const STARTUP_CAUSES = new Set([
  "auth_config_invalid",
  "auth_session_store_invalid",
  "workspace_registry_invalid",
]);

const EXACT_CAUSES = new Map([
  ["authentication configuration is invalid", "auth_config_invalid"],
  ["authentication session state is invalid", "auth_session_store_invalid"],
  ["workspace registry configuration is invalid", "workspace_registry_invalid"],
]);

/** Return one bounded machine cause; never include the original error text or stack. */
export function formatStartupFailure(error: unknown): string {
  const message = error instanceof Error ? error.message : "";
  const cause = STARTUP_CAUSES.has(message) ? message : EXACT_CAUSES.get(message) ?? "startup_unknown";
  return `backend startup failed: ${cause}`;
}