemoteStorage,
+    root_ctx: RequestContext,
 }

 #[derive(Debug, Clone)]
@@ -105,7 +111,7 @@ impl OnDiskState {
        _conf: &'static PageServerConf,
        _tenant_shard_id: &TenantShardId,
        _imeline_id: &TimelineId,
-        _ame: LayerFileName,
+        _ame: LayerName,
        metadata: LayerFileMetadata,
        access_time: SystemTime,
    ) -> Self {
@@ -118,10 +124,10 @@ impl OnDiskState {

 #[derive(Debug, Clone, Default)]
 pub(super) struct SecondaryDetailTimeline {
-    pub(super) on_disk_layers: HashMap<LayerFileName, OnDiskState>,
+    pub(super) on_disk_layers: HashMap<LayerName, OnDiskState>,

    /// We remember when layers were evicted, to prevent re-downloading them.
-    pub(super) evicted_at: HashMap<LayerFileName, SystemTime>,
+    pub(super) evicted_at: HashMap<LayerName, SystemTime>,
 }

 /// This state is written by the secondary downloader, it is opaque
@@ -270,7 +276,7 @@ impl JobGenerator<PendingDownload, RunningDownload, CompleteDownload, DownloadCo
        // Update freshened_at even if there was an error: we don't want errored tenants to implicitly
        // take priority to run again.
        let mut detail = secondary_state.detail.lock().unwrap();
-        detail.next_download = Some(Instant::now() + DOWNLOAD_FRESHEN_INTERVAL);
+        detail.next_download = Some(Instant::now() + period_jitter(DOWNLOAD_FRESHEN_INTERVAL, 5));
    }

    async fn schedule(&mut self) -> SchedulingResult<PendingDownload> {
@@ -301,11 +307,9 @@ impl JobGenerator<PendingDownload, RunningDownload, CompleteDownload, DownloadCo
                    }

                    if detail.next_download.is_none() {
-                        // Initialize with a jitter: this spreads initial downloads on startup
-                        // or mass-attach across our freshen interval.
-                        let jittered_period =
-                            rand::thread_rng().gen_range(Duration::ZERO..DOWNLOAD_FRESHEN_INTERVAL);
-                        detail.next_download = Some(now.checked_add(jittered_period).expect(
+                        // Initialize randomly in the range from 0 to our interval: this uniformly spreads the start times.  Subsequent
+                        // rounds will use a smaller jitter to avoid accidentally synchronizing later.
+                        detail.next_download = Some(now.checked_add(period_warmup(DOWNLOAD_FRESHEN_INTERVAL)).expect(
                        "Using our constant, which is known to be small compared with clock range",
                    ));
                    }
@@ -367,11 +371,12 @@ impl JobGenerator<PendingDownload, RunningDownload, CompleteDownload, DownloadCo
        let remote_storage = self.remote_storage.clone();
        let conf = self.tenant_manager.get_conf();
        let tenant_shard_id = *secondary_state.get_tenant_shard_id();
+        let download_ctx = self.root_ctx.attached_child();
        (RunningDownload { barrier }, Box::pin(async move {
            let _completion = completion;

            match TenantDownloader::new(conf, &remote_storage, &secondary_state)
-                .download()
+                .download(&download_ctx)
                .await
            {
                Err(UpdateError::NoData) => {
@@ -485,7 +490,7 @@ impl<'a> TenantDownloader<'a> {
        }
    }

-    async fn download(&self) -> Result<(), UpdateError> {
+    async fn download(&self, ctx: &RequestContext) -> Result<(), UpdateError> {
        debug_assert_current_span_has_tenant_id();

        // For the duration of a download, we must hold the SecondaryTenant::gate, to ensure
@@ -560,7 +565,7 @@ impl<'a> TenantDownloader<'a> {
            }

            let timeline_id = timeline.timeline_id;
-            self.download_timeline(timeline)
+            self.download_timeline(timeline, ctx)
                .instrument(tracing::info_span!(
                    "secondary_download_timeline",
                    tenant_id=%tenant_shard_id.tenant_id,
@@ -616,12 +621,12 @@ impl<'a> TenantDownloader<'a> {
                let layers_in_heatmap = heatmap_timeline
                    .layers
                    .iter()
-                    .map(|l| &l.name)
+                    .map(|l| (&l.name, l.metadata.generation))
                    .collect::<HashSet<_>>();
                let layers_on_disk = timeline_state
                    .on_disk_layers
                    .iter()
-                    .map(|l| l.0)
+                    .map(|l| (l.0, l.1.metadata.generation))
                    .collect::<HashSet<_>>();

                let mut layer_count = layers_on_disk.len();
@@ -632,16 +637,24 @@ impl<'a> TenantDownloader<'a> {
                    .sum();

                // Remove on-disk layers that are no longer present in heatmap
-                for layer in layers_on_disk.difference(&layers_in_heatmap) {
+                for (layer_file_name, generation) in layers_on_disk.difference(&layers_in_heatmap) {
                    layer_count -= 1;
                    layer_byte_count -= timeline_state
                        .on_disk_layers
-                        .get(layer)
+                        .get(layer_file_name)
                        .unwrap()
                        .metadata
                        .file_size();

-                    delete_layers.push((*timeline_id, (*layer).clone()));
+                    let local_path = local_layer_path(
+                        self.conf,
+                        self.secondary_state.get_tenant_shard_id(),
+                        timeline_id,
+                        layer_file_name,
+                        generation,
+                    );
+
+                    delete_layers.push((*timeline_id, (*layer_file_name).clone(), local_path));
                }

                progress.bytes_downloaded += layer_byte_count;
@@ -656,11 +669,7 @@ impl<'a> TenantDownloader<'a> {
        }

        // Execute accumulated deletions
-        for (timeline_id, layer_name) in delete_layers {
-            let timeline_path = self
-                .conf
-                .timeline_path(self.secondary_state.get_tenant_shard_id(), &timeline_id);
-            let local_path = timeline_path.join(layer_name.to_string());
+        for (timeline_id, layer_name, local_path) in delete_layers {
            tracing::info!(timeline_id=%timeline_id, "Removing secondary local layer {layer_name} because it's absent in heatmap",);

            tokio::fs::remove_file(&local_path)
@@ -742,12 +751,13 @@ impl<'a> TenantDownloader<'a> {
        .and_then(|x| x)
    }

-    async fn download_timeline(&self, timeline: HeatMapTimeline) -> Result<(), UpdateError> {
+    async fn download_timeline(
+        &self,
+        timeline: HeatMapTimeline,
+        ctx: &RequestContext,
+    ) -> Result<(), UpdateError> {
        debug_assert_current_span_has_tenant_and_timeline_id();
        let tenant_shard_id = self.secondary_state.get_tenant_shard_id();
-        let timeline_path = self
-            .conf
-            .timeline_path(tenant_shard_id, &timeline.timeline_id);

        // Accumulate updates to the state
        let mut touched = Vec::new();
@@ -797,10 +807,14 @@ impl<'a> TenantDownloader<'a> {
                if cfg!(debug_assertions) {
                    // Debug for https://github.com/neondatabase/neon/issues/6966: check that the files we think
                    // are already present on disk are really there.
-                    let local_path = self
-                        .conf
-                        .timeline_path(tenant_shard_id, &timeline.timeline_id)
-                        .join(layer.name.file_name());
+                    let local_path = local_layer_path(
+                        self.conf,
+                        tenant_shard_id,
+                        &timeline.timeline_id,
+                        &layer.name,
+                        &layer.metadata.generation,
+                    );
+
                    match tokio::fs::metadata(&local_path).await {
                        Ok(meta) => {
                            tracing::debug!(
@@ -875,6 +889,7 @@ impl<'a> TenantDownloader<'a> {
                &layer.name,
                &LayerFileMetadata::from(&layer.metadata),
                &self.secondary_state.cancel,
+                ctx,
            )
            .await
            {
@@ -893,7 +908,13 @@ impl<'a> TenantDownloader<'a> {
            };

            if downloaded_bytes != layer.metadata.file_size {
-                let local_path = timeline_path.join(layer.name.to_string());
+                let local_path = local_layer_path(
+                    self.conf,
+                    tenant_shard_id,
+                    &timeline.timeline_id,
+                    &layer.name,
+                    &layer.metadata.generation,
+                );

                tracing::warn!(
                    "Downloaded layer {} with unexpected size {} != {}.  Removing download.",
@@ -976,7 +997,7 @@ async fn init_timeline_state(

    // As we iterate through layers found on disk, we will look up their metadata from this map.
    // Layers not present in metadata will be discarded.
-    let heatmap_metadata: HashMap<&LayerFileName, &HeatMapLayer> =
+    let heatmap_metadata: HashMap<&LayerName, &HeatMapLayer> =
        heatmap.layers.iter().map(|l| (&l.name, l)).collect();

    while let Some(dentry) = dir
@@ -1013,7 +1034,7 @@ async fn init_timeline_state(
            continue;
        }

-        match LayerFileName::from_str(file_name) {
+        match LayerName::from_str(file_name) {
            Ok(name) => {
                let remote_meta = heatmap_metadata.get(&name);
                match remote_meta {
--- a/pageserver/src/tenant/secondary/heatmap.rs
+++ b/pageserver/src/tenant/secondary/heatmap.rs
@@ -1,8 +1,6 @@
 use std::time::SystemTime;

-use crate::tenant::{
-    remote_timeline_client::index::IndexLayerMetadata, storage_layer::LayerFileName,
-};
+use crate::tenant::{remote_timeline_client::index::IndexLayerMetadata, storage_layer::LayerName};

 use serde::{Deserialize, Serialize};
 use serde_with::{serde_as, DisplayFromStr, TimestampSeconds};
@@ -31,7 +29,7 @@ pub(crate) struct HeatMapTimeline {
 #[serde_as]
 #[derive(Serialize, Deserialize)]
 pub(crate) struct HeatMapLayer {
-    pub(super) name: LayerFileName,
+    pub(super) name: LayerName,
    pub(super) metadata: IndexLayerMetadata,

    #[serde_as(as = "TimestampSeconds<i64>")]
@@ -42,7 +40,7 @@ pub(crate) struct HeatMapLayer {

 impl HeatMapLayer {
    pub(crate) fn new(
-        name: LayerFileName,
+        name: LayerName,
        metadata: IndexLayerMetadata,
        access_time: SystemTime,
    ) -> Self {
--- a/pageserver/src/tenant/secondary/heatmap_uploader.rs
+++ b/pageserver/src/tenant/secondary/heatmap_uploader.rs
@@ -20,12 +20,14 @@ use crate::{

 use futures::Future;
 use pageserver_api::shard::TenantShardId;
-use rand::Rng;
 use remote_storage::{GenericRemoteStorage, TimeoutOrCancel};

 use super::{
    heatmap::HeatMapTenant,
-    scheduler::{self, JobGenerator, RunningJob, SchedulingResult, TenantBackgroundJobs},
+    scheduler::{
+        self, period_jitter, period_warmup, JobGenerator, RunningJob, SchedulingResult,
+        TenantBackgroundJobs,
+    },
    CommandRequest, UploadCommand,
 };
 use tokio_util::sync::CancellationToken;
@@ -181,15 +183,11 @@ impl JobGenerator<UploadPending, WriteInProgress, WriteComplete, UploadCommand>
            let state = self
                .tenants
                .entry(*tenant.get_tenant_shard_id())
-                .or_insert_with(|| {
-                    let jittered_period = rand::thread_rng().gen_range(Duration::ZERO..period);
-
-                    UploaderTenantState {
-                        tenant: Arc::downgrade(&tenant),
-                        last_upload: None,
-                        next_upload: Some(now.checked_add(jittered_period).unwrap_or(now)),
-                        last_digest: None,
-                    }
+                .or_insert_with(|| UploaderTenantState {
+                    tenant: Arc::downgrade(&tenant),
+                    last_upload: None,
+                    next_upload: Some(now.checked_add(period_warmup(period)).unwrap_or(now)),
+                    last_digest: None,
                });

            // Decline to do the upload if insufficient time has passed
@@ -274,7 +272,7 @@ impl JobGenerator<UploadPending, WriteInProgress, WriteComplete, UploadCommand>

            let next_upload = tenant
                .get_heatmap_period()
-                .and_then(|period| now.checked_add(period));
+                .and_then(|period| now.checked_add(period_jitter(period, 5)));

            WriteComplete {
                    tenant_shard_id: *tenant.get_tenant_shard_id(),
--- a/pageserver/src/tenant/secondary/scheduler.rs
+++ b/pageserver/src/tenant/secondary/scheduler.rs
@@ -1,4 +1,5 @@
 use futures::Future;
+use rand::Rng;
 use std::{
    collections::HashMap,
    marker::PhantomData,
@@ -19,6 +20,26 @@ use super::{CommandRequest, CommandResponse};
 const MAX_SCHEDULING_INTERVAL: Duration = Duration::from_secs(10);
 const MIN_SCHEDULING_INTERVAL: Duration = Duration::from_secs(1);

+/// Jitter a Duration by an integer percentage.  Returned values are uniform
+/// in the range 100-pct..100+pct (i.e. a 5% jitter is 5% either way: a ~10% range)
+pub(super) fn period_jitter(d: Duration, pct: u32) -> Duration {
+    if d == Duration::ZERO {
+        d
+    } else {
+        rand::thread_rng().gen_range((d * (100 - pct)) / 100..(d * (100 + pct)) / 100)
+    }
+}
+
+/// When a periodic task first starts, it should wait for some time in the range 0..period, so
+/// that starting many such tasks at the same time spreads them across the time range.
+pub(super) fn period_warmup(period: Duration) -> Duration {
+    if period == Duration::ZERO {
+        period
+    } else {
+        rand::thread_rng().gen_range(Duration::ZERO..period)
+    }
+}
+
 /// Scheduling helper for background work across many tenants.
 ///
 /// Systems that need to run background work across many tenants may use this type
--- a/pageserver/src/tenant/size.rs
+++ b/pageserver/src/tenant/size.rs
@@ -118,9 +118,6 @@ pub(super) async fn gather_inputs(
    ctx: &RequestContext,
 ) -> anyhow::Result<ModelInputs> {
    // refresh is needed to update gc related pitr_cutoff and horizon_cutoff
-    //
-    // FIXME: if a single timeline is deleted while refresh gc info is ongoing, we will fail the
-    // whole computation. It does not make sense from the billing perspective.
    tenant
        .refresh_gc_info(cancel, ctx)
        .await
@@ -192,7 +189,9 @@ pub(super) async fn gather_inputs(
        // than a space bound (horizon cutoff).  This means that if someone drops a database and waits for their
        // PITR interval, they will see synthetic size decrease, even if we are still storing data inside
        // horizon_cutoff.
-        let mut next_gc_cutoff = gc_info.pitr_cutoff;
+        let pitr_cutoff = gc_info.cutoffs.pitr;
+        let horizon_cutoff = gc_info.cutoffs.horizon;
+        let mut next_gc_cutoff = pitr_cutoff;

        // If the caller provided a shorter retention period, use that instead of the GC cutoff.
        let retention_param_cutoff = if let Some(max_retention_period) = max_retention_period {
@@ -219,6 +218,8 @@ pub(super) async fn gather_inputs(
            .map(|lsn| (lsn, LsnKind::BranchPoint))
            .collect::<Vec<_>>();

