Summary of METR's predeployment evaluation of GPT-5.6 Sol

Note on independence: This evaluation was conducted under a standard NDA. Due to the sensitive information shared with METR as part of this evaluation, OpenAI’s comms and legal team required review and approval of this post. 1 Summary We conducted an independent external evaluation of GPT-5.6 Sol. For this evaluation, OpenAI provided: Access to GPT-5.6 Sol, both the final checkpoint and a ‘railfree’ version, via API Access to GPT-5.6 Sol with raw chain-of-thought via API A “Codex harness setup guide for third-party assessors” Updated answers to key claims from our pilot Frontier Risk Report qu