Remote empty text content for tool calls & support kimi-k2-thinking (#1093)

Co-authored-by: openhands <[email protected]>
Co-authored-by: enyst <[email protected]>
Co-authored-by: Xingyao Wang <[email protected]>

Author: 4 people

.github/workflows/integration-runner.yml

@@ -67,6 +67,10 @@ jobs:
                       run-suffix: deepseek_run
                       llm-config:
                           model: litellm_proxy/deepseek/deepseek-chat
+                    - name: Kimi K2 Thinking
+                      run-suffix: kimi_k2_run
+                      llm-config:
+                          model: litellm_proxy/moonshot/kimi-k2-thinking
         steps:
             - name: Checkout repository
               uses: actions/checkout@v5

openhands-sdk/openhands/sdk/llm/message.py

@@ -269,6 +269,7 @@ def to_chat_dict(self) -> dict[str, Any]:
         # Assistant function_call(s)
         if self.role == "assistant" and self.tool_calls:
             message_dict["tool_calls"] = [tc.to_chat_dict() for tc in self.tool_calls]
+            self._remove_content_if_empty(message_dict)
 
         # Tool result (observation) threading
         if self.role == "tool" and self.tool_call_id is not None:
@@ -331,6 +332,52 @@ def _list_serializer(self) -> dict[str, Any]:
         # tool call keys are added in to_chat_dict to centralize behavior
         return message_dict
 
+    def _remove_content_if_empty(self, message_dict: dict[str, Any]) -> None:
+        """Remove empty text content entries from assistant tool-call messages.
+
+        Mutates the provided message_dict in-place:
+        - If content is a string of only whitespace, drop the 'content' key
+        - If content is a list, remove any text items with empty text; if the list
+          becomes empty, drop the 'content' key
+        """
+        if "content" not in message_dict:
+            return
+
+        content = message_dict["content"]
+
+        if isinstance(content, str):
+            if content.strip() == "":
+                message_dict.pop("content", None)
+            return
+
+        if isinstance(content, list):
+            normalized: list[Any] = []
+            for item in content:
+                if not isinstance(item, dict):
+                    normalized.append(item)
+                    continue
+
+                if item.get("type") == "text":
+                    text_value = item.get("text", "")
+                    if isinstance(text_value, str):
+                        if text_value.strip() == "":
+                            continue
+                    else:
+                        raise ValueError(
+                            f"Text content item has non-string text value: "
+                            f"{text_value!r}"
+                        )
+
+                normalized.append(item)
+
+            if normalized:
+                message_dict["content"] = normalized
+            else:
+                message_dict.pop("content", None)
+            return
+
+        # Any other content shape is left as-is
+
     def to_responses_value(self, *, vision_enabled: bool) -> str | list[dict[str, Any]]:
         """Return serialized form.
 

tests/sdk/llm/test_message.py

@@ -142,6 +142,45 @@ def test_message_with_tool_calls():
     assert result["tool_calls"][0]["function"]["arguments"] == '{"arg": "value"}'
 
 
+def test_message_tool_calls_drop_empty_string_content():
+    """Assistant tool calls with no text should not include empty content strings."""
+    from openhands.sdk.llm.message import Message, MessageToolCall
+
+    tool_call = MessageToolCall(
+        id="call_empty",
+        name="test_function",
+        arguments="{}",
+        origin="completion",
+    )
+
+    message = Message(role="assistant", content=[], tool_calls=[tool_call])
+
+    result = message.to_chat_dict()
+    assert "content" not in result
+
+
+def test_message_tool_calls_strip_blank_list_content():
+    """List-serialized tool call messages should drop blank text content blocks."""
+    from openhands.sdk.llm.message import Message, MessageToolCall, TextContent
+
+    tool_call = MessageToolCall(
+        id="call_blank_list",
+        name="test_function",
+        arguments="{}",
+        origin="completion",
+    )
+
+    message = Message(
+        role="assistant",
+        content=[TextContent(text="")],
+        tool_calls=[tool_call],
+        function_calling_enabled=True,
+    )
+
+    result = message.to_chat_dict()
+    assert "content" not in result
+
+
 def test_message_from_llm_chat_message_function_role_error():
     """Test Message.from_llm_chat_message with function role raises error."""
     from litellm.types.utils import Message as LiteLLMMessage