Playing audio live from Bluetooth headset on iPhone speaker

Hi guys,

I am having issue in live-streaming audio from Bluetooth headset and playing it live on the iPhone speaker.

I am able to redirect audio back to the headset but this is not what I want.

The issue happens when I am trying to override output - the iPhone switches to speaker but also switches a microphone.

This is example of the code:

import AVFoundation

class AudioRecorder {
    let player:  AVAudioPlayerNode
    let engine:AVAudioEngine
    let audioSession:AVAudioSession
    let audioSessionOutput:AVAudioSession
    
    init() {
        self.player = AVAudioPlayerNode()
        self.engine = AVAudioEngine()
        self.audioSession = AVAudioSession.sharedInstance()
        self.audioSessionOutput = AVAudioSession()
        do {
            try self.audioSession.setCategory(AVAudioSession.Category.playAndRecord, options: [.defaultToSpeaker])
            try self.audioSessionOutput.setCategory(AVAudioSession.Category.playAndRecord, options: [.allowBluetooth]) // enables Bluetooth HFP profile
            try self.audioSession.setMode(AVAudioSession.Mode.default)
            try self.audioSession.setActive(true)
            // try self.audioSession.overrideOutputAudioPort(.speaker) // doens't work
        } catch {
            print(error)
        }
        
        let input = self.engine.inputNode
        self.engine.attach(self.player)
        let bus = 0
        let inputFormat = input.inputFormat(forBus: bus)
        self.engine.connect(self.player, to: engine.mainMixerNode, format: inputFormat)
        input.installTap(onBus: bus, bufferSize: 512, format: inputFormat) { (buffer, time) -> Void in
            self.player.scheduleBuffer(buffer)
           print(buffer)
        }
    }
    
    public func start() {
        try! self.engine.start()
        self.player.play()
    }
    
    public func stop() {
        self.player.stop()
        self.engine.stop()
        
    }
}

I am not sure if this is a bug or not.

Can somebody point me into the right direction? I there a way to design a custom audio routing?

I would also appreciate some good documentation besides AVFoundation docs.