dev-inspector-mcp

The missing runtime context for AI coding agents.

AI can read your code, but can't see what's happening at runtime. DevInspector provides the missing context: source code location, DOM state, styles, network, console, terminal output, and screenshots.

Two modes: Use with your IDE's AI (Cursor, VSCode) via MCP, or run AI agents directly in the browser via ACP (Claude Code, Codex CLI, Gemini CLI, OpenCode, more).

Using Claude Code or another AI agent? Install the DevInspector skill so your agent knows how to set up and troubleshoot the inspector:

npx skills add mcpc-tech/dev-inspector-mcp

Table of Contents

• Demo Video
• Social Media
• Key Features
• Quick Start
  • Installation
  • Automated Setup
  • Framework Setup
• Agent Skills
• Configuration
  • Auto-Update MCP Config
  • Agent Installation
  • Custom Agents
  • MCP Servers Configuration
• What It Does
• Two Workflow Modes
• MCP Tools
• Custom Inspector Tools
• MCP Prompts
• Architecture

Demo Video

Watch the demo: https://www.youtube.com/shorts/TCt2oOtPS_k

Social Media

Twittter/X Post: https://x.com/yaoandyan/status/1995082020431753600

Key Features

Visual Context & Region Selection

Click any element to inspect it, or drag to select a region. AI gets the full context: source code location, computed styles, component hierarchy, IDs, classes, text content, and automatically captures screenshots for pixel-perfect visual understanding.

Page Overview & Accessibility Tree

get_page_info provides AI with a semantic understanding of the page: URL, viewport, and an accessibility tree showing landmarks, headings, forms, and links. AI can navigate the page structure without screenshots.

Universal DevTools Access

AI can access Network and Console logs from any browser (via client-side interception) or full Chrome DevTools (via chrome devtools mcp). It sees what you see, regardless of your environment.

Multi-Agent Workflow

Switch between agents (Claude Code, Codex, Gemini, Opencode...) and track their debugging progress visually with a floating status bar.

Quick Start

Installation

# npm - basic installation
npm i -D @mcpc-tech/unplugin-dev-inspector-mcp

# pnpm - basic installation
pnpm add -D @mcpc-tech/unplugin-dev-inspector-mcp

# yarn - basic installation
yarn add -D @mcpc-tech/unplugin-dev-inspector-mcp

Note: If you don't need the ACP agents (Inspector Bar mode), add --no-optional to skip installing agent packages:

npm i -D @mcpc-tech/unplugin-dev-inspector-mcp --no-optional
pnpm add -D @mcpc-tech/unplugin-dev-inspector-mcp --no-optional
yarn add -D @mcpc-tech/unplugin-dev-inspector-mcp --no-optional

Automated Setup (Recommended)

Run the setup command to automatically configure your vite.config.ts, webpack.config.js, or next.config.ts:

npx @mcpc-tech/unplugin-dev-inspector-mcp setup

Options:

• --dry-run - Preview changes without applying them
• --config <path> - Specify config file path (auto-detect by default)
• --bundler <type> - Specify bundler type: vite, webpack, nextjs
• --no-backup - Skip creating backup files
• --help - Show help message

Examples:

# Preview changes before applying
npx @mcpc-tech/unplugin-dev-inspector-mcp setup --dry-run

# Setup specific config file
npx @mcpc-tech/unplugin-dev-inspector-mcp setup --config vite.config.ts

# Setup for specific bundler
npx @mcpc-tech/unplugin-dev-inspector-mcp setup --bundler vite

This will:

• Detect your bundler configuration
• Add the necessary import
• Add the plugin to your configuration
• Create a backup of your config file

Framework Setup

Pick your framework below. Each section is self-contained -- just copy the config.

// vite.config.ts
import DevInspector from '@mcpc-tech/unplugin-dev-inspector-mcp';
import react from '@vitejs/plugin-react'; // or vue(), svelte(), solid(), preact()

export default {
  plugins: [
    DevInspector.vite({ enabled: true }),
    react(),
  ],
};

Plugin order matters: Place DevInspector.vite() before framework plugins. Otherwise source locations may show unknown:0:0.

