/**
 * Pure decision helper for kv-cache history slicing used by
 * `completion-stream.ts` (via the slice computed from
 * `TurnHandle.savedCount`).
 *
 * This module intentionally has **no** `bare-*` imports so it can be
 * exercised directly from unit tests running under `bun` without
 * pulling in the Bare runtime (which is not available in that
 * environment).
 *
 * Cancel detection flows through the per-request `AbortSignal` from
 * `RequestRegistry`; the `cachedMessageCounts` map lives in
 * `kv-cache-session.ts`, which owns all three KV-cache bookkeeping
 * layers (saved counts, init flags, on-disk files). Only the pure
 * slice-decision helper remains here.
 */
export interface HistoryMessage {
    role: string;
    content: string;
    attachments?: {
        path: string;
    }[] | undefined;
}
export interface HistorySliceDecision {
    /** Messages to send to the model on the next turn. */
    messages: HistoryMessage[];
    /**
     * True when the decision path proves the current `savedCount` is stale
     * and the caller should drop the cached entry (via
     * `KvCacheSession.dropStaleSavedCount(turn)`) to avoid propagating the
     * bad count to the next turn.
     */
    clearStaleCount: boolean;
}
/**
 * Pure slice decision for `prepareMessagesForCache`.
 *
 * Mirrors the shape of the logic in `completion-stream.ts` but without
 * calling `transformMessages` (which depends on `bare-fs` for
 * attachment probing). Kept here so the decision can be unit-tested in
 * isolation.
 *
 * The key regression guard: when a non-zero `savedCount` would slice
 * the history down to an empty array, it is treated as stale — the
 * caller falls back to sending the system-stripped full history rather
 * than handing the model an empty payload.
 */
export declare function decideCachedHistorySlice(savedCount: number, cacheExists: boolean, history: HistoryMessage[]): HistorySliceDecision;
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