perf(git): reuse queries and stop canceled catalog scans (#24923)

* perf(git): reuse queries and stop canceled catalog scans

* refactor(git): check relay filesystem error codes

src/main/git/repo-default-remote.test.ts

@@ -71,4 +71,42 @@ describe('getDefaultRemote', () => {
       'Failed to resolve default remote for repo.'
     )
   })
+
+  it('keeps configured branch precedence when a remote list is already available', async () => {
+    gitExecFileAsyncMock.mockImplementation(async (argv: string[]) => {
+      if (argv[0] === 'for-each-ref') {
+        return { stdout: 'refs/remotes/origin/HEAD\0refs/remotes/origin/main\n' }
+      }
+      if (argv[0] === 'config') {
+        return { stdout: 'upstream\n' }
+      }
+      throw new Error('unexpected command')
+    })
+
+    await expect(getDefaultRemote('/repo', {}, ['origin', 'upstream'])).resolves.toBe('upstream')
+    expect(gitExecFileAsyncMock.mock.calls.some(([args]) => args[0] === 'remote')).toBe(false)
+  })
+
+  it.each([
+    [['origin', 'upstream'], 'origin'],
+    [['company'], 'company']
+  ])('reuses known remotes %j when no default ref resolves', async (remotes, expected) => {
+    gitExecFileAsyncMock.mockRejectedValue(new Error('missing ref'))
+
+    await expect(getDefaultRemote('/repo', {}, remotes)).resolves.toBe(expected)
+    expect(gitExecFileAsyncMock.mock.calls.some(([args]) => args[0] === 'remote')).toBe(false)
+  })
+
+  it.each([
+    [[], 'Repo has no configured git remotes.'],
+    [
+      ['upstream', 'fork'],
+      'Repo has multiple remotes (upstream, fork) and no default is configured. Set branch.<default>.remote.'
+    ]
+  ])('preserves errors for known remotes %j', async (remotes, message) => {
+    gitExecFileAsyncMock.mockRejectedValue(new Error('missing ref'))
+
+    await expect(getDefaultRemote('/repo', {}, remotes)).rejects.toThrow(message)
+    expect(gitExecFileAsyncMock.mock.calls.some(([args]) => args[0] === 'remote')).toBe(false)
+  })
 })

src/main/git/repo.ts

@@ -125,7 +125,8 @@ export async function getRemoteCount(path: string): Promise<number> {
 /** Resolve the configured push remote without assuming a provider. */
 export async function getDefaultRemote(
   path: string,
-  options: LocalGitExecOptions = {}
+  options: LocalGitExecOptions = {},
+  knownRemoteNames?: readonly string[]
 ): Promise<string> {
   const defaultRef = await getDefaultBaseRefAsync(path, options)
   const defaultBranch = defaultRef
@@ -150,11 +151,14 @@ export async function getDefaultRemote(
   }
 
   try {
-    const { stdout } = await gitExecFileAsync(['remote'], gitExecOptions(path, options))
-    const remotes = stdout
-      .split('\n')
-      .map((line) => line.trim())
-      .filter(Boolean)
+    let remotes = knownRemoteNames
+    if (remotes === undefined) {
+      const { stdout } = await gitExecFileAsync(['remote'], gitExecOptions(path, options))
+      remotes = stdout
+        .split('\n')
+        .map((line) => line.trim())
+        .filter(Boolean)
+    }
     if (remotes.includes('origin')) {
       return 'origin'
     }

