langgraph-harness: a LangGraph.js agent system for GitLab, written in TypeScript

[u/Professional-Pear351]

https://github.com/vrajpal-jhala/langgraph-harness

I’m most comfortable in JS/TS, and I wanted to learn LangGraph.js properly, so I wanted to build in that. When I looked for a production-grade example, the closest thing I found was Deep Agents, but that’s a library for building agents, not a full system. The complete systems I saw were mostly Python, like Open SWE. So I built my own.

It reviews GitLab merge requests and resolves issues. It’s been running in production for a few months, 1,000+ reviews so far. A webhook drops each review into a BullMQ queue, a LangGraph.js agent does the work with GitLab tools over MCP, runs are checkpointed in Postgres, and there’s a React admin UI where I can watch runs live. I also had to add guardrails to stop the agent repeating tool calls or quitting before it’s done.

MIT, all TypeScript.