AI SDK - Pi Harness

HarnessV1 adapter backed by @earendil-works/pi-coding-agent. Pi runs in the host Node.js process and uses the sandbox as a remote filesystem + shell — no bridge process is installed inside the sandbox.

Setup

npm i @ai-sdk/harness-pi @ai-sdk/harness @ai-sdk/sandbox-vercel

Usage

import { HarnessAgent } from '@ai-sdk/harness/agent';
import { createPi } from '@ai-sdk/harness-pi';
import { createVercelSandbox } from '@ai-sdk/sandbox-vercel';
import { tool } from 'ai';
import { z } from 'zod/v4';

const agent = new HarnessAgent({
  harness: createPi({ thinkingLevel: 'medium' }),
  id: 'demo',
  sandbox: createVercelSandbox({ runtime: 'node24' }),
  skills: [
    {
      name: 'careful-refactors',
      description: 'Make minimal diffs and keep tests green.',
      content: 'Prefer changes that touch the fewest files possible.',
    },
  ],
  tools: {
    deploy: tool({
      description: 'Deploy a service.',
      inputSchema: z.object({ env: z.enum(['staging', 'production']) }),
      execute: async ({ env }) => ({ url: `https://${env}.example.com` }),
    }),
  },
});

const session = await agent.createSession();
try {
  const result = await agent.generate({
    session,
    prompt: 'Read README.md and summarise the goals.',
  });
  console.log(result.text);
} finally {
  await session.destroy();
}

The adapter requires a HarnessV1SandboxProvider. Pi has no in-sandbox bridge, so the sandbox doesn't need to expose any ports — @ai-sdk/sandbox-vercel or @ai-sdk/sandbox-just-bash both work.

Inline extensions

Use extensionFactories to load trusted inline Pi extensions for each harness session:

import { createPi } from '@ai-sdk/harness-pi';

const harness = createPi({
  extensionFactories: [
    pi => {
      pi.on('agent_start', () => {
        console.log('Pi agent started');
      });
    },
  ],
});

Routine resource refreshes between turns do not reinitialize extension factories. If the underlying Pi session is rebuilt, factories initialize for the new Pi runtime. Extension factories execute in the host Node.js process, so only pass factories you trust. This option does not enable filesystem extension discovery: user, project, personal, and settings-based Pi extensions remain disabled. Themes and prompt templates also remain disabled.