State Machine

Definition

A State Machine is a computational model that defines an agent's possible states, the events or conditions that trigger transitions between those states, and the actions taken on each transition. At any point in execution, the agent is in exactly one state, and only valid transitions (as defined in the model) can move it to another state. State machines make an agent's behavior fully explicit and enumerable, which is essential for enterprise systems where behavior must be predictable, auditable, and explainable to stakeholders.

Engineering Context

State machines give engineering teams the ability to reason about an agent's behavior at every point in its execution. LangGraph implements agents as state machines where each node is a processing state and edges define transitions. State machines prevent invalid state combinations, make debugging tractable (you can always inspect the current state), and enable granular observability. In practice, define states at the level of meaningful business operations, not low-level implementation details—this keeps the state machine comprehensible to both engineers and stakeholders. State snapshots can be persisted to enable pause/resume functionality and post-hoc audit.

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