Unlike SAML which shows the expiry date of the certificate, I couldn’t see the same for OIDC application. Can I assume the client secret never expires?
That’s correct, Client Secrets do not have a built in expiration date. However, if you do need or want to, it is still possible to rotate a client secret.
Great! just a follow up question - Does this holds true for API Service client secret as well?
Yup, its the same for API Service apps as well.