Model detail
gpt-5.1-codex-max
GPT-5.1-Codex-Max is OpenAI’s latest agentic coding model, designed for long-running, high-context software development tasks. It is based on an updated version of the 5.1 reasoning stack and trained on agentic workflows spanning software engineering, mathematics, and research. GPT-5.1-Codex-Max delivers faster performance, improved reasoning, and higher token efficiency across the development lifecycle.
Model specs
- Context length
- 400K
- Max output
- 128K
- I/O modalities
- Text / Image
- Released
- 2025-12
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API endpoints
One MixRoute gateway, OpenAI-compatible
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OpenAI-compatible
/v1/chat/completionsPOST
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Pricing
Flat rate, unit: /1M Tokens
Input
$1.2500 /1M Tokens
Completion
$10.0000 /1M Tokens
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Selection summary
Quickly judge whether it fits your workload
What is this model good for?
Long-running, high-context software development workflows
Use gpt-5.1-codex-max for extended agentic work across software engineering, mathematics, and research-oriented development tasks.
What should you check before using it?
Constrain long-running execution before scaling
Set clear task boundaries, tool permissions, time limits, and review checkpoints, then assess token efficiency and completion quality.
How should you start?
Use gpt-5.1-codex-max on a supervised long task
Begin with model ID gpt-5.1-codex-max in a sandboxed workflow where intermediate changes and final output can be reviewed.
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Token cost estimator
Live estimate from this page's pricing, not an actual bill
This model has no cache-read price; caching is not counted
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FAQ
gpt-5.1-codex-max is intended for long-running, high-context software development work across engineering, mathematics, and research-oriented workflows.
One endpoint, a testable decision
Test this model and alternate routes with the same request format
Start from a real workload, then let quality, total cost, and failure conditions decide whether to send production traffic.