I’ve open-sourced btc-safe, a self-hosted, watch-only Bitcoin multisig coordinator. One owner proposes a transaction. Every co-signer sees it in a shared queue and signs from their own device. It broadcasts once M of N have signed.
• Watch-only: the server stores xpubs and descriptors only. It never holds keys and never signs.
• Independent checks: the browser re-derives change and receive addresses from the xpubs and cross-checks every PSBT against the server.
• Signers: Ledger (WebHID), Trezor, Sparrow and Caravan import, and PSBT files.
• Accounts: TOTP 2FA and per-wallet roles (admin, proposer, viewer). Reorg-aware confirmations.
• Stack: Rust (axum, bdk_wallet, Postgres) and Next.js. MIT licensed.
Try it (signet, no real funds): https://web-production-56752.up.railway.app. Sign up with any email, create a 2-of-3, and fund it from a signet faucet.
