Simon Willison’s Weblog

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25th April 2026

Since GPT-5.4, we’ve unified Codex and the main model into a single system, so there’s no separate coding line anymore.

GPT-5.5 takes this further, with strong gains in agentic coding, computer use, and any task on a computer.

Romain Huet, confirming OpenAI won't release a GPT-5.5-Codex model

This is a quotation collected by Simon Willison, posted on 25th April 2026.