/** Begin Synchronized Update (DEC private mode 2026 set). */
export declare const BSU = "\u001B[?2026h";
/** End Synchronized Update (DEC private mode 2026 reset). */
export declare const ESU = "\u001B[?2026l";
/**
 * Wrap a frame string in synchronized-update markers so the terminal presents it atomically.
 * Pure + side-effect free so it is unit-testable. When `sync` is false it returns the chunk
 * unchanged (escape hatch via CORTEX_TUI_NO_SYNC).
 */
export declare function wrapFrame(chunk: string, sync: boolean): string;
export interface RenderStats {
    /** Number of write() calls intercepted. */
    writes: number;
    /** Total bytes (string length) written, excluding the BSU/ESU markers we add. */
    bytes: number;
    /** How many of those writes carried a full-screen clear (the flicker-prone path). */
    clears: number;
    /** epoch ms of the first and last intercepted write (for a writes/sec estimate). */
    firstAt: number;
    lastAt: number;
}
export declare function newRenderStats(): RenderStats;
/** Fold one write into the running stats (exported for testing). */
export declare function recordWrite(stats: RenderStats, chunk: string, now: number): void;
/** Derived writes-per-second over the observed window (0 when fewer than 2 writes). */
export declare function writesPerSecond(stats: RenderStats): number;
export interface RenderStdoutOptions {
    /** Wrap frames in BSU/ESU (default true; disabled by CORTEX_TUI_NO_SYNC). */
    sync?: boolean;
    /** Collect render stats; the returned object is exposed on `__renderStats`. */
    stats?: RenderStats | null;
    /** Clock injection for tests. */
    now?: () => number;
}
/** A stdout proxy that also surfaces the stats object it accumulates into. */
export type RenderStdout = NodeJS.WriteStream & {
    __renderStats?: RenderStats | null;
};
/**
 * Build a proxy over `base` (typically process.stdout) that intercepts only `write` — wrapping
 * string frames in synchronized-update markers and folding them into `stats` — while delegating
 * every other property (columns/rows getters, on/off, isTTY, …) to the real stream, with `this`
 * bound to the real stream so the getters report the real terminal geometry. Ink, log-update, and
 * App's useStdout all share this one object, so they stay consistent.
 */
export declare function makeRenderStdout(base: NodeJS.WriteStream, options?: RenderStdoutOptions): RenderStdout;