Broadcast Pool

Privacy-preserving Bitcoin transaction scheduling and broadcasting tool. It sits between a wallet (Sparrow / Liana) and an Electrum indexer (electrs / Fulcrum), exposing an Electrum server that intercepts blockchain.transaction.broadcast and holds signed transactions in a virtual mempool until they meet a chosen broadcast criterion (immediate, scheduled date/time, fiat price, or block height).

Architecture

Sparrow / Liana  ──tcp:50050──▶  Broadcast Pool (Electrum server + virtual mempool)
                                        │
                                        ├──▶ electrs / Fulcrum   (history, balances, UTXOs)
                                        └──▶ Bitcoin Core RPC     (final broadcast)

• Wallet broadcasts are intercepted and retained instead of being relayed.
• The wallet still sees the pending tx (the pool injects it into history/mempool responses) so balances update immediately.
• A scheduler broadcasts the tx to the network when its trigger fires.

Build

cargo build --release
./target/release/broadcast-pool start

Configuration

Configured via config/default.toml and BROADCAST_POOL_* environment variables (network, indexer, Bitcoin Core RPC, Electrum host/port). Never commit real RPC credentials — inject them via environment variables.

Umbrel

Packaged as an Umbrel Community Store app under umbrel-app/sparrow-broadcast-pool/. The Docker image is published to ghcr.io/criptoworld8484/broadcast-pool-umbrel by the .github/workflows/umbrel-docker.yml workflow when a v* tag is pushed.

See TROUBLESHOOTING.md and UMBREL.md for deployment and debugging notes.

License

MIT