# 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)