Feedthrough — Debug any web app with AI. From inside.

The name

What's a feedthrough?

Many physics and chemistry experiments run inside a sealed vacuum chamber, with all the air pumped out so nothing contaminates the experiment. The catch: you still need to control instruments inside the chamber and read their measurements, and the smallest air leak ruins the run. A feedthrough is the part that solves this — a specially engineered connector that carries electrical signals through the chamber wall while keeping the vacuum perfectly intact. You can't reach inside, but the feedthrough lets you observe and control what's happening in there anyway.

The parallel is exact. Feedthrough extracts runtime debug data from inside a running web app without disturbing it, and sends control signals back in — clicks, keystrokes, DOM queries — without breaking the execution environment.

Vacuum Chamber

experiment running
signals generated

feedthrough

instruments outside

Your Web App

app state changing
network requests firing

@feedthrough/core

your AI agent

The difference

Embedded, not external

Every other browser MCP tool controls the browser from the outside via Puppeteer or CDP. That means Chrome only, a separate controlled browser, and no access to your app's internals.

✗ External tools (Puppeteer / CDP)

Observer from the outside

Launch a separate browser, drive it remotely, hope the public-facing DOM tells the whole story.

Chrome only
No access to framework internals
Separate browser process required
Doesn't work inside Cypress

✓ Feedthrough

Agent from the inside

Runs in the same JavaScript context as your app, with full access to everything the page knows.

Any browser
React trees, Redux store, custom globals
Your existing dev server — no extra process
Works inside Cypress test runs

Quick start

Up in four steps

No config files, no separate browser to launch.

Add to your MCP client config

// .claude/settings.json (Claude Code example)
{
  "mcpServers": {
    "feedthrough": {
      "command": "npx",
      "args": ["@feedthrough/mcp"]
    }
  }
}

Inject the bridge into your app

Eight first-party adapters — Vite, Next.js, Nuxt, SvelteKit, Remix, webpack, Cypress, Playwright. Pick yours, drop in one line. Dev only, zero cost in production.

Install: npm ↗

// vite.config.ts
import { feedthrough } from "@feedthrough/vite";
defineConfig({ plugins: [feedthrough()] });

// next.config.ts
import { withFeedthrough } from "@feedthrough/nextjs";
export default withFeedthrough()({ /* your next config */ });

// nuxt.config.ts
export default defineNuxtConfig({
  modules: ["@feedthrough/nuxt"],
});

// src/hooks.server.ts
import { feedthroughHandle } from "@feedthrough/sveltekit";
import { sequence } from "@sveltejs/kit/hooks";
export const handle = sequence(feedthroughHandle);

// vite.config.ts
import { feedthrough } from "@feedthrough/remix";
defineConfig({ plugins: [remix(), feedthrough()] });

// webpack.config.mjs
import { FeedthroughPlugin } from "@feedthrough/webpack";
export default { plugins: [new FeedthroughPlugin()] };

// cypress/support/e2e.ts
import { setupFeedthrough } from "@feedthrough/cypress";
setupFeedthrough();

// Import test from the adapter instead of @playwright/test
import { test, expect } from "@feedthrough/playwright";

Open your app in the browser

Once the bridge connects you'll see:

[feedthrough] browser connected

Ask your AI agent what's wrong

> Why is the counter showing the wrong number?

Agent: I'll check the console logs and inspect the element.

  get_console_logs()         → total: 1, 2, 3
  inspect_element("#count")  → textContent: "2, 4, 6"

  State increments by 2 but logs show +1.
  Bug on line 47: setViews(views + 2)

Debug any web app
with AI. From inside.

See it in action

What's a feedthrough?

How it works

Embedded, not external

Observer from the outside

Agent from the inside

Up in four steps

Add to your MCP client config

Inject the bridge into your app

Open your app in the browser

Ask your AI agent what's wrong

Sixteen tools, everything you need

Eight first-party adapters

Debug any web appwith AI. From inside.

See it in action

What's a feedthrough?

How it works

Embedded, not external

Observer from the outside

Agent from the inside

Up in four steps

Add to your MCP client config

Inject the bridge into your app

Open your app in the browser

Ask your AI agent what's wrong

Sixteen tools, everything you need

Eight first-party adapters

Debug any web app
with AI. From inside.