Similar to ImmediatelyFast, Sodium detects core shader changes (in their case displaying warnings to the user). They allow resource packs to opt-out of this feature in pack.mcmeta, acknowledging that things will break. Would it be possible to add a similar option for ImmediatelyFast? I have packs that modify text shaders, but shouldn't interfere with IF's optimisations - disabling features would reduce client performance without any actual benefit to me.

Added it. Resource packs can now declare compatibility with certain features, which would normally get disabled when the pack modifies certain core shaders. Example which force enables all features, which would normally be disabled if certain core shaders are modified:

"immediatelyfast": {
    "compatible_features": ["font_atlas_resizing", "hud_batching", "experimental_screen_batching"]
}

Thank you!

Yes I can add such a feature

Do you have a resource pack which utilizes the sodium opt out feature? If yes, could you upload it here or send a link to it. I would like to make a similar implementation, so resource pack authors don't have to know about different opt out files and any mod opt out is in the same place.

here's an example pack - it's just a section in pack.mcmeta (defined here in the sodium code)

sodium shader example.zip