src/main/git/worktree-list-reader-cancellation.test.ts

@@ -0,0 +1,156 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import type * as FsPromises from 'node:fs/promises'
+import type { GitWorktreeInfo } from '../../shared/worktree/types'
+import type { gitExecFileAsync } from './runner'
+
+const { statProbe, gitExec } = vi.hoisted(() => ({
+  statProbe: vi.fn<(worktreePath: string) => Promise<void>>(),
+  gitExec: vi.fn<typeof gitExecFileAsync>()
+}))
+
+vi.mock('node:fs/promises', async (importOriginal) => ({
+  ...(await importOriginal<typeof FsPromises>()),
+  stat: statProbe
+}))
+vi.mock('./runner', () => ({
+  gitExecFileAsync: gitExec,
+  translateWslOutputPaths: (output: string) => output
+}))
+vi.mock('../../shared/git-worktree-admin', () => ({
+  annotateWorktreeLocksFromAdmin: async (_repoPath: string, rows: GitWorktreeInfo[]) => rows
+}))
+
+import { clearGitCapabilityStateForTests } from './git-capability-state'
+import { readWorktreeList } from './worktree-list-reader'
+
+function porcelainRow(worktreePath: string, markers: string[] = []): string {
+  return [
+    `worktree ${worktreePath}`,
+    `HEAD ${'a'.repeat(40)}`,
+    'branch refs/heads/main',
+    ...markers,
+    '',
+    ''
+  ].join('\n')
+}
+
+let porcelain = ''
+function nextTurn(): Promise<void> {
+  return new Promise((resolve) => setImmediate(resolve))
+}
+
+beforeEach(() => {
+  clearGitCapabilityStateForTests()
+  statProbe.mockReset()
+  gitExec.mockReset()
+  porcelain =
+    porcelainRow('/repo') +
+    Array.from({ length: 32 }, (_, index) => porcelainRow(`/repo/task-${index}`)).join('')
+  gitExec.mockImplementation(async (args) => {
+    if (args.includes('-z')) {
+      throw Object.assign(new Error("unknown switch `z'"), { stderr: "error: unknown switch `z'" })
+    }
+    return { stdout: porcelain, stderr: '' }
+  })
+})
+
+describe('old-Git native worktree listing cancellation', () => {
+  it('rejects before pending existence probes finish and prevents further probes', async () => {
+    const controller = new AbortController()
+    const reason = new Error('Listing closed')
+    const releases: (() => void)[] = []
+    statProbe.mockImplementation(() => new Promise((resolve) => releases.push(resolve)))
+    const outcome = vi.fn<(result: unknown) => void>()
+    const observed = readWorktreeList('/repo', { signal: controller.signal }).then(
+      (result) => outcome(result),
+      (error: unknown) => outcome(error)
+    )
+    try {
+      await nextTurn()
+      expect(gitExec.mock.calls.map(([args]) => args)).toEqual([
+        ['worktree', 'list', '--porcelain', '-z'],
+        ['worktree', 'list', '--porcelain']
+      ])
+      expect(statProbe).toHaveBeenCalledTimes(8)
+      controller.abort(reason)
+      await nextTurn()
+      expect(outcome).toHaveBeenCalledExactlyOnceWith(reason)
+      expect(statProbe).toHaveBeenCalledTimes(8)
+    } finally {
+      releases.splice(0).forEach((release) => release())
+    }
+    await observed
+    await nextTurn()
+    expect(outcome).toHaveBeenCalledExactlyOnceWith(reason)
+    expect(statProbe).toHaveBeenCalledTimes(8)
+  })
+
+  it('starts no existence probes when the request is already aborted', async () => {
+    const controller = new AbortController()
+    const reason = new Error('Already closed')
+    controller.abort(reason)
+    await expect(readWorktreeList('/repo', { signal: controller.signal })).rejects.toBe(reason)
+    await nextTurn()
+    expect(statProbe).not.toHaveBeenCalled()
+  })
+
+  it('handles synchronous cancellation by the first existence probe without an unhandled rejection', async () => {
+    const controller = new AbortController()
+    const reason = new Error('First probe closed the request')
+    const releases: (() => void)[] = []
+    const unhandled: unknown[] = []
+    const onUnhandled = (error: unknown): void => {
+      unhandled.push(error)
+    }
+    process.on('unhandledRejection', onUnhandled)
+    statProbe.mockImplementation(() => {
+      controller.abort(reason)
+      return new Promise((resolve) => releases.push(resolve))
+    })
+    try {
+      await expect(readWorktreeList('/repo', { signal: controller.signal })).rejects.toBe(reason)
+      expect(statProbe).toHaveBeenCalledTimes(1)
+      releases.splice(0).forEach((release) => release())
+      await nextTurn()
+      expect(statProbe).toHaveBeenCalledTimes(1)
+      expect(unhandled).toEqual([])
+    } finally {
+      releases.splice(0).forEach((release) => release())
+      process.off('unhandledRejection', onUnhandled)
+    }
+  })
+
+  it('keeps lock and prunable protections and treats only ENOENT as absence', async () => {
+    porcelain = [
+      porcelainRow('/repo'),
+      porcelainRow('/repo/bare', ['bare']),
+      porcelainRow('/repo/locked', ['locked agent session']),
+      porcelainRow('/repo/prunable', ['prunable missing directory']),
+      porcelainRow('/repo/missing'),
+      porcelainRow('/repo/denied'),
+      porcelainRow('/repo/live')
+    ].join('')
+    statProbe.mockImplementation(async (worktreePath) => {
+      if (worktreePath.endsWith('/missing')) {
+        throw Object.assign(new Error('missing'), { code: 'ENOENT' })
+      }
+      if (worktreePath.endsWith('/denied')) {
+        throw Object.assign(new Error('denied'), { code: 'EACCES' })
+      }
+    })
+    const result = await readWorktreeList('/repo')
+    expect(statProbe.mock.calls.map(([worktreePath]) => worktreePath)).toEqual([
+      '/repo/missing',
+      '/repo/denied',
+      '/repo/live'
+    ])
+    expect(result.filter((row) => row.prunable).map((row) => row.path)).toEqual([
+      '/repo/prunable',
+      '/repo/missing'
+    ])
+    expect(result.find((row) => row.path === '/repo/locked')).toMatchObject({
+      locked: true,
+      lockReason: 'agent session'
+    })
+  })
+})

src/main/git/worktree-list-reader.ts

@@ -1,3 +1,4 @@
+import { throwIfSignalAborted, waitForPromiseWithSignal } from '../../shared/abort-signal-reason'
 import { annotateWorktreeLocksFromAdmin } from '../../shared/git-worktree-admin'
 import { stat } from 'node:fs/promises'
 import type { GitWorktreeInfo } from '../../shared/worktree/types'
@@ -263,6 +264,7 @@ async function annotatePrunableByExistence(
 
   async function probeNext(): Promise<void> {
     while (nextIndex < worktrees.length) {
+      throwIfSignalAborted(options.signal)
       const index = nextIndex
       nextIndex += 1
       const worktree = worktrees[index]
@@ -287,7 +289,11 @@ async function annotatePrunableByExistence(
   }
 
   const workerCount = Math.min(PRUNABLE_EXISTENCE_PROBE_CONCURRENCY, worktrees.length)
-  await Promise.all(Array.from({ length: workerCount }, () => probeNext()))
+  await waitForPromiseWithSignal(
+    Promise.all(Array.from({ length: workerCount }, () => probeNext())),
+    options.signal
+  )
+  throwIfSignalAborted(options.signal)
   return annotated
 }
 

