snapback — undo for your machine

snapback run -- <any command>    # cheap snapshot first, then run it
snapback undo                    # didn't like it? put everything back

We hand filesystem access to AI agents, migration scripts, and codemods every day — and the rollback story below "restore the whole VM" is usually nothing. git checkout doesn't cover your SQLite file, your untracked uploads dir, or the Postgres volume your migration just mangled.

snapback is that missing layer: one command to checkpoint the working tree, your databases, and your container volumes — and one command to snap back.

Quickstart

pip install snapback-cli

snapback run -- python migrate.py     # snapshot, then run
snapback undo                         # roll back the tree (and undo is undoable: `snapback redo`)

snapback snap -m "before letting the agent loose"   # manual checkpoint
snapback list                         # what can I go back to?
snapback diff                         # what changed since the last snapshot?
snapback gc --keep 5                  # prune old snapshots

No config needed — by default snapback snapshots the working tree (minus .snapback/ itself). Zero dependencies, Python ≥ 3.11.

Beyond files: databases and volumes

Drop a snapback.toml in the project root to declare extra targets:

[snapshot]
ignore = ["node_modules", "*.log", "app.db"]   # skip in tree snapshots

[[target]]
backend = "sqlite"          # consistent even while the app holds the db open
path = "app.db"             # (uses SQLite's online backup API, not file copy)

[[target]]
backend = "docker-volume"   # tar the named volume via a helper container
volume = "pgdata"

Every snapback run / snap / undo now covers all three: tree + db + volume, atomically bookended around your risky command.

How it works

• Snapshots live in .snapback/snapshots/<id>/ with a meta.json recording the command, targets, and per-backend payloads.
• undo restores the newest snapshot — but first it saves the current state as a pre-undo snapshot, so redo gets you back. Undo is never a trap.
• run passes the wrapped command's exit code through untouched, so it slots into scripts and CI: snapback run -- make deploy-staging.
• diff [id] shows what changed since a snapshot (A/D/M per path) — check what the agent actually did before deciding whether to undo it.
• Backends are one file each in snapback/backends/, discovered automatically. snapback backends lists what your install supports.

Storage backends

A backend is one file. It exposes NAME, snapshot(spec, payload_dir, root) -> payload, and restore(spec, payload_dir, root, payload) — see snapback/backends/sqlite_db.py for the shape (60 lines). One backend or one integration per PR; see CONTRIBUTING.md.

What snapback is not

• Not a backup tool — snapshots are local, short-lived checkpoints, not disaster recovery. gc them freely.
• Not filesystem magic by default — the portable backend copies files. Switch the tree target to apfs (or a future btrfs/zfs) for O(1) CoW snapshots.
• Not a sandbox — the command really runs. snapback makes it reversible, not contained.

License

MIT