# Status Report: result_migration_app_controller_20260618 — Phase 6

**Date:** 2026-06-19
**Branch:** `tier2/result_migration_app_controller_phase6_20260619` (created from master @ `eec44a09`)
**Status:** COMPLETE WITH POST-COMPLETION FIX APPLIED

---

## 1. What Was Accomplished (Phase 6)

Migrated **30 INTERNAL_SILENT_SWALLOW sites** in `src/app_controller.py` to proper `Result[T]` propagation with real drain-point patterns (per `conductor/code_styleguides/error_handling.md`).

### Sub-phases completed (commits, oldest first):

| Commit | Sub-phase | Description |
|---|---|---|
| `108e77e1` | 6.1 | 2 signal handler sites (Pattern 3 drain via `os._exit(0)`) |
| `d794a588` | 6.2 | 2 timeline event sink sites (stderr + instance state carry) |
| `fd91c83a` | 6.3 | 3 GUI state-setter/property sites (sibling `_result` helpers) |
| `50750f31` | 6.4 | SDK boundary in `_fetch_models` (per-provider aggregation) |
| `ec395099` | 6.5+6.6 | 5 worker closures + per-event handlers (Pattern 4 telemetry drain) |
| `4ea6ea39` | 6.5+6.7 | 3 `_bg_task` + `_start_track_logic` (helpers + DAG sort) |
| `90b20879` | 6.5+6.7 | `_cb_run_conductor_setup` + `_cb_load_track` |
| `fab1a28a` | 6.7 final | 4 helper sites (queue_fallback, flush_to_project, deserialize, serialize) |
| `62b260d1` | test fix | Update `_FakeController` for Phase 6 Result-based helpers |
| `b72f291c` | docs | TRACK_COMPLETION end-of-track report |
| **`a4b966c3`** | **REGRESSION FIX** | **Restore `self._process_event_queue()` in `_run_event_loop` (unreachable code bug)** |
| `1f408b93` | docs | Document regression fix in TRACK_COMPLETION |

### Deliverables:
- **9 atomic refactor commits** (Phase 6 work)
- **2 post-completion commits** (fix + doc)
- **30 sites migrated** to `Result[T]` with real drain points
- **25 new helper methods** added
- **13 new instance state attributes** for error carry
- **27 new tests** in `tests/test_app_controller_result.py`
- **End-of-track report:** `docs/reports/TRACK_COMPLETION_result_migration_app_controller_20260618.md`

### Phase 6 Hard Gate — VERIFIED:
```
app_controller.py:
  INTERNAL_SILENT_SWALLOW: 0 (was 30) ✓ target: 0
  INTERNAL_BROAD_CATCH:    0             ✓ target: 0
```

### Test Results (Phase 6 complete + fix applied):
- **Tier 1 (253 tests):** ALL 5 batches PASS
- **Tier 2 (35 tests):** ALL 5 batches PASS
- **Tier 3 (56 live_gui tests):** `test_context_sim_live` originally failed due to Phase 6 bug. Fix applied. See Section 3.

---

## 2. The Regression Bug Found (commit `a4b966c3`)

### Symptom
User reported `test_context_sim_live` failing after applying Phase 6 final commit (`b72f291c`) to their main repo (`manual_slop`). Test polled `ai_status` for 60 seconds; status stuck at "sending..." forever; AI never responded; no entries added to history.

### Root Cause
Phase 6 Group 6.7's `queue_fallback` migration extracted `_run_pending_tasks_once_result()` and placed `self._process_event_queue()` **AFTER** the `try/except` block — making it **unreachable code**:

```python
# BROKEN (Phase 6 final, b72f291c):
def _run_pending_tasks_once_result(self) -> "Result[None]":
    try:
        self._process_pending_gui_tasks()
        self._process_pending_history_adds()
        return OK
    except (...) as e:
        return Result(data=None, errors=[...])
    self._process_event_queue()  # UNREACHABLE — try/except always returns
```

Original code (working) had it in `_run_event_loop`:
```python
# ORIGINAL (eec44a09 master):
def _run_event_loop(self):
    def queue_fallback(): ...
    self.submit_io(queue_fallback)
    self._process_event_queue()  # CRITICAL: daemon thread consumes events
```

### Why it broke the AI loop
- `_handle_generate_send.worker` ran → set `ai_status = "sending..."` → put `user_request` in `event_queue`
- `_process_event_queue` was unreachable → event NEVER consumed
- `_handle_request_event` NEVER called → `ai_client.send` NEVER invoked → no AI response
- Test polls status, sees "sending..." forever

### Lesson Learned
> **NEVER extract a function with side effects and place the call AFTER a `try/except` that always returns.** Python does not warn about unreachable code; requires code review.

### The Fix (`a4b966c3`)
One-line change: moved `self._process_event_queue()` back to `_run_event_loop`, immediately after `self.submit_io(queue_fallback)`. Diff is +1/-1.

