I’m working on a launch daemon. I’m in the process of adding setCodeSigningRequirement to both sides of the connection, starting with the XPC service. I’ve already made it so that the service calls setCodeSigningRequirement on a new connection passed to the listener method of NSXPCListenerDelegate. It works and the connection does get invalidated. The launch daemon logs stdout and stderr to a file already. So I figured that if a connection gets invalidated because of a code signing failure, it’d be nice to NSLog this to make it easier for users to debug what’s going on, without forcing them to use Console.app. The docs for setCodeSigningRequirement include an example of how to capture this error on the client side, when the client calls that method. What I cannot figure out is how to capture this error on the side of the XPC service. I could use setInvalidationHandler, but the problem with it is that a connection can be invalidated for a myriad of reasons and the handler doesn’t know what happened. Is there perhaps an equivalent of remoteObjectProxyWithErrorHandler but for the service side of the connection?