Splice Interop

[ddustin]

A collection of fixes for interop with Eclair.

• Clearer logging of splice flow errors.
• Allowing channel_ready messages to occur during splice reestablish flow.
• Fixing of splice related RPC user shown errors code -- they could come from multiple places and cause a crash if they do.
• Implement the triggering of the sending of announcement signatures if requested by new reestablish TLVs.

[t-bast]

Implement the triggering of the sending of announcement signatures if requested by new reestablish TLVs.

I believe you've introduced a new bug in your fix. I've tested the following flow:

• eclair and cln have a confirmed channel
• eclair creates a splice that confirms and ignores cln's announcement_signatures
• I restart the eclair node: on reconnection, it asks for a retransmission of announcement_signatures, which cln correctly retransmits (so I initially thought that this was fixed)
• But if I ignore it again and reconnect a second time (with exactly the same channel_reestablish where eclair asks again for retransmission of announcement_signatures), now cln sends an error and force-closes

Here is the log of the force-close:

2026-01-09T11:08:21.071Z **BROKEN** 0375124ab04a67a5d074833dce3197f733fec624e2200e9bd69e52bbeb5d980a98-chan#1: Internal error CHANNELD_NORMAL: bad channeld_reestablished 044d01
2026-01-09T11:08:21.071Z UNUSUAL 0375124ab04a67a5d074833dce3197f733fec624e2200e9bd69e52bbeb5d980a98-chan#1: Peer permanent failure in CHANNELD_NORMAL: Internal error (reason=local)
2026-01-09T11:08:21.071Z INFO    0375124ab04a67a5d074833dce3197f733fec624e2200e9bd69e52bbeb5d980a98-chan#1: State changed from CHANNELD_NORMAL to AWAITING_UNILATERAL

If you want to reproduce, you can use this custom eclair branch that ignores splice announcement_signatures: https://github.com/ACINQ/eclair/tree/splicing-official-cross-compat-annsigs-retransmit

Allowing channel_ready messages to occur during splice reestablish flow.

This one doesn't seem to be fixed. I still get the following error on reconnection:

Got incorrect message from peer: WIRE_CHANNEL_READY (should be WIRE_COMMITMENT_SIGNED or WIRE_TX_SIGNATURES or WIRE_TX_ABORT of WIRE_CHANNEL_READY) [Invalid ERROR message '0024907bcacf3f172c362443bbbc194d490cdfcf89f4693f8cf2da5a2825e8c9d0600397c01f3c5b332421ce9a8a4f31850eed46837c0e459f3f18af4fc7586b7963090108038bd74d261c9a5b']

Steps to reproduce:

• use this branch of eclair, which will stop splicing before exchanging commit_sig: https://github.com/ACINQ/eclair/tree/splicing-official-cross-compat-abort-reconnect
• open a channel between eclair and cln (in my test, opened by eclair with eclair-cli open --nodeId=<cln_node_id> --fundingSatoshis=300000 --fundingFeeBudgetSatoshis=10000 --channelType=anchor_outputs_zero_fee_htlc_tx)
• wait for the channel to be confirmed
• initiate a splice from eclair: eclair-cli splicein --channelId=<channel_id> --amountIn=100000
• restart the eclair node: the logs will show this failure and the tx_abort isn't processed