[Fix] Require JSON booleans for response_format json_schema.strict (#34777)

Co-authored-by: James Liu <jamesl@modal.com>

python/sglang/srt/entrypoints/openai/protocol.py

@@ -53,6 +53,7 @@ from pydantic import (
     BaseModel,
     ConfigDict,
     Field,
+    StrictBool,
     field_serializer,
     field_validator,
     model_serializer,
@@ -219,7 +220,10 @@ class JsonSchemaResponseFormat(BaseModel):
     description: Optional[str] = None
     # use alias to workaround pydantic conflict
     schema_: Optional[Dict[str, object]] = Field(alias="schema", default=None)
-    strict: Optional[bool] = None
+    # The OpenAI wire contract accepts JSON booleans only; StrictBool rejects
+    # the values lax pydantic would coerce ("yes", "on", 0, 1, ...), matching
+    # OpenAI's 422 behavior. Omitted (None) keeps its meaning.
+    strict: Optional[StrictBool] = None
 
 
 class ResponseFormat(BaseModel):