When running an ASA Agent 12.8 for WebSphere, the ASA Agent catches the request, and after determining the resource being protected, it reports that it won't handle the request. As such, SSO doesn't occur.
asa.log:
[17 Aug 2022 10:48:10,161] [WebContainer : 68] [INFO] High Level Agent is checking if SiteMinder is the target interceptor for request /myApp.
[17 Aug 2022 10:48:10,165] [WebContainer : 68] [DEBUG] The Resource Manager is checking if resource /myApp is Protected.
[17 Aug 2022 10:48:10,180] [WebContainer : 68] [DEBUG] SiteMinder Resource Manager isProtected auth scheme = 1
[17 Aug 2022 10:48:10,180] [WebContainer : 68] [INFO] SM_WSH_00032 - The Resource Manager determined resource /myApp is Protected.
[17 Aug 2022 10:48:10,181] [WebContainer : 68] [DEBUG] SiteMinder HLA Resource Manager resolved resource context: /siteminderassertion
[17 Aug 2022 10:48:10,181] [WebContainer : 68] [DEBUG] The Resource Manager is checking if resource /siteminderassertion is Protected.
[17 Aug 2022 10:48:10,198] [WebContainer : 68] [DEBUG] SiteMinder Resource Manager isProtected auth scheme = 1
[17 Aug 2022 10:48:10,198] [WebContainer : 68] [INFO] SM_WSH_00032 - The Resource Manager determined resource /siteminderassertion is Protected.
[17 Aug 2022 10:48:10,199] [WebContainer : 68] [DEBUG] SiteMinder HLA Resource Manager processResource session cookie = false, challenge cookie = false, schemeId = 1
[17 Aug 2022 10:48:10,199] [WebContainer : 68] [INFO] High Level Agent not intercepting for request /myApp.
[17 Aug 2022 10:48:10,199] [WebContainer : 68] [INFO] The SiteMinder TAI will not intercept request URL https://_host._domain._com/myApp.
[17 Aug 2022 10:48:10,199] [WebContainer : 68] [DEBUG] SiteMinder HLA Resource Manager processResource session cookie = false, challenge cookie = false, schemeId = 1
[17 Aug 2022 10:48:10,199] [WebContainer : 68] [INFO] High Level Agent not intercepting for request /myApp.
[17 Aug 2022 10:48:10,199] [WebContainer : 68] [INFO] The SiteMinder TAI will not intercept request URL https://_host._domain._com/myApp.
ASA Agent 12.8 on WebSphere ND 8.5.5.21 on RedHat 7;
Web Agent 12.52SP1CR0 on Front End IHS 8.5.5 on RedHat 7;
Upgrade the ASA Agent for WebSphere 12.8SP1 when this one will be available to benefit from the fix from DE506122.