src/main/git/worktree-listing-sparse-cancellation.test.ts

@@ -0,0 +1,140 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import type { GitWorktreeInfo } from '../../shared/worktree/types'
+import type { GitWorktreeExecOptions } from './worktree-operation-options'
+
+const { sparseProbe } = vi.hoisted(() => ({
+  sparseProbe:
+    vi.fn<
+      (repoPath: string, worktreePath: string, options?: GitWorktreeExecOptions) => Promise<boolean>
+    >()
+}))
+
+vi.mock('./worktree-sparse-checkout-cache', () => ({
+  detectSparseCheckoutCached: sparseProbe
+}))
+vi.mock('./worktree-list-reader', () => ({
+  readCheckedOutBranchRef: vi.fn(),
+  readRepoCommonDirFromGit: vi.fn(),
+  readRepoLocation: vi.fn(),
+  readTranslatedWorktreeGraph: vi.fn(),
+  readWorktreeHeadOid: vi.fn(),
+  readWorktreeList: vi.fn()
+}))
+
+import { annotateSparseCheckoutStatus } from './worktree-listing'
+
+function listedWorktree(index: number): GitWorktreeInfo {
+  return {
+    path: `/repo/task-${index}`,
+    head: 'a'.repeat(40),
+    branch: `refs/heads/task-${index}`,
+    isBare: false,
+    isMainWorktree: false
+  }
+}
+
+function nextTurn(): Promise<void> {
+  return new Promise((resolve) => setImmediate(resolve))
+}
+
+beforeEach(() => {
+  sparseProbe.mockReset()
+})
+
+describe('sparse worktree listing cancellation', () => {
+  it('rejects while eight probes are pending and claims no more rows after they settle', async () => {
+    const rows = Array.from({ length: 32 }, (_, index) => listedWorktree(index))
+    const controller = new AbortController()
+    const reason = new Error('Listing closed')
+    const releases: (() => void)[] = []
+    sparseProbe.mockImplementation(
+      () => new Promise((resolve) => releases.push(() => resolve(true)))
+    )
+    const outcome = vi.fn<(result: unknown) => void>()
+    const observed = annotateSparseCheckoutStatus('/repo', rows, {
+      signal: controller.signal,
+      wslDistro: 'Ubuntu'
+    }).then(
+      (result) => outcome(result),
+      (error: unknown) => outcome(error)
+    )
+
+    try {
+      await nextTurn()
+      expect(sparseProbe).toHaveBeenCalledTimes(8)
+      expect(sparseProbe).toHaveBeenCalledWith('/repo', rows[0]?.path, {
+        signal: controller.signal,
+        wslDistro: 'Ubuntu'
+      })
+      controller.abort(reason)
+      await nextTurn()
+      expect(outcome).toHaveBeenCalledExactlyOnceWith(reason)
+      expect(sparseProbe).toHaveBeenCalledTimes(8)
+    } finally {
+      releases.splice(0).forEach((release) => release())
+    }
+    await observed
+    await nextTurn()
+    expect(sparseProbe).toHaveBeenCalledTimes(8)
+    expect(outcome).toHaveBeenCalledExactlyOnceWith(reason)
+    expect(rows.every((row) => row.isSparse === undefined)).toBe(true)
+  })
+
+  it('starts no probes for a pre-aborted request, including an empty listing', async () => {
+    const controller = new AbortController()
+    const reason = new Error('Already closed')
+    controller.abort(reason)
+    for (const rows of [[listedWorktree(0)], []]) {
+      await expect(
+        annotateSparseCheckoutStatus('/repo', rows, { signal: controller.signal })
+      ).rejects.toBe(reason)
+    }
+    await nextTurn()
+    expect(sparseProbe).not.toHaveBeenCalled()
+  })
+
+  it('observes worker rejections when the first probe synchronously aborts the request', async () => {
+    const controller = new AbortController()
+    const reason = new Error('First probe closed the request')
+    const releases: (() => void)[] = []
+    const unhandled: unknown[] = []
+    const onUnhandled = (error: unknown): void => {
+      unhandled.push(error)
+    }
+    process.on('unhandledRejection', onUnhandled)
+    sparseProbe.mockImplementation(() => {
+      controller.abort(reason)
+      return new Promise((resolve) => releases.push(() => resolve(true)))
+    })
+    try {
+      await expect(
+        annotateSparseCheckoutStatus(
+          '/repo',
+          Array.from({ length: 32 }, (_, index) => listedWorktree(index)),
+          { signal: controller.signal }
+        )
+      ).rejects.toBe(reason)
+      expect(sparseProbe).toHaveBeenCalledTimes(1)
+      releases.splice(0).forEach((release) => release())
+      await nextTurn()
+      expect(sparseProbe).toHaveBeenCalledTimes(1)
+      expect(unhandled).toEqual([])
+    } finally {
+      releases.splice(0).forEach((release) => release())
+      process.off('unhandledRejection', onUnhandled)
+    }
+  })
+
+  it('preserves existing sparse and bare rows during a successful listing', async () => {
+    const rows = [
+      { ...listedWorktree(0), isBare: true },
+      { ...listedWorktree(1), isSparse: true },
+      listedWorktree(2)
+    ]
+    sparseProbe.mockResolvedValue(true)
+    const result = await annotateSparseCheckoutStatus('/repo', rows)
+    expect(sparseProbe).toHaveBeenCalledExactlyOnceWith('/repo', rows[2]?.path, {})
+    expect(result).toEqual([rows[0], rows[1], { ...rows[2], isSparse: true }])
+    expect(rows[2]?.isSparse).toBeUndefined()
+  })
+})

