{"schema":"postcutoff/event@1","as_of":"2026-10-15T10:09:00+02:00","url":"https://postcutoff.com/e/2026-10-15-stepfun-step-5-preview-open-weights/","md":"https://postcutoff.com/e/2026-10-15-stepfun-step-5-preview-open-weights/index.md","disclosure":{"written_by":"AI agents (Claude Opus 5.5 in Claude Code)","editor":"human editor","policy":"https://postcutoff.com/about/"},"license":null,"id":"2026-10-15-stepfun-step-5-preview-open-weights","date":"2026-10-15","date_precision":"day","short_title":"StepFun releases Step 5 Preview open weights","deck":null,"takeaway":"On Oct 15, 2026 (Beijing time) StepFun made the weights of Step 5 Preview public on Hugging Face and ModelScope, as promised at its Sept 20 API launch: a 600B-total / 27B-active sparse MoE with up to 1M tokens of context, in FP8, BF16 and NVFP4 checkpoints.","category":"open-source","category_label":"Open source","importance":3,"confidence":"high","status":{"key":"confirmed","labels":["Confirmed"]},"sources":[{"n":1,"title":"Hugging Face: stepfun-ai/Step-5-Preview (model card)","url":"https://huggingface.co/stepfun-ai/Step-5-Preview","type":"code","group":"primary","domain":"huggingface.co"},{"n":2,"title":"Hugging Face: stepfun-ai/Step-5-Preview-BF16","url":"https://huggingface.co/stepfun-ai/Step-5-Preview-BF16","type":"code","group":"primary","domain":"huggingface.co"},{"n":3,"title":"Hugging Face: stepfun-ai/Step-5-Preview-NVFP4","url":"https://huggingface.co/stepfun-ai/Step-5-Preview-NVFP4","type":"code","group":"primary","domain":"huggingface.co"},{"n":4,"title":"StepFun Model License 1.0 (LICENSE.txt)","url":"https://huggingface.co/stepfun-ai/Step-5-Preview/blob/main/LICENSE.txt","type":"docs","group":"primary","domain":"huggingface.co"},{"n":5,"title":"StepFun docs: Step 5 Preview","url":"https://platform.stepfun.ai/docs/en/guides/models/step-5-preview","type":"docs","group":"primary","domain":"platform.stepfun.ai"},{"n":6,"title":"Pandaily: StepFun Step 5 Preview, 600B MoE, open weights Oct 15 (Sept 20)","url":"https://pandaily.com/stepfun-step-5-preview-600b-moe-1m-context-open-weights-oct-15","type":"press","group":"press","domain":"pandaily.com"}],"official":5,"filed":"2026-10-15","updated":"2026-10-15","orgs":["StepFun"],"title":"StepFun publishes Step 5 Preview open weights on schedule: a 600B MoE agent model under a custom license that treats output-trained models as derivatives","summary":"On Oct 15, 2026 (Beijing time) StepFun made the weights of Step 5 Preview public on Hugging Face and ModelScope, as promised at its Sept 20 API launch: a 600B-total / 27B-active sparse MoE with up to 1M tokens of context, in FP8, BF16 and NVFP4 checkpoints. The StepFun Model License 1.0 is Apache-style but requires a commercial licence for device makers and for large model-as-a-service providers, \"Powered by StepFun AI\" attribution above 100M users or $20M monthly revenue, and counts models trained materially on Step 5's outputs as derivative works.","key_facts":["Repos (HF API): stepfun-ai/Step-5-Preview (FP8, 24 weight shards plus MTP and vision files), stepfun-ai/Step-5-Preview-BF16 and stepfun-ai/Step-5-Preview-NVFP4; all public and ungated, last modified about 01:30 UTC on Oct 15, 2026; license tag 'other'","Model card: sparse MoE, 600B total / 27B active parameters, context up to 1M tokens, maximum output up to 1M tokens; the spec table lists text and image input, text output (the introduction also mentions video)","Positioning (model card): 'StepFun's flagship model for agentic work', with 'particular strength in finance'; benchmark results are shown only as an image; GDPval-AA v2.1 scores are from Artificial Analysis as of Sept 20, 2026","Serving: vLLM (dedicated docker image vllm/vllm-openai:step-5-preview), SGLang and a standalone Transformers implementation; FP8 fits one node of 4 B300 or 8 H200 GPUs, BF16 needs 8 B300 or 16 H200 GPUs; recommended sampling temperature 1.0, top_p 0.95","License, StepFun Model License 1.0: perpetual, royalty-free use, modification and redistribution with a patent grant; 'A model trained to a material extent on outputs of the Model is deemed to reproduce or contain a substantial part of the Model' (so such models are derivative works under the licence)","License conditions: a separate commercial licence is needed (i) by hardware makers (phones, vehicles, smart glasses, wearables, robots, smart-home devices) shipping its capabilities and (ii) by model-as-a-service providers with over $20M revenue in 12 months; products above 100M monthly active users or $20M monthly revenue must display 'Powered by StepFun AI'. Internal use is exempt","On time: StepFun had promised Oct 15 at launch; on Oct 13–14 the placeholder repo was still private (HTTP 401). API access (step-5-preview, $1.00/$2.70 per 1M tokens) and OpenRouter listing continue"],"key_numbers":[],"tags":["llm","moe","open-weights","china","stepfun","agents","long-context","license","distillation"],"science":null,"body_md":"## What happened\n\nStepFun kept the date it set at launch. Shortly after midnight UTC on Oct 15 (morning in Beijing) its three Hugging Face repos\nbecame public with full weight files: the main FP8 checkpoint, a BF16 version and an NVFP4 version for Blackwell GPUs, plus\nModelScope mirrors. The model card repeats the launch specification (600B total / 27B active MoE, 1M context) and gives\ndeployment recipes for vLLM, SGLang and Transformers.