f - Document stale min_rbf_feerate when in-progress negotiation fails

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: jkczyz

lightning/src/ln/channel.rs

@@ -11968,7 +11968,9 @@ where
 			//   feerate requirement. Derive the minimum RBF feerate from the negotiation's
 			//   feerate so the user can choose an appropriate feerate.
 			// - If the negotiation fails (e.g., tx_abort), the splice will proceed as a fresh
-			//   splice instead.
+			//   splice instead. In this case, the min_rbf_feerate becomes stale, causing a
+			//   slightly higher feerate than necessary. Call splice_channel again after
+			//   receiving SpliceFailed to get a fresh template without the RBF constraint.
 			let prev_feerate = negotiation.funding_feerate_sat_per_1000_weight();
 			let min_feerate_kwu = ((prev_feerate as u64) * 25).div_ceil(24);
 			(Some(FeeRate::from_sat_per_kwu(min_feerate_kwu)), None)

lightning/src/ln/channelmanager.rs

@@ -6526,7 +6526,10 @@ impl<
 	///
 	/// If any failures occur while negotiating the funding transaction, an [`Event::SpliceFailed`]
 	/// will be emitted. Any contributed inputs no longer used will be included in an
-	/// [`Event::DiscardFunding`] and thus can be re-spent.
+	/// [`Event::DiscardFunding`] and thus can be re-spent. If a [`FundingTemplate`] was obtained
+	/// while a previous splice was still being negotiated, its
+	/// [`min_rbf_feerate`][FundingTemplate::min_rbf_feerate] may be stale after the failure.
+	/// Call this method again to get a fresh template.
 	///
 	/// After initial signatures have been exchanged, [`Event::FundingTransactionReadyForSigning`]
 	/// will be generated and [`ChannelManager::funding_transaction_signed`] should be called.