GPT-5.5 changelog

OpenAI models available in Amazon Bedrock

GPT-5.4 and GPT-5.5 became available in Amazon Bedrock through an OpenAI-compatible Responses API endpoint, with models and features varying by AWS Region.

GPT-5.5 and GPT-5.5 Pro released in the API

GPT-5.5 shipped to the Chat Completions and Responses APIs, with GPT-5.5 Pro on the Responses API. Reasoning effort defaults to medium, and caching for GPT-5.5 only works with extended prompt caching.

Who is affected:

Developers choosing a frontier OpenAI model on the API.

What to do:

Test GPT-5.5 against your current model. Note that in-memory prompt caching is not supported.

GPT-5.5 available in Codex and recommended for most tasks

GPT-5.5 became available in Codex as the recommended choice for most Codex tasks once it appears in the model picker.

Who is affected:

Codex users.

What to do:

Select gpt-5.5 in Codex.