+        drop(gc_info);
+
        // Add branch points we collected earlier, just in case there were any that were
        // not present in retain_lsns. We will remove any duplicates below later.
        if let Some(this_branchpoints) = branchpoints.get(&timeline_id) {
@@ -297,8 +298,8 @@ pub(super) async fn gather_inputs(
            last_record: last_record_lsn,
            // this is not used above, because it might not have updated recently enough
            latest_gc_cutoff: *timeline.get_latest_gc_cutoff_lsn(),
-            horizon_cutoff: gc_info.horizon_cutoff,
-            pitr_cutoff: gc_info.pitr_cutoff,
+            horizon_cutoff,
+            pitr_cutoff,
            next_gc_cutoff,
            retention_param_cutoff,
        });
--- a/pageserver/src/tenant/storage_layer.rs
+++ b/pageserver/src/tenant/storage_layer.rs
@@ -1,11 +1,11 @@
 //! Common traits and structs for layers

 pub mod delta_layer;
-mod filename;
 pub mod image_layer;
 pub(crate) mod inmemory_layer;
 pub(crate) mod layer;
 mod layer_desc;
+mod layer_name;

 use crate::context::{AccessStatsBehavior, RequestContext};
 use crate::repository::Value;
@@ -34,10 +34,10 @@ use utils::rate_limit::RateLimit;
 use utils::{id::TimelineId, lsn::Lsn};

 pub use delta_layer::{DeltaLayer, DeltaLayerWriter, ValueRef};
-pub use filename::{DeltaFileName, ImageFileName, LayerFileName};
 pub use image_layer::{ImageLayer, ImageLayerWriter};
 pub use inmemory_layer::InMemoryLayer;
 pub use layer_desc::{PersistentLayerDesc, PersistentLayerKey};
+pub use layer_name::{DeltaLayerName, ImageLayerName, LayerName};

 pub(crate) use layer::{EvictionError, Layer, ResidentLayer};

@@ -646,8 +646,8 @@ pub mod tests {

    use super::*;

-    impl From<DeltaFileName> for PersistentLayerDesc {
-        fn from(value: DeltaFileName) -> Self {
+    impl From<DeltaLayerName> for PersistentLayerDesc {
+        fn from(value: DeltaLayerName) -> Self {
            PersistentLayerDesc::new_delta(
                TenantShardId::from([0; 18]),
                TimelineId::from_array([0; 16]),
@@ -658,8 +658,8 @@ pub mod tests {
        }
    }

-    impl From<ImageFileName> for PersistentLayerDesc {
-        fn from(value: ImageFileName) -> Self {
+    impl From<ImageLayerName> for PersistentLayerDesc {
+        fn from(value: ImageLayerName) -> Self {
            PersistentLayerDesc::new_img(
                TenantShardId::from([0; 18]),
                TimelineId::from_array([0; 16]),
@@ -670,11 +670,11 @@ pub mod tests {
        }
    }

-    impl From<LayerFileName> for PersistentLayerDesc {
-        fn from(value: LayerFileName) -> Self {
+    impl From<LayerName> for PersistentLayerDesc {
+        fn from(value: LayerName) -> Self {
            match value {
-                LayerFileName::Delta(d) => Self::from(d),
-                LayerFileName::Image(i) => Self::from(i),
+                LayerName::Delta(d) => Self::from(d),
+                LayerName::Image(i) => Self::from(i),
            }
        }
    }
--- a/pageserver/src/tenant/storage_layer/delta_layer.rs
+++ b/pageserver/src/tenant/storage_layer/delta_layer.rs
@@ -57,6 +57,7 @@ use std::fs::File;
 use std::io::SeekFrom;
 use std::ops::Range;
 use std::os::unix::fs::FileExt;
+use std::str::FromStr;
 use std::sync::Arc;
 use tokio::sync::OnceCell;
 use tracing::*;
@@ -68,7 +69,8 @@ use utils::{
 };

 use super::{
-    AsLayerDesc, LayerAccessStats, PersistentLayerDesc, ResidentLayer, ValuesReconstructState,
+    AsLayerDesc, LayerAccessStats, LayerName, PersistentLayerDesc, ResidentLayer,
+    ValuesReconstructState,
 };

 ///
@@ -309,13 +311,13 @@ impl DeltaLayer {
            .and_then(|res| res)?;

        // not production code
-        let actual_filename = path.file_name().unwrap().to_owned();
-        let expected_filename = self.layer_desc().filename().file_name();
+        let actual_layer_name = LayerName::from_str(path.file_name().unwrap()).unwrap();
+        let expected_layer_name = self.layer_desc().layer_name();

-        if actual_filename != expected_filename {
+        if actual_layer_name != expected_layer_name {
            println!("warning: filename does not match what is expected from in-file summary");
-            println!("actual: {:?}", actual_filename);
-            println!("expected: {:?}", expected_filename);
+            println!("actual: {:?}", actual_layer_name.to_string());
+            println!("expected: {:?}", expected_layer_name.to_string());
        }

        Ok(Arc::new(loaded))
@@ -392,6 +394,7 @@ impl DeltaLayerWriterInner {
        tenant_shard_id: TenantShardId,
        key_start: Key,
        lsn_range: Range<Lsn>,
+        ctx: &RequestContext,
    ) -> anyhow::Result<Self> {
        // Create the file initially with a temporary filename. We don't know
        // the end key yet, so we cannot form the final filename yet. We will
@@ -402,7 +405,7 @@ impl DeltaLayerWriterInner {
        let path =
            DeltaLayer::temp_path_for(conf, &tenant_shard_id, &timeline_id, key_start, &lsn_range);

-        let mut file = VirtualFile::create(&path).await?;
+        let mut file = VirtualFile::create(&path, ctx).await?;
        // make room for the header block
        file.seek(SeekFrom::Start(PAGE_SZ as u64)).await?;
        let blob_writer = BlobWriter::new(file, PAGE_SZ as u64);
@@ -428,9 +431,15 @@ impl DeltaLayerWriterInner {
    ///
    /// The values must be appended in key, lsn order.
    ///
-    async fn put_value(&mut self, key: Key, lsn: Lsn, val: Value) -> anyhow::Result<()> {
+    async fn put_value(
+        &mut self,
+        key: Key,
+        lsn: Lsn,
+        val: Value,
+        ctx: &RequestContext,
+    ) -> anyhow::Result<()> {
        let (_, res) = self
-            .put_value_bytes(key, lsn, Value::ser(&val)?, val.will_init())
+            .put_value_bytes(key, lsn, Value::ser(&val)?, val.will_init(), ctx)
            .await;
        res
    }
@@ -441,9 +450,10 @@ impl DeltaLayerWriterInner {
        lsn: Lsn,
        val: Vec<u8>,
        will_init: bool,
+        ctx: &RequestContext,
    ) -> (Vec<u8>, anyhow::Result<()>) {
        assert!(self.lsn_range.start <= lsn);
-        let (val, res) = self.blob_writer.write_blob(val).await;
+        let (val, res) = self.blob_writer.write_blob(val, ctx).await;
        let off = match res {
            Ok(off) => off,
            Err(e) => return (val, Err(anyhow::anyhow!(e))),
@@ -463,18 +473,23 @@ impl DeltaLayerWriterInner {
    ///
    /// Finish writing the delta layer.
    ///
-    async fn finish(self, key_end: Key, timeline: &Arc<Timeline>) -> anyhow::Result<ResidentLayer> {
+    async fn finish(
+        self,
+        key_end: Key,
+        timeline: &Arc<Timeline>,
+        ctx: &RequestContext,
+    ) -> anyhow::Result<ResidentLayer> {
        let index_start_blk =
            ((self.blob_writer.size() + PAGE_SZ as u64 - 1) / PAGE_SZ as u64) as u32;

-        let mut file = self.blob_writer.into_inner().await?;
+        let mut file = self.blob_writer.into_inner(ctx).await?;

        // Write out the index
        let (index_root_blk, block_buf) = self.tree.finish()?;
        file.seek(SeekFrom::Start(index_start_blk as u64 * PAGE_SZ as u64))
            .await?;
        for buf in block_buf.blocks {
-            let (_buf, res) = file.write_all(buf).await;
+            let (_buf, res) = file.write_all(buf, ctx).await;
            res?;
        }
        assert!(self.lsn_range.start < self.lsn_range.end);
@@ -494,7 +509,7 @@ impl DeltaLayerWriterInner {
        // TODO: could use smallvec here but it's a pain with Slice<T>
        Summary::ser_into(&summary, &mut buf)?;
        file.seek(SeekFrom::Start(0)).await?;
-        let (_buf, res) = file.write_all(buf).await;
+        let (_buf, res) = file.write_all(buf, ctx).await;
        res?;

        let metadata = file
@@ -572,6 +587,7 @@ impl DeltaLayerWriter {
        tenant_shard_id: TenantShardId,
        key_start: Key,
        lsn_range: Range<Lsn>,
+        ctx: &RequestContext,
    ) -> anyhow::Result<Self> {
        Ok(Self {
            inner: Some(
@@ -581,6 +597,7 @@ impl DeltaLayerWriter {
                    tenant_shard_id,
                    key_start,
                    lsn_range,
+                    ctx,
                )
                .await?,
            ),
@@ -592,8 +609,18 @@ impl DeltaLayerWriter {
    ///
    /// The values must be appended in key, lsn order.
    ///
-    pub async fn put_value(&mut self, key: Key, lsn: Lsn, val: Value) -> anyhow::Result<()> {
-        self.inner.as_mut().unwrap().put_value(key, lsn, val).await
+    pub async fn put_value(
+        &mut self,
+        key: Key,
+        lsn: Lsn,
+        val: Value,
+        ctx: &RequestContext,
+    ) -> anyhow::Result<()> {
+        self.inner
+            .as_mut()
+            .unwrap()
+            .put_value(key, lsn, val, ctx)
+            .await
    }

    pub async fn put_value_bytes(
@@ -602,11 +629,12 @@ impl DeltaLayerWriter {
        lsn: Lsn,
        val: Vec<u8>,
        will_init: bool,
+        ctx: &RequestContext,
    ) -> (Vec<u8>, anyhow::Result<()>) {
        self.inner
            .as_mut()
            .unwrap()
-            .put_value_bytes(key, lsn, val, will_init)
+            .put_value_bytes(key, lsn, val, will_init, ctx)
            .await
    }

@@ -621,10 +649,11 @@ impl DeltaLayerWriter {
        mut self,
        key_end: Key,
        timeline: &Arc<Timeline>,
+        ctx: &RequestContext,
    ) -> anyhow::Result<ResidentLayer> {
        let inner = self.inner.take().unwrap();
        let temp_path = inner.path.clone();
-        let result = inner.finish(key_end, timeline).await;
+        let result = inner.finish(key_end, timeline, ctx).await;
        // The delta layer files can sometimes be really large. Clean them up.
        if result.is_err() {
            tracing::warn!(
@@ -675,6 +704,7 @@ impl DeltaLayer {
        let mut file = VirtualFile::open_with_options(
            path,
            virtual_file::OpenOptions::new().read(true).write(true),
+            ctx,
        )
        .await
        .with_context(|| format!("Failed to open file '{}'", path))?;
@@ -692,7 +722,7 @@ impl DeltaLayer {
        // TODO: could use smallvec here, but it's a pain with Slice<T>
        Summary::ser_into(&new_summary, &mut buf).context("serialize")?;
        file.seek(SeekFrom::Start(0)).await?;
-        let (_buf, res) = file.write_all(buf).await;
+        let (_buf, res) = file.write_all(buf, ctx).await;
        res?;
        Ok(())
    }
@@ -708,7 +738,7 @@ impl DeltaLayerInner {
        max_vectored_read_bytes: Option<MaxVectoredReadBytes>,
        ctx: &RequestContext,
    ) -> Result<Result<Self, anyhow::Error>, anyhow::Error> {
-        let file = match VirtualFile::open(path).await {
+        let file = match VirtualFile::open(path, ctx).await {
            Ok(file) => file,
            Err(e) => return Ok(Err(anyhow::Error::new(e).context("open layer file"))),
        };
@@ -882,7 +912,7 @@ impl DeltaLayerInner {
        .await
        .map_err(GetVectoredError::Other)?;

-        self.do_reads_and_update_state(reads, reconstruct_state)
+        self.do_reads_and_update_state(reads, reconstruct_state, ctx)
            .await;

        reconstruct_state.on_lsn_advanced(&keyspace, self.lsn_range.start);
@@ -986,6 +1016,7 @@ impl DeltaLayerInner {
        &self,
        reads: Vec<VectoredRead>,
        reconstruct_state: &mut ValuesReconstructState,
+        ctx: &RequestContext,
    ) {
        let vectored_blob_reader = VectoredBlobReader::new(&self.file);
        let mut ignore_key_with_err = None;
@@ -1003,7 +1034,7 @@ impl DeltaLayerInner {
        // track when a key is done.
        for read in reads.into_iter().rev() {
            let res = vectored_blob_reader
-                .read_blobs(&read, buf.take().expect("Should have a buffer"))
+                .read_blobs(&read, buf.take().expect("Should have a buffer"), ctx)
                .await;

            let blobs_buf = match res {
@@ -1115,15 +1146,15 @@ impl DeltaLayerInner {
        Ok(all_keys)
    }

-    /// Using the given writer, write out a truncated version, where LSNs higher than the
-    /// truncate_at are missing.
-    #[cfg(test)]
+    /// Using the given writer, write out a version which has the earlier Lsns than `until`.
+    ///
+    /// Return the amount of key value records pushed to the writer.
    pub(super) async fn copy_prefix(
        &self,
        writer: &mut DeltaLayerWriter,
-        truncate_at: Lsn,
+        until: Lsn,
        ctx: &RequestContext,
-    ) -> anyhow::Result<()> {
+    ) -> anyhow::Result<usize> {
        use crate::tenant::vectored_blob_io::{
            BlobMeta, VectoredReadBuilder, VectoredReadExtended,
        };
@@ -1187,6 +1218,8 @@ impl DeltaLayerInner {
        // FIXME: buffering of DeltaLayerWriter
        let mut per_blob_copy = Vec::new();

+        let mut records = 0;
+
        while let Some(item) = stream.try_next().await? {
            tracing::debug!(?item, "popped");
            let offset = item
@@ -1205,7 +1238,7 @@ impl DeltaLayerInner {

            prev = Option::from(item);

-            let actionable = actionable.filter(|x| x.0.lsn < truncate_at);
+            let actionable = actionable.filter(|x| x.0.lsn < until);

            let builder = if let Some((meta, offsets)) = actionable {
                // extend or create a new builder
@@ -1246,7 +1279,7 @@ impl DeltaLayerInner {

                buf.clear();
                buf.reserve(read.size());
-                let res = reader.read_blobs(&read, buf).await?;
+                let res = reader.read_blobs(&read, buf, ctx).await?;

                for blob in res.blobs {
                    let key = blob.meta.key;
@@ -1273,7 +1306,7 @@ impl DeltaLayerInner {
                    let will_init = crate::repository::ValueBytes::will_init(data)
                        .inspect_err(|_e| {
                            #[cfg(feature = "testing")]
-                            tracing::error!(data=?utils::Hex(data), err=?_e, "failed to parse will_init out of serialized value");
+                            tracing::error!(data=?utils::Hex(data), err=?_e, %key, %lsn, "failed to parse will_init out of serialized value");
                        })
                        .unwrap_or(false);

