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fix: Force float16 dtype for GGUF models to fix incorrect output #30090

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kitaekatt wants to merge 3 commits into from
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fix: Force float16 dtype for GGUF models to fix incorrect output #30090

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aa7ff75
fix: Default GGUF to float16 while preserving bfloat16 option
kitaekatt Dec 9, 2025
20d5288
fix(gguf): Disable bfloat16 on Blackwell (SM 120+) via device capabil…
kitaekatt Dec 9, 2025
9848dd9
fix(gguf): Remove dtype auto-override, rely on quantization layer
kitaekatt Dec 9, 2025
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9 changes: 9 additions & 0 deletions vllm/model_executor/layers/quantization/gguf.py
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@
)
from vllm.model_executor.models.utils import WeightsMapper
from vllm.model_executor.utils import set_weight_attrs
from vllm.platforms import current_platform
from vllm.utils.torch_utils import direct_register_custom_op

logger = init_logger(__name__)
Expand All @@ -52,6 +53,14 @@ def get_name(self) -> QuantizationMethods:
return "gguf"

def get_supported_act_dtypes(self) -> list[torch.dtype]:
# GGUF dequantization kernels use half precision (fp16) internally.
# bfloat16 has precision issues on SM 120+ devices (Blackwell).
if current_platform.has_device_capability(120):
logger.warning_once(
"GGUF has precision issues with bfloat16 on SM 120+ devices. "
"bfloat16 is unavailable for Blackwell devices."
)
return [torch.half, torch.float32]
return [torch.half, torch.bfloat16, torch.float32]

@classmethod
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