DeepSeek V4.1 'causal encoder-decoder' label debated: likely a YOCO-style KV-reuse design
donglixp · x · 2026-09-10
Developer aHapBean pushes back on the 'Causal Encoder-Decoder' framing of DeepSeek V4.1, arguing it overstates the architectural departure:
- V4.1 is likely still a decoder-only LLM; a clearer description is a YOCO-style KV-reuse design (You Only Cache Once)
- The 'encoder' is just the lower half of a jointly trained causal Transformer stack — early layers of decoder-only LLMs already function as encoders building contextual representations
- Upper layers share global KV derived from midpoint representations, letting most prompt tokens skip upper-layer computation during prefill — a real efficiency win
- The whole stack is trained end to end; 'encoder-decoder' wrongly suggests two separate networks
Related event: DeepSeek V4.1 Flash Confirmed to Center on YOCO Architecture(7 posts)→
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