confidence-engine/docs/experiment-57j81.md

Experiment 57J.81 — Update-Only Previous Question Fix

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

Objective

Fix the 57J.80 defect: update-only mode sends previousQuestion = null, which the production Zod validator rejects with "Expected string, received null" at request_validation stage, blocking all model inference.

Defect Source

When FIXTURE_MODE=updateOnly, the harness sets selectedQuestion = null (line 242 of reproduce-multi-turn-investigation.mjs) and then passes it as previousQuestion to the Update request. The production validation schema (lib/graph/schema.js:207) requires previousQuestion: z.string().min(1).

Fix

Source of previousQuestion: FIXTURE ANCHOR (derived from committed fixture, not a hardcoded duplicate).

The pre-anchored fixture already contains the exact question text in two locations:

• unresolved_question at the fixture level (snake_case, from JSON)
• The anchor node's label field on n_savings_realism

Change in harness (scripts/reproduce-multi-turn-investigation.mjs):

let selectedQuestion = fixtureData.unresolved_question ?? savingsNode.label;

This replaces let selectedQuestion = null; — both the harness and its test simulation now derive previousQuestion from the committed savings-realism anchor.

Exact previousQuestion: "Are the projected office savings from relocation realistic?"

Classification: A — FIX VALIDATED (tooling only)

One tooling commit fixes the boundary condition. The pre-anchored fixture already contains the required question string; no production code, prompts, or schemas changed.

Tests added

1. Direct assertion that previousQuestion is a non-empty string
2. Direct assertion that previousQuestion matches the committed savings-realism anchor exactly
3. Direct assertion of exact fixture graph transmission (replaces indirect node-count check)
4. Direct assertion of exact ANSWER_2 in request body
5. Explicit zero-HTTP-call guard for missing ANSWER_2

All 49 harness tests pass. Zero Ollama calls. Zero live API calls.

What this enables

The update-only apparatus can now reach the production Update path without requiring a prior Start call. Experiment 57J.80's incremental-meaning test case is unblocked and ready to run against the model inference stage.

Production code changed: NO

Ollama calls: 0

Live API calls: 0