There's been a lot of discussion recently around how Claude Code updates affect behavior, predictability, and token usage.

When Claude Code updates, it's not just the model that changes - the CLI harness, system prompts, tool-calling behavior, and context management all evolve too. Newer is often better. But not always for every workflow.

In my own setup, I noticed that some skills, agents, and project workflows I'd built behaved differently after recent updates. Not necessarily worse, but differently enough that predictability started to matter.

For AI-assisted development, that matters.

The problem

Sometimes you want the latest model. Sometimes you want the setup your workflow was built around.

There's no built-in way to run an older Claude Code version side-by-side with the latest one.…