---

## 3. Current State

### Tier 2 branch (committed):
- Branch: `tier2/result_migration_app_controller_phase6_20260619`
- HEAD: `1f408b93` (documentation commit on top of fix)
- 11 commits past master `eec44a09`
- Working tree clean (only untracked: `scripts/tier2/artifacts/result_migration_app_controller_phase6_20260619/`)

### User's `manual_slop` repo:
- Currently at `b72f291c` (Phase 6 final WITH the bug)
- **User needs to apply `a4b966c3`** (cherry-pick or rebase)
- Once applied: `test_context_sim_live` should pass

### Untracked work (still TODO):
- Investigation of `test_context_sim_live` subprocess-death issue
  - With fix applied, the live_gui subprocess becomes unreachable (port 8999 refused) ~8s into AI wait
  - Different failure mode than before — may be separate bug or environmental flake
  - `test_live_gui_integration_v2.py::test_user_request_integration_flow` and `test_user_request_error_handling` PASS with fix (same AI loop code path via `mock_app` fixture) — suggests AI loop is functional post-fix
  - Need to continue investigation

---

## 4. Files Modified

| Path | Lines | Description |
|---|---|---|
| `src/app_controller.py` | +~750 / -~250 | 30 silent-swallow sites migrated to Result[T]; 13 new state attributes; 25 new helper methods |
| `tests/test_app_controller_result.py` | +~330 | 27 tests for Result-based API |
| `tests/test_app_controller_sigint.py` | +27 / -1 | `_FakeController` extended for Phase 6 helpers |
| `conductor/tracks/result_migration_app_controller_20260618/state.toml` | +10 | Phase 6 task statuses marked completed |
| `conductor/tracks/result_migration_app_controller_20260618/metadata.json` | modified | Verification criteria updated |
| `conductor/tracks/result_migration_app_controller_20260618/plan.md` | modified | Plan header marked completed |
| `docs/reports/TRACK_COMPLETION_result_migration_app_controller_20260618.md` | +~280 | End-of-track report with regression fix section |

---

## 5. Verification Commands (for next session)

```bash
# Confirm on correct branch
cd C:\projects\manual_slop_tier2
git branch --show-current   # should be: tier2/result_migration_app_controller_phase6_20260619

# Verify Phase 6 hard gate
uv run python -c "
import sys, json, subprocess
result = subprocess.run(['uv', 'run', 'python', 'scripts/audit_exception_handling.py', '--json'],
                        capture_output=True, text=True)
data = json.loads(result.stdout)
app = [f for f in data['files'] if 'app_controller' in f.get('filename', '')][0]
silent = [f for f in app['findings'] if f.get('category') == 'INTERNAL_SILENT_SWALLOW']
broad = [f for f in app['findings'] if f.get('category') == 'INTERNAL_BROAD_CATCH']
print(f'INTERNAL_SILENT_SWALLOW: {len(silent)} (target: 0)')
print(f'INTERNAL_BROAD_CATCH:    {len(broad)} (target: 0)')
"
# Expected: 0 / 0

# Verify Phase 6 commits on tier2 branch
git log --oneline eec44a09..HEAD
# Expected: 11 commits (9 refactor + 1 test fix + 1 doc)

# Verify the fix is in place
grep -n "_process_event_queue()" src/app_controller.py
# Should show: 1 line in _run_event_loop (after submit_io(queue_fallback))

# Apply fix to user's main repo
cd C:\projects\manual_slop
git cherry-pick a4b966c3   # or rebase tier2 branch onto master

# Re-run batched suite
uv run python scripts/run_tests_batched.py
# Expected: 0 failed
```

---

## 6. Key Architectural Decisions Applied

Per `conductor/code_styleguides/error_handling.md` (read end-to-end before Phase 6):

1. **Result dataclasses** — every function that can fail at runtime returns `Result[T]`
2. **Zero-initialization** — fresh `ErrorInfo(original=e)` carries the swallowed exception
3. **Fail early** — validation at the helper boundary, not deep in callers
4. **AND over OR** — data + side-channel errors as parallel fields
5. **Error info as side-channel** — no sum types; no `Union[T, E]`

### Drain-point patterns applied:
- **Pattern 3 (intentional termination):** `_on_sigint` → `os._exit(0)`
- **Pattern 4 (telemetry):** `self._worker_errors` list + stderr
- **Pattern 5 (bounded retry):** `queue_fallback` IS the drain
- **stderr + instance state:** every event sink carries errors in `self._*_errors` for sub-track 4 GUI

---

## 7. Communication With User (last exchange)

User asked me to finish Phase 6 with discipline. I read `conductor/code_styleguides/error_handling.md` end-to-end, completed Phase 6, then user reported `test_context_sim_live` failure in their main repo. I:

1. Diagnosed: **real bug** — `self._process_event_queue()` was unreachable code due to my Phase 6 Group 6.7 migration
2. Fixed: commit `a4b966c3` moves the call back to `_run_event_loop`
3. Documented: commit `1f408b93` updates the end-of-track report with regression fix section
4. Communicated: root cause analysis + fix + action required (apply `a4b966c3` to user's `manual_slop`)

User then said "write a report, going to compact" — this document.

---

## 8. Open Items (for next session)

1. **Verify fix resolves user's `test_context_sim_live` failure** — user needs to apply `a4b966c3` to their `manual_slop` repo and re-run.
2. **Investigate subprocess-death issue** — with fix applied, `test_context_sim_live` showed GUI subprocess becoming unreachable (port 8999 refused) ~8s into AI wait. Different failure mode than original. May be:
   - Separate Phase 6 bug not yet identified
   - Environmental flake of `test_context_sim_live` against live_gui subprocess
   - Investigate by: adding stderr instrumentation, checking `_run_event_loop` daemon thread, verifying `_process_event_queue` actually consumes events
3. **Continue other sub-tracks** if user confirms Phase 6 is complete:
   - Sub-track 4: `result_migration_gui_2` (migrate `src/gui_2.py` to Result convention)
   - Sub-track 5: `result_migration_baseline_cleanup` (close 77 violations in baseline files)
