[macos 15.2 (24C101)] Custom input method does not work as expected

Environment: macOS 15.2 (24C101) with Xcode 16.2 (16C5032a)

Goal: I am trying to build a simple IMKInputController-based input method.

Problem: My .app bundle registers successfully and I can select it as an input source. When selected, it blocks keyboard input, but my handle method does not seem to execute or produce output. I have placed NSLog statements in my controller's init and handle methods.

Code for the controller:

import InputMethodKit

// The IMKTextInput protocol is provided by the framework.
// We don't need to define our own bridging protocol for this test.

public class HelloWorldController: IMKInputController {

    public override init!(server: IMKServer!, delegate: Any!, client inputClient: Any!) {
        super.init(server: server, delegate: delegate, client: inputClient)
        NSLog("HelloWorldIME: Controller has been initialized.")
    }

    public override func handle(_ event: NSEvent!, client sender: Any!) -> Bool {
        NSLog("HelloWorldIME: handle() method was called.")

        // ================== FINAL FIX APPLIED HERE ==================

        // 1. First, we ensure the client is a fundamental Objective-C object.
        guard let clientObject = sender as? NSObject else {
            NSLog("HelloWorldIME: Error - client object is not an NSObject.")
            return false
        }
        NSLog("HelloWorldIME: Successfully cast client to NSObject.")
        
        // 2. Now that we have an NSObject, we can safely check if it responds to the selector.
        let selector = #selector(IMKTextInput.insertText(_:replacementRange:))
        if !clientObject.responds(to: selector) {
             NSLog("HelloWorldIME: Error - client object does not respond to the insertText selector.")
             return false
        }
        NSLog("HelloWorldIME: Client responds to insertText. Preparing to insert text.")

        // 3. Since we've confirmed it responds, we can now safely treat it as an IMKTextInput
        //    and call the method.
        let client = clientObject as! IMKTextInput
        let stringToInsert = "A"
        let replacementRange = NSRange(location: NSNotFound, length: 0)
        
        client.insertText(stringToInsert, replacementRange: replacementRange)
        
        NSLog("HelloWorldIME: Called insertText with string '\(stringToInsert)'. Action complete.")

        // ========================================================

        return true
    }
}