Repository navigation
__TSR_index is NaN, resulting in invalid history notifications (subscriber) #3907
Description
Which project does this relate to?
Router
Describe the bug
I tried subscribing to router history changes to track back/forward navigation, but it's not working for me. When using the browser’s back/forward buttons, I get this action - { type: 'GO', index: NaN }.
I looked into history/src/index.ts and found that the history index is stored in __TSR_index, and in my case, it's NaN (see screenshot).
Your Example Website or App
https://stackblitz.com/edit/github-gn1q23iq?file=src%2Froutes%2F__root.tsx
Steps to Reproduce the Bug or Issue
- Navigate to About page
- Navigate back using browser back button
Expected behavior
I'd expect BACK action type being sent when using browser back button
Screenshots or Videos
Platform
- macOS
- Chrome
- Version: 134.0.6998.166
Additional context
No response
Activity
schiller-manuel commentedon Apr 1, 2025
cc @ferretwithaberet
LadyBluenotes commentedon Jul 12, 2026
Thanks for the report. I can still reproduce this on current main.
createBrowserHistorytreats an existingkey/__TSR_key as initialized state even when __TSR_index is missing. The next navigation then derives an index from undefined, which becomesNaN, and the following popstate is reported asGO.This needs a small normalization step for partial existing history state, plus a browser-history regression test.