Description of problem: This started after upgrade from 16.2.0 to 16.2.2 while migrating from custom config to the feature described in [1]. We had fully functional openid federation with many associated groups per user before the upgrade. We have reverted the custom config and use 'keystone::federation::openidc::openidc_response_mode: "form_post"' in env-params.yaml. [1] 16.2.2 is out and puppet-keystone-15.5.0-2.20211125004854.337022a.el8ost contains 2021-11-24 OSP Prod Chain <dev-null> 15.5.0-2.20211125004854.337022a - Update patches - OIDC: Add support for setting OIDCResponseMode <====== - Add oidc options Version-Release number of selected component (if applicable): OSP 16.2.2 How reproducible: always Steps to Reproduce: 1. Login using openid wqith 5 groups 2. 3. Actual results: Failed to authenticate Expected results: no auth errors