← ChatGPT & Codex changelog

OpenAI API — September, 2026

This release introduces GPT-6 Astra, our most capable model, designed for complex end-to-end tasks like reasoning, coding, and research, with enhanced controls for long-running work. New GPT Image 2.5 Sunburst and Flare models provide advanced image generation and editing capabilities for both precision and speed. API improvements include refined error handling for rate limits and server load, along with IPv6 support. Developers benefit from these powerful new models and tools for building more robust and sophisticated AI applications.

Added

  • Released GPT Image 2.5 Sunburst and GPT Image 2.5 Flare for image generation and editing through the Image API and the Responses API image generation tool.
  • Use Sunburst for workflows where editing precision matters most, or Flare for fast, high-quality everyday image generation. Both models support the new xhigh and max quality settings and use GPT Image 2 token rates. See the image generation guide and pricing.
  • Released GPT-6 Astra, our most capable model, built for the hardest end-to-end work.
  • Added new controls for long-running work with GPT-6 Astra in the Responses API:

Changed

  • Use GPT-6 Astra for reasoning, coding, computer use, research, and document creation. It combines these capabilities to carry complex tasks from an initial request to a finished result, using the context and tools you provide.
  • Key changes to consider when migrating:
  • GPT-6 Astra does not support the none reasoning effort level.
  • GPT-6 Astra does not support custom temperature or top_p values or log probabilities (logprobs).
  • Tool calling requires the Responses API. If you use tools with Chat Completions, follow the Responses migration guide.
  • Misalignment monitoring asynchronously checks for potential issues during agent work in supported Responses API requests. Checks can trigger safety alerts or stop a conversation for review.
  • Start with Using GPT-6 Astra for capabilities, prompting, and migration guidance. Explore computer use for browser and desktop workflows, and see pricing for available inference tiers.
  • Async tool calling: Let the model continue working while your application runs function or custom tools, then return results as they become available.
  • Mid-turn steering: Send additional instructions while a response is in progress over WebSockets, so the model can incorporate corrections or changing requirements.
  • Change reasoning effort mid-conversation: Increase effort for difficult work or reduce it for routine follow-ups while preserving the cached prompt prefix.
  • Updated API errors so applications can distinguish traffic that increases too quickly from temporary model overload.
  • Traffic that increases too quickly can return a 429 error with the slow_down code. Temporary model overload returns a 503 error with the server_is_overloaded code. Both responses may include Retry-After. When the header is present, wait at least as long as it specifies before retrying. If it's missing, use exponential backoff. See the error codes guide and rate limits guide.
  • Connections to api.openai.com can now use IPv6.