Optimize detokenization without HF decode kwargs (#25309)

python/sglang/srt/managers/detokenizer_manager.py

@@ -44,6 +44,7 @@ from sglang.srt.utils import (
 )
 from sglang.srt.utils.hf_transformers_utils import get_tokenizer
 from sglang.srt.utils.network import get_zmq_socket
+from sglang.srt.utils.patch_tokenizer import decode_without_hf_kwargs
 from sglang.srt.utils.watchdog import Watchdog
 from sglang.utils import (
     TypeBasedDispatcher,
@@ -190,6 +191,12 @@ class DetokenizerManager(MultiHttpWorkerDetokenizerMixin):
     ) -> List[str]:
         """Batch decode with grouping by (skip_special_tokens, spaces_between_special_tokens)."""
 
+        if not getattr(self.tokenizer, "is_fast", False):
+            return [
+                decode_without_hf_kwargs(self.tokenizer, ids, skip)
+                for ids, skip in zip(ids_list, skip_list)
+            ]
+
         # fast path
         first_skip, first_space = skip_list[0], space_list[0]
         if all(

python/sglang/srt/utils/patch_tokenizer.py

@@ -29,6 +29,15 @@ def _is_kimi_tiktoken_tokenizer(tokenizer):
     return class_name == "TikTokenTokenizer" and "tokenization_kimi" in module_name
 
 
+def decode_without_hf_kwargs(tokenizer, token_ids, skip_special_tokens):
+    if skip_special_tokens:
+        special_ids = getattr(tokenizer, "all_special_ids_set", None)
+        if special_ids is None:
+            special_ids = set(tokenizer.all_special_ids)
+        token_ids = [tid for tid in token_ids if tid not in special_ids]
+    return tokenizer.decode(token_ids)
+
+
 class _SpecialTokensCachePatcher:
     _PATCHED_FLAG = "_sglang_special_tokens_patched"
     _CACHED_TOKENS_ATTR = "_sglang_cached_special_tokens"