GPT-5.5 Released via OpenAI Codex with Subscription Access

OpenAI has released GPT-5.5, available in Codex and rolling out to paid ChatGPT subscribers, with API access promised soon. The model is described as fast and highly capable by Simon Willison, who had preview access. A notable omission is the API, which requires additional safety work. The release occurs amid tensions between AI agent harnesses like OpenClaw and API providers. OpenClaw was blocked by Anthropic from integrating with subscriptions, but OpenAI, having hired OpenClaw creator Peter Steinberger, welcomed continued integration via the same mechanism used by their open-source Codex CLI tool. OpenAI's Romain Huet confirmed official support for using Codex with ChatGPT subscriptions across various platforms. Willison created a plugin, llm-openai-via-codex, that uses the Codex subscription to run prompts. He tested GPT-5.5 with a pelican benchmark, noting that higher reasoning effort (xhigh) produced a more CSS-heavy SVG with 9,322 reasoning tokens versus 39 for default. The post was published on 23rd April 2026.