AMP / MPP
Also: Atomic Multipath Payments, Multi-Part Payments
lightning · advanced
Splitting a Lightning payment across multiple routes simultaneously. Lets you pay more than any single channel can route.
A Lightning channel's maximum payment size is bounded by its current liquidity. If you have 5 channels with 0.01 BTC of outbound each and want to send 0.04 BTC, no single channel can carry it. MPP/AMP splits the payment into multiple HTLCs across multiple routes, then reassembles atomically: either all parts settle or none do.
MPP (BOLT-4 amendment, 2020) splits a single invoice across paths but settles via one shared preimage. Every part has the same payment hash; the receiver claims them all at once. AMP (proposed but less adopted) goes further — the receiver derives a fresh hash per part, allowing repeat payments to the same "address" without reusing the invoice.
MPP dramatically improved Lightning's effective payment size. In practice, wallets now routinely split anything above a few thousand sats across 2–4 paths, regardless of whether a single-path route exists.