diff --git a/.github/actions/install-node-dependencies/action.yml b/.github/actions/install-node-dependencies/action.yml
index 7695d2bec9b..95ef7e96cc9 100644
--- a/.github/actions/install-node-dependencies/action.yml
+++ b/.github/actions/install-node-dependencies/action.yml
@@ -10,6 +10,10 @@ inputs:
     description: Node.js version override; defaults to the version declared in package.json.
     required: false
     default: ''
+  cache-dependency-path:
+    description: Lockfiles for the pnpm download store; include mobile/pnpm-lock.yaml only when the job installs mobile dependencies.
+    required: false
+    default: pnpm-lock.yaml
   persist-native-cache:
     description: Save restored native modules at job end. Set false when a later step overwrites the same path with a different ABI.
     required: false
@@ -39,9 +43,7 @@ runs:
       with:
         install: false
 
-    # Why both lockfiles: setup-node keys the pnpm store on the root lockfile alone, so
-    # jobs that also install mobile restored a store with none of the React Native tree
-    # in it and re-downloaded the lot on every run.
+    # Desktop-only jobs should not miss their download cache when mobile dependencies change.
     - name: Setup Node.js
       id: default-node
       if: inputs.node-version == ''
@@ -49,9 +51,7 @@ runs:
       with:
         node-version-file: package.json
         cache: pnpm
-        cache-dependency-path: |
-          pnpm-lock.yaml
-          mobile/pnpm-lock.yaml
+        cache-dependency-path: ${{ inputs.cache-dependency-path }}
 
     - name: Setup requested Node.js
       id: requested-node
@@ -60,9 +60,7 @@ runs:
       with:
         node-version: ${{ inputs.node-version }}
         cache: pnpm
-        cache-dependency-path: |
-          pnpm-lock.yaml
-          mobile/pnpm-lock.yaml
+        cache-dependency-path: ${{ inputs.cache-dependency-path }}
 
     - name: Validate native runtime
       shell: bash
diff --git a/.github/workflows/adhoc-mac-build.yml b/.github/workflows/adhoc-mac-build.yml
index 3e17eee9b68..ac49acdbb83 100644
--- a/.github/workflows/adhoc-mac-build.yml
+++ b/.github/workflows/adhoc-mac-build.yml
@@ -160,16 +160,14 @@ jobs:
 
       - name: Checkout the requested ref
         uses: actions/checkout@v6
-        env:
-          # Full-history checkout must also preserve case-twin branch and tag names.
-          GIT_DEFAULT_REF_FORMAT: reftable
         with:
           # Why an input at all rather than just github.ref: the whole point is to
           # build code that has not landed, and the workflow definition itself
           # always comes from the dispatch ref — naming the branch here instead
           # applies main's current copy of this file to an arbitrary branch.
           ref: ${{ steps.vetted.outputs.sha }}
-          fetch-depth: 0
+          # Version helpers only read HEAD; published versions come from the release API.
+          fetch-depth: 1
           # This job only reads stablyai/orca and never pushes; every write goes
           # to the adhoc repo through a minted App token passed by env. Not
           # persisting the checkout credential shrinks the blast radius if a build
diff --git a/.github/workflows/daily-mac-build.yml b/.github/workflows/daily-mac-build.yml
index 45130e932d8..e70fc928295 100644
--- a/.github/workflows/daily-mac-build.yml
+++ b/.github/workflows/daily-mac-build.yml
@@ -90,7 +90,8 @@ jobs:
         uses: actions/checkout@v6
         with:
           ref: main
-          fetch-depth: 0
+          # Version helpers only read HEAD; published versions come from the release API.
+          fetch-depth: 1
           # Why: this job only reads stablyai/orca and never pushes; every write
           # goes to the daily repo through a minted App token passed by env.
           # Not persisting the checkout credential shrinks the blast radius if a
diff --git a/.github/workflows/hourly-mac-build.yml b/.github/workflows/hourly-mac-build.yml
index c300b2543b8..e55adc54995 100644
--- a/.github/workflows/hourly-mac-build.yml
+++ b/.github/workflows/hourly-mac-build.yml
@@ -137,7 +137,8 @@ jobs:
         uses: actions/checkout@v6
         with:
           ref: ${{ needs.preflight.outputs.head_sha }}
-          fetch-depth: 0
+          # Version helpers only read HEAD; published versions come from the release API.
+          fetch-depth: 1
           # Why: this job only reads stablyai/orca and never pushes; every write
           # goes to the hourly repo through a minted App token passed by env.
           # Not persisting the checkout credential shrinks the blast radius if a
diff --git a/.github/workflows/mobile.yml b/.github/workflows/mobile.yml
index 6dbfc02aa3c..9afc865f87e 100644
--- a/.github/workflows/mobile.yml
+++ b/.github/workflows/mobile.yml
@@ -41,6 +41,10 @@ jobs:
         uses: actions/checkout@v6
 
       - uses: ./.github/actions/install-node-dependencies
+        with:
+          cache-dependency-path: |
+            pnpm-lock.yaml
+            mobile/pnpm-lock.yaml
 
       # bundler-cache installs mobile/Gemfile.lock, so this job is also what
       # proves the pinned fastlane the release workflow depends on still
diff --git a/.github/workflows/pr.yml b/.github/workflows/pr.yml
index a9e45ef116e..45a3d12c2d8 100644
--- a/.github/workflows/pr.yml
+++ b/.github/workflows/pr.yml
@@ -126,6 +126,9 @@ jobs:
       - uses: ./.github/actions/install-node-dependencies
         with:
           native-runtime: node
+          cache-dependency-path: |
+            pnpm-lock.yaml
+            mobile/pnpm-lock.yaml
 
       - name: Lint
         run: pnpm exec oxlint --format github
diff --git a/config/scripts/ci-dependency-download-cache.test.mjs b/config/scripts/ci-dependency-download-cache.test.mjs
new file mode 100644
index 00000000000..9cce5bb0f6f
--- /dev/null
+++ b/config/scripts/ci-dependency-download-cache.test.mjs
@@ -0,0 +1,30 @@
+import { readFileSync } from 'node:fs'
+import { describe, expect, it } from 'vitest'
+import { parse } from 'yaml'
+
+const read = (path) => parse(readFileSync(path, 'utf8'))
+const workflow = (name) => read(`.github/workflows/${name}.yml`)
+const action = read('.github/actions/install-node-dependencies/action.yml')
+
+describe('CI dependency download caches', () => {
+  it('scopes desktop stores to the root lockfile and lets mixed installs opt in', () => {
+    expect(action.inputs['cache-dependency-path'].default).toBe('pnpm-lock.yaml')
+    for (const step of action.runs.steps.filter((step) => step.uses === 'actions/setup-node@v6')) {
+      expect(step.with.cache).toBe('pnpm')
+      expect(step.with['cache-dependency-path']).toBe('${{ inputs.cache-dependency-path }}')
+    }
+    const install = action.runs.steps.find((step) => step.name === 'Install dependencies')
+    expect(install.if).toBeUndefined()
+    expect(install.run).toContain('pnpm install --frozen-lockfile --ignore-scripts')
+    expect(install.run).toContain(
+      'diff --exit-code -- package.json pnpm-lock.yaml pnpm-workspace.yaml'
+    )
+    const mobile = workflow('mobile').jobs.verify.steps.find((step) =>
+      step.uses?.includes('install-node-dependencies')
+    )
+    expect(mobile.with['cache-dependency-path'].trim().split('\n')).toEqual([
+      'pnpm-lock.yaml',
+      'mobile/pnpm-lock.yaml'
+    ])
+  })
+})
diff --git a/config/scripts/workflow-ref-mirror-case-safety.test.mjs b/config/scripts/workflow-ref-mirror-case-safety.test.mjs
index 31366f5e489..497a58653a0 100644
--- a/config/scripts/workflow-ref-mirror-case-safety.test.mjs
+++ b/config/scripts/workflow-ref-mirror-case-safety.test.mjs
@@ -1,7 +1,10 @@
-import { readFileSync } from 'node:fs'
+import { mkdtempSync, readFileSync, rmSync, writeFileSync } from 'node:fs'
+import { tmpdir } from 'node:os'
 import { join, resolve } from 'node:path'
+import { pathToFileURL } from 'node:url'
 import { describe, expect, it } from 'vitest'
 import { parse } from 'yaml'
+import { runProcessSync } from '../../src/shared/child-process/run-process'
 
 const projectDir = resolve(import.meta.dirname, '../..')
 
@@ -15,13 +18,74 @@ const REF_MIRRORS = [
 ]
 
