DeepSeek V4.1 Flash: 1M Context, 437x Smaller KV Cache

Logosofia no Dia a Dia · Sep 11, 2026 · 25m

DeepSeek V4.1 Flash looks like a point release but behaves like a new base model: a 552B-parameter mixture of experts with 8B active parameters during prefill, a 20-layer causal encoder feeding a 20-layer decoder, and a global KV cache squeezed to 890 bytes per token. That last number is what makes a million-token context economically real. But bigger windows don't fix the problem anyone actually feels — the model losing the middle of its own input. We walk through the "lost in the middle" literature, the U-shaped attention bias that starves the center of a long prompt, attention sinks that…