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 ↗Feature · Model: gpt-5.5 · Model: gpt-5.5-pro · API: v1/responses · API: v1/chat/completions · API: v1/batch
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.
GPT-5.5 supports a 1M token context window, image input, structured outputs, function calling, prompt caching, Batch, tool search, built-in computer use, hosted shell, apply patch, Skills, MCP, and web search. Key updates include:
- Reasoning effort now defaults to
medium.- When
image_detailis unset or set toauto, the model now uses original behavior.
Read from the provider's text; the quote is the provider's exact lines.