Step 1 -- next.config.ts:

import DevInspector, { turbopackDevInspector } from '@mcpc-tech/unplugin-dev-inspector-mcp';

const nextConfig = {
  webpack: (config) => {
    config.plugins.push(DevInspector.webpack({ enabled: true }));
    return config;
  },
  turbopack: {
    rules: turbopackDevInspector({ enabled: true }),
  },
};

export default nextConfig;

Step 2 -- app/layout.tsx (required):

import { DevInspector } from "@mcpc-tech/unplugin-dev-inspector-mcp/next";

export default function RootLayout({ children }) {
  return (
    <html>
      <body>
        <DevInspector />
        {children}
      </body>
    </html>
  );
}

Run with next dev (webpack) or next dev --turbopack (turbopack).

// vite.config.ts
import { reactRouter } from "@react-router/dev/vite";
import DevInspector from '@mcpc-tech/unplugin-dev-inspector-mcp';

export default defineConfig({
  plugins: [
    DevInspector.vite({ enabled: true, entry: "app/root.tsx" }),
    reactRouter(),
  ],
});

// webpack.config.js
const DevInspector = require('@mcpc-tech/unplugin-dev-inspector-mcp');

module.exports = {
  plugins: [
    DevInspector.webpack({ enabled: true }),
  ],
};

Non-HTML Projects (Miniapps, Library Bundles)

DevInspector.vite({
  enabled: true,
  autoInject: false,
  entry: 'src/main.ts',
})

TypeScript Types

If you import virtual:dev-inspector-mcp, add to your tsconfig:

{
  "compilerOptions": {
    "types": ["vite/client", "@mcpc-tech/unplugin-dev-inspector-mcp/client"]
  }
}

Custom Virtual Module Name

DevInspector.vite({
  enabled: true,
  autoInject: false,
  virtualModuleName: 'virtual:my-custom-inspector',
})

Disable Chrome DevTools

Set disableChrome: true in plugin options or DEV_INSPECTOR_DISABLE_CHROME=1 env var.

Zero Production Impact: In production builds, virtual:dev-inspector-mcp becomes a no-op module.

Supported Frameworks

React, Vue, Svelte, SolidJS, Preact, Next.js (Webpack + Turbopack), React Router v7+. Angular support in progress.

Agent Skills

DevInspector ships a built-in Agent Skill for Claude Code (and compatible AI agents) that teaches the agent how to integrate and troubleshoot the inspector.

Install it with one command:

npx skills add mcpc-tech/dev-inspector-mcp

The skill covers setup for all supported bundlers, common gotchas, and troubleshooting -- so the agent can guide you through the entire integration without back-and-forth.

What are Agent Skills? Skills are Markdown-based instruction sets that AI agents load at session start to gain domain-specific knowledge. See the Claude Code docs for more.

Configuration

Auto-Update MCP Config

The plugin automatically updates MCP configuration files for detected editors when the dev server starts. This saves you from manually configuring MCP endpoints.

Supported editors: Cursor, VSCode, Windsurf, Claude Code, Antigravity

// vite.config.ts
DevInspector.vite({
  // Auto-detect and update (default: true)
  updateConfig: true,

  // Or specify editors manually
  updateConfig: ['cursor', 'vscode'],

  // Or disable
  updateConfig: false,

  // Server name in MCP config (default: 'dev-inspector')
  updateConfigServerName: 'my-app-inspector',
})

Custom editors: For non-standard editors, use customEditors:

DevInspector.vite({
  customEditors: [
    {
      id: 'my-editor',
      name: 'My Editor',
      configPath: '~/.my-editor',        // absolute, ~/relative, or project-relative
      configFileName: 'mcp.json',
      serverUrlKey: 'url',               // default: 'url'
      configFormat: 'mcpServers',        // 'mcpServers' or 'servers' (vscode-style)
    },
  ],
})

Agent Installation

DevInspector supports multiple AI agents via ACP.

For npm-based agents (Claude Code, Codex CLI, Cursor Agent, Droid), you can pre-install them as dev dependencies for faster loading.

For system-level agents, install globally:

Gemini CLI

npm install -g @google/gemini-cli

Documentation →

Kimi CLI

uv tool install --python 3.13 kimi-cli

Documentation →

Goose

pipx install goose-ai

Documentation →

Opencode

curl -fsSL https://opencode.ai/install | bash

Documentation →

CodeBuddy Code

npm install -g @tencent-ai/codebuddy-code

Documentation →

Note: If you don't pre-install npm-based agents, they will be launched via npx on first use (slower startup).

