[Speculators][Speculative Decoding] Fix gpt-oss eagle3 accuracy issue (#25406)

Signed-off-by: jiahanc <173873397+jiahanc@users.noreply.github.com>

tests/v1/spec_decode/test_eagle.py

@@ -534,6 +534,8 @@ def test_propose(method, attn_backend, num_speculative_tokens, monkeypatch):
     proposer.runner.attn_groups.append([mock.MagicMock()])
     proposer.runner.attn_groups[0][0].get_metadata_builder.return_value = \
         attn_metadata_builder
+    proposer._get_attention_metadata_builder = mock.MagicMock(
+        return_value=attn_metadata_builder)
 
     result = proposer.propose(target_token_ids=target_token_ids,
                               target_positions=target_positions,
@@ -660,6 +662,8 @@ def test_propose_tree(spec_token_tree):
     proposer.runner.attn_groups.append([mock.MagicMock()])
     proposer.runner.attn_groups[0][0].get_metadata_builder.return_value = \
         attn_metadata_builder
+    proposer._get_attention_metadata_builder = mock.MagicMock(
+        return_value=attn_metadata_builder)
 
     # Setup inputs for the proposer.
     target_token_ids = torch.randint(0,

vllm/config/model.py

@@ -1003,6 +1003,7 @@ class ModelConfig:
                     self.quantization = quantization_override
                     break
 
+            quant_method = quant_method if quant_method != "" else None
             # Verify quantization configurations.
             if self.quantization is None:
                 self.quantization = quant_method

vllm/model_executor/models/llama_eagle.py

@@ -134,6 +134,11 @@ class EagleLlamaForCausalLM(LlamaForCausalLM):
         nn.Module.__init__(self)
         self.config = vllm_config. \
             speculative_config.draft_model_config.hf_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:
+            base_vocab_size = getattr(self.config, "vocab_size", None)
+            self.config.draft_vocab_size = base_vocab_size
         target_layer_num = vllm_config.model_config.get_num_layers(
             vllm_config.parallel_config)
         self.model = LlamaModel(vllm_config=vllm_config,

vllm/model_executor/models/llama_eagle3.py

@@ -203,6 +203,11 @@ class Eagle3LlamaForCausalLM(LlamaForCausalLM):
         nn.Module.__init__(self)
         self.config = vllm_config. \
             speculative_config.draft_model_config.hf_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:
+            base_vocab_size = getattr(self.config, "vocab_size", None)
+            self.config.draft_vocab_size = base_vocab_size
         target_layer_num = vllm_config.model_config.get_num_layers(
             vllm_config.parallel_config)
 

vllm/v1/spec_decode/eagle.py

@@ -9,6 +9,7 @@ import numpy as np
 import torch
 import torch.nn as nn
 
+from vllm.attention.backends.abstract import AttentionMetadataBuilder
 from vllm.attention.layer import Attention
 from vllm.config import (CompilationLevel, VllmConfig,
                          get_layers_from_vllm_config)
@@ -77,6 +78,8 @@ class EagleProposer:
         self.is_multimodal_model = vllm_config.model_config \
             .is_multimodal_model
 
+        self.attn_metadata_builder: Optional[AttentionMetadataBuilder] = None
+
         self.use_cuda_graph = (self.vllm_config.compilation_config.level
                                == CompilationLevel.PIECEWISE and
                                not self.vllm_config.model_config.enforce_eager)
@@ -117,7 +120,7 @@ class EagleProposer:
             with_numpy=True)
 
         # Determine allowed attention backends once during initialization.
-        self.allowed_attn_types: tuple[type[EagleAttentionMetadata], ...]
+        self.allowed_attn_types: tuple[type, ...]
         if current_platform.is_rocm():
             rocm_types = [TritonAttentionMetadata, FlashAttentionMetadata]
             # vllm.v1.attention.backends.rocm_aiter_fa is an optional backend
@@ -190,10 +193,12 @@ class EagleProposer:
 
         assert self.runner is not None
 
-        # FIXME: need to consider multiple kv_cache_groups
-        attn_metadata_builder = \
-            self.runner.attn_groups[0][0].get_metadata_builder()
-        attn_metadata = attn_metadata_builder.build_for_drafting(
+        # Select the correct attention metadata builders for EAGLE layers.
+        # Get the attention metadata builders once and reuse for later.
+        builder = (self._get_attention_metadata_builder()
+                   if self.attn_metadata_builder is None else
+                   self.attn_metadata_builder)
+        attn_metadata = builder.build_for_drafting(
             common_attn_metadata=common_attn_metadata, draft_index=0)
 
