fix(bg): identify sessions with persisted process markers (#2163)

src/cli/bg.test.ts

@@ -6,6 +6,7 @@ import { describe, expect, it } from 'bun:test'
 import {
   buildBackgroundSessionLaunch,
   buildBackgroundChildProcessConfig,
+  buildBackgroundSessionDisplayCommand,
   confirmBackgroundSessionLaunch,
   followLogFile,
   killBackgroundSession,
@@ -20,11 +21,19 @@ import {
   BACKGROUND_SESSION_ID_ENV,
   BACKGROUND_SESSION_LAUNCHER_PID_ENV,
 } from './bgFinalizer.js'
+import {
+  BACKGROUND_PROCESS_MARKER_FLAG,
+  backgroundProcessMarkerToken,
+  generateBackgroundProcessMarker,
+} from './bgRouting.js'
 import type {
   BackgroundSession,
   BackgroundSessionProcessIdentity,
 } from './bgRegistry.js'
 
+const TEST_PROCESS_MARKER = 'a'.repeat(64)
+const OTHER_PROCESS_MARKER = 'b'.repeat(64)
+
 class TestOutput extends EventEmitter {
   chunks: Buffer[] = []
   destroyed = false
@@ -98,6 +107,57 @@ async function withTempFile<T>(
 }
 
 describe('background session CLI parsing', () => {
+  it('generates a fresh bounded lower-case hex marker from 32 random bytes', () => {
+    const first = generateBackgroundProcessMarker(size => {
+      expect(size).toBe(32)
+      return new Uint8Array(size).fill(0x11)
+    })
+    const second = generateBackgroundProcessMarker(size =>
+      new Uint8Array(size).fill(0x22),
+    )
+
+    expect(first).toBe('11'.repeat(32))
+    expect(second).toBe('22'.repeat(32))
+    expect(second).not.toBe(first)
+  })
+
+  it('strips inherited marker options before -- but preserves prompt text after it', () => {
+    const inline = backgroundProcessMarkerToken(TEST_PROCESS_MARKER)
+    for (const inherited of [
+      [inline],
+      [BACKGROUND_PROCESS_MARKER_FLAG, TEST_PROCESS_MARKER],
+    ]) {
+      const parsed = parseBackgroundInvocation([
+        '--bg',
+        ...inherited,
+        '--print',
+        '--',
+        inline,
+      ])
+
+      expect(parsed.prompt).toBe(inline)
+      expect(parsed.childArgs).toEqual(['--print', '--', inline])
+    }
+  })
+
+  it('preserves marker-looking required-option values', () => {
+    const markerLookingValue = backgroundProcessMarkerToken(TEST_PROCESS_MARKER)
+    const parsed = parseBackgroundInvocation([
+      '--bg',
+      '--system-prompt',
+      markerLookingValue,
+      'actual prompt',
+    ])
+
+    expect(parsed.prompt).toBe('actual prompt')
+    expect(parsed.childArgs).toEqual([
+      '--system-prompt',
+      markerLookingValue,
+      '--print',
+      'actual prompt',
+    ])
+  })
+
   it('builds a print-mode child command and preserves provider/model flags', () => {
     const parsed = parseBackgroundInvocation([
       '--provider',
@@ -471,6 +531,7 @@ describe('background session CLI parsing', () => {
       sessionName: 'tests',
       stdoutLogPath: '/tmp/bg.out.log',
       backgroundSessionId: 'bg-tests',
+      processMarker: TEST_PROCESS_MARKER,
       launcherPid: 700,
     })
 
@@ -479,6 +540,7 @@ describe('background session CLI parsing', () => {
       '--max-old-space-size=8192',
       '--expose-gc',
       '/repo/bin/openclaude',
+      backgroundProcessMarkerToken(TEST_PROCESS_MARKER),
       '--print',
       'fix failing tests',
     ])
@@ -503,6 +565,7 @@ describe('background session CLI parsing', () => {
       },
       stdoutLogPath: '/tmp/bg.out.log',
       backgroundSessionId: 'bg-no-wrapper',
+      processMarker: TEST_PROCESS_MARKER,
       launcherPid: 701,
     })
 
@@ -522,6 +585,7 @@ describe('background session CLI parsing', () => {
       processEnv: {},
       stdoutLogPath: '/tmp/bg.out.log',
       backgroundSessionId: 'bg-bun-owner',
+      processMarker: TEST_PROCESS_MARKER,
       launcherPid: 702,
     })
 
@@ -531,6 +595,107 @@ describe('background session CLI parsing', () => {
     expect(config.env[BACKGROUND_SESSION_LAUNCHER_PID_ENV]).toBe('702')
   })
 
