diff --git a/.github/workflows/ssh-relay-runtime-artifacts.yml b/.github/workflows/ssh-relay-runtime-artifacts.yml
index d90f0de0a07..9ba6d320dd0 100644
--- a/.github/workflows/ssh-relay-runtime-artifacts.yml
+++ b/.github/workflows/ssh-relay-runtime-artifacts.yml
@@ -290,6 +290,7 @@ jobs:
             src/main/ssh/ssh-relay-runtime-posix-file-destination.test.ts \
             src/main/ssh/ssh-relay-runtime-windows-file-destination.test.ts \
             src/main/ssh/ssh-relay-runtime-windows-staging-control.test.ts \
+            src/main/ssh/ssh-relay-runtime-windows-tree-transfer.test.ts \
             src/main/ssh/ssh-relay-runtime-posix-tree-transfer.test.ts \
             src/main/ssh/ssh-relay-runtime-system-ssh-file-channel.test.ts \
             src/main/ssh/ssh-relay-runtime-sftp-file-destination.test.ts \
@@ -1031,6 +1032,7 @@ jobs:
             src/main/ssh/ssh-relay-runtime-posix-file-destination.test.ts `
             src/main/ssh/ssh-relay-runtime-windows-file-destination.test.ts `
             src/main/ssh/ssh-relay-runtime-windows-staging-control.test.ts `
+            src/main/ssh/ssh-relay-runtime-windows-tree-transfer.test.ts `
             src/main/ssh/ssh-relay-runtime-posix-tree-transfer.test.ts `
             src/main/ssh/ssh-relay-runtime-system-ssh-file-channel.test.ts `
             src/main/ssh/ssh-relay-runtime-sftp-file-destination.test.ts `
diff --git a/config/scripts/ssh-relay-runtime-workflow.test.mjs b/config/scripts/ssh-relay-runtime-workflow.test.mjs
index a5ee8115b4e..5601f06bb9f 100644
--- a/config/scripts/ssh-relay-runtime-workflow.test.mjs
+++ b/config/scripts/ssh-relay-runtime-workflow.test.mjs
@@ -204,6 +204,7 @@ describe('SSH relay runtime artifact workflow', () => {
       'ssh-relay-runtime-posix-file-destination.test.ts',
       'ssh-relay-runtime-windows-file-destination.test.ts',
       'ssh-relay-runtime-windows-staging-control.test.ts',
+      'ssh-relay-runtime-windows-tree-transfer.test.ts',
       'ssh-relay-runtime-posix-tree-transfer.test.ts',
       'ssh-relay-runtime-system-ssh-file-channel.test.ts',
       'ssh-relay-runtime-sftp-file-destination.test.ts',
diff --git a/docs/reference/plans/2026-07-14-ssh-relay-github-release-implementation-checklist-summary.md b/docs/reference/plans/2026-07-14-ssh-relay-github-release-implementation-checklist-summary.md
index c512e0c4d29..a98bab60975 100644
--- a/docs/reference/plans/2026-07-14-ssh-relay-github-release-implementation-checklist-summary.md
+++ b/docs/reference/plans/2026-07-14-ssh-relay-github-release-implementation-checklist-summary.md
@@ -10,12 +10,17 @@ A checked box means the work has evidence in the detailed ledger. Design approva
 complete a box.
 
 Active checkpoint: **Milestone 6 / Work Package 5 bounded runtime transfer — disconnected Windows
-system-SSH tree-composition contract audit, 2026-07-15, Codex implementation owner.**
-The next slice is limited to composing the proven staging control, per-file receiver, source stream,
-and existing system-SSH channel adapter into one exclusive Windows staging tree with parent-first
-directories, bounded concurrency/progress, and joined owned-root cleanup. Live OpenSSH, product
-callers, legacy upload/fallback/default behavior, tuple enablement, publication, and SignPath remain
-out of scope.
+system-SSH tree-composition native CI proof, 2026-07-15, Codex implementation owner.**
+The local package is green; push its isolated commit and require exact-head all-six native artifact
+and adjacent workflow evidence before auditing any live/full-size Windows OpenSSH package. Live
+OpenSSH, product callers, legacy upload/fallback/default behavior, tuple enablement, publication,
+and SignPath remain out of scope.
+`E-M6-WINDOWS-SYSTEM-SSH-TREE-LOCAL-RED-001` proves the native workflow oracle passes 9/9 and the
+purpose suite fails solely because the audited production tree-composition module is absent.
+`E-M6-WINDOWS-SYSTEM-SSH-TREE-LOCAL-001` records 8/8 purpose and 9/9 workflow-oracle cases, 258
+focused passes with three declared skips, 694 broad relay passes with nine declared skips, 282/282
+release contracts, typecheck, full lint, formatting, max-lines, diff, protected-resolver, and
+no-product-consumer gates. Exact-head native CI remains required.
 `E-M6-WINDOWS-SYSTEM-SSH-CONTROL-LOCAL-RED-001` proves the native workflow oracle passes 9/9 and
 the purpose suite fails solely because the audited production staging-control module is absent.
