import type { SessionEvent, SessionEventToolOutputPreview } from "@opengeni/sdk";
/**
 * Exact reads of tool outputs a step page delivered as bounded previews.
 *
 * A turn's steps are read with `toolOutputs: "preview"`, so a large tool
 * output arrives as its head and tail with an `outputPreview` fact. When a
 * reader expands that row (or its renderer needs the exact output) the row's
 * exact output event is read once, by its sequence, and replaces the preview.
 */
export type ToolOutputReadState = "loading" | "error" | "loaded";
/** One row's exact-output read, as the timeline projection sees it. */
export type ToolOutputRead = {
    state: ToolOutputReadState | "preview";
    load: () => void;
};
export type ToolOutputReader = (eventId: string, sequence: number, turnId: string | null) => ToolOutputRead;
/** The exact tool-output events of a page around one sequence. */
export type ToolOutputPageRead = (sequence: number) => Promise<readonly SessionEvent[]>;
/** Exact-output reads in flight at once; the rest wait their turn. */
export declare const TOOL_OUTPUT_READS_IN_FLIGHT = 4;
/** The preview fact of a step-page tool output, or null for an exact one. */
export declare function toolOutputPreviewFact(payload: unknown): SessionEventToolOutputPreview | null;
/** Whether a session event is a tool output delivered as a preview. */
export declare function isToolOutputPreviewEvent(event: SessionEvent): boolean;
/**
 * Reads each requested row's exact output once, a few at a time. `read`
 * identifies the session: reads are forgotten when it changes. Exact outputs
 * are kept only for turns in `turns` (the turns whose steps are loaded).
 */
export declare function useToolOutputReads(read: ToolOutputPageRead, turns: ReadonlyMap<string, unknown>): {
    /** Exact output events by event id. */
    exact: ReadonlyMap<string, SessionEvent>;
    reader: ToolOutputReader;
};