Added fallback for sandbox spec service (#13317)

Co-authored-by: openhands <openhands@all-hands.dev>

tests/unit/app_server/test_app_conversation_skills_endpoint.py

@@ -501,3 +501,73 @@ class TestGetConversationSkills:
         data = json.loads(content)
         assert 'skills' in data
         assert len(data['skills']) == 0
+
+    async def test_get_skills_uses_default_sandbox_spec_when_not_found(self):
+        """Test endpoint uses default sandbox spec when original spec is not found.
+
+        Arrange: Setup sandbox with spec that returns None, but default spec available
+        Act: Call get_conversation_skills endpoint
+        Assert: Response is successful using default sandbox spec
+        """
+        # Arrange
+        conversation_id = uuid4()
+        sandbox_id = str(uuid4())
+
+        mock_conversation = AppConversation(
+            id=conversation_id,
+            created_by_user_id='test-user',
+            sandbox_id=sandbox_id,
+            sandbox_status=SandboxStatus.RUNNING,
+        )
+
+        mock_sandbox = SandboxInfo(
+            id=sandbox_id,
+            created_by_user_id='test-user',
+            status=SandboxStatus.RUNNING,
+            sandbox_spec_id=str(uuid4()),
+            session_api_key='test-api-key',
+            exposed_urls=[
+                ExposedUrl(name=AGENT_SERVER, url='http://localhost:8000', port=8000)
+            ],
+        )
+
+        # Default sandbox spec to be used as fallback
+        default_sandbox_spec = SandboxSpecInfo(
+            id=str(uuid4()), command=None, working_dir='/workspace'
+        )
+
+        mock_user_context = MagicMock(spec=UserContext)
+        mock_app_conversation_service = _make_service_mock(
+            user_context=mock_user_context,
+            conversation_return=mock_conversation,
+            skills_return=[],
+        )
+
+        mock_sandbox_service = MagicMock()
+        mock_sandbox_service.get_sandbox = AsyncMock(return_value=mock_sandbox)
+
+        mock_sandbox_spec_service = MagicMock()
+        # Original sandbox spec lookup returns None
+        mock_sandbox_spec_service.get_sandbox_spec = AsyncMock(return_value=None)
+        # Default sandbox spec is available
+        mock_sandbox_spec_service.get_default_sandbox_spec = AsyncMock(
+            return_value=default_sandbox_spec
+        )
+
+        # Act
+        response = await get_conversation_skills(
+            conversation_id=conversation_id,
+            app_conversation_service=mock_app_conversation_service,
+            sandbox_service=mock_sandbox_service,
+            sandbox_spec_service=mock_sandbox_spec_service,
+        )
+
+        # Assert
+        assert response.status_code == status.HTTP_200_OK
+        # Verify that get_default_sandbox_spec was called as fallback
+        mock_sandbox_spec_service.get_default_sandbox_spec.assert_called_once()
+        content = response.body.decode('utf-8')
+        import json
+
+        data = json.loads(content)
+        assert 'skills' in data