 `E-M6-WINDOWS-SYSTEM-SSH-CONTROL-LOCAL-001` records 16/17 purpose cases locally with the real
diff --git a/docs/reference/plans/2026-07-14-ssh-relay-github-release-implementation-checklist.md b/docs/reference/plans/2026-07-14-ssh-relay-github-release-implementation-checklist.md
index 04a3c3262a8..18a69f57aa7 100644
--- a/docs/reference/plans/2026-07-14-ssh-relay-github-release-implementation-checklist.md
+++ b/docs/reference/plans/2026-07-14-ssh-relay-github-release-implementation-checklist.md
@@ -8,8 +8,8 @@ work; keep exact commands, runner identities, hashes, metrics, and residual gaps
 
 Date created: 2026-07-14<br>
 Last updated: 2026-07-15<br>
-Current phase: Milestone 6 / Work Package 5 bounded runtime transfer — **In progress — 2026-07-15, Codex implementation owner: disconnected Windows system-SSH tree-composition contract audit**. Keep every capability disconnected from every production/default SSH path. Real Apple/SignPath rehearsals remain an explicit late gate and are not on this package's critical path.<br>
-Session checkpoint: **WINDOWS STAGING CONTROL NATIVE PROOF CLOSED / TREE COMPOSITION AUDIT ACTIVE — 2026-07-15, Codex implementation owner** — `E-M6-WINDOWS-SYSTEM-SSH-CONTROL-CI-001` proves the real PowerShell staging-control contract on native Windows x64/arm64 and all adjacent exact-head gates, with only the declared hosted Windows arm64 floor gap. Audit the next disconnected tree owner before writing RED tests. Do not connect a product caller, change legacy upload/fallback/default behavior, enable a tuple, publish an artifact, or perform SignPath work. Merging to `main` remains prohibited, SignPath is deferred, and legacy remains the production default.<br>
+Current phase: Milestone 6 / Work Package 5 bounded runtime transfer — **In progress — 2026-07-15, Codex implementation owner: disconnected Windows system-SSH tree-composition native CI proof**. Keep every capability disconnected from every production/default SSH path. Real Apple/SignPath rehearsals remain an explicit late gate and are not on this package's critical path.<br>
+Session checkpoint: **WINDOWS TREE COMPOSITION LOCAL GREEN / EXACT-HEAD NATIVE CI NEXT — 2026-07-15, Codex implementation owner** — `E-M6-WINDOWS-SYSTEM-SSH-TREE-LOCAL-001` proves the disconnected composer and every audited local lifecycle gate. Commit and push the isolated package, then require all-six native artifact and adjacent exact-head workflows before auditing live/full-size Windows OpenSSH. Do not connect a product caller, change legacy upload/fallback/default behavior, enable a tuple, publish an artifact, or perform SignPath work. Merging to `main` remains prohibited, SignPath is deferred, and legacy remains the production default.<br>
 Primary design: [SSH relay GitHub Release plan](./2026-07-14-ssh-relay-github-release-plan.html)<br>
 Motivating issues: [#8450](https://github.com/stablyai/orca/issues/8450), [#1693](https://github.com/stablyai/orca/issues/1693)
 
@@ -18411,6 +18411,79 @@ src/main/ssh/ssh-remote-node-resolution.test.ts` is empty. A non-test reference
   publication/default behavior, or SignPath. Legacy remains the sole production/default path and
   every tuple stays disabled.
 
+### E-M6-WINDOWS-SYSTEM-SSH-TREE-LOCAL-RED-001 — audited tree composer is absent
+
+- Date/owner/base: 2026-07-15, Codex implementation owner; uncommitted test/workflow package atop
+  `c39e20cc6ccdfc66dbac25bd17d86fd4e53fdacd`.
+- Format command:
+  `pnpm exec oxfmt --check .github/workflows/ssh-relay-runtime-artifacts.yml config/scripts/ssh-relay-runtime-workflow.test.mjs src/main/ssh/ssh-relay-runtime-windows-tree-transfer.test.ts docs/reference/plans/2026-07-14-ssh-relay-github-release-implementation-checklist.md docs/reference/plans/2026-07-14-ssh-relay-github-release-implementation-checklist-summary.md`
+  passes all five files in 9.616 seconds.
+- RED command:
+  `pnpm exec vitest run --config config/vitest.config.ts --maxWorkers=1 src/main/ssh/ssh-relay-runtime-windows-tree-transfer.test.ts config/scripts/ssh-relay-runtime-workflow.test.mjs`.
+  The workflow oracle passes 9/9 in 215 ms. The purpose suite collects zero tests and fails at its
+  production import only with `Cannot find module '/src/main/ssh/ssh-relay-runtime-windows-tree-transfer'`;
+  there is no assertion, fixture, workflow-oracle, or adjacent failure.
