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Anthropic · Frontier

Claude Sonnet 5.5

Added Sep 28, 2026

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Use in the app

Claude Sonnet 5.5 handles everyday coding, tool-based workflows, visual analysis, and polished writing with a 1M-token context window. This version skips up-front thinking and can reason between tool calls for faster responses; use Thinking for deeper planning and complex problems.

  • Reasoning
  • Tools
  • Vision
  • Structured output
  • PDF input
Input
Text, Images
Output
Text
Reasoning effort
low · medium · high
Discovery tier
Frontier

Pricing

USD per 1M tokens
Input
$2.00
Output
$10.00
Cache read
$0.10
Cache write
$2.50
$4.00 for a 1-hour cache

Reference prices as published by the model provider. API example

Specifications

Context window
1M
Max output
128K
Average output (7 days)
523 tokens
Longer than 50% of 473 models

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TryGPT 5.6 SolGrok 4.7MiMo V2.6 ProAll 3

Public evaluations

Benchmarks

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

Intelligence Index

46.8

Tested at high reasoning effort

Better than 93% of 326 scored models

3.8Catalog models by score55.1

Agentic work

  • AutomationBench-AA

    59.4%

    Workflow automation, penalized for guardrail violations

    Better than 79% of 173 scored models

  • AutomationBench-AA tasks completed

    29.4%

    Workflows finished end to end without a guardrail violation

    Better than 80% of 173 scored models

  • AA-Briefcasev1.1

    1,635 Elo

    Agentic knowledge work, rated head to head

    Better than 93% of 166 scored models

  • GDPval-AAv2.1

    1,548 Elo

    Economically valuable occupational tasks, rated head to head

    Better than 81% of 187 scored models

Document reasoning

  • GDP.pdf

    25.2%

    Professional reasoning over PDF documents, all-pass rate

    Better than 88% of 171 scored models

  • AA-LCRv1.1

    78.0%

    Reasoning across long documents

    Better than 65% of 309 scored models

  • MLCR-AA

    18.9%

    Long-context reasoning over medical records

    Better than 76% of 121 scored models

Reasoning and knowledge

  • Humanity’s Last Exam

    45.8%

    Expert-level questions across academic fields

    Better than 88% of 323 scored models

Coding

  • Terminal-Benchv4.0

    43.9%

    Practical software engineering in a terminal

    Better than 90% of 171 scored models

  • SciCode

    53.7%

    Scientific computing in Python

    Better than 66% of 174 scored models

Legacy evaluations

  • AA-LCR (unversioned)

    78.0%

    Long-context reasoning, earlier grading

    Better than 65% of 309 scored models

Scores from Artificial Analysis, updated Oct 26, 2026. Claude Sonnet 5.5 was tested at high 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.

Throughput
269.5 tok/s
Faster than 92% of 259 models
Time to first token
4.9 s
Quicker than 31% of 259 models
Prompt cache hits
37.0%
About $1.30 per 1M input tokens with caching
Request success (24h)
99.9%
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 93.9%
  • 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": "anthropic/claude-sonnet-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="anthropic/claude-sonnet-5.5",
    messages=[{"role": "user", "content": "Explain this stack trace."}],
)
print(reply.choices[0].message.content)

Anthropic

Other Anthropic models, starting with the same family.