@effect-state-machine/studio-client

Connects running effect-state-machine machines to Studio, the standalone devtool.

Install

pnpm add @effect-state-machine/studio-client

effect and effect-state-machine are peer dependencies.

Attach a running machine

import { Attach, Transport, WebSocketTransport } from "@effect-state-machine/studio-client"
import * as Effect from "effect/Effect"
import * as MachineEngine from "effect-state-machine/MachineEngine"

const program = Effect.scoped(
  Effect.gen(function* () {
    const handle = yield* definition.run(input)
    yield* Attach.attach({
      definition,
      handle,
      quickEvents: [{ id: "save", label: "Save", event: { _tag: "Save" } }],
    })
    // …the application continues normally
  }),
).pipe(
  Effect.provide(MachineEngine.layerMemory()),
  Effect.provideService(Transport.StudioTransport, WebSocketTransport.make()),
)

Attaching is scoped and observational: it never interrupts the machine, and it is inert when no Studio is running — the client connects lazily, retries in the background, and buffers unsent facts (bounded, oldest dropped with a truncation notice). One attachment represents the root machine and every child machine it owns as a single ordered Studio session.

The transport is a swappable Effect service (StudioTransport): WebSocketTransport reaches a local Studio server, and an in-memory pair ships for tests and embedded use.

For a runnable walkthrough see examples/checkout-demo.ts.