Constant MAX_SEARCH_QUERY_SCALARS 

pub const MAX_SEARCH_QUERY_SCALARS: usize = 1_024; // 1_024usize

Maximum Unicode scalar values accepted from one interactive query.

This is an input-work ceiling, independent of the page budgets. A pasted multi-megabyte string must not become one gram phrase per scalar on the UI thread. The limit is far above a meaningful palette query; callers receive an empty page for longer input and can refine it normally.