@@ -1281,10 +1314,19 @@ impl DeltaLayerInner {
                    per_blob_copy.extend_from_slice(data);

                    let (tmp, res) = writer
-                        .put_value_bytes(key, lsn, std::mem::take(&mut per_blob_copy), will_init)
+                        .put_value_bytes(
+                            key,
+                            lsn,
+                            std::mem::take(&mut per_blob_copy),
+                            will_init,
+                            ctx,
+                        )
                        .await;
                    per_blob_copy = tmp;
+
                    res?;
+
+                    records += 1;
                }

                buffer = Some(res.buf);
@@ -1296,7 +1338,7 @@ impl DeltaLayerInner {
            "with the sentinel above loop should had handled all"
        );

-        Ok(())
+        Ok(records)
    }

    pub(super) async fn dump(&self, ctx: &RequestContext) -> anyhow::Result<()> {
@@ -1369,7 +1411,6 @@ impl DeltaLayerInner {
        Ok(())
    }

-    #[cfg(test)]
    fn stream_index_forwards<'a, R>(
        &'a self,
        reader: &'a DiskBtreeReader<R, DELTA_KEY_SIZE>,
@@ -1755,17 +1796,20 @@ mod test {
            harness.tenant_shard_id,
            entries_meta.key_range.start,
            entries_meta.lsn_range.clone(),
+            &ctx,
        )
        .await?;

        for entry in entries {
            let (_, res) = writer
-                .put_value_bytes(entry.key, entry.lsn, entry.value, false)
+                .put_value_bytes(entry.key, entry.lsn, entry.value, false, &ctx)
                .await;
            res?;
        }

-        let resident = writer.finish(entries_meta.key_range.end, &timeline).await?;
+        let resident = writer
+            .finish(entries_meta.key_range.end, &timeline, &ctx)
+            .await?;

        let inner = resident.as_delta(&ctx).await?;

@@ -1810,7 +1854,7 @@ mod test {

            for read in vectored_reads {
                let blobs_buf = vectored_blob_reader
-                    .read_blobs(&read, buf.take().expect("Should have a buffer"))
+                    .read_blobs(&read, buf.take().expect("Should have a buffer"), &ctx)
                    .await?;
                for meta in blobs_buf.blobs.iter() {
                    let value = &blobs_buf.buf[meta.start..meta.end];
@@ -1940,6 +1984,7 @@ mod test {
                tenant.tenant_shard_id,
                Key::MIN,
                Lsn(0x11)..truncate_at,
+                ctx,
            )
            .await
            .unwrap();
@@ -1951,7 +1996,7 @@ mod test {
                .await
                .unwrap();

-            let copied_layer = writer.finish(Key::MAX, &branch).await.unwrap();
+            let copied_layer = writer.finish(Key::MAX, &branch, ctx).await.unwrap();

            copied_layer.as_delta(ctx).await.unwrap();

--- a/pageserver/src/tenant/storage_layer/image_layer.rs
+++ b/pageserver/src/tenant/storage_layer/image_layer.rs
@@ -54,6 +54,7 @@ use std::fs::File;
 use std::io::SeekFrom;
 use std::ops::Range;
 use std::os::unix::prelude::FileExt;
+use std::str::FromStr;
 use std::sync::Arc;
 use tokio::sync::OnceCell;
 use tokio_stream::StreamExt;
@@ -65,8 +66,10 @@ use utils::{
    lsn::Lsn,
 };

-use super::filename::ImageFileName;
-use super::{AsLayerDesc, Layer, PersistentLayerDesc, ResidentLayer, ValuesReconstructState};
+use super::layer_name::ImageLayerName;
+use super::{
+    AsLayerDesc, Layer, LayerName, PersistentLayerDesc, ResidentLayer, ValuesReconstructState,
+};

 ///
 /// Header stored in the beginning of the file
@@ -231,7 +234,7 @@ impl ImageLayer {
        conf: &PageServerConf,
        timeline_id: TimelineId,
        tenant_shard_id: TenantShardId,
-        fname: &ImageFileName,
+        fname: &ImageLayerName,
    ) -> Utf8PathBuf {
        let rand_string: String = rand::thread_rng()
            .sample_iter(&Alphanumeric)
@@ -267,13 +270,13 @@ impl ImageLayer {
            .and_then(|res| res)?;

        // not production code
-        let actual_filename = path.file_name().unwrap().to_owned();
-        let expected_filename = self.layer_desc().filename().file_name();
+        let actual_layer_name = LayerName::from_str(path.file_name().unwrap()).unwrap();
+        let expected_layer_name = self.layer_desc().layer_name();

-        if actual_filename != expected_filename {
+        if actual_layer_name != expected_layer_name {
            println!("warning: filename does not match what is expected from in-file summary");
-            println!("actual: {:?}", actual_filename);
-            println!("expected: {:?}", expected_filename);
+            println!("actual: {:?}", actual_layer_name.to_string());
+            println!("expected: {:?}", expected_layer_name.to_string());
        }

        Ok(loaded)
@@ -340,6 +343,7 @@ impl ImageLayer {
        let mut file = VirtualFile::open_with_options(
            path,
            virtual_file::OpenOptions::new().read(true).write(true),
+            ctx,
        )
        .await
        .with_context(|| format!("Failed to open file '{}'", path))?;
@@ -357,7 +361,7 @@ impl ImageLayer {
        // TODO: could use smallvec here but it's a pain with Slice<T>
        Summary::ser_into(&new_summary, &mut buf).context("serialize")?;
        file.seek(SeekFrom::Start(0)).await?;
-        let (_buf, res) = file.write_all(buf).await;
+        let (_buf, res) = file.write_all(buf, ctx).await;
        res?;
        Ok(())
    }
@@ -374,7 +378,7 @@ impl ImageLayerInner {
        max_vectored_read_bytes: Option<MaxVectoredReadBytes>,
        ctx: &RequestContext,
    ) -> Result<Result<Self, anyhow::Error>, anyhow::Error> {
-        let file = match VirtualFile::open(path).await {
+        let file = match VirtualFile::open(path, ctx).await {
            Ok(file) => file,
            Err(e) => return Ok(Err(anyhow::Error::new(e).context("open layer file"))),
        };
@@ -471,7 +475,7 @@ impl ImageLayerInner {
            .await
            .map_err(GetVectoredError::Other)?;

-        self.do_reads_and_update_state(reads, reconstruct_state)
+        self.do_reads_and_update_state(reads, reconstruct_state, ctx)
            .await;

        Ok(())
@@ -534,6 +538,7 @@ impl ImageLayerInner {
        &self,
        reads: Vec<VectoredRead>,
        reconstruct_state: &mut ValuesReconstructState,
+        ctx: &RequestContext,
    ) {
        let max_vectored_read_bytes = self
            .max_vectored_read_bytes
@@ -562,7 +567,7 @@ impl ImageLayerInner {
            }

            let buf = BytesMut::with_capacity(buf_size);
-            let res = vectored_blob_reader.read_blobs(&read, buf).await;
+            let res = vectored_blob_reader.read_blobs(&read, buf, ctx).await;

            match res {
                Ok(blobs_buf) => {
@@ -628,6 +633,7 @@ impl ImageLayerWriterInner {
        tenant_shard_id: TenantShardId,
        key_range: &Range<Key>,
        lsn: Lsn,
+        ctx: &RequestContext,
    ) -> anyhow::Result<Self> {
        // Create the file initially with a temporary filename.
        // We'll atomically rename it to the final name when we're done.
@@ -635,7 +641,7 @@ impl ImageLayerWriterInner {
            conf,
            timeline_id,
            tenant_shard_id,
-            &ImageFileName {
+            &ImageLayerName {
                key_range: key_range.clone(),
                lsn,
            },
@@ -647,6 +653,7 @@ impl ImageLayerWriterInner {
                virtual_file::OpenOptions::new()
                    .write(true)
                    .create_new(true),
+                ctx,
            )
            .await?
        };
@@ -677,9 +684,14 @@ impl ImageLayerWriterInner {
    ///
    /// The page versions must be appended in blknum order.
    ///
-    async fn put_image(&mut self, key: Key, img: Bytes) -> anyhow::Result<()> {
+    async fn put_image(
+        &mut self,
+        key: Key,
+        img: Bytes,
+        ctx: &RequestContext,
+    ) -> anyhow::Result<()> {
        ensure!(self.key_range.contains(&key));
-        let (_img, res) = self.blob_writer.write_blob(img).await;
+        let (_img, res) = self.blob_writer.write_blob(img, ctx).await;
        // TODO: re-use the buffer for `img` further upstack
        let off = res?;

@@ -693,7 +705,11 @@ impl ImageLayerWriterInner {
    ///
    /// Finish writing the image layer.
    ///
-    async fn finish(self, timeline: &Arc<Timeline>) -> anyhow::Result<ResidentLayer> {
+    async fn finish(
+        self,
+        timeline: &Arc<Timeline>,
+        ctx: &RequestContext,
+    ) -> anyhow::Result<ResidentLayer> {
        let index_start_blk =
            ((self.blob_writer.size() + PAGE_SZ as u64 - 1) / PAGE_SZ as u64) as u32;

@@ -704,7 +720,7 @@ impl ImageLayerWriterInner {
            .await?;
        let (index_root_blk, block_buf) = self.tree.finish()?;
        for buf in block_buf.blocks {
-            let (_buf, res) = file.write_all(buf).await;
+            let (_buf, res) = file.write_all(buf, ctx).await;
            res?;
        }

@@ -724,7 +740,7 @@ impl ImageLayerWriterInner {
        // TODO: could use smallvec here but it's a pain with Slice<T>
        Summary::ser_into(&summary, &mut buf)?;
        file.seek(SeekFrom::Start(0)).await?;
-        let (_buf, res) = file.write_all(buf).await;
+        let (_buf, res) = file.write_all(buf, ctx).await;
        res?;

        let metadata = file
@@ -792,10 +808,11 @@ impl ImageLayerWriter {
        tenant_shard_id: TenantShardId,
        key_range: &Range<Key>,
        lsn: Lsn,
+        ctx: &RequestContext,
    ) -> anyhow::Result<ImageLayerWriter> {
        Ok(Self {
            inner: Some(
-                ImageLayerWriterInner::new(conf, timeline_id, tenant_shard_id, key_range, lsn)
+                ImageLayerWriterInner::new(conf, timeline_id, tenant_shard_id, key_range, lsn, ctx)
                    .await?,
            ),
        })
@@ -806,8 +823,13 @@ impl ImageLayerWriter {
    ///
    /// The page versions must be appended in blknum order.
    ///
-    pub async fn put_image(&mut self, key: Key, img: Bytes) -> anyhow::Result<()> {
-        self.inner.as_mut().unwrap().put_image(key, img).await
+    pub async fn put_image(
+        &mut self,
+        key: Key,
+        img: Bytes,
+        ctx: &RequestContext,
+    ) -> anyhow::Result<()> {
+        self.inner.as_mut().unwrap().put_image(key, img, ctx).await
    }

    ///
@@ -816,8 +838,9 @@ impl ImageLayerWriter {
    pub(crate) async fn finish(
        mut self,
        timeline: &Arc<Timeline>,
+        ctx: &RequestContext,
    ) -> anyhow::Result<super::ResidentLayer> {
-        self.inner.take().unwrap().finish(timeline).await
+        self.inner.take().unwrap().finish(timeline, ctx).await
    }
 }

--- a/pageserver/src/tenant/storage_layer/inmemory_layer.rs
+++ b/pageserver/src/tenant/storage_layer/inmemory_layer.rs
@@ -473,10 +473,11 @@ impl InMemoryLayer {
        timeline_id: TimelineId,
        tenant_shard_id: TenantShardId,
        start_lsn: Lsn,
+        ctx: &RequestContext,
    ) -> Result<InMemoryLayer> {
        trace!("initializing new empty InMemoryLayer for writing on timeline {timeline_id} at {start_lsn}");

-        let file = EphemeralFile::create(conf, tenant_shard_id, timeline_id).await?;
+        let file = EphemeralFile::create(conf, tenant_shard_id, timeline_id, ctx).await?;
        let key = InMemoryLayerFileId(file.page_cache_file_id());

        Ok(InMemoryLayer {
@@ -642,6 +643,7 @@ impl InMemoryLayer {
            self.tenant_shard_id,
            Key::MIN,
            self.start_lsn..end_lsn,
+            ctx,
        )
        .await?;

@@ -659,14 +661,14 @@ impl InMemoryLayer {
                let will_init = Value::des(&buf)?.will_init();
                let res;
                (buf, res) = delta_layer_writer
-                    .put_value_bytes(*key, *lsn, buf, will_init)
+                    .put_value_bytes(*key, *lsn, buf, will_init, &ctx)
                    .await;
                res?;
            }
        }

        // MAX is used here because we identify L0 layers by full key range
-        let delta_layer = delta_layer_writer.finish(Key::MAX, timeline).await?;
+        let delta_layer = delta_layer_writer.finish(Key::MAX, timeline, &ctx).await?;
        Ok(Some(delta_layer))
    }
 }
--- a/pageserver/src/tenant/storage_layer/layer.rs
+++ b/pageserver/src/tenant/storage_layer/layer.rs
@@ -4,26 +4,28 @@ use pageserver_api::keyspace::KeySpace;
 use pageserver_api::models::{
    HistoricLayerInfo, LayerAccessKind, LayerResidenceEventReason, LayerResidenceStatus,
 };
-use pageserver_api::shard::ShardIndex;
+use pageserver_api::shard::{ShardIndex, TenantShardId};
 use std::ops::Range;
 use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
 use std::sync::{Arc, Weak};
 use std::time::{Duration, SystemTime};
 use tracing::Instrument;
+use utils::id::TimelineId;
 use utils::lsn::Lsn;
 use utils::sync::heavier_once_cell;

 use crate::config::PageServerConf;
-use crate::context::RequestContext;
+use crate::context::{DownloadBehavior, RequestContext};
 use crate::repository::Key;
 use crate::span::debug_assert_current_span_has_tenant_and_timeline_id;
+use crate::task_mgr::TaskKind;
 use crate::tenant::timeline::GetVectoredError;
 use crate::tenant::{remote_timeline_client::LayerFileMetadata, Timeline};

 use super::delta_layer::{self, DeltaEntry};
 use super::image_layer;
 use super::{
-    AsLayerDesc, LayerAccessStats, LayerAccessStatsReset, LayerFileName, PersistentLayerDesc,
+    AsLayerDesc, LayerAccessStats, LayerAccessStatsReset, LayerName, PersistentLayerDesc,
    ValueReconstructResult, ValueReconstructState, ValuesReconstructState,
 };

