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Step 5 Preview
GPT 5.1 Codex Max
GPT 5.1 Codex Max is a proprietary model from OpenAI, released Dec 4, 2025. Its best result is #48 of 143 on LiveCodeBench with 83.56%. It costs $1.25 per million input tokens and $10 per million output tokens, with a 400K-token context window.
- Developer
- OpenAI
- Released
- Dec 4, 2025
- Context window
- 400K
- Price in / out, per 1M tokens
- $1.25 / $10
- Weights
- Proprietary
- Inputs
- Text, Images
- Reasoning
- Yes
- Tool use
- Yes
Benchmarks
| Benchmark | Score bar | Accuracy | Rank | Cost / test |
|---|---|---|---|---|
| Vibe Code BenchCoding | 22.17% | 80 / 115 | $7.32 | |
| LiveCodeBenchCoding | 83.56% | 48 / 143 | $1.25 / $10 |
Vals AI, as of Oct 24, 2026.
Compare GPT 5.1 Codex Max
OpenAI
The lab behind GPT and ChatGPT, which brought large language models to hundreds of millions of people. Founded 2015, based in San Francisco. openai.com
Questions
Who makes GPT 5.1 Codex Max?
GPT 5.1 Codex Max is made by OpenAI, founded 2015 and based in San Francisco.
How much does GPT 5.1 Codex Max cost?
$1.25 per million input tokens and $10 per million output tokens, at its provider’s list price.
What is GPT 5.1 Codex Max’s context window?
400K tokens (400,000).
Is GPT 5.1 Codex Max open source?
No. GPT 5.1 Codex Max is proprietary and served through its provider’s API.