OpenAI releases GPT-5.5 and GPT-5.5 Pro in the API

Changelog

April, 2026

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, including through Batch, 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. GPT-5.5 defaults to medium reasoning effort.

Released GPT Image 2, a state-of-the-art image generation model for image generation and editing. GPT Image 2 supports flexible image sizes, high-fidelity image inputs, token-based image pricing, and Batch API support with a 50% discount.

Updated the Agents SDK with new capabilities, including:

• running agents in controlled sandboxes;
• inspecting and customizing the open-source harness; and
• controlling when memories are created and where they're stored.

March, 2026

Released GPT-5.4 mini and GPT-5.4 nano to the Chat Completions and Responses API. GPT-5.4 mini brings GPT-5.4-class capabilities to a faster, more efficient model for high-volume workloads, while GPT-5.4 nano is optimized for simple high-volume tasks where speed and cost matter most.

GPT-5.4 mini supports tool search, built-in computer use, and compaction. GPT-5.4 nano supports compaction, but does not support tool search or computer use.

Updated our image encoder to fix a small bug with input_image inputs in GPT-5.4. Some image understanding use cases may now see improved quality. No action is required.

Expanded the Sora API with reusable character references, longer generations up to 20 seconds, 1080p output for sora-2-pro, video extensions, and Batch API support for POST /v1/videos. 1080p generations on sora-2-pro are billed at $0.70 per second.

Released GPT-5.4, our newest frontier model for professional work, to the Chat Completions and Responses API, and released GPT-5.4 pro to the Responses API for tougher problems that benefit from more compute.

Also released:

• Tool search in the Responses API, which lets models defer large tool surfaces until runtime to reduce token usage, preserve cache performance, and improve latency.
• Built-in Computer use support in GPT-5.4 through the Responses API computer tool for screenshot-based UI interaction.
• A 1M token context window and native Compaction support for longer-running agent workflows.