+- Disposition: the RED state matches `E-M6-WINDOWS-SYSTEM-SSH-TREE-AUDIT-001`. Implement only the
+  disconnected composer and expand the green suite to every audited lifecycle case. No product
+  consumer, live Windows OpenSSH claim, default/fallback change, tuple enablement, publication, or
+  SignPath work is authorized by this evidence.
+
+### E-M6-WINDOWS-SYSTEM-SSH-TREE-LOCAL-001 — disconnected tree composer is locally green
+
+- Date/owner/base/runner: 2026-07-15, Codex implementation owner; uncommitted implementation,
+  purpose-test, native-workflow, and checklist package atop exact base
+  `c39e20cc6ccdfc66dbac25bd17d86fd4e53fdacd` on Apple arm64, macOS 26.2 build 25C56, Node
+  26.5.0, pnpm 10.24.0. Local Node is newer than the repository's Node 24 contract, so exact-head
+  all-six native proof remains mandatory.
+- Implementation: add one disconnected Windows tree owner over the proven staging-control,
+  per-file receiver, source-stream scheduler, and authenticated system-SSH channel adapter. It
+  validates a Windows scanned tree, rooted drive/UNC staging path, system transport, exact signal,
+  and one-to-four concurrency before I/O; defaults to one file; creates one exclusive root and every
+  declared directory parent-first; streams exact descendant paths/sizes; and returns only frozen
+  aggregate progress. Root ownership begins only after successful exclusive creation. Later failure
+  or cancellation joins all source workers before a separate five-second owned-root cleanup, and
+  joins primary plus cleanup errors.
+- Purpose command: `/usr/bin/time -l pnpm exec vitest run --config config/vitest.config.ts
+--maxWorkers=1 src/main/ssh/ssh-relay-runtime-windows-tree-transfer.test.ts
+config/scripts/ssh-relay-runtime-workflow.test.mjs`. Result: two files and 17/17 cases pass: 8/8
+  composer lifecycle cases plus the 9/9 workflow oracle; 2.17 seconds real, 139,853,824-byte maximum
+  RSS, 98,866,936-byte peak footprint, zero swaps and block I/O. Proof covers hostile/pre-aborted
+  input before I/O, exact root/parent-first directories/files/bytes/counts/path-free progress,
+  default-one and maximum-four destinations, collision preservation, directory/file failure,
+  retained-write cancellation before cleanup, joined cleanup failure, five-second cleanup timeout,
+  and no later progress.
+- Focused command: `/usr/bin/time -l pnpm exec vitest run --config config/vitest.config.ts
+--maxWorkers=1` with the Windows tree/control/file, POSIX tree/control/file, system-channel,
+  source-tree/scan/stream, system-fallback, connection, and workflow-oracle suites. Result: 13 files,
+  258 passed and three declared platform skips out of 261; 20.40 seconds real, 186,826,752-byte
+  maximum RSS, 97,179,360-byte peak footprint, zero swaps and block I/O.
+- Broad relay command: `/usr/bin/time -l pnpm exec vitest run --config config/vitest.config.ts
+--maxWorkers=1 src/main/ssh/ssh-relay-*.test.ts`. Result: 53 files passed, five files skipped; 694
+  passed and nine declared skips out of 703; 46.75 seconds real, 324,173,824-byte maximum RSS,
+  97,146,592-byte peak footprint, zero swaps and block I/O.
+- Release-contract command: `/usr/bin/time -l pnpm exec vitest run --config
+config/vitest.config.ts --maxWorkers=1 config/scripts/ssh-relay-runtime-*.test.mjs`. Result: 50
+  files and 282/282 cases pass; 19.62 seconds real, 195,706,880-byte maximum RSS, 97,900,328-byte
+  peak footprint, zero swaps and block I/O.
+- Static evidence: final-code `pnpm typecheck` passes. `/usr/bin/time -l pnpm lint` passes in 23.95
+  seconds real with 2,073,870,336-byte maximum RSS and 97,949,456-byte peak footprint; its 26
+  warnings pre-exist outside this diff. Full lint proves switch exhaustiveness, 41 reliability gates,
+  the 355-entry max-lines ratchet with no new bypass, bundled guides, and localization checks.
+  Targeted `oxlint` and six-file `oxfmt --check` pass.
+- Isolation evidence: `git diff --check` passes; `git diff --exit-code HEAD --
+src/main/ssh/ssh-remote-node-resolution.ts src/main/ssh/ssh-remote-node-resolution.test.ts` is
+  empty. An asserted non-test reference search finds the new export only in its owning production
+  module. The intended diff is limited to the disconnected composer/purpose test, its one entry in
+  each native workflow command family and oracle, and both checklist documents. No legacy uploader,
+  Electron/startup/product importer, settings, Beta mode, fallback, tuple, publication, default-path,
+  or signing behavior changes.
+- Residual boundary: this is adapter-backed composition, not live Windows OpenSSH, a full-size
+  runtime transfer/measurement, long-path or endpoint-protection proof, primitive classification/
+  cache, remote bundled-Node verification/install/publish/launch, product/Beta/fallback/default
+  behavior, tuple enablement, publication, Apple signing, or SignPath. Exact-head all-six native and
+  adjacent workflow proof remains required before this package closes. Legacy remains the sole
+  production/default path and every tuple stays disabled.
