Eclair Channel Force-Close Errors: Debug and Fix

When Eclair force-closes a channel unexpectedly, funds are locked for days. Here is how to diagnose and prevent it.

Common Causes

1. HTLC timeout — remote peer not settling payments on time
2. Fee rate mismatch — commitment tx fee too low for mempool
3. Stale channel state — outdated backup restored
4. Peer offline too long — Eclair closes after inactivity threshold

Diagnosis

eclair-cli channels | jq '.[] | select(.state=="CLOSING")'
eclair-cli channel --channelId <id>
eclair-cli closedchannels

Fix: Fee Rate Issues

# eclair.conf
eclair.on-chain-fees.closing-feerate-sat-byte = 10

Fix: HTLC Timeout

eclair.channel.htlc-timeout-blocks = 144

Recovery After Force-Close

1. Wait for CSV delay (144 blocks default)
2. Run: eclair-cli getrecoveredchannels
3. Sweep: eclair-cli cpfp --outpoint <txid:vout>

Prevention

Keep peers online, monitor mempool fees, set conservative max-accepted-htlcs, enable require-confirmed-inputs-for-dual-funding. Force-close is last resort — most issues resolve with peer reconnect.