# PR body — fix/diagnostic-walk-and-spec

**Title:** `Fix diagnostic walk counter reset, add c2 cap, wire field_user write-through, document §5.7`

**Compare URL:** https://github.com/2ppaamm/capstoneapi/pull/new/fix/diagnostic-walk-and-spec

---

## Summary

Implements all 6 tasks from `docs/algorithms/cc-implementation-diagnostic-walk.md`, fixing three bugs in the diagnostic walk plus the spec gap that hid them.

### Three bugs (and which task addresses each)

| # | Bug | Task | Fix |
|---|---|---|---|
| 1 | `wrong_count_at_level` carried across level changes → false cementing two levels below true ceiling | Task 2 | Reset wrong/correct counters when `getNextLevelUp/Down` returns a different level. Deliberately skip reset at the floor (level doesn't change) so 2-wrongs cement still fires there. |
| 2 | No c2 cap → lucky-guess promotion could cement `final_level` above any level the user answered correctly | Task 3 | `applyC2Cap()` in both cement branches and `completeDiagnostic`'s fallback. c2 = `MAX(levels.start_maxile_level)` over correct attempts this session+field via JOIN through `skill_track`. |
| 3 | `users.maxile_level` written directly from `diagnostic_field_progress.final_level`, bypassing canonical `field_user` aggregation → cascade recomputes from empty `field_user` on first answer post-diagnostic, causing drift | Task 4 | Write each cemented field to `field_user` with monotonic guard, recompute `users.maxile_level` from `AVG(field_user.field_maxile WHERE > 0)` per §3.4, propagate to `result.overall_maxile`. |

Plus Task 1 (spec patch §5.7), Task 5 (`complated_at` → `completed_at` typo), Task 6 (docstring drift on `applyAdaptiveAlgorithm`).

## Smoke trace

Verified end-to-end via `ops/.tmp-smoke-diag-walk.php` against local DB (transaction-rolled-back so no durable state). Starting `current_level = 100` on field 37 (Number & Algebra, local field ID):

```
INITIAL                  current_level=100  wrong=0  correct=0  final=null   completed=F
Q1 correct at L100       current_level=200  wrong=0  correct=0  final=null   completed=F
Q2 wrong   at L200       current_level=100  wrong=0  correct=0  final=null   completed=F
Q3 wrong   at L100       current_level=100  wrong=1  correct=0  final=null   completed=F
Q4 wrong   at L100       current_level=100  wrong=2  correct=0  final=100    completed=T

field_user rows for this user:
  field_id=37  field_maxile=100.00  month_achieved=202605

users.maxile_level=100.00   AVG(field_user.field_maxile WHERE >0)=100.000000   match=YES
result.overall_maxile=100
```

**Key observations:**

- **Q2 → Q3 transition**: counters correctly reset on the L200→L100 step-down (the bug). Without the fix, Q3's wrong would have incremented to 2 and cemented prematurely. The playbook called this exact scenario out.
- **Q3 → Q4 at the floor**: `getNextLevelDown(100, 37)` returns 100 (this field's min level *is* 100). Level didn't change, counter not reset — wrong climbs from 1 to 2 across Q3+Q4 → cement fires.
- **Cement value is 100, not 0**: the playbook trace said "CEMENT at L0 (one below 100)" but on actual local data field 37's floor is L100, so `getNextLevelDown(100, 37) = 100`. The walk semantics are correct; the playbook's "L0" was conceptual.
- **`users.maxile_level == AVG(field_user.field_maxile)`** ✅ — the canonical-aggregation contract from §3.4 is now honoured by the diagnostic completion path.

## Decisions made under the autonomy directive

1. **`month_achieved` column is INT `YYYYMM`, not the string `Y-m`** that the spec patch text used. Verified against local schema (`int unsigned NOT NULL`) and existing values (`202605`, `202510`, …). Used `(int) now()->format('Ym')`.

2. **`FieldUser` model was missing `month_achieved` from `$fillable`** — added it. Mass-assignment via `updateOrCreate` would have silently dropped the column otherwise. Smallest possible touch.

3. **Counter reset is gated on actual level change**, not on entering the step-up / step-down branch unconditionally. The spec text says "step down + reset," but the explanatory parenthetical ("the next wrong is at a different level, so the counter is per-level not cumulative") clarifies the intent. At the floor, `getNextLevelDown` returns the same level, no reset, so the 2-wrongs cement rule still fires there — matches the playbook trace where Q3+Q4 both at L100 cement.

4. **Added `AssessmentSession::user()` belongsTo relation** — the original `completeDiagnostic` did `$session->user->update(...)`, but the relation was never defined. Latent `NullPointerException` waiting on the first prod diagnostic completion. Adding the relation is the smallest possible enabler for Task 4 (and revives the original intent). Two lines plus a `use BelongsTo`.

5. **c2 cap was a no-op in the playbook trace** (c2=100, walk-final=100, MIN=100). Cap structurally in place via the JOIN; will engage in scenarios where the walk's `levelBelow(cement_level)` would otherwise exceed the user's max correct level. Smoke trace doesn't exhibit such a case because reaching the cement level via step-up requires a correct answer at the step-below level, so c2 is always ≥ walk-final in normal flow. Cap is defensive — present as spec'd but rarely engages.

6. **`complated_at` typo on the READ side**: `$session->complated_at ?? now()` was always returning `now()` because `complated_at` doesn't exist as a column — so the typo was a silent no-op. Fix to `$session->completed_at` preserves the intended behavior (don't overwrite a previously-set completion timestamp). Verified column is `completed_at` (already correct on the WRITE side).

## Out of scope — follow-up needed

Logged here per the playbook's "log but don't fix" rule:

- The pre-existing `AssessmentSession` model had only an `attempts()` relation. It's plausible other code paths reference relationships that don't exist (`->test`, `->testType`, etc.). Worth an audit pass post-beta.
- `MaxileService`, `AdaptiveLevelService` reads from `user_*_levels`, `Test::firstOrCreateDiagnostic`, the picker rewrite — all confirmed still out of scope per playbook.

## Files changed

**Docs (commit `ed2a039`)**
- `docs/algorithms/maxile-and-question-selection.md` — §5.7 added after §5.6, §8 + §9 updated.
- `docs/algorithms/cc-implementation-diagnostic-walk.md` — the playbook itself, committed for traceability.
- `docs/algorithms/spec-patch-diagnostic-walk.md` — deleted as transport-only (was never tracked).

**Code (commit `a9cfc01`)**
- `app/Services/DiagnosticService.php` — counter reset, c2 cap, field_user write-through, typo, docstring.
- `app/Models/FieldUser.php` — `month_achieved` added to `$fillable`.
- `app/Models/AssessmentSession.php` — `user()` belongsTo relation added.

## Test plan

- [x] `php -l` clean on all edited files
- [x] Smoke trace from Task 2 verification passes (see above)
- [x] `field_user` row written with correct `field_maxile`, `month_achieved` (INT YYYYMM)
- [x] `users.maxile_level == AVG(field_user.field_maxile WHERE > 0)`
- [x] `result.overall_maxile` returns canonical maxile, not local DFP average
- [x] No prod writes (smoke ran inside `DB::beginTransaction` + `rollBack`)