+
 ## Accepted Gaps
 
 No product gap is accepted merely because it appears in this list. Each entry requires explicit
diff --git a/src/main/ssh/ssh-relay-runtime-windows-tree-transfer.test.ts b/src/main/ssh/ssh-relay-runtime-windows-tree-transfer.test.ts
new file mode 100644
index 00000000000..802ff0bbbd4
--- /dev/null
+++ b/src/main/ssh/ssh-relay-runtime-windows-tree-transfer.test.ts
@@ -0,0 +1,390 @@
+import { mkdir, mkdtemp, readFile, rm } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+
+import { publishSshRelayArtifactCacheEntry } from './ssh-relay-artifact-cache-entry'
+import { createSshRelayArtifactCacheEntryFixture } from './ssh-relay-artifact-cache-entry-fixture'
+import {
+  acquireSshRelayArtifactCacheInUseLease,
+  type SshRelayArtifactCacheInUseLease
+} from './ssh-relay-artifact-cache-in-use-lease'
+import { scanSshRelayRuntimeSourceTree } from './ssh-relay-runtime-source-scan'
+import { createSshRelayRuntimeSourceTree } from './ssh-relay-runtime-source-tree'
+import type { SshRelayRuntimeSystemSshConnection } from './ssh-relay-runtime-system-ssh-file-channel'
+import {
+  transferSshRelayRuntimeTreeViaWindowsSystemSsh,
+  SSH_RELAY_RUNTIME_WINDOWS_TREE_TRANSFER_LIMITS
+} from './ssh-relay-runtime-windows-tree-transfer'
+
+const stagingControl = vi.hoisted(() => vi.fn())
+const openFileDestination = vi.hoisted(() => vi.fn())
+
+vi.mock('./ssh-relay-runtime-windows-staging-control', () => ({
+  runSshRelayRuntimeWindowsStagingControl: stagingControl
+}))
+vi.mock('./ssh-relay-runtime-windows-file-destination', () => ({
+  openSshRelayRuntimeWindowsFileDestination: openFileDestination
+}))
+
+const cleanupRoots = new Set<string>()
+const cleanupLeases = new Set<SshRelayArtifactCacheInUseLease>()
+
+async function treeFixture(os: 'win32' | 'linux' = 'win32') {
+  const root = await mkdtemp(join(tmpdir(), 'orca-relay-windows-tree-'))
+  cleanupRoots.add(root)
+  const inputRoot = join(root, 'input')
+  await mkdir(inputRoot)
+  const fixture = await createSshRelayArtifactCacheEntryFixture({ root: inputRoot, os })
+  const cacheRoot = join(root, 'cache')
+  const entry = await publishSshRelayArtifactCacheEntry({
+    cacheRoot,
+    artifact: fixture.artifact,
+    archivePath: fixture.archivePath
+  })
+  const lease = await acquireSshRelayArtifactCacheInUseLease({ cacheRoot, entry })
+  cleanupLeases.add(lease)
+  const source = createSshRelayRuntimeSourceTree({
+    kind: 'ready',
+    source: 'cache',
+    artifact: fixture.artifact,
+    entry,
+    lease
+  })
+  return scanSshRelayRuntimeSourceTree(source, new AbortController().signal)
+}
+
+function connection(system = true): SshRelayRuntimeSystemSshConnection {
+  return { usesSystemSshTransport: () => system, exec: vi.fn() }
+}
+
+function retainDestinationWrites() {
+  let active = 0
+  let peak = 0
+  let holding = true
+  const pending = new Set<() => void>()
+  openFileDestination.mockImplementation(async ({ signal }: { signal: AbortSignal }) => {
+    active += 1
+    peak = Math.max(peak, active)
+    let owned = true
+    const settle = (): void => {
+      if (owned) {
+        owned = false
+        active -= 1
+      }
+    }
+    return {
+      write: vi.fn(() => {
+        if (!holding) {
+          return Promise.resolve()
+        }
+        return new Promise<void>((resolve, reject) => {
+          const release = (): void => {
+            signal.removeEventListener('abort', onAbort)
+            pending.delete(release)
+            resolve()
+          }
+          const onAbort = (): void => {
+            pending.delete(release)
+            reject(signal.reason)
+          }
+          pending.add(release)
+          signal.addEventListener('abort', onAbort, { once: true })
+        })
+      }),
+      close: vi.fn(async () => settle()),
+      abort: vi.fn(async () => settle())
+    }
+  })
+  return {
+    peak: () => peak,
+    release: () => {
+      holding = false
+      for (const release of pending) {
+        release()
+      }
+    }
+  }
+}
+
+beforeEach(() => {
+  stagingControl.mockReset().mockResolvedValue(undefined)
+  openFileDestination.mockReset().mockImplementation(async () => ({
+    write: vi.fn(async () => {}),
+    close: vi.fn(async () => {}),
+    abort: vi.fn(async () => {})
+  }))
+})
+
+afterEach(async () => {
+  vi.useRealTimers()
+  await Promise.all([...cleanupLeases].map((lease) => lease.release().catch(() => {})))
+  cleanupLeases.clear()
+  await Promise.all([...cleanupRoots].map((root) => rm(root, { recursive: true, force: true })))
+  cleanupRoots.clear()
+})
+
+describe('SSH relay runtime Windows system-SSH tree transfer', () => {
+  it('rejects POSIX trees, unsafe roots, transport, concurrency, and pre-abort before I/O', async () => {
