# Proposal: executor-evidence-output-contract

## Why

Recent Chat diagnosis sessions frequently end as `LOW_CONFID` even though evidence tools were called successfully. The main failure mode is not missing tool execution; it is that Executor blends tool evidence, runbook/reference patterns, and model inference into one natural-language answer, then presents unsupported details as confirmed incident facts.

Verifier currently receives `original_query`, `executor_final_answer`, `tool_trace_summary`, and optional `retry_context`. It can catch unsupported claims, but it must first infer facts from unstructured prose. That makes the quality gate reactive and noisy: unsupported claims are detected after the answer has already been shaped as a confident story.

## What Changes

- Update the Chat Executor prompt so its final output follows a strict evidence-attribution JSON contract.
- Require confirmed claims to carry explicit evidence bindings and require unsupported items to be placed in `hypotheses`, `missing_info`, or `recommended_actions` instead of confirmed conclusions.
- Extend the verifier input contract with a parsed or raw `executor_structured_output` field while preserving the existing `executor_final_answer` field for fallback compatibility.
- Update the Chat Verifier prompt so it prefers Executor-provided structured claims over natural-language fact extraction.
- Keep Verifier isolated from Planner/Executor intermediate reasoning; it still receives only the original query, Executor final output, structured claim contract, tool trace summary, and retry context.
- Do not change evidence tool signatures, database schema, or the `Planner -> Executor -> Verifier` topology.

## Capabilities

### New Capabilities

None.

### Modified Capabilities

- `chat-verifier-agent`: Chat verification now consumes an Executor evidence-attribution contract when available.

## Impact

- Affected prompts: `chat-executor-prompt.md`, `chat-verifier-prompt.md`.
- Affected integration: `VerifierInputHook` or equivalent verifier payload assembly must include `executor_structured_output` when Executor returns valid structured JSON.
- Affected parsing: `ChatService` may parse Executor output to separate machine contract from user-facing text, with fallback when parsing fails.
- Affected tests/eval: prompt contract tests, verifier input assembly tests, and unsupported-claim regression fixtures.
- No database schema change is required. Structured Executor output can be persisted in existing step output fields and verifier snapshots.

## Out Of Scope

- Loosening Verifier scoring or `PASS` criteria.
- Raising `verifier.low-confidence-threshold` to hide unsupported claims.
- Treating runbook, skill, or historical case text as current incident evidence unless it was returned as evidence for the current query and bound explicitly.
- Adding a new verifier tool or allowing Verifier to perform retrieval.
- Replacing the existing tool trace summary contract.