Simplicity on Liquid: post-quantum signatures, Lending v2, and safer wallets

Blockstream says its Simplicity developer stack is progressing quickly on Liquid. SimplicityHL v0.7.0 improves modular contract development: native module imports, cleaner bytecode for auditability, and better error diagnostics. For local validation, the Simplicity SDK (Smplx v0.0.8) tightens the CLI and fixes edge-case execution bugs, aiming for a faster write→compile→test iteration loop without constantly spinning up regtest. In March 2026, Blockstream Research deployed the first post-quantum-signed transactions on Liquid mainnet. The scheme is SHRINCS, using compact 324-byte first-use signatures and ~16-byte additions in subsequent stateful signatures. The full transaction (including the Simplicity verification program) is ~38KB today, with room to reduce overhead via a future native opcode. Importantly, the post-quantum feature shipped as a Simplicity contract on Liquid without a network-wide consensus change. Blockstream also finalized the Lending v2 contract architecture, providing a tested template for Liquid lending and credit apps. The broader ecosystem is adopting Simplicity through projects and ongoing hackathons. Planned next steps include: Simplicity-specific fuzz testing (to run millions of randomized inputs before mainnet), an Elements Library Improvement Proposal (ELIP) for a standardized wallet interface to reduce fragile browser-extension integrations, and a Contract Registry (modeled on Ethereum ERC-7730 clear-signing) plus tx-manifest.json for human-readable signing. The goal is safer user approvals—users can verify audited contract templates and view clear intent instead of blind bytecode signing.