/** True when the host OS supports the Keychain backend. Only macOS for now.
 *  Honours `CLAUDE_SWITCH_DISABLE_KEYCHAIN=1` so the test suite (and any
 *  user who explicitly opts out) keeps the JSON-only behaviour. The env
 *  var is read on every call — tests flip it per-suite. */
export declare function keychainAvailable(): boolean;
/** Read an API key from the Keychain. Returns null if absent or on
 *  non-macOS. Does NOT throw on missing entries (the common case). */
export declare function readApiKeyFromKeychain(email: string): string | null;
/** Write an API key to the Keychain. Throws on macOS errors so the
 *  caller can surface them; no-op on non-macOS so callers can call
 *  unconditionally and only fall through to JSON when this returns false. */
export declare function writeApiKeyToKeychain(email: string, key: string): boolean;
/** Delete an API key from the Keychain. Returns true if an entry was
 *  removed, false if it didn't exist. No-op on non-macOS. */
export declare function deleteApiKeyFromKeychain(email: string): boolean;