@casdevel Yes, you’re right on that - should have used that function instead. When I read the documentation originally I had assumed this was meant for cores that called it a single time per frame, so I used the other function instead. Slightly related, I noticed you forked and changed this on your end (to test if it helps, I imagine), but saw that you forked libretro/Mesen. You should probably fork SourMesen/Mesen, since Mesen is meant to be an upstream core (I still don’t understand why libretro/Mesen exists, and why the Android builds point to it).
@butanebob I won’t say outright “no”, but the last time I checked, I got the impression that this would involve a lot more changes than I feel is worth (I don’t want to have to rewrite a ton of filesystem-related code that’s been in use & tested for a while, just for the libretro core). So it may happen eventually, but probably not soon.