Electrum’s recent patch resolves a Lightning backup issue, yet certain Bitcoin wallet holders must still renew their backups.
Backups created from wallets using non‑deterministic Lightning keys miss the data required to recover funds from anchor channels after the counterparty closes the channel.
Release 4.8.2, issued on September 11, continues to be the most recent version posted on Electrum’s site as of October 1.
The fix for individual backups inserts the missing payment key, allowing users to claim their balance from an anchor channel closed by the remote party. Without this key, the backup cannot sweep the on‑chain output and thus cannot retrieve the associated bitcoin.
Which Wallets Require Action?
According to the release notes, the issue arises only when both of the following are true: the wallet employs non‑deterministic Lightning keys, and the backup pertains to an anchor channel.
Non‑deterministic keys cannot be regenerated from the wallet seed. The alert applies to both single‑channel exports and full‑wallet backups that involve Lightning recovery.
Wallets that derive Lightning keys from a BIP39 seed or an imported extended private key (xprv) invariably use non‑deterministic keys. By contrast, Electrum‑seed wallets obtain deterministic Lightning keys only if the wallet file was created with version 4.1 or later; files from the 4.0.x series remain non‑deterministic even when run with newer software.
On the desktop client, the wallet interface flags Lightning channels as unrecoverable from the seed, and the Android channel‑opening dialog shows a similar warning. The defect only manifests when an anchor channel is involved.
The individual‑backup patch also removes the ability to request a remote force‑close when the backup lacks the data to sweep the resulting output, preventing a closure that could not be claimed.
Pull request 10851 amends wallet‑file exports by preserving a randomly generated Lightning private key that was formerly stripped away. Maintainer SomberNight notes that re‑activating Lightning in such a backup would produce new keys, rendering the existing channel‑backup data inadequate for spending anchor‑channel funds.
Updating the software alters how backups are generated and interpreted; consequently, Electrum’s prescribed fix calls for fresh exports, and impacted wallets will show a startup alert.
Performing the replacement hinges on preserving the original wallet data necessary for a new export; merely installing a newer version does not restore keys that have already been lost.
