/**
 * Subject Store — SDK-managed identity selection & namespaced cache
 * ---------------------------------------------------------------
 * - Keeps track of the current subject (opaque id + metadata)
 * - Namespaces grant/audit/session caches per subject
 * - Provides TTL-aware get/set/del on top of any async key-value storage
 * - Emits 'subject_changed' so apps/agents can react
 */
export type Subject = {
    id: string;
    displayName?: string;
    avatarUrl?: string;
    subject?: string;
};
export type AsyncKV = {
    get(key: string): Promise<string | null>;
    set(key: string, val: string, ttlSec?: number): Promise<void>;
    del(key: string): Promise<void>;
};
export declare class SubjectStore {
    private kv;
    private emitter;
    private current;
    private keySubjects;
    private keyCurrent;
    constructor(kv: AsyncKV);
    onSubjectChanged(cb: (s: Subject | null) => void): () => void;
    getSubject(): Promise<Subject | null>;
    setSubject(subject: Subject): Promise<Subject>;
    ensureSubject(pick: () => Promise<Subject>): Promise<Subject>;
    switchSubject(id: string): Promise<Subject>;
    listSubjects(): Promise<Subject[]>;
    saveSubject(s: Subject): Promise<void>;
    removeSubject(id: string): Promise<void>;
    nsKey(subjId: string, key: string): string;
    nsGet(subjId: string, key: string): Promise<string | null>;
    nsSet(subjId: string, key: string, val: string, ttlSec?: number): Promise<void>;
    nsDel(subjId: string, key: string): Promise<void>;
    curGet(key: string): Promise<string | null>;
    curSet(key: string, val: string, ttlSec?: number): Promise<void>;
    curDel(key: string): Promise<void>;
    private setCurrent;
    private getSubjectById;
}
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