Should /callbacks/{localCallbackId} have expected callers?

[eric-schuh]

While going through #584 I noticed that the /callbacks/{localCallbackId} endpoint doesn't have any x-expectedCallers, it would seem that this endpoint is expected to be called by the party that received the callback endpoint as part of a particular exchange, and that this endpoint is expected to live on the Workflow Service.

This would add a new line to the Workflow Service component table that has:

##Workflow Service
Endpoint Expected Caller
/callbacks/{localCallbackId} The party that received the callback URL

If this is not where this endpoint should be indexed, where should it be, and is this correct for the expected caller? (maybe with better phrasing to shorten it)

[dlongley]

I struggled to understand the description above. I don't know what it means to "receive a callback endpoint". But here are some of my thoughts on callbacks:

The callback endpoint lives on a coordinator. It will usually be (but I suppose does not need to be) the same coordinator that created the exchange. This coordinator usually specifies the callback as a variable when creating the exchange (but, again, I suppose this could technically be done another way).

The workflow service is the entity that calls the callback URL -- whenever the exchange state changes -- to notify the coordinator that it might want to poll the exchange URL to get the updated exchange information.

[eric-schuh]

#591 was merged on 17/2/2026

[TallTed]

Best to get in the habit of using ISO notation for all-numeric dates, like 2026-02-17.