macOS app that works as both commandline and GUI app, how can I suppress system log output to stderr?

Question

I'm an old programmer teaching myself macOS and making tools for my own use.

I've got an app working that launches a GUI conditionally, but when it launches the GUI, the system prints logging info to stderr. How can I prevent that programmatically?

I'm launching the GUI like this:

    NSApplication.shared.run()

And the logging info I don't want that is coming from the OS looks like this:

1   HIToolbox       0x00000001902e05c8 _ZN15MenuBarInstance22EnsureAutoShowObserverEv + 120
2   HIToolbox       0x00000001902e0188 _ZN15MenuBarInstance14EnableAutoShowEv + 60
3   HIToolbox       0x0000000190283310 SetMenuBarObscured + 372
4   HIToolbox       0x0000000190282ee8 _ZN13HIApplication15HandleActivatedEP14OpaqueEventRefhP15OpaqueWindowPtrh + 172
5   HIToolbox       0x000000019027cfcc _ZN13HIApplication13EventObserverEjP14OpaqueEventRefPv + 296
6   HIToolbox       0x0000000190243cd0 _NotifyEventLoopObservers + 176
7   HIToolbox       0x000000019027c96c AcquireEventFromQueue + 432
8   HIToolbox       0x000000019026be0c ReceiveNextEventCommon + 712
9   HIToolbox       0x000000019026bb2c _BlockUntilNextEventMatchingListInModeWithFilter + 72
10  AppKit          0x0000000189e18424 _DPSNextEvent + 632
11  AppKit          0x0000000189e175b4 -[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 728
12  AppKit          0x0000000189e0b9e4 -[NSApplication run] + 464
13  macos-cond-gui  0x0000000104cd0764 main + 2148
14  dyld            0x000000018678fe50 start + 2544

I've tried setting the environment variable OS_ACTIVITY_MODE to disable, but this makes no difference. I verify in my code that it can see that it's set. Could it be that app.run() creates a new process that doesn't have the same env vars?

I realize I can redirect stderr. I'm looking for a programmatic solution so the app doesn't force this onto the user. I also will want to output my own messages to stderr that I won't want hidden.