When quantum computing eventually forces Bitcoin to upgrade its signing and address infrastructure, only one type of Layer 2 solution truly preserves Bitcoin's security model—the one where users retain the absolute right to exit back onto the main chain.

This is where the architecture matters most. A Bitcoin L2 that enforces user exits directly on Bitcoin creates a fundamentally different risk profile. BitVM2 demonstrates this approach: it's engineered around Bitcoin-based arbitration and enforceable settlement mechanisms. The security guarantees track Bitcoin's own cryptographic assumptions, which means the protocol upgrades alongside quantum threats the way Bitcoin itself does.

This isn't just a nice feature. It's the difference between a sidechain and genuine Bitcoin security inheritance.