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openai/gpt-5-2-codex
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GPT-5.2-Codex

GPT-5.2-Codex is an upgraded version of GPT-5.1-Codex optimized for software engineering and coding workflows. It is designed for both interactive development sessions and long, independent execution of complex engineering tasks. The model supports building projects from scratch, feature development, debugging, large-scale refactoring, and code review. Compared to GPT-5.1-Codex, 5.2-Codex is more steerable, adheres closely to developer instructions, and produces cleaner, higher-quality code outputs. Reasoning effort can be adjusted with the `reasoning.effort` parameter. Read the [docs here](https://openrouter.ai/docs/use-cases/reasoning-tokens#reasoning-effort-level) Codex integrates into developer environments including the CLI, IDE extensions, GitHub, and cloud tasks. It adapts reasoning effort dynamically—providing fast responses for small tasks while sustaining extended multi-hour runs for large projects. The model is trained to perform structured code reviews, catching critical flaws by reasoning over dependencies and validating behavior against tests. It also supports multimodal inputs such as images or screenshots for UI development and integrates tool use for search, dependency installation, and environment setup. Codex is intended specifically for agentic coding applications.

1/14/2026
400,000 tokens

Specifications

Modalities

Input
text
image
Output
text

Supported Parameters

include_reasoning
max_tokens
reasoning
response_format
seed
structured_outputs
tool_choice
tools

Max Output Tokens

128,000

Reasoning Configuration

Default
Thinking on (effort: medium)
Selectable effort levels
xhigh
high
medium
low
Turning thinking off
Not possible (always thinks)

How to control thinking, and what it costs

Frequently asked questions

Is GPT-5.2-Codex available on FastMetal?
Not at the moment. GPT-5.6 Sol, from the same lab, is available on the FastMetal API today.
What is the context window of GPT-5.2-Codex?
400,000 tokens, shared between the prompt and the response.