@@ -122,14 +124,42 @@ impl PartialEq for Layer {
    }
 }

+pub(crate) fn local_layer_path(
+    conf: &PageServerConf,
+    tenant_shard_id: &TenantShardId,
+    timeline_id: &TimelineId,
+    layer_file_name: &LayerName,
+    _generation: &Generation,
+) -> Utf8PathBuf {
+    let timeline_path = conf.timeline_path(tenant_shard_id, timeline_id);
+
+    timeline_path.join(layer_file_name.to_string())
+
+    // TODO: switch to enabling new-style layer paths after next release
+    // if generation.is_none() {
+    //     // Without a generation, we may only use legacy path style
+    //     timeline_path.join(layer_file_name.to_string())
+    // } else {
+    //     timeline_path.join(format!("{}-v1{}", layer_file_name, generation.get_suffix()))
+    // }
+}
+
 impl Layer {
    /// Creates a layer value for a file we know to not be resident.
    pub(crate) fn for_evicted(
        conf: &'static PageServerConf,
        timeline: &Arc<Timeline>,
-        file_name: LayerFileName,
+        file_name: LayerName,
        metadata: LayerFileMetadata,
    ) -> Self {
+        let local_path = local_layer_path(
+            conf,
+            &timeline.tenant_shard_id,
+            &timeline.timeline_id,
+            &file_name,
+            &metadata.generation,
+        );
+
        let desc = PersistentLayerDesc::from_filename(
            timeline.tenant_shard_id,
            timeline.timeline_id,
@@ -142,6 +172,7 @@ impl Layer {
        let owner = Layer(Arc::new(LayerInner::new(
            conf,
            timeline,
+            local_path,
            access_stats,
            desc,
            None,
@@ -158,7 +189,8 @@ impl Layer {
    pub(crate) fn for_resident(
        conf: &'static PageServerConf,
        timeline: &Arc<Timeline>,
-        file_name: LayerFileName,
+        local_path: Utf8PathBuf,
+        file_name: LayerName,
        metadata: LayerFileMetadata,
    ) -> ResidentLayer {
        let desc = PersistentLayerDesc::from_filename(
@@ -183,6 +215,7 @@ impl Layer {
            LayerInner::new(
                conf,
                timeline,
+                local_path,
                access_stats,
                desc,
                Some(inner),
@@ -224,9 +257,19 @@ impl Layer {
                LayerResidenceStatus::Resident,
                LayerResidenceEventReason::LayerCreate,
            );
+
+            let local_path = local_layer_path(
+                conf,
+                &timeline.tenant_shard_id,
+                &timeline.timeline_id,
+                &desc.layer_name(),
+                &timeline.generation,
+            );
+
            LayerInner::new(
                conf,
                timeline,
+                local_path,
                access_stats,
                desc,
                Some(inner),
@@ -401,14 +444,21 @@ impl Layer {
        &self.0.path
    }

-    pub(crate) fn local_path_str(&self) -> &Arc<str> {
-        &self.0.path_str
+    pub(crate) fn debug_str(&self) -> &Arc<str> {
+        &self.0.debug_str
    }

    pub(crate) fn metadata(&self) -> LayerFileMetadata {
        self.0.metadata()
    }

+    pub(crate) fn get_timeline_id(&self) -> Option<TimelineId> {
+        self.0
+            .timeline
+            .upgrade()
+            .map(|timeline| timeline.timeline_id)
+    }
+
    /// Traditional debug dumping facility
    #[allow(unused)]
    pub(crate) async fn dump(&self, verbose: bool, ctx: &RequestContext) -> anyhow::Result<()> {
@@ -527,8 +577,8 @@ struct LayerInner {
    /// Full path to the file; unclear if this should exist anymore.
    path: Utf8PathBuf,

-    /// String representation of the full path, used for traversal id.
-    path_str: Arc<str>,
+    /// String representation of the layer, used for traversal id.
+    debug_str: Arc<str>,

    desc: PersistentLayerDesc,

@@ -640,7 +690,7 @@ impl Drop for LayerInner {
        let span = tracing::info_span!(parent: None, "layer_delete", tenant_id = %self.layer_desc().tenant_shard_id.tenant_id, shard_id=%self.layer_desc().tenant_shard_id.shard_slug(), timeline_id = %self.layer_desc().timeline_id);

        let path = std::mem::take(&mut self.path);
-        let file_name = self.layer_desc().filename();
+        let file_name = self.layer_desc().layer_name();
        let file_size = self.layer_desc().file_size;
        let timeline = self.timeline.clone();
        let meta = self.metadata();
@@ -708,19 +758,17 @@ impl Drop for LayerInner {
 }

 impl LayerInner {
+    #[allow(clippy::too_many_arguments)]
    fn new(
        conf: &'static PageServerConf,
        timeline: &Arc<Timeline>,
+        local_path: Utf8PathBuf,
        access_stats: LayerAccessStats,
        desc: PersistentLayerDesc,
        downloaded: Option<Arc<DownloadedLayer>>,
        generation: Generation,
        shard: ShardIndex,
    ) -> Self {
-        let path = conf
-            .timeline_path(&timeline.tenant_shard_id, &timeline.timeline_id)
-            .join(desc.filename().to_string());
-
        let (inner, version, init_status) = if let Some(inner) = downloaded {
            let version = inner.version;
            let resident = ResidentOrWantedEvicted::Resident(inner);
@@ -735,8 +783,10 @@ impl LayerInner {

        LayerInner {
            conf,
-            path_str: path.to_string().into(),
-            path,
+            debug_str: {
+                format!("timelines/{}/{}", timeline.timeline_id, desc.layer_name()).into()
+            },
+            path: local_path,
            desc,
            timeline: Arc::downgrade(timeline),
            have_remote_client: timeline.remote_client.is_some(),
@@ -939,11 +989,20 @@ impl LayerInner {
            return Err(DownloadError::DownloadRequired);
        }

+        let download_ctx = ctx
+            .map(|ctx| ctx.detached_child(TaskKind::LayerDownload, DownloadBehavior::Download))
+            .unwrap_or(RequestContext::new(
+                TaskKind::LayerDownload,
+                DownloadBehavior::Download,
+            ));
+
        async move {
            tracing::info!(%reason, "downloading on-demand");

            let init_cancelled = scopeguard::guard((), |_| LAYER_IMPL_METRICS.inc_init_cancelled());
-            let res = self.download_init_and_wait(timeline, permit).await?;
+            let res = self
+                .download_init_and_wait(timeline, permit, download_ctx)
+                .await?;
            scopeguard::ScopeGuard::into_inner(init_cancelled);
            Ok(res)
        }
@@ -982,6 +1041,7 @@ impl LayerInner {
        self: &Arc<Self>,
        timeline: Arc<Timeline>,
        permit: heavier_once_cell::InitPermit,
+        ctx: RequestContext,
    ) -> Result<Arc<DownloadedLayer>, DownloadError> {
        debug_assert_current_span_has_tenant_and_timeline_id();

@@ -1011,7 +1071,7 @@ impl LayerInner {
                    .await
                    .unwrap();

-                let res = this.download_and_init(timeline, permit).await;
+                let res = this.download_and_init(timeline, permit, &ctx).await;

                if let Err(res) = tx.send(res) {
                    match res {
@@ -1054,6 +1114,7 @@ impl LayerInner {
        self: &Arc<LayerInner>,
        timeline: Arc<Timeline>,
        permit: heavier_once_cell::InitPermit,
+        ctx: &RequestContext,
    ) -> anyhow::Result<Arc<DownloadedLayer>> {
        let client = timeline
            .remote_client
@@ -1061,7 +1122,12 @@ impl LayerInner {
            .expect("checked before download_init_and_wait");

        let result = client
-            .download_layer_file(&self.desc.filename(), &self.metadata(), &timeline.cancel)
+            .download_layer_file(
+                &self.desc.layer_name(),
+                &self.metadata(),
+                &timeline.cancel,
+                ctx,
+            )
            .await;

        match result {
@@ -1194,7 +1260,7 @@ impl LayerInner {
    }

    fn info(&self, reset: LayerAccessStatsReset) -> HistoricLayerInfo {
-        let layer_file_name = self.desc.filename().file_name();
+        let layer_name = self.desc.layer_name().to_string();

        let resident = self
            .inner
@@ -1208,7 +1274,7 @@ impl LayerInner {
            let lsn_range = &self.desc.lsn_range;

            HistoricLayerInfo::Delta {
-                layer_file_name,
+                layer_file_name: layer_name,
                layer_file_size: self.desc.file_size,
                lsn_start: lsn_range.start,
                lsn_end: lsn_range.end,
@@ -1219,7 +1285,7 @@ impl LayerInner {
            let lsn = self.desc.image_layer_lsn();

            HistoricLayerInfo::Image {
-                layer_file_name,
+                layer_file_name: layer_name,
                layer_file_size: self.desc.file_size,
                lsn_start: lsn,
                remote: !resident,
@@ -1780,25 +1846,23 @@ impl ResidentLayer {
        }
    }

-    /// FIXME: truncate is bad name because we are not truncating anything, but copying the
-    /// filtered parts.
-    #[cfg(test)]
-    pub(super) async fn copy_delta_prefix(
+    /// Returns the amount of keys and values written to the writer.
+    pub(crate) async fn copy_delta_prefix(
        &self,
        writer: &mut super::delta_layer::DeltaLayerWriter,
-        truncate_at: Lsn,
+        until: Lsn,
        ctx: &RequestContext,
-    ) -> anyhow::Result<()> {
+    ) -> anyhow::Result<usize> {
        use LayerKind::*;

        let owner = &self.owner.0;

        match self.downloaded.get(owner, ctx).await? {
            Delta(ref d) => d
-                .copy_prefix(writer, truncate_at, ctx)
+                .copy_prefix(writer, until, ctx)
                .await
-                .with_context(|| format!("truncate {self}")),
-            Image(_) => anyhow::bail!(format!("cannot truncate image layer {self}")),
+                .with_context(|| format!("copy_delta_prefix until {until} of {self}")),
+            Image(_) => anyhow::bail!(format!("cannot copy_lsn_prefix of image layer {self}")),
        }
    }

--- a/pageserver/src/tenant/storage_layer/layer_desc.rs
+++ b/pageserver/src/tenant/storage_layer/layer_desc.rs
@@ -5,7 +5,7 @@ use utils::{id::TimelineId, lsn::Lsn};

 use crate::repository::Key;

-use super::{DeltaFileName, ImageFileName, LayerFileName};
+use super::{DeltaLayerName, ImageLayerName, LayerName};

 use serde::{Deserialize, Serialize};

@@ -51,7 +51,7 @@ impl PersistentLayerDesc {
    }

    pub fn short_id(&self) -> impl Display {
-        self.filename()
+        self.layer_name()
    }

    #[cfg(test)]
@@ -103,14 +103,14 @@ impl PersistentLayerDesc {
    pub fn from_filename(
        tenant_shard_id: TenantShardId,
        timeline_id: TimelineId,
-        filename: LayerFileName,
+        filename: LayerName,
        file_size: u64,
    ) -> Self {
        match filename {
-            LayerFileName::Image(i) => {
+            LayerName::Image(i) => {
                Self::new_img(tenant_shard_id, timeline_id, i.key_range, i.lsn, file_size)
            }
-            LayerFileName::Delta(d) => Self::new_delta(
+            LayerName::Delta(d) => Self::new_delta(
                tenant_shard_id,
                timeline_id,
                d.key_range,
@@ -132,34 +132,34 @@ impl PersistentLayerDesc {
        lsn..(lsn + 1)
    }

-    /// Get a delta file name for this layer.
+    /// Get a delta layer name for this layer.
    ///
    /// Panic: if this is not a delta layer.
-    pub fn delta_file_name(&self) -> DeltaFileName {
+    pub fn delta_layer_name(&self) -> DeltaLayerName {
        assert!(self.is_delta);
-        DeltaFileName {
+        DeltaLayerName {
            key_range: self.key_range.clone(),
            lsn_range: self.lsn_range.clone(),
        }
    }

-    /// Get a delta file name for this layer.
+    /// Get a image layer name for this layer.
    ///
    /// Panic: if this is not an image layer, or the lsn range is invalid
-    pub fn image_file_name(&self) -> ImageFileName {
+    pub fn image_layer_name(&self) -> ImageLayerName {
        assert!(!self.is_delta);
        assert!(self.lsn_range.start + 1 == self.lsn_range.end);
-        ImageFileName {
+        ImageLayerName {
            key_range: self.key_range.clone(),
            lsn: self.lsn_range.start,
        }
    }

-    pub fn filename(&self) -> LayerFileName {
+    pub fn layer_name(&self) -> LayerName {
        if self.is_delta {
-            self.delta_file_name().into()
+            self.delta_layer_name().into()
        } else {
-            self.image_file_name().into()
+            self.image_layer_name().into()
        }
    }

--- a/pageserver/src/tenant/storage_layer/layer_name.rs
+++ b/pageserver/src/tenant/storage_layer/layer_name.rs
@@ -2,40 +2,42 @@
 //! Helper functions for dealing with filenames of the image and delta layer files.
 //!
 use crate::repository::Key;
+use std::borrow::Cow;
 use std::cmp::Ordering;
 use std::fmt;
 use std::ops::Range;
 use std::str::FromStr;

+use regex::Regex;
 use utils::lsn::Lsn;

 use super::PersistentLayerDesc;

 // Note: Timeline::load_layer_map() relies on this sort order
 #[derive(PartialEq, Eq, Clone, Hash)]
-pub struct DeltaFileName {
+pub struct DeltaLayerName {
    pub key_range: Range<Key>,
    pub lsn_range: Range<Lsn>,
 }

-impl std::fmt::Debug for DeltaFileName {
+impl std::fmt::Debug for DeltaLayerName {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        use super::RangeDisplayDebug;

-        f.debug_struct("DeltaFileName")
+        f.debug_struct("DeltaLayerName")
            .field("key_range", &RangeDisplayDebug(&self.key_range))
            .field("lsn_range", &self.lsn_range)
            .finish()
    }
 }

-impl PartialOrd for DeltaFileName {
+impl PartialOrd for DeltaLayerName {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
 }

-impl Ord for DeltaFileName {
+impl Ord for DeltaLayerName {
    fn cmp(&self, other: &Self) -> Ordering {
        let mut cmp = self.key_range.start.cmp(&other.key_range.start);
        if cmp != Ordering::Equal {
@@ -55,16 +57,14 @@ impl Ord for DeltaFileName {
    }
 }

-/// Represents the filename of a DeltaLayer
+/// Represents the region of the LSN-Key space covered by a DeltaLayer
 ///
 /// ```text
 ///    <key start>-<key end>__<LSN start>-<LSN end>
 /// ```
-impl DeltaFileName {
-    ///
-    /// Parse a string as a delta file name. Returns None if the filename does not
-    /// match the expected pattern.
-    ///
+impl DeltaLayerName {
+    /// Parse the part of a delta layer's file name that represents the LayerName. Returns None
+    /// if the filename does not match the expected pattern.
    pub fn parse_str(fname: &str) -> Option<Self> {
        let mut parts = fname.split("__");
        let mut key_parts = parts.next()?.split('-');
@@ -74,10 +74,19 @@ impl DeltaFileName {
        let key_end_str = key_parts.next()?;
        let lsn_start_str = lsn_parts.next()?;
        let lsn_end_str = lsn_parts.next()?;
+
        if parts.next().is_some() || key_parts.next().is_some() || key_parts.next().is_some() {
            return None;
        }

+        if key_start_str.len() != 36
+            || key_end_str.len() != 36
+            || lsn_start_str.len() != 16
+            || lsn_end_str.len() != 16
+        {
+            return None;
+        }
+
        let key_start = Key::from_hex(key_start_str).ok()?;
        let key_end = Key::from_hex(key_end_str).ok()?;

@@ -94,14 +103,14 @@ impl DeltaFileName {
            // or panic?
        }

-        Some(DeltaFileName {
+        Some(DeltaLayerName {
            key_range: key_start..key_end,
            lsn_range: start_lsn..end_lsn,
        })
    }
 }

