vllm-project/vllm · error · ValueError

Unknown quantization method: {self.quantization}. Must be on

Error message

Unknown quantization method: {self.quantization}. Must be one of {supported_quantization}.

What it means

Error "Unknown quantization method: {self.quantization}. Must be one of {supported_quantization}." thrown in vllm-project/vllm.

Source

Thrown at vllm/config/model.py:1282

                    quant_method = quantization_override
                    self.quantization = quantization_override
                    break

            quant_method = quant_method if quant_method != "" else None
            # Verify quantization configurations.
            if self.quantization is None:
                self.quantization = quant_method
            elif self.quantization != quant_method:
                raise ValueError(
                    "Quantization method specified in the model config "
                    f"({quant_method}) does not match the quantization "
                    f"method specified in the `quantization` argument "
                    f"({self.quantization})."
                )

        if self.quantization is not None:
            if self.quantization not in supported_quantization:
                raise ValueError(
                    f"Unknown quantization method: {self.quantization}. Must "
                    f"be one of {supported_quantization}."
                )
            current_platform.verify_quantization(self.quantization)

        if self.quantization in me_quant.DEPRECATED_QUANTIZATION_METHODS:
            if self.allow_deprecated_quantization:
                logger.warning(
                    "The quantization method %s is deprecated "
                    "and will be removed in future versions of vLLM.",
                    self.quantization,
                )
            else:
                raise ValueError(
                    "The quantization method %s is deprecated "
                    "and will be removed in future versions of vLLM. To bypass, "
                    "set `--allow-deprecated-quantization`.",
                    self.quantization,

View on GitHub (pinned to c794754062)

Solutions

1. Use one of the supported quantization methods listed in the error.
2. Check the model's quantization config and the vLLM supported quantization list.

When it happens

Trigger: Raised at vllm/config/model.py:1282 when validation fails: Unknown quantization method. Typically triggered by an incompatible or incomplete vLLM configuration, an unsupported platform/backend combination, or a runtime resource/dependency that is missing.

Common situations: Commonly encountered at vllm/config/model.py:1282 during vLLM startup/config validation or runtime setup when: (1) conflicting CLI flags or config fields are combined, (2) the current platform (CUDA/ROCm/CPU/XPU) or installed optional packages do not support the requested feature, or (3) a required value is absent or out of range. Resolve by correcting the configuration as described in the message, or by selecting a supported alternative.

AI-assisted analysis of vllm-project/vllm@c794754062 (2026-08-14). Data as JSON: /api/errors/06e722cecf319a32. Report an issue: GitHub.