Fix issue #4604: '[Bug]: Disable function calling for DeepSeek'

openhands/core/config/llm_config.py

@@ -90,7 +90,11 @@ class LLMConfig:
         """
         Post-initialization hook to assign OpenRouter-related variables to environment variables.
         This ensures that these values are accessible to litellm at runtime.
+        Also sets model-specific capabilities.
         """
+        # Set function calling support for DeepSeek models
+        if 'deepseek' in self.model.lower():
+            self.supports_function_calling = True
 
         # Assign OpenRouter-specific variables to environment variables
         if self.openrouter_site_url:
@@ -136,3 +140,4 @@ class LLMConfig:
             draft_editor_config = LLMConfig(**llm_config_dict['draft_editor'])
             args['draft_editor'] = draft_editor_config
         return cls(**args)
+

openhands/core/message.py

@@ -80,17 +80,32 @@ class Message(BaseModel):
             elif isinstance(item, ImageContent) and self.vision_enabled:
                 content.extend(d)
 
+        # For DeepSeek, we need to ensure content is a string when using tool calls
+        if len(content) == 1 and isinstance(content[0], dict) and 'text' in content[0]:
+            content = content[0]['text']
+
         ret: dict = {'content': content, 'role': self.role}
 
         if role_tool_with_prompt_caching:
             ret['cache_control'] = {'type': 'ephemeral'}
 
+        # Handle tool calls for DeepSeek compatibility
         if self.tool_call_id is not None:
-            assert (
-                self.name is not None
-            ), 'name is required when tool_call_id is not None'
+            assert self.name is not None, 'name is required when tool_call_id is not None'
             ret['tool_call_id'] = self.tool_call_id
             ret['name'] = self.name
         if self.tool_calls:
-            ret['tool_calls'] = self.tool_calls
+            # Ensure tool_calls is properly serialized for DeepSeek
+            ret['tool_calls'] = [
+                {
+                    'id': tc.id,
+                    'type': tc.type,
+                    'function': {
+                        'name': tc.function.name,
+                        'arguments': tc.function.arguments
+                    }
+                } for tc in self.tool_calls
+            ]
         return ret
+
+

openhands/llm/llm.py

@@ -159,11 +159,12 @@ class LLM(RetryMixin, DebugMixin):
                     self.config.max_output_tokens = self.model_info['max_tokens']
 
         self.config.supports_function_calling = (
-            self.model_info is not None
-            and self.model_info.get('supports_function_calling', False)
+            (self.model_info is not None and self.model_info.get('supports_function_calling', False))
+            or 'deepseek' in self.config.model.lower()  # DeepSeek models support function calling
         )
 
         self._completion = partial(
+
             litellm_completion,
             model=self.config.model,
             api_key=self.config.api_key,
@@ -473,3 +474,9 @@ class LLM(RetryMixin, DebugMixin):
 
         # let pydantic handle the serialization
         return [message.model_dump() for message in messages]
+
+
+
+
+
+

tests/unit/test_deepseek_tool_calling.py

@@ -0,0 +1,31 @@
+import pytest
+from openhands.core.config import LLMConfig
+from openhands.core.message import Message, TextContent
+from openhands.llm.llm import LLM
+
+def test_deepseek_tool_calling_message_serialization():
+    # Create a message with tool calls
+    message = Message(
+        role="assistant",
+        content=[TextContent(text="Let me help you with that.")],
+        tool_calls=[{
+            "id": "call_123",
+            "type": "function",
+            "function": {
+                "name": "test_function",
+                "arguments": '{"arg1": "value1"}'
+            }
+        }]
+    )
+    
+    # Verify serialization
+    serialized = message.model_dump()
+    assert "tool_calls" in serialized
+    assert isinstance(serialized["content"], str)
+    assert serialized["tool_calls"][0]["id"] == "call_123"
+    assert serialized["tool_calls"][0]["function"]["name"] == "test_function"
+
+def test_deepseek_model_supports_function_calling():
+    config = LLMConfig(model="deepseek-chat")
+    llm = LLM(config)
+    assert llm.config.supports_function_calling is True