+  it('injects one fresh marker immediately after a spaced entrypoint', () => {
+    const inherited = backgroundProcessMarkerToken(OTHER_PROCESS_MARKER)
+    const promptMarker = backgroundProcessMarkerToken(OTHER_PROCESS_MARKER)
+    const config = buildBackgroundChildProcessConfig({
+      execPath: 'C:\\Program Files\\nodejs\\node.exe',
+      execArgv: ['--expose-gc'],
+      entrypoint: 'C:\\repo path\\dist\\cli.mjs',
+      childArgs: [
+        inherited,
+        '--provider',
+        'openai',
+        '--model',
+        'gpt-5',
+        '--session-id',
+        '550e8400-e29b-41d4-a716-446655440000',
+        '--from-pr',
+        '1642',
+        '--print',
+        '--',
+        promptMarker,
+      ],
+      processEnv: {},
+      stdoutLogPath: 'C:\\logs path\\bg.out.log',
+      backgroundSessionId: 'bg-spaced-paths',
+      processMarker: TEST_PROCESS_MARKER,
+      launcherPid: 703,
+    })
+    const markerToken = backgroundProcessMarkerToken(TEST_PROCESS_MARKER)
+    const entrypointIndex = config.args.indexOf('C:\\repo path\\dist\\cli.mjs')
+
+    expect(config.args[entrypointIndex + 1]).toBe(markerToken)
+    expect(config.args.filter(arg => arg === markerToken)).toHaveLength(1)
+    expect(config.args.slice(0, config.args.indexOf('--'))).not.toContain(
+      inherited,
+    )
+    expect(config.args.slice(config.args.indexOf('--'))).toEqual([
+      '--',
+      promptMarker,
+    ])
+  })
+
+  it('keeps marker-looking required-option values during defensive injection', () => {
+    const markerLookingValue = backgroundProcessMarkerToken(OTHER_PROCESS_MARKER)
+    const config = buildBackgroundChildProcessConfig({
+      execPath: '/usr/bin/node',
+      execArgv: [],
+      entrypoint: '/repo/bin/openclaude',
+      childArgs: [
+        '--system-prompt',
+        markerLookingValue,
+        '--print',
+        'work',
+      ],
+      processEnv: {},
+      stdoutLogPath: '/tmp/bg.out.log',
+      backgroundSessionId: 'bg-marker-looking-value',
+      processMarker: TEST_PROCESS_MARKER,
+      launcherPid: 704,
+    })
+
+    expect(config.args).toEqual([
+      '--max-old-space-size=8192',
+      '--expose-gc',
+      '/repo/bin/openclaude',
+      backgroundProcessMarkerToken(TEST_PROCESS_MARKER),
+      '--system-prompt',
+      markerLookingValue,
+      '--print',
+      'work',
+    ])
+  })
+
+  it('omits only the internal marker from the displayed launch command', () => {
+    const markerToken = backgroundProcessMarkerToken(TEST_PROCESS_MARKER)
+    const promptMarker = backgroundProcessMarkerToken(OTHER_PROCESS_MARKER)
+
+    expect(
+      buildBackgroundSessionDisplayCommand(
+        [
+          'node',
+          '/repo path/dist/cli.mjs',
+          markerToken,
+          '--provider',
+          'openai',
+          '--print',
+          '--',
+          promptMarker,
+        ],
+        TEST_PROCESS_MARKER,
+      ),
+    ).toEqual([
+      'node',
+      '/repo path/dist/cli.mjs',
+      '--provider',
+      'openai',
+      '--print',
+      '--',
+      promptMarker,
+    ])
+  })
+
   it('escalates process-tree termination and waits for exit before returning', async () => {
     const signals: Array<string | number | undefined> = []
     let aliveChecks = 0
@@ -679,6 +844,17 @@ describe('background session process termination safety', () => {
     stdoutLogPath: '/tmp/stdout.log',
     stderrLogPath: '/tmp/stderr.log',
   }
+  const markedSession: BackgroundSession = {
+    ...session,
+    processMarker: TEST_PROCESS_MARKER,
+    command: [
+      'node',
+      'openclaude',
+      backgroundProcessMarkerToken(TEST_PROCESS_MARKER),
+      '--session-id',
+      'conversation-safety',
+    ],
+  }
 
   function identity(
     state: BackgroundSessionProcessIdentity['state'],
@@ -716,6 +892,30 @@ describe('background session process termination safety', () => {
     ])
   })
 
+  it('signals a marked session only after its exact token is freshly verified', async () => {
+    const calls: string[] = []
+    let aliveChecks = 0
+
+    await terminateBackgroundSessionProcessTree(markedSession, {
+      isProcessAlive: () => ++aliveChecks <= 2,
+      getProcessCommand: pid => {
+        calls.push(`verify:${pid}`)
+        return `node openclaude ${backgroundProcessMarkerToken(TEST_PROCESS_MARKER)} --session-id conversation-safety`
+      },
+      killTree: async (pid, signal) => {
+        calls.push(`signal:${pid}:${signal}`)
+      },
+      sleep: async () => {},
+      termGraceMs: 1,
+      pollIntervalMs: 1,
+    })
+
+    expect(calls).toEqual([
+      'verify:4242',
+      'signal:4242:SIGTERM',
+    ])
+  })
+
   it('refuses a mismatched identity before SIGTERM and does not mark killed', async () => {
     const calls: string[] = []
 
@@ -744,12 +944,37 @@ describe('background session process termination safety', () => {
     }
 
     expect(String(refusal)).toContain('refused to signal an unverified process')
+    expect(String(refusal)).toContain(
+      'This older background session could not be verified safely',
+    )
+    expect(String(refusal)).toContain('terminate PID 4242 manually')
     expect(String(refusal)).not.toContain('private prompt value')
     expect(calls).toEqual([])
   })
 
-  it('does not verify or signal terminal records when a reused PID would match', async () => {
+  it('does not signal or mark a marked session whose token mismatches', async () => {
-    for (const status of ['stale', 'killed', 'exited', 'failed'] as const) {
+    const calls: string[] = []
+
+    await expect(
+      killBackgroundSession(markedSession, {
+        isProcessAlive: () => true,
+        getProcessCommand: () =>
+          `node openclaude ${backgroundProcessMarkerToken(OTHER_PROCESS_MARKER)} --session-id conversation-safety`,
+        killTree: async (_pid, signal) => {
+          calls.push(`signal:${signal}`)
+        },
+        markKilled: async selected => {
+          calls.push(`mark:${selected.id}`)
+          return { ...selected, status: 'killed' }
+        },
+      }),
+    ).rejects.toThrow('refused to signal an unverified process')
+
+    expect(calls).toEqual([])
+  })
+
+  it('does not verify or signal authoritative terminal records when a reused PID would match', async () => {
+    for (const status of ['killed', 'exited', 'failed'] as const) {
       const calls: string[] = []
 
       const killed = await killBackgroundSession(
@@ -774,6 +999,110 @@ describe('background session process termination safety', () => {
     }
   })
 
