Fix kv_cache_scheme: DSV4 sparse attention requires FP8 KV cache

#4

kv_cache_scheme is currently null, but DeepSeek-V4's sparse attention architecture requires FP8 KV cache.
vLLM hard-asserts kv_cache_dtype.startswith("fp8") in vllm/models/deepseek_v4/attention.py - the model fails to load without it.

The sgl-project FP8 variant (sgl-project/DeepSeek-V4-Flash-FP8) works because its quant_method: "fp8" triggers implicit FP8 KV cache inference. This checkpoint uses quant_method: "compressed-tensors" which does not, so the scheme must be declared explicitly.

Verified on an 8xH100 cluster — the model crashes at worker startup without this fix.

Red Hat AI org

@nathans-redhat-com thanks for the suggestion, I’ll update the other models as well. Could you please add quant arg dynamic=True to avoid using static scales?

kylesayrs changed pull request status to closed

@nathans-redhat-com I did not observe the behavior that you specified, I still needed to pass --kv_cache_dtype=fp8. The change has been reverted

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