diff --git a/src/main/hook-archive-termination-safety.test.ts b/src/main/hook-archive-termination-safety.test.ts
new file mode 100644
index 00000000000..7627c7e84fc
--- /dev/null
+++ b/src/main/hook-archive-termination-safety.test.ts
@@ -0,0 +1,103 @@
+import { describe, expect, it, vi } from 'vitest'
+import { mkdtempSync, rmSync, writeFileSync } from 'node:fs'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import type { Repo } from '../shared/repo-types'
+
+vi.mock('./effective-hook-config', () => ({
+  getEffectiveHooksFromConfig: (_repo: unknown, hooks: unknown) => hooks
+}))
+
+const REPO: Repo = { id: 'r', path: '/repo', displayName: 'r', badgeColor: '#000', addedAt: 0 }
+
+/**
+ * Run a hook past its deadline with `process.kill` intercepted, so the escalation's decisions are
+ * observed directly instead of raced against the kernel. `groupAlive` answers the signal-0 probe.
+ */
+async function signalsFromTimedOutHook(groupAlive: boolean): Promise<string[]> {
+  const { runHook } = await import('./hooks')
+  const dir = mkdtempSync(join(tmpdir(), 'orca-hook-signals-'))
+  writeFileSync(join(dir, 'orca.yaml'), 'scripts:\n  archive: |\n    sleep 30\n')
+  const sent: string[] = []
+  const fakeKill = (pid: number, signal?: string | number): true => {
+    if (signal === 0) {
+      if (!groupAlive) {
+        throw Object.assign(new Error('ESRCH'), { code: 'ESRCH' })
+      }
+      return true
+    }
+    sent.push(`${pid < 0 ? 'group' : 'child'}:${String(signal)}`)
+    return true
+  }
+  const spy = vi.spyOn(process, 'kill').mockImplementation(fakeKill)
+  try {
+    await runHook('archive', dir, REPO, dir, undefined, 100)
+    await new Promise((resolve) => setTimeout(resolve, 2_400))
+    return sent
+  } finally {
+    spy.mockRestore()
+    rmSync(dir, { recursive: true, force: true })
+  }
+}
+
+// Why (#19334): the escalation exists for descendants that outlive the shell — a setup hook that
+// backgrounds a server typically loses its leader to the first SIGTERM while the server keeps
+// running. Keying the skip on the CHILD's exit would miss exactly that case; the probe asks the
+// GROUP instead. The residual hazard, stated in hooks.ts: a recycled pid answers the probe too.
+describe.skipIf(process.platform === 'win32')('archive hook termination', () => {
+  it('escalates to the group when members survive the first signal', async () => {
+    await expect(signalsFromTimedOutHook(true)).resolves.toEqual(['group:SIGTERM', 'group:SIGKILL'])
+  }, 20_000)
+
+  it('sends nothing once the group is provably empty', async () => {
+    // A group that answers ESRCH has no members left to kill, and its pid may since belong to
+    // someone else — so neither the SIGTERM nor the escalation is delivered.
+    await expect(signalsFromTimedOutHook(false)).resolves.toEqual([])
+  }, 20_000)
+})
+
+// The regression the group probe exists for, pinned directly because it cannot be reproduced
+// through `runHook` with signals intercepted: with `process.kill` mocked nothing actually dies, so
+// the child never reaches the exited state that a child-liveness skip would key on.
+describe.skipIf(process.platform === 'win32')('terminateHookTree', () => {
+  const fakeChild = (exited: boolean) => ({
+    pid: 4242,
+    exitCode: exited ? 0 : null,
+    signalCode: null,
+    kill: vi.fn()
+  })
+
+  it('signals a surviving group even though the shell leader already exited', async () => {
+    const { terminateHookTree } = await import('./hooks')
+    const sent: (string | number | undefined)[][] = []
+    const recordKill = (pid: number, signal?: string | number): true => {
+      if (signal !== 0) {
+        sent.push([pid, signal])
+      }
+      return true
+    }
+    const spy = vi.spyOn(process, 'kill').mockImplementation(recordKill)
+    try {
+      // A hook that backgrounds a server loses its leader to the first SIGTERM; the server lives on.
