Editorial recipe — not benchmarked — reviewed September 3, 2026
Diagnose and verify a browser performance regression
For web teams with a reproducible slow page and authority to run isolated browser tests.
Run this recipe
Work through it here
Progress stays in this browser. The downloaded Markdown kit works in any notes app or repository.
0/5 complete
Is this recipe useful?
Procedure
- Freeze the affected URL, viewport, browser version, data state, network and CPU conditions, and a repeatable user action before changing code.
- Use Playwright to reproduce the flow and capture functional timing; record a Chrome DevTools performance trace plus relevant console and network evidence in an isolated profile.
- Ask one coding agent to trace the bottleneck to a shared root cause and make the smallest fix that preserves behavior and accessibility.
- Repeat the identical run several times before and after, compare medians and trace insights, and fail the change if the user flow or functional checks regress.
- Have a different model review the diff and raw evidence, then manually confirm the flow on a representative real device before publishing the bounded result.
Acceptance artifact
A reproducible scenario, before-and-after traces, functional checks, bounded root-cause fix, and reviewed performance decision
Do not use it blindly
One lab trace is not field performance; browser profiles may contain sensitive data, and Chrome DevTools MCP can expose or modify anything in the connected instance.