Release v0.4.0

By Alekos Filini

A new release of BDK is out: the v0.4.0 release brings updated dependencies, more sanity checks and an overhauled API to build transactions.

You can find the full v0.4.0 changelog on GitHub.

What’s new in v0.4.0

Below are some highlights of the new improved APIs coming with this release:

A new API to build transaction

The star of this release is the new API designed and implemented by @llfourn that brings much more flexibility to the way we create transactions: originally the process of making a transaction involved the creation of a TxBuilder which was used to configure how the wallet should build the transaction. Things like which outputs to create, what nLockTime to use, which UTXOs to spend, and much more.

Once fully configured, this builder was then given to the Wallet itself in a Wallet::create_tx() or Wallet::bump_fee() call: the Wallet would try to follow the instructions given by the builder, but in case of conflicting or straight-up wrong options it would have to fail and force the user to start over.

The new API maintains the concept of a builder, but it changes the way it’s created so that it always contains a reference to the main Wallet instance. What this means is that most checks can now be performed right when something is added to the builder, not at the end, allowing the user to recover from errors instead of having to start over.

This also opens the door to even more improvements and additions, such as a way to spend foreign utxos in a transaction, or even a way to bump the fees of multiple transactions at once by batching them together, which saves a bit of space and money.

let send_to = wallet.get_new_address()?;
let (psbt, details) = {
    let mut builder = wallet.build_tx();
        .add_recipient(send_to.script_pubkey(), 50_000)

Upgraded dependencies

This release also brings many updates to our dependencies, including:

  • bitcoin to v0.26
  • miniscript to v5.1
  • electrum-client to v0.6
  • tokio to v1
  • reqwest to v0.11
  • cc to >= v1.0.64

Compact Filters example

Thanks to the upgrade to bitcoin v0.26 all the issues related to new networking messages in the P2P Bitcoin network have been fixed, which means that we can finally use our (experimental) compact filters Blockchain with standard Bitcoin Core 0.21 full nodes.

The following example has also been added to the repository and can be run with cargo run --features=compact_filters --example compact_filters_balance.

/// This will return wallet balance using compact filters
/// Requires a synced local bitcoin node 0.21 running on testnet with blockfilterindex=1 and peerblockfilters=1
fn main() -> Result<(), CompactFiltersError> {

    let num_threads = 4;
    let mempool = Arc::new(Mempool::default());
    let peers = (0..num_threads)
        .map(|_| Peer::connect("localhost:18333", Arc::clone(&mempool), Network::Testnet))
        .collect::<Result<_, _>>()?;
    let blockchain = CompactFiltersBlockchain::new(peers, "./wallet-filters", Some(500_000))?;
    info!("done {:?}", blockchain);
    let descriptor = "wpkh(tpubD6NzVbkrYhZ4X2yy78HWrr1M9NT8dKeWfzNiQqDdMqqa9UmmGztGGz6TaLFGsLfdft5iu32gxq1T4eMNxExNNWzVCpf9Y6JZi5TnqoC9wJq/*)";

    let database = MemoryDatabase::default();
    let wallet =
        Arc::new(Wallet::new(descriptor, None, Network::Testnet, database, blockchain).unwrap());
    wallet.sync(noop_progress(), None).unwrap();
    info!("balance: {}", wallet.get_balance()?);


A huge thanks to everybody who contributed to this new release with suggestions, pull requests and bug reports.

Since the v0.3.0 release around a month ago, we’ve had 59 new commits made by 8 different contributors for a total of 2463 additions and 1991 deletions. Here’s the full diff.

A special thanks to the new contributor for this release: