Use /cd to move a Claude Code session without blowing away the prompt cache

Claude Code Changelog (v2.1.154+·medium signal

The new /cd command moves a session to a different working directory mid-session without breaking the prompt cache, which a fresh session or a plain shell cd would otherwise invalidate. For long agent sessions that hop between subprojects in a monorepo, this preserves cached context and avoids re-paying for the system/context prefix on every directory switch. A small, non-obvious lever on token cost and latency.