+  it('fails closed instead of marking a stale session whose identity mismatches', async () => {
+    const calls: string[] = []
+
+    await expect(
+      killBackgroundSession(
+        { ...markedSession, status: 'stale' },
+        {
+          isProcessAlive: () => true,
+          getProcessCommand: () =>
+            `node openclaude ${backgroundProcessMarkerToken(OTHER_PROCESS_MARKER)} --session-id conversation-safety`,
+          killTree: async (_pid, signal) => {
+            calls.push(`signal:${signal}`)
+          },
+          markKilled: async selected => {
+            calls.push(`mark:${selected.id}`)
+            return { ...selected, status: 'killed' }
+          },
+        },
+      ),
+    ).rejects.toThrow('refused to signal an unverified process')
+
+    expect(calls).toEqual([])
+  })
+
+  it('refuses a matching legacy identity after the session was already stale', async () => {
+    const calls: string[] = []
+
+    await expect(
+      killBackgroundSession(
+        { ...session, status: 'stale' },
+        {
+          isProcessAlive: () => true,
+          getProcessCommand: () =>
+            'node openclaude --resume conversation-safety',
+          killTree: async (_pid, signal) => {
+            calls.push(`signal:${signal}`)
+          },
+          markKilled: async selected => {
+            calls.push(`mark:${selected.id}`)
+            return { ...selected, status: 'killed' }
+          },
+        },
+      ),
+    ).rejects.toThrow('PID ownership cannot be re-established safely')
+
+    expect(calls).toEqual([])
+  })
+
+  it('allows an exact marked identity to authorize a previously stale session', async () => {
+    const calls: string[] = []
+    const states: BackgroundSessionProcessIdentity['state'][] = [
+      'matches',
+      'matches',
+    ]
+
+    const killed = await killBackgroundSession(
+      { ...markedSession, status: 'stale' },
+      {
+        isProcessAlive: () => false,
+        verifySessionIdentity: () => {
+          const state = states.shift()!
+          calls.push(`verify:${state}`)
+          return identity(state)
+        },
+        killTree: async (_pid, signal) => {
+          calls.push(`signal:${signal}`)
+        },
+        markKilled: async selected => {
+          calls.push(`mark:${selected.id}`)
+          return { ...selected, status: 'killed' }
+        },
+      },
+    )
+
+    expect(killed.status).toBe('killed')
+    expect(calls).toEqual([
+      'verify:matches',
+      'verify:matches',
+      'signal:SIGTERM',
+      'mark:bg-safety',
+    ])
+  })
+
+  it('marks a stale session killed without signalling when its PID is gone', async () => {
+    const calls: string[] = []
+
+    const killed = await killBackgroundSession(
+      { ...session, status: 'stale' },
+      {
+        isProcessAlive: () => false,
+        killTree: async (_pid, signal) => {
+          calls.push(`signal:${signal}`)
+        },
+        markKilled: async selected => {
+          calls.push(`mark:${selected.id}`)
+          return { ...selected, status: 'killed' }
+        },
+      },
+    )
+
+    expect(killed.status).toBe('killed')
+    expect(calls).toEqual(['mark:bg-safety'])
+  })
+
   it('freshly verifies an unknown session that becomes readable before killing', async () => {
     const calls: string[] = []
     const states: BackgroundSessionProcessIdentity['state'][] = [
@@ -866,6 +1195,39 @@ describe('background session process termination safety', () => {
     ])
   })
 
+  it('does not send SIGKILL when a marked token changes after SIGTERM', async () => {
+    const calls: string[] = []
+    const commands = [
+      `node openclaude ${backgroundProcessMarkerToken(TEST_PROCESS_MARKER)} --session-id conversation-safety`,
+      `node openclaude ${backgroundProcessMarkerToken(OTHER_PROCESS_MARKER)} --session-id conversation-safety`,
+    ]
+
+    await expect(
+      terminateBackgroundSessionProcessTree(markedSession, {
+        isProcessAlive: () => true,
+        getProcessCommand: () => {
+          calls.push('verify')
+          return commands.shift()!
+        },
+        killTree: async (_pid, signal) => {
+          calls.push(`signal:${signal}`)
+        },
+        sleep: async () => {
+          calls.push('sleep')
+        },
+        termGraceMs: 1,
+        pollIntervalMs: 1,
+      }),
+    ).rejects.toThrow('refused to signal an unverified process')
+
+    expect(calls).toEqual([
+      'verify',
+      'signal:SIGTERM',
+      'sleep',
+      'verify',
+    ])
+  })
+
   it('fails closed when the live process identity is unreadable', async () => {
     const signals: Array<string | number> = []
 
@@ -882,6 +1244,26 @@ describe('background session process termination safety', () => {
     expect(signals).toEqual([])
   })
 
+  it('does not mark a marked session killed when identity is unreadable', async () => {
+    const calls: string[] = []
+
+    await expect(
+      killBackgroundSession(markedSession, {
+        isProcessAlive: () => true,
+        getProcessCommand: () => null,
+        killTree: async (_pid, signal) => {
+          calls.push(`signal:${signal}`)
+        },
+        markKilled: async selected => {
+          calls.push(`mark:${selected.id}`)
+          return { ...selected, status: 'killed' }
+        },
+      }),
+    ).rejects.toThrow('refused to signal an unverified process')
+
+    expect(calls).toEqual([])
+  })
+
   it('refuses signalling when liveness becomes unreadable during command lookup', async () => {
     const calls: string[] = []
     let probes = 0

src/cli/bg.ts

@@ -25,8 +25,11 @@ import {
   type BackgroundSessionProcessIdentityOptions,
 } from './bgRegistry.js'
 import {
+  backgroundProcessMarkerToken,
   BACKGROUND_SESSION_ID_ENV,
   BACKGROUND_SESSION_LAUNCHER_PID_ENV,
+  generateBackgroundProcessMarker,
+  stripBackgroundProcessMarkerArgs,
 } from './bgRouting.js'
 
 export type ParsedBackgroundInvocation = {
@@ -56,6 +59,7 @@ export type BuildBackgroundChildProcessConfigInput = {
   sessionName?: string
   stdoutLogPath: string
   backgroundSessionId: string
+  processMarker: string
   launcherPid?: number
 }
 
@@ -233,6 +237,7 @@ export function buildBackgroundChildProcessConfig(
   // launcher otherwise relaunches itself before finalizer ownership is checked.
   // Node-only heap flags are still supplied by safeNodeExecArgvForBackground.
   env[HEAP_RELAUNCHED_ENV] = '1'
+  const childArgs = stripBackgroundProcessMarkerArgs(input.childArgs)
 
   return {
     command: input.execPath,
@@ -243,7 +248,8 @@ export function buildBackgroundChildProcessConfig(
         input.processEnv,
       ),
       input.entrypoint,
-      ...input.childArgs,
+      backgroundProcessMarkerToken(input.processMarker),
+      ...childArgs,
     ],
     env,
   }
@@ -432,7 +438,7 @@ export async function buildBackgroundSessionLaunch(
 export function parseBackgroundInvocation(
   args: string[],
 ): ParsedBackgroundInvocation {
-  let childArgs = stripBackgroundFlag(args)
+  let childArgs = stripBackgroundProcessMarkerArgs(stripBackgroundFlag(args))
   const name = findSessionName(childArgs)?.trim() || undefined
   const promptIndex = findPromptIndex(childArgs)
   const prompt = promptIndex === -1 ? undefined : childArgs[promptIndex]
@@ -482,6 +488,21 @@ function formatCommand(command: string[]): string {
     .join(' ')
 }
 
