Documentation Index
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import {
WorkflowKit,
type WorkflowEngine,
type WorkflowKitOptions,
type WorldConfig,
type WorldRunHandle,
} from "@ai_kit/core";
WorkflowKit selects the workflow engine and exposes a unified lifecycle. The default engine is legacy (the in-memory engine); world runs on the Vercel Workflow SDK with a durable Postgres/MongoDB backend (requires the optional @ai_kit/workflow-world package).
WorkflowKitOptions
| Property | Type | Default | Description |
|---|
engine | "legacy" | "world" | "legacy" | Engine used by default for run. |
world | WorldConfig | undefined | World backend config. Required when engine === "world". |
WorldConfig
| Property | Type | Default | Description |
|---|
type | "postgres" | "mongodb" | required | World backend. mongodb is experimental. |
url | string | required | Connection string (postgres:// / mongodb://). |
jobPrefix | string | undefined | Postgres: namespace jobs on a shared database. |
workerConcurrency | number | SDK default | Postgres: concurrent workers (maps to queueConcurrency). |
maxPoolSize | number | SDK default | Postgres: connection pool size. |
Construction
const kit = new WorkflowKit({
engine: "world",
world: { type: "postgres", url: process.env.WORKFLOW_POSTGRES_URL! },
});
engine: "world" without a world config throws.- An unknown
world.type throws.
engine: "legacy" with a world config is allowed (lets you toggle engines via an env var without rewriting config).
Properties
| Property | Type | Description |
|---|
engine | WorkflowEngine | The configured default engine (read-only). |
world | WorldConfig | undefined | The world config, if any (read-only). |
Methods
start()
Starts the durable world worker (lazily loading @ai_kit/workflow-world and creating the adapter). No-op when engine === "legacy", so the same lifecycle code works for both engines. Throws a clear error if @ai_kit/workflow-world is not installed.
stop()
Gracefully stops the world worker. No-op when engine === "legacy" or when the world was never started.
Dispatches to the configured engine (overridable per call via dispatch.engine).
// Legacy overload — workflow is an AI Kit Workflow
run<Output>(
workflow: Workflow<any, Output>,
options: WorkflowRunOptions,
dispatch?: { engine?: WorkflowEngine },
): Promise<WorkflowRunResult<Output>>;
// World overload — workflow is a "use workflow" function, input is the args array
run(
workflow: (...args: any[]) => unknown,
args: unknown[],
dispatch?: { engine?: WorkflowEngine },
): Promise<WorldRunHandle>;
legacy → delegates to Workflow.run(options) and returns a WorkflowRunResult.world → delegates to the SDK’s start(fn, args) and returns a WorldRunHandle.
WorldRunHandle
The opaque handle returned by a world run (pass-through of the SDK Run):
| Property | Type | Description |
|---|
runId | string | Identifier of the durable run. |
Example
import { WorkflowKit } from "@ai_kit/core";
// One config, switchable via env — legacy locally, world in production
export const kit = new WorkflowKit({
engine: (process.env.WORKFLOW_ENGINE as "legacy" | "world") ?? "legacy",
world: { type: "postgres", url: process.env.WORKFLOW_POSTGRES_URL ?? "" },
});
await kit.start(); // no-op on legacy
const handle = await kit.run(myWorkflow, ["arg"]);
await kit.stop();