A custom header has been set for an IIS 8 based site protected by a 12.52 Webagent (Build 142).
Although the header is defined in the response it is not passed to IIS. Legacy headers are also not passed to IIS however they are enabled in the ACO.
There may actually be several reasons for this not working, like incorrect directory mappings or agent name resolution, etc. I believe we would need the policy server trace showing the transaction not passing the headers, the webagent trace as well as a fiddler trace for this. Likely you may want to open a support case to have a more thorough investigation
1. Is the response getting triggered properly on PS side?
2. Was the website configured with CA SSO webagent configuration wizard or manually? Can u share applicationHost.config & web.config?
3. How are you reading headers?
4. Do you have any custom modules other than CA SSO configured in IIS?
5. Does it work in classic pipeline mode?
Upgrading webagent to 12.52 SP1 CR6 resolved issue.
Ah right, 12.52 base (build 142) does not support IIS 8.0.