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StepFun (阶跃星辰)Open-weight·262K context·— params

Step 3.5 Flashstepfun/step-3-5-flash

Step 3.5 Flash is StepFun’s open-weight text reasoning model for coding, tool use and high-throughput workloads. It remains available alongside the multimodal Step 3.7 Flash and the newer Step 5 Preview.

Cheapest blended:$0.15 / 1M tokenson StepFun · 1 provider listed

Availability and billing notes

Reviewed September 21, 2026 · check the linked provider documentation for later changes.

Official source 1 →Official source 2 →

Pricing across providers

Sort by:
ProviderInput /1MOutput /1MBlended /1MLatency p50FormatFreshnessAction
StepFun
step-3.5-flash

International platform, USD.

$0.1
Cached $0.02
$0.3$0.15—OpenAI-compatiblePrice 1mo agoTry →

Affiliate disclosure: We may earn a commission from qualified signups. Pricing independence is enforced at the data layer — see our Editorial Independence Policy.

Works with

Point any of these clients at a hosting's base URL — they all speak at least one of this model's endpoint protocols (OPENAI_COMPATIBLE).

Capabilities

  • chat
  • reasoning
  • code

Languages: zh, en

Code samples

Example using StepFun — the cheapest hosting for this model as of last verification. Swap base_url and model to use a different provider from the matrix above.

from openai import OpenAI

client = OpenAI(
    api_key="YOUR_API_KEY",
    base_url="https://api.stepfun.ai/v1",
)

response = client.chat.completions.create(
    model="step-3.5-flash",
    messages=[{"role": "user", "content": "Hello!"}],
)
print(response.choices[0].message.content)

Technical specs

Context
262K
Max output
66K
Parameters
—
Release
—
Training cutoff
—
License
—
Hugging Face →Official documentation →

Similar models

Compare with

  • Step 3.5 Flash vs DeepSeek V3.1
    Comparison planned — not yet published
  • Step 3.5 Flash vs R1
    Comparison planned — not yet published
  • Step 3.5 Flash vs DeepSeek V3
    Comparison planned — not yet published

Frequently asked

How much does Step 3.5 Flash cost?+
The cheapest public hosting is $0.15 per 1M blended tokens on StepFun. 1 total providers are listed above with per-input / per-output / cached pricing.
Is Step 3.5 Flash open-source? Can I fine-tune it?+
Step 3.5 Flash has published weights. License: see the official repository. Review the linked repository and license for deployment, fine-tuning and commercial-use conditions.
Is Step 3.5 Flash OpenAI-compatible?+
At least one listed hosting exposes an OpenAI-compatible API, so you can point an existing openai SDK client at the Provider's base_url and use the Provider's model name. See the Code Samples above for a copy-pasteable example.
What's the maximum context window for Step 3.5 Flash?+
The model supports up to 262,144 tokens of context (input + output). Some hosted versions may impose a smaller limit — check the "Context" column in the pricing matrix for each provider.