> Claude code does some of this by handing off the "explore" agent work to haiku

This is no longer necessarily true. As of 2.1.198 [0] (released July 1st): "The built-in Explore agent now inherits the main session’s model (capped at opus) instead of running on haiku"

[0] https://code.claude.com/docs/en/changelog#2-1-198