This week’s newsletter summarizes an update to the liquidity advertisements specification. Also included are our regular sections with selected questions and answers from the Bitcoin Stack Exchange, announcements of new releases and release candidates, and descriptions of notable changes to popular Bitcoin infrastructure software.


  • Update to the liquidity ads specification: Lisa Neigut posted to the Lightning-Dev mailing list to announce an update to the specification for liquidity advertisements. That feature, implemented in Core Lightning and currently being worked on for Eclair, allows a node to announce that it is willing to contribute funds to a dual-funded channel. If another node accepts the offer by requesting to open a channel, the requesting node must pay the offering node an upfront fee. This allows a node needing incoming liquidity (e.g., a merchant) to find well-connected peers that can provide that liquidity at a market rate, entirely using open source software and the decentralized LN gossip protocol.

    The updates include a few structural changes plus increased flexibility to the contract duration and forwarding fee ceiling. The post received several replies on the mailing list and additional changes to the specification are expected. Neigut’s post also notes that the current construction of liquidity advertisements and channel announcements makes it theoretically possible to cryptographically prove one case where a party is violating its contract. It’s an open problem to design an actual compact fraud proof that could be used in a bond contract to incentivize contract compliance.

Selected Q&A from Bitcoin Stack Exchange

Bitcoin Stack Exchange is one of the first places Optech contributors look for answers to their questions—or when we have a few spare moments to help curious or confused users. In this monthly feature, we highlight some of the top-voted questions and answers posted since our last update.

Releases and release candidates

New releases and release candidates for popular Bitcoin infrastructure projects. Please consider upgrading to new releases or helping to test release candidates.

  • Core Lightning 23.11 is a release of the next major version of this LN node implementation. It provides additional flexibility to the rune authentication mechanism, improved backup verification, new and features for plugins.

  • Bitcoin Core 26.0rc3 is a release candidate for the next major version of the predominant full-node implementation. There’s a testing guide available.

Notable code and documentation changes

Notable recent changes in Bitcoin Core, Core Lightning, Eclair, LDK, LND, libsecp256k1, Hardware Wallet Interface (HWI), Rust Bitcoin, BTCPay Server, BDK, Bitcoin Improvement Proposals (BIPs), Lightning BOLTs, and Bitcoin Inquisition.

  • Rust Bitcoin #2213 amends the weight prediction for P2WPKH inputs processes during fee estimation. Since transactions with high-s signatures are considered non-standard since Bitcoin Core versions 0.10.3 and 0.11.1, transaction building processes can safely assume that any serialized ECDSA signatures will at most take 72 bytes instead of the previously used upper bound of 73 bytes.

  • BDK #1190 adds a new Wallet::list_output method that retrieves all outputs in the wallet, both spent outputs and unspent outputs. Previously, it was easy to get a list of unspent outputs but difficult to get a list of spent outputs.