[BUG] Funds from force-closed Lightning channel not swept after Electrum Mobile crash

[MarcosBarceloPerez]

Hello,

I would like to report what appears to be a bug related to Lightning channel recovery and force-closed channels in Electrum Mobile.

Here is what happened:

1. I recently created a wallet in Sparrow Wallet and imported it into Electrum Mobile using the BIP84 extended private master key (xprv).

2. I deposited approximately €100 worth of Bitcoin into the wallet and decided to open a Lightning channel with the Electrum Trampoline service to test Lightning functionality.

3. I saved the Base64 channel backup provided by Electrum.

4. Unfortunately, I later lost the application data from Electrum Mobile. I restored my wallet by importing the extended master private key again and also restored the Lightning channel using the Base64 channel backup.

5. Since Electrum no longer had information about the latest state of the Lightning channel, I decided to request a remote force-close of the channel.

6. The force-close was successfully executed, and the channel funds were sent to the following Bitcoin address:

bc1q89a5ynlqlyg07ps32d8sgrygtlcpm9ggsh5f2ex35qlmzrqwt4dqj6xl75

The corresponding transaction is:

b9017a5a826af5a2b9c09d545516ce23a78760a84d229cf0e324f116cc68b7c3

7. As far as I understand, after the force-close and once the CSV timelock expired, Electrum should have detected the relevant output and created a sweep transaction to move the funds back into the wallet.

However, Electrum Mobile suddenly crashed. After restarting the application, the Lightning channel and its history had disappeared. The only Lightning transaction that had previously appeared in the history was the channel closure. No sweep transaction was ever created.

I then tried importing the Base64 channel backup again. The channel briefly appears in Electrum, but then disappears again. I assume this may be because the channel has already been closed. I have observed the same behavior when trying to restore the channel using Electrum Desktop.

At this point, I am unable to recover the funds from the force-closed channel. It appears that Electrum did not perform the expected sweep transaction, and I can no longer access the channel information through the user interface.

This seems to indicate a potential bug in the handling of force-closed Lightning channels after restoring a wallet/channel backup, particularly when the application loses the latest channel state or crashes during the recovery process.

Could you please investigate whether this is a known bug or an issue with Electrum's Lightning channel recovery logic?

I would also appreciate guidance on how I can recover these funds manually. Since I still have the original BIP84 extended private master key and the Base64 Lightning channel backup, I would like to know whether the funds can be recovered using these backups, and if there is a way to manually trigger or construct the required sweep transaction.

Relevant information:

• Force-close transaction: b9017a5a826af5a2b9c09d545516ce23a78760a84d229cf0e324f116cc68b7c3
• Force-close output address: bc1q89a5ynlqlyg07ps32d8sgrygtlcpm9ggsh5f2ex35qlmzrqwt4dqj6xl75
• Wallet type: BIP84
• Original wallet created/imported from Sparrow Wallet
• Electrum Mobile: Lightning channel restored from Base64 channel backup
• Electrum Desktop: Same channel recovery issue observed
• Issue: Force-closed channel funds were never swept after the channel closure, and the channel/history subsequently disappeared from Electrum Mobile after a crash.

Please let me know if you need any additional logs, debug information, wallet files, or other details to reproduce and investigate the issue.

Thank you for your help.

[SomberNight]

@accumulator too eager bot closed this accidentally?

[SomberNight]

@accumulator please fix the bot, it should remember that it already closed an issue once and not close it a second time if the same issue is open again. Leaving the issue "closed" until then as I guess reopening it would trigger the bot again.

[SomberNight]

@MarcosBarceloPerez what version of Electrum? latest release?

Electrum Desktop: Same channel recovery issue observed

If you can restore from xprv and import the channel backup on desktop, and the funds are still not swept there, it would be good to get debug logs from that. Much easier to get logs on desktop than on Android. Ideally logs from the session where you import the channel backup would be best.

Logs should be safe to share security-wise, but can be somewhat privacy-sensitive. If you want you can send me the logfile in email, or just upload it here (in which case others can also try to debug).