LND Anchor Output Errors - Fix CPFP and Reserve Issues

What Are LND Anchor Output Errors?

Anchor outputs are small 330-sat outputs added to commitment transactions to allow fee bumping via CPFP. Errors occur when LND cannot properly manage these outputs during channel close.

Common Error Messages

• cannot sweep anchor output: not enough wallet funds
• anchor output CSV delay not met
• failed to publish anchor CPFP transaction
• anchor reserve requirement not met

Root Causes

• On-chain wallet balance below anchor reserve (10x num_active_channels * 330 sat)
• CPFP transaction rejected due to low fee rate
• Bitcoin mempool congested, anchor sweep not confirmed in time
• Using legacy (non-anchor) channel type with old peer

Fix: Maintain Anchor Reserve

# Check wallet balance
lncli walletbalance

# Check anchor reserve requirement
lncli getinfo | grep num_active_channels
# Reserve needed: num_active_channels * 10 * 330 sat

# Fund wallet to cover reserve
lncli newaddress p2wkh

Fix: CPFP Fee Bumping

# Bump fee on stuck anchor CPFP tx
lncli wallet bumpfee --sat_per_vbyte 20 <txid>:<output_index>

# Check pending sweeps
lncli pendingchannels

Fix: Channel Type Migration

# Check if channel uses anchors
lncli listchannels | python3 -c "
import json,sys
for c in json.load(sys.stdin)['channels']:
  print(c['chan_id'], c.get('commitment_type','unknown'))
"

# New channels default to anchors in LND 0.15+
# Old channels require cooperative close + reopen

Questions about LND anchor channels? DM on Nostr for help.