devtools

Use CDP at localhost:9222. Use agent-browser (simpler than Playwright) where helpful. For human-visible UI interaction, start with agent-browser snapshot -i; prefer returned @e* references, then role + accessible name. Re-snapshot after meaningful UI state changes. Fall back to DOM/CSS only when AX lacks the target. Playwright browsers are under ${HOME}/.local/share/playwright-browsers; set PLAYWRIGHT_BROWSERS_PATH accordingly.

• For state-changing actions, verify the target and current state first, act once, then verify the observable postcondition before continuing or retrying; never blindly repeat a possibly committed action.
• For repeated structured reads, inspect fetch/XHR before building browser automation. Replay a stable request when it returns the required data; verify representative results against the browser.
• Match representation to problem: AX for semantic targeting; DOM/JS for exact extraction; Network/CDP for APIs/protocol state; screenshots/geometry for visual, canvas, SVG, drag/brush issues.
• On CSP-heavy sites such as WhatsApp or Google apps, inline script injection may fail. A blob: script URL created in page context is a useful fallback.
• Do not persist credentials or session headers.