+    const windows = await treeFixture()
+    const linux = await treeFixture('linux')
+    const signal = new AbortController().signal
+    for (const options of [
+      { tree: linux, connection: connection(), remoteStagingRoot: 'C:/stage', signal },
+      { tree: windows, connection: connection(), remoteStagingRoot: '../stage', signal },
+      { tree: windows, connection: connection(), remoteStagingRoot: 'C:/CON/stage', signal },
+      { tree: windows, connection: connection(), remoteStagingRoot: '//server/share', signal },
+      { tree: windows, connection: connection(false), remoteStagingRoot: 'C:/stage', signal },
+      {
+        tree: windows,
+        connection: connection(),
+        remoteStagingRoot: 'C:/stage',
+        maximumConcurrency: 5,
+        signal
+      }
+    ]) {
+      await expect(transferSshRelayRuntimeTreeViaWindowsSystemSsh(options)).rejects.toThrow()
+    }
+    const controller = new AbortController()
+    const reason = new Error('pre-aborted')
+    controller.abort(reason)
+    await expect(
+      transferSshRelayRuntimeTreeViaWindowsSystemSsh({
+        tree: windows,
+        connection: connection(),
+        remoteStagingRoot: 'C:/stage',
+        signal: controller.signal
+      })
+    ).rejects.toBe(reason)
+    expect(stagingControl).not.toHaveBeenCalled()
+    expect(openFileDestination).not.toHaveBeenCalled()
+  })
+
+  it('creates parent-first directories and streams every exact file before returning progress', async () => {
+    const tree = await treeFixture()
+    const remoteRoot = 'C:/Users/测试/.orca/stage'
+    const written = new Map<string, Buffer>()
+    const events: string[] = []
+    stagingControl.mockImplementation(async ({ operation, remotePath }) => {
+      events.push(operation === 'create-directory' ? `directory:${remotePath}` : operation)
+    })
+    openFileDestination.mockImplementation(
+      async ({ remotePath, expectedSize, signal, openChannel }) => {
+        events.push(`file:${remotePath}`)
+        expect(expectedSize).toBe(tree.files.find((file) => remotePath.endsWith(file.path))?.size)
+        expect(signal).toBeInstanceOf(AbortSignal)
+        expect(openChannel).toBeTypeOf('function')
+        return {
+          write: vi.fn(async (chunk: Buffer) => {
+            written.set(
+              remotePath,
+              Buffer.concat([written.get(remotePath) ?? Buffer.alloc(0), chunk])
+            )
+          }),
+          close: vi.fn(async () => {}),
+          abort: vi.fn(async () => {})
+        }
+      }
+    )
+    const progress: unknown[] = []
+    const result = await transferSshRelayRuntimeTreeViaWindowsSystemSsh({
+      tree,
+      connection: connection(),
+      remoteStagingRoot: remoteRoot,
+      maximumConcurrency: 2,
+      signal: new AbortController().signal,
+      onProgress: (value) => progress.push(value)
+    })
+
+    expect(result).toMatchObject({
+      remoteStagingRoot: remoteRoot,
+      filesCompleted: tree.fileCount,
+      totalFiles: tree.fileCount,
+      bytesTransferred: tree.expandedBytes,
+      totalBytes: tree.expandedBytes
+    })
+    expect(stagingControl.mock.calls[0]?.[0]).toMatchObject({
+      operation: 'create-root',
+      remoteRoot
+    })
+    const directoryCalls = stagingControl.mock.calls.slice(1).map(([value]) => value)
+    const expectedDirectories = [...tree.directories]
+      .sort(
+        (left, right) =>
+          left.path.split('/').length - right.path.split('/').length ||
+          (left.path < right.path ? -1 : left.path > right.path ? 1 : 0)
+      )
+      .map((directory) => ({
+        operation: 'create-directory',
+        remoteRoot,
+        remotePath: `${remoteRoot}/${directory.path}`
+      }))
+    expect(directoryCalls).toEqual(
+      expectedDirectories.map((value) => expect.objectContaining(value))
+    )
+    expect(events.findIndex((event) => event.startsWith('file:'))).toBe(tree.directories.length + 1)
+    for (const file of tree.files) {
+      const remotePath = `${remoteRoot}/${file.path}`
+      expect(written.get(remotePath)).toEqual(await readFile(file.localPath))
+      expect(openFileDestination).toHaveBeenCalledWith(
+        expect.objectContaining({ remotePath, expectedSize: file.size })
+      )
+    }
+    expect(progress.length).toBeGreaterThan(0)
+    expect(progress.at(-1)).toMatchObject({
+      filesCompleted: tree.fileCount,
+      bytesTransferred: tree.expandedBytes,
+      activeFiles: 0
+    })
+    expect(progress.some((value) => 'path' in (value as object))).toBe(false)
+  })
+
+  it('does not clean a pre-existing root when exclusive creation fails', async () => {
+    const tree = await treeFixture()
+    const collision = new Error('root exists')
