Model Comparison

Claude Sonnet 4 vs Step-3.5-Flash

Step-3.5-Flash significantly outperforms across most benchmarks. Step-3.5-Flash is 34.3x cheaper per token.

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Performance Benchmarks

Comparative analysis across standard metrics

2 benchmarks

Claude Sonnet 4 outperforms in 0 benchmarks, while Step-3.5-Flash is better at 2 benchmarks (AIME 2025, SWE-Bench Verified).

Step-3.5-Flash significantly outperforms across most benchmarks.

Thu Apr 16 2026 • llm-stats.com

Arena Performance

Human preference votes

Pricing Analysis

Price comparison per million tokens

Step-3.5-Flash costs less

For input processing, Claude Sonnet 4 ($3.00/1M tokens) is 30.0x more expensive than Step-3.5-Flash ($0.10/1M tokens).

For output processing, Claude Sonnet 4 ($15.00/1M tokens) is 37.5x more expensive than Step-3.5-Flash ($0.40/1M tokens).

In conclusion, Claude Sonnet 4 is more expensive than Step-3.5-Flash.*

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

Lowest available price from all providers
Thu Apr 16 2026 • llm-stats.com
Anthropic
Claude Sonnet 4
Input tokens$3.00
Output tokens$15.00
Best providerAnthropic
StepFun
Step-3.5-Flash
Input tokens$0.10
Output tokens$0.40
Best providerStepFun
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

Claude Sonnet 4 accepts 200,000 input tokens compared to Step-3.5-Flash's 65,536 tokens. Claude Sonnet 4 can generate longer responses up to 64,000 tokens, while Step-3.5-Flash is limited to 8,192 tokens.

Anthropic
Claude Sonnet 4
Input200,000 tokens
Output64,000 tokens
StepFun
Step-3.5-Flash
Input65,536 tokens
Output8,192 tokens
Thu Apr 16 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Claude Sonnet 4 supports multimodal inputs, whereas Step-3.5-Flash does not.

Claude Sonnet 4 can handle both text and other forms of data like images, making it suitable for multimodal applications.

Claude Sonnet 4

Text
Images
Audio
Video

Step-3.5-Flash

Text
Images
Audio
Video

License

Usage and distribution terms

Claude Sonnet 4 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 4

Proprietary

Closed source

Step-3.5-Flash

Apache 2.0

Open weights

Release Timeline

When each model was launched

Claude Sonnet 4 was released on 2025-05-22, while Step-3.5-Flash was released on 2026-02-02.

Step-3.5-Flash is 9 months newer than Claude Sonnet 4.

Claude Sonnet 4

May 22, 2025

10 months ago

Step-3.5-Flash

Feb 2, 2026

2 months ago

8mo newer

Knowledge Cutoff

When training data ends

Neither model specifies a knowledge cutoff date.

Unable to compare the recency of their training data.

No cutoff dates available

Provider Availability

Claude Sonnet 4 is available from Anthropic, Bedrock, Google. Step-3.5-Flash is available from StepFun.

Claude Sonnet 4

anthropic logo
Anthropic
Input Price:Input: $3.00/1MOutput Price:Output: $15.00/1M
bedrock logo
AWS Bedrock
Input Price:Input: $3.00/1MOutput Price:Output: $15.00/1M
google logo
Google
Input Price:Input: $3.00/1MOutput Price:Output: $15.00/1M

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

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Key Takeaways

Anthropic
Larger context window (200,000 tokens)
Supports multimodal inputs
StepFun
Less expensive input tokens
Less expensive output tokens
Has open weights
Higher AIME 2025 score (97.3% vs 70.5%)
Higher SWE-Bench Verified score (74.4% vs 72.7%)
AnthropicClaude Sonnet 4
StepFunStep-3.5-Flash
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Detailed Comparison

AI Model Comparison Table
Feature
Anthropic
Claude Sonnet 4
StepFun
Step-3.5-Flash

FAQ

Common questions about Claude Sonnet 4 vs Step-3.5-Flash

Step-3.5-Flash significantly outperforms across most benchmarks. Claude Sonnet 4 is made by Anthropic and Step-3.5-Flash is made by StepFun. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.
Claude Sonnet 4 scores MMMLU: 86.5%, TAU-bench Retail: 80.5%, GPQA: 75.4%, MMMU: 74.4%, SWE-Bench Verified: 72.7%. 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%.
Step-3.5-Flash is 30.0x cheaper for input tokens. Claude Sonnet 4 costs $3.00/M input and $15.00/M output via anthropic. Step-3.5-Flash costs $0.10/M input and $0.40/M output via stepfun.
Claude Sonnet 4 supports 200K 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.
Key differences include context window (200K vs 66K), input pricing ($3.00 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.
Claude Sonnet 4 is developed by Anthropic and Step-3.5-Flash is developed by StepFun.