[v1] support liger_kernel (#10493)

examples/v1/train_full/train_full_liger_kernel.yaml

@@ -0,0 +1,28 @@
+model: Qwen/Qwen3-0.6B
+model_class: llm
+
+template: qwen3_nothink
+
+kernel_config:
+  name: liger_kernel
+  include_kernels: auto # choice: null/true/false/auto/kernel_id1,kernel_id2,kernel_id3, default is null
+
+quant_config: null
+
+dist_config:
+  name: fsdp2
+  dcp_path: null # /mnt/f/pretrain_models/Qwen3-0.6B-dcp
+
+### data
+train_dataset: data/v1_sft_demo.yaml
+
+### training
+output_dir: outputs/test_fsdp2
+micro_batch_size: 1
+cutoff_len: 2048
+learning_rate: 1.0e-4
+max_steps: 10
+
+### sample
+sample_backend: hf
+max_new_tokens: 128

src/llamafactory/v1/core/model_engine.py

@@ -188,9 +188,12 @@ class ModelEngine:
         if self.args.kernel_config is not None:
             from ..plugins.model_plugins.kernels.interface import KernelPlugin
 
-            model = KernelPlugin(self.args.kernel_config.name)(
-                model, include_kernels=self.args.kernel_config.get("include_kernels")
-            )
+            kernel_config = self.args.kernel_config
+            kernel_kwargs: dict = {"model": model, "include_kernels": kernel_config.get("include_kernels")}
+            if kernel_config.name == "liger_kernel":
+                # Fused linear CE omits logits; SFT stage needs logits for loss_weights.
+                kernel_kwargs["require_logits"] = self.is_train
+            model = KernelPlugin(kernel_config.name)(**kernel_kwargs)
 
         return model
 

src/llamafactory/v1/plugins/model_plugins/kernels/base.py

@@ -34,7 +34,7 @@ class BaseKernel(ABC):
     """
 
     _kernel_id: Any = ""  # kernel ID, any hashable value to identify a kernel implementation
-    _device: DeviceType = DeviceType.CPU  # "cuda", "npu", "cpu", etc.
+    _device: list[DeviceType] = [DeviceType.CPU]  # "cuda", "npu", "cpu", etc.
 
     @classmethod
     def get_kernel_id(cls) -> str:
@@ -42,8 +42,8 @@ class BaseKernel(ABC):
         return cls._kernel_id
 
     @classmethod
-    def get_device(cls) -> str:
-        """Returns the device type associated with the kernel (e.g., "cuda", "npu", "cpu")."""
+    def get_device(cls) -> list[DeviceType]:
+        """Returns the device type list associated with the kernel (e.g., ["cuda", "npu", "cpu"])."""
         return cls._device
 
     @classmethod
@@ -58,7 +58,7 @@ class BaseKernel(ABC):
             it should raise an error instead of silently switching.
             Kernels can override this method to implement custom dependency checks.
         """
-        if cls._device != get_current_accelerator().type:
+        if get_current_accelerator().type not in cls._device:
             return False
         return True
 

src/llamafactory/v1/plugins/model_plugins/kernels/interface.py

@@ -138,3 +138,48 @@ def apply_default_kernels(model: HFModel, include_kernels: str = None) -> HFMode
         apply_kernel(kernel, model=model)
 
     return model
+
+
+@KernelPlugin("liger_kernel").register()
+def apply_liger_kernels(
+    model: HFModel,
+    include_kernels: str = None,
+    require_logits: bool = False,
+) -> HFModel:
+    """Applies Liger kernel to the model.
+
+    Args:
+        model (HFModel): The model instance to apply kernels to.
+        include_kernels (str, optional): If ``"auto"`` or ``True``, apply Liger with
+                                         library defaults. If a comma-separated list (e.g.
+                                         ``rope,rms_norm``), enable only those ops; names match
+                                         ``apply_liger_kernel_to_*`` kwargs: ``rope``, ``rms_norm``,
+                                         ``swiglu``, ``cross_entropy``, ``fused_linear_cross_entropy``.
+                                         If ``None`` or ``False``, do nothing. Defaults to ``None``.
+        require_logits (bool, optional): When true, disables ``fused_linear_cross_entropy`` in favor
+                                         of non-fused CE so the forward pass returns ``logits``. Needed
+                                         for trainers that compute weighted loss from logits (e.g. v1
+                                         SFT with ``loss_weights``). Defaults to ``False`` (fused CE
+                                         when supported). The v1 ``run_sft`` entrypoint sets
+                                         ``require_logits`` to true for ``liger_kernel`` when the key
+                                         is omitted so SFT weighted loss keeps working.
+
+    Returns:
+        HFModel: The model with Liger kernel applied.
+    """
+    if not include_kernels:
+        return model
+    if include_kernels == "auto" or include_kernels is True:
+        use_kernels = "auto"
+    else:
+        use_kernels = [k.strip() for k in include_kernels.split(",") if k.strip()]
+        if not use_kernels:
+            return model
+
+    try:
+        from .liger_kernel_ops import LigerKernel
+    except ImportError as e:
+        logger.warning_rank0(f"[Kernel] Failed to import liger_kernel ops, skip. Error: {e}")
+        return model
+
+    return LigerKernel.apply(use_kernels=use_kernels, model=model, require_logits=require_logits)

