Error propagation (multi-agent)

Error propagation is the process by which one agent’s error is passed downstream as trusted input to the agents that act after it, so a single local mistake compounds across the system rather than staying at its source. Two shapes matter. Along a sequential chain the error deepens: every stage builds on the corrupted state it inherits, and the output drifts further from correct with each hop. Across a fan-out it widens: one bad result is consumed in parallel by many peers, correlating their failures at once.

Propagation depth, the number of successive hops an error survives before a check catches it, is the measure that turns this from anecdote into a quantity you can bound. It also fixes the term’s place among its neighbors: propagation is the mechanism, blast radius is the reach that mechanism achieves on a given run, and cascade resistance is the wiring’s standing tendency to damp or amplify that reach. The multi-agent failure-mode taxonomy maps which failures propagate and which stay put.