Timeline
Every edit to a notebook is captured to a durable, content-addressed history. Open it from ☰ → 🕘 History: scrub back through every checkpoint, diff, restore, or replay the notebook building itself up from scratch.
What gets recorded
Each checkpoint stores the full serialized notebook once as a content-addressed, compressed object, plus a log entry recording only the cells that changed or were removed. That per-cell delta is also the index behind a cell's own version timeline. Entries are tagged by source:
| Icon | Source |
|---|---|
| 👤 | a browser edit |
| 🤖 | an agent edit |
| 📝 | an external edit (VS Code, git) |
| ↩ | a restore |
| 🌱 | the notebook opening |
| · | a periodic auto-draft |
Captures are deduplicated by content hash, so a no-op capture is free and the store stays clean. A low-frequency background snapshot guarantees an at-least-periodic capture even for changes that slip past the op-level checkpoints.
History is filed under the notebook's document id, not its path, so moving or renaming the file keeps it. The id lives in the .jl, which means copying the file gives both copies one history (and one agent transcript, and one published slot). Slate says so once and offers ☰ → ⑂ Split from copy…, which gives this file a fresh id and copies the stores, so neither side loses anything. See Publishing.
Browsing and diffing
The history panel lists checkpoints newest-first. Select one to see a line diff against its parent. The current state is marked; drafts are dimmed.
Restoring
Restoring is non-destructive: the current state is pushed onto the undo stack and the restore is itself recorded as a new checkpoint, so you can always come straight back.
Replay — the buildup
Press ▶ Replay to step through the checkpoints in order, showing each one's diff in the preview pane, so you can watch the notebook take shape change by change.
Replay only shows. Putting the notebook back into one of those states is the separate ↩ Restore this version button.
Undo / redo
⌘Z / ⌘⇧Z step back through source snapshots for quick reversals. Each entry is labelled with the action it reverses, so the menu reads ↶ Undo cut 3 cells.
Inside a focused cell editor, ⌘Z first undoes your typing. Once that stack is spent it keeps going, stepping back through that cell's own recorded versions from the history store. The cell header shows the age of the version you land on (↶ 2h ago, then · oldest at the beginning), ⌘⇧Z steps forward again, and typing commits the version you are on.
That per-cell history is a different axis from restoring: it walks one cell's distinct past sources, where a restore puts the whole notebook back to a checkpoint.
The stack lives in the hub alongside the open notebook — not in the page — so it survives a reload, a closed tab, and a reconnect days later. You come back to a notebook and pick up where you left off instead of a blank undo stack. It holds the last 100 steps.
The Timeline is the durable, unbounded counterpart: it outlives the hub, and since undo and restore are themselves recorded as new checkpoints, nothing you do can lose earlier state.