If you want to understand why 2026's frontier LLMs look the way they do — why one ships Multi-head Latent Attention, another interleaves linear and full attention, a third leans on sliding windows — stop looking at benchmark scores and look at the KV cache. Almost every architectural decision at the frontier this year is, at heart, a fight with the memory that autoregressive decoding leaves behind. This is a practitioner's map of that fight: what the KV cache actually costs, the lineage of te...