# Verifier Evidence Reference Fidelity

## Background

ISS-007 came from end-to-end diagnosis cases where raw tool output and Executor `evidence_excerpt` contained enough facts, but Verifier still returned `LOW_CONFID` because the verifier-facing summary compressed away key details.

The affected flow is:

```text
chat_planner
  -> chat_executor
  -> VerifierInputHook / Gatekeeper
  -> chat_verifier
  -> chat_composer
```

The change hardens the evidence handoff between Executor, Gatekeeper, and Verifier.

## Goal

Make Executor cite concrete tool evidence, make Gatekeeper validate that citation with code, and make Verifier judge whether verified evidence can derive the claim.

## Scope

- Persist `tool_invocation.retrieval_details.evidence_refs`.
- Use `source_invocation_id + raw_path + evidence_excerpt` as the precise evidence binding.
- Add Gatekeeper `severity` and checked binding audit.
- Keep Gatekeeper in the Verifier hook path.
- Keep `tool_trace_summary` as navigation/audit context, not the only evidence source.
- Fix HikariCP mock positive/no-hit behavior.
- Tighten Executor/Verifier prompts for narrow-scope evidence handling.

## Non-goals

- No Planner `scope_contract`.
- No new database table.
- No full JSONPath engine.
- No change to external HTTP API.
- No retry rollback from Gatekeeper to Executor in this phase.

## OpenSpec

- Change: `openspec/changes/verifier-evidence-reference-fidelity`
- Source issue: `mvp/issues/archived/ISS-007-verifier-evidence-summary-fidelity.md`