+      terminateHookTree(fakeChild(true), 'SIGKILL')
+      expect(sent).toEqual([[-4242, 'SIGKILL']])
+    } finally {
+      spy.mockRestore()
+    }
+  })
+
+  it('sends nothing when the group answers ESRCH', async () => {
+    const { terminateHookTree } = await import('./hooks')
+    const child = fakeChild(true)
+    const emptyGroup = (): true => {
+      throw Object.assign(new Error('ESRCH'), { code: 'ESRCH' })
+    }
+    const spy = vi.spyOn(process, 'kill').mockImplementation(emptyGroup)
+    try {
+      terminateHookTree(child, 'SIGKILL')
+      expect(child.kill).not.toHaveBeenCalled()
+    } finally {
+      spy.mockRestore()
+    }
+  })
+})
diff --git a/src/main/hook-archive-timeout-observation.test.ts b/src/main/hook-archive-timeout-observation.test.ts
new file mode 100644
index 00000000000..62f4b17a386
--- /dev/null
+++ b/src/main/hook-archive-timeout-observation.test.ts
@@ -0,0 +1,52 @@
+import { describe, expect, it, vi } from 'vitest'
+import { mkdtempSync, rmSync, writeFileSync } from 'node:fs'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import type { Repo } from '../shared/repo-types'
+
+vi.mock('./effective-hook-config', () => ({
+  getEffectiveHooksFromConfig: (_repo: unknown, hooks: unknown) => hooks
+}))
+
+const REPO: Repo = { id: 'r', path: '/repo', displayName: 'r', badgeColor: '#000', addedAt: 0 }
+
+/** Run a real archive script in a real shell, under a deadline short enough to test. */
+async function runArchive(script: string, timeoutMs = 400) {
+  const { runHook } = await import('./hooks')
+  const dir = mkdtempSync(join(tmpdir(), 'orca-hook-deadline-'))
+  writeFileSync(join(dir, 'orca.yaml'), `scripts:\n  archive: |\n    ${script}\n`)
+  try {
+    return await runHook('archive', dir, REPO, dir, undefined, timeoutMs)
+  } finally {
+    rmSync(dir, { recursive: true, force: true })
+  }
+}
+
+// Why a real shell (#19334): this bug is invisible to a mock. Node's `exec({ timeout })` SIGTERMs
+// the child and reports whatever it chose to do, so a hook that traps SIGTERM and exits 0 came
+// back as a PASS — a hook cut off mid-archive, indistinguishable from one that finished its work.
+describe.skipIf(process.platform === 'win32')('archive hook deadline', () => {
+  it('fails a hook that traps SIGTERM and exits zero, despite its zero exit', async () => {
+    const result = await runArchive("trap 'exit 0' TERM; sleep 30")
+    expect(result.success).toBe(false)
+    // Withheld, so the removal gate reads `unverifiable` rather than a pass.
+    expect(result.exitCode).toBeUndefined()
+    expect(result.output).toContain('timed out')
+  }, 20_000)
+
+  it('settles at the deadline even when the hook refuses to die', async () => {
+    const started = Date.now()
+    const result = await runArchive("trap '' TERM; sleep 30")
+    expect(result.success).toBe(false)
+    // A hook that ignores the signal must not hold a removal open until it finishes.
+    expect(Date.now() - started).toBeLessThan(10_000)
+  }, 20_000)
+
+  it('passes a hook that finishes inside its deadline', async () => {
+    await expect(runArchive('echo archived')).resolves.toMatchObject({ success: true })
+  })
+
+  it('reports an observed non-zero exit as the exit it is', async () => {
+    await expect(runArchive('exit 23')).resolves.toMatchObject({ success: false, exitCode: 23 })
+  })
+})
diff --git a/src/main/hooks-archive-exit-observation.test.ts b/src/main/hooks-archive-exit-observation.test.ts
new file mode 100644
index 00000000000..7773894c4c4
--- /dev/null
+++ b/src/main/hooks-archive-exit-observation.test.ts
@@ -0,0 +1,63 @@
+import { describe, expect, it, vi } from 'vitest'
+import type { Repo } from '../shared/repo-types'
+
+const { execMock } = vi.hoisted(() => ({ execMock: vi.fn() }))
+vi.mock('child_process', () => ({
+  exec: execMock,
+  execFileSync: vi.fn(),
+  execFile: vi.fn(),
+  spawn: vi.fn()
+}))
+vi.mock('./effective-hook-config', () => ({
+  getEffectiveHooksFromConfig: () => ({ scripts: { archive: 'do-the-archive' } })
+}))
+
+const REPO: Repo = { id: 'r', path: '/repo', displayName: 'r', badgeColor: '#000', addedAt: 0 }
+
+const execFailure = (code: unknown): Error => Object.assign(new Error('Command failed'), { code })
+
+/** Drive runHook once with the error object `exec` hands back for a given failure mode. */
+async function runArchiveWith(
+  error: Error | null
+): Promise<{ success: boolean; exitCode?: number }> {
+  const { runHook } = await import('./hooks')
+  execMock.mockImplementationOnce((_script, _opts, cb) => {
+    cb(error, '', '')
+    return { pid: 1234, kill: vi.fn() }
+  })
+  const outcome = await runHook('archive', '/repo/wt', REPO)
+  // Guard against a vacuous pass: if the mock ever stops intercepting, a real shell would run and
+  // this, rather than the subtle assertions below, is what fails.
