fix(py): fix the issue of no response in say_hi_stream flow (#4003)

Co-authored-by: Mengqin Shen <mengqin@google.com>

Author: MengqinShen

py/plugins/anthropic/src/genkit/plugins/anthropic/models.py

@@ -75,10 +75,10 @@ async def generate(self, request: GenerateRequest, ctx: ActionRunContext | None
 
         if streaming:
             response = await self._generate_streaming(params, ctx)
-            content = []
         else:
             response = await self.client.messages.create(**params)
-            content = self._to_genkit_content(response.content)
+
+        content = self._to_genkit_content(response.content)
 
         response_message = Message(role=Role.MODEL, content=content)
         basic_usage = get_basic_usage_stats(input_=request.messages, response=response_message)
@@ -155,7 +155,7 @@ async def _generate_streaming(self, params: dict[str, Any], ctx: ActionRunContex
                         GenerateResponseChunk(
                             role=Role.MODEL,
                             index=0,
-                            content=[TextPart(text=chunk.delta.text)],
+                            content=[Part(root=TextPart(text=chunk.delta.text))],
                         )
                     )
             return await stream.get_final_message()
@@ -223,15 +223,17 @@ def _to_genkit_content(self, content_blocks: list) -> list[Part]:
         parts = []
         for block in content_blocks:
             if block.type == 'text':
-                parts.append(TextPart(text=block.text))
+                parts.append(Part(root=TextPart(text=block.text)))
             elif block.type == 'tool_use':
                 parts.append(
-                    ToolRequestPart(
-                        tool_request={
-                            'ref': block.id,
-                            'name': block.name,
-                            'input': block.input,
-                        }
+                    Part(
+                        root=ToolRequestPart(
+                            tool_request={
+                                'ref': block.id,
+                                'name': block.name,
+                                'input': block.input,
+                            }
+                        )
                     )
                 )
         return parts

py/plugins/anthropic/tests/test_models.py

@@ -180,9 +180,10 @@ def test_to_anthropic_messages():
 class MockStreamManager:
     """Mock stream manager for testing streaming."""
 
-    def __init__(self, chunks):
+    def __init__(self, chunks, final_content=None):
         self.chunks = chunks
         self.final_message = MagicMock()
+        self.final_message.content = final_content if final_content else []
         self.final_message.usage = MagicMock(input_tokens=10, output_tokens=20)
         self.final_message.stop_reason = 'end_turn'
 
@@ -217,7 +218,8 @@ async def test_streaming_generation():
         MagicMock(type='content_block_delta', delta=MagicMock(text='!')),
     ]
 
-    mock_stream = MockStreamManager(chunks)
+    final_content = [MagicMock(type='text', text='Hello world!')]
+    mock_stream = MockStreamManager(chunks, final_content=final_content)
     mock_client.messages.stream.return_value = mock_stream
 
     model = AnthropicModel(model_name='claude-sonnet-4', client=mock_client)
@@ -248,3 +250,10 @@ def send_chunk(chunk: GenerateResponseChunk):
 
     assert response.usage.input_tokens == 10
     assert response.usage.output_tokens == 20
+
+    # Verify final response content is populated
+    assert len(response.message.content) == 1
+    final_part = response.message.content[0]
+    assert isinstance(final_part, Part)
+    assert isinstance(final_part.root, TextPart)
+    assert final_part.root.text == 'Hello world!'