add support for nvidia/gpt-oss-120b-Eagle3 (#9739)

python/sglang/srt/models/llama_eagle3.py

@@ -185,9 +185,13 @@ class LlamaForCausalLMEagle3(LlamaForCausalLM):
         )
         # Llama 3.2 1B Instruct set tie_word_embeddings to True
         # Llama 3.1 8B Instruct set tie_word_embeddings to False
+        self.load_lm_head_from_target = False
         if self.config.tie_word_embeddings:
             self.lm_head = self.model.embed_tokens
         else:
+            if config.draft_vocab_size is None:
+                self.load_lm_head_from_target = True
+                config.draft_vocab_size = config.vocab_size
             self.lm_head = ParallelLMHead(
                 config.draft_vocab_size,
                 config.hidden_size,

python/sglang/srt/speculative/eagle_worker.py

@@ -137,7 +137,14 @@ class EAGLEWorker(TpModelWorker):
         embed, head = self.target_worker.model_runner.model.get_embed_and_head()
 
         if self.speculative_algorithm.is_eagle3():
-            # EAGLE3 models don't share lm_head
+            # most cases EAGLE3 models don't share lm_head
+            # but some models (e.g. nvidia/gpt-oss-120b-Eagle3) shares
+            if (
+                hasattr(self.draft_model_runner.model, "load_lm_head_from_target")
+                and self.draft_model_runner.model.load_lm_head_from_target
+            ):
+                self.draft_model_runner.model.set_embed_and_head(embed, head)
+            else:
                 self.draft_model_runner.model.set_embed(embed)
 
             # grab hot token ids