You are mixing up the extension pubsub system with the “regular” Twitch Events pubsub.
An extension can listen on the extension pubsub for events sent by you from your EBS to you connected extension users.
Whispers/bits/commerce are on the “regular” pubsub and are seperate to the extension pubsub.
You shouldn’t be connecting to and listening on the channel-ext-v1 topic yourself. Hence there are not docs about connecting to Twitch PubSub to listen on this topic. As it’s not the correct route.
When you broadcast to the Extension pubsub it is private to the channel in question and only listened to by the users/viewers on that channel. (To do some any other way involves some jiggery pokery beyond ModestTim’s revealing of the Topic name)
Extension PubSub messages are delivered in real time, literally straight after you have emitted to the extensions PubSub transmit end point.
Sending Extension PubSub is documented:
And listening to those inside an Extension is documented:
This refers to “Regular” PubSub which you cannot transmit to, only listen on. And only for Topics such as Whispers and Bits that is documented:
Basically you have read a number of things on the forums and got yourself confused…