/** Physical-row viewport state for native scrollback plus a bottom-anchored tail. */
export interface TranscriptViewportCursor {
    readonly sessionKey: string;
    readonly epoch: number;
    readonly flushedRows: number;
}
export interface TranscriptViewportInput {
    readonly sessionKey: string;
    readonly epoch: number;
    /** Physical durable transcript rows in the current rendered-history window. */
    readonly totalRows: number;
    /** Maximum durable rows retained outside Static for the live viewport. */
    readonly retainedRows: number;
}
export interface TranscriptViewportStep {
    readonly cursor: TranscriptViewportCursor;
    /** Durable physical rows emitted through Static. */
    readonly staticRows: number;
    /** Durable physical rows still available to the live viewport. */
    readonly liveRows: number;
}
/**
 * Advance the monotonic physical-row flush cursor.
 *
 * Ordinary renders never pull a row back out of native scrollback. A source-
 * backed replay (epoch change) flushes the complete durable window exactly
 * once after the caller clears/remounts Static; subsequent durable rows start
 * a fresh retained tail. Session/reset shrink starts from the new source.
 */
export declare function advanceTranscriptViewport(previous: TranscriptViewportCursor, input: TranscriptViewportInput): TranscriptViewportStep;
/** Real history rows that fit beside the currently painted stream/tool rows. */
export declare function visibleTranscriptRows(historyRows: number, occupiedRows: number, capacity: number): number;