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OpenAI · Frontier

GPT 5.1 Codex Max

Added Dec 4, 2025

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Use in the app

Top-tier GPT-5.1 Codex route used when direct OpenAI is unavailable.

  • Reasoning
  • Tools
  • Vision
  • Structured output
  • PDF input
Input
Text, Images
Output
Text
Reasoning effort
none · minimal · low · medium · high · xhigh
Discovery tier
Frontier

Pricing

USD per 1M tokens
Input
$2.50
Output
$20.00
Cache read
$0.25

Reference prices as published by the model provider. API example

Specifications

Context window
400K
Max output
128K

Side by side

GPT 5.1 Codex Max compared

Specifications, prices, speed and benchmark scores next to each other. Benchmarks below show every compared model too.

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GPT 5.1 Codex MaxOpenAIThis modelGLM 5V Turbo ThinkingZ.aiRemove
ProviderOpenAIZ.ai
Discovery tierFrontierOpen weights
AddedDec 4, 2025Apr 2, 2026
Limits
Context window400KBest202.8K
Max output128K131.07KBest
Average output—942 tokens
Pricing, USD per 1M tokens
Input$2.50$1.20Best
Output$20.00$4.00Best
Cache read$0.25$0.24Best
Performance
Throughput—41.0 tok/s
Time to first token—6.5 s
Request success (24h)—97.6%
Benchmark indexes
Intelligence Index23.7Best23.5
Math Index95.7—
Capabilities
ReasoningYesYes
ToolsYesYes
VisionYesYes
Structured outputYesYes
PDF inputYesNo
Video inputNoYes
Reasoning effortnone, minimal, low, medium, high, xhigh—

Public evaluations

Benchmarks

Independent evaluation results, with how each score ranks among the models in the Noumen catalog.

  • GPT 5.1 Codex Max
  • GLM 5V Turbo Thinking

Intelligence Index

  • GPT 5.1 Codex Max23.7
  • GLM 5V Turbo Thinking23.5

GPT 5.1 Codex Max tested at high reasoning effort

GPT 5.1 Codex Max: Better than 58% of 326 scored models

3.8Catalog models by score55.1

Indexes

  • Math Index

    Composite of the math evaluations

    • GPT 5.1 Codex Max: 95.7
    • GLM 5V Turbo Thinking: —

Document reasoning

  • AA-LCRv1.1

    Reasoning across long documents

    • GPT 5.1 Codex Max: 69.3%
    • GLM 5V Turbo Thinking: 70.3%Top

Reasoning and knowledge

  • Humanity’s Last Exam

    Expert-level questions across academic fields

    • GPT 5.1 Codex Max: 25.7%Top
    • GLM 5V Turbo Thinking: 17.1%

  • GPQA Diamond

    Graduate-level science questions

    • GPT 5.1 Codex Max: 86.0%Top
    • GLM 5V Turbo Thinking: 80.9%

  • MMLU-Pro

    Multi-subject knowledge and reasoning

    • GPT 5.1 Codex Max: 86.0%
    • GLM 5V Turbo Thinking: —

  • IFBench

    Following precise output instructions

    • GPT 5.1 Codex Max: 70.0%Top
    • GLM 5V Turbo Thinking: 61.1%

Coding

  • LiveCodeBench

    Recent competitive programming problems

    • GPT 5.1 Codex Max: 84.9%
    • GLM 5V Turbo Thinking: —

Math

  • AIME 2025

    Competition mathematics, 2025 problems

    • GPT 5.1 Codex Max: 95.7%
    • GLM 5V Turbo Thinking: —

Legacy evaluations

  • Terminal-Bench Hard

    Earlier terminal task suite

    • GPT 5.1 Codex Max: 34.8%Top
    • GLM 5V Turbo Thinking: 32.6%

  • τ²-Bench Telecom

    Tool use in a customer-support simulation

    • GPT 5.1 Codex Max: 83.0%
    • GLM 5V Turbo Thinking: 98.5%Top

  • AA-LCR (unversioned)

    Long-context reasoning, earlier grading

    • GPT 5.1 Codex Max: 69.3%
    • GLM 5V Turbo Thinking: 70.3%Top

Scores from Artificial Analysis, updated Oct 26, 2026. GPT 5.1 Codex Max was tested at high reasoning effort; compare scores measured at the same effort.Artificial Analysis

Developers

Use it through the API

Noumen’s API is OpenAI-compatible: any Chat Completions client works with a base URL and a key.

Read the quickstart
curl https://www.noumen.xyz/api/v1/chat/completions \
  -H "Authorization: Bearer $NOUMEN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "openai/gpt-5.1-codex-max",
    "reasoning_effort": "medium",
    "messages": [{ "role": "user", "content": "Explain this stack trace." }]
  }'
import os
from openai import OpenAI

client = OpenAI(base_url="https://www.noumen.xyz/api/v1", api_key=os.environ["NOUMEN_API_KEY"])
reply = client.chat.completions.create(
    model="openai/gpt-5.1-codex-max",
    messages=[{"role": "user", "content": "Explain this stack trace."}],
)
print(reply.choices[0].message.content)

OpenAI

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