/**
 * Runtime detection and capability checking primitive.
 * This is the foundation for all environment-specific behavior.
 *
 * All utilities should use this module instead of directly checking
 * for process, window, Deno, etc.
 */
/**
 * Thrown by `runtime.exit(code)` in environments without process exit
 * (i.e. browsers). Carries the requested exit code on `.exitCode` so
 * outer error handlers can still report it.
 */
export declare class ProcessExitError extends Error {
    readonly exitCode: number;
    constructor(code: number);
}
interface RuntimeCapabilities {
    readonly isBrowser: boolean;
    readonly isWorkerd: boolean;
    readonly isNode: boolean;
    readonly isDeno: boolean;
    readonly isBun: boolean;
    canExit(): boolean;
    canReadEnv(): boolean;
    canWriteEnv(): boolean;
    canFileSystem(): boolean;
    canNetwork(): boolean;
    canCrypto(): boolean;
    exit(code: number): never;
    env(key: string): string | undefined;
    setEnv(key: string, value: string): void;
    deleteEnv(key: string): void;
    hasEnv(key: string): boolean;
    allEnv(): Record<string, string>;
    cwd(): string;
    entry(): string | undefined;
    stdout: {
        write(message: string): void;
        isTTY: boolean;
    };
    stderr: {
        write(message: string): void;
        isTTY: boolean;
    };
}
declare class RuntimeOps implements RuntimeCapabilities {
    readonly isBrowser: boolean;
    readonly isWorkerd: boolean;
    readonly isNode: boolean;
    readonly isDeno: boolean;
    readonly isBun: boolean;
    /** `process.env`: Node and Bun, and a Worker whose `nodejs_compat` puts its vars there. */
    private get processEnv();
    canExit(): boolean;
    canReadEnv(): boolean;
    canWriteEnv(): boolean;
    canFileSystem(): boolean;
    canNetwork(): boolean;
    canCrypto(): boolean;
    exit(code: number): never;
    env(key: string): string | undefined;
    setEnv(key: string, value: string): void;
    deleteEnv(key: string): void;
    hasEnv(key: string): boolean;
    allEnv(): Record<string, string>;
    cwd(): string;
    /**
     * The program's entry: the script's path or URL, else the executable
     * (a REPL, `node -e`). undefined in browsers and Workers, which have none.
     */
    entry(): string | undefined;
    get stdout(): {
        write: (message: string) => void;
        isTTY: boolean;
    };
    get stderr(): {
        write: (message: string) => void;
        isTTY: boolean;
    };
}
export declare const runtime: RuntimeOps;
export type { RuntimeCapabilities };
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