HN, OP here. I built this because I recently watched my LangChain agent burn through ~$50 of OpenAI credits overnight. It got stuck in a semantic infinite loop (repeating "I am checking..." over and over) which my basic max_iterations check didn't catch because the phrasing was slightly different each time. Realizing that "Pre-Flight" testing for agents is surprisingly hard, I built a small middleware API (FastAPI + LangChain) to automate this. What it does: It acts as an adversarial simulator. You send it your agent's system prompt, and it spins up a 'Red Team' LLM to attack it. Currently checks for: Infinite Loops: Semantic repetition detection. PII Leaks: Attempts social engineering ('URGENT AUDIT') to force the agent to leak fake PII, then checks if it gets blocked. Prompt Injection: Basic resistance checks. Tech Stack: Python, FastAPI, Supabase (for logs). It's open-source and I hosted a live instance on Render if you want to try curl it without installing: https://agentic-qa-api.onrender.com/docs Would love feedback on what other failure modes you've seen your agents fall into!