mattonecz Thanks for posting your question in Microsoft Q&A. We do have a full sample BidirectionChat available for JS V4 model and this will help you get started with the migration. If you have any questions or face issues, feel free to reach out to us (with additional details like code snippet, config etc.) or open a new issue in https://github.com/aspnet/AzureSignalR-samples/issues related to SignalR samples.
Sorry about the documentation missing V4 samples and will pass on feedback internally to our doc team to update it. I hope this helps with your question.
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