Less theory.
More working code.

1import { Engine, Workflow } from "@newvexa/workify";
2
3export function createWorkflowEngine() {
4  const workflow = new Workflow({ id: "demo", name: "Double a number" });
5
6  workflow.addNode({
7    id: "start",
8    name: "Receive input",
9    type: "trigger",
10    async execute(input) {
11      return { outputs: { main: input.initial } };
12    },
13  });
14
15  workflow.addNode({
16    id: "double",
17    name: "Double the value",
18    type: "action",
19    async execute(input, context) {
20      context.signal.throwIfAborted();
21      const value = input.incoming[0]?.value;
22      if (typeof value !== "number") throw new Error("Expected a number");
23      return { outputs: { main: value * 2 } };
24    },
25  });
26
27  workflow.addLink({
28    id: "start-double",
29    name: "Input to calculation",
30    source: { nodeId: "start", port: "main" },
31    target: { nodeId: "double", port: "main" },
32  });
33
34  return new Engine(workflow, { concurrency: 4, historyLimit: 500 });
35}