CONFIRMEDDate confidence: CONFIRMEDStated as firmHow firmly the source words the date: confirmed, scheduled, estimated, delayed or unverified.Show all CONFIRMED pins87% CONFIDENCEOverall confidence: 87%How well the pin's source and references back up its dates.Weighted average of how firmly 6 references, the source included, support the pin's start and end times; a reference counts half as much for every 180 days older than the newestShow all pins at 75% confidence or better
AIBase's[6] 2 February 2026 report calls it StepFun's[1][3] "latest open-source foundation model" with code on GitHub and weights on Hugging Face[2], and the GitHub repository's first commit is dated 2 February; OpenRouter listed it from 29 January and the Hugging Face repo was created on 1 February UTC, so the public launch day is 2 February.StepFun open-sources Step 3.5 Flash, a 196B-parameter sparse mixture-of-experts with 11B active parameters, a 256K context and up to 350 tokens per second, scoring 74.4% on SWE-bench Verified under Apache 2.0.
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