+  expect(execMock).toHaveBeenCalled()
+  return outcome
+}
+
+// Why (#19334): an ABSENT exitCode is what the removal gate reads as `unverifiable`. The guard is
+// `typeof code === 'number'`, because `exec` reports a spawn failure with a *string* code — a
+// looser null-check would file ENOENT as `exited "ENOENT"`, reading a hook that never ran as one
+// that reported an exit. The timeout arm of the same contract is covered against a real shell in
+// hook-archive-timeout-observation.test.ts.
+describe('archive hook exit observation', () => {
+  it('passes a clean run through without an exit code', async () => {
+    await expect(runArchiveWith(null)).resolves.toEqual({ success: true, output: '' })
+  })
+
+  it.each([
+    ['a non-zero exit', 23],
+    ['a shell command-not-found', 127]
+  ])('reports %s as the observed exit it is', async (_label, code) => {
+    await expect(runArchiveWith(execFailure(code))).resolves.toMatchObject({
+      success: false,
+      exitCode: code
+    })
+  })
+
+  it.each([
+    ['was killed by a signal', null],
+    ['never started, so the code is a string', 'ENOENT']
+  ])('withholds the exit code when the hook %s', async (_label, code) => {
+    const result = await runArchiveWith(execFailure(code))
+    expect(result.success).toBe(false)
+    expect(result.exitCode).toBeUndefined()
+  })
+})
diff --git a/src/main/hooks.ts b/src/main/hooks.ts
index ef65fc28cf0..f9d91f38423 100644
--- a/src/main/hooks.ts
+++ b/src/main/hooks.ts
@@ -1,6 +1,5 @@
 import { readFileSync, existsSync } from 'node:fs'
 import { join } from 'node:path'
-import { exec } from 'node:child_process'
 import { parseOrcaYaml } from '../shared/orca-yaml'
 import { resolveHookCommandSourcePolicy } from '../shared/hook-command-source-policy'
 import { getEffectiveHooksFromConfig } from './effective-hook-config'
@@ -15,9 +14,114 @@ import type { HookRuntimeTarget } from './hook-runtime-target'
 import type { OrcaHooks } from '../shared/orca-yaml-hook-types'
 import type { Repo } from '../shared/repo-types'
 import type { ProjectExecutionRuntimeResolution } from '../shared/project-execution-runtime'
+import { exec } from 'node:child_process'
 
 const HOOK_TIMEOUT = 120_000 // 2 minutes
 
+type HookProcessOutcome = { success: boolean; output: string; exitCode?: number }
+
+/**
+ * Turn a finished process into a hook verdict.
+ *
+ * Why `timedOut` decides before `code` (#19334): a hook that traps SIGTERM and exits 0 reports a
+ * zero exit for a run we cut off mid-archive. The exit code of something we stopped is not
+ * evidence it finished, so a timeout withholds the code and the removal gate reads that as
+ * `unverifiable` rather than as a pass.
