diff --git a/python/sglang/srt/entrypoints/openai/json_schema_utils.py b/python/sglang/srt/entrypoints/openai/json_schema_utils.py
index 4e8039233b68..759624ac3f2b 100644
--- a/python/sglang/srt/entrypoints/openai/json_schema_utils.py
+++ b/python/sglang/srt/entrypoints/openai/json_schema_utils.py
@@ -39,6 +39,9 @@ def _enforce_no_additional_properties(schema: Dict[str, Any]) -> None:
 def normalize_json_schema(schema: Dict[str, Any], strict: bool) -> Dict[str, Any]:
     """Return a normalized copy of the schema with stricter defaults when requested."""
     normalized = copy.deepcopy(schema)
+    properties = normalized.get("properties")
+    if isinstance(properties, dict) and "strict" in properties:
+        properties.pop("strict", None)
     if strict:
         _enforce_no_additional_properties(normalized)
     return normalized
diff --git a/python/sglang/srt/entrypoints/openai/protocol.py b/python/sglang/srt/entrypoints/openai/protocol.py
index d9025ef8a12e..db2228d63b1d 100644
--- a/python/sglang/srt/entrypoints/openai/protocol.py
+++ b/python/sglang/srt/entrypoints/openai/protocol.py
@@ -545,8 +545,25 @@ class ChatCompletionRequest(BaseModel):
     @model_validator(mode="before")
     @classmethod
     def set_tool_choice_default(cls, values):
-        if values.get("tool_choice") is None:
-            if values.get("tools") is None:
+        model_name = str(values.get("model") or "").lower()
+        tools = values.get("tools")
+        tool_choice = values.get("tool_choice")
+
+        def _is_auto(choice):
+            return isinstance(choice, str) and choice.lower() == "auto"
+
+        is_kimi_thinking = model_name == "moonshotai/kimi-k2-thinking"
+
+        if (
+            is_kimi_thinking
+            and tools is not None
+            and (tool_choice is None or _is_auto(tool_choice))
+        ):
+            values["tool_choice"] = "required"
+            return values
+
+        if tool_choice is None:
+            if tools is None:
                 values["tool_choice"] = "none"
             else:
                 values["tool_choice"] = "auto"
diff --git a/python/sglang/srt/function_call/function_call_parser.py b/python/sglang/srt/function_call/function_call_parser.py
index 0755448e97ad..c93f83fdf1ea 100644
--- a/python/sglang/srt/function_call/function_call_parser.py
+++ b/python/sglang/srt/function_call/function_call_parser.py
@@ -189,7 +189,7 @@ def get_structure_constraint(
         if self.detector.supports_structural_tag() and tool_choice == "auto":
             structural_tag = self.get_structure_tag()
             return ("structural_tag", structural_tag)
-        elif isinstance(self.detector, LongCatDetector):
+        elif isinstance(self.detector, (LongCatDetector, KimiK2Detector)):
             ebnf = self.get_ebnf(tool_choice)
             return ("ebnf", ebnf) if ebnf is not None else None
         elif tool_choice == "required" or isinstance(tool_choice, ToolChoice):
diff --git a/test/srt/openai_server/basic/test_protocol.py b/test/srt/openai_server/basic/test_protocol.py
index fbf1e3971dc0..602c25fbdd8a 100644
--- a/test/srt/openai_server/basic/test_protocol.py
+++ b/test/srt/openai_server/basic/test_protocol.py
@@ -190,6 +190,53 @@ def test_chat_completion_tool_choice_validation(self):
         )
         self.assertEqual(request2.tool_choice, "auto")
 
+    def test_chat_completion_tool_choice_for_kimi_k2(self):
+        """Ensure Kimi K2 Thinking forces tool_choice to required when tools are present."""
+        messages = [{"role": "user", "content": "Hello"}]
+        tools = [
+            {
+                "type": "function",
+                "function": {
+                    "name": "test_func",
+                    "description": "Test function",
+                },
+            }
+        ]
+
+        request_default = ChatCompletionRequest(
+            model="moonshotai/Kimi-K2-Thinking",
+            messages=messages,
+            tools=tools,
+        )
+        self.assertEqual(request_default.tool_choice, "required")
+
+        request_auto = ChatCompletionRequest(
+            model="moonshotai/Kimi-K2-Thinking",
+            messages=messages,
+            tools=tools,
+            tool_choice="auto",
+        )
+        self.assertEqual(request_auto.tool_choice, "required")
+
+        request_function = ChatCompletionRequest(
+            model="moonshotai/Kimi-K2-Thinking",
+            messages=messages,
+            tools=tools,
+            tool_choice={
+                "type": "function",
+                "function": {"name": "test_func"},
+            },
+        )
+        self.assertEqual(request_function.tool_choice.function.name, "test_func")
+
+        request_none = ChatCompletionRequest(
+            model="moonshotai/Kimi-K2-Thinking",
+            messages=messages,
+            tools=tools,
+            tool_choice="none",
+        )
+        self.assertEqual(request_none.tool_choice, "none")
+
     def test_chat_completion_sglang_extensions(self):
         """Test chat completion with SGLang extensions"""
         messages = [{"role": "user", "content": "Hello"}]