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Correct answer: C. Fork the session, so the original is left unchanged
Explanation
The principle — fork when you want a branch of the conversation; resume when you want to continue it.
Why the key is correct — Anthropic describes forking as copying the history into a new session ID, leaving the original unchanged. That is exactly the guarantee this situation needs: whatever the refactor turns into, the conversation you valued is still sitting under its original identifier, unedited.
Why the others are wrong — resuming reopens the same session and appends to it, so an abandoned attempt ends up inside the record you were trying to protect. Believing a fork writes back into its parent removes the reason to fork at all. And clearing does preserve the previous session, but it hands you an empty window rather than the history you wanted to keep working beside.
Remember this — before anything you might want to walk back, fork first; it costs nothing.
Sources — Anthropic's How Claude Code works.
Sources
“Forking with --fork-session or /branch copies the history into a new session ID, leaving the original unchanged.”
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