Function countConcurrentSessions

src/utils/concurrentSessions.ts:168–204

()

 * Returns 0 on any error (conservative).
 */
export async function countConcurrentSessions(): Promise<number> {
  const dir = getSessionsDir()
  let files: string[]
  try {
    files = await readdir(dir)
  } catch (e) {
    if (!isFsInaccessible(e)) {
      logForDebugging(`[concurrentSessions] readdir failed: ${errorMessage(e)}`)
    }
    return 0
  }

  let count = 0
  for (const file of files) {
    // Strict filename guard: only `<pid>.json` is a candidate. parseInt's
    // lenient prefix-parsing means `2026-03-14_notes.md` would otherwise
    // parse as PID 2026 and get swept as stale — silent user data loss.
    // See anthropics/claude-code#34210.
    if (!/^\d+\.json$/.test(file)) continue
    const pid = parseInt(file.slice(0, -5), 10)
    if (pid === process.pid) {
      count++
      continue
    }
    if (isProcessRunning(pid)) {
      count++
    } else if (getPlatform() !== 'wsl') {
      // Stale file from a crashed session — sweep it. Skip on WSL: if
      // ~/.claude/sessions/ is shared with Windows-native Claude (symlink
      // or CLAUDE_CONFIG_DIR), a Windows PID won't be probeable from WSL
      // and we'd falsely delete a live session's file. This is just
      // telemetry so conservative undercount is acceptable.
      void unlink(join(dir, file)).catch(() => {})
    }
  }
  return count
}