Experiences with GPT-5-Codex - Applied Mathematics Consultingwww.johndcook.com › blog › 2025/10/16 › experiences-with-gpt-5-codex

Also, some have reported that the new Claude Sonnet 4.5 runs much faster, though Codex is being continually improved. Obviously to be effective, these models must have access to adequate test case coverage, to enable the models to debug against. Without this, the coding agent can get really lost.