bugfix: Fix XGrammar backend to use model's EOS tokens for constrained generation (#8422)

python/sglang/srt/constrained/base_grammar_backend.py

@@ -168,7 +168,10 @@ class BaseGrammarBackend:
 
 
 def create_grammar_backend(
-    server_args: ServerArgs, tokenizer, vocab_size: int
+    server_args: ServerArgs,
+    tokenizer,
+    vocab_size: int,
+    eos_token_ids: Optional[set] = None,
 ) -> Optional[BaseGrammarBackend]:
     if server_args.grammar_backend == "outlines":
         from sglang.srt.constrained.outlines_backend import OutlinesGrammarBackend
@@ -180,7 +183,12 @@ def create_grammar_backend(
     elif server_args.grammar_backend == "xgrammar":
         from sglang.srt.constrained.xgrammar_backend import XGrammarGrammarBackend
 
-        grammar_backend = XGrammarGrammarBackend(tokenizer, vocab_size=vocab_size)
+        # Convert Set[int] to List[int] if needed
+        eos_list = list(eos_token_ids) if eos_token_ids else None
+
+        grammar_backend = XGrammarGrammarBackend(
+            tokenizer, vocab_size=vocab_size, model_eos_token_ids=eos_list
+        )
     elif server_args.grammar_backend == "llguidance":
         from sglang.srt.constrained.llguidance_backend import GuidanceBackend