[Bugfix][Kimi K3] Enable deferred MoE finalization before weight loading

tests/models/kimi_k3/test_latent_moe_tail.py

@@ -1,6 +1,8 @@
 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
+from types import SimpleNamespace
+
 import pytest
 import ray
 import torch
@@ -13,8 +15,13 @@
     multi_process_parallel,
 )
 from vllm.distributed import get_tp_group
+from vllm.model_executor.layers.fused_moe.experts.trtllm_mxfp4_moe import (
+    TrtLlmMxfp4ExpertsMonolithic,
+)
 from vllm.model_executor.layers.fused_moe.moe_output import UnfinalizedMoEOutput
+from vllm.model_executor.layers.fused_moe.runner.moe_runner import MoERunner
 from vllm.model_executor.warmup.cutedsl_warmup import cutedsl_warmup
+from vllm.models.kimi_k3.nvidia import latent_moe_runner
 from vllm.models.kimi_k3.nvidia.ops.latent_moe_tail import KimiK3LatentMoETailOp
 from vllm.platforms import current_platform
 
@@ -24,6 +31,78 @@
 TOP_K = 8
 
 
+def test_deferred_finalize_enabled_before_moe_kernel_setup(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    class FakeMoEConfig:
+        tp_size = 8
+        dp_size = 1
+        ep_size = 1
+        pcp_size = 1
+        is_sequence_parallel = False
+        hidden_dim = LATENT_SIZE
+        hidden_dim_unpadded = LATENT_SIZE
+        experts_per_token = 16
+        defer_moe_finalize = False
+        defer_moe_finalize_max_num_tokens = -1
+
+        @property
+        def use_deferred_moe_finalize(self) -> bool:
+            return self.defer_moe_finalize
+
+    moe_config = FakeMoEConfig()
+    quant_method = SimpleNamespace(
+        experts_cls=TrtLlmMxfp4ExpertsMonolithic,
+        moe_kernel=None,
+    )
+    norm_weight = torch.empty(LATENT_SIZE, dtype=torch.bfloat16)
+    transform = SimpleNamespace(
+        norm=SimpleNamespace(weight=norm_weight, variance_epsilon=EPS),
+        up_proj=SimpleNamespace(
+            weight=SimpleNamespace(shape=(HIDDEN_SIZE, LATENT_SIZE))
+        ),
+    )
+
+    def fake_runner_init(runner, *args, **kwargs) -> None:
+        runner.moe_config = moe_config
+        runner.routed_experts = SimpleNamespace(quant_method=quant_method)
+        runner._shared_experts = object()
+        runner.routed_output_transform = transform
+
+    initialized_with: dict[str, object] = {}
+    tail_op = SimpleNamespace(contract=SimpleNamespace(max_num_tokens=128))
+
+    def fake_tail_initialize(**kwargs):
+        initialized_with.update(kwargs)
+        return tail_op
+
+    monkeypatch.setattr(MoERunner, "__init__", fake_runner_init)
+    monkeypatch.setattr(latent_moe_runner.torch.cuda, "Event", lambda: object())
+    monkeypatch.setattr(
+        latent_moe_runner,
+        "current_platform",
+        SimpleNamespace(
+            is_cuda=lambda: True,
+            is_device_capability_family=lambda capability: capability == 100,
+        ),
+    )
+    monkeypatch.setattr(
+        latent_moe_runner,
+        "get_current_vllm_config",
+        lambda: SimpleNamespace(
+            parallel_config=SimpleNamespace(use_ubatching=False),
+            model_config=SimpleNamespace(enable_sleep_mode=False),
+        ),
+    )
+    monkeypatch.setattr(KimiK3LatentMoETailOp, "initialize", fake_tail_initialize)
+
+    latent_moe_runner.LatentMoERunner()
+
+    assert moe_config.defer_moe_finalize
+    assert moe_config.defer_moe_finalize_max_num_tokens == 128
+    assert initialized_with["experts_per_token"] == 16
+
+
 def _make_deferred_routed_output(
     num_tokens: int,
     device: torch.device,

vllm/models/kimi_k3/nvidia/latent_moe_runner.py

@@ -113,16 +113,12 @@ def __init__(
             )
 
             experts_cls = getattr(self._quant_method, "experts_cls", None)
-            moe_kernel = self._quant_method.moe_kernel
+            # The kernel instance is built after weight loading, while the tail
+            # must register its CuTeDSL warmup units during runner construction.
             self.moe_config.defer_moe_finalize = (
-                (
-                    experts_cls is TrtLlmMxfp4ExpertsMonolithic
-                    or experts_cls is TrtLlmNvFp4ExpertsMonolithic
-                )
-                and self.moe_config.hidden_dim == self.moe_config.hidden_dim_unpadded
-                and moe_kernel is not None
-                and moe_kernel.supports_deferred_moe_finalize()
-            )
+                experts_cls is TrtLlmMxfp4ExpertsMonolithic
+                or experts_cls is TrtLlmNvFp4ExpertsMonolithic
+            ) and self.moe_config.hidden_dim == self.moe_config.hidden_dim_unpadded
             from vllm.models.kimi_k3.nvidia.ops.latent_moe_tail import (
                 KimiK3LatentMoETailOp,
             )
@@ -145,6 +141,12 @@ def __init__(
                 if self.moe_config.use_deferred_moe_finalize
                 else -1
             )
+            if self.moe_config.use_deferred_moe_finalize:
+                logger.info_once(
+                    "K3 latent-MoE tail fusion with deferred top-k finalization "
+                    "is enabled for up to %d tokens.",
+                    op.contract.max_num_tokens,
+                )
         else:
             self.moe_config.defer_moe_finalize = False
             self.moe_config.defer_moe_finalize_max_num_tokens = -1