/**
 * Bounded retention for the session checkpoint list (`state.checkpoints`).
 *
 * Mirrors the dual-budget pattern of history-retention.ts: the checkpoint
 * list is a display index into the canonical session record, not the record
 * itself. The JSONL session log still carries every `checkpoint` event, so
 * pruning old in-memory rows loses nothing — `/rewind` simply shows the
 * newest slice. Without a bound, resuming a long session rebuilt every
 * checkpoint ever written into memory (see buildRestoredCheckpoints) and
 * the live `checkpointReceived` reducer appended forever.
 *
 * This module is pure TypeScript — no React, no Ink.
 */
import type { State } from './app-state.js';
export type CheckpointEntry = State['checkpoints'][number];
/** Default maximum number of retained checkpoints. */
export declare const TUI_CHECKPOINTS_MAX_ENTRIES = 200;
/** Default maximum serialized bytes across all retained checkpoints. */
export declare const TUI_CHECKPOINTS_MAX_BYTES: number;
export interface CheckpointBudget {
    maxEntries?: number | undefined;
    maxBytes?: number | undefined;
}
/**
 * Retain the newest checkpoints within both a count and serialized-byte
 * budget. Checkpoints are chronological (ascending promptIndex), so the
 * newest entries are at the end of the array. Like retainTuiHistory, at
 * least one entry is always kept — dropping the only checkpoint would make
 * `/rewind` report "no checkpoints" for a session that has one.
 *
 * Returns the ORIGINAL array reference when nothing needs pruning so
 * reducer callers can bail out without scheduling another render.
 */
export declare function retainCheckpoints(checkpoints: CheckpointEntry[], budget?: CheckpointBudget): CheckpointEntry[];
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