GPT-5.1 Codex API
About
Build advanced reasoning agents with GPT-5.1 Codex, a specialized AI model optimized for complex logic and chain-of-thought tasks. This model delivers cost-effective pricing at $1.25/1M input and $10.00/1M output tokens, native tool calling support. Access GPT-5.1 Codex via the DevPass (LLM Gateway) API with up to 128K output tokens.
Capabilities
Input Modalities
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Output Modalities
text
Reasoning
Yes
Structured Output
Limits
Context Window
400K
Tokens
Input Limit
272K
Tokens
Max Output
128K
Tokens
Pricing
Standard (per 1M tokens)
Input
$1.25
Output
$10.00
Caching (per 1M tokens)
Read
$0.13
Frequently Asked Questions
GPT-5.1 Codex by DevPass (LLM Gateway) costs $1.25 per 1M input tokens and $10.00 per 1M output tokens. Cached reads cost $0.13 per 1M tokens.
Model Details
ID
gpt-5.1-codex
Provider
DevPass (LLM Gateway)Family
gpt-codex
Release Date
Nov 13, 2025
Knowledge Cutoff
Sep 30, 2024
API Integration
NPM Package
@ai-sdk/openai-compatible
Environment Variables
LLMGATEWAY_API_KEY
API Base URL
https://api.llmgateway.io/v1