From 7a07a9c93d328fddece47df7d938cf505e914fe7 Mon Sep 17 00:00:00 2001
From: drslark <slarksblood@qq.com>
Date: Fri, 6 Mar 2026 14:57:18 +0800
Subject: [PATCH] [main][feature] Support quarot for eagle3

Signed-off-by: drslark <slarksblood@qq.com>
---
 vllm/model_executor/models/llama_eagle3.py | 33 +++++++++++++++++++
 vllm/model_executor/models/utils.py        | 37 ++++++++++++++++++++++
 2 files changed, 70 insertions(+)

diff --git a/vllm/model_executor/models/llama_eagle3.py b/vllm/model_executor/models/llama_eagle3.py
index 5f66716d5454..ff784ff5828e 100644
--- a/vllm/model_executor/models/llama_eagle3.py
+++ b/vllm/model_executor/models/llama_eagle3.py
@@ -30,6 +30,9 @@
     get_draft_quant_config,
     maybe_prefix,
     process_eagle_weight,
+    get_rotation_path,
+    get_rotataion_matrix,
+    compute_rotataion_matrix3,
 )
 
 logger = init_logger(__name__)
@@ -266,6 +269,10 @@ class Eagle3LlamaForCausalLM(LlamaForCausalLM):
     def __init__(self, *, vllm_config: VllmConfig, prefix: str = ""):
         nn.Module.__init__(self)
         self.config = vllm_config.speculative_config.draft_model_config.hf_config
+
+        self.target_model_config = self.vllm_config.speculative_config.target_model_config
+        self.target_quant_config = self.vllm_config.quant_config
+
         # Ensure draft_vocab_size is set
         # default to the base vocab size when absent
         if getattr(self.config, "draft_vocab_size", None) is None:
@@ -360,6 +367,19 @@ def combine_hidden_states(
         return self.model.fc(hidden_states)
 
     def load_weights(self, weights: Iterable[tuple[str, torch.Tensor]]):
+        # TODO maybe extract a function
+        rotation_path = get_rotation_path(self.target_model_config.model, self.target_quant_config)
+
+        use_quarot = rotation_path is not None
+
+        if use_quarot:
+            Q = get_rotataion_matrix(rotation_path)
+            Q3 = compute_rotataion_matrix3(Q)
+            if isinstance(self.config.dtype, str):
+                embed_dtype = getattr(torch, self.config.dtype)
+            else:
+                embed_dtype = self.config.dtype
+
         model_weights = {}
         includes_draft_id_mapping = False
         includes_embed_tokens = False
@@ -384,11 +404,24 @@ def load_weights(self, weights: Iterable[tuple[str, torch.Tensor]]):
                 continue
             elif "lm_head" not in name:
                 name = "model." + name
+            if "fc." in name and use_quarot:
+                # anti-rotate fc
+                dtype = loaded_weight.dtype
+                loaded_weight = loaded_weight @ Q3.to(dtype)
             if "embed_tokens" in name:
                 includes_embed_tokens = True
             model_weights[name] = loaded_weight
             process_eagle_weight(self, name)
 
+        # process embedding if drafter does not have embedding
+        if use_quarot and not includes_embed_tokens:
+            name = "model.embed_tokens.weight"
+            loaded_weight = get_embedding_tensor(target_model_path).to(dtype) @ Q.T.to(dtype)
+            model_weights[name] = loaded_weight
+
+            includes_embed_tokens = True
+            process_eagle_weight(self, name)
+
         if not includes_mask_hidden and self.use_parallel_drafting:
             raise ValueError(
                 "mask_hidden not found in weights but "
diff --git a/vllm/model_executor/models/utils.py b/vllm/model_executor/models/utils.py
index abc953b7f980..1ffef8f93b2b 100644
--- a/vllm/model_executor/models/utils.py
+++ b/vllm/model_executor/models/utils.py
@@ -875,3 +875,40 @@ def get_layer_index(feature_layer_index: int, num_hidden_layers: int) -> int:
     if feature_layer_index < 0:
         return num_hidden_layers + feature_layer_index + 1
     return feature_layer_index
+
+
+def get_rotation_path(target_model_path, quant_config):
+    """
+    Gets the path of the rotation matrix, returns None if the target model is not a quarot model.
+    """
+    try:
+        rotation_relative_path = quant_config.quant_description["optional"]["quarot"]["rotation_map"][
+            "global_rotation"
+        ]
+    except KeyError:
+        return None
+
+    return Path(target_model_path) / rotation_relative_path
+
+
+def get_rotataion_matrix(rotation_path):
+    """
+    Anti-rotate maxtrix.
+    """
+    try:
+        safetensor_data = load_file(rotation_path)
+        Q = safetensor_data["global_rotation"]
+
+        return Q
+    except Exception as e:
+        logger.error(
+            f"Failed to load rotation weight from '{rotation_path}'. "
+            "If you want to use quarot model with eagle3, take a check."
+        )
+        raise e
+
+def compute_rotataion_matrix3(Q):
+    """
+    Anti-rotate matrix for 3 layers of hidden_states.
+    """
+    return torch.block_diag(Q, Q, Q)