Function acquireLock

src/utils/autoUpdater.ts:176–249

* Attempts to acquire a lock for auto-updater * @returns true if lock was acquired, false if another process holds the lock

()

 * @returns true if lock was acquired, false if another process holds the lock
 */
async function acquireLock(): Promise<boolean> {
  const fs = getFsImplementation()
  const lockPath = getLockFilePath()

  // Check for existing lock: 1 stat() on the happy path (fresh lock or ENOENT),
  // 2 on stale-lock recovery (re-verify staleness immediately before unlink).
  try {
    const stats = await fs.stat(lockPath)
    const age = Date.now() - stats.mtimeMs
    if (age < LOCK_TIMEOUT_MS) {
      return false
    }
    // Lock is stale, remove it before taking over. Re-verify staleness
    // immediately before unlinking to close a TOCTOU race: if two processes
    // both observe the stale lock, A unlinks + writes a fresh lock, then B
    // would unlink A's fresh lock and both believe they hold it. A fresh
    // lock has a recent mtime, so re-checking staleness makes B back off.
    try {
      const recheck = await fs.stat(lockPath)
      if (Date.now() - recheck.mtimeMs < LOCK_TIMEOUT_MS) {
        return false
      }
      await fs.unlink(lockPath)
    } catch (err) {
      if (!isENOENT(err)) {
        logError(err as Error)
        return false
      }
    }
  } catch (err) {
    if (!isENOENT(err)) {
      logError(err as Error)
      return false
    }
    // ENOENT: no lock file, proceed to create one
  }

  // Create lock file atomically with O_EXCL (flag: 'wx'). If another process
  // wins the race and creates it first, we get EEXIST and back off.
  // Lazy-mkdir the config dir on ENOENT.
  try {
    await writeFile(lockPath, `${process.pid}`, {
      encoding: 'utf8',
      flag: 'wx',
    })
    return true
  } catch (err) {
    const code = getErrnoCode(err)
    if (code === 'EEXIST') {
      return false
    }
    if (code === 'ENOENT') {
      try {
        // fs.mkdir from getFsImplementation() is always recursive:true and
        // swallows EEXIST internally, so a dir-creation race cannot reach the
        // catch below — only writeFile's EEXIST (true lock contention) can.
        await fs.mkdir(getClaudeConfigHomeDir())
        await writeFile(lockPath, `${process.pid}`, {