Accept-patch header is missing in the response for the OPTIONS request if the target resource class supports PATCH.
rfc5789 says:

"Accept-Patch SHOULD appear in the OPTIONS response for any resource that supports the use of the PATCH method. The presence of the Accept-Patch header in response to any method is an implicit indication that PATCH is allowed on the resource identified by the Request-URI."

Example of the expected response for the OPTIONS request:

HTTP/1.1 200 OK
   Allow: GET, PUT, POST, OPTIONS, HEAD, DELETE, PATCH
   Accept-Patch: application/example, text/example

Test: https://github.com/resteasy/Resteasy/pull/1437/files#diff-7fc162ad4df364a9f363c8fc7323153aR104
Note: Please remove '@Category(ExpectedFailing.class)' line from test once fixed.