+ */
+function classifyHookProcessResult(
+  result: { code: number | null; stdout: string; stderr: string; timedOut: boolean },
+  context: { hookName: string; cwd: string; timeoutMs: number }
+): HookProcessOutcome {
+  const streams = `${result.stdout}\n${result.stderr}`
+  if (result.timedOut) {
+    const message = `Hook timed out after ${context.timeoutMs}ms.`
+    console.error(`[hooks] ${context.hookName} hook failed in ${context.cwd}:`, message)
+    return { success: false, output: `${streams}\n${message}`.trim() }
+  }
+  if (result.code !== 0) {
+    const message = `Command failed with exit code ${result.code}.`
+    console.error(`[hooks] ${context.hookName} hook failed in ${context.cwd}:`, message)
+    return {
+      success: false,
+      output: `${streams}\n${message}`.trim(),
+      ...(typeof result.code === 'number' ? { exitCode: result.code } : {})
+    }
+  }
+  console.log(`[hooks] ${context.hookName} hook completed in ${context.cwd}`)
+  return { success: true, output: streams.trim() }
+}
+
+const SIGTERM_GRACE_MS = 2_000
+
+/** Signal the hook's whole process group where the platform has one, else just the child. */
+export type TerminableChild = {
+  pid?: number
+  exitCode: number | null
+  signalCode: NodeJS.Signals | null
+  kill: (signal: NodeJS.Signals) => boolean
+}
+
+export function terminateHookTree(child: TerminableChild, signal: NodeJS.Signals): void {
+  // Why probe the GROUP and not the child: the escalation exists for descendants that outlive the
+  // shell. A hook that backgrounds a server typically loses its leader to the first SIGTERM while
+  // the server keeps running, so keying this on `child.exitCode` would skip the SIGKILL in exactly
+  // the case it was added for.
+  //
+  // The trade-off it does not solve: signalling by negative pid names whatever group owns that pid
+  // now. Once the leader is reaped its pid can be recycled, and a probe cannot tell a surviving
+  // descendant from a stranger that inherited the number. Killing a runaway hook is the likelier
+  // event and the one the deadline promises, so the group is signalled whenever it answers; the
+  // residual window is pid wraparound inside the two-second grace.
+  if (process.platform !== 'win32' && child.pid) {
+    try {
+      // Signal 0 tests for members without delivering anything: ESRCH means the group is empty.
+      process.kill(-child.pid, 0)
+    } catch {
+      return
+    }
+    try {
+      process.kill(-child.pid, signal)
+      return
+    } catch {
+      // Raced with the last member exiting; fall through to the direct kill.
+    }
+  }
+  if (child.exitCode !== null || child.signalCode !== null) {
+    return
+  }
+  try {
+    child.kill(signal)
+  } catch {
+    // Already dead.
+  }
+}
+
+/** An `exec` failure: a string `code` (ENOENT) means it never started, so no exit was observed. */
+function hookProcessError(
+  error: Error,
+  stdout: string,
+  stderr: string,
+  context: { hookName: string; cwd: string }
+): HookProcessOutcome {
+  const code = 'code' in error ? error.code : undefined
+  console.error(`[hooks] ${context.hookName} hook failed in ${context.cwd}:`, error.message)
+  return {
+    success: false,
+    output: `${stdout}\n${stderr}\n${error.message}`.trim(),
+    ...(typeof code === 'number' ? { exitCode: code } : {})
+  }
+}
+
+/** A hook that never started reported no exit, so the code stays withheld. */
+function hookSpawnFailure(
+  error: unknown,
+  context: { hookName: string; cwd: string }
+): HookProcessOutcome {
+  const message = error instanceof Error ? error.message : String(error)
+  console.error(`[hooks] ${context.hookName} hook failed in ${context.cwd}:`, message)
+  return { success: false, output: message }
+}
+
 function getHookShell(): string | undefined {
   if (process.platform === 'win32') {
     return process.env.ComSpec || 'cmd.exe'
@@ -120,8 +224,12 @@ export function runHook(
   cwd: string,
   repo: Repo,
   hooksPath?: string,
-  projectRuntime?: ProjectExecutionRuntimeResolution | HookRuntimeTarget
-): Promise<{ success: boolean; output: string }> {
+  projectRuntime?: ProjectExecutionRuntimeResolution | HookRuntimeTarget,
+  /** Deadline override. Production uses HOOK_TIMEOUT; tests use it to exercise the timeout path. */
+  timeoutMs: number = HOOK_TIMEOUT
+  // Why (#19334): an absent exitCode means no exit was ever observed. The archive-hook removal
+  // gate reads that as `unverifiable` rather than folding it into a zero.
