I've been working on a GitHub Action that checks producers and consumers of APIs and catches mismatches in CI across repositories. Rather than contract testing, this uses SWC to extract the routes from express apps/mounted routers to find producers, and extracts async call code which it sends to an LLM to find consumers. It then extracts request and response types from both sides and runs a minimal TypeScript compiler pass using just those types to surface mismatches between services.

You just need to add the GitHub Action to your workflow. Run it on main to analyse deployed code, and on PRs to catch divergence before merging. It’s fast, low-effort to integrate, and I’m hoping it’ll help catch bugs early across services.

I'm looking for some beta testers that have Express microservices. If this sounds interesting, let me know - happy to chat or give you an API key to try it when send them out on the 18th - https://www.carrick.tools.

Repo - https://github.com/daveymoores/carrick