# TypeScript Review Report

**Branch**: feat/176-tmux-abstraction-layer -> main
**Date**: 2026-05-17
**Diff**: `git diff 40f9537...HEAD` (5 files, +250/-71)

## Issues in Your Changes (BLOCKING)

### CRITICAL

(none)

### HIGH

(none)

## Issues in Code You Touched (Should Fix)

(none)

## Pre-existing Issues (Not Blocking)

(none)

## Suggestions (Lower Confidence)

(none)

## Analysis Notes

All changed code was reviewed against the TypeScript skill checklist. Key observations:

1. **No `any` types** -- All new code uses proper types. The `(err: unknown)` narrowing in the `.catch()` handler at `tmux-connector.ts:353-358` correctly uses `instanceof Error` before accessing `.message`. The `isOutputMessage` type guard at line 54-64 uses `Record<string, unknown>` (not `any`) for the intermediate cast, which is the standard pattern.

2. **Discriminated union usage** -- The `Result<T, E>` discriminated union is correctly narrowed via `.ok` checks before accessing `.error.message` in all four new `cleanupResult` handling blocks (spawn:165-171, destroy:204-209, dispose:247-253, triggerExit:629-635).

3. **Type safety of new extracted methods** -- `buildActiveSession()` (line 263) returns `ActiveSession` with correct field types. `forceDeliverRemaining()` (line 514) operates on properly typed `Map<number, OutputMessage>`. `startSentinelWatcher()` and `startMessagesWatcher()` maintain the same type contracts as the original inlined code.

4. **`Math.min(...intervals)` edge case** (line 394) -- Guarded by `if (this.activeSessions.size === 0) return` at line 389, so `intervals` is never empty. `Math.min()` on an empty spread returns `Infinity`, which would be caught by `Math.max(Infinity, MIN_CHECK_INTERVAL_MS)` anyway, so double-safe.

5. **`staleEntries` type annotation** (line 423) -- `Array<[string, ActiveSession]>` is correctly typed as a tuple array, matching the `[taskId, session]` destructuring at line 444.

6. **Test mock types** -- The `as unknown as TmuxConnectorDeps['watch']` casts in tests (lines 92, 428) follow the established pattern for mock objects that implement a structural subset of the target interface. The new `on: vi.fn()` additions to watcher mocks (lines 74-75) match the `FSWatcher.on()` method used in production code.

7. **Strict mode compliance** -- Project uses `strict: true` in tsconfig. `npm run typecheck` passes clean with no errors.

## Summary

| Category | CRITICAL | HIGH | MEDIUM | LOW |
|----------|----------|------|--------|-----|
| Blocking | 0 | 0 | 0 | 0 |
| Should Fix | 0 | 0 | 0 | 0 |
| Pre-existing | 0 | 0 | 0 | 0 |

**TypeScript Score**: 9/10
**Recommendation**: APPROVED

The changes demonstrate strong type safety practices: proper `unknown` narrowing, discriminated union handling, no `any` usage, and consistent Result type patterns. The extracted methods maintain correct type contracts. The one point deduction from a perfect score is for the project-wide absence of `noUncheckedIndexedAccess` in tsconfig (pre-existing configuration choice, not introduced by this branch).
