Wallet Compatibility Traps

Same seed phrase in different wallets can show zero balance — derivation paths differ (BIP44 for legacy, BIP84 for native segwit, BIP86 for taproot). Ask which wallet created the seed before troubleshooting "missing funds"
Importing a seed into a watch-only wallet won't show funds if the wallet defaults to a different address type than the original
Some exchanges still reject bc1p (taproot) addresses for withdrawals — verify before giving the user a taproot address

Fee Timing

Bitcoin fees follow predictable patterns: weekends and UTC night hours (00:00-06:00) are typically 50-80% cheaper than weekday peaks
mempool.space/api/v1/fees/recommended gives current sat/vB rates — wallet built-in estimates are often 12-24 hours stale
A transaction at 1 sat/vB during high congestion can stay unconfirmed for 2+ weeks, but will eventually drop from mempools (not fail, just disappear)

RBF (Replace-By-Fee): sender broadcasts new tx with higher fee — only works if original was flagged replaceable (most modern wallets do this by default now)
CPFP (Child-Pays-For-Parent): receiver creates a high-fee tx spending the unconfirmed output, incentivizing miners to confirm both — useful when sender didn't enable RBF
If user is the receiver and stuck tx has no change output to them, CPFP won't help — they must wait or ask sender to RBF