# MistakeTracker + file-provenance ledger (#12)

**Status:** shipped `v2.7.4-mistake-tracker-ledger`
**Source:** `boocode_code_review_v2.md` §1 #12, §5e (cline — algorithm-reimplemented, not vendored).

Two native-inference (apps/server) hardening features. One cohesive backend change (they share
`TurnArgs` + the tool-phase observation point) + a small frontend sentinel render.

## Part A — MistakeTracker (heterogeneous-failure recovery)

Complements the doom-loop guard (`sentinels.ts:detectDoomLoop`, which only catches *identical*
repeats) by catching a run of consecutive tool **failures** the model isn't recovering from.

- New pure `apps/server/src/services/inference/mistake-tracker.ts` (mirrors `detectDoomLoop`):
  - `FailureKind = 'zod_reject' | 'tool_not_found' | 'exec_error' | 'api_error' | 'permission_denied'`
    (all already distinguished in `tool-phase.ts:executeToolCall`).
  - `MISTAKE_THRESHOLD = 3`.
  - State `{ run: FailureKind[]; nudges: number }` — `run` is the current consecutive-failure streak,
    reset on ANY successful tool step; `nudges` counts recovery injections not yet cleared by a success.
  - `recordStep(state, outcome)` where outcome is a failure kind or `'success'`.
  - `detectMistakePattern(state): 'nudge' | 'escalate' | null` — `run.length >= 3` → `'nudge'` the first
    time (`nudges === 0`), `'escalate'` if it trips again while `nudges >= 1` (no intervening success).
- Lives in `TurnArgs` (loop-local, reset per `runInference`, like `recentToolCalls`).
- Integration in `turn.ts` loop: after each tool phase, `recordStep` per tool outcome; then
  `detectMistakePattern`:
  - `'nudge'` (decision: soft + escalate): append a transient **model-facing** recovery-guidance system
    message to the NEXT turn's payload (re-read schemas, verify paths exist before acting, try a
    different approach — not retry variations), insert a `mistake_recovery` UI sentinel
    (`escalated:false`), bump `nudges`, reset `run`. Loop continues.
  - `'escalate'`: stop the turn (break), insert a `mistake_recovery` sentinel (`escalated:true`,
    `can_continue:true`, cap-hit-style), finalize. Prevents heterogeneous failures from burning the
    whole step budget.

## Part B — File-provenance ledger (Read-only)

- Accumulate file paths read by `view_file`/`grep`/`find_files`/`list_dir` into `TurnArgs.filesRead:
  Set<string>` (recorded at the tool-phase, like the failure outcomes).
- On compaction (`compaction.ts:buildPrompt`), inject a deterministic, sorted `## Files Read` list into
  the summary prompt context so the summarizer merges it into the rolling summary — **no new
  table/column**; it propagates as summary text across compactions. `compaction-prompt.ts`'s
  `SUMMARY_TEMPLATE` already has a `## Relevant Files` section to extend/merge with.
- BooChat is **read-only** (no write tools on apps/server) → "Files Modified" is N/A here; only
  "Files Read". (The apps/coder write side can add "Modified" later.)

## Sentinel contract (pinned — backend + frontend must match)

New sentinel kind on `MessageMetadata` in BOTH `apps/server/src/types/api.ts` AND
`apps/web/src/api/types.ts`:
```
{ kind: 'mistake_recovery'; failure_kinds: string[]; count: number; escalated: boolean; can_continue?: boolean }
```
- `role='system'`, `status='complete'`, stripped from the LLM payload via `isAnySentinel` in
  `payload.ts` (UI-only) and `compaction.ts:buildHeadPayload`.
- Frontend render branch in `apps/web/src/components/MessageBubble.tsx`: `escalated:false` →
  "Hit repeated different errors — recovery guidance injected, continuing." `escalated:true` →
  "Repeated errors persisted — stopped the turn." (mirror the doom-loop/cap-hit branches).

## Decisions (2026-06-01)
- MistakeTracker intervention: **soft nudge + escalate**.
- **UI sentinel** for recovery (`mistake_recovery`).

## Files (backend, one agent) / (frontend, one agent)
- Backend: `mistake-tracker.ts` (new), `turn.ts`, `tool-phase.ts`, `sentinels.ts`,
  `sentinel-summaries.ts`, `payload.ts`, `compaction.ts`, `compaction-prompt.ts`, `types/api.ts` +
  tests (`mistake-tracker.test.ts`, ledger/compaction assertions).
- Frontend: `apps/web/src/api/types.ts` (MessageMetadata arm) + `MessageBubble.tsx` (render branch).
  MUST NOT touch Sam's WIP web files.

## Verify
- `pnpm -C apps/server test`; `pnpm -C apps/server build`; `npx tsc -p apps/web/tsconfig.app.json --noEmit`
