OpenAI's evals platform deprecation, Agent Builder shutdown, and v1/prompts API removal all land November 30, 2026. Here's what operators need to migrate and how the routing layer absorbs the gap.
OpenAI published a detailed guide on designing trustworthy third-party evaluations. The key operator lesson: harness choice changes measured capability, so benchmark scores require context before they can inform routing tier decisions.
Codex eval infrastructure separates a working agent from a self-improving one. OpenAI's Tax AI converted production traces into eval targets and ran Codex-driven iterations automatically. The architecture applies to any team building agents on an API gateway.
