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GPT-5.1 Codex

Multimodal
OpenAI

GPT-5.1 Codex is a version of GPT-5.1 optimized for agentic coding tasks in Codex and similar environments. Features enhanced reasoning capabilities and is available through the Responses API. The base model snapshot is regularly updated.

Key Specifications

Parameters
-
Context
400.0K
Release Date
November 18, 2025
Average Score
64.3%

Timeline

Key dates in the model's history
Announcement
November 18, 2025
Today
March 25, 2026

Technical Specifications

Parameters
-
Training Tokens
-
Knowledge Cutoff
September 30, 2024
Family
-
Capabilities
MultimodalZeroEval

Pricing & Availability

Input (per 1M tokens)
$1.25
Output (per 1M tokens)
$10.00
Max Input Tokens
400.0K
Max Output Tokens
128.0K
Supported Features
Function CallingStructured OutputCode ExecutionWeb SearchBatch InferenceFine-tuning

Benchmark Results

Model performance metrics across various tests and benchmarks

Programming

Programming skills tests
SWE-Bench Verified
effort reasoningSelf-reported
74.0%

Other Tests

Specialized benchmarks
SWE-Lancer
IC SWESelf-reported
66.0%
Terminal-Bench 2.0
n=89, high effort reasoningSelf-reported
53.0%

License & Metadata

License
proprietary
Announcement Date
November 18, 2025
Last Updated
January 22, 2026

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