Lightning Routing Lightning is a source-routed network: the sender computes the full path through intermediaries and constructs the onion accordingly. Each hop sees only its forwarding instructions, not the full route. Channel graph Built from + gossip: Each edge has TWO directions, each with potentially different fees and CLTV deltas. Cost function Standard scoring (LND, CLN, LDK): (apriori probability of success) often defaults to 95% for unknown edges, decreasing with recent failures. Pathfinder: Dijkstra or Yen's k-shortest-paths over the cost function. Multi-Path Payments (MPP) Split a p…