StepFun

⚡️ Step 3.5 Flash is coming: Fast Enough to Think. Reliable Enough to Act！ We’re dropping our most capable open-source foundation model yet. Frontier reasoning meets extreme efficiency. It leverages a sparse Mixture of Experts (MoE) architecture, 196B total → 11B active. Key Capabilities: ✅Reasoning at Speed: MTP-3 powered throughput at 100–300 tok/s (350 tok/s peak for single-stream coding tasks). ✅Agentic Power: ⚡️ 74.4% SWE-bench Verified ⚡️ 51.0% Terminal-Bench 2.0. Proven stability for complex, long-horizon tasks. ✅256K Efficient Context: 3:1 SWA ratio + Full Attention. Massive datasets or long codebases support with minimal overhead. Consistent performance, hybrid efficiency. ✅Local-First Deployment: Optimized for Mac Studio M4 Max, NVIDIA DGX Spark. Secure, private, and frontier-capable. Your data, your hardware, your agent. You can try Step 3.5 Flash right now: 👉 OpenRouter: openrouter.ai/stepfun/step-3… 👉 GitHub: github.com/stepfun-ai/Ste… 👉 HuggingFace：huggingface.co/stepfun-ai/Ste… 👉 Blog：static.stepfun.com/blog/step-3.5-… 👉 ModelScope: modelscope.cn/models/stepfun… 🌌 The Next：Step 4 training is officially LIVE！ We're calling on the world's boldest builders to co-creat the Step 4 right now. Let's define the Agentic Era together! Join our Discord：discord.gg/RcMJhNVAQc

our SFT dataset is now on @ModelScope2022 too! modelscope.cn/datasets/stepf…

the last missing piece. our SFT training dataset is now available at huggingface.co/datasets/stepf…

great to see teams building on Step 3.5 Flash in production 🔨

@mudler_it awesome to hear! welcome aboard 🔨 let us know if there's anything we can help with during the switch.

Another update from my team: we are switching to Step 3.5 Flash as base! great model for its size! For my use it completely destroys Qwen 3.5 122b! reports.localai.io/posts/step-3.5…

Step 3.5 Flash is now open source: model weights and full training framework (SteptronOSS), released together.🚀 196B total, 11B active. SWE-bench Verified 74.4% / Terminal-Bench 2.0 51.0%. - MoE architecture: 288 routed experts + 1 shared, Top-8 activation per token - MTP-3: predicts 4 tokens per forward pass, 100–300 tok/s typical, 350 tok/s peak - 3:1 SWA ratio (1 full attention + 3 sliding window layers): 256K context at lower compute cost - 💻 Runs on Mac Studio M4 Max and NVIDIA DGX Spark - SteptronOSS: SFT, continued pretraining, RL (WIP) - Apache 2.0 Two checkpoints released: Step-3.5-Flash-Base and Step-3.5-Flash-Base-Midtrain. 🤖 Base: modelscope.cn/models/stepfun… 🤖 Midtrain: modelscope.cn/models/stepfun… 🔧 Training Framework: github.com/stepfun-ai/Ste… 📄 Paper: modelscope.cn/papers/2602.10…

@boyuan_chen @ModelScope2022 exactly our thinking. that's why we released SteptronOSS alongside the weights 🔨

@ModelScope2022 11B active out of 196B total, less than 6% of params lit up per token. that's aggressive sparsity. honestly more interested in the training framework release than the weights - open weights are table stakes now, open training code is what actually pushes the field forward.

@ModelScope2022 thanks @ModelScope2022 for the support! 🤝 for those asking — yes, SFT data is coming soon.

we're seeing more and more agents built on Step 3.5 Flash through @openclaw — and we love it. to help you get started, here's our OpenClaw cookbook 👇 🔗 github.com/stepfun-ai/Ste…

now on @ModelScope2022 too 👇 Base: modelscope.cn/models/stepfun… Midtrain: modelscope.cn/models/stepfun…

"can we get the base model?" sure. here's two. "can we get the code?" sure. here's SteptronOSS. "what about the SFT data?" coming soon. maximum sincerity, minimum barriers. - Step 3.5 Flash Base — pretrained foundation - Step 3.5 Flash Base-Midtrain — code, agents & long-context - SteptronOSS — open-sourced, ready for your custom workflows - SFT Data — coming soon for reference not just the final checkpoint — a customizable pipeline. 🤗 huggingface.co/stepfun-ai/Ste… 🤗 huggingface.co/stepfun-ai/Ste… 💻 github.com/stepfun-ai/Ste…

Huge respect for @JustinLin610 and his contributions to Qwen — a true champion of open-source AI. Wishing you all the best on your next adventure! 🙏 We'll carry on the spirit of open source.

