internal/

Package filter provides a byte-stream filter that detects an adjacent Ctrl+] Ctrl+] (0x1D 0x1D) sequence to trigger a detach action, while forwarding a single Ctrl+] immediately to the PTY.

Package initmode reports whether the current sbsh process should take on PID-1 responsibilities (zombie reaping, signal forwarding).

Package pidutil exposes a stable per-process identifier used to detect PID reuse: after a process exits, the kernel may recycle its PID for an unrelated process, so callers that persist PIDs and later signal them must reconfirm identity before delivering the signal.