Bitcoin's threshold for trust-minimization—without a soft fork | SAM BLACKSHEAR

— Sam Blackshear's background in programming language research and his recruitment to Meta's Libra project to design Move, a smart contract language emphasizing explicit value representation and minimality to prevent common security failures in systems like Solidity.

— The transition from Libra to Mysten Labs: after Libra faced regulatory obstacles, five co-founders (including Blackshear) departed in fall 2021 to build Sui, a blockchain incorporating Move with performance optimizations for throughput, latency, and horizontal scaling via object-based transaction architecture.

— Hashi: Mysten's new Bitcoin primitive using a two-of-two multisig (Sui validator set + enclave-run guardian) with a 30-day timelock fallback, designed to minimize trust assumptions for Bitcoin DeFi (borrowing, yield strategies, collateral use) without requiring soft forks.

— Trust architecture in Hashi: users need to trust that no more than one-third of staking power in the Sui validator set is malicious (Byzantine Fault Tolerance), plus enclave integrity; the guardian adds a safety layer against simultaneous validator compromise.

— Move's design philosophy: explicit coin types, functional transaction model with declared input/output objects, and avoidance of dynamic dispatch eliminate entire categories of bugs that plague EVM-based contracts; Sui adapted this further by shifting from account-based to object-based storage.

— Positioning Hashi against other Bitcoin bridges: emphasizes minimized trust relative to federated custodians, combined with Sui's three-year track record, formal verification efforts, and DeFi safety practices; notes that a Bitcoin soft fork enabling trustless bridges would supersede Hashi's complexity, but the thesis around DeFi utility would remain.

— Builders interested in Bitcoin DeFi should evaluate Sui and Move if they prioritize safe programmability and formal verification; the language's design prevents entire classes of vulnerabilities (reentrancy, missing value checks) at the language level rather than relying on developer discipline.

— Bitcoin holders skeptical of custodial bridges can test Hashi on Sui testnet now; the architecture offers tunable trust via multiple validation layers (Sui validators + guardian enclave + timelock escape hatch), with feedback and bug bounties sought before mainnet launch.

— Consider Hashi's core use case—borrowing against unmoved Bitcoin—as a financial primitive enabling yield strategies and collateral deployment; this differs from payment-focused L2s and may appeal to institutions with large Bitcoin holdings seeking to scale strategies without selling.