/** stdout/stderr sinks, injected everywhere so tests capture output. */
export interface Io {
    /** Data channel — response bodies and JSON results ONLY. */
    out(line: string): void;
    /** Everything else: status lines, pair codes, errors, hints. */
    err(line: string): void;
}
export declare const EXIT: {
    readonly OK: 0;
    readonly USAGE: 1;
    readonly BRIDGE: 2;
    readonly BOTWALL: 3;
    readonly HTTP: 4;
};
/** Invalid invocation or profile state — maps to EXIT.USAGE. */
export declare class UsageError extends Error {
    readonly hint?: string;
    constructor(message: string, hint?: string);
}
export declare function printJson(io: Io, value: unknown): void;
/**
 * `--json` envelope for fetch verbs. The bridge returns `{status, url,
 * body}` — response headers never cross the protocol, and `body` is
 * always a UTF-8 string (the extension decodes it).
 */
export declare function fetchEnvelope(res: {
    status: number;
    url: string;
    body: string;
}): string;