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StepFun vs StreamLake
Two Chinese AI providers with different specialties. StepFun ships open multimodal models; StreamLake sells Kuaishou's proprietary coding model and cloud capacity.
By The Subconscious Team · Updated
StepFun vs StreamLake: key differences
Both providers serve first-party inference from China, which sets the same baseline caution for US and EU buyers. Past that, they diverge. StepFun is a Shanghai lab with efficient multimodal models, including Step 3.7 Flash, a 198B mixture-of-experts vision-language model with 11B active parameters, 256K context and Apache 2.0 weights, at $0.20 in and $1.15 out. StreamLake is Kuaishou's AI cloud, and its headline model is KAT-Coder-Pro V2.5, a proprietary agentic coding model that Kuaishou trained with large-scale agentic reinforcement learning for repository-level work.
The choice follows the job. For coding agents, StreamLake offers a KwaiKAT Coding Plan and a Claude-protocol proxy that drops into Claude Code or OpenClaw. For vision, video and speech work, StepFun's models are built for it, and its open weights run on vLLM and SGLang wherever a team wants. StreamLake adds bare-metal compute for Chinese internet businesses, while StepFun's models reach Western users through OpenRouter. StreamLake's docs lead with China, and StepFun trails frontier models on hard multimodal reasoning.
What StepFun and StreamLake do
StepFun
StepFun is a Shanghai AI lab known for efficient multimodal models, with a mix of proprietary API models and open-weight releases. In September 2026 it launched Step 5 Preview, its new flagship for agentic work: a 600B-total, 27B-active mixture-of-experts model with 1M context and text and image input, which Artificial Analysis scores level with Kimi K3. It costs $1.00 in and $2.70 out per million tokens, and its weights followed on Hugging Face in mid-October under the custom StepFun Model License 1.0, which allows commercial use with restrictions. Its cheaper workhorse, Step 3.7 Flash, came out in May 2026 as a 198B mixture-of-experts vision-language model with only 11B active parameters. It has 256K context, selectable reasoning levels, tool use and structured outputs, and it ships under Apache 2.0. StepFun's own API prices it at $0.20 in and $1.15 out per million tokens, and OpenRouter carries it too.
Example models: Step 5 Preview, Step 3.7 Flash
Full StepFun profileStreamLake
StreamLake is the AI cloud brand of Kuaishou, the Chinese short-video company behind the Kling video models. It sells model-as-a-service inference and bare-metal compute to internet businesses, drawing on the infrastructure Kuaishou built to serve video at massive scale. Its developer site offers APIs, SDKs and integration guides aimed at taking teams from testing to production, and its Vanchin platform also hosts third-party open models from DeepSeek and GLM, most recently DeepSeek V4.1 Flash 1017.
Example models: KAT-Coder-Pro V2.5, KAT-Coder-Air V2.5
Full StreamLake profileShould you choose StepFun or StreamLake?
StepFun
Choose StepFun for
- Vision, video and speech understanding at low cost
- Open weights to self-host outside China
- Access through OpenRouter
StreamLake
Choose StreamLake for
- Agentic coding on KAT-Coder in Claude Code
- A flat KwaiKAT Coding Plan
- Bare-metal capacity for businesses in China
StepFun vs StreamLake at a glance
| Attribute | StepFun | StreamLake |
|---|---|---|
| Model access | Open weights (Apache 2.0 or StepFun license) and API models | Proprietary coding models, plus hosted open models |
| Flagship models | Step 5 Preview, Step 3.7 Flash | KAT-Coder-Pro V2.5, KAT-Coder-Air V2.5 |
| Speed | ~128 tok/s on Step 3.7 Flash | Unknown |
| Price | $0.20 in, $1.15 out (Step 3.7 Flash) | $0.74 in, $2.96 out (Pro V2.5), or KwaiKAT Coding Plan |
| Customization | Open weights to fine-tune | Unknown |
| Deployment | First-party API, OpenRouter | MaaS API, bare metal |
| Long context | Up to 1M (Step 5 Preview); 256K on Step 3.7 Flash | 256K |
Frequently asked questions
What is the difference between StepFun and StreamLake?
Two Chinese AI providers with different specialties. StepFun ships open multimodal models; StreamLake sells Kuaishou's proprietary coding model and cloud capacity.
When should I choose StepFun over StreamLake?
Vision, video and speech understanding at low cost; Open weights to self-host outside China; Access through OpenRouter.
When should I choose StreamLake over StepFun?
Agentic coding on KAT-Coder in Claude Code; A flat KwaiKAT Coding Plan; Bare-metal capacity for businesses in China.
Is StepFun or StreamLake cheaper?
StepFun: $0.20 in, $1.15 out (Step 3.7 Flash). StreamLake: $0.74 in, $2.96 out (Pro V2.5), or KwaiKAT Coding Plan. The cheaper choice depends on the model and workload.
Which has more context, StepFun or StreamLake?
StepFun: Up to 1M (Step 5 Preview); 256K on Step 3.7 Flash. StreamLake: 256K.
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