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 Azure Cognitive Services API with up to 128K output tokens.
Capabilities
Input Modalities
textimageaudio
Output Modalities
text
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 Azure Cognitive Services 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
Azure Cognitive ServicesFamily
gpt-codex
Release Date
Nov 14, 2025
Knowledge Cutoff
Sep 30, 2024
API Integration
NPM Package
@ai-sdk/azure
Environment Variables
AZURE_COGNITIVE_SERVICES_RESOURCE_NAME
AZURE_COGNITIVE_SERVICES_API_KEY