Fan-out
Also called fan-in, map-reduce with agents
One job is split into pieces, each goes to its own worker at the same moment, and their results are gathered into one answer, which is the fan-in. The whole job takes as long as the slowest worker, plus the gathering.
It suits reading far better than writing. Ten agents can look through ten modules and report back without touching each other. Ten agents editing the same app cannot.
Say it to your agent
“Use subagents to read each package under src/ and report every place it calls the old auth client, with file and line. One subagent per package. If one fails to report, tell me which, and don't treat it as "nothing found".”