fateA statechart engine for Go

Hierarchical states, parallel regions, and history — with no dependencies beyond the standard library.

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Concepts

GitHub

Statecharts, not flat FSMs

Compound and parallel states, deep and shallow history, guards, actions, and final states. The semantics follow SCXML and XState v5.

Read the concepts

No dependencies

The engine imports only the standard library. The Temporal integration is a separate module, so its SDK is never pulled in unless you ask for it.

Install

Deterministic and persistable

A Machine is immutable and shareable. An Actor serialises to JSON and restores byte for byte, which makes replay exact.

How persistence works

Effects are data

Delayed transitions and invocations are surfaced as pending effects. An adapter performs them, so the engine itself never touches the clock or the network.

The effect model

Runs inside Temporal

Because the engine performs no side effects, a machine can be driven from a workflow and survive replay unchanged.

The Temporal guide

Render and diff

Render any machine to ASCII, Mermaid, or graph JSON, and diff two snapshots from the command line.

The fate CLI