GPT-5.1 Codex Max API
About
Build advanced reasoning agents with GPT-5.1 Codex Max, 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 Max via the Kilo Gateway API with up to 128K output tokens.
Capabilities
Input Modalities
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Output Modalities
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Reasoning
Yes
Structured Output
Yes
Tool Use
Yes
WeightsClosed
Temperature
Fixed
Attachment
Supported
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 Max by Kilo 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
openai/gpt-5.1-codex-max
Provider
Kilo GatewayFamily
gpt-codex
Release Date
Nov 13, 2025
Knowledge Cutoff
Sep 30, 2024
API Integration
NPM Package
@ai-sdk/openai-compatible
Environment Variables
KILO_API_KEY
API Base URL
https://api.kilo.ai/api/gateway