playwright-debug

Testing & Quality

This skill should be used when the user asks to "debug the electron app", "connect playwright to VoiceTree", "take screenshots of the running app", "interact with the live UI", "inspect the running application", or "test UI elements live". Provides step-by-step instructions for connecting Playwright MCP to a running Electron app for live debugging and automation.

License unclear

QUICK START

How to use this skill

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Source SKILL.md: https://github.com/voicetreelab/voicetree/blob/HEAD/.claude/skills/playwright-debug/SKILL.md

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Playwright MCP Live Debugging

Connect to a running VoiceTree Electron app for live debugging via browser automation.

Quick Start (3 steps)

1. Start Electron in debug mode

cd webapp && npm run electron:debug

This starts Electron with CDP enabled on port 9222 and automatically calls prettySetupAppForElectronDebugging() once the renderer is ready — loading the example_small project and spawning 3 debug terminals.

Run with a bash timeout (e.g. 30s) since this is a long-running dev server.

2. Verify CDP is ready

curl -s http://localhost:9222/json/version

Should return JSON with "Browser": "Chrome/...".

3. Go straight to inspecting — do NOT navigate

The app is already loaded with the project and debug terminals. Do not run browser_navigate or page.goto() — this would force-refresh and destroy the loaded state. Instead, jump directly to:

// browser_evaluate — check cytoscape nodes
const cy = window.cytoscapeInstance;
JSON.stringify({ nodeCount: cy.nodes().length, edgeCount: cy.edges().length });

Use browser_snapshot or browser_take_screenshot for visual inspection.

Opening a specific project (optional)

If you need a specific project instead of the test fixture:

await window.electronAPI.main.initializeProject('/path/to/folder');

Available Tools

Tool	Purpose
`browser_snapshot`	Get accessibility tree of current page
`browser_click`	Click elements by ref
`browser_hover`	Hover over elements
`browser_type`	Type into inputs
`browser_evaluate`	Run JavaScript in page context
`browser_tabs`	Switch between tabs
`browser_wait_for`	Wait for text/elements
`browser_take_screenshot`	Capture visual screenshot

Accessing App APIs

The app exposes window.electronAPI with useful methods:

// Via browser_evaluate
Object.keys(window.electronAPI.main)

// Key methods:
window.electronAPI.main.prettySetupAppForElectronDebugging()  // Spawn debug terminals
window.electronAPI.main.initializeProject(path)  // Open a folder
window.electronAPI.main.getGraph()               // Get graph data
window.electronAPI.main.getNode(id)              // Get node details
window.electronAPI.main.loadSettings()           // App settings

Cytoscape Instance

Access the graph directly via window.cytoscapeInstance:

// Get all nodes in the graph
const cy = window.cytoscapeInstance;
cy.nodes().map(n => ({ id: n.id(), isContext: n.data('isContextNode') }));

// Get node count
cy.nodes().length;

CRITICAL: Do NOT navigate or refresh the app

electron:debug automatically loads the project and spawns debug terminals. The app is already at the right page when CDP is ready. Do NOT:

Run browser_navigate / page.goto() — this will force-refresh the app and lose all loaded state
Hit /json in the browser — same problem

Instead, go straight to browser_evaluate to inspect the page state (e.g. query cytoscape nodes, check DOM elements). Use browser_snapshot or browser_take_screenshot for visual inspection.

CRITICAL: Be surgical when killing Electron processes

VoiceTree itself runs as an Electron process. A blanket pkill -f electron or kill -9 on all Electron PIDs will kill your own host app. To kill only the debug Electron:

# Find ONLY the process listening on port 9222
lsof -i :9222 -sTCP:LISTEN
# Then kill that specific PID
kill <pid>

Never use pkill -f electron or kill Electron PIDs found via lsof -i :9222 without the -sTCP:LISTEN filter — connected clients (including your own app) also show up.

Troubleshooting

Issue	Solution
Connection refused	Ensure Electron started with `npm run electron:debug`
Timeout on first connect	Retry - first connection can be slow
Wrong tab selected	`browser_tabs action=select index=1`
Native dialog opened	Use JavaScript APIs instead - native dialogs can't be automated
Old Electron still running	`lsof -i :9222 -sTCP:LISTEN` then `kill <that-pid>`

Architecture

Claude Code → @playwright/mcp --cdp-endpoint http://localhost:9222 → CDP → Electron App → VoiceTree Webapp

Notes

CDP only accesses renderer process, not Electron main process
Hot reload works - no restart needed on code changes
Native file dialogs cannot be automated - use electronAPI.main.initializeProject() instead
Only one debug session at a time (port 9222 hardcoded)