A visual guide to Google's Gemma 4 architecture by Maarten Grootendorst received 212 upvotes on r/LocalLLaMA, shared by Hugging Face's Omar Sanseviero. The guide breaks down Gemma 4's hybrid design where only 10 of 60 layers use global attention while the rest use linear/sliding window attention — the architectural decision behind both its efficiency advantage and the KV cache bugs the community just fixed.