# Brief: evidence-trace-hardening

## Background

The MVP already has persisted tool traces and a verifier, but the evidence contract is still only partially standardized. For interview-focused hardening, the project now needs a tighter contract for evidence persistence, no-evidence / failure semantics, and degraded-output behavior.

## Goals

1. Standardize the persisted evidence-tool contract across `lookup_knowledge`, `query_logs`, and `query_metrics`.
2. Make verifier-facing summaries distinguish failed calls, no-hit calls, deduped retrievals, and actual supporting evidence.
3. Add offline tests for verifier fallback and degraded-output paths.

## Scope

- `ToolInvocationRecorder`
- `LookupKnowledgeTool`
- `QueryLogsTools`
- `QueryMetricsTools`
- `ToolTraceSummaryService`
- `ChatService`
- Focused offline tests

## Non-Goals

- No new API or schema
- No evaluation harness yet
- No trace UI
- No security/config cleanup

## Related OpenSpec

`openspec/changes/evidence-trace-hardening/`