Halfway through a task you check out a different git branch. What changes for the session that is already running?

The principle — the files move with the branch; the conversation stays with the directory.

Why the key is correct — Anthropic states it directly: Claude sees your current branch's files, and when you switch branches Claude sees the new branch's files, but your conversation history stays the same. The two halves are independent, which is what makes it safe to change branch mid-task without re-explaining anything.

Why the others are wrong — a checkout does not create a session, because sessions are bound to the directory and the directory has not changed. Nor is there a cached copy of the old branch's files; reads happen against what is on disk at the time. And the conversation is untouched, so re-briefing is work you do not owe.

Remember this — you can change branch and keep talking; Claude will read whatever is there now.

Sources — Anthropic's How Claude Code works.