Fix LND Node Issues: 3 Free Diagnostic Scripts

Running a Lightning Network node and hitting mysterious failures? These copy-paste Python scripts helped debug real issues.

1. Graph Staleness Detector

Silent payment failures are often caused by a stale routing graph. Check how old yours is:

import subprocess, json, time
result = subprocess.run(['lncli', 'describegraph'],
    capture_output=True, text=True)
g = json.loads(result.stdout)
edges = g['edges']
if edges:
    latest = max(int(e.get('last_update', 0)) for e in edges)
    lag = int(time.time()) - latest
    print(f'Graph: {len(g["nodes"])} nodes, {len(edges)} edges')
    print(f'Last update: {lag//3600}h {(lag%3600)//60}m ago')
    if lag > 7200:
        print('WARNING: Stale graph — routing is blind')

2. Phantom Liquidity Scanner

Channels that show 'active' but have never processed an HTLC — a known issue in LND 0.17:

import subprocess, json
result = subprocess.run(['lncli', 'listchannels'],
    capture_output=True, text=True)
channels = json.loads(result.stdout)['channels']
dead = [c for c in channels
    if int(c.get('num_updates', '0')) == 0]
print(f'Phantom channels: {len(dead)} / {len(channels)}')
for c in dead[:5]:
    print(f'  {c["chan_id"]} | {c["remote_pubkey"][:20]}...')

3. Fee Optimization Check

Channels with high local balance ratio are providing cheap liquidity — you may be undercharging:

import subprocess, json
result = subprocess.run(['lncli', 'listchannels'],
    capture_output=True, text=True)
for ch in json.loads(result.stdout)['channels']:
    cap = int(ch['capacity'])
    if cap < 500_000:
        continue
    ratio = int(ch['local_balance']) / cap
    if ratio > 0.7:
        print(f'Undercharging: {ratio:.0%} local on {ch["chan_id"][:8]}')
        print(f'  Peer: {ch["remote_pubkey"][:20]}...')

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