-impl fmt::Display for DeltaFileName {
+impl fmt::Display for DeltaLayerName {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(
            f,
@@ -115,29 +124,29 @@ impl fmt::Display for DeltaFileName {
 }

 #[derive(PartialEq, Eq, Clone, Hash)]
-pub struct ImageFileName {
+pub struct ImageLayerName {
    pub key_range: Range<Key>,
    pub lsn: Lsn,
 }

-impl std::fmt::Debug for ImageFileName {
+impl std::fmt::Debug for ImageLayerName {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        use super::RangeDisplayDebug;

-        f.debug_struct("ImageFileName")
+        f.debug_struct("ImageLayerName")
            .field("key_range", &RangeDisplayDebug(&self.key_range))
            .field("lsn", &self.lsn)
            .finish()
    }
 }

-impl PartialOrd for ImageFileName {
+impl PartialOrd for ImageLayerName {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
 }

-impl Ord for ImageFileName {
+impl Ord for ImageLayerName {
    fn cmp(&self, other: &Self) -> Ordering {
        let mut cmp = self.key_range.start.cmp(&other.key_range.start);
        if cmp != Ordering::Equal {
@@ -153,7 +162,7 @@ impl Ord for ImageFileName {
    }
 }

-impl ImageFileName {
+impl ImageLayerName {
    pub fn lsn_as_range(&self) -> Range<Lsn> {
        // Saves from having to copypaste this all over
        PersistentLayerDesc::image_layer_lsn_range(self.lsn)
@@ -161,16 +170,14 @@ impl ImageFileName {
 }

 ///
-/// Represents the filename of an ImageLayer
+/// Represents the part of the Key-LSN space covered by an ImageLayer
 ///
 /// ```text
 ///    <key start>-<key end>__<LSN>
 /// ```
-impl ImageFileName {
-    ///
-    /// Parse a string as an image file name. Returns None if the filename does not
-    /// match the expected pattern.
-    ///
+impl ImageLayerName {
+    /// Parse a string as then LayerName part of an image layer file name. Returns None if the
+    /// filename does not match the expected pattern.
    pub fn parse_str(fname: &str) -> Option<Self> {
        let mut parts = fname.split("__");
        let mut key_parts = parts.next()?.split('-');
@@ -182,19 +189,23 @@ impl ImageFileName {
            return None;
        }

+        if key_start_str.len() != 36 || key_end_str.len() != 36 || lsn_str.len() != 16 {
+            return None;
+        }
+
        let key_start = Key::from_hex(key_start_str).ok()?;
        let key_end = Key::from_hex(key_end_str).ok()?;

        let lsn = Lsn::from_hex(lsn_str).ok()?;

-        Some(ImageFileName {
+        Some(ImageLayerName {
            key_range: key_start..key_end,
            lsn,
        })
    }
 }

-impl fmt::Display for ImageFileName {
+impl fmt::Display for ImageLayerName {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(
            f,
@@ -205,21 +216,24 @@ impl fmt::Display for ImageFileName {
        )
    }
 }
+
+/// LayerName is the logical identity of a layer within a LayerMap at a moment in time.  The
+/// LayerName is not a unique filename, as the same LayerName may have multiple physical incarnations
+/// over time (e.g. across shard splits or compression). The physical filenames of layers in local
+/// storage and object names in remote storage consist of the LayerName plus some extra qualifiers
+/// that uniquely identify the physical incarnation of a layer (see [crate::tenant::remote_timeline_client::remote_layer_path])
+/// and [`crate::tenant::storage_layer::layer::local_layer_path`])
 #[derive(Debug, PartialEq, Eq, Hash, Clone)]
-pub enum LayerFileName {
-    Image(ImageFileName),
-    Delta(DeltaFileName),
+pub enum LayerName {
+    Image(ImageLayerName),
+    Delta(DeltaLayerName),
 }

-impl LayerFileName {
-    pub fn file_name(&self) -> String {
-        self.to_string()
-    }
-
+impl LayerName {
    /// Determines if this layer file is considered to be in future meaning we will discard these
    /// layers during timeline initialization from the given disk_consistent_lsn.
    pub(crate) fn is_in_future(&self, disk_consistent_lsn: Lsn) -> bool {
-        use LayerFileName::*;
+        use LayerName::*;
        match self {
            Image(file_name) if file_name.lsn > disk_consistent_lsn => true,
            Delta(file_name) if file_name.lsn_range.end > disk_consistent_lsn + 1 => true,
@@ -228,7 +242,7 @@ impl LayerFileName {
    }

    pub(crate) fn kind(&self) -> &'static str {
-        use LayerFileName::*;
+        use LayerName::*;
        match self {
            Delta(_) => "delta",
            Image(_) => "image",
@@ -236,7 +250,7 @@ impl LayerFileName {
    }
 }

-impl fmt::Display for LayerFileName {
+impl fmt::Display for LayerName {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Image(fname) => write!(f, "{fname}"),
@@ -245,23 +259,36 @@ impl fmt::Display for LayerFileName {
    }
 }

-impl From<ImageFileName> for LayerFileName {
-    fn from(fname: ImageFileName) -> Self {
+impl From<ImageLayerName> for LayerName {
+    fn from(fname: ImageLayerName) -> Self {
        Self::Image(fname)
    }
 }
-impl From<DeltaFileName> for LayerFileName {
-    fn from(fname: DeltaFileName) -> Self {
+impl From<DeltaLayerName> for LayerName {
+    fn from(fname: DeltaLayerName) -> Self {
        Self::Delta(fname)
    }
 }

-impl FromStr for LayerFileName {
+impl FromStr for LayerName {
    type Err = String;

+    /// Conversion from either a physical layer filename, or the string-ization of
+    /// Self. When loading a physical layer filename, we drop any extra information
+    /// not needed to build Self.
    fn from_str(value: &str) -> Result<Self, Self::Err> {
-        let delta = DeltaFileName::parse_str(value);
-        let image = ImageFileName::parse_str(value);
+        let gen_suffix_regex = Regex::new("^(?<base>.+)(?<gen>-v1-[0-9a-f]{8})$").unwrap();
+        let file_name: Cow<str> = match gen_suffix_regex.captures(value) {
+            Some(captures) => captures
+                .name("base")
+                .expect("Non-optional group")
+                .as_str()
+                .into(),
+            None => value.into(),
+        };
+
+        let delta = DeltaLayerName::parse_str(&file_name);
+        let image = ImageLayerName::parse_str(&file_name);
        let ok = match (delta, image) {
            (None, None) => {
                return Err(format!(
@@ -276,7 +303,7 @@ impl FromStr for LayerFileName {
    }
 }

-impl serde::Serialize for LayerFileName {
+impl serde::Serialize for LayerName {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: serde::Serializer,
@@ -288,19 +315,19 @@ impl serde::Serialize for LayerFileName {
    }
 }

-impl<'de> serde::Deserialize<'de> for LayerFileName {
+impl<'de> serde::Deserialize<'de> for LayerName {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: serde::Deserializer<'de>,
    {
-        deserializer.deserialize_string(LayerFileNameVisitor)
+        deserializer.deserialize_string(LayerNameVisitor)
    }
 }

-struct LayerFileNameVisitor;
+struct LayerNameVisitor;

-impl<'de> serde::de::Visitor<'de> for LayerFileNameVisitor {
-    type Value = LayerFileName;
+impl<'de> serde::de::Visitor<'de> for LayerNameVisitor {
+    type Value = LayerName;

    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
        write!(
@@ -315,3 +342,42 @@ impl<'de> serde::de::Visitor<'de> for LayerFileNameVisitor {
        v.parse().map_err(|e| E::custom(e))
    }
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    #[test]
+    fn image_layer_parse() -> anyhow::Result<()> {
+        let expected = LayerName::Image(ImageLayerName {
+            key_range: Key::from_i128(0)
+                ..Key::from_hex("000000067F00000001000004DF0000000006").unwrap(),
+            lsn: Lsn::from_hex("00000000014FED58").unwrap(),
+        });
+        let parsed = LayerName::from_str("000000000000000000000000000000000000-000000067F00000001000004DF0000000006__00000000014FED58-v1-00000001").map_err(|s| anyhow::anyhow!(s))?;
+        assert_eq!(parsed, expected,);
+
+        // Omitting generation suffix is valid
+        let parsed = LayerName::from_str("000000000000000000000000000000000000-000000067F00000001000004DF0000000006__00000000014FED58").map_err(|s| anyhow::anyhow!(s))?;
+        assert_eq!(parsed, expected,);
+
+        Ok(())
+    }
+
+    #[test]
+    fn delta_layer_parse() -> anyhow::Result<()> {
+        let expected = LayerName::Delta(DeltaLayerName {
+            key_range: Key::from_i128(0)
+                ..Key::from_hex("000000067F00000001000004DF0000000006").unwrap(),
+            lsn_range: Lsn::from_hex("00000000014FED58").unwrap()
+                ..Lsn::from_hex("000000000154C481").unwrap(),
+        });
+        let parsed = LayerName::from_str("000000000000000000000000000000000000-000000067F00000001000004DF0000000006__00000000014FED58-000000000154C481-v1-00000001").map_err(|s| anyhow::anyhow!(s))?;
+        assert_eq!(parsed, expected);
+
+        // Omitting generation suffix is valid
+        let parsed = LayerName::from_str("000000000000000000000000000000000000-000000067F00000001000004DF0000000006__00000000014FED58-000000000154C481").map_err(|s| anyhow::anyhow!(s))?;
+        assert_eq!(parsed, expected);
+
+        Ok(())
+    }
+}
--- a/pageserver/src/tenant/tasks.rs
+++ b/pageserver/src/tenant/tasks.rs
@@ -2,6 +2,7 @@
 //! such as compaction and GC

 use std::ops::ControlFlow;
+use std::str::FromStr;
 use std::sync::Arc;
 use std::time::{Duration, Instant};

@@ -9,9 +10,11 @@ use crate::context::{DownloadBehavior, RequestContext};
 use crate::metrics::TENANT_TASK_EVENTS;
 use crate::task_mgr;
 use crate::task_mgr::{TaskKind, BACKGROUND_RUNTIME};
+use crate::tenant::config::defaults::DEFAULT_COMPACTION_PERIOD;
 use crate::tenant::throttle::Stats;
 use crate::tenant::timeline::CompactionError;
 use crate::tenant::{Tenant, TenantState};
+use rand::Rng;
 use tokio_util::sync::CancellationToken;
 use tracing::*;
 use utils::{backoff, completion};
@@ -38,12 +41,13 @@ static CONCURRENT_BACKGROUND_TASKS: once_cell::sync::Lazy<tokio::sync::Semaphore
        tokio::sync::Semaphore::new(permits)
    });

-#[derive(Debug, PartialEq, Eq, Clone, Copy, strum_macros::IntoStaticStr)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, strum_macros::IntoStaticStr, enum_map::Enum)]
 #[strum(serialize_all = "snake_case")]
 pub(crate) enum BackgroundLoopKind {
    Compaction,
    Gc,
    Eviction,
+    IngestHouseKeeping,
    ConsumptionMetricsCollectMetrics,
    ConsumptionMetricsSyntheticSizeWorker,
    InitialLogicalSizeCalculation,
@@ -53,19 +57,25 @@ pub(crate) enum BackgroundLoopKind {

 impl BackgroundLoopKind {
    fn as_static_str(&self) -> &'static str {
-        let s: &'static str = self.into();
-        s
+        self.into()
    }
 }

+static PERMIT_GAUGES: once_cell::sync::Lazy<
+    enum_map::EnumMap<BackgroundLoopKind, metrics::IntCounterPair>,
+> = once_cell::sync::Lazy::new(|| {
+    enum_map::EnumMap::from_array(std::array::from_fn(|i| {
+        let kind = <BackgroundLoopKind as enum_map::Enum>::from_usize(i);
+        crate::metrics::BACKGROUND_LOOP_SEMAPHORE_WAIT_GAUGE.with_label_values(&[kind.into()])
+    }))
+});
+
 /// Cancellation safe.
 pub(crate) async fn concurrent_background_tasks_rate_limit_permit(
    loop_kind: BackgroundLoopKind,
    _ctx: &RequestContext,
 ) -> tokio::sync::SemaphorePermit<'static> {
-    let _guard = crate::metrics::BACKGROUND_LOOP_SEMAPHORE_WAIT_GAUGE
-        .with_label_values(&[loop_kind.as_static_str()])
-        .guard();
+    let _guard = PERMIT_GAUGES[loop_kind].guard();

    pausable_failpoint!(
        "initial-size-calculation-permit-pause",
@@ -132,6 +142,30 @@ pub fn start_background_loops(
            }
        },
    );
+
+    task_mgr::spawn(
+        BACKGROUND_RUNTIME.handle(),
+        TaskKind::IngestHousekeeping,
+        Some(tenant_shard_id),
+        None,
+        &format!("ingest housekeeping for tenant {tenant_shard_id}"),
+        false,
+        {
+            let tenant = Arc::clone(tenant);
+            let background_jobs_can_start = background_jobs_can_start.cloned();
+            async move {
+                let cancel = task_mgr::shutdown_token();
+                tokio::select! {
+                    _ = cancel.cancelled() => { return Ok(()) },
+                    _ = completion::Barrier::maybe_wait(background_jobs_can_start) => {}
+                };
+                ingest_housekeeping_loop(tenant, cancel)
+                    .instrument(info_span!("ingest_housekeeping_loop", tenant_id = %tenant_shard_id.tenant_id, shard_id = %tenant_shard_id.shard_slug()))
+                    .await;
+                Ok(())
+            }
+        },
+    );
 }

 ///
@@ -379,6 +413,61 @@ async fn gc_loop(tenant: Arc<Tenant>, cancel: CancellationToken) {
    TENANT_TASK_EVENTS.with_label_values(&["stop"]).inc();
 }

