/**
 * A word diff of an AI answer against the text it rewrites, both as they
 * read, for the panel's changes view. Words come from the stream's own
 * segmentation, so Chinese is compared word by word rather than character by
 * character, and the spaces after a word are tokens of their own.
 */
export interface WordDiffPart {
    kind: 'same' | 'removed' | 'added';
    text: string;
}
/** `after` against `before`, or null when the two have too little in common to compare. */
export declare function diffWords(before: string, after: string): WordDiffPart[] | null;