Add funding redeem script to `ChannelDetails` and `ChannelPending` event #4234

benthecarman · 2025-11-19T15:44:39Z

Original context and motivation comes from here: lightningdevkit/ldk-node#677 (comment)

When splicing-in, the default case is our channel utxo + our wallet utxos being combined. This works great however, it can give our wallet issues calculating fees after the fact because our wallet needs to know about our channel's utxo. We currently have it's outpoint and satoshi value available, but not its output script so we are unable to construct the TxOut for the channel. This adds the redeem script to the ChannelDetails and ChannelPending event which gives us enough information to be able to construct it.

ldk-reviews-bot · 2025-11-19T15:44:43Z

👋 Thanks for assigning @jkczyz as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

jkczyz

LGTM

lightning/src/events/mod.rs

lightning/src/ln/channel_state.rs

ldk-reviews-bot · 2025-11-19T16:38:31Z

👋 The first review has been submitted!

Do you think this PR is ready for a second reviewer? If so, click here to assign a second reviewer.

codecov · 2025-11-19T18:16:26Z

Codecov Report

❌ Patch coverage is 69.04762% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.32%. Comparing base (6d9c676) to head (e3ebe7a).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
lightning/src/ln/channel_state.rs	46.66%	8 Missing ⚠️
lightning/src/routing/router.rs	50.00%	4 Missing ⚠️
lightning/src/ln/channelmanager.rs	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4234      +/-   ##
==========================================
- Coverage   89.32%   89.32%   -0.01%     
==========================================
  Files         180      180              
  Lines      138641   138680      +39     
  Branches   138641   138680      +39     
==========================================
+ Hits       123844   123877      +33     
- Misses      12174    12179       +5     
- Partials     2623     2624       +1

Flag	Coverage Δ
fuzzing	`35.97% <46.66%> (+<0.01%)`	⬆️
tests	`88.69% <69.04%> (-0.01%)`	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

jkczyz

As noted in lightningdevkit/ldk-node#677 (comment), we should include this in SplicePending, too, since subsequent splices will spend the new funding output. Feel free to do it in a follow-up if you prefer.

benthecarman · 2025-11-19T19:42:02Z

Added to the SplicePending event

jkczyz · 2025-11-19T19:50:32Z

lightning/src/ln/channelmanager.rs

+											new_funding_redeem_script: chan
+												.funding
+												.get_funding_redeemscript(),


This will still be the old funding until the splice is promoted. You'll need to communicate it through SpliceFundingNegotiated.

jkczyz · 2025-11-19T20:51:34Z

lightning/src/events/mod.rs

 		channel_type: Option<ChannelTypeFeatures>,
+		/// The witness script that can be used to spend the funding output for this channel.
+		///
+		/// This field will be `None` for objects serialized with LDK versions prior to 0.2.0.


Sounds like this won't make 0.2 but feel free to petition @TheBlueMatt :)

TheBlueMatt

I'll be honest I'm pretty annoyed we're talking about changing the 0.2 API almost two months after we intended to ship it, but if we land this today maybe we still include it in 0.2.

lightning/src/events/mod.rs

TheBlueMatt · 2025-11-20T15:00:33Z

lightning/src/ln/channel_state.rs

+	/// The witness script that can be used to spend the funding output for this channel.
+	///
+	/// This field will be `None` for objects serialized with LDK versions prior to 0.2.0.
+	pub funding_redeem_script: Option<bitcoin::ScriptBuf>,
 }

 impl ChannelDetails {
 	/// Gets the current SCID which should be used to identify this channel for inbound payments.
 	/// This should be used for providing invoice hints or in any other context where our
 	/// counterparty will forward a payment to us.
 	///
 	/// This is either the [`ChannelDetails::inbound_scid_alias`], if set, or the
 	/// [`ChannelDetails::short_channel_id`]. See those for more information.
 	pub fn get_inbound_payment_scid(&self) -> Option<u64> {
 		self.inbound_scid_alias.or(self.short_channel_id)
 	}

 	/// Gets the current SCID which should be used to identify this channel for outbound payments.
 	/// This should be used in [`Route`]s to describe the first hop or in other contexts where
 	/// we're sending or forwarding a payment outbound over this channel.
 	///
 	/// This is either the [`ChannelDetails::short_channel_id`], if set, or the
 	/// [`ChannelDetails::outbound_scid_alias`]. See those for more information.
 	///
 	/// [`Route`]: crate::routing::router::Route
 	pub fn get_outbound_payment_scid(&self) -> Option<u64> {
 		self.short_channel_id.or(self.outbound_scid_alias)
 	}

+	/// Gets the funding output for this channel, if available.


These need docs on when it changes wrt a splice. When a splice happens at what point in the splice do these switch over to the new values?

Added, looked through the code and seems it happens after the commitment signed messages were exchanged.

jkczyz · 2025-11-20T16:05:40Z

lightning/src/ln/channel_state.rs

+	/// During a splice, the funding output will change and this value will be updated
+	/// after the `commitment_signed` messages have been exchanged.


