GenClass MCP sunucusu

GenClass plugin

For Claude Code, Codex, Cursor, Gemini CLI and other agents that read plugins or skills. GenClass lets the agent see what happens inside the pages of your web app running on your machine (each click, request and response, the order the responses were delivered, what each response wrote into the app's state, uncaught errors), find race conditions by re-running a page with the network answering in different orders, replay one exact order to prove a fix, and write a Playwright test that fails while the bug is there.

Install

Claude Code (the server, a prompt hook that brings new findings to each prompt, and the genclass skill):

/plugin marketplace add genclass-dev/genclass-plugin
/plugin install genclass@genclass

Codex (the server and the skill): codex plugin marketplace add genclass-dev/genclass-plugin, then codex plugin add genclass@genclass. Gemini CLI (the same): gemini extensions install https://github.com/genclass-dev/genclass-plugin. The skill alone, in any agent the skills CLI knows: npx skills add genclass-dev/genclass-plugin; for GitHub Copilot, gh skill install genclass-dev/genclass-plugin genclass.

Then connect your app's development build and load a page of the dev server. genclass_setup prints the install line (npm install @genclass/runtime@0.3.0-beta.6, the version this release was tested with; the page side needs 0.3.0-beta.1 or later) and the lines for your framework, behind a development check. See the package README.

What the agent asks first

The skill and the server's instructions tell the agent to show you each of these and wait for your yes: running the install or adding the lines genclass_setup prints; npx playwright install chromium and npm i -D playwright; genclass_scan with hosted: true; writing a fix or a test when you only asked what broke. These are instructions to the agent, not locks in the code; your client's own permission prompts still apply.

What it installs

In the plugin repository the server is vendored: server/cli.mjs is the published @genclass/mcp@0.2.2 build (its dist/cli.js, byte for byte, fetched from npm by the daily sync), server/genclass-mcp.mjs is the package's command importing it, and .mcp.json and the hook run them with node from ${CLAUDE_PLUGIN_ROOT}, so installing the plugin installs nothing and runs the exact release it was reviewed with (the one download is genclass_scan's, below); there is no package.json or lockfile. The copy of this folder inside GenClass runs npx -y @genclass/mcp@0.2.2 instead (nothing built is committed there). plugin.json and mcp.json at this folder's root are the same server in the Agent Plugins format, for Cursor, Codex and other clients that read it (server and skill, no hook); that format has no plugin-root variable, so they keep npx.

What the hook sends, and where

Only to this machine. It reads the bridge's token from ~/.genclass/bridge-47357.token (mode 0600), asks the bridge at http://127.0.0.1:47357 for findings newer than its cursor, keeps that cursor in .genclass/agent/hook-cursor in the project, and prints the new findings' ids, kinds, pages and titles for Claude Code to add to the prompt. Page strings are quoted and labelled as recorded data, not instructions. It sends nothing else anywhere, prints nothing when no bridge is running or nothing is new, and gives up after 0.8 seconds if the bridge does not answer. The first prompt of a session only sets the cursor (genclass_findings has the backlog).

The server listens on 127.0.0.1 only and accepts pages from this machine (localhost, 127.0.0.1, *.localhost) or origins you list in GENCLASS_AGENT_ORIGINS. Nothing leaves your machine unless you or your agent ask for it: genclass_analytics {source: "production"} reads your own GenClass dashboard when you set GENCLASS_DASHBOARD to its link; genclass_scan with hosted: true sends the URL to the genclass.dev page check (without it, the page loads in a local headless browser); and GENCLASS_REPORT, off by default, mirrors finding ids, kinds, page paths, replay verdicts and counts to that dashboard, never titles or page text. When the project has no @genclass/runtime, genclass_scan downloads the version this release pins, @genclass/runtime@0.3.0-beta.6, from npm through npx. Details: AGENT.md section 6.

Privacy

By default the plugin collects nothing and sends nothing to GenClass or anyone else; the exceptions you can turn on are listed above. Findings stay in .genclass/agent/ in your project (gitignored by the server) and in the bridge's memory.

The lines genclass_setup prints start the runtime in development builds only, and a production build drops them. On a local or private address the runtime sends no diagnostics (it does fetch its on-device model from jsDelivr). Running it in production is a separate choice this plugin does not need: outside the check GenClass.init() runs for every visitor and sends anonymous diagnostics from public hosts by default, which GenClass.init({ telemetry: false }) turns off (PRIVACY.md).

Turn it off

• Everything: /plugin disable genclass@genclass (or /plugin uninstall genclass@genclass).
• Only the hook: Claude Code has no switch for one plugin hook; uninstall the plugin and add the server alone (claude mcp add genclass -- npx -y @genclass/mcp@0.2.2), or set "disableAllHooks": true in your settings, which turns off every hook.
• In the app: remove the connectAgent(rt) block; the page then never talks to the bridge.

Where this comes from

This folder is packages/mcp/plugin in genclass-dev/GenClass. The repository genclass-dev/genclass-plugin is this folder at a repository root with the marketplace files and the vendored server, assembled by node packages/mcp/scripts/plugin-repo.mjs and re-synced daily, so issues and pull requests go to GenClass.

License

Apache-2.0. Source: packages/mcp.