undo— agent skill

You are the /undo skill. Reverse the assistant's most recent change without destroying work.

Triggers

• Slash form: /undo
• Natural language: "undo that", "take that back", "revert what you just did"

Hard refusals (check first)

Run these checks. If any return non-empty/non-zero, refuse with the corresponding message:

1. Pushed commits. git log @{upstream}..HEAD --oneline 2>/dev/null — if empty, fine; if non-empty AND the user is asking to undo a committed change, only operate on unpushed commits. If the only commits in scope are pushed, refuse:

"I can't undo commits you've already pushed. That would rewrite shared history. Want help doing it manually?"

1. Merge in progress. git rev-parse --verify MERGE_HEAD 2>/dev/null — if exits 0, refuse:

"Something's mid-merge here — that's beyond what I'll touch automatically. Want me to walk you through it?"

1. No git repo. git rev-parse --is-inside-work-tree 2>/dev/null — if not, this skill shouldn't exist; tell user the safety net wasn't activated.

Step 1: Detect mode

Run git status --porcelain and capture output.

• Output non-empty (dirty tree) → Mode 1: undo uncommitted changes.
• Output empty + recent commits in session → Mode 2: undo a session commit.
• Output empty + no session commits → "There's nothing to undo right now."

To detect session commits, read .claude/.session-start for the session-start timestamp and run:

git log --since="@$(cat .claude/.session-start)" --pretty=format:'%h %s'

Mode 1: Uncommitted changes

Step 1.1: Show what will be undone

git status --porcelain

Translate to plain English:

"I'm about to undo these changes: - Modified: src/foo.js - Modified: src/bar.js - New file: src/baz.js

>

Nothing will be deleted permanently — I'll save them as a checkpoint first so you can restore if needed. OK to proceed? (yes / no)"

Step 1.2: Stash on confirm

git stash push -u -m "undo: $(date -u +%Y-%m-%dT%H:%M:%SZ)"

Step 1.3: Confirm

"Done. If you change your mind, tell me to 'restore the last undo' and I'll bring it back."

Mode 2: Committed in this session

Step 2.1: Pre-flight stash of any uncommitted changes

Run git status --porcelain. If non-empty:

git stash push -u -m "undo-preflight: $(date -u +%Y-%m-%dT%H:%M:%SZ)"

Tell the user:

"You have unsaved changes on top of the commit. I'll set those aside first, then undo the commit. Both are recoverable."

Step 2.2: List session commits

Show them with numbers:

"I made these commits in this session: 1. a1b2c3d Add login form 2. e4f5g6h Fix typo

>

Which would you like to undo? (number — only the most recent is straightforward, older requires care)"

Step 2.3: Refuse old history

If the user picks a commit older than the session-start timestamp:

"That commit is from before we started today. I won't touch older history — let me know if you really want to do that manually."

Step 2.4: Soft reset

For the chosen commit, run:

git reset --soft <commit>^

This keeps changes staged. Confirm:

"Done. Your changes are staged but the commit is gone. You can re-commit differently or use git restore --staged . to unstage."

Step 2.5: Re-apply pre-flight stash

If a pre-flight stash was created:

git stash pop

Tell the user:

"I've also put back the unsaved changes you had."

Restoration

Triggered by: "restore the last undo", "bring back what we undid".

git stash pop

If multiple undo: stashes exist, list and ask which.

Hard rules

• Never run git reset --hard.
• Never run git clean.
• Never touch pushed commits.
• Every operation must be reversible (stash and soft reset are; hard reset and clean are not).