src/main/git/worktree-listing.ts

@@ -1,3 +1,4 @@
+import { throwIfSignalAborted, waitForPromiseWithSignal } from '../../shared/abort-signal-reason'
 import { readFile, realpath, stat } from 'node:fs/promises'
 import { join, posix } from 'node:path'
 import { isDefinitiveAbsence } from '../../shared/definitive-filesystem-absence'
@@ -128,6 +129,7 @@ export async function annotateSparseCheckoutStatus(
 
   async function detectNext(): Promise<void> {
     while (nextIndex < worktrees.length) {
+      throwIfSignalAborted(options.signal)
       const index = nextIndex
       nextIndex += 1
       const worktree = worktrees[index]
@@ -135,6 +137,7 @@ export async function annotateSparseCheckoutStatus(
         continue
       }
       const isSparse = await detectSparseCheckoutCached(repoPath, worktree.path, options)
+      throwIfSignalAborted(options.signal)
       if (isSparse) {
         annotated[index] = { ...worktree, isSparse }
       }
@@ -143,7 +146,11 @@ export async function annotateSparseCheckoutStatus(
 
   // Why: cap concurrency so status-poll refreshes don't fan out many sparse-checkout filesystem probes at once.
   const workerCount = Math.min(SPARSE_CHECKOUT_DETECTION_CONCURRENCY, worktrees.length)
-  await Promise.all(Array.from({ length: workerCount }, () => detectNext()))
+  await waitForPromiseWithSignal(
+    Promise.all(Array.from({ length: workerCount }, () => detectNext())),
+    options.signal
+  )
+  throwIfSignalAborted(options.signal)
   return annotated
 }
 

src/main/github/review-head-remote.test.ts

@@ -98,7 +98,7 @@ describe('resolveGitHubReviewHeadRemote', () => {
 
     expect(remote).toBe('origin')
     expect(getGitHubApiRepositoryForRemoteMock).not.toHaveBeenCalled()
-    expect(getDefaultRemoteMock).toHaveBeenCalledWith('/repo', { wslDistro: 'Ubuntu' })
+    expect(getDefaultRemoteMock).toHaveBeenCalledWith('/repo', { wslDistro: 'Ubuntu' }, ['origin'])
   })
 
   it('prefers origin over other remotes on SSH repos when no identity resolves', async () => {

src/main/github/review-head-remote.ts

@@ -49,5 +49,5 @@ export async function resolveGitHubReviewHeadRemote(args: {
   if (args.connectionId) {
     return pickPreferredGitRemote(remotes)
   }
-  return getDefaultRemote(args.repoPath, args.localGitOptions ?? {})
+  return getDefaultRemote(args.repoPath, args.localGitOptions ?? {}, remotes)
 }

src/main/ipc/worktrees-wsl-runtime-routing.test.ts

@@ -462,7 +462,11 @@ describe('registerWorktreeHandlers', () => {
       ['rev-parse', '--verify', 'origin/feature/add-feature'],
       { cwd: '/workspace/repo', wslDistro: 'Ubuntu' }
     )
-    expect(getDefaultRemoteMock).toHaveBeenCalledWith('/workspace/repo', { wslDistro: 'Ubuntu' })
+    expect(getDefaultRemoteMock).toHaveBeenCalledWith(
+      '/workspace/repo',
+      { wslDistro: 'Ubuntu' },
+      []
+    )
     expect(result).toMatchObject({
       baseBranch: 'def456',
       headSha: 'def456',

