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Nested error boundaries break the devtools #245
Description
When you have a layout route with a child route that has an error boundary, the devtools will error the page when trying to add the outlet-route route class to a dom node when the classList is an ErrorBoundary. This results in the page loading, then immediately erroring.
Error:
Oops!
Cannot read properties of undefined (reading 'add')
TypeError: Cannot read properties of undefined (reading 'add')
I only ever see this with RenderErrorBoundary as the name of the fiber node. To be honest, I'm not sure where to dissect this further.
Activity
c43721 commentedon Jan 11, 2026
https://github.com/c43721/rrdt-nested-errors-bug
I found the reproduction. I've documented the steps in the readme here.
To reproduce, I created a layout route with a single child. In that child route, export an error boundary. Then try to load that route. It will always error.
c43721 commentedon Jan 11, 2026
It seems like it's not happy with the child error boundary, but the root one is always fine. When I tried to export an error boundary that's not in a nested layout file (in an Outlet for example) then it works perfectly fine. In my example, I documented both routes for clarity.
[-]useReactTreeListener errors out during certain error boundary criterias[/-][+]Nested error boundaries break the devtools[/+]AlemTuzlak commentedon Jan 13, 2026
@c43721 wow that's wild, i'll see if i can fix that up, i'm looking into an issue with perf atm and i'll toss this into there as well!
c43721 commentedon Jan 13, 2026
Thanks @AlemTuzlak. I would have offered to take it up but couldn't figure out the details quickly enough LOL
Thanks for your attention!
AlemTuzlak commentedon Jan 14, 2026
should be fixed with latest release, mind confirming? @c43721
c43721 commentedon Jan 14, 2026
@AlemTuzlak I can confirm this is closed and that #246 did fix it! Thank you.