Quickstart

This example registers demo.ping, executes one known binding and prints {"value":"pong"}. Its fake sandbox deliberately ignores the submitted code. It checks registration, validation and cleanup, not JavaScript isolation.

import { Mycelium } from "@fungi.computer/mycelium";
import * as Effect from "effect/Effect";
import * as Stream from "effect/Stream";
import { z } from "zod";

const runtime = await Mycelium.make({
  modules: [
    Mycelium.module({
      id: "example-demo",
      name: "demo",
      operations: {
        ping: Mycelium.operation({
          input: z.object({}),
          output: z.object({ value: z.string() }),
          execute: async () => ({ value: "pong" }),
        }),
      },
    }),
  ],
  sandbox: {
    execute: (request, signal) => {
      signal.throwIfAborted();
      const ping = request.bindings.demo?.ping;
      if (ping === undefined) throw new Error("Missing demo.ping binding");
      return ping({});
    },
  },
});
const lease = await runtime.acquire();
try {
  const prepared = await Effect.runPromise(
    lease.executeTool.prepare({
      type: "toolCall",
      id: "example-execute",
      name: "execute",
      arguments: { code: "return demo.ping({})" },
    }),
  );
  const parts = await Effect.runPromise(Stream.runCollect(prepared.execute()));
  const text = parts[0]?.result.content[0];
  if (text?.type !== "text" || text.text !== '{"value":"pong"}') {
    throw new Error("Unexpected execute result");
  }
  console.log(text.text);
} finally {
  await lease.release();
  await runtime.close();
}

The public-import fixture uses the same known-binding pattern. A real evaluator must implement the public sandbox contract. Its request carries code, execution identity, limits and admitted bindings. Do not replace it with evaluation in the host’s privileged process.