DeepSeek V4 Paper Reveals 90% KV Cache Reduction at 1M Tokens via Compressed Sparse + Heavily Compressed Attention

r/LocalLLaMA·medium signal

The DeepSeek V4 technical paper details how Compressed Sparse Attention (CSA) + Heavily Compressed Attention (HCA) cut KV cache from 83.9 GiB to 9.62 GiB at 1M-token context — a 10x reduction vs V3.2. V4-Flash achieves 7% of V3.2's KV cache with 10% of single-token FLOPs. 119↑ on r/LocalLLaMA with 47 comments dissecting the architecture. Simon Willison and LMSYS published day-zero analyses.