[Fix] NGRAMWorker.update_weights_from_tensor — delegate to target worker (#24344)

python/sglang/srt/speculative/ngram_worker.py

@@ -83,6 +83,15 @@ class NGRAMWorker:
     def clear_cache_pool(self):
         self.ngram_corpus.reset()
 
+    def update_weights_from_tensor(self, recv_req):
+        # NGRAM has no draft weights of its own — the n-gram corpus is a CPU
+        # lookup structure built from request token streams — and its
+        # `model_runner` is shared with the target worker. The scheduler
+        # mixin dispatches via `self.draft_worker or self.tp_worker`, so
+        # without this method any caller of `update_weights_from_tensor`
+        # under `--speculative-algorithm NGRAM` raises AttributeError.
+        return self.target_worker.update_weights_from_tensor(recv_req)
+
     def add_external_corpus(self, corpus_id: str, token_chunks: list[list[int]]) -> int:
         return self.ngram_corpus.load_external_corpus_named(corpus_id, token_chunks)