LLM Eval Suites 2026: Promptfoo, Braintrust & Regression Gates
LLM evals are the new unit tests: this 2026 guide compares Promptfoo and Braintrust and shows how to wire regression gates that catch model drift before it...
Chapter 1: Why LLM Evals Are the New Unit Tests If you shipped software in the last decade, you internalized a simple contract: write a function, write a test, watch it go green, and trust that green forever. The test asserted add(2, 2) === 4, and it would keep asserting that until the heat death of the universe or until someone changed the code. That contract is the bedrock of modern engineering. It is also completely broken the moment you put a large language model in your call stack. Here is the uncomfortable truth every team building on LLMs in...