Dev builds 3D viewer for live SAE feature activations inside Gemma, runs locally on DGX Spark
leland_mcinnes · x · 2026-09-20
Inspired by recent fly-brain simulations and interpretability work, developer blakefullerton built a 3D viewer for watching SAE features activate inside a language model as it generates text.
In the demo, Gemma completing "the golden gate bridge is located in the city of" can be paused at "Francisco" to inspect features labeled "San Francisco, Oakland, Bay Area" and "City names." Everything runs locally on a DGX Spark with a 2x speedup, and the author shared the implementation in a thread — a practical path to inspecting model internals at runtime.
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