export interface ExecShellPlanOptions {
    /**
     * Injected in tests; defaults to the real filesystem. This is the only
     * injection point on the Windows path — the interpreter PATH itself is a
     * constant (WINDOWS_POWERSHELL_PATH) and deliberately cannot be overridden,
     * by a test or by anything else.
     */
    exists?: (candidate: string) => boolean;
}
/**
 * The result of planning.
 *
 * `posixShell` is what to hand Node's spawn `shell` option on POSIX (`true` =
 * /bin/sh, a path = that interpreter). It is always `true` and always IGNORED on
 * Windows, where nothing is spawned through a shell at all: the command goes to
 * the signed launcher, which runs cmd.exe itself.
 *
 * `command` is the text to run. Only the Windows PowerShell path rewrites it;
 * every other path hands back exactly what it was given.
 *
 * `clixmlStderr` says the stderr of the resulting process needs the PowerShell
 * CLIXML decoder (powershell-clixml.ts) in front of it. It is set on exactly ONE
 * path — the -EncodedCommand wrapping below — because the CLIXML is a side effect
 * of that wrapping and of nothing else. It travels on the plan rather than being
 * re-derived from `shell` in executor.ts so that the decision stays where the
 * wrapping decision is: change the wrapping here and the flag changes with it,
 * instead of a second file quietly disagreeing about which commands were
 * wrapped. cmd, sh and bash never carry it and their stderr is byte-identical to
 * what it was before this existed.
 */
export type ExecShellPlan = {
    ok: true;
    command: string;
    posixShell: true | string;
    clixmlStderr?: true;
} | {
    ok: false;
    message: string;
};
/**
 * Resolve a requested shell for THIS machine.
 *
 * `shell` arrives off a relay frame, so it is treated as untrusted input: an
 * unknown string, or one belonging to the other platform family, is refused
 * with the same message the relay would have produced. `undefined` is the
 * documented "machine default" and is the only value that changes nothing.
 */
export declare function planExecShell(platform: NodeJS.Platform | string, shell: string | undefined, command: string, options?: ExecShellPlanOptions): ExecShellPlan;