The AI arena is free today

Open Superagent

Claude Sonnet 5.5 vs o1-pro

Claude Sonnet 5.5 leads the LLM Stats Score 58.1 to 19.7.

Anthropic · OpenAI · Updated for 2026

Which is better?

Claude Sonnet 5.5 leads the overall LLM Stats Score 58.1 to 19.7, ranking #3 overall.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose Claude Sonnet 5.5

  • overall performance matters — it scores 58.1 and ranks #3 on LLM Stats
  • your work emphasizes reasoning — it leads those capability indexes
  • you want the most recent training data — it shipped Sep 2026

Choose o1-pro

  • you are already invested in the OpenAI ecosystem

At a glance

The differences that matter most.

Claude Sonnet 5.5
Anthropic
o1-pro
OpenAI
Core performance indexes
LLM Stats Score
58.1
#3
19.7
#206
Reasoning
56.6
#3
20.0
#197
Cost, coverage & limits
Benchmark wins
—
—
Input price
$2.00 / M
— / M
Output price
$10.00 / M
— / M
Context window
1,000,000
—

Individual benchmarks

47 reported for Claude Sonnet 5.5 · 2 for o1-pro

No common benchmarks found

Claude Sonnet 5.5 and o1-prodon't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Human preference

Blind head-to-head votes and playground preference scores

Context Window

Maximum input and output token capacity

Only Claude Sonnet 5.5 specifies input context (1,000,000 tokens). Only Claude Sonnet 5.5 specifies output context (128,000 tokens).

Anthropic
Claude Sonnet 5.5
Input1,000,000 tokens
Output128,000 tokens
OpenAI
o1-pro
Input- tokens
Output- tokens
Tue Sep 29 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Both Claude Sonnet 5.5 and o1-pro support multimodal inputs.

They are both capable of processing various types of data, offering versatility in application.

Claude Sonnet 5.5

Text
Images
Audio
Video

o1-pro

Text
Images
Audio
Video

License

Usage and distribution terms

Both models are licensed under proprietary licenses.

Both models have usage restrictions defined by their respective organizations.

Claude Sonnet 5.5

Proprietary

Closed source

o1-pro

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Sonnet 5.5 was released on 2026-09-28, while o1-pro was released on 2024-12-17.

Claude Sonnet 5.5 is 22 months newer than o1-pro.

Claude Sonnet 5.5

Sep 28, 2026

1 days ago

1.8yr newer
o1-pro

Dec 17, 2024

1.8 years ago

Knowledge Cutoff

When training data ends

Claude Sonnet 5.5 has a knowledge cutoff of 2026-06-01, while o1-pro has a cutoff of 2023-09-30.

Claude Sonnet 5.5 has more recent training data (up to 2026-06-01), making it potentially better informed about events through that date compared to o1-pro (2023-09-30).

Claude Sonnet 5.5

Jun 2026

2.8 yr newer
o1-pro

Sep 2023

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

Run your own prompts against Claude Sonnet 5.5 and o1-pro side-by-side, then vote on the output you prefer.

Claude Sonnet 5.5
✓ Preferred
o1-pro
Open in Playground

FAQ

Common questions about Claude Sonnet 5.5 vs o1-pro.

Which is better, Claude Sonnet 5.5 or o1-pro?

Claude Sonnet 5.5 leads the LLM Stats Score 58.1 to 19.7. Claude Sonnet 5.5 is made by Anthropic and o1-pro is made by OpenAI. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does Claude Sonnet 5.5 compare to o1-pro in benchmarks?

Claude Sonnet 5.5 scores BenchCAD (with Python tool): 96.3%, ArXivMath (with tools): 95.2%, Global-MMLU: 92.1%, MILU: 91.6%, SWE-bench Multilingual: 90.3%. o1-pro scores AIME 2024: 86.0%, GPQA: 79.0%.

What are the context window sizes for Claude Sonnet 5.5 and o1-pro?

Claude Sonnet 5.5 supports 1.0M tokens and o1-pro supports an unknown number of tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Claude Sonnet 5.5 and o1-pro?

Key differences include LLM Stats Score (58.1 vs 19.7). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Sonnet 5.5 and o1-pro?

Claude Sonnet 5.5 is developed by Anthropic and o1-pro is developed by OpenAI.

Related comparisons