Prevent NSApp from autoloading a nib at launch.

main.m

#import <objc/runtime.h>

int main(int argc, char *argv[])
{
  Class bundle = [NSBundle class];
  method_exchangeImplementations(
    class_getClassMethod(bundle, @selector(loadNibNamed:owner:)),
    class_getClassMethod(bundle, @selector(stopAuto_loadNibNamed:owner:))
  );

  // ... rest of main, probably just NSApplicationMain()
}

NSBundle+StopAutoloadingNibs.m

#import <Foundation/Foundation.h>


// NSApplication has this weird habit of trying very hard to load a nib at 
// launch. If there are none in the app bundle, it'll wander off into the 
// frameworks until it finds one, then try to use it.
//
// You know this is what's happening if you get four log messages at launch 
// saying "Could not connect the action buttonPressed: to target of class 
// NSApplication". You've deleted MainMenu.nib and removed the "Main nib file 
// base name" item from Info.plist, but you get these weird messages.
// 
// This category implements a replacement for +loadNibNamed:owner: that will 
// silently swallow this misguided attempt at autoloading a nib, but pass the 
// rest along.
@implementation NSBundle (StopAutoLoadingNibs)

// Calling this method without monkeypatching will result in an infinite loop.
+ (BOOL)stopAuto_loadNibNamed:(NSString *)nibName owner:(id)owner
{
  if (nibName == nil && owner == NSApp)
    // Fake a load.
    return YES;
  else
    // This is not an infinite loop! This method is assumed to be monkeypatched, 
    // so this message gets handled by the original implementation.
    return [self stopAuto_loadNibNamed:nibName owner:owner];
}

@end

Thanks a bunch!