Worked on the redis/redis repository to enhance the reliability of cluster rebalance operations in the Redis CLI by addressing a CROSSSLOT error that occurred when using the --user flag without -a. The solution involved root-cause analysis and a targeted fix in C, consolidating MIGRATE argument handling to prevent empty argv slots from being serialized as keys. This adjustment stabilized key-slot calculations and improved the predictability of node reconfigurations. Collaborated closely with other contributors, co-authoring the patch and documenting the process. Utilized C programming, Tcl scripting, and unit testing to deliver a robust, maintainable improvement to cluster rebalance workflows.