Pre-installing npm-based Agents (Recommended)

The recommended way is to install agents during initial setup (see Installation above).

Alternatively, install them later as dev dependencies:

# npm
npm i -D @zed-industries/claude-code-acp

# pnpm
pnpm add -D @zed-industries/claude-code-acp

# Or add directly to package.json

{
  "devDependencies": {
    "@zed-industries/claude-code-acp": "^0.12.4",
    "@zed-industries/codex-acp": "^0.7.1",
    "@blowmage/cursor-agent-acp": "^0.1.0",
    "@yaonyan/droid-acp": "^0.0.8"
  }
}

About optionalDependencies: Agent packages are installed by default. If you don't need them, use --no-optional when installing.

Why install as devDependencies?

• Ensures faster startup (uses local package via require.resolve instead of npx)
• Won't affect production bundle (tree-shaken out unless imported)
• Standard practice for development tools

Custom Agents

This plugin uses the Agent Client Protocol (ACP) to connect with AI agents.

⏱️ Note: Initial connection may be slow as agents are launched via npx (downloads packages on first run).

Default agents: View configuration →

You can customize available AI agents, filter visible agents, and set a default agent:

// vite.config.ts
export default {
  plugins: [
    DevInspector.vite({
      enabled: true,

      // Option 1: Only show specific agents (filters merged agents)
      visibleAgents: ['Claude Code', 'Gemini CLI', 'Goose'],

      // Option 2: Add custom agents (merges with defaults)
      agents: [
        {
          name: "Claude Code", // Matches default - auto-fills icon and env
          command: "npx",
          args: ["-y", "@zed-industries/claude-code-acp"],
        },
        {
          name: "My Custom Agent",
          command: "my-agent-cli",
          args: ["--mode", "acp"],
          env: [{ key: "MY_API_KEY", required: true }],
          meta: { icon: "https://example.com/icon.svg" }
        }
      ],

      // Option 3: Combine both - add custom agents and filter visibility
      agents: [
        {
          name: "My Custom Agent",
          command: "my-agent-cli",
          args: ["--mode", "acp"],
          env: [{ key: "MY_API_KEY", required: true }],
          meta: { icon: "https://example.com/icon.svg" }
        }
      ],
      visibleAgents: ['Claude Code', 'My Custom Agent'], // Only show these

      // Set default agent to show on startup
      defaultAgent: "Claude Code"
    }),
  ],
};

Key Features:

• agents: Merges your custom agents with defaults. Agents with the same name as default agents automatically inherit missing properties (icons, env)
• visibleAgents: Filters which agents appear in the UI (applies after merging). Great for limiting options to only what your team uses
• defaultAgent: Sets which agent is selected on startup
• If no custom agents provided, defaults are: Claude Code, Codex CLI, Gemini CLI, Kimi CLI, Goose, Opencode, Cursor Agent, Droid, CodeBuddy Code

MCP Servers Configuration

You can configure external MCP servers for agents to access additional tools.

DevInspector.vite({
  mcpServers: [
    // HTTP/SSE Server
    {
      name: 'remote-server',
      type: 'sse', // or 'http'
      url: 'https://api.example.com/sse',
      headers: [{ name: 'Authorization', value: process.env.MCP_TOKEN ?? '' }]
    },
    // Local Stdio Server
    {
      name: 'local-server',
      command: 'npx',
      args: ['-y', '@modelcontextprotocol/server-memory'],
      env: { MY_VAR: 'value' }
    }
  ]
})

What It Does

Click element → Describe issue → AI analyzes → Get fix

1. Click any UI element to capture context (source, styles, DOM)
2. Describe what's wrong or ask a question about the element
3. AI diagnoses using Chrome DevTools integration
4. Get intelligent solutions through natural conversation

Examples:

• "Why is this button not clickable?" → AI checks pointer-events, z-index, overlays
• "This API call is failing" → AI analyzes network requests, timing, responses
• "Where is this component?" → Jump to source file and line number

Two Workflow Modes

DevInspector offers two ways to interact with your AI, depending on your preference:

1. Editor Mode

Best for: Code-heavy tasks, refactoring, and maintaining flow.

