Highest-intelligence API option in the GPT-5.5 family. Use for the most challenging problems that require maximum reasoning depth and can tolerate higher latency. Supports full reasoning effort range from none to xhigh.
- Highest-intelligence API option for the most challenging problems requiring maximum reasoning depth.
- Configurable reasoning effort (none → xhigh) optimized for complex multi-step analytical tasks.
- Supports a 1,050,000-token context window and up to 128,000 max output tokens.
- Full tool support including web search, image generation, file search, and MCP.
- Pricing is $30.00 per 1M input tokens and $180.00 per 1M output tokens.
Web Search
Search the web for current info.
JSON Mode
Output responses in valid JSON format.
Image Generator
Generate images from text prompts.
Model Information
Supported Formats
GPT 5.5OpenAI's most advanced model released April 2026. GPT-5.5 is recommended for most reasoning workloads, combining frontier intelligence with configurable reasoning effort (none → xhigh). Available in API, Codex, and ChatGPT.
GPT 5.4GPT-5.4 is OpenAI's frontier model for complex professional work, designed for agentic, coding, and professional workflows with the highest reasoning capability. Features a 1.05M token context window, native computer use, and built-in support for web search, file search, and MCP.
GPT 5.4 ProGPT-5.4 Pro is a premium version of GPT-5.4 that produces smarter and more precise responses by using more compute to think harder. Supports reasoning effort levels (medium, high, xhigh) and is optimized for tackling the most difficult problems requiring deep reasoning.