Overview
GPT-5.1-Codex is OpenAI's coding-specialized variant of GPT-5.1, released for developers in mid-November 2025. While the general-purpose GPT-5.1 handles a broad mix of agentic and coding work, GPT-5.1-Codex is tuned specifically for long-running, autonomous software engineering inside Codex and Codex-like harnesses — the kind of tasks that involve creating pull requests, reviewing code, debugging, and building front-end interfaces over many steps.
The model accepts both text and images (such as screenshots for UI work) and returns text. It offers a 400,000-token context window and can produce up to 128,000 output tokens, with a knowledge cutoff of September 30, 2024. GPT-5.1-Codex is exposed through OpenAI's Responses API and its model snapshot is updated over time; it also powers the Codex CLI, IDE extensions, and cloud, and shipped in public preview inside GitHub Copilot.
GPT-5.1-Codex sits between the lighter GPT-5.1-Codex-Mini and the higher-end GPT-5.1-Codex-Max in OpenAI's coding lineup. It supports adjustable reasoning effort, so developers can trade speed for depth on harder problems. On SWE-bench Verified, GPT-5.1-Codex scores about 73.7% at medium reasoning effort, placing it among the stronger coding models of its generation.
| Released | 2025-11-19 |
|---|---|
| License | Proprietary (OpenAI API) |
| Weights | API only |
| Context | 400K |
| Max output | 128K |
| Architecture | A version of GPT-5.1 optimized for agentic coding. Like other GPT-5.1 models, it supports adjustable reasoning effort; OpenAI has not published parameter counts or architectural details. |
| Knowledge cutoff | September 30, 2024 |
| Modalities | Text, Vision |
| Status | Available |
Benchmarks
Scores on a 0–100 scale (25-point gridlines); higher is better. Each benchmark links to its published source.
Pricing
| Input | $1.25 / 1M tokens per 1M tokens |
|---|---|
| Cached input | $0.125 / 1M tokens per 1M tokens |
| Output | $10.00 / 1M tokens per 1M tokens |
Pricing for the gpt-5.1-codex model on the OpenAI API (Responses API).
Strengths
- Purpose-built for long-running, agentic coding loops rather than one-shot completions
- Large 400K-token context window suits big repositories and multi-file refactors
- Accepts image input (e.g. UI screenshots) for front-end and visual debugging tasks
- Adjustable reasoning effort lets you balance latency against problem difficulty
- Integrated across the Codex CLI, IDE extensions, cloud, and GitHub Copilot
Best for
- Autonomous, multi-step coding tasks such as opening and iterating on pull requests
- Project-scale refactors and deep debugging across large codebases
- Automated code review and Q&A inside Codex or similar agent harnesses
- Front-end and UI development from screenshots or mockups
- Embedding agentic coding into developer tools via the OpenAI Responses API
How to access
| Provider | Model ID |
|---|---|
| OpenAI ↗ | gpt-5.1-codex |
| OpenRouter ↗ | openai/gpt-5.1-codex |
Codex — every version
The full lineage of the Codex line, newest first. Every version has its own page — click any to compare specs, benchmarks and pricing.
| Version | Released | Context | License |
|---|---|---|---|
| GPT-5.3-Codexcurrent | 2026-02-05 | — | Proprietary |
| GPT-5.3-Codex-Spark | 2026-02-12 | — | Proprietary |
| GPT-5.2-Codex | 2025-12-11 | — | Proprietary |
| GPT-5.1-Codex | 2025-11-19 | — | Proprietary |
| GPT-5-Codex | 2025-09 | — | Proprietary |
FAQ
What is GPT-5.1-Codex?
GPT-5.1-Codex is a version of OpenAI's GPT-5.1 optimized for agentic, long-running coding tasks. It is designed to work inside Codex and Codex-like harnesses on jobs such as pull requests, code review, debugging, and front-end development, and is available through the OpenAI Responses API.
How is GPT-5.1-Codex different from GPT-5.1?
GPT-5.1 is a general-purpose model that handles a broad range of agentic and coding work, while GPT-5.1-Codex is specifically tuned for long-running, autonomous software engineering. OpenAI also offers a lighter GPT-5.1-Codex-Mini and a higher-end GPT-5.1-Codex-Max in the same lineup.
What is GPT-5.1-Codex's context window and output limit?
GPT-5.1-Codex has a 400,000-token context window and can generate up to 128,000 output tokens. Its knowledge cutoff is September 30, 2024.
How much does GPT-5.1-Codex cost?
On the OpenAI API, GPT-5.1-Codex is priced at $1.25 per million input tokens, $0.125 per million cached input tokens, and $10.00 per million output tokens.