I have:

withContext(<http://Dispatchers.IO|Dispatchers.IO>) {
            when (event) {
                is Event.Comment -> response.write("")
                else -> TODO()
            }
        }

and intellij is complaining that

Writer#write

is blocking, even though I clearly swapped over to IO

... actually, expanding my youtrack search has turned up https://youtrack.jetbrains.com/issue/KT-39684, which is probably related