# diagnosis-eval-harness Specification

## Purpose
Provide a repeatable offline evaluation harness for MVP diagnosis Agent behavior, so prompt, tool, retrieval, and verifier changes can be checked against fixed trace-based regression cases.

## Requirements

### Requirement: Evaluation harness SHALL define fixed diagnosis cases
The system SHALL provide a small fixed set of MVP diagnosis evaluation cases with explicit expected trace and answer criteria.

#### Scenario: Case definition includes expected evidence
- **WHEN** an evaluation case is defined
- **THEN** it SHALL include a case id, user question, expected root-cause keywords, required evidence tools, and allowed verifier verdicts

#### Scenario: Case definition can express forbidden behavior
- **WHEN** a case has known unsafe behavior
- **THEN** the case definition SHALL be able to declare forbidden answer keywords or forbidden verdicts

### Requirement: Evaluation harness SHALL validate diagnosis traces
The system SHALL validate a diagnosis trace against the corresponding case definition using deterministic rules.

#### Scenario: Evidence coverage validation
- **WHEN** a trace is evaluated
- **THEN** the evaluator SHALL verify that required evidence tools appear in `toolInvocations` or verifier trace summaries

#### Scenario: Verifier evaluation validation
- **WHEN** a trace is evaluated
- **THEN** the evaluator SHALL verify that `selfEvaluation.verifier_evaluation.verdict` exists
- **AND** the verdict SHALL be one of the case's allowed verdicts

#### Scenario: Answer keyword validation
- **WHEN** a trace is evaluated
- **THEN** the evaluator SHALL verify that the final answer includes at least the configured minimum root-cause keyword coverage

#### Scenario: Degraded output validation
- **WHEN** a trace verdict is `REJECT`
- **THEN** the evaluator SHALL verify that the final answer follows the degraded-output contract rather than leaking an unverified executor answer

### Requirement: Evaluation harness SHALL report quality and cost signals
The system SHALL produce a report that summarizes pass/fail results and key trace metrics.

#### Scenario: JSON report output
- **WHEN** an evaluation run completes
- **THEN** the evaluator SHALL output a JSON report with per-case result, failed checks, verdict, evidence coverage, tool-call count, and duration

#### Scenario: Markdown report output
- **WHEN** an evaluation run completes
- **THEN** the evaluator SHALL output a Markdown report suitable for review in the repository

#### Scenario: Aggregate metrics
- **WHEN** multiple cases are evaluated
- **THEN** the report SHALL include aggregate pass rate, verdict distribution, average tool-call count, and average duration when available

### Requirement: Evaluation harness SHALL support offline fixture mode
The first evaluator version SHALL be runnable without live MySQL, Redis, Milvus, or LLM services by evaluating saved trace fixtures.

#### Scenario: Fixture trace evaluation
- **WHEN** the evaluator is run against a directory of trace fixture files
- **THEN** it SHALL evaluate each trace file against its matching case definition
- **AND** it SHALL not require a running application service

#### Scenario: Missing fixture is reported clearly
- **WHEN** a case has no matching trace fixture
- **THEN** the evaluator SHALL mark the case as not run or failed with a clear reason

### Requirement: Evaluation harness SHALL provide complete fixture coverage for fixed cases
The system SHALL include an offline trace fixture for every fixed MVP diagnosis evaluation case.

#### Scenario: Every case resolves to a fixture file
- **WHEN** the evaluator loads the fixed case definition file
- **THEN** every case's `traceFixture` value SHALL resolve to an existing JSON fixture file

#### Scenario: Fixture files are loadable as diagnosis traces
- **WHEN** each referenced fixture is loaded
- **THEN** it SHALL deserialize into the trace response shape used by the evaluator

### Requirement: Evaluation harness SHALL preserve a reproducible baseline report
The system SHALL preserve a generated baseline report for the full fixed fixture set.

#### Scenario: Baseline report includes all fixed cases
- **WHEN** the baseline report is generated from the fixed case file and fixture directory
- **THEN** the report SHALL include one result for every fixed case

#### Scenario: Baseline report is reviewable
- **WHEN** the baseline report is written
- **THEN** it SHALL be available in JSON and Markdown formats under the eval documentation area

#### Scenario: Baseline regeneration is documented
- **WHEN** a developer changes fixtures or evaluator rules
- **THEN** the eval documentation SHALL explain how to regenerate the baseline report

### Requirement: Evaluation harness SHALL compare reports against a baseline
The system SHALL compare a current diagnosis evaluation report against a saved baseline report using deterministic rules.

#### Scenario: Aggregate regression detection
- **WHEN** the current report has a lower pass rate than the baseline report
- **THEN** the diff SHALL record a regression with the old value, new value, and delta

#### Scenario: Cost signal detection
- **WHEN** average tool-call count or average duration changes between reports
- **THEN** the diff SHALL record the baseline value, current value, and delta

#### Scenario: Verdict distribution comparison
- **WHEN** verdict counts differ between reports
- **THEN** the diff SHALL record the verdict distribution changes

### Requirement: Evaluation harness SHALL compare case-level report results
The system SHALL compare case results by case id and report actionable per-case changes.

#### Scenario: Case pass/fail regression
- **WHEN** a case changes from passing in the baseline to failing in the current report
- **THEN** the diff SHALL record a regression for that case

#### Scenario: Evidence coverage regression
- **WHEN** a required evidence tool changes from covered to uncovered for a case
- **THEN** the diff SHALL record a regression naming the case and tool

#### Scenario: Missing case detection
- **WHEN** a baseline case is absent from the current report
- **THEN** the diff SHALL record a regression for the missing case

#### Scenario: New case detection
- **WHEN** a current report contains a case absent from the baseline
- **THEN** the diff SHALL record the case as a non-regression change

### Requirement: Evaluation harness SHALL report baseline diff results
The system SHALL expose baseline diff output in structured JSON and reviewable Markdown formats.

#### Scenario: JSON diff output
- **WHEN** a baseline diff is written as JSON
- **THEN** it SHALL include aggregate summary fields and detailed diff items

#### Scenario: Markdown diff output
- **WHEN** a baseline diff is written as Markdown
- **THEN** it SHALL include a readable summary and a table of diff items