Error model

All provider and native errors are normalized to a single ExpoAIError at the boundary, so app code handles one shape regardless of which adapter failed.

export class ExpoAIError extends Error {
  code: ExpoAIErrorCode;
  provider: ExpoAIProvider;
  retryable: boolean;
  fallbackRecommended: boolean;
  nativeMessage?: string;
}

export type ExpoAIErrorCode =
  | 'UNAVAILABLE'
  | 'UNSUPPORTED_DEVICE'
  | 'MODEL_NOT_READY'
  | 'MODEL_DOWNLOAD_REQUIRED'
  | 'USER_SETTING_REQUIRED'
  | 'INVALID_PROMPT'
  | 'CONTEXT_WINDOW_EXCEEDED'
  | 'SAFETY_BLOCKED'
  | 'RATE_LIMITED'
  | 'CANCELLED'
  | 'TIMEOUT'
  | 'NATIVE_PROVIDER_ERROR'
  | 'UNKNOWN';

• retryable tells the app whether trying again may succeed (e.g. AICore still initializing).
• fallbackRecommended signals that switching to another provider is the right recovery, which the router uses when fallback is allowed.
• nativeMessage preserves the original platform error for logging without leaking it into your normalized handling.