/**
 * The message shape on a `chrome.runtime.Port` between the page, the
 * extension's background and its panel: a channel name and its payload.
 * Kept apart from `port-link.ts`, which pulls in the whole devframe, so the
 * background worker can share the guard without bundling it.
 */
/** The structural slice of `chrome.runtime.Port` used here. */
export interface PortLike {
    postMessage(message: unknown): void;
    onMessage: {
        addListener(callback: (message: unknown) => void): void;
    };
    onDisconnect?: {
        addListener(callback: () => void): void;
    };
}
/** What travels on the port, in both directions. */
export interface PortMessage {
    channel: string;
    data?: unknown;
}
export declare const isPortMessage: (message: unknown) => message is PortMessage;
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