StepFun · language model
Step 3.5 Flash: pricing, context and benchmarks
Step 3.5 Flash is StepFun's model released on January 29, 2026. It costs $0.1 per million input tokens and $0.3 per million output tokens, with a 262.1K-token context window. No independent score has been published for it so far.
What you need to know about Step 3.5 Flash
StepFun, based in China, put Step 3.5 Flash online on January 29, 2026. It accepts text as input and produces text. Its context window reaches 262,144 tokens, larger than 58 % of the models in the registry, and it can write up to 65,536 tokens in one go.
It has been available for about 9 months, long enough for its prices and scores to have settled.
Step 3.5 Flash pricing
On OpenRouter, Step 3.5 Flash costs $0.1 per million input tokens and $0.3 per million output tokens. Counting three tokens read for every token written, its average price is $0.15 per million, more expensive than 17 % of paid models (5.1 times cheaper than the median of $0.76).
A concrete example: a task that sends 2,000 tokens (about 1,500 words) and receives a 500-token answer costs $0.0004. At 1,000 tasks a day, budget $11 a month. The price calculator redoes this with your own volumes.
Performance and benchmarks
Epoch AI does not yet publish a capabilities index for Step 3.5 Flash. We therefore show no made-up performance rating: only price, context and features count towards its score.
Features, privacy and local use
- It supports tool calling, so it can drive an AI agent, call APIs or MCP servers.
- It is a reasoning model: it "thinks" before answering, which helps on hard tasks but uses more output tokens.
Its weights are open and downloadable from Hugging Face (apache-2.0 licence): you can run it on your own machines without sending your data to a third party. With 199,384,301,376 billion parameters, it needs about 111,414,660,537 GB of memory at 4-bit quantisation. Check with the VRAM calculator. It was downloaded 265,299 times on Hugging Face last month.
Other StepFun models
| Model | Released | Avg. price | ECI |
|---|---|---|---|
| Step 5 Preview | Oct 8, 2026 | $1.43 | — |
| Step 3.7 Flash | May 28, 2026 | $0.44 | — |
Verdict
Computed score: 77/100, from public data (performance, price, context, features).
Strengths
- Low price: cheaper than 83 % of paid models.
- Open weights: self-hostable, your data stays with you.
Limitations
- No independent score published: performance cannot be verified.
- Text only: reads neither images nor files.
Avoid if…
- you want to host it on a single consumer computer (≈ 111,414,660,537 GB needed at 4-bit).
Alternatives
- Ministral 3 8B 2512$0.15
- Hy3$0.15
- Seed-2.0-Mini$0.18
- Qwen3 30B A3B Instruct 2507$0.14
- Qwen3.5-9B$0.19
- Ternary Bonsai 2 27B$0.18
Comparisons and tools
Learn more
Frequently asked questions
How much does Step 3.5 Flash cost?
$0.1 per million input tokens and $0.3 per million output tokens on OpenRouter (checked October 25, 2026). A task with 2,000 tokens read and 500 written costs $0.0004.
How big is Step 3.5 Flash's context window?
262,144 tokens, roughly 197,000 words, with a maximum of 65,536 output tokens.
Can Step 3.5 Flash run locally?
Yes, its weights are published under the apache-2.0 licence. Expect about 111,414,660,537 GB of memory at 4-bit.
Is Step 3.5 Flash suitable for an AI agent?
Technically yes: it supports tool calling. Then check its cost for your volume.
What are the alternatives to Step 3.5 Flash?
The closest models on price and performance are Ministral 3 8B 2512, Hy3, and Seed-2.0-Mini.
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Neutrality. No affiliate links. No vendor pays to be reviewed, rated or ranked. Reviews are directed by François Chollet, neutral and factual, and every data point is dated and sourced. How we score