StepFun

Step 3.5 Flash

CTX256K

64Quality

Reasoning · Tools

Input$0.10/M

Output$0.30/M

StepFun flash lane for quick multimodal reasoning and coding assistance

Open weightsApache 2.0768/1040

Drag to turn

StepFunTextCommon

Step 3.5 Flash

StepFun flash lane for quick multimodal reasoning and coding assistance

step-3.5-flash

Type: Text
Quality: 64 · Top 36% on the LMArena Text
Context window: 256,000 tokens
Max output: 256,000 tokens
Input price: $0.10 / 1M tokens
Output price: $0.30 / 1M tokens
Cache read: $0.02 / 1M tokens
Cache write: —
Parameters: 199B (199,384,301,376)
Downloads: 260K in the last 30 days
Likes: 840
Access to weights: Open download
Released: Jan 29, 2026
Knowledge cutoff: Jan 2025
Takes in: Text
Puts out: Text
Reasoning: Yes
Tool calling: Yes
Structured output: No
File attachments: No
Access: Open weights
License: Apache 2.0
Rarity: Common
Set number: 768/1040

Open StepFun docs Weights on Hugging Face Quality 64 Where to run it 17 Evolution 1/2 Race it 11 tok/s Meet its creature Battle Phi-4-mini-reasoning

License read from the model’s Hugging Face card. Specs from models.dev, downloads from Hugging Face, last changed Oct 18, 2026. Official source: platform.stepfun.ai.

How good is it?

Public leaderboard scores for Step 3.5 Flash, refreshed daily from Epoch AI and LMArena.

Top 36% of the 416 models on the LMArena Text: #150.

Quality is the share of a leaderboard’s models this one beats, from 0 to 100. Chat models are rated on Epoch AI’s Capabilities Index when it lists them, otherwise on LMArena; image and video models on LMArena’s image and video arenas.

Leaderboards

LMArena Text#150 of 416
People compare two anonymous answers and vote for the better one.1,403 rating
LMArena Text · Coding#127 of 411
The text arena’s coding prompts only.1,436 rating
LMArena Text · Math#144 of 400
The text arena’s math prompts only.1,408 rating
LMArena Text · Creative writing#159 of 414
The text arena’s creative writing prompts only.1,357 rating

Scores from LMArena, licensed CC BY 4.0. Boards list models under their own names, so a close match is shown with the name it was scored under. Credits

Where to run it

15 providers sell Step 3.5 Flash through an API, and 2 Hugging Face hosts serve it. Prices are per million tokens, cheapest first.

CheapestCommandCode$0.09 in · $0.30 out
Free to try1 providerNvidia
From the labStepFun (Global)$0.10 in · $0.30 out
Fastest on Hugging FaceDeepInfra11 tokens/s

API providers

Provider	Input	Output	Context
NvidiaFree`stepfun-ai/step-3.5-flash`	Free	Free	256K
CommandCodeCheapest paid`stepfun/Step-3.5-Flash`	$0.09	$0.30	256K
Eden AI`deepinfra/stepfun-ai/Step-3.5-Flash`	$0.09	$0.30	262K
EmpirioLabs AI`step-3-5-flash`	$0.10	$0.30	256K
Kilo Gateway`stepfun/step-3.5-flash`	$0.10	$0.30	262K
NanoGPT`stepfun-ai/step-3.5-flash`	$0.10	$0.30	262K
OpenRouter`stepfun/step-3.5-flash`	$0.10	$0.30	262K
SiliconFlow`stepfun-ai/Step-3.5-Flash`	$0.10	$0.30	262K
SiliconFlow (China)`stepfun-ai/Step-3.5-Flash`	$0.10	$0.30	262K
StepFun (China)`step-3.5-flash`	$0.10	$0.30	256K

Show 5 more providers

Provider	Input	Output	Context
StepFun (Global)Official`step-3.5-flash`	$0.10	$0.30	256K
ZenMux`stepfun/step-3.5-flash`	$0.10	$0.30	256K
Qiniu`stepfun/step-3.5-flash`	—	—	64K
StepFun Step Plan (China)`step-3.5-flash`	—	—	256K
StepFun Step Plan (Global)`step-3.5-flash`	—	—	256K

Hugging Face Inference Providers

Host	Input	Output	Context	Speed	First token
DeepInfraFastestTools	$0.10	$0.30	262K	11 tok/s	0.5s
Featherless	—	—	—	—	—

From models.dev and Hugging Face, checked daily. Resellers’ listings can lag behind their price pages, so confirm with the provider before you commit.

Face off

Current text models from other labs at a similar output price.

Step 3.5 Flash

Step 3.5 Flash

How good is it?

Leaderboards

Where to run it

API providers

Hugging Face Inference Providers

Face off

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