/** Metadata key under which a method's @OnDiagnostic subscriptions accumulate. */
export declare const ON_DIAGNOSTIC_META: unique symbol;
/** One subscription declared on a method. `event` omitted = every event of `lib`. */
export interface OnDiagnosticMeta {
    lib: string;
    event?: string;
}
/**
 * Subscribe a provider method to a diagnostics channel. Requires
 * `DiagnosticsModule.forRoot()` to be imported so the explorer wires it up.
 *
 * - `@OnDiagnostic('resilience', 'circuit-opened')` — the exact channel.
 * - `@OnDiagnostic('resilience')` — every `aviary:resilience:*` channel (current + future).
 *
 * Stackable: apply more than once to react to several channels with one method.
 */
export declare function OnDiagnostic(lib: string, event?: string): MethodDecorator;
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