Bitcoin quantum defense debate: BitMEX “canary” wait-and-react plan

Bitcoin developers are debating a new way to defend against a future quantum computing threat. Instead of locking vulnerable coins on a fixed schedule, BitMEX Research proposes a “canary” system that would only restrict older wallets if a quantum-capable attacker proves the threat on-chain. The design uses a special Bitcoin address holding a bounty. A spend from that address would act as public evidence that Bitcoin’s signature scheme has been broken. Once triggered, it would automatically impose a retroactive network-wide freeze on vulnerable older coins. Supporters argue this “wait and react” approach avoids the “authoritarian” feel of BIP-361, a proposal to phase out vulnerable addresses on a predetermined five-year timeline—potentially leaving unmigrated coins permanently frozen. The canary plan also adds a “safety window” so vulnerable funds may still move, but recipients cannot spend for a period (around a year), aiming to make stealth theft harder. Critics say the proposal hinges on an uncomfortable assumption: the first quantum attacker will claim the bounty rather than execute what could be the largest Bitcoin theft in history. If the attacker instead steals quietly at scale, the defense could fail and Bitcoin may still face the worst-case scenario that the fixed-timeline plan was meant to prevent.