+export function buildBackgroundSessionDisplayCommand(
+  command: string[],
+  processMarker: string,
+): string[] {
+  const markerToken = backgroundProcessMarkerToken(processMarker)
+  const delimiterIndex = command.indexOf('--')
+  const optionEnd = delimiterIndex === -1 ? command.length : delimiterIndex
+  const markerIndex = command.findIndex(
+    (arg, index) => index < optionEnd && arg === markerToken,
+  )
+  return markerIndex === -1
+    ? [...command]
+    : [...command.slice(0, markerIndex), ...command.slice(markerIndex + 1)]
+}
+
 function printSessionTable(
   sessions: Awaited<ReturnType<typeof listBackgroundSessions>>,
 ): void {
@@ -839,8 +860,12 @@ function unverifiedProcessError(
   session: BackgroundSession,
   reason: string,
 ): Error {
+  const action =
+    session.processMarker === undefined
+      ? `This older background session could not be verified safely. Restart it to use stronger process identity, or terminate PID ${session.pid} manually after confirming ownership.`
+      : 'Re-run `openclaude ps` and retry after confirming the session identity.'
   return new Error(
-    `OpenClaude refused to signal an unverified process for background session ${session.id} (PID ${session.pid}): ${reason}. Re-run \`openclaude ps\` and retry after confirming the session identity.`,
+    `OpenClaude refused to signal an unverified process for background session ${session.id} (PID ${session.pid}): ${reason}. ${action}`,
   )
 }
 
@@ -921,10 +946,23 @@ export async function killBackgroundSession(
     (async (selected: BackgroundSession) =>
       await markBackgroundSessionKilled(selected.id))
 
-  if (isTerminalBackgroundSession(session)) return await markKilled(session)
+  if (session.status !== 'stale' && isTerminalBackgroundSession(session)) {
+    return await markKilled(session)
+  }
 
   const identity = verifySelectedBackgroundSessionIdentity(session, options)
-  if (authorizeBackgroundSessionSignal(session, identity) === 'matches') {
+  const authorization = authorizeBackgroundSessionSignal(session, identity)
+  if (
+    authorization === 'matches' &&
+    session.status === 'stale' &&
+    session.processMarker === undefined
+  ) {
+    throw unverifiedProcessError(
+      session,
+      'this older session was already stale, so its PID ownership cannot be re-established safely',
+    )
+  }
+  if (authorization === 'matches') {
     await terminateBackgroundSessionProcessTree(session, options)
   }
 
@@ -1032,6 +1070,7 @@ export async function handleBgFlag(args: string[]): Promise<void> {
   }
 
   const id = backgroundSessionId()
+  const processMarker = generateBackgroundProcessMarker()
   const { childArgs, sessionId } = await buildBackgroundSessionLaunch(
     parsed.childArgs,
     randomUUID(),
@@ -1053,6 +1092,7 @@ export async function handleBgFlag(args: string[]): Promise<void> {
     sessionName: parsed.name,
     stdoutLogPath: logPaths.stdoutLogPath,
     backgroundSessionId: id,
+    processMarker,
     launcherPid: process.pid,
   })
 
@@ -1108,6 +1148,7 @@ export async function handleBgFlag(args: string[]): Promise<void> {
     provider: findFlagValue(childArgs, '--provider'),
     model: findFlagValue(childArgs, '--model'),
     sessionId,
+    processMarker,
     stdoutLogPath: logPaths.stdoutLogPath,
     stderrLogPath: logPaths.stderrLogPath,
     logFilesPrecreated: true,
@@ -1131,6 +1172,11 @@ export async function handleBgFlag(args: string[]): Promise<void> {
   console.log(`Logs: ${session.stdoutLogPath}`)
   console.log(`Follow: openclaude logs ${session.id} -f`)
   console.log(
-    `Command: ${formatCommand([basename(childConfig.command), ...childConfig.args])}`,
+    `Command: ${formatCommand(
+      buildBackgroundSessionDisplayCommand([
+        basename(childConfig.command),
+        ...childConfig.args,
+      ], processMarker),
+    )}`,
   )
 }

src/cli/bgFinalizer.test.ts

@@ -10,10 +10,16 @@ import {
   prepareBackgroundSessionFinalizer,
 } from './bgFinalizer.js'
 import { buildBackgroundChildProcessConfig } from './bg.js'
+import {
+  BACKGROUND_PROCESS_MARKER_FLAG,
+  backgroundProcessMarkerToken,
+  isValidBackgroundProcessMarker,
+} from './bgRouting.js'
 import {
   _setBackgroundSessionsRootForTesting,
   listBackgroundSessions,
   refreshBackgroundSessionStatuses,
+  verifyBackgroundSessionProcessIdentity,
   type BackgroundSession,
 } from './bgRegistry.js'
 
@@ -343,6 +349,7 @@ describe('background session finalizer', () => {
     id: string,
     args: string[],
   ): Promise<number> {
+    const processMarker = 'c'.repeat(64)
     const processEnv: NodeJS.ProcessEnv = {
       ...process.env,
       OPENCLAUDE_CONFIG_DIR: configDir,
@@ -356,6 +363,7 @@ describe('background session finalizer', () => {
       processEnv,
       stdoutLogPath: join(configDir, `${id}.out.log`),
       backgroundSessionId: id,
+      processMarker,
       launcherPid: process.pid,
     })
     const child = spawn(childConfig.command, childConfig.args, {
@@ -367,7 +375,11 @@ describe('background session finalizer', () => {
     await mkdir(join(sessionsRoot, 'sessions'), { recursive: true })
     await writeFile(
       join(sessionsRoot, 'sessions', `${id}.json`),
-      JSON.stringify(ownedSession(id, child.pid)),
+      JSON.stringify({
+        ...ownedSession(id, child.pid),
+        processMarker,
+        command: [childConfig.command, ...childConfig.args],
+      }),
     )
     const [code] = (await once(child, 'exit')) as [number]
     return code
@@ -484,11 +496,73 @@ describe('background session finalizer', () => {
         exitCode: expectation.exitCode,
         terminalReason: 'exit_code',
       })
+      expect(isValidBackgroundProcessMarker(session.processMarker)).toBe(true)
+      expect(session.command).toContain(
+        backgroundProcessMarkerToken(session.processMarker!),
+      )
+      expect(stdout).not.toContain(BACKGROUND_PROCESS_MARKER_FLAG)
       expect(await Bun.file(session.stdoutLogPath).exists()).toBe(true)
       expect(await Bun.file(session.stderrLogPath).exists()).toBe(true)
     })
   }
 
