After trying various workarounds based on reports of other software not working on macos 15.2 (e.g. java + docker sigkill https://github.com/corretto/corretto-21/issues/85, or the aforementioned Microsoft Defender issues. Many horror stories of various issues in the macadmins Slack), I downgraded to 14.7.2.
Now everything Docker->IRIS->wiremock works again. If you're reading this and are in a similar situation I would suggest avoiding mac os 15 for as long as possible
I launch our test suite from the IRIS terminal. I was demonstrating that the code used to create http requests is fairly generic and has worked previously. The subsequent individual tests on the IRIS server will test a variety of mocked endpoints, on both http and https ports on the Wiremock server. When tests are attempting to talk to any endpoint, on either http or https ports, the IRIS terminal returns the error which I posted.
I had already checked the SSL configuration from the management portal, and it is enabled on the IRIS server. The error persists, so I wanted to see if anyone else had the same issue.