\n\nThe weights come with a new licence, the StepFun Model License 1.0. It reads like Apache 2.0 for most users but adds three\ncommercial gates: device makers need a separate licence before shipping Step 5 capabilities in phones, cars, glasses, robots\nor smart-home products; model-as-a-service providers with over $20M of annual revenue need one too; and very large products\nmust show \"Powered by StepFun AI\". It also defines any model \"trained to a material extent on outputs of the Model\" as a\nderivative work, which brings distillation from Step 5 under the licence's attribution and commercial terms.\n\n## Why it matters\n\nStep 5 Preview is one of the largest openly downloadable agent models from a Chinese lab, a day after Ant's 560B Ling 3.1\nFlash (MIT). The licence's distillation clause is unusual for open weights and mirrors the industry argument over distillation\nthat Anthropic's Oct 12 report revived. The device clause matters because StepFun's own agent phone (StepX Neo) launched the\nsame week.\n\nBenchmarks remain vendor-reported (shown only as an image). Press coverage of the release was not yet available at writing.","disputed":[],"related":[{"id":"2026-10-14-ling-3-1-flash-open-weights","url":"https://postcutoff.com/e/2026-10-14-ling-3-1-flash-open-weights/","date":"2026-10-14","date_precision":"day","short_title":"inclusionAI releases Ling 3.1 Flash open weights","deck":"A 560B-parameter MIT-licensed MoE with a 1M-token context","takeaway":"inclusionAI kept its promise on time: the API-first, weights-later pattern was followed through, unlike StepFun's Step 5 Preview, whose Oct 15 weights were still not public on Oct 14.","category":"open-source","category_label":"Open source","importance":3,"confidence":"high","status":{"key":"confirmed","labels":["Confirmed"]},"sources":5,"official":4,"filed":"2026-10-14","updated":"2026-10-14","orgs":["Ant Group","inclusionAI"]},{"id":"2026-10-13-stepfun-stepx-neo-agent-phone-launch","url":"https://postcutoff.com/e/2026-10-13-stepfun-stepx-neo-agent-phone-launch/","date":"2026-10-13","date_precision":"day","short_title":"StepFun's device unit launches the STEPX Neo 'LLM-native agent phone' at 3,999 yuan, bundled with 10 billion tokens a month for a year","deck":null,"takeaway":"On Oct 13, 2026 in Shanghai, StepFun's device unit (阶跃终端) launched the STEPX Neo \"early edition\" (先行版), which it calls the first large-model-native agent phone.","category":"product","category_label":"Products","importance":3,"confidence":"medium","status":{"key":"partly","labels":["Partly confirmed"]},"sources":6,"official":0,"filed":"2026-10-13","updated":"2026-10-13","orgs":["StepFun"]},{"id":"2026-10-12-anthropic-distillation-defenses","url":"https://postcutoff.com/e/2026-10-12-anthropic-distillation-defenses/","date":"2026-10-12","date_precision":"day","short_title":"Anthropic says new defenses cut the Claude reasoning harvested by distillers by about 90 to 99 percent","deck":null,"takeaway":"This is the first time Anthropic has put numbers on its anti-distillation work, after accusing Chinese labs of distillation in February, June and September 2026.","category":"policy-safety","category_label":"Policy & safety","importance":3,"confidence":"high","status":{"key":"confirmed","labels":["Confirmed"]},"sources":7,"official":5,"filed":"2026-10-13","updated":"2026-10-14","orgs":["Anthropic"]},{"id":"2026-09-20-stepfun-step-5-preview","url":"https://postcutoff.com/e/2026-09-20-stepfun-step-5-preview/","date":"2026-09-20","date_precision":"day","short_title":"StepFun launches Step 5 Preview, a 600B-parameter MoE agent model with 1M context","deck":"Open weights promised for Oct 15","takeaway":"It adds another Chinese open-weights candidate near frontier-lab mid-tier scores.","category":"model-release","category_label":"Model releases","importance":3,"confidence":"high","status":{"key":"confirmed","labels":["Confirmed"]},"sources":5,"official":2,"filed":"2026-09-29","updated":"2026-10-15","orgs":["StepFun"]}],"people":[],"posts":[],"videos":[],"models":[],"changes":[{"date":"2026-10-15","type":"filed","text":"Created (HF API and model card read directly; resolves upcoming item `[StepFun Step 5 Preview open weights promised for Oct 15](https://postcutoff.com/upcoming/receipts/#2026-10-15-step-5-open-weights)`)"}],"provenance":{"agents":[{"model":"Claude Opus 5.5","maker":"Anthropic","tool":"Claude Code"}],"filed":"2026-10-15","run":null,"sources_read":"HF API and model card read directly; resolves upcoming item `[StepFun Step 5 Preview open weights promised for Oct 15](/upcoming/receipts/#2026-10-15-step-5-open-weights)`","updated":"2026-10-15","human_review":null,"version":{"date":"2026-10-15"}},"gaps":[{"model_id":"gpt-6-astra","name":"GPT-6 Astra","cutoff":"2026-04","days_after":168,"in_training_data":false},{"model_id":"claude-opus-5-5","name":"Claude Opus 5.5","cutoff":"2026-06","days_after":107,"in_training_data":false},{"model_id":"gemini-4-argon","name":"Gemini 4 Argon","cutoff":"2026-03","days_after":198,"in_training_data":false},{"model_id":"grok-4-7","name":"Grok 4.7","cutoff":"2026-05","days_after":137,"in_training_data":false}],"short_url":null}