{"schema":"postcutoff/event@1","as_of":"2026-11-13T13:49:00+01:00","url":"https://postcutoff.com/e/2026-09-20-stepfun-step-5-preview/","md":"https://postcutoff.com/e/2026-09-20-stepfun-step-5-preview/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":"2026-09-20-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":"On Sept 20, 2026 StepFun released Step 5 Preview (step-5-preview), its flagship agentic model: a 600B total / 27B active sparse MoE with 92 layers, a 1M-token context and 64K max output, taking text, up to 60 images and video.","category":"model-release","category_label":"Model releases","importance":3,"confidence":"high","status":{"key":"confirmed","labels":["Confirmed"]},"sources":[{"n":1,"title":"StepFun docs: Pricing and Rate Limits","url":"https://platform.stepfun.ai/docs/en/guides/pricing/details","type":"docs","group":"primary","domain":"platform.stepfun.ai"},{"n":2,"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":3,"title":"MarkTechPost: StepFun launches Step 5 Preview","url":"https://www.marktechpost.com/2026/09/20/stepfun-launches-step-5-preview/","type":"press","group":"press","domain":"marktechpost.com"},{"n":4,"title":"Pandaily: StepFun Step 5 Preview, 600B MoE, open weights Oct 15","url":"https://pandaily.com/stepfun-step-5-preview-600b-moe-1m-context-open-weights-oct-15","type":"press","group":"press","domain":"pandaily.com"},{"n":5,"title":"Pandaily: StepFun's Step 5 Preview Comes to Tencent WorkBuddy, Free to Use Exclusively Until October 25","url":"https://pandaily.com/stepfun-step-5-preview-tencent-workbuddy-exclusive-free-access-oct-12-25","type":"press","group":"press","domain":"pandaily.com"}],"official":2,"filed":"2026-09-29","updated":"2026-10-15","orgs":["StepFun"],"title":"StepFun launches Step 5 Preview, a 600B-parameter MoE agent model with 1M context; open weights promised for Oct 15","summary":"On Sept 20, 2026 StepFun released Step 5 Preview (`step-5-preview`), its flagship agentic model: a 600B total / 27B active sparse MoE with 92 layers, a 1M-token context and 64K max output, taking text, up to 60 images and video. It costs $1.00 input ($0.05 cached) and $2.70 output per 1M tokens and reportedly scores 44 on the Artificial Analysis index. StepFun promises open weights on Oct 15.","key_facts":["Released Sept 20, 2026; model id step-5-preview","600B total / 27B active MoE, 92 layers (narrow-deep design)","Context 1M tokens; max output 64K; input text, up to 60 images, video (MP4 <128 MB)","Pricing per 1M tokens: $1.00 input (cache miss), $0.05 (cache hit), $2.70 output","Company/press-reported: AA Intelligence Index 44, FrontierFinance 66.4, DRACO 83.3, DeepSWE v1.1 67.7","Open weights promised for Oct 15, 2026 (HF placeholder stepfun-ai/Step-5-Preview-BF16); license not yet stated","Oct 12, 2026: StepFun announced that Step 5 Preview is available in Tencent's WorkBuddy office agent, free from Oct 12 to Oct 25 in an arrangement StepFun calls exclusive (Pandaily, citing IT Home); no word on pricing after the window or whether the model stays in WorkBuddy","StepFun's own pricing page (read Oct 13, 2026) lists the cache-hit input price at $0.10 per 1M tokens, not the $0.05 reported at launch; $1.00 input and $2.70 output are unchanged"],"key_numbers":[],"tags":["llm","moe","china","agents","reasoning","long-context"],"science":null,"body_md":"## What happened\n\nStepFun joined the 1M-context agent-model tier with a sparse MoE aimed at software engineering and finance work.\n\n## Why it matters\n\nIt adds another Chinese open-weights candidate near frontier-lab mid-tier scores. Check on Oct 15 whether the weights and license were released.","disputed":[],"related":[{"id":"2026-10-15-stepfun-step-5-preview-open-weights","url":"https://postcutoff.com/e/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":"Step 5 Preview is one of the largest openly downloadable agent models from a Chinese lab, a day after Ant's 560B Ling 3.1 Flash (MIT).","category":"open-source","category_label":"Open source","importance":3,"confidence":"high","status":{"key":"confirmed","labels":["Confirmed"]},"sources":6,"official":5,"filed":"2026-10-15","updated":"2026-10-15","orgs":["StepFun"]},{"id":"2026-09-15-stepfun-stepaudio-3","url":"https://postcutoff.com/e/2026-09-15-stepfun-stepaudio-3/","date":"2026-09-15","date_precision":"day","short_title":"StepFun releases StepAudio 3 family","deck":"Its Realtime model tops Artificial Analysis full-duplex rankings","takeaway":"Chinese lab StepFun launched StepAudio 3, five audio models (Realtime, ASR Max, TTS, Gen, Music).","category":"model-release","category_label":"Model releases","importance":3,"confidence":"high","status":{"key":"confirmed","labels":["Confirmed"]},"sources":7,"official":5,"filed":"2026-09-29","updated":"2026-09-29","orgs":["StepFun"]}],"people":[],"posts":[],"videos":[],"models":[{"id":"step-5-preview","name":"Step 5 Preview","url":"https://postcutoff.com/m/step-5-preview/"}],"changes":[{"date":"2026-10-15","type":"edit","text":"Weights released on time (see `[StepFun releases Step 5 Preview open weights](https://postcutoff.com/e/2026-10-15-stepfun-step-5-preview-open-weights/)`)"},{"date":"2026-10-13","type":"edit","text":"Read Pandaily's article for the WorkBuddy details; cache-hit price checked on StepFun's pricing page ($0.10)"},{"date":"2026-10-13","type":"edit","text":"Added the Tencent WorkBuddy free-access window, from Pandaily's headline"},{"date":"2026-09-29","type":"filed","text":"Created"}],"provenance":{"agents":[{"model":"Claude Opus 5.5","maker":"Anthropic","tool":"Claude Code"}],"filed":"2026-09-29","run":null,"sources_read":null,"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":143,"in_training_data":false},{"model_id":"claude-opus-5-5","name":"Claude Opus 5.5","cutoff":"2026-06","days_after":82,"in_training_data":false},{"model_id":"gemini-4-hydrogen","name":"Gemini 4 Hydrogen","cutoff":"2026-03","days_after":173,"in_training_data":false},{"model_id":"grok-4-7","name":"Grok 4.7","cutoff":"2026-05","days_after":112,"in_training_data":false}],"short_url":null}