[DevTools Bug]: v6.0.0 (9/26/2024) of devtools makes a page extremely slow in dev (even when devtools are closed)

Website or app

difficult to build a repor for now, since

Repro steps

I'm unsure what's the best way to reproduce the issue, but I'm loading a page with React Router v6 with React@19.0.0-rc-6cf85185-20241014 (using the latest version of the compiler), and v6.0.0 of devtools. Chrome version 129.0.6668.101 (Official Build) (arm64) on MacOS.

Even with devtools closed, page loads become very sluggish in development. If I run a Chrome performance profiler, it completely stalls on opening a new page for 5 seconds (albeit we're not running the React profiler):

When I turn off React Developer tools, page loads become instant when devtools are closed, and Chrome profiler is also 10x faster.

The problem is so bad that we thought we had a memory leak in our app somewhere, but it was all good in the built version of the app. Turns out devtools had updated in the background and everything became sluggish in development as a result. After we disabled the extensions, everything became supper snappy in development again.

Would love to provide a repro, but I'm not exactly sure what conditions trigger the issue, as a barebones react router setup doesn't seem to do the trick.

How often does this bug happen?

Every time

DevTools package (automated)

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DevTools version (automated)

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Error message (automated)

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Error call stack (automated)

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Error component stack (automated)

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GitHub query string (automated)

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No source file, test, or reliable reproduction is provided. Start by comparing page-load performance in a React Router v6 app using React 19.0.0-rc-6cf85185-20241014 with React DevTools v6.0.0 enabled and disabled, using Chrome's performance profiler. Done means identifying reproducible triggering conditions and a confirmed DevTools fix or a narrowly scoped follow-up.