+  it.skipIf(process.platform === 'win32')(
+    'recognizes a live built marked child through the production command probe',
+    async () => {
+      const id = 'bg-built-live-marker'
+      const processMarker = 'e'.repeat(64)
+      const processEnv: NodeJS.ProcessEnv = {
+        ...process.env,
+        OPENCLAUDE_CONFIG_DIR: configDir,
+      }
+      delete processEnv.OPENCLAUDE_DISABLE_CLI_ENTRYPOINT_AUTO_RUN
+      const childConfig = buildBackgroundChildProcessConfig({
+        execPath: 'node',
+        execArgv: [],
+        entrypoint: installedLauncherPath,
+        childArgs: ['--version'],
+        processEnv,
+        stdoutLogPath: join(configDir, `${id}.out.log`),
+        backgroundSessionId: id,
+        processMarker,
+        launcherPid: process.pid,
+      })
+      const child = spawn(childConfig.command, childConfig.args, {
+        env: childConfig.env,
+        stdio: ['ignore', 'ignore', 'ignore'],
+      })
+      if (!child.pid) throw new Error('built CLI fixture did not start')
+      const exit = once(child, 'exit')
+      let forceTimer: ReturnType<typeof setTimeout> | undefined
+
+      try {
+        expect(child.kill('SIGSTOP')).toBe(true)
+        const session: BackgroundSession = {
+          ...ownedSession(id, child.pid),
+          processMarker,
+          command: [childConfig.command, ...childConfig.args],
+        }
+        await mkdir(join(sessionsRoot, 'sessions'), { recursive: true })
+        await writeFile(
+          join(sessionsRoot, 'sessions', `${id}.json`),
+          JSON.stringify(session),
+        )
+
+        expect(verifyBackgroundSessionProcessIdentity(session).state).toBe(
+          'matches',
+        )
+        expect(await refreshBackgroundSessionStatuses()).toMatchObject([
+          { id, status: 'running', processMarker },
+        ])
+      } finally {
+        child.kill('SIGCONT')
+        forceTimer = setTimeout(() => child.kill('SIGKILL'), 5_000)
+        await exit
+        clearTimeout(forceTimer)
+      }
+    },
+  )
+
   it('keeps the installed launcher PID stable and shows outcomes truthfully in ps', async () => {
     expect(await runBuiltCliSession('bg-built-success', ['--version'])).toBe(0)
     expect(
@@ -520,6 +594,12 @@ describe('background session finalizer', () => {
     expect(stderr).toBe('')
     expect(stdout).toMatch(/bg-built-success\s+exited/)
     expect(stdout).toMatch(/bg-built-failure\s+failed/)
+    for (const session of await listBackgroundSessions()) {
+      expect(session.processMarker).toBe('c'.repeat(64))
+      expect(session.command).toContain(
+        backgroundProcessMarkerToken(session.processMarker!),
+      )
+    }
   })
 
   it.skipIf(process.platform === 'win32')(

src/cli/bgRegistry.test.ts

@@ -17,6 +17,15 @@ import {
   type BackgroundSession,
 } from './bgRegistry.js'
 
+const TEST_PROCESS_MARKER = 'a'.repeat(64)
+const OTHER_PROCESS_MARKER = 'b'.repeat(64)
+// Keep this test-only constructor available on the pre-marker base so the
+// marker-authoritative regression can prove red there. Production identity
+// constructs its expected token independently, so token-format drift still
+// fails the marked-match tests below.
+const backgroundProcessMarkerToken = (marker: string) =>
+  `--openclaude-bg-session-marker=${marker}`
+
 const {
   recordBackgroundSessionNaturalTermination,
   recordBackgroundSessionNaturalTerminationSync,
@@ -82,10 +91,16 @@ describe('background session registry', () => {
       name: 'auth-refactor',
       pid: 12345,
       cwd: '/repo',
-      command: ['openclaude', '--print', 'refactor auth'],
+      command: [
+        'openclaude',
+        backgroundProcessMarkerToken(TEST_PROCESS_MARKER),
+        '--print',
+        'refactor auth',
+      ],
       provider: 'openai',
       model: 'gpt-5',
       sessionId: 'conversation-1',
+      processMarker: TEST_PROCESS_MARKER,
       now: new Date('2026-06-15T08:00:00.000Z'),
     })
 
@@ -98,9 +113,15 @@ describe('background session registry', () => {
       provider: 'openai',
       model: 'gpt-5',
       sessionId: 'conversation-1',
+      processMarker: TEST_PROCESS_MARKER,
       startedAt: '2026-06-15T08:00:00.000Z',
       updatedAt: '2026-06-15T08:00:00.000Z',
-      command: ['openclaude', '--print', 'refactor auth'],
+      command: [
+        'openclaude',
+        backgroundProcessMarkerToken(TEST_PROCESS_MARKER),
+        '--print',
+        'refactor auth',
+      ],
     })
     expect(session.stdoutLogPath).toBe(
       join(configDir, 'bg-sessions', 'logs', 'bg-test-1.out.log'),
@@ -111,6 +132,87 @@ describe('background session registry', () => {
 
