observability

Investors have poured serious capital into agent evaluation, observability and benchmarking. **Braintrust** raised **$80M at $800M**, **LangChain** **$125M at $1.25B**, **LMArena** **$100M then $150M at $1.7B**, **Patronus** a fresh **$50M Series B** on June 25. The product they sell is a number. The research says the number is broken: up to **100%** relative error on agent benchmarks, **27** private variants gaming one leaderboard, and a 1MB blind script beating frontier agents.