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Add splice details to TransactionType::Splice#4570

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jkczyz wants to merge 2 commits intolightningdevkit:mainfrom
jkczyz:2026-04-splice-transaction-type
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Add splice details to TransactionType::Splice#4570
jkczyz wants to merge 2 commits intolightningdevkit:mainfrom
jkczyz:2026-04-splice-transaction-type

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@jkczyz jkczyz commented Apr 17, 2026

Surface splice broadcast metadata downstream, so consumers (notably LDK Node) can reconcile PaymentDetails / PendingPaymentDetails directly from the broadcaster callback.

  • TransactionType::Splice now carries contribution: Option<FundingContribution> — our local contribution for this round, and replaced_txid: Option<Txid> — the prior negotiated candidate being replaced on RBF. The alternative (reacting to SplicePending) is worse: that event races with BDK wallet sync and doesn't carry the replaced txid.
  • FundingContribution gains public getters for estimated_fee, inputs, and max_feerate; feerate is elevated from pub(super) to pub. Combined with existing value_added, outputs, change_output, this exposes everything a downstream consumer needs without reaching into the raw transaction.

The Hash derive on TransactionType is dropped (unused in the workspace; FundingContribution transitively contains ConfirmedUtxo which lacks Hash).

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ldk-reviews-bot commented Apr 17, 2026

👋 Thanks for assigning @TheBlueMatt 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 jkczyz requested review from TheBlueMatt and wpaulino April 17, 2026 21:14
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ldk-claude-review-bot commented Apr 17, 2026

I've thoroughly reviewed the entire diff, examining:

  1. The replaced_txid computation via checked_sub(2) on negotiated_candidates — correct, since the current candidate is pushed at line 9374 before this code runs.

  2. The contributions.last().cloned() logic — correctly returns None for pure acceptors (empty contributions vector) and Some(...) for parties that contributed. The reset_pending_splice_state pop logic at lines 7287-7294 correctly maintains the invariant that contributions.last() reflects the most recent negotiated round.

  3. The acceptor's tx_init_rbf handler (lines 13092-13162) — correctly pushes to contributions only when the acceptor actually contributes (queued or prior-adjusted), leaving it untouched otherwise.

  4. All test call sites — expected_replaced_txid values are consistent with the chaining semantics (first splice → None, RBF → Some(prior_txid), new splice after promotion → None).

  5. New public getters on FundingContribution — straightforward delegations to existing fields with appropriate return types.

  6. Hash derive removal — no HashMap<TransactionType, _> or HashSet<TransactionType> usage exists in the workspace.

  7. FundingTxInput accessibility — it's a public type alias for ConfirmedUtxo, which has public accessors (outpoint(), output(), sequence()), so the new inputs() getter is usable by downstream consumers.

No new issues found beyond what was covered in the prior review pass. The pre-existing concern about the rebroadcast path after 0-conf splice promotion (where monitor_updating_restored at channel.rs:9749-9757 would use TransactionType::Funding for a promoted splice transaction) remains valid but is not introduced by this PR.

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Comment thread lightning/src/ln/channel.rs Outdated
Comment on lines +7241 to +7256
if !self.context.is_manual_broadcast
&& !waiting_for_batch
&& self.funding.get_funding_tx_confirmation_height().is_none()
{
if let Some(tx) = &self.funding.funding_transaction {
return Some((
tx.clone(),
TransactionType::Funding {
channels: vec![(
self.context.counterparty_node_id,
self.context.channel_id,
)],
},
));
}
}
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Bug: After 0-conf splice promotion, self.pending_splice is None (cleared at maybe_promote_splice_funding line 11680) and self.funding holds the splice's FundingScope with funding_tx_confirmation_height == 0 and funding_transaction = Some(splice_tx). This initial-funding branch will match:

  • is_manual_broadcast = false (normal channel)
  • waiting_for_batch = false (channel is ChannelReady)
  • get_funding_tx_confirmation_height().is_none() = true (height is 0)
  • funding_transaction = Some(splice_tx)

...and return TransactionType::Funding wrapping the splice transaction. The splice branch below is unreachable because self.pending_splice is None.

The test test_splice_rebroadcast_uses_splice_type_after_0conf_promotion (added in this PR) expects TransactionType::Splice with the original contribution preserved, but this code would produce TransactionType::Funding. That test will fail.

A possible fix: check self.funding.channel_transaction_parameters.splice_parent_funding_txid — it is Some(...) for promoted splices and None for initial funding. You'd also need to persist the contribution and replaced_txid metadata somewhere that survives promotion (e.g., on FundingScope or ChannelContext), since pending_splice is cleared.

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Discussed offline. Dropped the commit to retry for now. We may do this later in ChannelMonitor where we'll store the FundingContribution.

@jkczyz jkczyz force-pushed the 2026-04-splice-transaction-type branch from dbaf6d9 to 86dcede Compare April 22, 2026 18:36
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Needs rebase, also ci is very sad.

@jkczyz jkczyz self-assigned this Apr 23, 2026
jkczyz and others added 2 commits April 23, 2026 16:35
`TransactionType::Splice` now carries the local contribution to the
splice and, for RBF, the txid of the prior negotiated candidate being
replaced. This lets LDK Node update its `PaymentDetails` and
`PendingPaymentDetails` from the broadcast callback without re-deriving
the contribution from the raw transaction or tracking RBF chains
itself.

Driving these updates from the `SplicePending` event instead is more
complicated because that event races with BDK wallet syncing and
doesn't carry the replaced txid; the broadcast callback is a cleaner
integration point.

The `Hash` derive on `TransactionType` is dropped since it isn't used
anywhere in the workspace and `FundingContribution` (now embedded)
transitively contains `ConfirmedUtxo`, which doesn't derive `Hash`.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Add public getters for `estimated_fee`, `inputs`, and `max_feerate`, and
elevate `feerate` from `pub(super)` to `pub`. Together with the existing
`value_added`, `outputs`, and `change_output`, this gives downstream
consumers of `TransactionType::Splice` (notably LDK Node, which updates
`PaymentDetails` from the broadcast callback) the data they need
without reaching into the raw transaction.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
@jkczyz jkczyz force-pushed the 2026-04-splice-transaction-type branch from 86dcede to dacf092 Compare April 23, 2026 21:42
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jkczyz commented Apr 23, 2026

Rebased. Compilation failures were from new tests in main.

@jkczyz jkczyz requested a review from TheBlueMatt April 23, 2026 22:17
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codecov Bot commented Apr 23, 2026

Codecov Report

❌ Patch coverage is 52.63158% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.08%. Comparing base (2313bd5) to head (dacf092).

Files with missing lines Patch % Lines
lightning/src/ln/funding.rs 25.00% 9 Missing ⚠️
Additional details and impacted files
@@            Coverage Diff             @@
##             main    #4570      +/-   ##
==========================================
- Coverage   87.08%   87.08%   -0.01%     
==========================================
  Files         161      161              
  Lines      109255   109271      +16     
  Branches   109255   109271      +16     
==========================================
+ Hits        95147    95154       +7     
- Misses      11627    11632       +5     
- Partials     2481     2485       +4     
Flag Coverage Δ
fuzzing-fake-hashes 30.88% <36.84%> (-0.10%) ⬇️
fuzzing-real-hashes 22.66% <0.00%> (+0.01%) ⬆️
tests 86.16% <52.63%> (-0.01%) ⬇️

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