Add diagnosis eval baseline diff

devflow/projects/2026-07-05-diagnosis-eval-baseline-diff/acceptance.md

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+# Acceptance: diagnosis-eval-baseline-diff
+
+## Classification
+
+standard-light
+
+## Task Status
+
+| Task | Status | Notes |
+| --- | --- | --- |
+| Issue and OpenSpec setup | Done | Created slug-based issue and initial OpenSpec artifacts. |
+| Implementation | Done | Added diff model, comparator, writer, docs, sample outputs, and focused tests. |
+| Verification | Done | Diff/evaluator tests, compile verification, and OpenSpec validation passed. |
+
+## Current State
+
+- Baseline diff is implemented for aggregate metrics, verdict distribution, case-level state, keyword coverage, evidence coverage, missing cases, and new cases.
+- JSON and Markdown diff output are available.
+- No production runtime behavior has been changed.
+
+## Verification
+
+### Script Verification
+
+- Command: `mvn -q "-Dtest=DiagnosisEvalBaselineDiffTest" test`
+- Result: passed
+- Notes: Also verified with `DiagnosisTraceEvaluatorTest`.
+
+### Static Verification
+
+- Command: `mvn -q -DskipTests compile`
+- Result: passed
+
+### OpenSpec Verification
+
+- Command: `openspec validate diagnosis-eval-baseline-diff --strict`
+- Result: passed

devflow/projects/2026-07-05-diagnosis-eval-baseline-diff/brief.md

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+# Brief: diagnosis-eval-baseline-diff
+
+## Background
+
+The eval harness now has a complete saved baseline. This change adds the comparison layer that turns the baseline into an actionable regression signal.
+
+## Goals
+
+1. Compare baseline and current `DiagnosisEvalReport` objects.
+2. Detect aggregate and per-case regressions.
+3. Output JSON and Markdown diff reports.
+4. Document how to read the diff in interview and engineering terms.
+
+## Scope
+
+- Diff data structures
+- Deterministic report comparison
+- JSON / Markdown diff output
+- Focused tests and eval docs
+
+## Non-Goals
+
+- No live Agent execution
+- No LLM-as-judge
+- No evaluator scoring rule changes
+- No production API changes
+
+## Related OpenSpec
+
+`openspec/changes/diagnosis-eval-baseline-diff/`

devflow/projects/2026-07-05-diagnosis-eval-baseline-diff/decisions.md

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+# Diagnosis Eval Baseline Diff Decisions
+
+## Clarify
+
+- Entry summary: add report diffing on top of the completed diagnosis eval baseline.
+- Slug: `diagnosis-eval-baseline-diff`
+- Devflow scale: standard-light
+
+## Context
+
+- `diagnosis-eval-harness` created deterministic fixture evaluation.
+- `expand-diagnosis-eval-fixtures` created a complete saved baseline.
+- This change compares new reports against that baseline.
+
+## Key Decisions
+
+- Decision: Diff report DTOs instead of raw traces.
+  - Reason: the report is the stable contract for regression review.
+
+- Decision: Use deterministic code rules instead of LLM-as-judge.
+  - Reason: baseline regression checks should be repeatable and explainable.
+
+- Decision: Output both JSON and Markdown.
+  - Reason: JSON supports automation; Markdown is useful in reviews and interviews.
+
+## Open Questions
+
+- Whether a future change should expose this through a CLI or Maven goal.

devflow/projects/2026-07-05-diagnosis-eval-baseline-diff/evidence.md

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+# Evidence: diagnosis-eval-baseline-diff
+
+## Evidence Log
+
+- 2026-07-05: Created slug-based issue `diagnosis-eval-baseline-diff.md`.
+- 2026-07-05: Created OpenSpec change `diagnosis-eval-baseline-diff`.
+- 2026-07-05: Added baseline diff DTOs, deterministic comparer, and JSON / Markdown writer.
+- 2026-07-05: Added sample baseline diff JSON and Markdown reports.
+- 2026-07-05: Verification passed with `mvn -q "-Dtest=DiagnosisEvalBaselineDiffTest,DiagnosisTraceEvaluatorTest" test`.
+- 2026-07-05: Verification passed with `mvn -q -DskipTests compile`.
+- 2026-07-05: Verification passed with `openspec validate diagnosis-eval-baseline-diff --strict`.