Codex 1 in this material In the captured interview with OpenAI's Codex product team, Codex 1 is introduced as the custom model powering OpenAI Codex — a tuned version of o3 trained specifically for agentic coding work.[^ceebdf5b-d543-5073-becc-f4bfbb1dcabf@382] It is the model behind the interview's central claims about Codex's behavior: producing reviewable diffs, writing honest summaries, and supplying deterministic log citations so a human can verify what the agent actually did.[^ceebdf5b-d543-5073-becc-f4bfbb1dcabf@382] Why the tuning matters The interview frames Codex 1 not as a general chat model but as one shaped for a delegation-first workflow: tasks are handed off whole, run in a locked-down container, and come back as changes a developer can inspect rather than conversations to babysit. The tuning goal is trust through verifiability — the model's output is meant to be checked, not taken on faith.[^ceebdf5b-d543-5073-becc-f4bfbb1dcabf@382]