/**
 * Secret indirection for account credentials — keeps plaintext out of
 * config.toml. A config value may be:
 *
 *   • a plain string            → used as-is (backward compatible)
 *   • "keychain:<account>"      → macOS Keychain, service "email-mcp"
 *   • "keychain:<svc>/<account>"→ macOS Keychain, explicit service
 *   • "env:<VAR>"               → an environment variable
 *
 * The Keychain path shells out to the `security` CLI. Only the service and
 * account (non-secret identifiers) are ever passed as arguments — the secret
 * itself only ever travels back on the child's stdout, so nothing sensitive
 * reaches argv (visible via `ps`) or the logs. Multi-account falls out of the
 * Keychain's per-item `account` attribute: each account's secret is a distinct
 * generic-password item under the shared service.
 *
 * Writing a secret is deliberately NOT done here — see `account set-secret`,
 * which delegates entry to the `security` interactive prompt so the value is
 * never scripted into argv.
 */
/** Injectable reader: (command, args) => secret on stdout. */
export type SecretRunner = (command: string, args: string[]) => Promise<string>;
export interface ResolveOptions {
    runner?: SecretRunner;
    env?: Record<string, string | undefined>;
    /** Override the detected platform (testing / explicit control). */
    platform?: NodeJS.Platform;
}
/**
 * Resolve one config secret value. Plain strings pass through unchanged, so
 * existing plaintext configs keep working while new ones can point at the
 * Keychain or an environment variable.
 */
export declare function resolveSecret(value: string, opts?: ResolveOptions): Promise<string>;
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