/** Typed, runtime-neutral channel contracts. Durable replay, presence, fan-out, and tenant-aware
 * routing belong in an adapter; the bundled hub provides only bounded process-local replay for tests
 * and local development. */
export interface ChannelContract<Name extends string, Message> {
    readonly name: Name;
    /** Type-only message witness; adapters never materialize it. */
    readonly __message?: (value: Message) => Message;
}
export interface ChannelEvent<Message> {
    /** Monotonic within one channel; adapters may use a different opaque cursor representation. */
    readonly sequence: number;
    readonly resumeToken: string;
    readonly data: Message;
}
export type ChannelCloseReason = "closed" | "backpressure" | "aborted";
export interface ChannelSubscription<Message> extends AsyncIterableIterator<ChannelEvent<Message>> {
    readonly channel: string;
    readonly closed: boolean;
    readonly closeReason: ChannelCloseReason | undefined;
    readonly resumeToken: string | undefined;
    close(): void;
}
export interface ChannelSubscribeOptions {
    /** Maximum undelivered events retained for this subscriber. Default 64. */
    readonly maxQueue?: number;
    /** Resume after this opaque cursor. The adapter must fail closed when the cursor is unavailable. */
    readonly resumeFrom?: string;
    readonly signal?: AbortSignal;
}
export interface ChannelHub {
    subscribe<Name extends string, Message>(channel: ChannelContract<Name, Message>, options?: ChannelSubscribeOptions): ChannelSubscription<Message>;
    publish<Name extends string, Message>(channel: ChannelContract<Name, Message>, data: Message): ChannelEvent<Message>;
}
export interface MemoryChannelHubOptions {
    /** Default queue bound per subscriber. Default 64. */
    readonly maxQueue?: number;
    /** Maximum events retained per channel for local cursor replay. Default: the queue bound. */
    readonly historySize?: number;
}
/** A requested cursor is malformed, belongs to another channel, or fell outside retained history. */
export declare class ChannelResumeUnavailableError extends Error {
    readonly channel: string;
    readonly resumeToken: string;
    constructor(channel: string, resumeToken: string);
}
/** Define a typed channel name. Message types are erased; adapters own validation at their boundary. */
export declare function defineChannel<Name extends string, Message>(name: Name): ChannelContract<Name, Message>;
/** A bounded in-memory hub suitable for tests and local development, never for durable fan-out. */
export declare function memoryChannelHub(options?: MemoryChannelHubOptions): ChannelHub;
/** Adapt a channel subscription to a cancellable Web stream for SSE/HTTP adapters. */
export declare function channelReadableStream<Message>(subscription: ChannelSubscription<Message>): ReadableStream<ChannelEvent<Message>>;
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