[Bugfix] Fix qwen-moe packed_modules_mapping (#26634)

Signed-off-by: Jee Jee Li <pandaleefree@gmail.com>

vllm/model_executor/models/interfaces.py

@@ -325,7 +325,7 @@ class SupportsLoRA(Protocol):
     # are empty by default.
     embedding_modules: ClassVar[dict[str, str]] = {}
     embedding_padding_modules: ClassVar[list[str]] = []
-    packed_modules_mapping: ClassVar[dict[str, list[str]]] = {}
+    packed_modules_mapping: dict[str, list[str]] = {}
 
 
 # We can't use runtime_checkable with ClassVar for issubclass checks

vllm/model_executor/models/qwen2_moe.py

@@ -534,11 +534,7 @@ class Qwen2MoeForCausalLM(nn.Module, SupportsPP, SupportsLoRA):
             "q_proj",
             "k_proj",
             "v_proj",
-        ],
-        "gate_up_proj": [
-            "gate_proj",
-            "up_proj",
-        ],
+        ]
     }
 
     def __init__(self, *, vllm_config: VllmConfig, prefix: str = ""):
@@ -547,6 +543,18 @@ class Qwen2MoeForCausalLM(nn.Module, SupportsPP, SupportsLoRA):
         quant_config = vllm_config.quant_config
         self.config = config
         self.quant_config = quant_config
+        # Only perform the following mapping when Qwen2MoeMLP exists
+        if (
+            getattr(config, "mlp_only_layers", [])
+            or config.shared_expert_intermediate_size > 0
+        ):
+            self.packed_modules_mapping["gate_up_proj"] = (
+                [
+                    "gate_proj",
+                    "up_proj",
+                ],
+            )
+
         self.model = Qwen2MoeModel(
             vllm_config=vllm_config, prefix=maybe_prefix(prefix, "model")
         )

vllm/model_executor/models/qwen3_moe.py

@@ -634,11 +634,7 @@ class Qwen3MoeForCausalLM(
             "q_proj",
             "k_proj",
             "v_proj",
-        ],
-        "gate_up_proj": [
-            "gate_proj",
-            "up_proj",
-        ],
+        ]
     }
 
     fall_back_to_pt_during_load = False
@@ -649,6 +645,14 @@ class Qwen3MoeForCausalLM(
         quant_config = vllm_config.quant_config
         self.config = config
         self.quant_config = quant_config
+        # Only perform the following mapping when Qwen3MoeMLP exists
+        if getattr(config, "mlp_only_layers", []):
+            self.packed_modules_mapping["gate_up_proj"] = (
+                [
+                    "gate_proj",
+                    "up_proj",
+                ],
+            )
         self.model = Qwen3MoeModel(
             vllm_config=vllm_config, prefix=maybe_prefix(prefix, "model")
         )