/** A migration stage is deliberately JSON-like so it can be unit-tested offline. */
export type SettingsMigrationRecord = Record<string, unknown>;
/**
 * The first persisted settings shape had no schemaVersion. It was the flat
 * config shape, followed by a short-lived grouped shape at the top level.
 */
export declare function migrateV1ToV2(raw: unknown): SettingsMigrationRecord;
/** V3 added the fixed Tencent Cloud slot while retaining the V2 language field. */
export declare function migrateV2ToV3(raw: unknown): SettingsMigrationRecord;
/**
 * V4 split the global language into browser/local/provider fields. The old
 * global value is intentionally discarded, as recorded by D-042.
 */
export declare function migrateV3ToV4(raw: unknown): SettingsMigrationRecord;
/** Apply only the migrations known by this package; future versions are normalized conservatively. */
export declare function migrateSettingsToCurrent(raw: unknown): SettingsMigrationRecord;