ThursdAI — the weekly AI news podcast hosted by Alex Volkov — has covered 6 StepFun releases since Feb 2025, most recently StepAudio 2.5 on Apr 23, 2026. Highlights include Step-Video-T2V, Step-Video-TI2V, Step1X-3D, Step 3.5 Flash. 5 of them shipped with open weights. Every entry below has primary-source links and the episode segment where we covered it live.
StepAudio 2.5 TTS adds natural-language control of emotion and delivery
StepFun released StepAudio 2.5, a text-to-speech model that lets you steer emotion and delivery with natural-language instructions. It was covered in the show's Voice & Audio segment as the week's notable speech release.
StepFun open-sources Step 3.5 Flash Base with its training stack
StepFun released Step 3.5 Flash Base and Midtrain checkpoints, an unusually open release that includes training artifacts and the SteptronOSS training stack alongside the weights. The panel praised the Apache-2 orientation and called the continuation-pretraining flexibility a major practical unlock for builders.
StepFun Step 3.5 Flash: frontier reasoning claims at 11B active params
StepFun released Step 3.5 Flash, a 196B sparse MoE model with only 11B active parameters, claiming frontier-level reasoning while generating at 100-350 tokens per second. It continues the trend of sparse Chinese MoE models delivering high speed at low active parameter counts.
StepFun's Step1X-3D: open two-stage framework for textured 3D assets
StepFun released Step1X-3D, an open two-stage framework for high-fidelity, controllable generation of textured 3D assets: it first synthesizes watertight geometry, then generates view-consistent textures. Trained on 2M curated meshes, the release also includes a curated dataset of 800K assets and a Hugging Face demo.
StepFun releases Step-Video-TI2V image-to-video model
Chinese lab StepFun dropped Step-Video-TI2V, an open text/image-to-video generation model. Weights are on Hugging Face with code on GitHub, adding another open-weights option to the fast-moving video generation space.
StepFun open-sources Step-Video-T2V, a SOTA 30B text-to-video model
StepFun released Step-Video-T2V (plus a T2V Turbo variant), a 30 billion parameter state-of-the-art text-to-video model under an MIT license. Results impressed especially on text integration, such as rendering 'We will open source' on a scroll as a character unfurls it, marking one of the strongest open-source video drops of the week.
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