+async fn ingest_housekeeping_loop(tenant: Arc<Tenant>, cancel: CancellationToken) {
+    TENANT_TASK_EVENTS.with_label_values(&["start"]).inc();
+    async {
+        loop {
+            tokio::select! {
+                _ = cancel.cancelled() => {
+                    return;
+                },
+                tenant_wait_result = wait_for_active_tenant(&tenant) => match tenant_wait_result {
+                    ControlFlow::Break(()) => return,
+                    ControlFlow::Continue(()) => (),
+                },
+            }
+
+            // We run ingest housekeeping with the same frequency as compaction: it is not worth
+            // having a distinct setting.  But we don't run it in the same task, because compaction
+            // blocks on acquiring the background job semaphore.
+            let period = tenant.get_compaction_period();
+
+            // If compaction period is set to zero (to disable it), then we will use a reasonable default
+            let period = if period == Duration::ZERO {
+                humantime::Duration::from_str(DEFAULT_COMPACTION_PERIOD)
+                    .unwrap()
+                    .into()
+            } else {
+                period
+            };
+
+            // Jitter the period by +/- 5%
+            let period =
+                rand::thread_rng().gen_range((period * (95)) / 100..(period * (105)) / 100);
+
+            // Always sleep first: we do not need to do ingest housekeeping early in the lifetime of
+            // a tenant, since it won't have started writing any ephemeral files yet.
+            if tokio::time::timeout(period, cancel.cancelled())
+                .await
+                .is_ok()
+            {
+                break;
+            }
+
+            let started_at = Instant::now();
+            tenant.ingest_housekeeping().await;
+
+            warn_when_period_overrun(
+                started_at.elapsed(),
+                period,
+                BackgroundLoopKind::IngestHouseKeeping,
+            );
+        }
+    }
+    .await;
+    TENANT_TASK_EVENTS.with_label_values(&["stop"]).inc();
+}
+
 async fn wait_for_active_tenant(tenant: &Arc<Tenant>) -> ControlFlow<()> {
    // if the tenant has a proper status already, no need to wait for anything
    if tenant.current_state() == TenantState::Active {
@@ -420,8 +509,6 @@ pub(crate) async fn random_init_delay(
    period: Duration,
    cancel: &CancellationToken,
 ) -> Result<(), Cancelled> {
-    use rand::Rng;
-
    if period == Duration::ZERO {
        return Ok(());
    }
--- a/pageserver/src/tenant/timeline.rs
+++ b/pageserver/src/tenant/timeline.rs
--- a/pageserver/src/tenant/timeline/compaction.rs
+++ b/pageserver/src/tenant/timeline/compaction.rs
@@ -15,7 +15,8 @@ use anyhow::{anyhow, Context};
 use enumset::EnumSet;
 use fail::fail_point;
 use itertools::Itertools;
-use pageserver_api::shard::{ShardIdentity, TenantShardId};
+use pageserver_api::keyspace::ShardedRange;
+use pageserver_api::shard::{ShardCount, ShardIdentity, TenantShardId};
 use tokio_util::sync::CancellationToken;
 use tracing::{debug, info, info_span, trace, warn, Instrument};
 use utils::id::TimelineId;
@@ -93,7 +94,7 @@ impl Timeline {
        // Define partitioning schema if needed

        // FIXME: the match should only cover repartitioning, not the next steps
-        match self
+        let partition_count = match self
            .repartition(
                self.get_last_record_lsn(),
                self.get_compaction_target_size(),
@@ -146,6 +147,7 @@ impl Timeline {
                assert!(sparse_layers.is_empty());

                self.upload_new_image_layers(dense_layers)?;
+                dense_partitioning.parts.len()
            }
            Err(err) => {
                // no partitioning? This is normal, if the timeline was just created
@@ -157,9 +159,150 @@ impl Timeline {
                if !self.cancel.is_cancelled() {
                    tracing::error!("could not compact, repartitioning keyspace failed: {err:?}");
                }
+                1
            }
        };

+        if self.shard_identity.count >= ShardCount::new(2) {
+            // Limit the number of layer rewrites to the number of partitions: this means its
+            // runtime should be comparable to a full round of image layer creations, rather than
+            // being potentially much longer.
+            let rewrite_max = partition_count;
+
+            self.compact_shard_ancestors(rewrite_max, ctx).await?;
+        }
+
+        Ok(())
+    }
+
+    /// Check for layers that are elegible to be rewritten:
+    /// - Shard splitting: After a shard split, ancestor layers beyond pitr_interval, so that
+    ///   we don't indefinitely retain keys in this shard that aren't needed.
+    /// - For future use: layers beyond pitr_interval that are in formats we would
+    ///   rather not maintain compatibility with indefinitely.
+    ///
+    /// Note: this phase may read and write many gigabytes of data: use rewrite_max to bound
+    /// how much work it will try to do in each compaction pass.
+    async fn compact_shard_ancestors(
+        self: &Arc<Self>,
+        rewrite_max: usize,
+        _ctx: &RequestContext,
+    ) -> anyhow::Result<()> {
+        let mut drop_layers = Vec::new();
+        let layers_to_rewrite: Vec<Layer> = Vec::new();
+
+        // We will use the PITR cutoff as a condition for rewriting layers.
+        let pitr_cutoff = self.gc_info.read().unwrap().cutoffs.pitr;
+
+        let layers = self.layers.read().await;
+        for layer_desc in layers.layer_map().iter_historic_layers() {
+            let layer = layers.get_from_desc(&layer_desc);
+            if layer.metadata().shard.shard_count == self.shard_identity.count {
+                // This layer does not belong to a historic ancestor, no need to re-image it.
+                continue;
+            }
+
+            // This layer was created on an ancestor shard: check if it contains any data for this shard.
+            let sharded_range = ShardedRange::new(layer_desc.get_key_range(), &self.shard_identity);
+            let layer_local_page_count = sharded_range.page_count();
+            let layer_raw_page_count = ShardedRange::raw_size(&layer_desc.get_key_range());
+            if layer_local_page_count == 0 {
+                // This ancestral layer only covers keys that belong to other shards.
+                // We include the full metadata in the log: if we had some critical bug that caused
+                // us to incorrectly drop layers, this would simplify manually debugging + reinstating those layers.
+                info!(%layer, old_metadata=?layer.metadata(),
+                    "dropping layer after shard split, contains no keys for this shard.",
+                );
+
+                if cfg!(debug_assertions) {
+                    // Expensive, exhaustive check of keys in this layer: this guards against ShardedRange's calculations being
+                    // wrong.  If ShardedRange claims the local page count is zero, then no keys in this layer
+                    // should be !is_key_disposable()
+                    let range = layer_desc.get_key_range();
+                    let mut key = range.start;
+                    while key < range.end {
+                        debug_assert!(self.shard_identity.is_key_disposable(&key));
+                        key = key.next();
+                    }
+                }
+
+                drop_layers.push(layer);
+                continue;
+            } else if layer_local_page_count != u32::MAX
+                && layer_local_page_count == layer_raw_page_count
+            {
+                debug!(%layer,
+                    "layer is entirely shard local ({} keys), no need to filter it",
+                    layer_local_page_count
+                );
+                continue;
+            }
+
+            // Don't bother re-writing a layer unless it will at least halve its size
+            if layer_local_page_count != u32::MAX
+                && layer_local_page_count > layer_raw_page_count / 2
+            {
+                debug!(%layer,
+                    "layer is already mostly local ({}/{}), not rewriting",
+                    layer_local_page_count,
+                    layer_raw_page_count
+                );
+            }
+
+            // Don't bother re-writing a layer if it is within the PITR window: it will age-out eventually
+            // without incurring the I/O cost of a rewrite.
+            if layer_desc.get_lsn_range().end >= pitr_cutoff {
+                debug!(%layer, "Skipping rewrite of layer still in PITR window ({} >= {})",
+                    layer_desc.get_lsn_range().end, pitr_cutoff);
+                continue;
+            }
+
+            if layer_desc.is_delta() {
+                // We do not yet implement rewrite of delta layers
+                debug!(%layer, "Skipping rewrite of delta layer");
+                continue;
+            }
+
+            // Only rewrite layers if they would have different remote paths: either they belong to this
+            // shard but an old generation, or they belonged to another shard.  This also implicitly
+            // guarantees that the layer is persistent in remote storage (as only remote persistent
+            // layers are carried across shard splits, any local-only layer would be in the current generation)
+            if layer.metadata().generation == self.generation
+                && layer.metadata().shard.shard_count == self.shard_identity.count
+            {
+                debug!(%layer, "Skipping rewrite, is not from old generation");
+                continue;
+            }
+
+            if layers_to_rewrite.len() >= rewrite_max {
+                tracing::info!(%layer, "Will rewrite layer on a future compaction, already rewrote {}",
+                    layers_to_rewrite.len()
+                );
+                continue;
+            }
+
+            // Fall through: all our conditions for doing a rewrite passed.
+            // TODO: implement rewriting
+            tracing::debug!(%layer, "Would rewrite layer");
+        }
+
+        // Drop the layers read lock: we will acquire it for write in [`Self::rewrite_layers`]
+        drop(layers);
+
+        // TODO: collect layers to rewrite
+        let replace_layers = Vec::new();
+
+        // Update the LayerMap so that readers will use the new layers, and enqueue it for writing to remote storage
+        self.rewrite_layers(replace_layers, drop_layers).await?;
+
+        if let Some(remote_client) = self.remote_client.as_ref() {
+            // We wait for all uploads to complete before finishing this compaction stage.  This is not
+            // necessary for correctness, but it simplifies testing, and avoids proceeding with another
+            // Timeline's compaction while this timeline's uploads may be generating lots of disk I/O
+            // load.
+            remote_client.wait_completion().await?;
+        }
+
        Ok(())
    }

@@ -520,7 +663,7 @@ impl Timeline {
                            writer
                                .take()
                                .unwrap()
-                                .finish(prev_key.unwrap().next(), self)
+                                .finish(prev_key.unwrap().next(), self, ctx)
                                .await?,
                        );
                        writer = None;
@@ -557,12 +700,17 @@ impl Timeline {
                                debug!("Create new layer {}..{}", lsn_range.start, lsn_range.end);
                                lsn_range.clone()
                            },
+                            ctx,
                        )
                        .await?,
                    );
                }

-                writer.as_mut().unwrap().put_value(key, lsn, value).await?;
+                writer
+                    .as_mut()
+                    .unwrap()
+                    .put_value(key, lsn, value, ctx)
+                    .await?;
            } else {
                debug!(
                    "Dropping key {} during compaction (it belongs on shard {:?})",
@@ -578,7 +726,7 @@ impl Timeline {
            prev_key = Some(key);
        }
        if let Some(writer) = writer {
-            new_layers.push(writer.finish(prev_key.unwrap().next(), self).await?);
+            new_layers.push(writer.finish(prev_key.unwrap().next(), self, ctx).await?);
        }

        // Sync layers
@@ -608,6 +756,7 @@ impl Timeline {
                &self
                    .conf
                    .timeline_path(&self.tenant_shard_id, &self.timeline_id),
+                ctx,
            )
            .await
            .fatal_err("VirtualFile::open for timeline dir fsync");
@@ -946,6 +1095,7 @@ impl CompactionJobExecutor for TimelineAdaptor {
            self.timeline.tenant_shard_id,
            key_range.start,
            lsn_range.clone(),
+            ctx,
        )
        .await?;

@@ -972,7 +1122,7 @@ impl CompactionJobExecutor for TimelineAdaptor {

            let value = val.load(ctx).await?;

-            writer.put_value(key, lsn, value).await?;
+            writer.put_value(key, lsn, value, ctx).await?;

            prev = Some((key, lsn));
        }
@@ -988,7 +1138,7 @@ impl CompactionJobExecutor for TimelineAdaptor {
        });

        let new_delta_layer = writer
-            .finish(prev.unwrap().0.next(), &self.timeline)
+            .finish(prev.unwrap().0.next(), &self.timeline, ctx)
            .await?;

        self.new_deltas.push(new_delta_layer);
@@ -1020,6 +1170,7 @@ impl TimelineAdaptor {
            self.timeline.tenant_shard_id,
            key_range,
            lsn,
+            ctx,
        )
        .await?;

@@ -1058,11 +1209,11 @@ impl TimelineAdaptor {
                        }
                    }
                };
-                image_layer_writer.put_image(key, img).await?;
+                image_layer_writer.put_image(key, img, ctx).await?;
                key = key.next();
            }
        }
-        let image_layer = image_layer_writer.finish(&self.timeline).await?;
+        let image_layer = image_layer_writer.finish(&self.timeline, ctx).await?;

        self.new_images.push(image_layer);

--- a/pageserver/src/tenant/timeline/delete.rs
+++ b/pageserver/src/tenant/timeline/delete.rs
@@ -422,6 +422,10 @@ impl DeleteTimelineFlow {
    pub(crate) fn is_finished(&self) -> bool {
        matches!(self, Self::Finished)
    }
+
+    pub(crate) fn is_not_started(&self) -> bool {
+        matches!(self, Self::NotStarted)
+    }
 }

