When PCK is loaded using this code? Usually it is loaded as res://assets.sparsepck and handled by AAssetManager/FileAccessAndroid. And assets:// seems to be only used for Android Editor keystores.

Yeah, I'm honestly not too sure how often people typically try load .pck from assets://. I guess this will impact any file loaded from assets://, so if users are doing that for some reason and attempt to seek, that'll fail too. Again, presumably not that common or else this would have been raised before.

As to why I ran into this myself. I was setting up native Android debugging for GodotJS. I'm using --main-pack as quick and easy way to test my Godot projects.

I think it'd be good to have a bug report to discuss the specific conditions and use case where this would happen

The change looks good. Probably was not noticed since keystore is always read/written in one chunk. It's not really related to PCK, since anything using seek should fail.

But I'm not sure what was the purpose of adding assets:// in the first place, and whether it is supposed to be user accessible.

But I'm not sure what was the purpose of adding assets:// in the first place, and whether it is supposed to be user accessible.

The assets:// path provides a mean for editor build to access their own assets directory, since for editor builds, res:// points to the general filesystem where the loaded project is stored.
On template builds, res:// and assets:// point to the same location, but are handled by different logic, so on template builds, using res:// is the recommended approach.

Thanks!