From 3bbd567a1a0020a5c5962dd9032def0399ee6fca Mon Sep 17 00:00:00 2001
From: Hamza Imran <hamza135252@gmail.com>
Date: Sun, 1 Nov 2026 17:28:02 +0500
Subject: [PATCH] fix(vertex_ai): map google.auth TransportError to
 APIConnectionError (#49419)

---
 .../exception_mapping_utils.py                | 21 +++++++++++++
 .../test_exception_mapping_utils.py           | 31 +++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/litellm/litellm_core_utils/exception_mapping_utils.py b/litellm/litellm_core_utils/exception_mapping_utils.py
index 85c232ad3f4..1e5fc501464 100644
--- a/litellm/litellm_core_utils/exception_mapping_utils.py
+++ b/litellm/litellm_core_utils/exception_mapping_utils.py
@@ -1272,6 +1272,27 @@ def _map_vertex_exception(
 ) -> None:
     status_code: Final[object] = getattr(original_exception, "status_code", None)
     body_code: Final[int | None] = _get_body_error_code(error_str)
+    if (
+        exception_type == "TransportError"
+        or "TransportError" in type(original_exception).__name__
+        or "google.auth.exceptions.TransportError" in str(type(original_exception))
+    ):
+        raise APIConnectionError(
+            message=f"{custom_llm_provider.capitalize()}Exception - Authentication TransportError: {error_str}",
+            llm_provider=custom_llm_provider,
+            model=model,
+            litellm_debug_info=extra_information,
+        )
+    if (
+        exception_type in ("RefreshError", "GoogleAuthError", "DefaultCredentialsError")
+        or "google.auth.exceptions" in str(type(original_exception))
+    ):
+        raise AuthenticationError(
+            message=f"{custom_llm_provider.capitalize()}Exception - Authentication Error: {error_str}",
+            llm_provider=custom_llm_provider,
+            model=model,
+            litellm_debug_info=extra_information,
+        )
     if "Vertex AI API has not been used in project" in error_str or "Unable to find your project" in error_str:
         raise BadRequestError(
             message=f"litellm.BadRequestError: {custom_llm_provider}Exception - {error_str}",
diff --git a/tests/unit/litellm_core_utils/test_exception_mapping_utils.py b/tests/unit/litellm_core_utils/test_exception_mapping_utils.py
index 2b1e4a5eed3..ca18c3bdb17 100644
--- a/tests/unit/litellm_core_utils/test_exception_mapping_utils.py
+++ b/tests/unit/litellm_core_utils/test_exception_mapping_utils.py
@@ -772,6 +772,37 @@ def test_vertex_wrapped_500_with_body_code_403_maps_to_bad_request() -> None:
     assert excinfo.value.status_code == 403
 
 
+def test_vertex_auth_transport_error_maps_to_api_connection_error() -> None:
+    import google.auth.exceptions
+    original_exception = google.auth.exceptions.TransportError("Socket timeout")
+
+    with pytest.raises(litellm.APIConnectionError) as excinfo:
+        exception_type(
+            model="gemini/gemini-2.5-flash",
+            original_exception=original_exception,
+            custom_llm_provider="vertex_ai",
+        )
+
+    assert isinstance(excinfo.value, litellm.APIConnectionError)
+    assert "Authentication TransportError" in str(excinfo.value)
+    assert "https://github.com/BerriAI/litellm/issues/new" not in str(excinfo.value)
+
+
+def test_vertex_auth_refresh_error_maps_to_authentication_error() -> None:
+    import google.auth.exceptions
+    original_exception = google.auth.exceptions.RefreshError("Token has been expired or revoked")
+
+    with pytest.raises(litellm.AuthenticationError) as excinfo:
+        exception_type(
+            model="gemini/gemini-2.5-flash",
+            original_exception=original_exception,
+            custom_llm_provider="vertex_ai",
+        )
+
+    assert isinstance(excinfo.value, litellm.AuthenticationError)
+    assert excinfo.value.status_code == 401
+
+
 class TestGetBodyErrorCode:
     """Unit tests for _get_body_error_code helper."""