export declare function fetchLatestNpmVersion(fetchImpl?: typeof fetch, timeoutMs?: number): Promise<string | null>;
export type InstallChannel = "global-npm" | "npx" | "native" | "source" | "unknown";
export declare function detectInstallChannel(env?: NodeJS.ProcessEnv): InstallChannel;
export interface UpdatePromptInput {
    currentVersion: string;
    interactiveTty: boolean;
    outputMode: string;
    ci: boolean;
    command: string;
    channel: InstallChannel;
}
export declare function shouldShowUpdatePrompt(input: UpdatePromptInput): boolean;
/**
 * Maps a raw keypress byte sequence to an update prompt action.
 * Ctrl+C, Enter, and newline all map to "l" (Later) — they must never kill
 * the governed process. Only "y"/"Y" maps to "y" (Update now).
 */
export declare function classifyUpdateKey(key: string): "y" | "l";
/**
 * Returns [executable, args] for the npm global-update command on this platform.
 * On Windows, .cmd files cannot be spawned with shell:false — use ComSpec instead.
 * Exported for unit testing (pure function, no side effects).
 */
export declare function buildNpmUpdateCommand(env?: NodeJS.ProcessEnv): [string, string[]];
export declare function runNpmUpdate(): {
    success: boolean;
    error?: string;
};
/**
 * Shows the startup update prompt.
 * Returns:
 *   false     — prompt not shown (not a newer version, wrong channel, suppressed)
 *   "deferred" — prompt shown, user pressed L/Enter/timeout (original command continues)
 *   "updated"  — prompt shown, user pressed Y (update was attempted; do not continue original command)
 */
export declare function maybeShowUpdatePrompt(currentVersion: string, fetchImpl?: typeof fetch): Promise<false | "deferred" | "updated">;