My team just upgraded from 3.20.1 to 3.29.0 and we are now running into problems because CosmosOperationCanceledException no longer works with the Microsoft Orleans binary serializer.

Azure-sdk-for-net ran into this same issue a few years ago, and solved it by implementing Serializable on their Exception classes.

It's a best practice to always make Exception classes Serializable. Without this, my team has to work around the issue by catching all CosmosExceptions and wrapping them in another Exception that implements Serializable.