What Happened
On 2026-04-23, OpenAI began rolling out GPT-5.5 and GPT-5.5 Pro in ChatGPT, with GPT-5.5 also available in Codex.
Why It Matters
The release pushed the mainline model toward completing ambiguous, multistep work across tools rather than only producing standalone responses. Its significance lies in the cumulative shift from answering requests to maintaining a task across research, execution, and verification. The different product and API dates also document how frontier models can reach users in stages.
Technical Details
OpenAI reported gains on agentic coding, computer-use, professional-work, and scientific-analysis evaluations. The launch page distinguishes the initial April 23 product rollout from API availability: GPT-5.5 and Pro reached the API on April 24, according to its dated update.