Phase 4 Step 10: DevTools Protocol (CDP subset)

[thomasnemer]

Parent: #41

Goal

Implement a subset of the Chrome DevTools Protocol (CDP) to enable debugging with Chrome DevTools frontend, Playwright, and Puppeteer.

Prerequisites

• None (framing can start early; domains are added as subsystems mature)

Implementation

• WebSocket server activated via --remote-debugging-port=PORT CLI flag
• CDP message framing: JSON-RPC over WebSocket, method dispatch
• Page domain: navigate, reload, getFrameTree, lifecycle events
• Runtime domain: evaluate, callFunctionOn, getProperties, console API
• DOM domain: getDocument, querySelector, getOuterHTML, setAttributeValue
• CSS domain: getComputedStyleForNode, getMatchedStylesForNode
• Network domain: requestWillBeSent, responseReceived, loadingFinished
• Console domain: messageAdded
• New dependency: tokio-tungstenite

Tests

• WebSocket connection and message framing tests
• Method dispatch and error handling tests
• Per-domain command/response tests
• Integration test: connect Chrome DevTools frontend
• Integration test: basic Playwright/Puppeteer script

Acceptance Criteria

• WebSocket server starts on specified port
• CDP domains (Page, Runtime, DOM, CSS, Network, Console) respond correctly
• Chrome DevTools frontend can connect and inspect pages
• Basic Playwright/Puppeteer automation scripts work