src/llamafactory/v1/plugins/model_plugins/kernels/liger_kernel_ops.py

@@ -0,0 +1,148 @@
+# Copyright 2025 the LlamaFactory team.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""The definition of Liger Kernel.
+
+Init Phase:
+1. Define LigerKernel class.
+2. Register Liger kernel.
+
+"""
+
+import inspect
+
+from ....accelerator.helper import DeviceType, get_current_accelerator
+from ....utils.logging import get_logger
+from ....utils.types import HFModel
+from .base import BaseKernel
+
+
+logger = get_logger(__name__)
+
+_LIGER_FN_BY_MODEL_TYPE: dict[str, str] = {
+    "qwen3": "apply_liger_kernel_to_qwen3",
+    "qwen3_moe": "apply_liger_kernel_to_qwen3_moe",
+    "qwen3_next": "apply_liger_kernel_to_qwen3_next",
+    "qwen3_5": "apply_liger_kernel_to_qwen3_5",
+    "qwen3_5_text": "apply_liger_kernel_to_qwen3_5_text",
+    "qwen3_5_moe": "apply_liger_kernel_to_qwen3_5_moe",
+    "qwen3_5_moe_text": "apply_liger_kernel_to_qwen3_5_moe_text",
+}
+
+
+class LigerKernel(BaseKernel):
+    """Liger Kernel for optimized model training."""
+
+    _device = [DeviceType.CUDA, DeviceType.NPU]
+
+    @classmethod
+    def check_deps(cls) -> bool:
+        """Checks if the required dependencies for the kernel are available."""
+        try:
+            import liger_kernel  # noqa: F401
+
+            return super().check_deps()
+        except ImportError:
+            logger.warning_rank0(
+                "Liger kernel is not installed, the kernel_config liger_kernel will be ignored. Please install it from https://github.com/linkedin/Liger-Kernel."
+            )
+            return False
+
+    @classmethod
+    def apply(cls, **kwargs) -> "HFModel":
+        """Applies the Liger kernel to the model.
+
+        Args:
+            **kwargs: Must include ``model``. Optional ``use_kernels`` is a list of Liger op
+                names to enable exclusively, or the string ``"auto"`` to use each
+                ``apply_liger_kernel_to_*`` function's signature defaults (same as calling
+                upstream with only ``model``). Optional ``require_logits`` forces non-fused
+                cross entropy when supported.
+
+        Returns:
+            HFModel: The model with Liger kernel applied.
+
+        Raises:
+            ValueError: If the model is not provided.
+            RuntimeError: If dependencies are not met.
+        """
+        model = kwargs.get("model")
+        use_kernels = kwargs.get("use_kernels", None)
+        if model is None:
+            raise ValueError(f"HFModel instance is required for {cls.__name__}.")
+
+        if not cls.check_deps():
+            raise RuntimeError(
+                f"current device is not supported by liger_kernel. Current device is {get_current_accelerator().type}, supported devices are {cls.get_device()}"
+            )
+
+        require_logits = kwargs.get("require_logits", False)
+
+        model_type = getattr(model.config, "model_type", None)
+
+        if model_type not in _LIGER_FN_BY_MODEL_TYPE:
+            logger.warning_rank0("Current model does not support liger kernel.")
+            return model
+
+        import liger_kernel.transformers as liger_transformers
+
+        apply_liger_kernel = getattr(liger_transformers, _LIGER_FN_BY_MODEL_TYPE[model_type])
+
+        sig = inspect.signature(apply_liger_kernel).parameters
+        togglable = [name for name in sig if name != "model"]
+
+        def _normalize_op_name(raw: str) -> str:
+            key = raw.strip().lower().replace("-", "_")
+            aliases = {
+                "rmsnorm": "rms_norm",
+                "flce": "fused_linear_cross_entropy",
+                "lce": "fused_linear_cross_entropy",
+                "fused_ce": "fused_linear_cross_entropy",
+            }
+            return aliases.get(key, key)
+
+        if use_kernels is not None and len(use_kernels) == 0:
+            return model
+
+        if use_kernels != "auto":
+            selected = {_normalize_op_name(k) for k in use_kernels}
+            ops = selected - set(togglable)
+            if ops:
+                raise ValueError(
+                    f"Unknown Liger op(s) {sorted(ops)} for model_type={model_type}. Valid: {sorted(togglable)}"
+                )
+            if "cross_entropy" in selected and "fused_linear_cross_entropy" in selected:
+                raise ValueError("cross_entropy and fused_linear_cross_entropy cannot both be enabled.")
+            call_kwargs = {name: (name in selected) for name in togglable}
+            call_kwargs["model"] = model
+        else:
+            # Mirror ``liger_kernel`` signature defaults so patches match upstream defaults
+            # and logging reflects enabled ops (omitted kwargs only live in the callee).
+            call_kwargs = {"model": model}
+            for name in togglable:
+                param = sig[name]
+                if param.default is not inspect.Parameter.empty:
+                    call_kwargs[name] = param.default
+
+        if require_logits and "fused_linear_cross_entropy" in sig:
+            logger.warning_rank0("Current training stage does not support chunked cross entropy.")
+            call_kwargs["fused_linear_cross_entropy"] = False
+            call_kwargs["cross_entropy"] = True
+
+        apply_liger_kernel(**call_kwargs)
+
+        applied = sorted(name for name, on in call_kwargs.items() if name != "model" and on)
+        logger.info_rank0(f"These Liger ops are applied to the model: {applied}")
+
+        return model

src/llamafactory/v1/plugins/model_plugins/kernels/registry.py

@@ -58,7 +58,7 @@ class Registry:
         device = kernel_cls.get_device()
 
         # The device type of the current accelerator does not match the device type required by the kernel, skip registration
-        if device != get_current_accelerator().type:
+        if get_current_accelerator().type not in device:
             return
 
         if not kernel_id: