Constant MAX_USER_TEXTURE_SLOTS 

pub const MAX_USER_TEXTURE_SLOTS: usize = 8;

Maximum simultaneously-bound user textures per preset. Sized to cover the in-the-wild distribution: a typical preset survey shows ≤ 4 distinct sampler sampler_X; declarations per shader; 8 leaves headroom without blowing past the comp pipeline’s bind-group budget. Presets that exceed this cap are translated with the first 8 slots used and the rest falling through to the standard fallback path (sampler_main).