+    stagingControl.mockRejectedValueOnce(collision)
+    await expect(
+      transferSshRelayRuntimeTreeViaWindowsSystemSsh({
+        tree,
+        connection: connection(),
+        remoteStagingRoot: 'C:/existing/stage',
+        signal: new AbortController().signal
+      })
+    ).rejects.toBe(collision)
+    expect(stagingControl).toHaveBeenCalledOnce()
+  })
+
+  it('defaults to one active destination and permits no more than four', async () => {
+    const tree = await treeFixture()
+    for (const maximumConcurrency of [undefined, 4]) {
+      const retained = retainDestinationWrites()
+      const transfer = transferSshRelayRuntimeTreeViaWindowsSystemSsh({
+        tree,
+        connection: connection(),
+        remoteStagingRoot: 'C:/private/stage',
+        maximumConcurrency,
+        signal: new AbortController().signal
+      })
+      const expected = maximumConcurrency ?? 1
+      await vi.waitFor(() => expect(retained.peak()).toBe(expected))
+      retained.release()
+      await transfer
+      expect(retained.peak()).toBeLessThanOrEqual(expected)
+      openFileDestination.mockReset()
+    }
+  })
+
+  it('cleans an owned root after a directory failure', async () => {
+    const tree = await treeFixture()
+    const primary = new Error('directory denied')
+    stagingControl.mockImplementation(async ({ operation }) => {
+      if (operation === 'create-directory') {
+        throw primary
+      }
+    })
+    await expect(
+      transferSshRelayRuntimeTreeViaWindowsSystemSsh({
+        tree,
+        connection: connection(),
+        remoteStagingRoot: 'C:/private/stage',
+        signal: new AbortController().signal
+      })
+    ).rejects.toBe(primary)
+    expect(stagingControl.mock.calls.map(([value]) => value.operation)).toEqual([
+      'create-root',
+      'create-directory',
+      'remove-root'
+    ])
+  })
+
+  it('joins file and owned-root cleanup failures', async () => {
+    const tree = await treeFixture()
+    const primary = new Error('remote disk full')
+    const cleanup = new Error('endpoint protection lock')
+    openFileDestination.mockRejectedValueOnce(primary)
+    stagingControl.mockImplementation(async ({ operation }: { operation: string }) => {
+      if (operation === 'remove-root') {
+        throw cleanup
+      }
+    })
+    await expect(
+      transferSshRelayRuntimeTreeViaWindowsSystemSsh({
+        tree,
+        connection: connection(),
+        remoteStagingRoot: 'C:/private/stage',
+        signal: new AbortController().signal
+      })
+    ).rejects.toMatchObject({ errors: expect.arrayContaining([primary, cleanup]) })
+    expect(stagingControl.mock.calls.at(-1)?.[0]).toMatchObject({ operation: 'remove-root' })
+  })
+
+  it('settles a retained write before cleanup on cancellation and emits no later progress', async () => {
+    const tree = await treeFixture()
+    const controller = new AbortController()
+    const reason = new Error('cancelled Windows tree transfer')
+    const events: string[] = []
+    const progress: unknown[] = []
+    stagingControl.mockImplementation(async ({ operation }) => events.push(operation))
+    openFileDestination.mockImplementation(async ({ signal }: { signal: AbortSignal }) => ({
+      write: vi.fn(
+        () =>
+          new Promise<void>((_resolve, reject) => {
+            events.push('write-start')
+            signal.addEventListener('abort', () => reject(signal.reason), { once: true })
+          })
+      ),
+      close: vi.fn(async () => events.push('file-close')),
+      abort: vi.fn(async () => events.push('file-abort'))
+    }))
+    const transfer = transferSshRelayRuntimeTreeViaWindowsSystemSsh({
+      tree,
+      connection: connection(),
+      remoteStagingRoot: 'C:/private/stage',
+      signal: controller.signal,
+      onProgress: (value) => progress.push(value)
+    })
+    await vi.waitFor(() => expect(events).toContain('write-start'))
+    controller.abort(reason)
+    await expect(transfer).rejects.toBe(reason)
+    expect(events.indexOf('file-abort')).toBeLessThan(events.indexOf('remove-root'))
+    const settledProgress = progress.length
+    await new Promise((resolve) => setTimeout(resolve, 0))
+    expect(progress).toHaveLength(settledProgress)
+  })
+
+  it('bounds unresponsive owned-root cleanup below ten seconds', async () => {
+    const tree = await treeFixture()
+    vi.useFakeTimers()
+    const primary = new Error('file open failed')
+    openFileDestination.mockRejectedValueOnce(primary)
+    stagingControl.mockImplementation(({ operation, signal }) => {
+      if (operation !== 'remove-root') {
+        return Promise.resolve()
+      }
+      return new Promise((_resolve, reject) => {
