/** Thrown when AICOMMANDER_CONFIG_DIR is set to a path we cannot store into. */
export declare class ConfigDirError extends Error {
    constructor(message: string);
}
/**
 * Optional override for the durable identity/session directory.
 *
 * `device.ts` and `session-store.ts` default to /etc with a ~/.config fallback,
 * which assumes /etc survives a reboot. That is not universally true: QNAP QTS
 * rebuilds its whole root filesystem — /etc, /var/run and /usr/local alike —
 * from a ramdisk on every boot, and some container images are equally volatile.
 * An agent persisting its identity there comes back from a restart with a NEW
 * session code and no linked accounts.
 *
 * Setting AICOMMANDER_CONFIG_DIR points both stores at durable storage instead
 * (on QNAP, a directory on the data volume). It is consulted only when no
 * explicit `configDir` was passed — the desktop app's per-user data dir still
 * wins — so leaving it unset preserves the existing behaviour exactly.
 *
 * An EMPTY or whitespace-only value is treated as unset (the defaults apply):
 * `AICOMMANDER_CONFIG_DIR=` and an absent variable are the same statement of
 * intent from a shell or a service wrapper, and wrappers that build the value can
 * legitimately end up with an empty string. A NON-blank but unusable value
 * THROWS instead of falling back to the defaults. Every other
 * store failure in this package has a safe fallback (/etc → ~/.config); this one
 * does not: silently reverting to a volatile /etc is precisely the "new device id
 * and new session code on every restart" failure the override exists to prevent,
 * and nothing downstream would report it (`loadOrCreateDevice` returns an
 * in-memory identity, `saveSession` no-ops outside strict mode). We deliberately
 * do NOT gate this on `isStrictCredentialStorage()`: the QNAP service that needs
 * the override most is not a systemd unit, so it would land in the quiet branch.
 */
export declare function envConfigDir(): string | undefined;