/**
 * Lessons: the curated, one-line-per-rule index of what went wrong and what
 * to do instead (T13949, owner decision D11181).
 *
 * A lesson is an observation of type `lesson`: the title holds the one-line
 * rule and the narrative holds why (the incident). Process lessons default to
 * the global (main) brain so every project and device reads them. The index
 * lists current lessons newest first; an invalidated (superseded) lesson is
 * hidden.
 *
 * Code placed in `packages/core/` per Package-Boundary Check — verified against AGENTS.md.
 *
 * @module memory/lessons
 * @task T13949
 */
/** Longest one-line rule a lesson title may hold. */
export declare const LESSON_RULE_MAX = 200;
/** Which store a lessons read covers. */
export type LessonScope = 'project' | 'global' | 'all';
/** One row of the lessons index. */
export interface LessonEntry {
    /** Observation id. */
    id: string;
    /** The one-line rule (the observation title). */
    rule: string;
    /** Why: the incident behind the rule (the observation narrative). */
    why: string;
    /** Creation time, SQLite `datetime` shape. */
    createdAt: string;
    /** Store the lesson lives in. */
    scope: 'project' | 'global';
}
/**
 * Validate the one-line rule of a lesson before it is stored.
 *
 * @param title - The proposed rule; required for a lesson.
 * @returns An error message, or `null` when the rule is acceptable.
 * @example
 * ```ts
 * lessonRuleError('Run biome on the exact changed files before push'); // null
 * ```
 */
export declare function lessonRuleError(title: string | undefined): string | null;
/**
 * List current lessons, newest first, from the project brain, the global
 * (main) brain, or both.
 *
 * With scope `all` each store is read on its own: a store that fails is
 * reported to `onStoreError` and the other store's lessons are still listed.
 * When every store fails the call throws one error naming each store's cause,
 * and `onStoreError` is not called.
 *
 * @param projectRoot - Project whose brain is read for `project` / `all`.
 * @param options - `scope` (default `all`), `limit` (default 50) and
 *   `onStoreError`, told which store failed under scope `all`.
 * @returns Lessons merged across the requested stores, newest first.
 * @example
 * ```ts
 * const lessons = await listLessons(root, { scope: 'all', limit: 20 });
 * ```
 */
export declare function listLessons(projectRoot: string, options?: {
    scope?: LessonScope;
    limit?: number;
    onStoreError?: (scope: 'project' | 'global', error: Error) => void;
}): Promise<LessonEntry[]>;
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