Lightning Specification Meeting 2025/03/24

[t-bast]

The meeting will take place on Monday 2025/03/24 at 7pm UTC (5:30am Adelaide time) on Libera Chat IRC #lightning-dev. It is open to the public.

A video link is available for higher bandwidth communication: https://meet.jit.si/Lightning-Spec-Meeting

Recently Updated Proposals / Seeking Review

This section contains changes that have been opened or updated recently and need feedback from the meeting participants.

• Allow non-initiator to RBF dual-funded channels Allow either node to send tx_init_rbf in v2 establishment #1236
• Dual funding reconnect commit_sig retransmission Do not unnecessarily retransmit commitment_signed in dual funding #1214
• Assume option_channel_type Assume option_channel_type #1232
• Splicing Channel Splicing (feature 62/63) #1160
• Taproot extension-bolt: simple taproot channels (feature 80/81) #995
• Taproot gossip extension-bolt: taproot gossip (features 32/33) #1059
• Dynamic Commitments Extension/dynamic commitments #1117
• Attributable errors Attributable failures (feature 36/37) #1044
• 0-fee commitments Zero-fee commitments using v3 transactions (feature 40/41) #1228
• Channel jamming draft: HTLC Endorsement to Mitigate Channel Jamming #1071 Project Updates: Hybrid Channel Jamming Mitigation #1218
• Bolt 12 contacts: blip-0042: Bolt 12 Contacts blips#42
• Liquidity ads Extensible Liquidity Ads #1153
• Trampoline routing Trampoline Routing (2021 edition) (Feature 56/57) #829 and Trampoline onion format (Feature 56/57) #836
• Async payments Support async payments in BOLT 12 #1149
• BOLT 12 recurrence BOLT 12: re-add recurrence support. #1240

Stale Proposals

This section contains pending changes that may not need feedback from the meeting participants, unless someone explicitly asks for it during the meeting. These changes are usually waiting for implementation work to happen to drive more feedback.

• Inbound fees Inbound routing fees blips#18 and Add a bLIP for backwards-compatible inbound fees blips#22

Waiting for interop

This section contains changes that have been conceptually ACKed and are waiting for at least two implementations to fully interoperate.
They most likely don't need to be covered during the meeting, unless someone asks for updates.

• Zero reserve Add option_zero_reserve (FEATURE 64/65) #1140 (follow-up on bolt2: relax channel_reserve_satoshis requirements #1133 to include a feature bit)
• Don't force close until error is received after channel_reestablish Nodes shouldn't publish their commitment when receiving outdated channel_reestablish #934

Long Term Updates

This section contains long-term changes that need review, but require a substantial implementation effort.

• Simplified commitment Feature 106/107: option_simplified_update. #867
• lnprototest (https://github.com/rustyrussell/lnprototest)

[ariard]

That should be checked : https://delvingbitcoin.org/t/disclosure-lnd-excessive-failback-exploit/1493/6

[Roasbeef]

allow non-initiator to rbf dual funded channel?

• seems reasonable, any pitfalls?

option chan type:

• few nodes not setting it, but likely well abandoned
• impls should either start to assume it, or set it to required

splicing:

• can just do it in chan reest instead of doing it in splice locked?
• race condition of update-add and splice locked at the same time?
  • or isn't an issue in steady state?
  • may not be a real issue until we start to use taproot
    • issue where they don't know to send nonces for the old stuff?
    • extra nonces can resolve things?
• extra nonces may work, but need to check the code to make sure this works
• scaling confs:
  • want to scale confs with each splice that updates
  • if you make a large channel, then splice it all out, and you have the old conf target -- less secure
    • when do you forget the old state?
    • just use a static min depth the entire time? if > 25% hash rate, then 8 confs is ideal?
  • simple impls just continue to watch for 100 blocks
  • other edge cases pop up if the splicing transaction has its inputs double spend as a result of a re-org (opportunity)

taproot:

• final changes needed for mini script compat re script
• lnd to implement the nonce changes for rbf coop close, then can do interop w/ the final feature bit

taproot gossip:

• spec not up to date w/ delving post

dyn commits:

• lots of channel types, hard to deprecate them
• renewed interest in this
• lnd last milestone re impl:
  • storing history on disk, need to remember params to handle breaches

0-fee commitments:

• bitciond 29 soon to be released
  • can update impls to start to use the latest APIs, test e2e

channel jamming:

• nothing new this meeting, hopefully some for next meeting

trampoline + blinded paths combo:

• can make a bLIP to put details to handle the transition from blinded paths to trampoline
• shift to reveal the payment secret from the onion?
• CLN looking into trampoline once again