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[Bugfix] LoRA: extend expert base_layer loading to Qwen3.5 and Step3.x #37114

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Merged
jeejeelee merged 2 commits into from
Apr 21, 2026
Merged

[Bugfix] LoRA: extend expert base_layer loading to Qwen3.5 and Step3.x #37114

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7d1a8d1
[Bugfix] LoRA: extend expert base_layer loading to Qwen3.5 and Step3.x
HollowMan6 Mar 16, 2026
dc755ae
Merge branch 'main' into lora_qwen3.5
HollowMan6 Apr 21, 2026
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7 changes: 5 additions & 2 deletions vllm/model_executor/models/qwen3_5.py
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Original file line number Diff line number Diff line change
Expand Up @@ -403,9 +403,12 @@ def load_weights(self, weights: Iterable[tuple[str, torch.Tensor]]) -> set[str]:
loaded_params: set[str] = set()
expert_params_mapping = self.get_expert_mapping()
is_fused_expert = False
base_layer = (
"base_layer." if any(".base_layer." in name for name in params_dict) else ""
)
fused_expert_params_mapping = [
("experts.w13_weight", "experts.gate_up_proj", 0, "w1"),
("experts.w2_weight", "experts.down_proj", 0, "w2"),
(f"experts.{base_layer}w13_weight", "experts.gate_up_proj", 0, "w1"),
(f"experts.{base_layer}w2_weight", "experts.down_proj", 0, "w2"),
]
num_experts = (
self.config.num_experts if hasattr(self.config, "num_experts") else 0
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7 changes: 5 additions & 2 deletions vllm/model_executor/models/qwen3_5_mtp.py
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Expand Up @@ -198,9 +198,12 @@ def load_weights(self, weights: Iterable[tuple[str, torch.Tensor]]) -> set[str]:
params_dict = dict(self.named_parameters())
loaded_params: set[str] = set()
is_fused_expert = False
base_layer = (
"base_layer." if any(".base_layer." in name for name in params_dict) else ""
)
fused_expert_params_mapping = [
("experts.w13_weight", "experts.gate_up_proj", 0, "w1"),
("experts.w2_weight", "experts.down_proj", 0, "w2"),
(f"experts.{base_layer}w13_weight", "experts.gate_up_proj", 0, "w1"),
(f"experts.{base_layer}w2_weight", "experts.down_proj", 0, "w2"),
]
num_experts = (
self.config.num_experts if hasattr(self.config, "num_experts") else 0
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7 changes: 5 additions & 2 deletions vllm/model_executor/models/qwen3_vl_moe.py
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Expand Up @@ -183,9 +183,12 @@ def load_weights(self, weights: Iterable[tuple[str, torch.Tensor]]) -> set[str]:
loaded_params: set[str] = set()
expert_params_mapping = self.get_expert_mapping()
is_fused_expert = False
base_layer = (
"base_layer." if any(".base_layer." in name for name in params_dict) else ""
)
fused_expert_params_mapping = [
("experts.w13_weight", "experts.gate_up_proj", 0, "w1"),
("experts.w2_weight", "experts.down_proj", 0, "w2"),
(f"experts.{base_layer}w13_weight", "experts.gate_up_proj", 0, "w1"),
(f"experts.{base_layer}w2_weight", "experts.down_proj", 0, "w2"),
]
num_experts = self.config.num_experts
for name, loaded_weight in weights:
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9 changes: 6 additions & 3 deletions vllm/model_executor/models/step3_text.py
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Expand Up @@ -467,11 +467,14 @@ def load_weights(self, weights: Iterable[tuple[str, torch.Tensor]]) -> set[str]:
]
params_dict = dict(self.named_parameters())
loaded_params: set[str] = set()
base_layer = (
"base_layer." if any(".base_layer." in name for name in params_dict) else ""
)

expert_params_mapping = [
(".moe.experts.w13_weight", ".moe.gate_proj.weight", "w1"),
(".moe.experts.w13_weight", ".moe.up_proj.weight", "w3"),
(".moe.experts.w2_weight", ".moe.down_proj.weight", "w2"),
(f".moe.experts.{base_layer}w13_weight", ".moe.gate_proj.weight", "w1"),
(f".moe.experts.{base_layer}w13_weight", ".moe.up_proj.weight", "w3"),
(f".moe.experts.{base_layer}w2_weight", ".moe.down_proj.weight", "w2"),

@jeejeelee jeejeelee Mar 16, 2026

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It looks like these changes are unrelated. If needed, please submit a separate PR. Thank you.

@HollowMan6 HollowMan6 Mar 16, 2026

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Thank you @jeejeelee for letting me know #36976 and #37019! I just removed all the Qwen3.5 LoRA fix in this PR and focus on the changes you mentioned here, those are extensions to #31104, please let me know what you think, thanks!

]

disable_moe_stacked_params = [data[1] for data in expert_params_mapping]
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9 changes: 6 additions & 3 deletions vllm/model_executor/models/step3p5.py
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Original file line number Diff line number Diff line change
Expand Up @@ -641,12 +641,15 @@ def load_weights(self, weights: Iterable[tuple[str, torch.Tensor]]) -> set[str]:

params_dict = dict(self.named_parameters())
loaded_params: set[str] = set()
base_layer = (
"base_layer." if any(".base_layer." in name for name in params_dict) else ""
)

# Old packed 3D format: .moe.gate_proj.weight [num_experts, out, in]
expert_params_mapping = [
(".moe.experts.w13_weight", ".moe.gate_proj.weight", "w1"),
(".moe.experts.w13_weight", ".moe.up_proj.weight", "w3"),
(".moe.experts.w2_weight", ".moe.down_proj.weight", "w2"),
(f".moe.experts.{base_layer}w13_weight", ".moe.gate_proj.weight", "w1"),
(f".moe.experts.{base_layer}w13_weight", ".moe.up_proj.weight", "w3"),
(f".moe.experts.{base_layer}w2_weight", ".moe.down_proj.weight", "w2"),
]

# New per-expert format: .moe.experts.E.gate_proj.weight_packed [out, in]
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11 changes: 7 additions & 4 deletions vllm/model_executor/models/step3p5_mtp.py
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Original file line number Diff line number Diff line change
Expand Up @@ -181,14 +181,17 @@ def load_weights(self, weights: Iterable[tuple[str, torch.Tensor]]) -> set[str]:
("gate_up_proj", "gate_proj", 0),
("gate_up_proj", "up_proj", 1),
]
params_dict = dict(self.named_parameters())
base_layer = (
"base_layer." if any(".base_layer." in name for name in params_dict) else ""
)

expert_params_mapping = [
(".moe.experts.w13_weight", ".moe.gate_proj.weight", "w1"),
(".moe.experts.w13_weight", ".moe.up_proj.weight", "w3"),
(".moe.experts.w2_weight", ".moe.down_proj.weight", "w2"),
(f".moe.experts.{base_layer}w13_weight", ".moe.gate_proj.weight", "w1"),
(f".moe.experts.{base_layer}w13_weight", ".moe.up_proj.weight", "w3"),
(f".moe.experts.{base_layer}w2_weight", ".moe.down_proj.weight", "w2"),
]

params_dict = dict(self.named_parameters())
loaded_params: set[str] = set()
for name, loaded_weight in weights:
if "rotary_emb.inv_freq" in name:
Expand Down
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