Braintrust and Basis open-sourced Trajectory Behavior Specs, a Markdown-based standard designed to evaluate hundreds of intermediate decision steps in long-horizon agents against production traces.

Key Takeaways

  • Moves beyond binary end-result evaluation to assess step-by-step decision quality across long trajectories;
  • Markdown-based specification language bridges product requirements and automated LLM judge prompts;
  • Continuously tests production traces against specs to generate automated regression suites during agent refactoring.