How much does Step 3.5 Flash cost?

Step 3.5 Flash costs $0.10 per million input tokens and $0.30 per million output tokens. For a typical conversation (~2,000 tokens), that's approximately $0.001 per message.

What benchmarks has Step 3.5 Flash been tested on?

Step 3.5 Flash has been evaluated on 10 benchmarks. Top scores: Chatbot Arena Elo — Overall: 1391.4, OpenCompass — AIME2025: 95.7, OpenCompass — IFEval: 93.2.

Is Step 3.5 Flash open source?

Yes, Step 3.5 Flash is open source.

How does Step 3.5 Flash compare to Gemini 3.1 Pro Preview?

Step 3.5 Flash has an average score of 89.5 while Gemini 3.1 Pro Preview scores 90.0. Gemini 3.1 Pro Preview slightly outperforms Step 3.5 Flash overall. Step 3.5 Flash costs $0.10/1M input vs Gemini 3.1 Pro Preview at $2.00/1M input. See full comparison →

Home/Models/Step 3.5 Flash

Step 3.5 Flash

Name: Step 3.5 Flash
Price: 0.1 USD
Author: stepfun

by stepfun · Released Jan 2026

Open Source

89.5

avg score

Rank #8

Compare

Top 3% of all models

Context

262K tokens (~131 books)

Input $/1M

$0.10

Output $/1M

$0.30

Type

text

License

Open Source

Benchmarks

10 tested

Data updated today

About

Step 3.5 Flash is StepFun's most capable open-source foundation model. Built on a sparse Mixture of Experts (MoE) architecture, it selectively activates only 11B of its 196B parameters per token....

Tested on 10 benchmarks with 76.9% average. Top scores: Chatbot Arena Elo — Overall (1391.4%), OpenCompass — AIME2025 (95.7%), OpenCompass — IFEval (93.2%).

Capabilities

coding

83.9

#2 globally

math

95.7

#3 globally

knowledge

62.9

#34 globally

speed

67.5

#24 globally

language

93.2

#5 globally

Benchmark Scores

Compare All

Tested on 10 benchmarks · Ranked across 6 categories

Score Distribution (all 233 models)

0255075100

▲ You are here

codingCompare coding →

OpenCompass — LiveCodeBenchV6

OpenCompass Live Code Bench v6. Fresh competitive programming problems to evaluate code generation without memorization.

83.9—

mathCompare math →

OpenCompass — AIME2025

OpenCompass evaluation on AIME 2025 problems. Tests mathematical reasoning on fresh competition problems.

95.7—

knowledgeCompare knowledge →

OpenCompass — GPQA-Diamond

OpenCompass evaluation of GPQA Diamond. PhD-level science questions from the hardest subset.

83.7—

OpenCompass — MMLU-Pro

OpenCompass MMLU-Pro evaluation. Harder knowledge test with more answer choices.

83.5—

OpenCompass — HLE

OpenCompass evaluation of Humanitys Last Exam. Expert-level cross-discipline knowledge test.

21.6—

Quick compare:

vs Gemini 3.1 Pro Preview

vs GPT-5 Chat

vs Qwen3.6 Plus

Excellent (85+) Good (70-85) Average (50-70) Below (<50)

Model Family · stepfun Step 3.5

Step 3.5 FlashJan 2026

76.9

$0.10/M in262Kctx10 benchmarks

Step 3.5 Flash (free)Jan 2026

$0.00/M in(-0.10)256Kctx(-6K)

See the full Step 3.5 family →

Similar Models

Gemini 3.1 Pro Preview

Links

Info

stepfun Pricing explorer Developers · API

Research

Documentation

Community

Source Code

BenchGecko API

step-3-5-flash

Specifications

Typetext
Context262K tokens (~131 books)
ReleasedJan 2026
LicenseOpen Source
StatusActive
Cost / Message~$0.001

Available On

stepfun$0.10

Frequently Asked Questions

Step 3.5 Flash is an open-source text AI model by stepfun, released in January 2026. It has an average benchmark score of 89.5. Context window: 262K tokens.

Benchmarks

Chatbot Arena Elo — Overall OpenCompass — AIME2025 OpenCompass — IFEval OpenCompass — LiveCodeBenchV6 OpenCompass — GPQA-Diamond

stepfun · Provider stepfun · Economy All Models Compare Models Pricing Developers · API Context Window · Glossary

Step 3.5 Flash

Frequently Asked Questions

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