Hmmm... this should only change when the splice has been promoted (i.e., when the FundingScope from the pending splice is swapped in for the current FundingScope). That happens after splice_locked has been exchanged.

rust-lightning/lightning/src/ln/channel.rs

Line 11200 in 6d9c676

core::mem::swap(&mut self.funding, funding);

Maybe you were looking at channel establishment?

Oh I see, i think what I was looking at when that FundedChannel was being created/updated here:

rust-lightning/lightning/src/ln/channel.rs

Line 2219 in e3ebe7a

self.phase = ChannelPhase::Funded(funded_channel);

Original context and motivation comes from here: lightningdevkit/ldk-node#677 (comment) When splicing-in, the default case is our channel utxo + our wallet utxos being combined. This works great however, it can give our wallet issues calculating fees after the fact because our wallet needs to know about our channel's utxo. We currently have it's outpoint and satoshi value available, but not its output script so we are unable to construct the TxOut for the channel. This adds the redeem script to the `ChannelDetails` and `ChannelPending` event which gives us enough information to be able to construct it.

benthecarman mentioned this pull request Nov 19, 2025

Channel splicing support lightningdevkit/ldk-node#677

Merged

benthecarman requested a review from jkczyz November 19, 2025 15:44

benthecarman force-pushed the redeem-script-channel-pending-detials branch 4 times, most recently from b2f8584 to 1c29113 Compare November 19, 2025 16:24

jkczyz reviewed Nov 19, 2025

View reviewed changes

lightning/src/events/mod.rs Outdated Show resolved Hide resolved

lightning/src/events/mod.rs Outdated Show resolved Hide resolved

lightning/src/ln/channel_state.rs Outdated Show resolved Hide resolved

lightning/src/ln/channel_state.rs Outdated Show resolved Hide resolved

benthecarman force-pushed the redeem-script-channel-pending-detials branch from 1c29113 to 436dc4b Compare November 19, 2025 16:42

jkczyz previously approved these changes Nov 19, 2025

View reviewed changes

benthecarman dismissed jkczyz’s stale review via 4f5125c November 19, 2025 19:41

jkczyz reviewed Nov 19, 2025

View reviewed changes

benthecarman force-pushed the redeem-script-channel-pending-detials branch 2 times, most recently from e0c0b62 to 5b5c8d6 Compare November 19, 2025 20:06

jkczyz previously approved these changes Nov 19, 2025

View reviewed changes

TheBlueMatt reviewed Nov 20, 2025

View reviewed changes

benthecarman dismissed jkczyz’s stale review via c5428d2 November 20, 2025 15:43

benthecarman force-pushed the redeem-script-channel-pending-detials branch from 5b5c8d6 to c5428d2 Compare November 20, 2025 15:43

jkczyz reviewed Nov 20, 2025

View reviewed changes

benthecarman added 2 commits November 20, 2025 10:35

Add funding redeem script to `SplicePending' event

e3ebe7a

benthecarman force-pushed the redeem-script-channel-pending-detials branch from c5428d2 to e3ebe7a Compare November 20, 2025 16:35

jkczyz approved these changes Nov 20, 2025

View reviewed changes

jkczyz merged commit f325458 into lightningdevkit:main Nov 21, 2025
26 checks passed

jkczyz added the backport 0.2 label Nov 21, 2025

benthecarman deleted the redeem-script-channel-pending-detials branch November 21, 2025 04:11

benthecarman mentioned this pull request Nov 21, 2025

Backport 4234 to 0.2 #4239

Open

		/// During a splice, the funding output will change and this value will be updated
		/// after the `commitment_signed` messages have been exchanged.

Add funding redeem script to ChannelDetails and ChannelPending event #4234

Add funding redeem script to ChannelDetails and ChannelPending event #4234

Uh oh!

Conversation

benthecarman commented Nov 19, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

ldk-reviews-bot commented Nov 19, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

jkczyz left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

ldk-reviews-bot commented Nov 19, 2025

Uh oh!

codecov bot commented Nov 19, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Codecov Report

Uh oh!

jkczyz left a comment

Choose a reason for hiding this comment

Uh oh!

benthecarman commented Nov 19, 2025

Uh oh!

jkczyz Nov 19, 2025

Choose a reason for hiding this comment

Uh oh!

benthecarman Nov 19, 2025

Choose a reason for hiding this comment

Uh oh!

jkczyz Nov 19, 2025

Choose a reason for hiding this comment

Uh oh!

TheBlueMatt left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

TheBlueMatt Nov 20, 2025

Choose a reason for hiding this comment

Uh oh!

benthecarman Nov 20, 2025

Choose a reason for hiding this comment

Uh oh!

jkczyz Nov 20, 2025

Choose a reason for hiding this comment

Uh oh!

benthecarman Nov 20, 2025

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

Add funding redeem script to `ChannelDetails` and `ChannelPending` event #4234

Add funding redeem script to `ChannelDetails` and `ChannelPending` event #4234

benthecarman commented Nov 19, 2025 •

edited

Loading

ldk-reviews-bot commented Nov 19, 2025 •

edited

Loading

codecov bot commented Nov 19, 2025 •

edited

Loading