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OpenAI · Language model

GPT-5.1-Codex-Mini

openai/gpt-5.1-codex-mini
  • Language
Released Nov 13, 2025

GPT-5.1-Codex-Mini is a smaller and faster version of GPT-5.1-Codex

Specifications

Context window
400,000 tokens
Max output
128,000 tokens
Input
image, text
Output
text
Reasoning effort
high, medium, low
Tokenizer
GPT

Supported parameters

Accepted by the model and forwarded as-is by the gateway.

  • max_completion_tokens
  • reasoning
  • reasoning_effort
  • response_format
  • seed
  • structured_outputs
  • tool_choice
  • tools

Use it

POST /api/v1/chat/completions · MCP chat · full reference

curl https://omnirail.org/api/v1/chat/completions \
  -H "Authorization: Bearer $OMNIRAIL_KEY" -H "Content-Type: application/json" \
  -d '{"model":"openai/gpt-5.1-codex-mini","messages":[{"role":"user","content":"Hello"}],"max_tokens":300}'