API Contract Verification

Compare an API specification (OpenAPI, GraphQL schema, protobuf) against the actual implementation, flag drift, and optionally generate fixes.

Workflow

runPipeline(
  pipe(
    all(parseAPISpec, analyzeImplementation),
    compareContracts,
    forEach(classifyDrift).then(
      branch({
        Breaking: forEach(generateFix),
        NonBreaking: drop,
      })
    ),
  ),
);

Stages

1. Parallel extraction — parse the API spec and analyze the implementation concurrently.
2. Compare — diff the declared contract against the actual behavior. Output: list of discrepancies.
3. Classify — for each discrepancy, determine if it's a breaking change or non-breaking drift.
4. Fix breaking changes — generate patches for breaking discrepancies. Non-breaking drift is logged but not fixed.

Key points

• The spec parser is deterministic (no LLM) — it reads the OpenAPI/protobuf file and outputs structured data.
• The implementation analyzer uses an LLM to read route handlers and extract the actual request/response shapes.
• forEach processes all discrepancies concurrently.
• The fix generator sees one discrepancy at a time with focused context.