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Claude Sonnet 5.5 vs Step-3.5-Flash

Claude Sonnet 5.5 leads the LLM Stats Score 58.0 to 37.1. Step-3.5-Flash is 22.9x cheaper per token.

Anthropic · StepFun · Updated for 2026

Which is better?

Claude Sonnet 5.5 leads the overall LLM Stats Score 58.0 to 37.1, ranking #3 overall.

On price, Step-3.5-Flash is roughly 22.9x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Claude Sonnet 5.5 also accepts a larger context window (1,000,000 input tokens), making it the stronger choice for long documents and large codebases.

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

Choose Claude Sonnet 5.5

  • overall performance matters — it scores 58.0 and ranks #3 on LLM Stats
  • your work emphasizes reasoning and coding — it leads those capability indexes
  • you process long inputs — it offers a 1,000,000 token context window
  • you want the most recent training data — it shipped Sep 2026

Choose Step-3.5-Flash

  • cost matters — it's about 22.9x cheaper per token
  • you need open weights you can self-host or fine-tune

At a glance

The differences that matter most.

Claude Sonnet 5.5
Anthropic
Step-3.5-Flash
StepFun
Core performance indexes
LLM Stats Score
58.0
#3
37.1
#76
Reasoning
56.6
#3
37.2
#75
Coding
48.8
#2
20.4
#104
Agents
42.3
#3
15.3
#92
Cost, coverage & limits
Benchmark wins
—
—
Input price
$2.00 / M
$0.10 / M
Output price
$10.00 / M
$0.40 / M
Context window
1,000,000
65,536

Capability indexes

Additional strengths measured across groups of related public benchmarks

2 shared
Index
Claude Sonnet 5.5
Step-3.5-Flash
Math
36.9#34
33.9#52
Tool use
34.0#2
13.3#103
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

47 reported for Claude Sonnet 5.5 · 7 for Step-3.5-Flash

No common benchmarks found

Claude Sonnet 5.5 and Step-3.5-Flashdon'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

Pricing Analysis

Price comparison per million tokens

Step-3.5-Flash costs less

For input processing, Claude Sonnet 5.5 ($2.00/1M tokens) is 20.0x more expensive than Step-3.5-Flash ($0.10/1M tokens).

For output processing, Claude Sonnet 5.5 ($10.00/1M tokens) is 25.0x more expensive than Step-3.5-Flash ($0.40/1M tokens).

In conclusion, Claude Sonnet 5.5 is more expensive than Step-3.5-Flash.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Fri Oct 02 2026 • llm-stats.com
Anthropic
Claude Sonnet 5.5
Input tokens$2.00
Output tokens$10.00
Best providerAnthropic
StepFun
Step-3.5-Flash
Input tokens$0.10
Output tokens$0.40
Best providerStepFun
Notice missing or incorrect data?

Context Window

Maximum input and output token capacity

Claude Sonnet 5.5 accepts 1,000,000 input tokens compared to Step-3.5-Flash's 65,536 tokens. Claude Sonnet 5.5 can generate longer responses up to 128,000 tokens, while Step-3.5-Flash is limited to 8,192 tokens.

Anthropic
Claude Sonnet 5.5
Input1,000,000 tokens
Output128,000 tokens
StepFun
Step-3.5-Flash
Input65,536 tokens
Output8,192 tokens
Fri Oct 02 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Claude Sonnet 5.5 supports multimodal inputs, whereas Step-3.5-Flash does not.

Claude Sonnet 5.5 can handle both text and other forms of data like images, making it suitable for multimodal applications.

Claude Sonnet 5.5

Text
Images
Audio
Video

Step-3.5-Flash

Text
Images
Audio
Video

License

Usage and distribution terms

Claude Sonnet 5.5 is licensed under a proprietary license, while Step-3.5-Flash uses Apache 2.0.

License differences may affect how you can use these models in commercial or open-source projects.

Claude Sonnet 5.5

Proprietary

Closed source

Step-3.5-Flash

Apache 2.0

Open weights

Release Timeline

When each model was launched

Claude Sonnet 5.5 was released on 2026-09-28, while Step-3.5-Flash was released on 2026-02-02.

Claude Sonnet 5.5 is 8 months newer than Step-3.5-Flash.

Claude Sonnet 5.5

Sep 28, 2026

4 days ago

7mo newer
Step-3.5-Flash

Feb 2, 2026

8 months ago

Knowledge Cutoff

When training data ends

Claude Sonnet 5.5 has a documented knowledge cutoff of 2026-06-01, while Step-3.5-Flash's cutoff date is not specified.

We can confirm Claude Sonnet 5.5's training data extends to 2026-06-01, but cannot make a direct comparison without Step-3.5-Flash's cutoff date.

Claude Sonnet 5.5

Jun 2026

Step-3.5-Flash

—

Provider Availability

Claude Sonnet 5.5 is available from Anthropic. Step-3.5-Flash is available from StepFun.

Claude Sonnet 5.5

anthropic logo
Anthropic
Input Price:Input: $2.00/1MOutput Price:Output: $10.00/1M

Step-3.5-Flash

stepfun logo
StepFun
Input Price:Input: $0.10/1MOutput Price:Output: $0.40/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?

Judge for yourself.

Run your own prompts against Claude Sonnet 5.5 and Step-3.5-Flash side-by-side, then vote on the output you prefer.

Claude Sonnet 5.5
✓ Preferred
Step-3.5-Flash
Open in Playground

FAQ

Common questions about Claude Sonnet 5.5 vs Step-3.5-Flash.

Which is better, Claude Sonnet 5.5 or Step-3.5-Flash?

Claude Sonnet 5.5 leads the LLM Stats Score 58.0 to 37.1. Claude Sonnet 5.5 is made by Anthropic and Step-3.5-Flash is made by StepFun. 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 Step-3.5-Flash 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%. Step-3.5-Flash scores AIME 2025: 97.3%, Tau-bench: 88.2%, LiveCodeBench v6: 86.4%, IMO-AnswerBench: 85.4%, SWE-Bench Verified: 74.4%.

Is Claude Sonnet 5.5 cheaper than Step-3.5-Flash?

Step-3.5-Flash is 20.0x cheaper for input tokens. Claude Sonnet 5.5 costs $2.00/M input and $10.00/M output via anthropic. Step-3.5-Flash costs $0.10/M input and $0.40/M output via stepfun.

What are the context window sizes for Claude Sonnet 5.5 and Step-3.5-Flash?

Claude Sonnet 5.5 supports 1.0M tokens and Step-3.5-Flash supports 66K 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 Step-3.5-Flash?

Key differences include LLM Stats Score (58.0 vs 37.1), context window (1.0M vs 66K), input pricing ($2.00 vs $0.10/M), multimodal support (yes vs no), licensing (Proprietary vs Apache 2.0). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Sonnet 5.5 and Step-3.5-Flash?

Claude Sonnet 5.5 is developed by Anthropic and Step-3.5-Flash is developed by StepFun.

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