Using v-for on an object with key/value, the key is typed as number

This is the same issue as #8819, but i cannot reopen that one.

It seems to me that the issue reappeared, the original reproducer shows the key to be string | number even with the latest version available on play.vuejs.org

https://play.vuejs.org/#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

Originally posted by @syyyr in https://github.com/vuejs/core/issues/10963#issuecomment-3528008872