src/relay/git-handler-worktree-existence-cancellation.test.ts

@@ -0,0 +1,108 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import type * as FsPromises from 'node:fs/promises'
+import type { GitWorktreeInfo } from '../shared/worktree/types'
+
+const { statProbe } = vi.hoisted(() => ({
+  statProbe: vi.fn<(worktreePath: string) => Promise<void>>()
+}))
+vi.mock('node:fs/promises', async (importOriginal) => ({
+  ...(await importOriginal<typeof FsPromises>()),
+  stat: statProbe
+}))
+vi.mock('../shared/git-worktree-admin', () => ({
+  annotateWorktreeLocksFromAdmin: vi.fn()
+}))
+
+import { annotatePrunableWorktreesByExistence } from './git-handler-worktree-list'
+
+function listedWorktree(index: number): GitWorktreeInfo {
+  return {
+    path: `/remote/repo/task-${index}`,
+    head: 'a'.repeat(40),
+    branch: `refs/heads/task-${index}`,
+    isBare: false,
+    isMainWorktree: false
+  }
+}
+
+function nextTurn(): Promise<void> {
+  return new Promise((resolve) => setImmediate(resolve))
+}
+
+beforeEach(() => {
+  statProbe.mockReset()
+})
+
+describe('relay worktree existence cancellation', () => {
+  it('rejects before eight pending stats finish and starts no more after they settle', async () => {
+    const rows = Array.from({ length: 32 }, (_, index) => listedWorktree(index))
+    const controller = new AbortController()
+    const reason = new Error('Remote listing closed')
+    const releases: (() => void)[] = []
+    statProbe.mockImplementation(() => new Promise((resolve) => releases.push(resolve)))
+    const outcome = vi.fn<(result: unknown) => void>()
+    const observed = annotatePrunableWorktreesByExistence(rows, controller.signal).then(
+      (result) => outcome(result),
+      (error: unknown) => outcome(error)
+    )
+    try {
+      await nextTurn()
+      expect(statProbe).toHaveBeenCalledTimes(8)
+      controller.abort(reason)
+      await nextTurn()
+      expect(outcome).toHaveBeenCalledExactlyOnceWith(reason)
+      expect(statProbe).toHaveBeenCalledTimes(8)
+    } finally {
+      releases.splice(0).forEach((release) => release())
+    }
+    await observed
+    await nextTurn()
+    expect(statProbe).toHaveBeenCalledTimes(8)
+    expect(outcome).toHaveBeenCalledExactlyOnceWith(reason)
+    expect(rows.every((row) => row.prunable === undefined)).toBe(true)
+  })
+
+  it('starts no stats for an already-aborted request, including an empty catalog', async () => {
+    const controller = new AbortController()
+    const reason = new Error('Already closed')
+    controller.abort(reason)
+    for (const rows of [[listedWorktree(0)], []]) {
+      await expect(annotatePrunableWorktreesByExistence(rows, controller.signal)).rejects.toBe(
+        reason
+      )
+    }
+    await nextTurn()
+    expect(statProbe).not.toHaveBeenCalled()
+  })
+
+  it('handles synchronous abort in the first stat without abandoning rejected workers', async () => {
+    const controller = new AbortController()
+    const reason = new Error('First probe closed the request')
+    const releases: (() => void)[] = []
+    const unhandled: unknown[] = []
+    const onUnhandled = (error: unknown): void => {
+      unhandled.push(error)
+    }
+    process.on('unhandledRejection', onUnhandled)
+    statProbe.mockImplementation(() => {
+      controller.abort(reason)
+      return new Promise((resolve) => releases.push(resolve))
+    })
+    try {
+      await expect(
+        annotatePrunableWorktreesByExistence(
+          Array.from({ length: 32 }, (_, index) => listedWorktree(index)),
+          controller.signal
+        )
+      ).rejects.toBe(reason)
+      expect(statProbe).toHaveBeenCalledTimes(1)
+      releases.splice(0).forEach((release) => release())
+      await nextTurn()
+      expect(statProbe).toHaveBeenCalledTimes(1)
+      expect(unhandled).toEqual([])
+    } finally {
+      releases.splice(0).forEach((release) => release())
+      process.off('unhandledRejection', onUnhandled)
+    }
+  })
+})

