valkey-cli is the official cluster management tool. If we consider atomic slot migration to be fully supported, the cli should use atomic slot migration instead of the old SETSLOT method, in these commands:

valkey-cli --cluster reshard
valkey-cli --cluster rebalance

Alternatives you've considered

If we think that atomic slot migration is experimental, then we can wait and do this change in 9.1 or 10.0 instead.

Additional information

Even if not everyone uses valkey-cli as a cluster admin tool, it is used as a reference implementation when implementing another control planes such as kubernetes operators.

Follow-up of #23, #1949