 struct DeletionGuard(OwnedMutexGuard<DeleteTimelineFlow>);
--- a/pageserver/src/tenant/timeline/detach_ancestor.rs
+++ b/pageserver/src/tenant/timeline/detach_ancestor.rs
@@ -0,0 +1,542 @@
+use std::sync::Arc;
+
+use super::{layer_manager::LayerManager, Timeline};
+use crate::{
+    context::{DownloadBehavior, RequestContext},
+    task_mgr::TaskKind,
+    tenant::{
+        storage_layer::{AsLayerDesc as _, DeltaLayerWriter, Layer, ResidentLayer},
+        Tenant,
+    },
+    virtual_file::{MaybeFatalIo, VirtualFile},
+};
+use tokio_util::sync::CancellationToken;
+use tracing::Instrument;
+use utils::{completion, generation::Generation, id::TimelineId, lsn::Lsn};
+
+#[derive(Debug, thiserror::Error)]
+pub(crate) enum Error {
+    #[error("no ancestors")]
+    NoAncestor,
+    #[error("too many ancestors")]
+    TooManyAncestors,
+    #[error("shutting down, please retry later")]
+    ShuttingDown,
+    #[error("flushing failed")]
+    FlushAncestor(#[source] anyhow::Error),
+    #[error("layer download failed")]
+    RewrittenDeltaDownloadFailed(#[source] anyhow::Error),
+    #[error("copying LSN prefix locally failed")]
+    CopyDeltaPrefix(#[source] anyhow::Error),
+    #[error("upload rewritten layer")]
+    UploadRewritten(#[source] anyhow::Error),
+
+    #[error("ancestor is already being detached by: {}", .0)]
+    OtherTimelineDetachOngoing(TimelineId),
+
+    #[error("remote copying layer failed")]
+    CopyFailed(#[source] anyhow::Error),
+
+    #[error("unexpected error")]
+    Unexpected(#[source] anyhow::Error),
+}
+
+pub(crate) struct PreparedTimelineDetach {
+    layers: Vec<Layer>,
+}
+
+/// TODO: this should be part of PageserverConf because we cannot easily modify cplane arguments.
+#[derive(Debug)]
+pub(crate) struct Options {
+    pub(crate) rewrite_concurrency: std::num::NonZeroUsize,
+    pub(crate) copy_concurrency: std::num::NonZeroUsize,
+}
+
+impl Default for Options {
+    fn default() -> Self {
+        Self {
+            rewrite_concurrency: std::num::NonZeroUsize::new(2).unwrap(),
+            copy_concurrency: std::num::NonZeroUsize::new(10).unwrap(),
+        }
+    }
+}
+
+/// See [`Timeline::prepare_to_detach_from_ancestor`]
+pub(super) async fn prepare(
+    detached: &Arc<Timeline>,
+    tenant: &Tenant,
+    options: Options,
+    ctx: &RequestContext,
+) -> Result<(completion::Completion, PreparedTimelineDetach), Error> {
+    use Error::*;
+
+    if detached.remote_client.as_ref().is_none() {
+        unimplemented!("no new code for running without remote storage");
+    }
+
+    let Some((ancestor, ancestor_lsn)) = detached
+        .ancestor_timeline
+        .as_ref()
+        .map(|tl| (tl.clone(), detached.ancestor_lsn))
+    else {
+        return Err(NoAncestor);
+    };
+
+    if !ancestor_lsn.is_valid() {
+        return Err(NoAncestor);
+    }
+
+    if ancestor.ancestor_timeline.is_some() {
+        // non-technical requirement; we could flatten N ancestors just as easily but we chose
+        // not to
+        return Err(TooManyAncestors);
+    }
+
+    // before we acquire the gate, we must mark the ancestor as having a detach operation
+    // ongoing which will block other concurrent detach operations so we don't get to ackward
+    // situations where there would be two branches trying to reparent earlier branches.
+    let (guard, barrier) = completion::channel();
+
+    {
+        let mut guard = tenant.ongoing_timeline_detach.lock().unwrap();
+        if let Some((tl, other)) = guard.as_ref() {
+            if !other.is_ready() {
+                return Err(OtherTimelineDetachOngoing(*tl));
+            }
+        }
+        *guard = Some((detached.timeline_id, barrier));
+    }
+
+    let _gate_entered = detached.gate.enter().map_err(|_| ShuttingDown)?;
+
+    if ancestor_lsn >= ancestor.get_disk_consistent_lsn() {
+        let span =
+            tracing::info_span!("freeze_and_flush", ancestor_timeline_id=%ancestor.timeline_id);
+        async {
+            let started_at = std::time::Instant::now();
+            let freeze_and_flush = ancestor.freeze_and_flush0();
+            let mut freeze_and_flush = std::pin::pin!(freeze_and_flush);
+
+            let res =
+                tokio::time::timeout(std::time::Duration::from_secs(1), &mut freeze_and_flush)
+                    .await;
+
+            let res = match res {
+                Ok(res) => res,
+                Err(_elapsed) => {
+                    tracing::info!("freezing and flushing ancestor is still ongoing");
+                    freeze_and_flush.await
+                }
+            };
+
+            res.map_err(FlushAncestor)?;
+
+            // we do not need to wait for uploads to complete but we do need `struct Layer`,
+            // copying delta prefix is unsupported currently for `InMemoryLayer`.
+            tracing::info!(
+                elapsed_ms = started_at.elapsed().as_millis(),
+                "froze and flushed the ancestor"
+            );
+            Ok(())
+        }
+        .instrument(span)
+        .await?;
+    }
+
+    let end_lsn = ancestor_lsn + 1;
+
+    let (filtered_layers, straddling_branchpoint, rest_of_historic) = {
+        // we do not need to start from our layers, because they can only be layers that come
+        // *after* ancestor_lsn
+        let layers = tokio::select! {
+            guard = ancestor.layers.read() => guard,
+            _ = detached.cancel.cancelled() => {
+                return Err(ShuttingDown);
+            }
+            _ = ancestor.cancel.cancelled() => {
+                return Err(ShuttingDown);
+            }
+        };
+
+        // between retries, these can change if compaction or gc ran in between. this will mean
+        // we have to redo work.
+        partition_work(ancestor_lsn, &layers)
+    };
+
+    // TODO: layers are already sorted by something: use that to determine how much of remote
+    // copies are already done.
+    tracing::info!(filtered=%filtered_layers, to_rewrite = straddling_branchpoint.len(), historic=%rest_of_historic.len(), "collected layers");
+
+    // TODO: copying and lsn prefix copying could be done at the same time with a single fsync after
+    let mut new_layers: Vec<Layer> =
+        Vec::with_capacity(straddling_branchpoint.len() + rest_of_historic.len());
+
+    {
+        tracing::debug!(to_rewrite = %straddling_branchpoint.len(), "copying prefix of delta layers");
+
+        let mut tasks = tokio::task::JoinSet::new();
+
+        let mut wrote_any = false;
+
+        let limiter = Arc::new(tokio::sync::Semaphore::new(
+            options.rewrite_concurrency.get(),
+        ));
+
+        for layer in straddling_branchpoint {
+            let limiter = limiter.clone();
+            let timeline = detached.clone();
+            let ctx = ctx.detached_child(TaskKind::DetachAncestor, DownloadBehavior::Download);
+
+            tasks.spawn(async move {
+                let _permit = limiter.acquire().await;
+                let copied =
+                    upload_rewritten_layer(end_lsn, &layer, &timeline, &timeline.cancel, &ctx)
+                        .await?;
+                Ok(copied)
+            });
+        }
+
+        while let Some(res) = tasks.join_next().await {
+            match res {
+                Ok(Ok(Some(copied))) => {
+                    wrote_any = true;
+                    tracing::info!(layer=%copied, "rewrote and uploaded");
+                    new_layers.push(copied);
+                }
+                Ok(Ok(None)) => {}
+                Ok(Err(e)) => return Err(e),
+                Err(je) => return Err(Unexpected(je.into())),
+            }
+        }
+
+        // FIXME: the fsync should be mandatory, after both rewrites and copies
+        if wrote_any {
+            let timeline_dir = VirtualFile::open(
+                &detached
+                    .conf
+                    .timeline_path(&detached.tenant_shard_id, &detached.timeline_id),
+                ctx,
+            )
+            .await
+            .fatal_err("VirtualFile::open for timeline dir fsync");
+            timeline_dir
+                .sync_all()
+                .await
+                .fatal_err("VirtualFile::sync_all timeline dir");
+        }
+    }
+
+    let mut tasks = tokio::task::JoinSet::new();
+    let limiter = Arc::new(tokio::sync::Semaphore::new(options.copy_concurrency.get()));
+
+    for adopted in rest_of_historic {
+        let limiter = limiter.clone();
+        let timeline = detached.clone();
+
+        tasks.spawn(
+            async move {
+                let _permit = limiter.acquire().await;
+                let owned =
+                    remote_copy(&adopted, &timeline, timeline.generation, &timeline.cancel).await?;
+                tracing::info!(layer=%owned, "remote copied");
+                Ok(owned)
+            }
+            .in_current_span(),
+        );
+    }
+
+    while let Some(res) = tasks.join_next().await {
+        match res {
+            Ok(Ok(owned)) => {
+                new_layers.push(owned);
+            }
+            Ok(Err(failed)) => {
+                return Err(failed);
+            }
+            Err(je) => return Err(Unexpected(je.into())),
+        }
+    }
+
+    // TODO: fsync directory again if we hardlinked something
+
+    let prepared = PreparedTimelineDetach { layers: new_layers };
+
+    Ok((guard, prepared))
+}
+
+fn partition_work(
+    ancestor_lsn: Lsn,
+    source_layermap: &LayerManager,
+) -> (usize, Vec<Layer>, Vec<Layer>) {
+    let mut straddling_branchpoint = vec![];
+    let mut rest_of_historic = vec![];
+
+    let mut later_by_lsn = 0;
+
+    for desc in source_layermap.layer_map().iter_historic_layers() {
+        // off by one chances here:
+        // - start is inclusive
+        // - end is exclusive
+        if desc.lsn_range.start > ancestor_lsn {
+            later_by_lsn += 1;
+            continue;
+        }
+
+        let target = if desc.lsn_range.start <= ancestor_lsn
+            && desc.lsn_range.end > ancestor_lsn
+            && desc.is_delta
+        {
+            // TODO: image layer at Lsn optimization
+            &mut straddling_branchpoint
+        } else {
+            &mut rest_of_historic
+        };
+
+        target.push(source_layermap.get_from_desc(&desc));
+    }
+
+    (later_by_lsn, straddling_branchpoint, rest_of_historic)
+}
+
+async fn upload_rewritten_layer(
+    end_lsn: Lsn,
+    layer: &Layer,
+    target: &Arc<Timeline>,
+    cancel: &CancellationToken,
+    ctx: &RequestContext,
+) -> Result<Option<Layer>, Error> {
+    use Error::UploadRewritten;
+    let copied = copy_lsn_prefix(end_lsn, layer, target, ctx).await?;
+
+    let Some(copied) = copied else {
+        return Ok(None);
+    };
+
+    // FIXME: better shuttingdown error
+    target
+        .remote_client
+        .as_ref()
+        .unwrap()
+        .upload_layer_file(&copied, cancel)
+        .await
+        .map_err(UploadRewritten)?;
+
+    Ok(Some(copied.into()))
+}
+
+async fn copy_lsn_prefix(
+    end_lsn: Lsn,
+    layer: &Layer,
+    target_timeline: &Arc<Timeline>,
+    ctx: &RequestContext,
+) -> Result<Option<ResidentLayer>, Error> {
+    use Error::{CopyDeltaPrefix, RewrittenDeltaDownloadFailed};
+
+    tracing::debug!(%layer, %end_lsn, "copying lsn prefix");
+
+    let mut writer = DeltaLayerWriter::new(
+        target_timeline.conf,
+        target_timeline.timeline_id,
+        target_timeline.tenant_shard_id,
+        layer.layer_desc().key_range.start,
+        layer.layer_desc().lsn_range.start..end_lsn,
+        ctx,
+    )
+    .await
+    .map_err(CopyDeltaPrefix)?;
+
+    let resident = layer
+        .download_and_keep_resident()
+        .await
+        // likely shutdown
+        .map_err(RewrittenDeltaDownloadFailed)?;
+
+    let records = resident
+        .copy_delta_prefix(&mut writer, end_lsn, ctx)
+        .await
+        .map_err(CopyDeltaPrefix)?;
+
+    drop(resident);
+
+    tracing::debug!(%layer, records, "copied records");
+
+    if records == 0 {
+        drop(writer);
+        // TODO: we might want to store an empty marker in remote storage for this
+        // layer so that we will not needlessly walk `layer` on repeated attempts.
+        Ok(None)
+    } else {
+        // reuse the key instead of adding more holes between layers by using the real
+        // highest key in the layer.
+        let reused_highest_key = layer.layer_desc().key_range.end;
+        let copied = writer
+            .finish(reused_highest_key, target_timeline, ctx)
+            .await
+            .map_err(CopyDeltaPrefix)?;
+
+        tracing::debug!(%layer, %copied, "new layer produced");
+
+        Ok(Some(copied))
+    }
+}
+
+/// Creates a new Layer instance for the adopted layer, and ensures it is found from the remote
+/// storage on successful return without the adopted layer being added to `index_part.json`.
+async fn remote_copy(
+    adopted: &Layer,
+    adoptee: &Arc<Timeline>,
+    generation: Generation,
+    cancel: &CancellationToken,
+) -> Result<Layer, Error> {
+    use Error::CopyFailed;
+
+    // depending if Layer::keep_resident we could hardlink
+
+    let mut metadata = adopted.metadata();
+    debug_assert!(metadata.generation <= generation);
+    metadata.generation = generation;
+
+    let owned = crate::tenant::storage_layer::Layer::for_evicted(
+        adoptee.conf,
+        adoptee,
+        adopted.layer_desc().layer_name(),
+        metadata,
+    );
+
+    // FIXME: better shuttingdown error
+    adoptee
+        .remote_client
+        .as_ref()
+        .unwrap()
+        .copy_timeline_layer(adopted, &owned, cancel)
+        .await
+        .map(move |()| owned)
+        .map_err(CopyFailed)
+}
+
+/// See [`Timeline::complete_detaching_timeline_ancestor`].
+pub(super) async fn complete(
+    detached: &Arc<Timeline>,
+    tenant: &Tenant,
+    prepared: PreparedTimelineDetach,
+    _ctx: &RequestContext,
+) -> Result<Vec<TimelineId>, anyhow::Error> {
+    let rtc = detached
+        .remote_client
+        .as_ref()
+        .expect("has to have a remote timeline client for timeline ancestor detach");
+
+    let PreparedTimelineDetach { layers } = prepared;
+
+    let ancestor = detached
+        .get_ancestor_timeline()
+        .expect("must still have a ancestor");
+    let ancestor_lsn = detached.get_ancestor_lsn();
+
+    // publish the prepared layers before we reparent any of the timelines, so that on restart
+    // reparented timelines find layers. also do the actual detaching.
+    //
+    // if we crash after this operation, we will at least come up having detached a timeline, but
+    // we cannot go back and reparent the timelines which would had been reparented in normal
+    // execution.
+    //
+    // this is not perfect, but it avoids us a retry happening after a compaction or gc on restart
+    // which could give us a completely wrong layer combination.
+    rtc.schedule_adding_existing_layers_to_index_detach_and_wait(
+        &layers,
+        (ancestor.timeline_id, ancestor_lsn),
+    )
+    .await?;
+
+    let mut tasks = tokio::task::JoinSet::new();
+
+    // because we are now keeping the slot in progress, it is unlikely that there will be any
+    // timeline deletions during this time. if we raced one, then we'll just ignore it.
+    tenant
+        .timelines
+        .lock()
+        .unwrap()
+        .values()
+        .filter_map(|tl| {
+            if Arc::ptr_eq(tl, detached) {
+                return None;
+            }
+
+            if !tl.is_active() {
+                return None;
+            }
+
+            let tl_ancestor = tl.ancestor_timeline.as_ref()?;
+            let is_same = Arc::ptr_eq(&ancestor, tl_ancestor);
+            let is_earlier = tl.get_ancestor_lsn() <= ancestor_lsn;
+
+            let is_deleting = tl
+                .delete_progress
+                .try_lock()
+                .map(|flow| !flow.is_not_started())
+                .unwrap_or(true);
+
+            if is_same && is_earlier && !is_deleting {
+                Some(tl.clone())
+            } else {
+                None
+            }
+        })
+        .for_each(|timeline| {
+            // important in this scope: we are holding the Tenant::timelines lock
+            let span = tracing::info_span!("reparent", reparented=%timeline.timeline_id);
+            let new_parent = detached.timeline_id;
+
+            tasks.spawn(
+                async move {
+                    let res = timeline
+                        .remote_client
+                        .as_ref()
+                        .expect("reparented has to have remote client because detached has one")
+                        .schedule_reparenting_and_wait(&new_parent)
+                        .await;
+
+                    match res {
+                        Ok(()) => Some(timeline),
+                        Err(e) => {
+                            // with the use of tenant slot, we no longer expect these.
+                            tracing::warn!("reparenting failed: {e:#}");
+                            None
+                        }
+                    }
+                }
+                .instrument(span),
+            );
+        });
+
+    let reparenting_candidates = tasks.len();
+    let mut reparented = Vec::with_capacity(tasks.len());
+
+    while let Some(res) = tasks.join_next().await {
+        match res {
+            Ok(Some(timeline)) => {
+                tracing::info!(reparented=%timeline.timeline_id, "reparenting done");
+                reparented.push(timeline.timeline_id);
+            }
+            Ok(None) => {
+                // lets just ignore this for now. one or all reparented timelines could had
+                // started deletion, and that is fine.
+            }
+            Err(je) if je.is_cancelled() => unreachable!("not used"),
+            Err(je) if je.is_panic() => {
+                // ignore; it's better to continue with a single reparenting failing (or even
+                // all of them) in order to get to the goal state.
+                //
+                // these timelines will never be reparentable, but they can be always detached as
+                // separate tree roots.
+            }
+            Err(je) => tracing::error!("unexpected join error: {je:?}"),
+        }
+    }
+
+    if reparenting_candidates != reparented.len() {
+        tracing::info!("failed to reparent some candidates");
+    }
+
+    Ok(reparented)
+}
--- a/pageserver/src/tenant/timeline/init.rs
+++ b/pageserver/src/tenant/timeline/init.rs
@@ -6,13 +6,13 @@ use crate::{
            self,
            index::{IndexPart, LayerFileMetadata},
        },
-        storage_layer::LayerFileName,
+        storage_layer::LayerName,
        Generation,
    },
    METADATA_FILE_NAME,
 };
 use anyhow::Context;
-use camino::Utf8Path;
+use camino::{Utf8Path, Utf8PathBuf};
 use pageserver_api::shard::ShardIndex;
 use std::{collections::HashMap, str::FromStr};
 use utils::lsn::Lsn;
@@ -20,7 +20,7 @@ use utils::lsn::Lsn;
 /// Identified files in the timeline directory.
 pub(super) enum Discovered {
    /// The only one we care about
-    Layer(LayerFileName, u64),
+    Layer(LayerName, Utf8PathBuf, u64),
    /// Old ephmeral files from previous launches, should be removed
    Ephemeral(String),
    /// Old temporary timeline files, unsure what these really are, should be removed
@@ -43,10 +43,10 @@ pub(super) fn scan_timeline_dir(path: &Utf8Path) -> anyhow::Result<Vec<Discovere
        let direntry = direntry?;
        let file_name = direntry.file_name().to_string();