         # At this moment, we assume all eagle layers belong to the same KV
@@ -327,10 +332,8 @@ class EagleProposer:
                 exceeds_max_model_len, PADDING_SLOT_ID)
 
             # Rebuild attention metadata
-            attn_metadata_builder = \
-                self.runner.attn_groups[0][0].get_metadata_builder()
-            attn_metadata = attn_metadata_builder\
-                .build_for_drafting(common_attn_metadata=common_attn_metadata,
+            attn_metadata = builder.build_for_drafting(
+                common_attn_metadata=common_attn_metadata,
                 draft_index=token_index + 1)
             for layer_name in self.attn_layer_names:
                 per_layer_attn_metadata[layer_name] = attn_metadata
@@ -851,10 +854,24 @@ class EagleProposer:
         # share lm_head with the target model if needed
         # some model definition do not define lm_head explicitly
         # and reuse embed_tokens for lm_head, e.g., CohereForCausalLM
-        if self.vllm_config.speculative_config.method != "eagle3" and \
-                hasattr(target_language_model, "lm_head"):
-            logger.info("Loading EAGLE LM head weights from the target model.")
+        if self.vllm_config.speculative_config.method != "eagle3":
+            if hasattr(target_language_model, "lm_head"):
+                logger.info(
+                    "Loading EAGLE LM head weights from the target model.")
+                self.model.lm_head = target_language_model.lm_head
+        else:
+            if (hasattr(self.model, "lm_head")
+                    and hasattr(target_language_model, "lm_head")
+                    and self.model.lm_head.weight.shape
+                    == target_language_model.lm_head.weight.shape):
+                logger.info("Assuming the EAGLE head shares the same lm_head"
+                            " with the target model.")
+                del self.model.lm_head
                 self.model.lm_head = target_language_model.lm_head
+            else:
+                logger.info(
+                    "The EAGLE head's lm_head will be loaded separately"
+                    " from the target model.")
 
     @torch.inference_mode()
     def dummy_run(
@@ -877,6 +894,31 @@ class EagleProposer:
                 inputs_embeds=inputs_embeds,
             )
 
+    def _get_attention_metadata_builder(
+            self) -> list[AttentionMetadataBuilder]:
+        """Find and return the attention metadata builders for EAGLE layers.
+        
+        Returns:
+            The metadata builders for EAGLE layers.
+            
+        Raises:
+            AssertionError: If no metadata builders are found for EAGLE layers.
+        """
+        builder = None
+        chosen_layer = self.attn_layer_names[0]
+
+        for kv_cache_group in self.runner.attn_groups:
+            for attn_group in kv_cache_group:
+                if chosen_layer in attn_group.layer_names:
+                    builder = attn_group.get_metadata_builder()
+                    break
+            if builder is not None:
+                break
+
+        assert builder is not None, (
+            "Failed to find attention metadata builder for EAGLE layers.")
+        return builder
+
     def validate_same_kv_cache_group(self,
                                      kv_cache_config: KVCacheConfig) -> None:
         """

vllm/v1/worker/gpu_model_runner.py

@@ -1177,8 +1177,13 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
                 encoder_seq_lens=encoder_seq_lens,
             )
 
-            if self.speculative_config and \
-                spec_decode_common_attn_metadata is None:
+            if (self.speculative_config
+                    and spec_decode_common_attn_metadata is None):
+                if isinstance(self.drafter, EagleProposer):
+                    if (self.drafter.attn_layer_names[0]
+                            in kv_cache_group_spec.layer_names):
+                        spec_decode_common_attn_metadata = common_attn_metadata
+                else:
                     spec_decode_common_attn_metadata = common_attn_metadata
 
             for attn_group in self.attn_groups[kv_cache_group_id]: