WCSession.sendMessage is crashing … | Apple Developer Forums

WCSession.sendMessage is crashing when a reply or error handler is attached, why?

The following code should send a message from the watch to the iPhone. Unfortunately, it is crashing. I have no clue why.

if WCSession.isSupported()
{
  let session = WCSession.default

  if ((session.activationState == .activated) && session.isReachable)
  {
    session.sendMessage(["SimpleMessages":["start"]],                                          replyHandler:{reply in
                                                     _ = 0
                                                    },
                            errorHandler:nil)
      }
    }

If the reply handler is set to nil, the code does not crash.

Anyway, in both cases the message is correctly sent from the watch to the phone.

The code itself is run on the main thread (verified).

I am running watchOS 26.6 and iOS 27.

Here is the crash :

Stack trace