+): Promise<{ success: boolean; output: string; exitCode?: number }> {
   const hooks = getEffectiveHooks(repo, hooksPath)
   const script = hooks?.scripts[hookName]
 
@@ -165,57 +273,71 @@ export function runHook(
       shell: 'bash',
       cwd: wslInfo.linuxPath,
       env: guestEnv,
-      timeoutMs: HOOK_TIMEOUT
+      timeoutMs
     })
-      .then((result) => {
-        if (result.timedOut) {
-          const message = `Hook timed out after ${HOOK_TIMEOUT}ms.`
-          console.error(`[hooks] ${hookName} hook failed in ${cwd}:`, message)
-          return { success: false, output: `${result.stdout}\n${result.stderr}\n${message}`.trim() }
-        }
-        if (result.code !== 0) {
-          const message = `Command failed with exit code ${result.code}.`
-          console.error(`[hooks] ${hookName} hook failed in ${cwd}:`, message)
-          return { success: false, output: `${result.stdout}\n${result.stderr}\n${message}`.trim() }
-        }
-        console.log(`[hooks] ${hookName} hook completed in ${cwd}`)
-        return { success: true, output: `${result.stdout}\n${result.stderr}`.trim() }
-      })
-      .catch((error: unknown) => {
-        const message = error instanceof Error ? error.message : String(error)
-        console.error(`[hooks] ${hookName} hook failed in ${cwd}:`, message)
-        return { success: false, output: message }
-      })
+      .then((result) => classifyHookProcessResult(result, { hookName, cwd, timeoutMs }))
+      .catch((error: unknown) => hookSpawnFailure(error, { hookName, cwd }))
   }
 
   const shellHookEnv: NodeJS.ProcessEnv = { ...process.env, ...getSetupEnvVars(repo, cwd) }
   dropIncoherentCondaActivationEnv(shellHookEnv)
 
-  return new Promise((resolve) => {
-    exec(
+  return new Promise<HookProcessOutcome>((resolve) => {
+    // Why we own the deadline (#19334): Node's `exec({ timeout })` SIGTERMs the child and then
+    // reports whatever it chose to do, so a hook that traps SIGTERM and exits 0 came back as a
+    // PASS — a hook cut off mid-archive, indistinguishable from one that finished. Settle on the
+    // deadline instead, and settle AT it, so a hook that traps and keeps running cannot hold a
+    // removal open. `exec` stays because it owns the per-platform shell invocation (`cmd.exe`
+    // wants `/d /s /c`, not `-c`), which is not this change's to re-derive.
+    let settled = false
+    let deadline: NodeJS.Timeout | undefined
+    const settle = (result: HookProcessOutcome): void => {
+      if (settled) {
+        return
+      }
+      settled = true
+      if (deadline) {
+        clearTimeout(deadline)
+      }
+      resolve(result)
+    }
+    const child = exec(
       script,
       {
         cwd,
-        timeout: HOOK_TIMEOUT,
         shell: getHookShell(),
         // Why: hooks run unattended; block Git Credential Manager's interactive prompt while keeping cached auth (issue #7652).
-        env: promptGuardShellEnv(shellHookEnv)
+        env: promptGuardShellEnv(shellHookEnv),
+        // Signal the whole group on POSIX: the script is a shell, and the work is its children.
+        ...(process.platform === 'win32' ? {} : { detached: true })
       },
       (error, stdout, stderr) => {
         if (error) {
-          console.error(`[hooks] ${hookName} hook failed in ${cwd}:`, error.message)
-          resolve({
-            success: false,
-            output: `${stdout}\n${stderr}\n${error.message}`.trim()
-          })
-        } else {
-          console.log(`[hooks] ${hookName} hook completed in ${cwd}`)
-          resolve({
-            success: true,
-            output: `${stdout}\n${stderr}`.trim()
-          })
+          settle(hookProcessError(error, stdout, stderr, { hookName, cwd }))
+          return
         }
+        settle(
+          classifyHookProcessResult(
+            { code: 0, stdout, stderr, timedOut: false },
+            { hookName, cwd, timeoutMs }
+          )
+        )
       }
     )
+    // Why guarded: `exec`'s callback can fire synchronously (the unit test's mock does), and arming
+    // a deadline on an already-settled run would later signal a process group whose pid is long
+    // gone — and may by then belong to something else.
+    if (!settled) {
+      deadline = setTimeout(() => {
+        settle(
+          classifyHookProcessResult(
+            { code: null, stdout: '', stderr: '', timedOut: true },
+            { hookName, cwd, timeoutMs }
+          )
+        )
+        terminateHookTree(child, 'SIGTERM')
+        setTimeout(() => terminateHookTree(child, 'SIGKILL'), SIGTERM_GRACE_MS).unref?.()
+      }, timeoutMs)
+    }
   })
 }