headquarter/openspec/changes/responsive-terminal/verify.md

Verify: Responsive Web Terminal

Verification Report

What Changed

Implemented a resilient, responsive web terminal with auto-reconnect, heartbeat, local echo, and scrollback persistence across 3 chained PRs.

Backend (PR-1):

• terminal_session.py: Added termios echo detection, exit reason tracking, closed public property
• terminal_manager.py: Added heartbeat tracking (15s ping / 60s idle timeout), message batching (16ms), ping/pong handling, task reference storage
• terminal.py: Added ping/pong routing, echo state checks, session_ended notification

Frontend (PR-2):

• use-terminal-connection.ts: WebSocket lifecycle, exponential backoff reconnect, heartbeat, local echo deduplication, resize debounce/throttle, scrollback callbacks, Ctrl+Shift+R shortcut
• use-terminal-connection.test.ts: 13 tests covering connection lifecycle, reconnect backoff, resize, scrollback

Frontend UI (PR-3):

• terminal.tsx: Rewritten with status bar, session-ended overlay, reconnect banner, ResizeObserver, light/dark theme, xterm-addon-serialize
• styles.css: Added overlay, reconnect banner, spinner animation styles

Documentation:

• docs/features/terminal.md: User guide with connection states, keyboard shortcuts, troubleshooting
• docs/architecture/frontend.md: Terminal component stack and data flow
• docs/architecture/backend.md: Terminal system architecture and protocol

Acceptance Criteria Coverage

AC	Status	Evidence
AC-1: Auto-reconnection	✅	Implemented in useTerminalConnection — 1s→30s backoff, max 10 attempts
AC-2: Heartbeat	✅	15s ping interval, 5s pong timeout, 60s idle close on server
AC-3: Local echo	✅	Printable ASCII echoed immediately, server deduplication, echo-state control
AC-4: Resize debounce	✅	200ms debounce + 500ms throttle in sendResize
AC-5: Scrollback serialization	✅	SerializeAddon + sessionStorage + restore with divider
AC-6: Connection quality indicator	✅	Status bar with color-coded dot, latency tooltip, attempt counter
AC-7: Graceful container exit	✅	session_ended message + overlay with Reconnect/Go Back
AC-8: Backend message batching	✅	16ms batch window in _read_loop
AC-9: Keyboard shortcut	✅	Ctrl+Shift+R triggers reconnect()

Quality Gates

Gate	Result
Frontend typecheck	✅ Clean
Frontend lint	✅ Clean
Frontend tests	✅ 48 passed (13 new hook tests)
Backend unit tests	✅ 101 passed (16 new terminal tests)
Backend ruff	✅ Clean

Commits

• 6c8cfe9 — feat: responsive web terminal with auto-reconnect, heartbeat, and local echo
• a01e625 — docs: add responsive terminal documentation

Risks and Limitations

• Docker exec PTY is not resumable across reconnects — new shell is spawned. Scrollback serialization makes this transparent.
• Local echo only works for printable ASCII; control chars and escape sequences round-trip.
• termios echo detection is Unix-only (Linux/macOS). The fallback is echo-enabled.
• Integration tests require Docker + running containers; not covered in automated test suite.

Follow-ups

• Manual end-to-end testing with real containers
• Consider adding xterm-addon-webgl for GPU rendering on high-latency connections
• Consider scrollback persistence across full page reloads (currently sessionStorage only)