# CU Synthesis Experiment Apparatus — Iteration 3

## Purpose

Deterministic experiment helper for invoking the production `synthesizeCurrentUnderstanding()` function with fixed local input fixtures, without live model calls.

## Files

| File | Role |
|------|------|
| `scripts/current-understanding-experiment-helper.cjs` | Standalone helper (CJS + dynamic import ESM) |
| `tests/graph/current-understanding-experiment-helper.test.js` | Deterministic verification (14 tests, 0 live calls) |

## Usage

### Helper (CLI)

```bash
node scripts/current-understanding-experiment-helper.cjs --file fixtures/cu-synthesis.json
```

Fixture contract: `{ situationGraph: object, findings: array }`

### Test

```bash
npx vitest run tests/graph/current-understanding-experiment-helper.test.js --environment=node
```

## Existing Mechanics Reused

- Dynamic `import()` seam from CJS to ESM (proven in `scripts/overview-experiment-helper.cjs` line 64)
- Environment loading via `@next/env` `loadEnvConfig` (proven in both existing helpers)
- `.env.local` ownership of `OLLAMA_BASE_URL` and `OLLAMA_MODEL` preserved — helper reads from `process.env`, never writes
- Deterministic inline test double provider pattern (mirrors `makeFakeProvider` in `tests/graph/current-understanding-synthesis.test.js`)

## Production Entry Point

`synthesizeCurrentUnderstanding()` from `lib/graph/current-understanding-synthesis.js`

Input contract: `{ situationGraph: object, findings: array }`
Optional deps: `{ provider: object, modelName: string }`

Output: `{ currentUnderstanding: string }`

## Verification Results

All 14 deterministic tests PASS. Zero live model calls. The following invariants verified:
- Fixed compatible input reaches `synthesizeCurrentUnderstanding()`
- Expected structured output `{ currentUnderstanding }` captured
- Prompt includes revised Rule 2 boundary text ("Do not introduce or describe open questions...")
- Exactly one synthesis invocation per run
- Input fixture is not mutated (deep clone + compare)
- No persistence/Supabase/DB operations

## Iteration 4 — Regression Fixture

Fixture path: `tests/fixtures/current-understanding-original-investigation.json`

Source: authenticated GET `/api/investigations/6b080d97-033e-477b-9d41-7b2f4f04bbed` (2026-10-08)

Contract: `{ situationGraph: object, findings: array }`

Contents:
- `situationGraph`: 11 nodes (1 state, 5 observation, 2 metric, 3 unknown), 10 edges, full `reasoningState`, `resolvedNodeIds`, `centralStatement`, `activeUnknownNodeId`
- `findings`: 9 findings total; all 7 previously verified IDs present (`hciikc`, `ybfsm3`, `k45vyt`, `vhftyr`, `9bgkmw`, `23192q`, `kkh39k`)

Verified: helper parses without invoking live synthesis; fixture immutability confirmed via deep-clone roundtrip.