# GPT-5.1-Codex spotted on Arena

GPT-5.1-Codex is a model from OpenAI, released on 13 Nov 2025. First seen 11 Sep 2026. Catalogues list a 400,000 tokens context window. 8 evidence links.

- Kind: Sighting
- Developer: OpenAI
- Confidence: Confirmed
- First seen: 2026-09-11T22:09:46.186Z
- Model: [GPT-5.1-Codex](https://alexgetman.com/models/openai/gpt-5-1-codex/)
- Canonical: https://alexgetman.com/signals/2026/09/11/gpt-5-1-codex-high/

## Evidence links

- [Arena · leaderboards](https://platform.openai.com/docs/models/gpt-5.1-codex)
- [OpenCode · discovery](https://opencode.ai/data/openai/gpt-5-1-codex)
- [OpenRouter](https://openrouter.ai/openai/gpt-5.1-codex)
- [Artificial Analysis · benchmarks](https://artificialanalysis.ai/models)
- [TrueFoundry · Azure catalogue](https://github.com/truefoundry/models/blob/main/providers/microsoft-foundry/gpt-5.1-codex.yaml)
- [models.dev · catalogue](https://models.dev/#gpt-5.1-codex)
- [OpenAI · model index](https://developers.openai.com/api/docs/models/gpt-5.1-codex)
- [OpenAI · deprecations](https://platform.openai.com/docs/deprecations)