diff --git a/.claude/skills/post-merge-cleanup/skill.md b/.claude/skills/post-merge-cleanup/skill.md
new file mode 100644
index 0000000000..9a2283d21e
--- /dev/null
+++ b/.claude/skills/post-merge-cleanup/skill.md
@@ -0,0 +1,25 @@
+# Post-Merge Cleanup
+
+Run this after squash-merging a PR to clean up the local repo.
+
+## Steps
+
+1. Switch to main and pull latest:
+   ```bash
+   git checkout main && git pull
+   ```
+
+2. Prune remote tracking branches that no longer exist on the remote:
+   ```bash
+   git fetch --prune
+   ```
+
+3. Delete local branches whose remote tracking branch is gone:
+   ```bash
+   git branch -vv | grep '\[.*: gone\]' | awk '{print $1}' | xargs -r git branch -D
+   ```
+   If no gone branches exist, skip this step.
+
+4. Check for any remaining non-main local branches and report them. Do NOT delete branches that still have a remote — only report them.
+
+5. Confirm the workspace is clean with `git status`.