diff --git a/src/main/daemon/pty-subprocess-spawn-file-foreground.test.ts b/src/main/daemon/pty-subprocess-spawn-file-foreground.test.ts
index 8a373616d81..35f330078cc 100644
--- a/src/main/daemon/pty-subprocess-spawn-file-foreground.test.ts
+++ b/src/main/daemon/pty-subprocess-spawn-file-foreground.test.ts
@@ -3,6 +3,7 @@ import { afterEach, describe, expect, it, vi } from 'vitest'
 import type { ProcessTableRow } from '../../shared/process-table-snapshot'
 import type * as SnapshotReader from '../../shared/process-table-snapshot-reader'
 import { createDaemonPtySubprocessHandle } from './pty-subprocess/subprocess-handle'
+import { inspectSpawnFileChildProcessesFromRows } from './pty-subprocess/spawn-file-child-processes'
 import { resolveSpawnFileForegroundFromRows } from './pty-subprocess/spawn-file-foreground-process'
 import { inspectTerminalHostProcess } from './terminal-host-process-inspection'
 import { Session } from './session'
@@ -226,6 +227,35 @@ it('ignores stopped/background children and another terminal beneath the same ro
   })
 })
 
+// ps spells "no controlling terminal" as `?` on Linux, `??` on macOS and `-` on some builds.
+describe.each(['??', '?', '-'] as const)('root on no controlling terminal (tty=%s)', (tty) => {
+  const detachedRoot: ProcessTableRow = {
+    pid: 100,
+    ppid: 1,
+    pgid: 100,
+    tpgid: 100,
+    tty,
+    startTime: 'Sat Sep 26 13:44:29 2026',
+    stat: 'S',
+    command: '/bin/zsh'
+  }
+  const detachedTree: ProcessTableRow[] = [
+    detachedRoot,
+    { ...detachedRoot, pid: 101, ppid: 100, pgid: 100, command: 'claude' }
+  ]
+
+  it('declines to name the descendant that shares the group but holds no terminal', () => {
+    expect(resolveSpawnFileForegroundFromRows(detachedTree, 100)).toEqual({
+      available: false,
+      processName: null
+    })
+  })
+
+  it('reports child evidence as unverifiable rather than reading an unfenceable table', () => {
+    expect(inspectSpawnFileChildProcessesFromRows(detachedTree, 100, 'zsh')).toBe('unverifiable')
+  })
+})
+
 it('uses Windows job membership and the native process table for ordinary children', async () => {
   vi.spyOn(process, 'platform', 'get').mockReturnValue('win32')
   resolveWindows.mockResolvedValue({ available: true, processName: null })
diff --git a/src/main/daemon/pty-subprocess/spawn-file-child-processes.ts b/src/main/daemon/pty-subprocess/spawn-file-child-processes.ts
index c07e3f77e7a..76d7767b56b 100644
--- a/src/main/daemon/pty-subprocess/spawn-file-child-processes.ts
+++ b/src/main/daemon/pty-subprocess/spawn-file-child-processes.ts
@@ -7,6 +7,7 @@ import {
   collectDescendantsFromIndex,
   getProcessTableIndex
 } from '../../../shared/process-table-index'
+import { hasControllingTty } from '../../../shared/posix-controlling-terminal'
 import type { ProcessTableRow } from '../../../shared/process-table-snapshot'
 import type { PtyChildProcessVerdict } from '../../../shared/terminal-process-inspection'
 import { readWindowsPtyJobProcessIds } from '../../providers/windows-pty-job-membership'
@@ -29,7 +30,7 @@ export function inspectSpawnFileChildProcessesFromRows(
 ): PtyChildProcessVerdict {
   const index = getProcessTableIndex(rows)
   const root = index.byPid.get(rootPid)
-  if (!root || !shellName || !root.tty || root.tty === '?') {
+  if (!root || !shellName || !hasControllingTty(root.tty)) {
     return 'unverifiable'
   }
   const tree = [{ ...root, depth: 0 }, ...collectDescendantsFromIndex(index, rootPid)]
diff --git a/src/main/daemon/pty-subprocess/spawn-file-foreground-process.ts b/src/main/daemon/pty-subprocess/spawn-file-foreground-process.ts
index b5763f238b1..46c2d5f4696 100644
--- a/src/main/daemon/pty-subprocess/spawn-file-foreground-process.ts
+++ b/src/main/daemon/pty-subprocess/spawn-file-foreground-process.ts
@@ -8,6 +8,7 @@ import {
   collectDescendantsFromIndex,
   getProcessTableIndex
 } from '../../../shared/process-table-index'
+import { hasControllingTty } from '../../../shared/posix-controlling-terminal'
 import type { ProcessTableRow } from '../../../shared/process-table-snapshot'
 import {
   getFreshProcessTableSnapshot,
@@ -52,7 +53,7 @@ export function resolveSpawnFileForegroundFromRows(
 ): AgentForegroundProcessResolution {
   const index = getProcessTableIndex(rows)
   const root = index.byPid.get(rootPid)
-  if (!root || !root.tpgid || root.tpgid < 0 || !root.tty || root.tty === '?') {
+  if (!root || !root.tpgid || root.tpgid < 0 || !hasControllingTty(root.tty)) {
     return { available: false, processName: null }
   }
   const tree = [{ ...root, depth: 0 }, ...collectDescendantsFromIndex(index, rootPid)]
diff --git a/src/shared/tmux-client-attachment.ts b/src/shared/tmux-client-attachment.ts
index 6184ebfc247..653994f618b 100644
--- a/src/shared/tmux-client-attachment.ts
+++ b/src/shared/tmux-client-attachment.ts
@@ -1,3 +1,4 @@
+import { hasControllingTty } from './posix-controlling-terminal'
 import type { ProcessTableRow } from './process-table-snapshot'
 
 export type TmuxHookPane = { socket: string; pane: string }
@@ -51,7 +52,7 @@ export function resolveTmuxClientAttachment(
 ): TmuxAttachedClient | null {
   const byPid = new Map(rows.map((row) => [row.pid, row]))
   const root = byPid.get(rootPid)
-  if (!root?.startTime || !root.tty || root.tty === '?' || !root.tpgid || root.tpgid <= 0) {
+  if (!root?.startTime || !hasControllingTty(root.tty) || !root.tpgid || root.tpgid <= 0) {
     return null
   }
   const attached = clients.filter((client) => {