diff --git a/packages/apps/src/microsoft_teams/apps/http_stream.py b/packages/apps/src/microsoft_teams/apps/http_stream.py
index cf52b321..f33588d3 100644
--- a/packages/apps/src/microsoft_teams/apps/http_stream.py
+++ b/packages/apps/src/microsoft_teams/apps/http_stream.py
@@ -399,6 +399,9 @@ async def _send(self, to_send: Union[TypingActivityInput, MessageActivityInput])
             else:
                 res = await self._client.conversations.create_activity(self._ref.conversation.id, to_send)
 
+            if to_send.id:
+                res = res.model_copy(update={"id": to_send.id})
+
             return SentActivity.merge(to_send, res)
         except HTTPStatusError as e:
             # Various error codes are used for streaming.
diff --git a/packages/apps/tests/test_http_stream.py b/packages/apps/tests/test_http_stream.py
index 892f6ad4..dd8a93d3 100644
--- a/packages/apps/tests/test_http_stream.py
+++ b/packages/apps/tests/test_http_stream.py
@@ -50,6 +50,14 @@ def mock_api_client(self):
         async def mock_send(conversation_id, activity):
             client.send_call_count += 1
             client.sent_activities.append(activity)
+
+            stream_entities = [
+                entity for entity in activity.entities or [] if entity.type == "streaminfo" and entity.stream_id
+            ]
+            stream_id = next((entity.stream_id for entity in stream_entities), None)
+            if stream_id:
+                return SentActivity(id="DO_NOT_USE_PLACEHOLDER_ID", activity_params=activity)
+
             return SentActivity(id=f"activity-{client.send_call_count}", activity_params=activity)
 
         client.conversations.create_activity = mock_send
@@ -504,6 +512,45 @@ async def test_close_returns_none_when_canceled(self, mock_api_client, conversat
         result = await stream.close()
         assert result is None
 
+    @pytest.mark.asyncio
+    async def test_close_returns_stream_id_when_final_response_has_placeholder(
+        self, mock_api_client, conversation_reference, patch_loop_call_later
+    ):
+        """The final streaming response is empty, so close() must retain the first chunk's id."""
+        loop = asyncio.get_running_loop()
+        patcher, scheduled = patch_loop_call_later(loop)
+        close_activities: list[SentActivity] = []
+        close_event = asyncio.Event()
+
+        async def handle_close(activity: SentActivity) -> None:
+            close_activities.append(activity)
+            close_event.set()
+
+        async def mock_create(conversation_id, activity):
+            if any(
+                entity.type == "streaminfo" and entity.stream_type == "final" for entity in (activity.entities or [])
+            ):
+                return SentActivity(id="DO_NOT_USE_PLACEHOLDER_ID", activity_params=activity)
+            return SentActivity(id="stream-1", activity_params=activity)
+
+        mock_api_client.conversations.create_activity = mock_create
+
+        with patcher:
+            stream = HttpStream(mock_api_client, conversation_reference)
+            stream.on_close(handle_close)
+
+            stream.emit("Streamed content")
+            await asyncio.sleep(0)
+            await self._run_scheduled_flushes(scheduled)
+
+            result = await stream.close()
+
+        assert result is not None
+        assert result.id == "stream-1"
+        await asyncio.wait_for(close_event.wait(), timeout=1)
+        assert close_activities == [result]
+        assert close_activities[0].id == "stream-1"
+
     @pytest.mark.asyncio
     async def test_final_activity_last_wins(self, mock_api_client, conversation_reference, patch_loop_call_later):
         """When multiple MessageActivityInputs are emitted, the last one's non-text fields are used."""
@@ -780,6 +827,7 @@ async def test_close_waits_for_flush_to_complete(self, mock_api_client, conversa
 
         result = await close_task
         assert result is not None
+        assert result.id == "activity-1"
         assert mock_api_client.send_call_count == 1
         assert mock_api_client.sent_activities[0].text == "Response text"