# Experiment 57J.80 — Incremental Meaning on Existing Uncertainty (Pre-Anchored)

**Branch:** `feature/semantic-action-contract-v0.23`
**Starting HEAD:** `ce01e70` (tooling: add pre-anchored update-only mode to canonical harness)

## Objective

Answer exactly:

> When the savings-realism uncertainty already exists and the user supplies new concrete information relevant to it, does the model emit `structuralActionRequired=true`, preserve that new information structurally, and avoid creating a duplicate equivalent uncertainty?

## Hypothesis

The answer contains both:
- **existing unresolved meaning:** uncertainty about whether the savings estimate is realistic
- **new supported information:** approximately £2 million per year, basis = eliminating the current lease cost

Expected valid contract path: `structuralActionRequired = true`, meaningful mutation, new info preserved, existing uncertainty identity preserved (single node).

## Configured scenario (from fixture)

```text
"We are considering relocating the engineering team to reduce operating costs."
```

## Configured answer (fixed)

```text
"The projected office saving is about £2 million per year based on eliminating the current lease cost, but I am still unsure whether that estimate is realistic."
```

## Pre-anchored fixture

```text
tests/fixtures/pre-anchored-update-savings-realism.json
```

**Savings-realism node:**
- id: `n_savings_realism`
- label: "Are the projected office savings from relocation realistic?"
- status: `unknown`

**Exactly one equivalent unresolved uncertainty before Update: YES**

## Run

### CALL ACCOUNTING

- startCalls: 0
- updateCalls: 1
- totalCalls: 1
- Retries: 0
- Supplementary scripts: NO

### UPDATE 1

- HTTP status: 400
- Stage: `request_validation`
- Validation errors: `[{"path":["previousQuestion"],"message":"Expected string, received null","code":"invalid_type"}]`
- structuralActionRequired: UNAVAILABLE

**Result:** Update rejected at request_validation before any model inference call. The harness passed `previousQuestion: null` (correct for update-only mode with no Start), but the production server's Zod validation requires `previousQuestion` to be a string.

## Classification: I — BLOCKED

The committed FIXTURE_MODE=updateOnly path fails before the model call due to a request_validation boundary condition: no prior Start means no selectedQuestion, and the server does not accept null for previousQuestion in update-only mode. The apparatus works (fixture loads, anchor verified, exactly one Update attempted), but cannot reach the model inference stage.

## What this establishes

- FIXTURE_MODE=updateOnly apparatus correctly verifies fixture integrity
- One update call is attempted even when blocked at validation
- Call accounting reports accurately
- Pre-anchored harness from 57J.78 requires a non-null previousQuestion string to reach the model inference stage

## What this does NOT prove

- Whether the model would produce structuralActionRequired=true for incremental meaning on existing uncertainty
- Whether new £2m/year information would be structurally preserved
- Whether lease-cost basis would be represented
- Whether duplicate uncertainty identity is avoided

## Production code changed: NO