/**
 * Global constants: default values, reserved prefixes, internal flags.
 */
export declare const DEFAULTS: {
    readonly HEARTBEAT_INTERVAL_MS: 30000;
    readonly HEARTBEAT_TIMEOUT_MS: 5000;
    readonly MAX_PENDING: number;
    readonly MAX_PAYLOAD_BYTES: number;
};
export declare const RESERVED_TYPE_PREFIXES: readonly ["__", "$"];
export declare const SYSTEM_MESSAGE_TYPES: {
    readonly HEARTBEAT: "__heartbeat";
    readonly HEARTBEAT_ACK: "__heartbeat_ack";
    readonly CLOSE: "__close";
};
export declare const RESERVED_META_KEYS: ReadonlySet<string>;
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