src/relay/git-handler-worktree-list-cancellation.test.ts

@@ -0,0 +1,209 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import type * as FsPromises from 'node:fs/promises'
+import type { GitWorktreeInfo } from '../shared/worktree/types'
+import type { GitHandlerOperationHost } from './git-handler-operation-context'
+import { createGitHandlerRelay } from './git-handler-test-harness'
+
+const { statProbe, annotateLocks } = vi.hoisted(() => ({
+  statProbe: vi.fn<(worktreePath: string) => Promise<void>>(),
+  annotateLocks:
+    vi.fn<
+      (
+        repoPath: string,
+        rows: GitWorktreeInfo[],
+        options?: { signal?: AbortSignal }
+      ) => Promise<GitWorktreeInfo[]>
+    >()
+}))
+vi.mock('node:fs/promises', async (importOriginal) => ({
+  ...(await importOriginal<typeof FsPromises>()),
+  stat: statProbe
+}))
+vi.mock('../shared/git-worktree-admin', () => ({
+  annotateWorktreeLocksFromAdmin: annotateLocks
+}))
+
+function porcelainRow(worktreePath: string): string {
+  return `worktree ${worktreePath}\nHEAD ${'a'.repeat(40)}\nbranch refs/heads/main\n\n`
+}
+
+function unsupportedZError(): Error {
+  return Object.assign(new Error('git usage error'), {
+    code: 129,
+    stderr: 'usage: git worktree list [<options>]\n'
+  })
+}
+
+function unsupportedPathFormatError(): Error {
+  return Object.assign(new Error('unsupported path format'), {
+    stderr: 'error: unknown option `path-format=absolute`\n'
+  })
+}
+
+function nextTurn(): Promise<void> {
+  return new Promise((resolve) => setImmediate(resolve))
+}
+
+let relay: ReturnType<typeof createGitHandlerRelay>
+
+beforeEach(() => {
+  relay = createGitHandlerRelay()
+  statProbe.mockReset()
+  annotateLocks.mockReset().mockImplementation(async (_repoPath, rows) => rows)
+})
+afterEach(() => relay.handler.dispose())
+
+describe('relay worktree listing request cancellation', () => {
+  it('forwards the dispatcher signal through the old-Git existence fallback', async () => {
+    const controller = new AbortController()
+    const reason = new Error('Remote request closed')
+    const porcelain =
+      porcelainRow('/remote/repo') +
+      Array.from({ length: 32 }, (_, index) => porcelainRow(`/remote/repo/task-${index}`)).join('')
+    const git = vi.fn<GitHandlerOperationHost['git']>(async (args) => {
+      if (args.includes('-z')) {
+        throw unsupportedZError()
+      }
+      return { stdout: porcelain, stderr: '' }
+    })
+    Object.assign(relay.handler, { git })
+    const releases: (() => void)[] = []
+    statProbe.mockImplementation(() => new Promise((resolve) => releases.push(resolve)))
+    const outcome = vi.fn<(result: unknown) => void>()
+    const observed = relay.dispatcher
+      .callRequest(
+        'git.listWorktrees',
+        { repoPath: '/remote/repo' },
+        { isStale: () => false, signal: controller.signal }
+      )
+      .then(
+        (result) => outcome(result),
+        (error: unknown) => outcome(error)
+      )
+    try {
+      await nextTurn()
+      expect(statProbe).toHaveBeenCalledTimes(8)
+      expect(git.mock.calls.map(([, , options]) => options?.signal)).toEqual([
+        controller.signal,
+        controller.signal
+      ])
+      expect(annotateLocks).toHaveBeenCalledWith('/remote/repo', expect.any(Array), {
+        signal: controller.signal
+      })
+      controller.abort(reason)
+      await nextTurn()
+      expect(outcome).toHaveBeenCalledExactlyOnceWith(reason)
+    } finally {
+      releases.splice(0).forEach((release) => release())
+    }
+    await observed
+    await nextTurn()
+    expect(statProbe).toHaveBeenCalledTimes(8)
+    expect(outcome).toHaveBeenCalledExactlyOnceWith(reason)
+  })
+
+  it.each(['preferred', 'fallback'] as const)(
+    'preserves cancellation from the %s normalization command',
+    async (mode) => {
+      const controller = new AbortController()
+      const reason = new Error('Normalization canceled')
+      const git = vi.fn<GitHandlerOperationHost['git']>(async (args, _cwd, options) => {
+        expect(options?.signal).toBe(controller.signal)
+        if (args[0] === 'worktree') {
+          return { stdout: porcelainRow('/remote/git-store'), stderr: '' }
+        }
+        if (mode === 'fallback' && args.includes('--path-format=absolute')) {
+          throw unsupportedPathFormatError()
+        }
+        controller.abort(reason)
+        throw reason
+      })
+      Object.assign(relay.handler, { git })
+      await expect(
+        relay.dispatcher.callRequest(
+          'git.listWorktrees',
+          { repoPath: '/remote/repo' },
+          { isStale: () => false, signal: controller.signal }
+        )
+      ).rejects.toBe(reason)
+      const locationCommands = git.mock.calls
+        .filter(([args]) => args[0] === 'rev-parse')
+        .map(([args]) => args)
+      expect(locationCommands).toEqual(
+        mode === 'preferred'
+          ? [
+              [
+                'rev-parse',
+                '--path-format=absolute',
+                '--show-toplevel',
+                '--git-common-dir',
+                '--git-dir'
+              ]
+            ]
+          : [
+              [
+                'rev-parse',
+                '--path-format=absolute',
+                '--show-toplevel',
+                '--git-common-dir',
+                '--git-dir'
+              ],
+              ['rev-parse', '--show-toplevel', '--git-common-dir', '--git-dir']
+            ]
+      )
+      expect(statProbe).not.toHaveBeenCalled()
+    }
+  )
+
+  it.each(['preferred', 'fallback'] as const)(
+    'keeps separate-git-dir normalization working with the %s command',
+    async (mode) => {
+      const controller = new AbortController()
+      const git = vi.fn<GitHandlerOperationHost['git']>(async (args, _cwd, options) => {
+        expect(options?.signal).toBe(controller.signal)
+        if (args[0] === 'worktree') {
+          return { stdout: porcelainRow('/remote/git-store'), stderr: '' }
+        }
+        if (mode === 'fallback' && args.includes('--path-format=absolute')) {
+          throw unsupportedPathFormatError()
+        }
+        return { stdout: '/remote/repo\n/remote/git-store\n/remote/git-store\n', stderr: '' }
+      })
+      Object.assign(relay.handler, { git })
+      await expect(
+        relay.dispatcher.callRequest(
+          'git.listWorktrees',
+          { repoPath: '/remote/repo' },
+          { isStale: () => false, signal: controller.signal }
+        )
+      ).resolves.toEqual([
+        expect.objectContaining({
+          path: '/remote/repo',
+          isMainWorktree: true
+        })
+      ])
+      expect(statProbe).not.toHaveBeenCalled()
+    }
+  )
+
+  it('rejects a pre-aborted dispatcher request before normalization or existence probes', async () => {
+    const controller = new AbortController()
+    const reason = new Error('Already closed')
+    controller.abort(reason)
+    const git = vi.fn<GitHandlerOperationHost['git']>(async () => ({
+      stdout: porcelainRow('/remote/git-store'),
+      stderr: ''
+    }))
+    Object.assign(relay.handler, { git })
+    await expect(
+      relay.dispatcher.callRequest(
+        'git.listWorktrees',
+        { repoPath: '/remote/repo' },
+        { isStale: () => false, signal: controller.signal }
+      )
+    ).rejects.toBe(reason)
+    expect(git).toHaveBeenCalledOnce()
+    expect(annotateLocks).not.toHaveBeenCalled()
+    expect(statProbe).not.toHaveBeenCalled()
+  })
+})

src/relay/git-handler-worktree-list.ts

@@ -1,3 +1,4 @@
+import { throwIfSignalAborted, waitForPromiseWithSignal } from '../shared/abort-signal-reason'
 import { annotateWorktreeLocksFromAdmin } from '../shared/git-worktree-admin'
 import { expandTilde } from './context'
 import { stat } from 'node:fs/promises'
@@ -46,21 +47,20 @@ const PRUNABLE_EXISTENCE_PROBE_CONCURRENCY = 8
  *  harmless backstop. The relay owns the filesystem, so a plain stat is
  *  authoritative. */
 export async function annotatePrunableWorktreesByExistence(
-  worktrees: GitWorktreeInfo[]
+  worktrees: GitWorktreeInfo[],
+  signal?: AbortSignal
 ): Promise<GitWorktreeInfo[]> {
   const annotated = [...worktrees]
   let nextIndex = 0
 
