/**
 * The `autoResize` sizing POLICY (guuey#992) — the host's side of the
 * `ui/notifications/size-changed` handshake, kept pure so the loop it
 * prevents is pinned by `auto-resize.test.ts` without a DOM.
 *
 * Why a policy and not "apply the report": the view runtime
 * (`@ggui-ai/iframe-runtime`) measures `documentElement` at `max-content`.
 * A view whose body is viewport-bound (`min-height: 100vh` — routine in
 * generated card CSS, and agent-generated HTML is not ours to control)
 * measures the frame's OWN height plus a constant δ (margins, padding) and
 * reports it back; a host that applies every report verbatim grows the
 * frame by δ per tick without bound. The founder's first prod card sat at
 * 86,816 px. The view cannot tell the two apart; the host can:
 *
 *   1. CEILING — a report is clamped to `ceiling` (the host viewport, or
 *      the embedder's `maxHeight`). A taller card scrolls inside its frame,
 *      as in every chat client.
 *   2. ECHO DETECTOR — a SECOND consecutive growth by the same δ (±2 px),
 *      arriving within {@link ECHO_WINDOW_MS} of our own apply, is the view
 *      echoing the frame, not content: the frame is HELD. The runtime
 *      dedupes identical reports, so a held frame goes quiet.
 *
 * Everything else applies: the first report, every shrink (which also
 * releases a hold), and a growth that is not an echo — real content growth
 * (a section opened) still sizes the frame.
 */
/** Two same-δ growths inside this window after our apply = the echo. */
export declare const ECHO_WINDOW_MS = 1000;
/** δ tolerance between the two growths — sub-pixel rounding, not content. */
export declare const ECHO_DELTA_TOLERANCE_PX = 2;
export interface AutoResizeState {
    /** The height the host last applied to the frame, if any. */
    readonly applied?: number;
    /** When it was applied (ms clock the caller supplies). */
    readonly appliedAt?: number;
    /** The growth (report − applied) the last apply was, if it was a growth. */
    readonly lastDelta?: number;
    /** When the last report arrived — a held frame stays held while growth reports keep coming. */
    readonly lastReportAt?: number;
    /** True while the frame is held against an echo. */
    readonly held: boolean;
}
export interface AutoResizeDecision {
    /** The height to apply now, or `undefined` to leave the frame as it is. */
    readonly apply: number | undefined;
    readonly state: AutoResizeState;
}
export declare function initialAutoResizeState(): AutoResizeState;
export declare function decideAutoResize(state: AutoResizeState, reportedHeight: number, nowMs: number, ceiling?: number): AutoResizeDecision;
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