GPT-5.1 Codex Max
API ID gpt-5.1-codex-max
gpt-5.1-codex-max was an OpenAI model, released December 2025. It had a 400,000-token context window and up to 128,000 output tokens. It took image input and supported function calling, structured outputs and reasoning.
- Status
- Retired
- Released
- December 2025
- Shutdown
- Jul 23, 2026
- Replacement
- GPT-5.6 Solgpt-5.6-sol
gpt-5.1-codex-max stopped serving on July 23, 2026. Recommended replacement: gpt-5.6-sol.
On cloud platforms
All platform dates| Platform | Platform ID | State | Shutdown | Time left | Replacement | Source |
|---|---|---|---|---|---|---|
| Microsoft Foundryversion 2025-12-04 | gpt-5.1-codex-max | Active | May 18, 2027 | 215 days | — | source |
Microsoft Foundry (version 2025-12-04) retires this model 299 days after OpenAI's own API.
Read daily from each platform's own pages. The shutdown date and countdown on this page use OpenAI's own date. Time left counts to 00:00 UTC on the shutdown date, which is the evening before in ET.
Features
Compare models| Feature | Value | Since | Source |
|---|---|---|---|
| Structured outputsThe model can be held to a JSON schema you supply, so every reply parses without retries or cleanup. | Supported | in place when tracking began (October 6, 2026) | source |
| Function callingAlso called tool use. You describe functions; the model replies with a function name and arguments for your code to run, then uses the result. | Supported | in place when tracking began (October 6, 2026) | source |
| Prompt cachingA prompt prefix you send again and again (system prompt, documents, tools) is cached, so later requests cost less and start faster. | Supported | in place when tracking began (October 6, 2026) | source |
| Batch APISend many requests as one job that runs in the background, usually finished within 24 hours, at a lower price than live requests. | Not supported | in place when tracking began (October 6, 2026) | source |
| Image inputImages such as screenshots, photos and charts can go in the prompt for the model to read. | Supported | in place when tracking began (October 6, 2026) | source |
| Reasoning / thinkingThe model can work through a problem step by step before it answers: usually better answers to hard questions, at the cost of more tokens and time. | Supported | in place when tracking began (October 6, 2026) | source |
| Fine-tuningYou can train your own version of the model on your examples through the company's API, then call it like any other model. | Not supported | in place when tracking began (October 6, 2026) | source |
| Built-in web searchThe company's API can search the web for the model during a request and cite its sources; you don't need a search service of your own. | Supported | in place when tracking began (October 6, 2026) | source |
| Context windowThe most the model can work with in one request, in tokens: your prompt, conversation history and files. A token is about three-quarters of an English word. | 400,000 tokens | in place when tracking began (October 6, 2026) | source |
| Max output tokensThe longest reply the model can write in one response, in tokens. A token is about three-quarters of an English word. | 128,000 tokens | in place when tracking began (October 6, 2026) | source |
Not published by OpenAI: PDF input, temperature parameter, top_p parameter, logprobs.
Price history
USD per 1M tokens, standard tierNo price history yet.
Prices
USD per 1M tokens, every type and band, by tierNo published prices.
Changelog
Changes we detected on OpenAI's pagesNo changes recorded yet.
Last checked · Sources: OpenAI deprecations, OpenAI pricing, OpenAI models