Even with identical slot names, two separate classes define different C-level layouts, so MI still fails at runtime. ```python class First: __slots__ = ("x",) class Second: __slots__ = ("x",) class Both(First, Second): ... ``` **Sandbox:** [Pyrefly](https://pyrefly.org/sandbox/?project=N4IgZglgNgpgziAXAAlHAhgOwCYCMD2AHgHQAOAnksiAMZTpxzIBiEATnAC6IA6myA5AH0hcKPk5wRyALzIAFDxCElAGgCUfPnQZMAyjBr4cvfoJFiJUobIVKVIDVsw7GyAEISAFvNYdOqsgGRjjqKMQRfCAAvoEg6DScEABuMKywVCAYOAQkFDFAA)
Even with identical slot names, two separate classes define different C-level layouts, so MI still fails at runtime.
Sandbox: Pyrefly