I have a working version of using an apex continuation in a VF page for parallel and chained callouts. Now I need to use a continuation from a Lightning Component so I implemented the Continuation Proxy component from the Salesforce Developers Blog. I can attach multiple HTTP requests to the continuation and I have confirmed all requests reach my server and complete successfully. I have confirmed the continuation calls my callback method.

In the callback method, Continuation.getResponse(requestlabel) always returns null. requestlabel has a valid value too, "Continuation-1".

I have tested the ContinuationProxy in a lightning component app and on a record detail page.

Has anyone seen this before or can help me in the right direction?

@RemoteAction
global static Object invoke(String methodName, String[] params) {

    // Create a Continuation for the HTTPRequest        
    Continuation con = new Continuation(60);
    con.continuationMethod = 'callback'; 

    ...
    //Add http request to continuation

    return con;
}

global static Object callback(list<string> labels, Object state) {
    system.debug(labels);       
    for (string l : labels) {
        system.debug(l);
        HttpResponse response = Continuation.getResponse(l);
        system.debug(response);            
    }
    
    ...
}

13:53:04.0 (1053483)|USER_DEBUG|[160]|DEBUG|(Continuation-1)
13:53:04.0 (1143478)|USER_DEBUG|[162]|DEBUG|Continuation-1
13:53:04.0 (1235817)|USER_DEBUG|[164]|DEBUG|null