- CloudConnectionError(reason=) defined in this module — token_expired | invalid_grant
- All 7 StorageBackend methods implemented as async coroutines
- Every sync googleapiclient call wrapped in asyncio.to_thread() (Pitfall 7)
- cache_discovery=False on build() prevents /tmp directory traversal (T-05-03-05)
- presigned_get_url and generate_presigned_put_url raise NotImplementedError (D-14)
- HttpError 401 raises CloudConnectionError(reason='token_expired')
- HttpError 400 with 'invalid_grant' raises CloudConnectionError(reason='invalid_grant')
- HttpError 404 on delete_object is silently swallowed (no-op per contract)
- Backend is stateless — no DB writes (B2 design, D-05/D-06)
curo1305