[foxnne]

Part of fizzyedit/plans#14 (plans/SHARED_HISTORY_PLAN.md step 3; plans/RECORDING_PLAN.md step 10 for pixi).

Most of pixi's share of shared history was already on main (#48, #49, #56, #57, #59, #60, #62: step ids, every step reported with its top and author, historyLine/historyGoTo, going back as a step, the waiting draw keeping its author). This closes what was left.

What changes

• A sprite's undo comes back when it opens again. restoreHistory: each entry one pixel step (steps.zig), kept with its id, checked against the sprite first (steps.fits, a walk back and forward on a copy of each layer the steps touch) and refused, history untouched, when it does not fit; ids must be distinct, non-zero and not the unsaved mark. A non-empty history is refused over one being made (fizzy picks a kept track up again when a restart leaves a track with no base, which could otherwise replace live history). A saved sprite stays saved. An empty history clears it, so "Forget This Document's History" works for pixi too.
• documentFingerprint: a hash of the grid, each layer by position (name, shown, folded, pixels; a drawing still being revealed as it ends), the sprites' origins and each animation's name and frames. fizzy keeps a closed document's track only when the owner has one, so until now no pixi track was ever kept and nothing could be restored.
• A step pixi cannot encode yet is still attributed. While tracks record (fizzy's default), every non-pixel change (add layer, rename, …) reported only restarted, so fizzy never heard of the step: an agent's Add Layer read as nobody's, and "Go back to before Claude's change" could not find it. A step added now follows its restart, effect empty; the recorder's new track drops steps before its base, so tracks are unchanged. Undo and redo of such a step still report only the restart: with the authors cleared, fizzy would read the step as the person's and announce the wrong undoer.
• Pixi's "Undo: … / Redo: …" toast is gone (maintainer's ask): fizzy's activity feed and its "Undid Claude's Draw" bubble say it, and whose. Its quiet flag, which only silenced that toast, goes with it.

Known limit, needs fizzy: a restarted clears fizzy's author map, so after a non-pixel step the steps before it read as the person's (seen: Claude's Draw before Claude's Add Layer, after going back). Fix: either pixi encodes every Change kind (RECORDING_PLAN step 4), or fizzy's Tracks starts a new track on an empty-effect step so owners need not send restarted for it. Left as a follow-up. Also not carried yet: a take-back step's "Back to …" title across a reopen (text's #641 put it in its step format; pixi's format has no label).

How it was seen (macOS, debug fizzy at main 58cdcb16, --quiet, its own profile, pixi Debug):

• An MCP client named Claude drew and added a layer: fizzy.undo answered {"title":"Layer","by":"Claude"}, then {"title":"Draw","by":"Claude"}; the control server's own calls read as the person's.
• ⌘Z (played by a tape) showed "Undid Claude's Draw" with Redo and the strip at "Back to Draw 6/7"; no pixi toast.
• fizzy.goBackBefore answered {"to":3,"by":"Claude","also_taken_back":0} and the agent's layer was gone.
• Two draws, saved, closed, opened again: undo, undo, redo, redo walked steps 2 and 1 and back (they read as the person's after the reopen: fizzy forgets authors at close). After review: three draws with the third undone, closed and reopened: redo brought step 3 back, then undo walked 3, 2, 1.
• zig build test: the new fits test (a history fits the sprite it leads to, not another).

Not seen: Windows/Linux (no platform code here).

🤖 Generated with Claude Code