diff --git a/test/test_token_refresh.py b/test/test_token_refresh.py
new file mode 100644
index 000000000..bcee5d194
--- /dev/null
+++ b/test/test_token_refresh.py
@@ -0,0 +1,47 @@
+"""Regression test for #2110: background token refresh thread must survive
+authlib OAuthError (e.g. invalid_grant), not just httpx.HTTPError."""
+
+import pytest
+from authlib.common.errors import AuthlibBaseError
+from httpx import HTTPError
+
+
+def test_authlib_base_error_is_not_http_error():
+    """AuthlibBaseError does NOT inherit from httpx.HTTPError, confirming
+    the bug: the old `except HTTPError` clause could never catch it."""
+    assert not issubclass(AuthlibBaseError, HTTPError)
+
+
+def test_authlib_base_error_caught_by_fixed_except_clause():
+    """The fixed except clause `(HTTPError, AuthlibBaseError)` must catch
+    authlib protocol-level errors like invalid_grant."""
+    try:
+        raise AuthlibBaseError("invalid_grant")
+    except (HTTPError, AuthlibBaseError):
+        pass  # This is what the fixed code does
+    else:
+        pytest.fail("AuthlibBaseError was not caught by (HTTPError, AuthlibBaseError)")
+
+
+def test_http_error_still_caught_by_fixed_except_clause():
+    """The fix must not break the existing HTTPError handling."""
+    try:
+        raise HTTPError("connection reset")
+    except (HTTPError, AuthlibBaseError):
+        pass
+    else:
+        pytest.fail("HTTPError was not caught by (HTTPError, AuthlibBaseError)")
+
+
+def test_oauth_error_subclass_caught():
+    """Concrete authlib errors (e.g. OAuthError) inherit from AuthlibBaseError
+    and must also be caught."""
+    from authlib.integrations.base_client.errors import OAuthError
+
+    assert issubclass(OAuthError, AuthlibBaseError)
+    try:
+        raise OAuthError("invalid_grant")
+    except (HTTPError, AuthlibBaseError):
+        pass
+    else:
+        pytest.fail("OAuthError was not caught by (HTTPError, AuthlibBaseError)")
diff --git a/weaviate/connect/v4.py b/weaviate/connect/v4.py
index d70bfc77b..c887baaa7 100644
--- a/weaviate/connect/v4.py
+++ b/weaviate/connect/v4.py
@@ -23,6 +23,7 @@
 )
 
 import grpc
+from authlib.common.errors import AuthlibBaseError  # type: ignore
 from authlib.integrations.httpx_client import (  # type: ignore
     AsyncOAuth2Client,
     OAuth2Client,
@@ -591,8 +592,10 @@ def periodic_refresh_token(refresh_time: int, _auth: Optional[_Auth]) -> None:
                         # saved credentials
                         refresh_session()
                     refresh_time = update_refresh_time()
-                except HTTPError as exc:
+                except (HTTPError, AuthlibBaseError) as exc:
                     # retry again after one second, might be an unstable connection
+                    # or an OAuth2 protocol-level rejection (e.g. invalid_grant
+                    # from authlib) — neither should kill the refresh thread (#2110)
                     refresh_time = 1
                     _Warnings.token_refresh_failed(exc)