 describe('ref-mirroring vet steps', () => {
-  it('keeps the full-history adhoc checkout on the same case-safe backend', () => {
+  it.each(['daily', 'hourly', 'adhoc'])('%s builds only need the current commit', (channel) => {
+    const job = readWorkflow(`.github/workflows/${channel}-mac-build.yml`).jobs[
+      `build-${channel}-mac`
+    ]
+    const checkout = job.steps.find((step) => step.uses === 'actions/checkout@v6')
+    expect(checkout.with['fetch-depth']).toBe(1)
+    expect(job.steps.some((step) => step.run?.includes('gh release list'))).toBe(true)
+    expect(
+      job.steps.some((step) => step.run?.includes('ORCA_PUBLISHED_VERSIONS="$published"'))
+    ).toBe(true)
+  })
+
+  it('retains release-cut history for version reservation and retry ancestry', () => {
+    const checkout = readWorkflow('.github/workflows/release-cut.yml').jobs.cut.steps.find(
+      (step) => step.uses === 'actions/checkout@v6'
+    )
+    expect(checkout.with['fetch-depth']).toBe(0)
+  })
+
+  it('resolves identical dev identities in full and depth-one checkouts without local tags', () => {
+    const directory = mkdtempSync(join(tmpdir(), 'orca-checkout-identity-'))
+    const source = join(directory, 'source')
+    const shallow = join(directory, 'shallow')
+    const run = (program, args, cwd) => {
+      const result = runProcessSync({ program, args, cwd })
+      expect(result.code, result.stderr).toBe(0)
+      return result.stdout.trim()
+    }
+    const git = (args, cwd = directory) => run('git', args, cwd)
+    try {
+      git(['init', source])
+      git(['config', 'user.name', 'CI test'], source)
+      git(['config', 'user.email', 'ci@example.invalid'], source)
+      writeFileSync(join(source, 'package.json'), JSON.stringify({ version: '1.4.165-rc.0' }))
+      git(['add', 'package.json'], source)
+      git(['-c', 'commit.gpgsign=false', 'commit', '-m', 'initial'], source)
+      git(['tag', 'v1.4.167'], source)
+      git(['-c', 'commit.gpgsign=false', 'commit', '--allow-empty', '-m', 'head'], source)
+      git(['clone', '--depth=1', '--no-tags', pathToFileURL(source).href, shallow])
+      expect(git(['rev-list', '--count', 'HEAD'], shallow)).toBe('1')
+      expect(git(['tag', '--list'], shallow)).toBe('')
+      const script = `
+        const result = [];
+        for (const [channel, exported] of [['daily', 'Daily'], ['hourly', 'Hourly'], ['adhoc', 'Adhoc']]) {
+          const module = await import(${JSON.stringify(pathToFileURL(join(projectDir, 'config/scripts/')).href)} + channel + '-build-version.mjs');
+          const date = new Date('2026-09-12T00:00:00Z');
+          result.push(channel === 'adhoc'
+            ? module.getAdhocBuildIdentity(date, 'branch', ['v1.4.167'])
+            : module['get' + exported + 'BuildIdentity'](date, { publishedVersions: ['v1.4.167'], releaseNames: [] }));
+        }
+        process.stdout.write(JSON.stringify(result));
+      `
+      const identities = (cwd) => run(process.execPath, ['--input-type=module', '-e', script], cwd)
+      expect(identities(shallow)).toBe(identities(source))
+      expect(
+        JSON.parse(identities(shallow)).every((identity) => identity.version.startsWith('1.4.168-'))
+      ).toBe(true)
+    } finally {
+      rmSync(directory, { recursive: true, force: true })
+    }
+  })
+
+  it('checks out only the vetted commit without remirroring refs', () => {
     const steps = readWorkflow('.github/workflows/adhoc-mac-build.yml').jobs['build-adhoc-mac']
       .steps
     const checkout = steps.find((step) => step.name === 'Checkout the requested ref')
-    expect(checkout.env.GIT_DEFAULT_REF_FORMAT).toBe('reftable')
     expect(checkout.with.ref).toBe('${{ steps.vetted.outputs.sha }}')
-    expect(checkout.with['fetch-depth']).toBe(0)
+    expect(checkout.with['fetch-depth']).toBe(1)
     expect(checkout.with['persist-credentials']).toBe(false)
   })
 
diff --git a/config/scripts/workflow-ref-reachability.test.mjs b/config/scripts/workflow-ref-reachability.test.mjs
index d71c3094c56..84a0b167986 100644
--- a/config/scripts/workflow-ref-reachability.test.mjs
+++ b/config/scripts/workflow-ref-reachability.test.mjs
@@ -95,7 +95,7 @@ describe('release ref trust with case-twin names', () => {
     expect(result.stdout).toContain('Refusing to build PR ref')
   })
 
-  it('preserves both case variants in the subsequent full-history checkout', async () => {
+  it('checks out the vetted SHA shallowly without mirroring case-twin refs again', async () => {
     const checkout = join(directory, 'checkout')
     const env = { ...identity, ...macCheckout.env }
     await git(['init', checkout], env)
@@ -105,21 +105,15 @@ describe('release ref trust with case-twin names', () => {
         checkout,
         'fetch',
         '--no-tags',
+        `--depth=${macCheckout.with['fetch-depth']}`,
         repository,
-        '+refs/heads/*:refs/remotes/origin/*',
-        '+refs/tags/*:refs/tags/*'
+        upper
       ],
       env
     )
     await git(['-C', checkout, 'checkout', '--detach', upper], env)
-    for (const [ref, sha] of [
-      ['refs/remotes/origin/Fix', upper],
-      ['refs/remotes/origin/fix', lower],
-      ['refs/tags/Release', upper],
-      ['refs/tags/release', lower]
-    ]) {
-      expect(await git(['-C', checkout, 'rev-parse', `${ref}^{commit}`], env)).toBe(sha)
-    }
     expect(await git(['-C', checkout, 'rev-parse', 'HEAD'], env)).toBe(upper)
+    expect(await git(['-C', checkout, 'rev-list', '--count', 'HEAD'], env)).toBe('1')
+    expect(await git(['-C', checkout, 'for-each-ref', '--format=%(refname)'], env)).toBe('')
   })
 })