-        let discovered = match LayerFileName::from_str(&file_name) {
+        let discovered = match LayerName::from_str(&file_name) {
            Ok(file_name) => {
                let file_size = direntry.metadata()?.len();
-                Discovered::Layer(file_name, file_size)
+                Discovered::Layer(file_name, direntry.path().to_owned(), file_size)
            }
            Err(_) => {
                if file_name == METADATA_FILE_NAME {
@@ -72,6 +72,28 @@ pub(super) fn scan_timeline_dir(path: &Utf8Path) -> anyhow::Result<Vec<Discovere
    Ok(ret)
 }

+/// Whereas `LayerFileMetadata` describes the metadata we would store in remote storage,
+/// this structure extends it with metadata describing the layer's presence in local storage.
+#[derive(Clone, Debug)]
+pub(super) struct LocalLayerFileMetadata {
+    pub(super) metadata: LayerFileMetadata,
+    pub(super) local_path: Utf8PathBuf,
+}
+
+impl LocalLayerFileMetadata {
+    pub fn new(
+        local_path: Utf8PathBuf,
+        file_size: u64,
+        generation: Generation,
+        shard: ShardIndex,
+    ) -> Self {
+        Self {
+            local_path,
+            metadata: LayerFileMetadata::new(file_size, generation, shard),
+        }
+    }
+}
+
 /// Decision on what to do with a layer file after considering its local and remote metadata.
 #[derive(Clone, Debug)]
 pub(super) enum Decision {
@@ -80,11 +102,11 @@ pub(super) enum Decision {
    /// The layer is present locally, but local metadata does not match remote; we must
    /// delete it and treat it as evicted.
    UseRemote {
-        local: LayerFileMetadata,
+        local: LocalLayerFileMetadata,
        remote: LayerFileMetadata,
    },
    /// The layer is present locally, and metadata matches.
-    UseLocal(LayerFileMetadata),
+    UseLocal(LocalLayerFileMetadata),
 }

 /// A layer needs to be left out of the layer map.
@@ -92,39 +114,42 @@ pub(super) enum Decision {
 pub(super) enum DismissedLayer {
    /// The related layer is is in future compared to disk_consistent_lsn, it must not be loaded.
    Future {
-        /// The local metadata. `None` if the layer is only known through [`IndexPart`].
-        local: Option<LayerFileMetadata>,
+        /// `None` if the layer is only known through [`IndexPart`].
+        local: Option<LocalLayerFileMetadata>,
    },
    /// The layer only exists locally.
    ///
    /// In order to make crash safe updates to layer map, we must dismiss layers which are only
    /// found locally or not yet included in the remote `index_part.json`.
-    LocalOnly(LayerFileMetadata),
+    LocalOnly(LocalLayerFileMetadata),
 }

 /// Merges local discoveries and remote [`IndexPart`] to a collection of decisions.
 pub(super) fn reconcile(
-    discovered: Vec<(LayerFileName, u64)>,
+    discovered: Vec<(LayerName, Utf8PathBuf, u64)>,
    index_part: Option<&IndexPart>,
    disk_consistent_lsn: Lsn,
    generation: Generation,
    shard: ShardIndex,
-) -> Vec<(LayerFileName, Result<Decision, DismissedLayer>)> {
+) -> Vec<(LayerName, Result<Decision, DismissedLayer>)> {
    use Decision::*;

-    // name => (local, remote)
-    type Collected = HashMap<LayerFileName, (Option<LayerFileMetadata>, Option<LayerFileMetadata>)>;
+    // name => (local_metadata, remote_metadata)
+    type Collected =
+        HashMap<LayerName, (Option<LocalLayerFileMetadata>, Option<LayerFileMetadata>)>;

    let mut discovered = discovered
        .into_iter()
-        .map(|(name, file_size)| {
+        .map(|(layer_name, local_path, file_size)| {
            (
-                name,
+                layer_name,
                // The generation and shard here will be corrected to match IndexPart in the merge below, unless
                // it is not in IndexPart, in which case using our current generation makes sense
                // because it will be uploaded in this generation.
                (
-                    Some(LayerFileMetadata::new(file_size, generation, shard)),
+                    Some(LocalLayerFileMetadata::new(
+                        local_path, file_size, generation, shard,
+                    )),
                    None,
                ),
            )
@@ -153,7 +178,7 @@ pub(super) fn reconcile(
                Err(DismissedLayer::Future { local })
            } else {
                match (local, remote) {
-                    (Some(local), Some(remote)) if local != remote => {
+                    (Some(local), Some(remote)) if local.metadata != remote => {
                        Ok(UseRemote { local, remote })
                    }
                    (Some(x), Some(_)) => Ok(UseLocal(x)),
@@ -177,12 +202,12 @@ pub(super) fn cleanup(path: &Utf8Path, kind: &str) -> anyhow::Result<()> {
 }

 pub(super) fn cleanup_local_file_for_remote(
-    path: &Utf8Path,
-    local: &LayerFileMetadata,
+    local: &LocalLayerFileMetadata,
    remote: &LayerFileMetadata,
 ) -> anyhow::Result<()> {
-    let local_size = local.file_size();
+    let local_size = local.metadata.file_size();
    let remote_size = remote.file_size();
+    let path = &local.local_path;

    let file_name = path.file_name().expect("must be file path");
    tracing::warn!("removing local file {file_name:?} because it has unexpected length {local_size}; length in remote index is {remote_size}");
@@ -199,7 +224,7 @@ pub(super) fn cleanup_local_file_for_remote(

 pub(super) fn cleanup_future_layer(
    path: &Utf8Path,
-    name: &LayerFileName,
+    name: &LayerName,
    disk_consistent_lsn: Lsn,
 ) -> anyhow::Result<()> {
    // future image layers are allowed to be produced always for not yet flushed to disk
@@ -211,12 +236,14 @@ pub(super) fn cleanup_future_layer(
 }

 pub(super) fn cleanup_local_only_file(
-    path: &Utf8Path,
-    name: &LayerFileName,
-    local: &LayerFileMetadata,
+    name: &LayerName,
+    local: &LocalLayerFileMetadata,
 ) -> anyhow::Result<()> {
    let kind = name.kind();
-    tracing::info!("found local-only {kind} layer {name}, metadata {local:?}");
-    std::fs::remove_file(path)?;
+    tracing::info!(
+        "found local-only {kind} layer {name}, metadata {:?}",
+        local.metadata
+    );
+    std::fs::remove_file(&local.local_path)?;
    Ok(())
 }
--- a/pageserver/src/tenant/timeline/layer_manager.rs
+++ b/pageserver/src/tenant/timeline/layer_manager.rs
@@ -9,6 +9,7 @@ use utils::{

 use crate::{
    config::PageServerConf,
+    context::RequestContext,
    metrics::TimelineMetrics,
    tenant::{
        layer_map::{BatchedUpdates, LayerMap},
@@ -69,6 +70,7 @@ impl LayerManager {
        conf: &'static PageServerConf,
        timeline_id: TimelineId,
        tenant_shard_id: TenantShardId,
+        ctx: &RequestContext,
    ) -> Result<Arc<InMemoryLayer>> {
        ensure!(lsn.is_aligned());

@@ -105,7 +107,7 @@ impl LayerManager {
            );

            let new_layer =
-                InMemoryLayer::create(conf, timeline_id, tenant_shard_id, start_lsn).await?;
+                InMemoryLayer::create(conf, timeline_id, tenant_shard_id, start_lsn, ctx).await?;
            let layer = Arc::new(new_layer);

            self.layer_map.open_layer = Some(layer.clone());
@@ -205,6 +207,24 @@ impl LayerManager {
        updates.flush();
    }

+    /// Called when compaction is completed.
+    pub(crate) fn rewrite_layers(
+        &mut self,
+        rewrite_layers: &[(Layer, ResidentLayer)],
+        drop_layers: &[Layer],
+        _metrics: &TimelineMetrics,
+    ) {
+        let mut updates = self.layer_map.batch_update();
+
+        // TODO: implement rewrites (currently this code path only used for drops)
+        assert!(rewrite_layers.is_empty());
+
+        for l in drop_layers {
+            Self::delete_historic_layer(l, &mut updates, &mut self.layer_fmgr);
+        }
+        updates.flush();
+    }
+
    /// Called when garbage collect has selected the layers to be removed.
    pub(crate) fn finish_gc_timeline(&mut self, gc_layers: &[Layer]) {
        let mut updates = self.layer_map.batch_update();
@@ -276,7 +296,7 @@ impl<T: AsLayerDesc + Clone> LayerFileManager<T> {
        // A layer's descriptor is present in the LayerMap => the LayerFileManager contains a layer for the descriptor.
        self.0
            .get(&desc.key())
-            .with_context(|| format!("get layer from desc: {}", desc.filename()))
+            .with_context(|| format!("get layer from desc: {}", desc.layer_name()))
            .expect("not found")
            .clone()
    }
--- a/pageserver/src/tenant/timeline/walreceiver/connection_manager.rs
+++ b/pageserver/src/tenant/timeline/walreceiver/connection_manager.rs
@@ -1535,7 +1535,7 @@ mod tests {

        let harness = TenantHarness::create("switch_to_same_availability_zone")?;
        let mut state = dummy_state(&harness).await;
-        state.conf.availability_zone = test_az.clone();
+        state.conf.availability_zone.clone_from(&test_az);
        let current_lsn = Lsn(100_000).align();
        let now = Utc::now().naive_utc();

@@ -1568,7 +1568,7 @@ mod tests {
        // We have another safekeeper with the same commit_lsn, and it have the same availability zone as
        // the current pageserver.
        let mut same_az_sk = dummy_broker_sk_timeline(current_lsn.0, "same_az", now);
-        same_az_sk.timeline.availability_zone = test_az.clone();
+        same_az_sk.timeline.availability_zone.clone_from(&test_az);

        state.wal_stream_candidates = HashMap::from([
            (
--- a/pageserver/src/tenant/upload_queue.rs
+++ b/pageserver/src/tenant/upload_queue.rs
@@ -1,8 +1,9 @@
-use super::storage_layer::LayerFileName;
+use super::storage_layer::LayerName;
 use super::storage_layer::ResidentLayer;
 use crate::tenant::metadata::TimelineMetadata;
 use crate::tenant::remote_timeline_client::index::IndexPart;
 use crate::tenant::remote_timeline_client::index::LayerFileMetadata;
+use crate::tenant::remote_timeline_client::index::Lineage;
 use std::collections::{HashMap, VecDeque};
 use std::fmt::Debug;

@@ -45,7 +46,7 @@ pub(crate) struct UploadQueueInitialized {

    /// All layer files stored in the remote storage, taking into account all
    /// in-progress and queued operations
-    pub(crate) latest_files: HashMap<LayerFileName, LayerFileMetadata>,
+    pub(crate) latest_files: HashMap<LayerName, LayerFileMetadata>,

    /// How many file uploads or deletions been scheduled, since the
    /// last (scheduling of) metadata index upload?
@@ -56,6 +57,9 @@ pub(crate) struct UploadQueueInitialized {
    /// DANGER: do not return to outside world, e.g., safekeepers.
    pub(crate) latest_metadata: TimelineMetadata,

+    /// Part of the flattened "next" `index_part.json`.
+    pub(crate) latest_lineage: Lineage,
+
    /// `disk_consistent_lsn` from the last metadata file that was successfully
    /// uploaded. `Lsn(0)` if nothing was uploaded yet.
    /// Unlike `latest_files` or `latest_metadata`, this value is never ahead.
@@ -89,7 +93,7 @@ pub(crate) struct UploadQueueInitialized {
    /// Putting this behind a testing feature to catch problems in tests, but assuming we could have a
    /// bug causing leaks, then it's better to not leave this enabled for production builds.
    #[cfg(feature = "testing")]
-    pub(crate) dangling_files: HashMap<LayerFileName, Generation>,
+    pub(crate) dangling_files: HashMap<LayerName, Generation>,

    /// Set to true when we have inserted the `UploadOp::Shutdown` into the `inprogress_tasks`.
    pub(crate) shutting_down: bool,
@@ -171,6 +175,7 @@ impl UploadQueue {
            latest_files: HashMap::new(),
            latest_files_changes_since_metadata_upload_scheduled: 0,
            latest_metadata: metadata.clone(),
+            latest_lineage: Lineage::default(),
            projected_remote_consistent_lsn: None,
            visible_remote_consistent_lsn: Arc::new(AtomicLsn::new(0)),
            // what follows are boring default initializations
@@ -218,6 +223,7 @@ impl UploadQueue {
            latest_files: files,
            latest_files_changes_since_metadata_upload_scheduled: 0,
            latest_metadata: index_part.metadata.clone(),
+            latest_lineage: index_part.lineage.clone(),
            projected_remote_consistent_lsn: Some(index_part.metadata.disk_consistent_lsn()),
            visible_remote_consistent_lsn: Arc::new(
                index_part.metadata.disk_consistent_lsn().into(),
@@ -281,7 +287,7 @@ pub(crate) struct UploadTask {
 /// for timeline deletion, which skips this queue and goes directly to DeletionQueue.
 #[derive(Debug)]
 pub(crate) struct Delete {
-    pub(crate) layers: Vec<(LayerFileName, LayerFileMetadata)>,
+    pub(crate) layers: Vec<(LayerName, LayerFileMetadata)>,
 }

 #[derive(Debug)]
@@ -290,7 +296,7 @@ pub(crate) enum UploadOp {
    UploadLayer(ResidentLayer, LayerFileMetadata),

    /// Upload the metadata file
-    UploadMetadata(IndexPart, Lsn),
+    UploadMetadata(Box<IndexPart>, Lsn),

    /// Delete layer files
    Delete(Delete),
--- a/pageserver/src/tenant/vectored_blob_io.rs
+++ b/pageserver/src/tenant/vectored_blob_io.rs
@@ -23,6 +23,7 @@ use pageserver_api::key::Key;
 use utils::lsn::Lsn;
 use utils::vec_map::VecMap;

+use crate::context::RequestContext;
 use crate::virtual_file::VirtualFile;

 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
@@ -285,6 +286,7 @@ impl<'a> VectoredBlobReader<'a> {
        &self,
        read: &VectoredRead,
        buf: BytesMut,
+        ctx: &RequestContext,
    ) -> Result<VectoredBlobsBuf, std::io::Error> {
        assert!(read.size() > 0);
        assert!(
@@ -295,7 +297,7 @@ impl<'a> VectoredBlobReader<'a> {
        );
        let buf = self
            .file
-            .read_exact_at_n(buf, read.start, read.size())
+            .read_exact_at_n(buf, read.start, read.size(), ctx)
            .await?;

        let blobs_at = read.blobs_at.as_slice();
--- a/Show More
+++ b/Show More