Let agents and tests reach into your running app — without shipping a debug menu

Appduct lets a terminal, a test runner, or an AI agent call functions inside your React Native app while it's running. You pick what's callable — a few functions you write yourself — and nothing else is reachable.

Why you'd want this

Your E2E tests stop tapping through setup. Most of an end-to-end test isn't the thing you're testing. It's logging in, dismissing onboarding, seeding a cart, waiting for a spinner. With Appduct, the test calls login(userId) or seedCart(items) directly and jumps straight to the part that matters. Faster runs, far less flakiness, and a lot fewer screenshots for an agent to burn tokens on.

Agents can actually drive your app. Add one line to Claude Code's or Cursor's config and your app's functions show up as tools the agent can call. It can flip a feature flag, jump to a screen, or check some state without you wiring up a single prompt.

No hidden debug UI. No secret gestures, no long-press-the-logo admin panel, nothing extra in the app for someone to go find. The only things reachable are functions you deliberately registered.

Nothing ships in your release build by default. Appduct is included in debug builds only — a release build compiles it out entirely, not just switches it off. Want it in a TestFlight or other internal build too? You can opt in per build — see Build variants.

Your dev loop doesn't fight you. Metro reloads, backgrounding the app, flaky Wi-Fi — the session survives all of it and picks back up on its own. One background service handles as many devices as you've got plugged in.

What it looks like

Register something you want reachable:

import { useAppductTool } from "@appduct/react-native";
import { z } from "zod";

useAppductTool({
  name: "seed_cart",
  description: "Fill the cart with test items.",
  inputSchema: z.object({ items: z.number() }),
  handler: async ({ items }) => ({ added: items }),
});

The hook registers once per mount — re-rendering costs nothing, and the handler always sees the latest state it closes over.

Call it from your terminal:

appduct invoke seed_cart --input '{"items":3}'

Or hand it to an agent — see Use it with an agent. The CLI and the MCP server both read your app's deep-link scheme straight from app.json's expo.scheme, so there's nothing to configure.

That's the whole idea. Everything else is about which builds include it and what they trust.

Is this safe to ship?

By default, yes — nothing here ships in a release build, so there's no code on the device to attack in the first place. If you opt into carrying Appduct in a build that reaches people outside your team (see Build variants), the connection is still encrypted, your app checks the identity of the machine on the other end rather than trusting whoever's on the network, and a link someone intercepts isn't a way in.

docs/SECURITY.md walks through what it protects against, what it doesn't, and how to configure and rotate keys for that case.

Getting started

Install the CLI where you'll run it, and the package in your app:

npm install -g appduct
npm install @appduct/react-native zod

From there:

• Set up your app — registering tools, deep-link setup, and the API reference.
• Use the CLI and MCP server — connecting to a device, listing and calling tools, and checking a built artifact.
• Try the playground — a working app you can run end to end in a few minutes. Fastest way to see whether this fits your project.

You'll need a development build or a bare React Native app — Expo Go can't do it.

Use it with an agent

There are two ways to connect an agent. Pick whichever fits how your agent works.

Over MCP. Add Appduct to your agent's MCP config — Claude Code, Cursor, or any other MCP client. Your app's tools show up next to the agent's own, and the connection tools explain themselves, so there's nothing else to install:

{
  "mcpServers": {
    "appduct": { "command": "appduct", "args": ["mcp"] }
  }
}

Through the CLI. For agents that work in a shell, and for scripts or CI. Install the Appduct skill so the agent knows the commands:

npx skills add callstackincubator/appduct --skill appduct

Asking an agent to add Appduct to your app or write its tools? Install the skill either way — it covers setup and the rules your tool schemas have to follow.

Packages

Package	What it is
appduct	The CLI, the background service, and the MCP server
@appduct/react-native	The app-side library and Expo config plugin
@appduct/shared	Types shared by both

Support

React Native apps on iOS 15.1+ and Android, both on the New Architecture. Web gets a no-op stub so shared code doesn't break. The CLI needs Node 20 or newer. Windows should work but hasn't been verified yet.

Docs

• docs/SECURITY.md — what it protects against, configuring trust, and key rotation
• docs/BUILD-VARIANTS.md — which builds carry Appduct, and how to compile it out
• docs/ARCHITECTURE.md — how the pieces fit together
• docs/PROTOCOL.md — the wire protocol, if you're implementing a client
• docs/CI.md — running it in CI, and the appduct doctor release gate

Made with ❤️ at Callstack

appduct is an open source project and will always remain free to use. If you think it's cool, please star it 🌟. Callstack is a group of React and React Native geeks, contact us at hello@callstack.com if you need any help with these or just want to say hi!

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