How is Dispatchers.Unconfined implemented and on which threads does it execute tasks?

Dispatchers.Unconfined in Kotlin Coroutines is a dispatcher that starts a coroutine in the current thread until the first suspension. After resumption, the coroutine continues execution in the thread or context where it was resumed.

That is, when launching a coroutine with Dispatchers.Unconfined, it runs in the same thread where it was started, without switching to any specific thread (for example, UI or background). But upon resumption after suspension, execution may switch to another thread, depending on where the resumption occurred.

This makes Unconfined useful for certain cases where strict thread confinement is not necessary, such as testing or for coroutines that do not depend on a specific thread.

Example:

launch(Dispatchers.Unconfined) {
    println("Start in thread: ${Thread.currentThread().name}")
    delay(100) // suspension
    println("Resume in thread: ${Thread.currentThread().name}")
}

The output may show that the initial execution and resumption occur in different threads.

Important: Dispatchers.Unconfined is not suitable for UI updates, as it does not guarantee execution on the main thread.