Quantum-Resistant Address Migration Protocol proposes a countdown window during which users must move funds from legacy to quantum-resistant wallets

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During a migration window, users would still be able to move funds freely. The BIP calls for wallet developers, block explorers and “other infrastructure” to build tools and warnings to help users comply.

Cruz’s QRAMP proposal outlines how the hard fork would work. Once activated, it would trigger a countdown. Users must “sweep” their bitcoins from vulnerable legacy addresses to new quantum-resistant wallets. If they fail to do so before the deadline, Bitcoin Core — the dominant full-node software — will automatically reject any attempt to spend those funds.