+        signal.addEventListener('abort', () => reject(signal.reason), { once: true })
+      })
+    })
+    const startedAt = Date.now()
+    const transfer = transferSshRelayRuntimeTreeViaWindowsSystemSsh({
+      tree,
+      connection: connection(),
+      remoteStagingRoot: 'C:/private/stage',
+      signal: new AbortController().signal
+    })
+    const rejection = expect(transfer).rejects.toMatchObject({
+      errors: expect.arrayContaining([
+        primary,
+        expect.objectContaining({ message: expect.stringMatching(/cleanup timed out/i) })
+      ])
+    })
+    await vi.waitFor(() =>
+      expect(stagingControl.mock.calls.at(-1)?.[0]).toMatchObject({ operation: 'remove-root' })
+    )
+    await vi.advanceTimersByTimeAsync(
+      SSH_RELAY_RUNTIME_WINDOWS_TREE_TRANSFER_LIMITS.cleanupTimeoutMs
+    )
+    await rejection
+    expect(Date.now() - startedAt).toBeLessThan(10_000)
+  })
+})
diff --git a/src/main/ssh/ssh-relay-runtime-windows-tree-transfer.ts b/src/main/ssh/ssh-relay-runtime-windows-tree-transfer.ts
new file mode 100644
index 00000000000..bea22050d55
--- /dev/null
+++ b/src/main/ssh/ssh-relay-runtime-windows-tree-transfer.ts
@@ -0,0 +1,192 @@
+import { assertSafeRemotePathSegment, normalizeWindowsRemotePath } from './ssh-remote-platform'
+import type { SshRelayRuntimeScannedSourceTree } from './ssh-relay-runtime-source-scan'
+import {
+  streamSshRelayRuntimeSourceTree,
+  type SshRelayRuntimeSourceStreamOptions,
+  type SshRelayRuntimeSourceStreamResult
+} from './ssh-relay-runtime-source-stream'
+import {
+  openSshRelayRuntimeSystemSshFileChannel,
+  type SshRelayRuntimeSystemSshConnection
+} from './ssh-relay-runtime-system-ssh-file-channel'
+import { openSshRelayRuntimeWindowsFileDestination } from './ssh-relay-runtime-windows-file-destination'
+import {
+  runSshRelayRuntimeWindowsStagingControl,
+  type RunSshRelayRuntimeWindowsStagingControlOptions
+} from './ssh-relay-runtime-windows-staging-control'
+
+export type SshRelayRuntimeWindowsTreeTransferOptions = Readonly<{
+  tree: SshRelayRuntimeScannedSourceTree
+  connection: SshRelayRuntimeSystemSshConnection
+  remoteStagingRoot: string
+  signal: AbortSignal
+  maximumConcurrency?: number
+  onProgress?: SshRelayRuntimeSourceStreamOptions['onProgress']
+}>
+
+export type SshRelayRuntimeWindowsTreeTransferResult = Readonly<
+  SshRelayRuntimeSourceStreamResult & { remoteStagingRoot: string }
+>
+
+const MAXIMUM_CONCURRENT_FILES = 4
+const CLEANUP_TIMEOUT_MS = 5_000
+
+type OpenChannel = RunSshRelayRuntimeWindowsStagingControlOptions['openChannel']
+
+function normalizeStagingRoot(value: string): string {
+  if (
+    typeof value !== 'string' ||
+    value === '' ||
+    value.includes('\0') ||
+    value.includes('\r') ||
+    value.includes('\n')
+  ) {
+    throw new Error('SSH relay runtime Windows staging root is invalid')
+  }
+  const normalized = normalizeWindowsRemotePath(value)
+  const driveRooted = /^[A-Za-z]:\//u.test(normalized)
+  const uncRooted = /^\/\/[^/]+\/[^/]+\//u.test(normalized)
+  if ((!driveRooted && !uncRooted) || normalized.endsWith('/')) {
+    throw new Error('SSH relay runtime Windows staging root is invalid')
+  }
+  const segments = driveRooted ? normalized.slice(3).split('/') : normalized.slice(2).split('/')
+  try {
+    for (const segment of segments) {
+      assertSafeRemotePathSegment(segment, 'windows')
+    }
+  } catch {
+    throw new Error('SSH relay runtime Windows staging root is invalid')
+  }
+  return normalized
+}
+
+function validateOptions(options: SshRelayRuntimeWindowsTreeTransferOptions): number {
+  const concurrency = options?.maximumConcurrency ?? 1
+  if (
+    !options?.tree ||
+    !options.connection ||
+    typeof options.connection.usesSystemSshTransport !== 'function' ||
+    typeof options.connection.exec !== 'function' ||
+    !options.signal ||
+    typeof options.signal.throwIfAborted !== 'function' ||
+    !Number.isInteger(concurrency) ||
+    concurrency < 1 ||
+    concurrency > MAXIMUM_CONCURRENT_FILES
+  ) {
+    throw new Error('SSH relay runtime Windows tree transfer input or concurrency is invalid')
+  }
+  if (options.tree.os !== 'win32') {
+    throw new Error('SSH relay runtime Windows tree transfer requires a Windows tree')
+  }
+  if (!options.connection.usesSystemSshTransport()) {
+    throw new Error('SSH relay runtime Windows tree transfer requires system SSH transport')
+  }
+  return concurrency
+}
+
+function remoteManifestPath(remoteStagingRoot: string, manifestPath: string): string {
+  const segments = manifestPath.split('/')
+  for (const segment of segments) {
+    assertSafeRemotePathSegment(segment, 'windows')
+  }
+  // Why: manifest paths are remote slash paths; client-native path utilities would corrupt them.
