@mastra/quickjs

QuickJsCodeModeTransport runs model-authored Code Mode programs in a QuickJS runtime compiled to WebAssembly. Use it when native addons or Node.js startup flags are unavailable, such as in serverless environments, while keeping execution isolated from the host process.

Installation

npm install @mastra/quickjs

Usage

import { Agent } from '@mastra/core/agent';
import { createCodeMode, createTool } from '@mastra/core/tools';
import { QuickJsCodeModeTransport } from '@mastra/quickjs';
import { z } from 'zod';

const getPrice = createTool({
  id: 'getPrice',
  description: 'Get the price of a product',
  inputSchema: z.object({ productId: z.string() }),
  outputSchema: z.object({ price: z.number() }),
  execute: async ({ productId }) => ({ price: productId === 'pro' ? 49 : 19 }),
});

const { tool, instructions } = createCodeMode(
  { tools: { getPrice } },
  new QuickJsCodeModeTransport({ memoryLimitMb: 128 }),
);

const agent = new Agent({
  id: 'pricing-agent',
  name: 'Pricing agent',
  instructions: ['Answer pricing questions.', instructions],
  model: 'openai/gpt-5.6-sol',
  tools: { execute_typescript: tool },
});

Documentation

• Code Mode guide
• QuickJsCodeModeTransport reference

Changelog

See the package changelog for version history and release notes.

Support

We have an open community Discord. Come and say hello and let us know if you have any questions or need any help getting things running.