Fix kimi k2 function calling format (#9606)

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

@@ -835,15 +835,23 @@ class OpenAIServingChat(OpenAIServingBase):
                 finish_reason["matched"] = None
             try:
                 text, call_info_list = parser.parse_non_stream(text)
-                tool_calls = [
+                tool_calls = []
+                for call_info in call_info_list:
+                    # For Kimi-K2, align tool_call_id with the model format: functions.{name}:{index}
+                    if tool_call_parser == "kimi_k2" and call_info.name is not None:
+                        tool_id = f"functions.{call_info.name}:{call_info.tool_index}"
+                    else:
+                        tool_id = f"call_{uuid.uuid4().hex[:24]}"
+
+                    tool_calls.append(
                         ToolCall(
-                        id=f"call_{uuid.uuid4().hex[:24]}",
+                            id=tool_id,
+                            index=getattr(call_info, "tool_index", None),
                             function=FunctionResponse(
                                 name=call_info.name, arguments=call_info.parameters
                             ),
                         )
-                    for call_info in call_info_list
-                ]
+                    )
                 return tool_calls, text, finish_reason
             except Exception as e:
                 logger.error(f"Tool call parsing error: {e}")
@@ -954,6 +962,10 @@ class OpenAIServingChat(OpenAIServingBase):
             # Tool call ID should be generated only once per tool call
             if call_item.name:
                 # First chunk: include ID and function name
+                if self.tokenizer_manager.server_args.tool_call_parser == "kimi_k2":
+                    # Align with Kimi-K2 format: functions.{name}:{index}
+                    tool_call_id = f"functions.{call_item.name}:{call_item.tool_index}"
+                else:
                     tool_call_id = f"call_{uuid.uuid4().hex[:24]}"
                 function_name = call_item.name
             else:

test/srt/openai_server/basic/test_serving_chat.py

@@ -6,6 +6,8 @@ or
     python -m unittest discover -s tests -p "test_*unit.py" -v
 """
 
+import asyncio
+import json
 import unittest
 import uuid
 from typing import Optional
@@ -325,6 +327,100 @@ class ServingChatTestCase(unittest.TestCase):
             result, "Should return None when parser has no tool call data"
         )
 
+    # ------------- kimi_k2 tool_call_id formatting -------------
+    def test_kimi_k2_non_streaming_tool_call_id_format(self):
+        """Ensure non-streaming tool_call.id matches functions.{name}:{index} for kimi_k2 parser."""
+
+        # Force kimi_k2 parser
+        self.tm.server_args.tool_call_parser = "kimi_k2"
+
+        # Mock FunctionCallParser.parse_non_stream to return one tool call
+        with patch(
+            "sglang.srt.entrypoints.openai.serving_chat.FunctionCallParser"
+        ) as ParserMock:
+            parser_instance = ParserMock.return_value
+
+            # Build a mock ToolCallItem-like object
+            call_info = Mock()
+            call_info.name = "get_weather"
+            call_info.parameters = '{"city":"Paris"}'
+            call_info.tool_index = 0
+
+            parser_instance.has_tool_call.return_value = True
+            parser_instance.parse_non_stream.return_value = ("", [call_info])
+
+            finish_reason = {"type": "stop", "matched": None}
+            tools = [
+                {"type": "function", "function": {"name": "get_weather"}},
+            ]
+
+            tool_calls, remaining_text, _ = self.chat._process_tool_calls(
+                text="<|tool_calls_section_begin|>...",
+                tools=tools,
+                tool_call_parser="kimi_k2",
+                finish_reason=finish_reason,
+            )
+
+            self.assertIsNotNone(tool_calls)
+            self.assertEqual(len(tool_calls), 1)
+            self.assertEqual(tool_calls[0].id, "functions.get_weather:0")
+            self.assertEqual(tool_calls[0].function.name, "get_weather")
+
+    def test_kimi_k2_streaming_tool_call_id_format(self):
+        """Ensure streaming first chunk tool_call.id matches functions.{name}:{index} for kimi_k2 parser."""
+
+        # Force kimi_k2 parser
+        self.tm.server_args.tool_call_parser = "kimi_k2"
+
+        # Prepare request with tools
+        req = ChatCompletionRequest(
+            model="x",
+            messages=[{"role": "user", "content": "Hi?"}],
+            tools=[{"type": "function", "function": {"name": "get_weather"}}],
+            stream=True,
+        )
+
+        # Patch FunctionCallParser used inside _process_tool_call_stream
+        with patch(
+            "sglang.srt.entrypoints.openai.serving_chat.FunctionCallParser"
+        ) as ParserMock:
+            parser_instance = ParserMock.return_value
+
+            # First call returns one ToolCallItem-like chunk (with name)
+            first_chunk_call = Mock()
+            first_chunk_call.tool_index = 0
+            first_chunk_call.name = "get_weather"
+            first_chunk_call.parameters = ""
+            parser_instance.parse_stream_chunk.side_effect = [
+                ("", [first_chunk_call]),
+                ("", []),
+            ]
+
+            async def collect_first_tool_chunk():
+                gen = self.chat._process_tool_call_stream(
+                    index=0,
+                    delta="irrelevant",
+                    parser_dict={},
+                    content={"meta_info": {"id": "chatcmpl-test"}},
+                    request=req,
+                    has_tool_calls={},
+                )
+                # Get first yielded SSE line
+                line = None
+                async for emitted in gen:
+                    line = emitted
+                    break
+                return line
+
+            loop = asyncio.get_event_loop()
+            line = loop.run_until_complete(collect_first_tool_chunk())
+            self.assertIsNotNone(line)
+            self.assertTrue(line.startswith("data: "))
+
+            payload = json.loads(line[len("data: ") :])
+            tool_calls = payload["choices"][0]["delta"]["tool_calls"]
+            self.assertEqual(tool_calls[0]["id"], "functions.get_weather:0")
+
 
 if __name__ == "__main__":
     unittest.main(verbosity=2)