ModelClock
API availability
Available in the API since Apr 24, 2026
OpenAI announced API availability for this model on 2026-04-24. API: v1/responses · API: v1/chat/completions · API: v1/batch
This date applies to API availability. Rollouts in consumer products or other hosting routes can happen on different dates.
- Hosting route
- First-party API
- Affected scope
- API: v1/responses · API: v1/chat/completions · API: v1/batch
- Announced
- Apr 24, 2026
- First seen by ModelClock
- Oct 3, 2026
What the provider published
developers.openai.com ↗Released GPT-5.5, a new frontier model for complex professional work, to the Chat Completions and Responses API, and released GPT-5.5 Pro for Responses API requests for tougher problems that benefit from more compute.
Read from the provider's text; the quote is the provider's exact lines.