Hi Insiders. This is Tuma, open-source reporter from the Insider Edition.

In this week’s update we feature the current work to add support for splicing and dual-funding to taproot channels in the BOLTs specifications.

We also cover several news from the Bitcoin ecosystem. Fabian Jahr is teaming with Payjoin to integrate that protocol with Cross-Input Signature Aggregation (CISA), Core developer l0rinc is working to remove AssumeUTXO , Wavelength is now available on Mainnet, and more.

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Highlights from the Bitcoin developer ecosystem

I spent 10+ hours in open-source developer calls in the Bitcoin ecosystem last week. Here is what caught my eye:

• Lightning developers are working to add support for splicing and dual-funding transactions in taproot channels
  • During the monthly meeting, on Monday 19th, Lightning developers discussed the ongoing effort to add support for splicing and dual-funding transaction in taproot channels. The work is currently reviewable in PR1324 in the BOLTs repository.
  • Taproot Lightning channels were introduced last May as a way to improve privacy, security, and flexibility of the system. In particular, the new taproot channels use MuSig2 key aggregation to combine two keys into one, with the multisig output becoming a single P2TR key, and tapscript trees capabilities.
  • The new update to the specifications aims to add nonces in various messages of the peer protocol to allow creating musig2 partial signatures during dual-funding and splicing. It also allows to omit the prevtx field when using taproot, since that field had to be included to prevent transaction malleability when using pre-segwit inputs.

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A BIPs Update

In the last days there was some movement in the BIP repository. Specifically, one new BIP has been published by BIP maintainer Murchandamus.

Published BIPs#

A list of recently published BIPs

BIP139: Wallet Metadata Backup Format#

Published On: October 24th, 2026

Layer: Applications

BIP139 specifies a standard way to store various type of metadata, such as account descriptors, keys, labels, PSBTs, and more, allowing compatibility between different wallet implementations, simpler wallet migration, and easier recovery processes.

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Other News from the Bitcoin World

• AssumeUTXO Removal: Bitcoin Core develoepr l0rinc announced a draft proposal to remove the AssumeUTXO feature from the Bitcoin reference implementation. This comes after in-person discussions during the Core Dev meeting.

  • AssumeUTXO allows a new user bootstrapping a node to import the UTXO set from an external source to start transacting right away, while the classic Initial Block Download (IBD) starts in the background.
  • According to l0rinc, this feature adds several layers of complexity around the codebase, making porposed changes difficult to implement. Moreover, the feature does not seem to be widely used by noderunners.
  • L0rinc’s provided a reference implementation of what the removal of AssumeUTXO would look like in PR36598. However, he stated that discussion on whether to remove the feature is still ongoing between maintainers.

• Payjoin + CISA = PISA: Fabian Jahr announced PISA, a new integration between Payjoin and CISA.

  • Jahr shared a video explaining how PISA could increase privacy on-chain — breaking the common ownership heuristic used in chain analysis —, while at the same time saving in fees.
  • To send a payment, both Alice and Bob can provide an input, as in a classical Payjoin transaction. Once Alice gets back the transaction with Bob’s input and signatures, she can leverage CISA so as to aggregate their signatures into one single signature.
  • To make it work, Jahr modified Bitcoin Core to include BIP460, the soft work that would bring CISA to Bitcoin. Thus, the provided test implementation is available only on regtest.

• Bitcoin Design <> AI: The Bitcoin Design Community — supported by Spiral — is launching a research initiative to understand how the Bitcoin Design Guide should evolve so that it can be easily leveraged by AI agent.

  • The Bitcoin Designer Community is specifically looking for builders of Bitcoin and Lightning wallet to understand how AI is used in their workflows, if the Guide is ready for the AI-driven development age, and which could be the areas where it could be improved.

• Wavelength on Mainnet: Lightning Labs announced that Wavelength — their implementation of the Ark protocol — was finally available on mainnet. Wavelength was announced in July, promising fast integration of Bitcoin payments in any application.

• Bitcoin-backed Dollars on Cashu: Ducat — a Bitcoin-native credit and stablecoin protocol — announced that they had launched a Bitcoin-backed dollar stablecoin built on top of the Cashu protocol. Ducat’s mint would allow users to deposit their UNIT stablecoin and receive newly minted ecash tokens.

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More from BTC++ Insider Edition

News Hour#

• BTC++ News Hour: Check out our Friday livestream, where Matthew Vuk and I discuss the most interesting news of the week from the Bitcoin developer ecosystem. This time, we hosted Brandon Black — known in cyberspace as reardencode — to talk about rbitcoin, a Bitcoin full-node implementation in Rust.

Videos#

• Aleksei Moskvin — BTC++ Insider Interviews: Alksei Moskving of [[alloc]init] talks to the Insider about the Shielded Bitcoin metaprotocol: private transfers on Bitcoin L1, encrypted notes, and wallet recovery from a seed phrase.
• Alex Bragin — BTC++ Insider Interviews: Alex Bragin — CTO at Jan3 — talks to the Insider about his commitment to Liquid, finally coming to resolution as peg-out functionality is restored.
• Michael from Boltz — BTC++ Insider Interviews: Michael — Former CTO at Boltz — talks to the Insider about why he shut down the swap service, how AI changed the risk equation, and why he’s still optimistic about the future of software.
• Jussi Tiira — BTC++ Insider Interviews: Jussi Tiira of the Finnish Bitcoin Association talks to the insider about his quest to educate Finnish MPs about Bitcoin.
• Rene Pickhardt — BTC++ Insider Interviews: Lightning researcher Rene Pickhardt talks to the Insider about Lightning’s scaling limits, on-chain bottlenecks and the case for multiparty channels.

Articles#

• We’re reimplementing private broadcast - This Week in Bitcoin Core #63

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Looking for an opportunity to join up with some bitcoin devs in person? Join us in Seoul this November 5-6 to talk about privacy in Bitcoin!