Oh, what potato will do is that if the 4th to 6th bytes are not #f0 DEO2, then it will say "no metadata"

Ah! I think I understand what you're asking.

So, this whole thing doesn't require any change to the assembler. It uses just an old boring ;label reference.

That label can be named anything, the ;meta #f0 DEO2, is kind of like setting a vector, but we're not worrying about that right now, #f0 is a non-specified device in Varvara.

The assembler sees ;meta, and write the position of the @meta label, which could be any other name too.

https://git.sr.ht/~rabbits/drifblim/tree/main/item/src/drifblim.tal#L446

So the ROM author will have at the top of their .tal file:

|0100
;my-metadata #f0 DEO2
@on-reset
;0123 .System/r DEO2
[…]

and the assembler does the rest.

The metadata is part of the rom.

https://git.sr.ht/~rabbits/nasu/tree/main/item/src/nasu.tal#L1389

The #f0 is only so the emulator can also become aware of that metadata. For example, to rename the window, to draw an icon, etc..

Content warning: uxn metadata proposal Click to open/close