I've not tried actually migrating from Claude Code... but having played a bit with other clients, I would avoid Mistral Vibe. I want to love it, there's some things that are nice about Vibe (mostly just "oui oui baguette"), but the things I did not like about it were disastrously bad. I could barely get MCP servers configured, and it was in something of a broken state even when I did get it working. I have many words about how horrified I am at how far behind Mistral is, but I will spare the rant.

OpenCode is another one to consider looking at: https://opencode.ai/ Not sure I'd recommend it, but it's worthy of consideration, as is Pi.

Also, consider that you can build your own. I've got Claude Code in the background working on improvements to my own harness (just for myself) at the moment. Though my intention is to have a mini API-only Claude Code that I can use on retro machines that don't support it, I don't need a full Claude Code feature set.