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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 modelMuse Spark OpenMetaRemove
ProviderOpenAIMeta
Discovery tierFrontierFrontier
AddedApr 23, 2026Oct 15, 2026
Limits
Context window1.05MBest1.05M
Max output128K—
Average output490 tokens1.3K tokens
Pricing, USD per 1M tokens
Input$5.00$1.25Best
Output$30.00$4.25Best
Cache read$0.50$0.15Best
Performance
Request success (24h)100.0%—
Benchmark indexes
Intelligence Index38.438.9Best
Coding Index74.9—
Capabilities
ReasoningYesYes
ToolsYesYes
VisionYesYes
Structured outputYesYes
PDF inputYesNo
Reasoning effortnone, low, medium, high, xhighlow, medium, high, xhigh

Public evaluations

Benchmarks

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

  • GPT 5.5
  • Muse Spark Open

Intelligence Index

  • GPT 5.538.4
  • Muse Spark Open38.9

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
    • Muse Spark Open: —

Agentic work

  • AutomationBench-AA

    Workflow automation, penalized for guardrail violations

    • GPT 5.5: 47.3%
    • Muse Spark Open: 49.7%Top

  • AutomationBench-AA tasks completed

    Workflows finished end to end without a guardrail violation

    • GPT 5.5: 19.6%
    • Muse Spark Open: 20.9%Top

  • AA-Briefcasev1.1

    Agentic knowledge work, rated head to head

    • GPT 5.5: 1,136 Elo
    • Muse Spark Open: 1,279 EloTop

  • GDPval-AAv2.1

    Economically valuable occupational tasks, rated head to head

    • GPT 5.5: 1,351 Elo
    • Muse Spark Open: 1,401 EloTop

Document reasoning

  • GDP.pdf

    Professional reasoning over PDF documents, all-pass rate

    • GPT 5.5: 21.2%Top
    • Muse Spark Open: 18.6%

  • AA-LCRv1.1

    Reasoning across long documents

    • GPT 5.5: 84.3%Top
    • Muse Spark Open: 78.3%

  • MLCR-AA

    Long-context reasoning over medical records

    • GPT 5.5: 28.9%Top
    • Muse Spark Open: 7.8%

Reasoning and knowledge

  • Humanity’s Last Exam

    Expert-level questions across academic fields

    • GPT 5.5: 45.8%Top
    • Muse Spark Open: 43.9%

  • GPQA Diamond

    Graduate-level science questions

    • GPT 5.5: 93.5%Top
    • Muse Spark Open: 89.0%

  • IFBench

    Following precise output instructions

    • GPT 5.5: 75.9%
    • Muse Spark Open: —

Coding

  • Terminal-Benchv4.0

    Practical software engineering in a terminal

    • GPT 5.5: 14.6%Top
    • Muse Spark Open: 8.1%

  • SciCode

    Scientific computing in Python

    • GPT 5.5: 55.8%
    • Muse Spark Open: 58.4%Top

Legacy evaluations

  • Terminal-Bench Hard

    Earlier terminal task suite

    • GPT 5.5: 60.6%
    • Muse Spark Open: —

  • τ²-Bench Telecom

    Tool use in a customer-support simulation

    • GPT 5.5: 93.9%
    • Muse Spark Open: —

  • AA-LCR (unversioned)

    Long-context reasoning, earlier grading

    • GPT 5.5: 84.3%Top
    • Muse Spark Open: 78.3%

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

Other OpenAI models, starting with the same family.