AMA is live! 🙌 Our team (including CEO, CTO & Chief Scientist) is answering your questions on r/LocalLLaMA today 8-11 AM PST. Jump in 👇 reddit.com/r/LocalLLaMA/c…

thanks for reporting this — the repetitive output loop is a known issue we're actively working on (related to token efficiency optimization). for the freeze during think phase, could you share which OpenCode version you're using? that'll help our team debug faster. you can also report this on our github for quicker tracking 🙏

@StepFun_ai @StepFun_ai Would you be able to fix this? Sometimes it freezes during the “think” phase in OpenCode. I am forced to tell it: “Continue.”

64B tokens on @openclaw this week. your users are putting Step 3.5 Flash to work 🫡 thanks for building this @steipete

@teortaxesTex @CyouSakura appreciate the thoughtful analysis! we're heads down building 🔨

Very bullish on @StepFun_ai, can see them getting onto the Upstarts tier with Kimi/Minimax/GLM, maybe even overtaking Why: they have a crazy strong and crazy fast model. It's brittle but *they* know how to harness it. PaCoRe is RSI-pilled as is @CyouSakura Step-Big will be a leap

AMA is back on! Big thanks to the r/LocalLLaMA mods for helping us set this up properly. This Thursday, 8-11 AM PST — ask us anything about Step 3.5 Flash 🙌

Update: AMA postponed — our r/LocalLLaMA post was removed by mods and we’re working to reschedule. New date coming soon 🙏

You called Step 3.5 Flash “the new local LLM king.” We heard you — now ask us anything. Our team is doing a live AMA on r/LocalLLaMA 📅 Feb 13 | 8-11 AM PST Architecture, deployment, known issues, what’s coming next — everything’s on the table. reddit.com/r/LocalLLaMA/s…

@OG_TAngent @bensig 🙌

@bensig Try @StepFun_ai step3.5

Cancelled my $200 ChatGPT plan. Going full Claude now.

@Norwakar cheat code unlocked 🔓 wait till you try deep research beta testing

okay but why does @StepFun_ai let me choose exactly where AI searches and nobody else does🙌 academic papers? toggle gov data? toggle code tutorials? toggle my own files? toggle felt like a cheat code honestly

@VivancosDavid "The revelation" — we'll take that 🙏 thanks for the thorough testing, David!

Time for a new artificiology.com #EAGI (brains) 🔥🔥🔥 UPDATE, after the last deep review, 2026 is moving fast as expected. First of all welcome to the new kid in the block @StepFun_ai with a triumphant #2 entry with step-3.5-flash a true killer and also the best price per token for your 🦞 #openclaw @openclaw thanks @steipete for releasing it! this model is free atm at @openrouter btw. To de details: maybe @deepseek_ai will release V4 soon and also Gemini 3.1 is about to, but meanwhile, these are the current results: Remember that I test only native models not agregators, with custom real benchmarks: My results on Feb 12th 2026: 🥇1st⬆️ @AnthropicAI first time first with 4.6 Opus is killer model but expensive... 🥈2nd⬆️ The revelation @StepFun_ai step-3.5-flash also best $ for 🦞 3th⬆️ @Zai_org biggest raise with the great new model #GLM5 3rd (tie)⬇️ @Kimi_Moonshot #Kimi K2.5 Is a terrific new model 4th ⬇️ @GoogleDeepMind waiting for 3.1 and beyond... 4th (tie)⬇️ @OpenAI even if I agree the new codex 5.3 is delivering, the other models context size for use in chat app is just crap, will the former king lose the battle? 5th ⬇️ @xai #Grok is not there yet when a new good model? 5th (tie) ⬇️@Alibaba_Qwen are still great models still waiting for new ones 6th⬇️ @deepseek_ai also waiting for the next big one? 7th ⬆️ @MiniMax_AI M2.1 keeps rising 2.5 soon? 8th ⬆️ @TheInclusionAI with #Ling & #Ring model are still good models but there is a lot of competition atm 10th⬇️ @Xiaomi stil in the stage with #Mimo 10th↕️ @Meituan_LongCat Flash Thinking is also a great model worth using. Thanks to @huggingface again for delivering the open models! Learn more by joining artificiology.com - Artificiology (también en español en artificiologia.com ) BTW this is this visible player list, stay tuned also for the work at @_Qubic_ #aigarth and #openscience #Neuraxon #AI #Artificiology #ArtificiologyRanking #Aritificiologia #AGIRanking #AGIRace