Chrome Devtools CLI

Chrome DevTools CLI

Use the official chrome-devtools CLI to inspect and drive the running XMCL Electron app. Do not configure, enable, or call Chrome DevTools through MCP tools. The npm package name still contains mcp, but the chrome-devtools binary is its standalone CLI client and does not require an MCP client config.

Use this command prefix without adding a project dependency:

npx -y -p chrome-devtools-mcp@latest chrome-devtools

Connect to XMCL

1. Reuse the running dev:main and dev:renderer tasks. Do not start duplicate tasks or another Electron app.

2. Discover the active debugging port from the Electron process arguments or task output. Probe likely ports only as a fallback:

   curl --fail --silent http://127.0.0.1:9222/json/list
   curl --fail --silent http://127.0.0.1:9300/json/list
   

3. Stop a stale CLI daemon, connect it to the discovered port, then verify the selected launcher page:

   npx -y -p chrome-devtools-mcp@latest chrome-devtools stop
   npx -y -p chrome-devtools-mcp@latest chrome-devtools start --browserUrl http://127.0.0.1:<port>
   npx -y -p chrome-devtools-mcp@latest chrome-devtools list_pages --output-format=json
   

   The real development page must be titled X Minecraft Launcher or XMCL and load from http://localhost:3000, not http://xmcl.runtime. Keep its numeric page ID for every page-scoped command.

Drive and inspect

Take a fresh accessibility snapshot before resolving element UIDs. UIDs can change after navigation, hot reload, dialogs, or other DOM updates.

npx -y -p chrome-devtools-mcp@latest chrome-devtools take_snapshot <pageId> --output-format=json
npx -y -p chrome-devtools-mcp@latest chrome-devtools click <pageId> <uid>
npx -y -p chrome-devtools-mcp@latest chrome-devtools fill <pageId> <uid> "value"
npx -y -p chrome-devtools-mcp@latest chrome-devtools press_key <pageId> "Enter"
npx -y -p chrome-devtools-mcp@latest chrome-devtools evaluate_script "() => ({ title: document.title, href: location.href })" --pageId <pageId> --output-format=json

Inspect renderer failures and relevant requests after exercising the complete workflow:

npx -y -p chrome-devtools-mcp@latest chrome-devtools list_console_messages <pageId> --output-format=json
npx -y -p chrome-devtools-mcp@latest chrome-devtools list_network_requests <pageId> --output-format=json

Use <command> --help before relying on an unfamiliar or version-sensitive flag. Prefer JSON output so results can be checked precisely. Screenshots for temporary inspection belong outside the repository unless the task explicitly requires review evidence:

npx -y -p chrome-devtools-mcp@latest chrome-devtools take_screenshot <pageId> --filePath "$TEMP/xmcl-devtools.png"

For the main launcher, validate at 1200x720 and, when layout risk warrants it, 800x400. Do not use mobile-like viewport sizes.

Finish

• Preserve user state and remove only temporary resources created by the test.

• After a main/runtime rebuild, restart only this repository's Electron app, reconnect the CLI, and repeat the same workflow.

• Run the narrowest automated test plus type-check or lint required by AGENTS.md; CLI validation does not replace those checks.

• Stop the CLI daemon when validation is complete:

  npx -y -p chrome-devtools-mcp@latest chrome-devtools stop
  

• Report the route and controls exercised, observed state transitions, relevant console/network results, screenshots if requested, and cleanup performed.