Starting a Subscription to AWS AppSync with AWS Cognito User Pool Authorization

Is there an existing issue for this?

• I have searched the existing issues

Product

Strawberry Shake

Describe the bug

I am using StrawberryShake.Blazor v13.4.0 as a client to an AWS AppSync GraphqlApi. Query components work and a subscription component is making a successful connection with AWS Cognito User Pool authorization, but the subscription “start” causes an UnsupportedOperation error.

This is the network log from my web browser.

{"type":"connection_init"}
{"type":"start","id":"c0931a4a-04f3-4c2b-8cde-ddbe6f4ff20b","payload":{"query":"subscription OnCreateAsset { onCreateAsset { __typename _deleted _version dateCreated dateModified id name } }","operationName":"OnCreateAsset"}}
{"type":"connection_ack","payload":{"connectionTimeoutMs":300000}}
{"type":"ka"}
{"type":"error","payload":{"errors":[{"errorType":"UnsupportedOperation","message":"unknown not supported through the realtime channel"}]}}

I know from a test in Postman that if I could configure my StrawberryShake WebSocket client to use the following format for a subscription “start” instead of the current format, the subscription registration would be successful.

{
    "type": "start",
    "id": "e6122ade-39a9-491c-ad57-09d9283324ea",
    "payload": {
        "data": "{\"query\":\"subscription OnCreateAsset { onCreateAsset { __typename _deleted _version dateCreated dateModified id name } }\"}",
        "extensions": {
            "authorization": {
                "Authorization": "jwt.jwt.jwt",
                "host": "abcdefghijklmnopqrstuvwxyz.appsync-api.us-east-1.amazonaws.com"
            }
        }
    }
}

AWS documentation for the subscription registration message format: https://docs.aws.amazon.com/appsync/latest/devguide/real-time-websocket-client.html#subscription-registration-message
AWS blog post for creating a Python client with real-time subscriptions : https://aws.amazon.com/blogs/mobile/appsync-websockets-python/

How do I configure my StrawberryShake WebSocket client to use the AWS AppSync graphql-ws protocol format?

No file or test is named. Start at Strawberry Shake's WebSocket subscription registration entry point and compare its start message with the AWS AppSync subscription-registration documentation and the provided network payload. Done means the client can register this Cognito-authorized subscription successfully using the required AppSync format.