# Review by Principal Systems Engineer (Google/Stripe caliber) (Round 4)

Now I have a thorough understanding of the implementation. Let me write the review.

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## Principal Systems Engineer Review

I've reviewed the full implementation (2,542 lines added across 23 files) against the PRD. Here's my assessment:

### Completeness

All 8 functional requirements from the PRD are implemented:

- **FR-1 ✓**: `colonyos tui` command and `--tui` flag on `colonyos run`
- **FR-2 ✓**: `TranscriptView` wrapping `RichLog` with auto-scroll and phase/tool/text rendering
- **FR-3 ✓**: `Composer` with `TextArea`, auto-grow 3→8 lines, Enter/Shift+Enter bindings
- **FR-4 ✓**: `StatusBar` with phase, cost, turns, elapsed, spinning indicator
- **FR-5 ✓**: `TextualUI` adapter implementing all 8 PhaseUI callbacks, thread-safe via janus queue
- **FR-6 ✓**: All keybindings (Enter, Shift+Enter, Ctrl+C, Ctrl+L, Escape)
- **FR-7 ✓**: `tui = ["textual>=0.40", "janus>=1.0"]` optional dep, import guarded
- **FR-8 ✓**: All output sanitized through `sanitize_display_text()`, including expanded OSC/DCS/CR attack vectors

All 1,695 existing tests pass. All 88 new TUI tests pass. All 59 sanitize tests pass.

### Findings

VERDICT: approve

FINDINGS:
- [src/colonyos/tui/app.py:172]: Lambda closure `lambda: self._run_callback(text)` captures `self._run_callback` late. If `_run_callback` were ever reassigned between submission and worker execution, the wrong callback runs. Low risk given current usage but worth noting — a local binding (`cb = self._run_callback; lambda: cb(text)`) would be defensive.
- [src/colonyos/tui/app.py:95-102]: Initial prompt runs in a worker with `exclusive=True`, which is correct for preventing concurrent orchestrator runs. However, there's no guard against the user submitting a second prompt via the composer while the initial prompt's worker is still running — `exclusive=True` silently cancels the previous worker. This is actually the right behavior for "cancel and redirect," but users get no feedback that the first run was abandoned.
- [src/colonyos/tui/adapter.py:155-157]: `on_tool_input_delta` attempts JSON parse on every delta. For tools with large inputs (e.g., big Write payloads), this means repeated `json.loads()` failures on incomplete JSON. The cost is low (caught exception, O(n) parse) but could be optimized with a simple "seen closing brace" heuristic.
- [src/colonyos/tui/widgets/status_bar.py:283-287]: Multiple reactive attributes (`phase_name`, `total_cost`, `turn_count`, etc.) each trigger a watch callback by default in Textual, but `_render_bar()` is also called explicitly in every setter method. This means state changes could trigger double renders — once from the reactive watcher and once from the explicit call. The explicit calls are correct and necessary for the spinner, but the reactive declarations should use `reactive(..., always_update=False)` or the watchers should be removed to avoid redundant work.
- [src/colonyos/sanitize.py]: The expanded sanitizer now correctly handles OSC (clipboard write), DCS, bare CR attacks, and single-char escapes. This is a genuine security improvement that benefits the entire project, not just the TUI. Well done.
- [src/colonyos/tui/app.py:105-112]: `on_unmount` cancels the consumer task and closes the janus queue, but if a worker thread is still running (pushing to `sync_q`), it will get a `RuntimeError` from writing to a closed queue. The cleanup should signal the worker to stop first (e.g., via a sentinel value or threading.Event).
- [src/colonyos/cli.py:4237-4251]: `_run_callback` creates a new `TextualUI` adapter per submission but reuses `app_instance.event_queue`. This is correct — fresh adapter state per run, shared queue. Good design.
- [tests/tui/test_adapter.py]: Excellent test coverage — 352 lines covering all 8 callbacks, sanitization, partial JSON parsing, edge cases, and thread safety. The `FakeSyncQueue` avoids requiring a running event loop, which keeps tests fast and deterministic.

SYNTHESIS:
This is a clean, well-scoped v1 implementation. The architecture is sound: the janus queue bridge between the synchronous orchestrator thread and Textual's async event loop is the right call, and avoids the much riskier path of refactoring the orchestrator to be fully async. The adapter pattern reuses the existing `ui_factory` injection point — zero changes to `agent.py` or the orchestrator's core logic. The sanitizer hardening (OSC, DCS, CR attacks) is a legitimate security improvement that applies project-wide.

The two issues worth tracking for v2 are: (1) the worker cancellation on unmount could race with the orchestrator thread, and (2) the `exclusive=True` worker behavior means rapid resubmission silently kills the previous run without explicit user feedback. Neither is a blocker — the first produces a caught exception at shutdown, and the second matches the PRD's "Ctrl+C to cancel and redirect" user story. The test coverage is strong (88 new tests, zero regressions across 1,695 existing tests), and the optional dependency boundary is clean. Ship it.