   async function probeNext(): Promise<void> {
     while (nextIndex < worktrees.length) {
+      throwIfSignalAborted(signal)
       const index = nextIndex
       nextIndex += 1
       const worktree = worktrees[index]
       const worktreePath = worktree?.path ?? ''
-      // Git only marks linked worktrees prunable, and never locked ones (a
-      // lock shields the registration even when the directory is missing). The
-      // Older Git locks are annotated from the host admin directory. A missing main
-      // worktree is surfaced by the repo-level failure paths.
+      // Locks protect missing linked worktrees; repository failures own the main row.
       if (
         !worktreePath ||
         worktree.isMainWorktree === true ||
@@ -73,7 +73,7 @@ export async function annotatePrunableWorktreesByExistence(
       try {
         await stat(worktreePath)
       } catch (err) {
-        if ((err as NodeJS.ErrnoException | undefined)?.code === 'ENOENT') {
+        if (typeof err === 'object' && err !== null && 'code' in err && err.code === 'ENOENT') {
           annotated[index] = { ...worktree, prunable: true }
         }
       }
@@ -81,7 +81,11 @@ export async function annotatePrunableWorktreesByExistence(
   }
 
   const workerCount = Math.min(PRUNABLE_EXISTENCE_PROBE_CONCURRENCY, worktrees.length)
-  await Promise.all(Array.from({ length: workerCount }, () => probeNext()))
+  await waitForPromiseWithSignal(
+    Promise.all(Array.from({ length: workerCount }, () => probeNext())),
+    signal
+  )
+  throwIfSignalAborted(signal)
   return annotated
 }
 

src/relay/git-handler-worktree-operations.ts

@@ -1,3 +1,4 @@
+import { throwIfSignalAborted } from '../shared/abort-signal-reason'
 import { annotateWorktreeLocksFromAdmin } from '../shared/git-worktree-admin'
 import * as path from 'node:path'
 import type { RequestContext } from './dispatcher'
@@ -67,7 +68,10 @@ export class GitHandlerWorktreeOperations extends GitHandlerOperationContext {
     }
   }
 
-  private async readRepoLocation(repoPath: string): Promise<RelayRepoLocation | undefined> {
+  private async readRepoLocation(
+    repoPath: string,
+    signal?: AbortSignal
+  ): Promise<RelayRepoLocation | undefined> {
     try {
       return await this.gitCapabilities.runWithFallback(
         'rev-parse-path-format',
@@ -80,7 +84,8 @@ export class GitHandlerWorktreeOperations extends GitHandlerOperationContext {
               '--git-common-dir',
               '--git-dir'
             ],
-            repoPath
+            repoPath,
+            { signal }
           )
           if (hasUnsupportedRevParsePathFormatEcho(stdout)) {
             // Why: old Git echoes the unknown option and exits zero; remember the signal though the paths still parse.
@@ -91,21 +96,25 @@ export class GitHandlerWorktreeOperations extends GitHandlerOperationContext {
         async () => {
           const { stdout } = await this.git(
             ['rev-parse', '--show-toplevel', '--git-common-dir', '--git-dir'],
-            repoPath
+            repoPath,
+            { signal }
           )
           return parseRelayRepoLocation(repoPath, stdout)
         },
         isUnsupportedRevParsePathFormatError
       )
     } catch {
+      throwIfSignalAborted(signal)
       return undefined
     }
   }
 
   private async normalizeMainWorktreePath(
     repoPath: string,
-    worktrees: GitWorktreeInfo[]
+    worktrees: GitWorktreeInfo[],
+    signal?: AbortSignal
   ): Promise<GitWorktreeInfo[]> {
+    throwIfSignalAborted(signal)
     const mainIndex = worktrees.findIndex((worktree) => worktree.isMainWorktree === true)
     const mainWorktree = worktrees[mainIndex]
     const mainPath = mainWorktree?.path ?? ''
@@ -115,7 +124,8 @@ export class GitHandlerWorktreeOperations extends GitHandlerOperationContext {
       return worktrees
     }
 
-    const location = await this.readRepoLocation(resolvedRepoPath)
+    const location = await this.readRepoLocation(resolvedRepoPath, signal)
+    throwIfSignalAborted(signal)
     if (!location) {
       return worktrees
     }
@@ -144,7 +154,8 @@ export class GitHandlerWorktreeOperations extends GitHandlerOperationContext {
         })
         return this.normalizeMainWorktreePath(
           repoPath,
-          parseWorktreeList(stdout, { nulDelimited: true })
+          parseWorktreeList(stdout, { nulDelimited: true }),
+          context?.signal
         )
       },
       async () => {
@@ -154,12 +165,17 @@ export class GitHandlerWorktreeOperations extends GitHandlerOperationContext {
         const { stdout } = await this.git(['worktree', 'list', '--porcelain'], repoPath, {
           signal: context?.signal
         })
-        const normalized = await this.normalizeMainWorktreePath(repoPath, parseWorktreeList(stdout))
+        const normalized = await this.normalizeMainWorktreePath(
+          repoPath,
+          parseWorktreeList(stdout),
+          context?.signal
+        )
         // Why: Git <2.31 emits no `prunable` annotation, so probe each linked worktree's existence instead of trusting stale registrations (issue #8389).
         return annotatePrunableWorktreesByExistence(
           await annotateWorktreeLocksFromAdmin(expandTilde(repoPath), normalized, {
             signal: context?.signal
-          })
+          }),
+          context?.signal
         )
       },
       isUnsupportedWorktreeListZError