+  return `${remoteStagingRoot}/${segments.join('/')}`
+}
+
+function joinedFailure(primary: unknown, cleanupFailure: unknown | undefined): unknown {
+  return cleanupFailure === undefined
+    ? primary
+    : new AggregateError(
+        [primary, cleanupFailure],
+        'SSH relay runtime Windows tree transfer cleanup failed'
+      )
+}
+
+async function cleanupOwnedRoot(
+  remoteStagingRoot: string,
+  openChannel: OpenChannel
+): Promise<void> {
+  const controller = new AbortController()
+  // Why: caller cancellation initiates cleanup; a separate bounded signal lets cleanup still run.
+  const timeout = setTimeout(
+    () => controller.abort(new Error('SSH relay runtime Windows tree cleanup timed out')),
+    CLEANUP_TIMEOUT_MS
+  )
+  try {
+    await runSshRelayRuntimeWindowsStagingControl({
+      operation: 'remove-root',
+      remoteRoot: remoteStagingRoot,
+      signal: controller.signal,
+      openChannel
+    })
+  } finally {
+    clearTimeout(timeout)
+  }
+}
+
+export async function transferSshRelayRuntimeTreeViaWindowsSystemSsh(
+  options: SshRelayRuntimeWindowsTreeTransferOptions
+): Promise<SshRelayRuntimeWindowsTreeTransferResult> {
+  const maximumConcurrency = validateOptions(options)
+  const { tree, connection, signal, onProgress } = options
+  const remoteStagingRoot = normalizeStagingRoot(options.remoteStagingRoot)
+  const openChannel: OpenChannel = (command, exactSignal) =>
+    openSshRelayRuntimeSystemSshFileChannel(connection, command, exactSignal)
+  const runControl = (
+    control: Omit<RunSshRelayRuntimeWindowsStagingControlOptions, 'signal' | 'openChannel'>
+  ): Promise<void> => runSshRelayRuntimeWindowsStagingControl({ ...control, signal, openChannel })
+  signal.throwIfAborted()
+  let rootOwned = false
+
+  try {
+    await runControl({ operation: 'create-root', remoteRoot: remoteStagingRoot })
+    rootOwned = true
+    signal.throwIfAborted()
+
+    const directories = [...tree.directories].sort(
+      (left, right) =>
+        left.path.split('/').length - right.path.split('/').length ||
+        (left.path < right.path ? -1 : left.path > right.path ? 1 : 0)
+    )
+    for (const directory of directories) {
+      signal.throwIfAborted()
+      await runControl({
+        operation: 'create-directory',
+        remoteRoot: remoteStagingRoot,
+        remotePath: remoteManifestPath(remoteStagingRoot, directory.path)
+      })
+      signal.throwIfAborted()
+    }
+
+    const result = await streamSshRelayRuntimeSourceTree({
+      tree,
+      signal,
+      maximumConcurrency,
+      onProgress,
+      openDestination: (file, exactSignal) =>
+        openSshRelayRuntimeWindowsFileDestination({
+          remotePath: remoteManifestPath(remoteStagingRoot, file.path),
+          expectedSize: file.size,
+          signal: exactSignal,
+          openChannel
+        })
+    })
+    signal.throwIfAborted()
+    return Object.freeze({ remoteStagingRoot, ...result })
+  } catch (error) {
+    let cleanupFailure: unknown
+    if (rootOwned) {
+      try {
+        await cleanupOwnedRoot(remoteStagingRoot, openChannel)
+      } catch (cleanupError) {
+        cleanupFailure = cleanupError
+      }
+    }
+    throw joinedFailure(error, cleanupFailure)
+  }
+}
+
+export const SSH_RELAY_RUNTIME_WINDOWS_TREE_TRANSFER_LIMITS = Object.freeze({
+  maximumConcurrentFiles: MAXIMUM_CONCURRENT_FILES,
+  cleanupTimeoutMs: CLEANUP_TIMEOUT_MS
+})