• How it works: You use your IDE's AI assistant (Cursor, Windsurf, Copilot).
• The Flow: Click an element in the browser -> The context (source, props, styles) is sent to your Editor via MCP -> You ask your Editor to fix it.
• Why: Keeps you in your coding environment.

2. Inspector Bar Mode (Recommended)

Best for: Quick fixes, visual tweaks, or if you don't use an AI editor.

• How it works: You use the floating "Inspector Bar" directly in the browser.
• The Flow: Click "Ask AI" in the browser -> Select an agent (e.g., Claude Code, Custom Script) -> The agent runs in your terminal but interacts with the browser overlay.
• Why: No context switching. Great for "what is this?" questions or network debugging.

MCP Tools

capture_element_context

Capture single element context. Two modes:

• Interactive (default): User clicks element to select
• Automated: Use selector param for programmatic capture

Returns: source location, DOM hierarchy, computed styles, dimensions, user notes, screenshot.

capture_area_context

Capture multiple elements in an area. Two modes:

• Interactive (default): User draws rectangle to select area
• Automated: Use containerSelector or bounds param

Returns: array of element contexts (max 50).

get_page_info

Get page overview with accessibility tree. Returns URL, title, viewport, document size, and semantic structure (landmarks, headings, forms, links). Start here to understand the page.

list_inspections

List all captured inspections with ID, element details, source location, notes, and status (pending/in-progress/completed/failed).

update_inspection_status

Update inspection status. Parameters: inspectionId (optional, auto-detects), status ('in-progress'|'completed'|'failed'|'deleted'), message (required for completed/failed).

execute_page_script

Execute JavaScript in browser context. Access: window, document, DOM APIs, React/Vue instances, localStorage. Must return a value.

get_network_requests

Get network requests from browser. Returns list with reqid, method, URL, status. Use reqid param to get full request/response details (headers, body, timing).

get_console_messages

Get console messages from browser. Returns list with msgid, level (log/warn/error), message. Use msgid param to get full message details.

get_stdio_messages

Get dev server stdout/stderr. Returns list with stdioid, stream type, content. Use stdioid param to get full message.

chrome_devtools

Agentic tool for Chrome DevTools access. Provides network inspection, console logs, performance metrics, element interaction, and more.

Custom Inspector Tools

You can register your own custom tools to be used by the AI agent. These tools run directly in the browser context, giving the AI access to your application's state, logic, or any browser APIs.

registerInspectorTool

Use this function to register a tool. It handles the MCP schema definition and implementation in one place.

// main.ts or any entry file
import { registerInspectorTool } from 'virtual:dev-inspector-mcp';

registerInspectorTool({
  name: "get_user_state",
  description: "Get current user session and preferences",
  inputSchema: {
    type: "object",
    properties: {
      includeToken: {
        type: "boolean",
        description: "Whether to include the auth token"
      }
    }
  },
  implementation: (args) => {
    // This runs in the browser!
    const user = window.useUserStore?.getState();

    if (args.includeToken) {
      return { user, token: localStorage.getItem('token') };
    }
    return { user };
  }
});

These custom tools are automatically discovered and made available to the connected AI agent along with the built-in inspector tools.

MCP Prompts

capture_element_context

Capture single element context. Interactive (user clicks) or automated (selector param).

capture_area_context

Capture multiple elements in area. Interactive (user draws rectangle) or automated (containerSelector/bounds param).

list_inspections

View all element inspections in the queue with their status.

launch_chrome_devtools

Launch Chrome DevTools and navigate to a specified URL for debugging and inspection.

Parameter: url (required) - The URL to navigate to (e.g., http://localhost:3000)

get_network_requests

List network requests or get details of a specific one. Always refreshes the list first.

get_console_messages

List console messages or get details of a specific one. Always refreshes the list first.

get_stdio_messages

List stdio (stdout/stderr) messages from the server process. Always refreshes the list first.

Architecture

For a deep dive into how the MCP context, CMCP library, and Puppet binding mechanism work together, see the Architecture Documentation.

Key concepts:

• Hub-and-spoke model: Vite dev server acts as central hub managing multiple client connections
• CMCP bidirectional execution: Server defines tool schemas, browser client provides implementations
• Puppet binding: Enables Chrome DevTools ↔ Inspector message passthrough
• Dynamic rebinding: Automatic connection recovery after browser refresh

License

MIT