State Machine

Conclusion first: the value of multi-agent doesn’t come from more models; it comes from the right structure. Multi-agent without structure is just more expensive concurrency — burn 2 to 3 times the tokens to watch a group of models nod at each other. Multi-agent with structure is an execution system that can delegate, parallelize, and verify. Why a Single Agent Fails at Long Tasks # Diagnosis first. A single agent executing complex tasks has five structural defects — blame the execution structure, not the model’s intelligence:

Autoregressive large language models operating in unconstrained environments suffer from an inherent tendency toward myopic mutation and runaway divergence. Claude Code’s Plan Mode attaches an external discrete Finite State Machine (FSM) that projects the action space onto a strictly side-effect-free subset, using an interactive human barrier to prune catastrophic physical backtracking branches from the decision tree. In disciplined software engineering, experienced developers instinctively value structural planning: mapping dependency graphs, deriving type signatures, and scoping blast radiuses before modifying a single line of code. Large language models possess no such innate restraint. Shaped by reinforcement learning to generate immediate answers, an agent granted unrestrained write permissions will instinctively mutate files without global context, precipitating an architectural cascade across complex repositories.