fix(connect): catch authlib OAuthError in background token refresh thread

The periodic_refresh_token daemon thread only caught httpx.HTTPError.
When the identity provider rejects a refresh at the OAuth2 protocol
level (e.g. Keycloak returns 400 invalid_grant due to token rotation,
reuse, revocation, or session expiry), authlib raises OAuthError which
inherits from AuthlibBaseError — NOT from httpx.HTTPError. The uncaught
exception killed the daemon thread silently, permanently breaking the
connection's ability to refresh tokens (#2110).

Add AuthlibBaseError to the except clause so both transport-level
(HTTPError) and protocol-level (OAuthError) failures are caught,
warned, and retried after 1 second.

Adds test/test_token_refresh.py with 4 tests verifying:
- AuthlibBaseError is NOT a subclass of HTTPError (confirms the bug)
- The fixed except clause catches AuthlibBaseError
- HTTPError is still caught (no regression)
- Concrete OAuthError subclass is also caught

Fixes #2110

Author: Solaris-star

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)")

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)