     const sessions = await listBackgroundSessions()
     expect(sessions.map(s => s.id)).toEqual(['bg-test-1'])
+    expect(sessions[0]?.processMarker).toBe(TEST_PROCESS_MARKER)
+  })
+
+  it('loads legacy session metadata without a process marker', async () => {
+    await mkdir(join(configDir, 'bg-sessions', 'sessions'), {
+      recursive: true,
+    })
+    await writeFile(
+      join(configDir, 'bg-sessions', 'sessions', 'bg-legacy.json'),
+      JSON.stringify({
+        id: 'bg-legacy',
+        pid: 123,
+        cwd: '/repo',
+        status: 'running',
+        sessionId: 'conversation-legacy',
+        startedAt: '2026-06-15T08:00:00.000Z',
+        updatedAt: '2026-06-15T08:00:00.000Z',
+        command: ['openclaude', '--print', 'work'],
+        stdoutLogPath: '/tmp/stdout.log',
+        stderrLogPath: '/tmp/stderr.log',
+      }),
+    )
+
+    const [session] = await listBackgroundSessions()
+    expect(session?.id).toBe('bg-legacy')
+    expect(session?.processMarker).toBeUndefined()
+  })
+
+  it('rejects malformed process markers on creation', async () => {
+    await expect(
+      createBackgroundSession({
+        id: 'bg-invalid-marker',
+        pid: 123,
+        cwd: '/repo',
+        command: ['openclaude', '--print', 'work'],
+        sessionId: 'conversation-invalid-marker',
+        processMarker: 'not-valid',
+      }),
+    ).rejects.toThrow('Invalid background process marker')
+
+    expect(await listBackgroundSessions()).toEqual([])
+  })
+
+  it('ignores metadata containing malformed process markers', async () => {
+    await mkdir(join(configDir, 'bg-sessions', 'sessions'), {
+      recursive: true,
+    })
+    const invalidMarkers = [
+      '',
+      'a'.repeat(63),
+      'a'.repeat(65),
+      'A'.repeat(64),
+      `${'a'.repeat(63)} `,
+      `${'a'.repeat(63)}/`,
+      `${'a'.repeat(63)};`,
+      `${'a'.repeat(63)}\u0000`,
+    ]
+
+    await Promise.all(
+      invalidMarkers.map(async (processMarker, index) => {
+        const id = `bg-invalid-marker-${index}`
+        await writeFile(
+          join(configDir, 'bg-sessions', 'sessions', `${id}.json`),
+          JSON.stringify({
+            id,
+            pid: 123 + index,
+            cwd: '/repo',
+            status: 'running',
+            sessionId: `conversation-${index}`,
+            processMarker,
+            startedAt: '2026-06-15T08:00:00.000Z',
+            updatedAt: '2026-06-15T08:00:00.000Z',
+            command: ['openclaude', '--print', 'work'],
+            stdoutLogPath: '/tmp/stdout.log',
+            stderrLogPath: '/tmp/stderr.log',
+          }),
+        )
+      }),
+    )
+
+    expect(await listBackgroundSessions()).toEqual([])
   })
 
   it('resolves exact live names before session id prefixes', async () => {
@@ -1130,6 +1232,108 @@ describe('background session registry', () => {
     )
   })
 
+  it('keeps a marked Windows session running when its exact early token matches', async () => {
+    const markerToken = backgroundProcessMarkerToken(TEST_PROCESS_MARKER)
+    await createBackgroundSession({
+      id: 'bg-marked-windows',
+      name: 'marked-windows',
+      pid: 333,
+      cwd: 'C:\\repo path',
+      command: [
+        'C:\\Program Files\\nodejs\\node.exe',
+        'C:\\repo path\\dist\\cli.mjs',
+        markerToken,
+        '--session-id',
+        'conversation-marked',
+        '--print',
+        'work',
+      ],
+      sessionId: 'conversation-marked',
+      processMarker: TEST_PROCESS_MARKER,
+      now: new Date('2026-06-15T08:00:00.000Z'),
+    })
+
+    const refreshed = await refreshBackgroundSessionStatuses({
+      isProcessAlive: () => true,
+      getProcessCommand: () =>
+        `"C:\\Program Files\\nodejs\\node.exe" "C:\\repo path\\dist\\cli.mjs" ${markerToken} --session-id conversation-marked --print work`,
+      now: new Date('2026-06-15T08:05:00.000Z'),
+    })
+
+    expect(refreshed[0]).toMatchObject({
+      id: 'bg-marked-windows',
+      status: 'running',
+      updatedAt: '2026-06-15T08:00:00.000Z',
+    })
+    await expect(
+      createBackgroundSession({
+        id: 'bg-marked-windows-contender',
+        name: 'marked-windows',
+        pid: 334,
+        cwd: '/repo',
+        command: ['openclaude', '--print', 'contender'],
+        sessionId: 'conversation-contender',
+      }),
+    ).rejects.toThrow('already exists')
+  })
+
+  it('marks a marked session stale when the same session id has a different marker', async () => {
+    const markerToken = backgroundProcessMarkerToken(TEST_PROCESS_MARKER)
+    await createBackgroundSession({
+      id: 'bg-marked-wrong-marker',
+      pid: 333,
+      cwd: '/repo',
+      command: [
+        'node',
+        '/repo/openclaude',
+        markerToken,
+        '--session-id',
+        'conversation-marked',
+      ],
+      sessionId: 'conversation-marked',
+      processMarker: TEST_PROCESS_MARKER,
+      now: new Date('2026-06-15T08:00:00.000Z'),
+    })
+
+    const refreshed = await refreshBackgroundSessionStatuses({
+      isProcessAlive: () => true,
+      getProcessCommand: () =>
+        `node /repo/openclaude ${backgroundProcessMarkerToken(OTHER_PROCESS_MARKER)} --session-id conversation-marked`,
+      now: new Date('2026-06-15T08:05:00.000Z'),
+    })
+
+    expect(refreshed[0]).toMatchObject({
+      id: 'bg-marked-wrong-marker',
+      status: 'stale',
+      updatedAt: '2026-06-15T08:05:00.000Z',
+    })
+  })
+
+  it('keeps a marked session unknown when its live command is unreadable', async () => {
+    const markerToken = backgroundProcessMarkerToken(TEST_PROCESS_MARKER)
+    await createBackgroundSession({
+      id: 'bg-marked-unreadable',
+      pid: 333,
+      cwd: '/repo',
+      command: ['node', '/repo/openclaude', markerToken, '--print', 'work'],
+      sessionId: 'conversation-marked',
+      processMarker: TEST_PROCESS_MARKER,
+      now: new Date('2026-06-15T08:00:00.000Z'),
+    })
+
+    const refreshed = await refreshBackgroundSessionStatuses({
+      isProcessAlive: () => true,
+      getProcessCommand: () => null,
+      now: new Date('2026-06-15T08:05:00.000Z'),
+    })
+
+    expect(refreshed[0]).toMatchObject({
+      id: 'bg-marked-unreadable',
+      status: 'unknown',
+      updatedAt: '2026-06-15T08:05:00.000Z',
+    })
+  })
+
   it('keeps running sessions fresh when their process identity still matches', async () => {
     await createBackgroundSession({
       id: 'bg-running',
@@ -1331,6 +1535,20 @@ describe('isBackgroundSessionProcessAlive process identity', () => {
     stdoutLogPath: '/tmp/stdout.log',
     stderrLogPath: '/tmp/stderr.log',
   }
+  const markerToken = backgroundProcessMarkerToken(TEST_PROCESS_MARKER)
+  const markedSession: BackgroundSession = {
+    ...session,
+    processMarker: TEST_PROCESS_MARKER,
+    command: [
+      '/opt/Open Claude/node',
+      '/repo path/dist/cli.mjs',
+      markerToken,
+      '--session-id',
+      session.sessionId,
+      '--print',
+      'work',
+    ],
+  }
 
   it('does not treat a reused PID whose command merely contains the arg as alive (#1770)', () => {
     // The live process at this PID is unrelated: its final token "16420" only
@@ -1360,6 +1578,100 @@ describe('isBackgroundSessionProcessAlive process identity', () => {
     expect(alive).toBe(true)
   })
 