src/shared/abort-signal-reason.test.ts

@@ -0,0 +1,14 @@
+import { expect, it } from 'vitest'
+import { waitForPromiseWithSignal } from './abort-signal-reason'
+
+it('observes work that rejects after its caller has already canceled', async () => {
+  const controller = new AbortController()
+  const reason = new Error('Caller canceled')
+  controller.abort(reason)
+  const work = new Promise<never>((_resolve, reject) => {
+    queueMicrotask(() => reject(new Error('Late filesystem failure')))
+  })
+
+  await expect(waitForPromiseWithSignal(work, controller.signal)).rejects.toBe(reason)
+  await new Promise<void>((resolve) => setImmediate(resolve))
+})

src/shared/abort-signal-reason.ts

@@ -16,6 +16,8 @@ export function waitForPromiseWithSignal<T>(promise: Promise<T>, signal?: AbortS
     return promise
   }
   if (signal.aborted) {
+    // Observe abandoned work so its later rejection stays handled.
+    void promise.catch(() => undefined)
     return Promise.reject(abortSignalReason(signal))
   }
   return new Promise<T>((resolve, reject) => {

src/shared/git-fork-sync.test.ts

@@ -16,6 +16,10 @@ function createRunner(overrides: {
   originExists?: boolean
   upstreamExists?: boolean
   aheadBehind?: string
+  equalTips?: boolean
+  ancestryError?: boolean
+  commitOutput?: string
+  countError?: boolean
 }): { runGit: GitForkSyncRunner; calls: string[][] } {
   const calls: string[][] = []
   const runGit = vi.fn(async (args: string[]) => {
@@ -42,14 +46,22 @@ function createRunner(overrides: {
         throw new Error('missing upstream branch')
       }
       return {
-        stdout: ref.includes('upstream')
-          ? '2222222222222222222222222222222222222222\n'
-          : '1111111111111111111111111111111111111111\n'
+        stdout:
+          overrides.commitOutput ??
+          (ref.includes('upstream') && !overrides.equalTips
+            ? '2222222222222222222222222222222222222222\n'
+            : '1111111111111111111111111111111111111111\n')
       }
     }
     if (args[0] === 'rev-list') {
+      if (overrides.countError) {
+        throw new Error('invalid revision')
+      }
       return { stdout: overrides.aheadBehind ?? '0\t2\n' }
     }
+    if (args[0] === 'merge-base' && overrides.ancestryError) {
+      throw new Error('missing parent object')
+    }
     return { stdout: '' }
   })
   return { runGit, calls }
@@ -106,6 +118,48 @@ describe('syncForkDefaultBranch', () => {
     expect(flattenedCommands(calls)).not.toContain('push origin')
   })
 
+  it('skips history counts for equal verified tips while retaining fetches and ancestry validation', async () => {
+    const { runGit, calls } = createRunner({ equalTips: true })
+
+    await expect(syncForkDefaultBranch(runGit)).resolves.toMatchObject({
+      status: 'up-to-date',
+      ahead: 0,
+      behind: 0
+    })
+    expect(calls.filter((args) => args[0] === 'fetch')).toHaveLength(2)
+    expect(calls.filter((args) => args[0] === 'rev-parse')).toHaveLength(2)
+    expect(calls.some((args) => args[0] === 'rev-list' || args[0] === 'push')).toBe(false)
+    expect(calls).toContainEqual([
+      'merge-base',
+      '--is-ancestor',
+      '1111111111111111111111111111111111111111',
+      '1111111111111111111111111111111111111111'
+    ])
+  })
+
+  it('still blocks equal tips when ancestry cannot be verified', async () => {
+    const { runGit, calls } = createRunner({ equalTips: true, ancestryError: true })
+
+    await expect(syncForkDefaultBranch(runGit)).resolves.toMatchObject({
+      status: 'blocked',
+      reason: 'diverged',
+      ahead: 0,
+      behind: 0
+    })
+    expect(calls.some((args) => args[0] === 'push')).toBe(false)
+  })
+
+  it('keeps the count query error when a wrapper returns identical non-object output', async () => {
+    const { runGit, calls } = createRunner({
+      commitOutput: 'wrapper banner\n',
+      countError: true
+    })
+
+    await expect(syncForkDefaultBranch(runGit)).rejects.toThrow('invalid revision')
+    expect(calls.some((args) => args[0] === 'rev-list')).toBe(true)
+    expect(calls.some((args) => args[0] === 'push')).toBe(false)
+  })
+
   it('scans newline-heavy remote and default-branch output without line-array splitting', async () => {
     const splitSpy = vi.spyOn(String.prototype, 'split')
     const { runGit } = createRunner({

src/shared/git-fork-sync.ts

@@ -278,9 +278,13 @@ export async function syncForkDefaultBranch(
     return { ...resultWithBranch, status: 'blocked', reason: 'missing-origin-branch' }
   }
 
-  const counts = parseAheadBehind(
-    (await runGit(['rev-list', '--left-right', '--count', `${originOid}...${upstreamOid}`])).stdout
-  )
+  const counts =
+    originOid === upstreamOid && /^(?:[0-9a-fA-F]{40}|[0-9a-fA-F]{64})$/.test(originOid)
+      ? { ahead: 0, behind: 0 }
+      : parseAheadBehind(
+          (await runGit(['rev-list', '--left-right', '--count', `${originOid}...${upstreamOid}`]))
+            .stdout
+        )
 
   if (counts.ahead > 0 || !(await isAncestor(runGit, originOid, upstreamOid))) {
     return { ...resultWithBranch, ...counts, status: 'blocked', reason: 'diverged' }