/**
 * Stable evidence key for a durable-change proposal: sha256 of the layer plus its summary,
 * lowercased and whitespace-collapsed, truncated to 24 hex chars. Normalization means the same
 * lesson re-observed with reworded whitespace/casing accumulates onto one key instead of scattering.
 */
export declare function observationKey(layer: string, summary: string): string;
export declare class ObservationStore {
    private readonly filePath;
    private readonly readOnly;
    constructor(filePath: string, options?: {
        readOnly?: boolean;
    });
    static forAgentDir(agentDir: string, options?: {
        readOnly?: boolean;
    }): ObservationStore;
    private load;
    private save;
    /** Evict least-recently-incremented keys until the store is back within {@link MAX_KEYS}. */
    private evict;
    /**
     * Record one more observation of `key` and return the new (capped) count. Load-mutate-save runs
     * under a single exclusive lock so two concurrent increments (e.g. two reflection passes across
     * sessions sharing an agentDir) can't both read the old count and drop one increment.
     */
    increment(key: string, at?: string): number;
    /** Current observation count for `key` (0 if never observed). */
    get(key: string): number;
}
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