+  it('does not fall back to the session id when marked process identity is missing', () => {
+    const result = verifyBackgroundSessionProcessIdentity(markedSession, {
+      isProcessAlive: () => true,
+      getProcessCommand: () =>
+        '/opt/Open Claude/node /repo path/dist/cli.mjs --session-id conversation-identity --print work',
+    })
+
+    expect(result.state).toBe('mismatch')
+  })
+
+  it('matches a marked Unix command with spaced executable and entrypoint paths', () => {
+    const result = verifyBackgroundSessionProcessIdentity(markedSession, {
+      isProcessAlive: () => true,
+      getProcessCommand: () =>
+        `/opt/Open Claude/node /repo path/dist/cli.mjs ${markerToken} --session-id conversation-identity --print work`,
+    })
+
+    expect(result.state).toBe('matches')
+  })
+
+  it('does not accept a missing, wrong, or shifted marker for a marked session', () => {
+    const prefix = '/opt/Open Claude/node /repo path/dist/cli.mjs'
+    const commands = [
+      `${prefix} --print work --session-id conversation-identity`,
+      `${prefix} ${backgroundProcessMarkerToken(OTHER_PROCESS_MARKER)} --session-id conversation-identity --print work`,
+      `${prefix} --print ${markerToken} --session-id conversation-identity work`,
+    ]
+
+    expect(
+      commands.map(
+        command =>
+          verifyBackgroundSessionProcessIdentity(markedSession, {
+            isProcessAlive: () => true,
+            getProcessCommand: () => command,
+          }).state,
+      ),
+    ).toEqual(['mismatch', 'mismatch', 'mismatch'])
+  })
+
+  it('does not match marker prefix, suffix, or prompt-only collisions', () => {
+    const prefix = '/opt/Open Claude/node /repo path/dist/cli.mjs'
+    const commands = [
+      `${prefix} prefix-${markerToken} --session-id conversation-identity`,
+      `${prefix} ${markerToken}-suffix --session-id conversation-identity`,
+      `${prefix} --print -- ${markerToken}`,
+    ]
+
+    expect(
+      commands.map(
+        command =>
+          verifyBackgroundSessionProcessIdentity(markedSession, {
+            isProcessAlive: () => true,
+            getProcessCommand: () => command,
+          }).state,
+      ),
+    ).toEqual(['mismatch', 'mismatch', 'mismatch'])
+  })
+
+  it('distinguishes truncated marked identity from a shorter unrelated command', () => {
+    const prefix = '/opt/Open Claude/node /repo path/dist/cli.mjs'
+    const withinMarker = markerToken.slice(0, -8)
+    const states = [
+      verifyBackgroundSessionProcessIdentity(markedSession, {
+        isProcessAlive: () => true,
+        getProcessCommand: () => prefix,
+      }).state,
+      verifyBackgroundSessionProcessIdentity(markedSession, {
+        isProcessAlive: () => true,
+        getProcessCommand: () => `${prefix} ${withinMarker}`,
+      }).state,
+      verifyBackgroundSessionProcessIdentity(markedSession, {
+        isProcessAlive: () => true,
+        getProcessCommand: () => 'unrelated short command',
+      }).state,
+    ]
+
+    expect(states).toEqual(['unreadable', 'unreadable', 'mismatch'])
+  })
+
+  it('treats a marked session whose stored command omits its marker as unreadable', () => {
+    const result = verifyBackgroundSessionProcessIdentity(
+      {
+        ...markedSession,
+        command: ['node', 'openclaude', '--print', 'work'],
+      },
+      {
+        isProcessAlive: () => true,
+        getProcessCommand: () => 'node openclaude --print work',
+      },
+    )
+
+    expect(result.state).toBe('unreadable')
+  })
+
   it('does not match the session id as a substring of a larger token (#1770)', () => {
     // A short id must not match an unrelated live command that merely contains
     // it inside a longer token — the same reused-PID collision class as the

src/cli/bgRegistry.ts

@@ -27,6 +27,10 @@ import {
   isProcessRunning,
 } from '../utils/genericProcessUtils.js'
 import { jsonParse, jsonStringify } from '../utils/slowOperations.js'
+import {
+  backgroundProcessMarkerToken,
+  isValidBackgroundProcessMarker,
+} from './bgRouting.js'
 
 export type BackgroundSessionStatus =
   | 'running'
@@ -45,6 +49,7 @@ export type BackgroundSession = {
   provider?: string
   model?: string
   sessionId: string
+  processMarker?: string
   startedAt: string
   updatedAt: string
   command: string[]
@@ -85,6 +90,7 @@ export type CreateBackgroundSessionInput = {
   provider?: string
   model?: string
   sessionId: string
+  processMarker?: string
   now?: Date
   stdoutLogPath?: string
   stderrLogPath?: string
@@ -426,6 +432,8 @@ function isBackgroundSession(
       typeof candidate.provider === 'string') &&
     (candidate.model === undefined || typeof candidate.model === 'string') &&
     typeof candidate.sessionId === 'string' &&
+    (candidate.processMarker === undefined ||
+      isValidBackgroundProcessMarker(candidate.processMarker)) &&
     typeof candidate.startedAt === 'string' &&
     typeof candidate.updatedAt === 'string' &&
     isStringArray(candidate.command) &&
@@ -682,6 +690,12 @@ export async function createBackgroundSession(
   if (!Number.isInteger(input.pid) || input.pid <= 0) {
     throw new Error(`Invalid background session pid: ${input.pid}`)
   }
+  if (
+    input.processMarker !== undefined &&
+    !isValidBackgroundProcessMarker(input.processMarker)
+  ) {
+    throw new Error('Invalid background process marker')
+  }
   await assertBackgroundSessionNameAvailable(input.name)
   const timestamp = iso(input.now)
   const logPaths = getBackgroundSessionLogPaths(input.id)
@@ -694,6 +708,9 @@ export async function createBackgroundSession(
     ...(input.provider ? { provider: input.provider } : {}),
     ...(input.model ? { model: input.model } : {}),
     sessionId: input.sessionId,
+    ...(input.processMarker
+      ? { processMarker: input.processMarker }
+      : {}),
     startedAt: timestamp,
     updatedAt: timestamp,
     command: input.command,
@@ -897,6 +914,35 @@ function commandLineMatchesBackgroundSession(
   return commandLineContainsArgs(commandLine, session.command)
 }
 
