Honestly, assuming the linearity of QM, the many worlds interpretation also provides an answer to this IMO. Your observations, thoughts, etc, exist in the doma

Honestly, assuming the linearity of QM, the many worlds interpretation also provides an answer to this IMO. Your observations, thoughts, etc, exist in the domain of eigenvalues of measurement operators applied to a quantum state and the universe itself is a massively entangled state vector in hilbert space. There is no decoherence at all. Instead, anything you can conceive of doing or measuring is actually a linear quantum operation taking a well described state in hilbert space from one state to another. What we actually see, and observe, and perceive is all just computation in the domain of the eigenvalues rather than the underlying true state of the universe as a vector in hilbert space. The fact that you remember a consistent history is because your 'remembering' is itself one such eigenvalue of a measurement operator applied to a massively entangled set of histories and you only think you get one result because that thinking itself occurs in the domain of the eigenvalues rather than the true state.