# Executor Composer Final Answer

## Background

Stages one to three moved the Chat diagnosis chain to structured Executor output, deterministic Gatekeeper validation, and Verifier `claim_checks`.

Before this stage, `ChatService` still owned final answer rendering. PASS paths could use a temporary V2 renderer, while LOW_CONFID and REJECT paths used templates. That left final user-facing expression too close to Executor material and made it harder to prove that only Verifier-allowed claims reached the user.

## Goal

Add a Composer expression layer after Verifier:

```text
chat_planner
  -> chat_executor
  -> VerifierInputHook + Gatekeeper
  -> chat_verifier
  -> chat_composer
  -> final answer
```

Composer produces user-facing answers from filtered material only:

- `allowed_claims`
- `allowed_hypotheses`
- `missing_info`
- `recommended_actions`
- `rationale`

## Scope

- Added `chat-composer-prompt.md`.
- Added `chat_composer` Agent construction in `ChatService`.
- Added Composer input filtering from Verifier decision and Executor structured output.
- Replaced PASS temporary V2 renderer usage with Composer-or-safe-fallback rendering.
- Routed LOW_CONFID and REJECT final answers through Composer when Verifier output is valid.
- Added deterministic fallback for malformed Composer output.
- Persisted `composer_output` under `diagnosis_session.self_evaluation.verifier_evaluation`.
- Updated sequential workflow tests.

## Non-Goals

- No Planner changes.
- No Executor retry changes.
- No Gatekeeper rule expansion.
- No Verifier classification expansion.
- No database schema migration.
- No stage-five eval fixture expansion.

## OpenSpec

- Active change before archive: `openspec/changes/executor-composer-final-answer`
- Capabilities: `chat-composer-agent`, `chat-verifier-agent`
- Scale: standard