The issue is solved with Spring Boot 3.0.1!

Steps to reproduce the issue

• build the project and run it
• open http://localhost:8082/graphiql
• authenticate with admin/admin
• execute test query to check it works

query {
  testQuery
}

• execute subscription

subscription {
  getNewPost{
    id
    title
    author {
      id
      name
    }
  }
}

• open another graphiql editor in new tab
• execute mutation

mutation {
  createPost(createPostInput: {
    title: "Lorem Ipsum"
    authorId: "123"
  }){
    id
    title
    author {
      name
    }
  }
}

• note that subscription received the response
• at this point authentication is lost and following request will be redirected to login page

Notes

• In case that Post object doesn't contain nested Author object, everything works as it should
• With Java Kickstart (code is here but commented out) everything works as it should
• With Spring Boot 3.0.0 /graphql calls get redirected to login page

Links

• Similar issue: graphql-java/graphql-java-spring#8