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OpenAI · Frontier

GPT 5.5

Added Apr 23, 2026

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Use in the app

GPT-5.5 is an OpenAI model, built for agentic coding, computer use, and professional knowledge work with stronger reasoning and token efficiency.

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

Pricing

USD per 1M tokens
Input
$5.00
Output
$30.00
Cache read
$0.50

Reference prices as published by the model provider. API example

Specifications

Context window
1.1M
Max output
128K
Average output (7 days)
490 tokens
Longer than 48% of 465 models

Side by side

GPT 5.5 compared

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

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GPT 5.5OpenAIThis modelGPT 4.1OpenAIRemove
ProviderOpenAIOpenAI
Discovery tierFrontierFrontier
AddedApr 23, 2026Sep 10, 2025
Limits
Context window1.05MBest1.05M
Max output128KBest32.77K
Average output490 tokens29 tokens
Pricing, USD per 1M tokens
Input$5.00$2.00Best
Output$30.00$8.00Best
Cache read$0.50$0.50
Performance
Request success (24h)100.0%100.0%
Benchmark indexes
Intelligence Index38.4Best12.7
Coding Index74.9—
Math Index—34.7
Capabilities
ReasoningYesNo
ToolsYesYes
VisionYesYes
Structured outputYesYes
PDF inputYesYes
Reasoning effortnone, low, medium, high, xhigh—

Public evaluations

Benchmarks

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

  • GPT 5.5
  • GPT 4.1

Intelligence Index

  • GPT 5.538.4
  • GPT 4.112.7

GPT 5.5 tested at xhigh reasoning effort

GPT 5.5: Better than 82% of 326 scored models

3.8Catalog models by score55.1

Indexes

  • Coding Index

    Composite of the coding evaluations

    • GPT 5.5: 74.9
    • GPT 4.1: —

  • Math Index

    Composite of the math evaluations

    • GPT 5.5: —
    • GPT 4.1: 34.7

Agentic work

  • AutomationBench-AA

    Workflow automation, penalized for guardrail violations

    • GPT 5.5: 47.3%
    • GPT 4.1: —

  • AutomationBench-AA tasks completed

    Workflows finished end to end without a guardrail violation

    • GPT 5.5: 19.6%
    • GPT 4.1: —

  • AA-Briefcasev1.1

    Agentic knowledge work, rated head to head

    • GPT 5.5: 1,136 Elo
    • GPT 4.1: —

  • GDPval-AAv2.1

    Economically valuable occupational tasks, rated head to head

    • GPT 5.5: 1,351 Elo
    • GPT 4.1: —

Document reasoning

  • GDP.pdf

    Professional reasoning over PDF documents, all-pass rate

    • GPT 5.5: 21.2%
    • GPT 4.1: —

  • AA-LCRv1.1

    Reasoning across long documents

    • GPT 5.5: 84.3%Top
    • GPT 4.1: 68.3%

  • MLCR-AA

    Long-context reasoning over medical records

    • GPT 5.5: 28.9%
    • GPT 4.1: —

Reasoning and knowledge

  • Humanity’s Last Exam

    Expert-level questions across academic fields

    • GPT 5.5: 45.8%Top
    • GPT 4.1: 4.2%

  • GPQA Diamond

    Graduate-level science questions

    • GPT 5.5: 93.5%Top
    • GPT 4.1: 66.6%

  • MMLU-Pro

    Multi-subject knowledge and reasoning

    • GPT 5.5: —
    • GPT 4.1: 80.6%

  • IFBench

    Following precise output instructions

    • GPT 5.5: 75.9%Top
    • GPT 4.1: 43.0%

Coding

  • Terminal-Benchv4.0

    Practical software engineering in a terminal

    • GPT 5.5: 14.6%
    • GPT 4.1: —

  • SciCode

    Scientific computing in Python

    • GPT 5.5: 55.8%
    • GPT 4.1: —

  • LiveCodeBench

    Recent competitive programming problems

    • GPT 5.5: —
    • GPT 4.1: 45.7%

Math

  • AIME 2025

    Competition mathematics, 2025 problems

    • GPT 5.5: —
    • GPT 4.1: 34.7%

  • AIME

    Competition mathematics

    • GPT 5.5: —
    • GPT 4.1: 43.7%

  • MATH-500

    Competition math problems

    • GPT 5.5: —
    • GPT 4.1: 91.3%

Legacy evaluations

  • Terminal-Bench Hard

    Earlier terminal task suite

    • GPT 5.5: 60.6%Top
    • GPT 4.1: 13.6%

  • τ²-Bench Telecom

    Tool use in a customer-support simulation

    • GPT 5.5: 93.9%Top
    • GPT 4.1: 47.1%

  • AA-LCR (unversioned)

    Long-context reasoning, earlier grading

    • GPT 5.5: 84.3%Top
    • GPT 4.1: 68.3%

Scores from Artificial Analysis, updated Oct 26, 2026. GPT 5.5 was tested at xhigh reasoning effort; compare scores measured at the same effort.Artificial Analysis

Live routing data

Performance and reliability

Recent averages across requests routed for this model. Your own speed depends on prompt length, reasoning effort and load.

Prompt cache hits
0.0%
About $5.00 per 1M input tokens with caching
Request success (24h)
100.0%
Reliable

Cache hits are the share of input tokens recently served from a prompt cache across all requests. They are not a forecast of your own hit rate.

Hourly request success · last 72 hoursLowest hour 100.0%
  • Healthy (98% or more)
  • Degraded (90–98%)
  • Down (under 90%)
  • No requests

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-5.5",
    "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-5.5",
    messages=[{"role": "user", "content": "Explain this stack trace."}],
)
print(reply.choices[0].message.content)

OpenAI

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