Model detail
GPT-5-Codex
GPT-5-Codex is a specialized version of GPT-5 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, 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.
Model specs
- Model ID
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gpt-5-codex
- Context length
- 400K
- Max output
- 128K
- I/O modalities
- Released
- 2025-09
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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?
Codex model for coding and agentic tasks
GPT-5-Codex: GPT-5-Codex is a version of GPT-5 optimized for agentic coding tasks in Codex or similar environments. It's available in the Responses API only and the underlying model snapshot wi. 400,000-token context.
What should you check before using it?
400,000 context, 128,000 output
OpenAI model. Supports tool calling, structured outputs, function calling. Knowledge cutoff: 2024-09-30.
Why use it through MixRoute?
Drop-in via OpenAI-compatible endpoint on MixRoute
Set the model parameter to "gpt-5-codex" and use your MixRoute API key.
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Capabilities & compatibility
Unconfirmed capabilities stay "Unknown," no guesses
Tool calling
GPT-5-Codex supports function and tool calls.
tools definition; the response returns tool_calls to execute and feed results back.
Structured output
GPT-5-Codex can produce JSON-formatted output on demand.
response_format: { type: "json_schema" } forces valid JSON output.
Streaming
GPT-5-Codex supports streamed responses.
stream: true streams tokens incrementally, so chat UIs render as they arrive.
Prompt caching
GPT-5-Codex supports prompt caching under supported routing conditions.
Vision input
GPT-5-Codex can process image inputs alongside text.
image_url content part alongside text messages.
OpenAI SDK
Call GPT-5-Codex through MixRoute's OpenAI-compatible endpoint.
base_url to https://api.mixroute.ai/v1; everything else follows the OpenAI style.
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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-Codex is a specialized version of GPT-5 optimized for software engineering and coding workflows. It supports both interactive development and long, independent execution of complex engineering tasks, including building, debugging, refactoring, and code review.
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.