DeepSeek V4's fully compressed layers might bottleneck long-context performance

bookwormengr · x · 2026-07-31

The author notes that despite recent upgrades, DeepSeek V4-Flash underperforms in long-context reasoning compared to MiniMax-2.7 and Kimi K3, with even V4 Pro falling short.

The speculation is that DeepSeek V4's lack of a single full attention layer is the culprit. Its architecture consists of SWA, CSA, and HCA layers—all of which compress along the sequence dimension and are lossy by definition. This yields an extremely low KV cache size but sacrifices long-context performance.

In contrast, Kimi K3 retains 24 MLA full attention layers (25%), offering a winning compromise between cache size and long-context capabilities.

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