The pql post-checkout hook unconditionally sourced .pql/hooks/post-checkout from the worktree toplevel, which doesn't exist in a fresh `git worktree add` — aborting the checkout. Guard on the file existing so worktree creation (used by parallel agent workflows) no longer fails. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>