+function markedCommandLineIdentity(
+  commandLine: string,
+  session: BackgroundSession,
+  processMarker: string,
+): 'matches' | 'mismatch' | 'unreadable' {
+  const markerToken = backgroundProcessMarkerToken(processMarker)
+  const storedTokens = session.command.flatMap(tokenizeCommandLine)
+  const expectedIndex = storedTokens.indexOf(markerToken)
+  if (expectedIndex === -1) return 'unreadable'
+
+  const liveTokens = tokenizeCommandLine(commandLine)
+  const comparablePrefixLength = Math.min(expectedIndex, liveTokens.length)
+  for (let index = 0; index < comparablePrefixLength; index += 1) {
+    if (liveTokens[index] !== storedTokens[index]) return 'mismatch'
+  }
+
+  if (liveTokens.length <= expectedIndex) return 'unreadable'
+  const candidate = liveTokens[expectedIndex]!
+  if (candidate === markerToken) return 'matches'
+  if (
+    expectedIndex === liveTokens.length - 1 &&
+    candidate.length > 0 &&
+    markerToken.startsWith(candidate)
+  ) {
+    return 'unreadable'
+  }
+  return 'mismatch'
+}
+
 export function verifyBackgroundSessionProcessIdentity(
   session: BackgroundSession,
   options?: BackgroundSessionProcessIdentityOptions,
@@ -928,6 +974,11 @@ export function verifyBackgroundSessionProcessIdentity(
   if (command == null || command.trim() === '') {
     return result('unreadable')
   }
+  if (session.processMarker !== undefined) {
+    return result(
+      markedCommandLineIdentity(command, session, session.processMarker),
+    )
+  }
   return result(
     commandLineMatchesBackgroundSession(command, session)
       ? 'matches'

src/cli/bgRouting.ts

@@ -1,4 +1,55 @@
+import { randomBytes } from 'node:crypto'
+
 export const BACKGROUND_SESSION_ID_ENV =
   'OPENCLAUDE_INTERNAL_BACKGROUND_SESSION_ID'
 export const BACKGROUND_SESSION_LAUNCHER_PID_ENV =
   'OPENCLAUDE_INTERNAL_BACKGROUND_LAUNCHER_PID'
+
+export const BACKGROUND_PROCESS_MARKER_FLAG =
+  '--openclaude-bg-session-marker'
+
+const BACKGROUND_PROCESS_MARKER_BYTES = 32
+const BACKGROUND_PROCESS_MARKER_RE = /^[a-f0-9]{64}$/
+
+export function isValidBackgroundProcessMarker(value: unknown): value is string {
+  return (
+    typeof value === 'string' && BACKGROUND_PROCESS_MARKER_RE.test(value)
+  )
+}
+
+export function generateBackgroundProcessMarker(
+  getRandomBytes: (size: number) => Uint8Array = randomBytes,
+): string {
+  const bytes = getRandomBytes(BACKGROUND_PROCESS_MARKER_BYTES)
+  if (bytes.byteLength !== BACKGROUND_PROCESS_MARKER_BYTES) {
+    throw new Error(
+      'Background process marker entropy source returned the wrong length',
+    )
+  }
+  return Buffer.from(bytes).toString('hex')
+}
+
+export function backgroundProcessMarkerToken(marker: string): string {
+  if (!isValidBackgroundProcessMarker(marker)) {
+    throw new Error('Invalid background process marker')
+  }
+  return `${BACKGROUND_PROCESS_MARKER_FLAG}=${marker}`
+}
+
+export function stripBackgroundProcessMarkerArgs(args: string[]): string[] {
+  const first = args[0]
+  const inlinePrefix = `${BACKGROUND_PROCESS_MARKER_FLAG}=`
+  if (
+    first?.startsWith(inlinePrefix) &&
+    isValidBackgroundProcessMarker(first.slice(inlinePrefix.length))
+  ) {
+    return args.slice(1)
+  }
+  if (
+    first === BACKGROUND_PROCESS_MARKER_FLAG &&
+    isValidBackgroundProcessMarker(args[1])
+  ) {
+    return args.slice(2)
+  }
+  return [...args]
+}

src/main.tsx

@@ -49,6 +49,7 @@ import type { ToolInputJSONSchema } from './Tool.js';
 import { createSyntheticOutputTool, isSyntheticOutputToolEnabled } from './tools/SyntheticOutputTool/SyntheticOutputTool.js';
 import { registerTaskReportCommand } from './cli/commands/taskReport.js';
 import { registerAimlapiCommand } from './cli/aimlapiCommand.js';
+import { BACKGROUND_PROCESS_MARKER_FLAG, isValidBackgroundProcessMarker } from './cli/bgRouting.js';
 import { getTools } from './tools.js';
 import { canUserConfigureAdvisor, getInitialAdvisorSetting, isAdvisorEnabled, isValidAdvisorModel, modelSupportsAdvisor } from './utils/advisor.js';
 import { isAgentSwarmsEnabled } from './utils/agentSwarmsEnabled.js';
@@ -3644,6 +3645,13 @@ async function run(): Promise<CommanderCommand> {
     }
   }).version(`${MACRO.DISPLAY_VERSION ?? MACRO.VERSION} (OpenClaude)`, '-v, --version', 'Output the version number');
 
+  program.addOption(new Option(`${BACKGROUND_PROCESS_MARKER_FLAG} <marker>`, 'Internal background process identity marker').argParser(value => {
+    if (!isValidBackgroundProcessMarker(value)) {
+      throw new InvalidArgumentError('Invalid background process marker');
+    }
+    return value;
+  }).hideHelp());
+
   // Worktree flags
   program.option('-w, --worktree [name]', 'Create a new git worktree for this session (optionally specify a name)');
   program.option('--tmux', 'Create a tmux session for the worktree (requires --worktree). Uses iTerm2 native panes when available; use --tmux=classic for traditional tmux.');