history:undo

Undo a previously executed history batch via WebSocket.
Equivalent to POST /api/history/undo in REST.

Each undo creates a new batch containing the inverse operations of the original one.
The original batch becomes marked as undone, and a new batch is linked via UndoOf / UndoneBy.

Rate limits

• Maximum 3 undo requests per 10 seconds per user.

---

Client → Server history:undo

{
  "batchId": "b8e0c4cb-8ab7-4b2e-91cd-8fd92e1b9a20"
}

Parameters:

• batchId (UUID, required) — identifier of the batch to undo.
  Must be visible to the current user and not already undone.

---

Success (ack)

{
  "ok": true,
  "batchId": "f1b4232e-7c9f-4c12-9f0a-17cc0012a511",
  "undoOf": "b8e0c4cb-8ab7-4b2e-91cd-8fd92e1b9a20",
  "diff": {
    "nodes": [
      { "id": "uuid", "title": "Old title", "version": 5 }
    ],
    "links": []
  },
  "trace_id": "af2b3d44c7b2"
}

Field reference

Field	Description
batchId	ID of the newly created undo batch
undoOf	ID of the original batch being undone
diff	Actual inverse diff applied to client state
trace_id	Internal diagnostic identifier for tracing requests

---

Error (ack)

{
  "ok": false,
  "error": "conflict.already_undone",
  "message": "Batch has already been undone",
  "trace_id": "af2b3d44c7b2"
}

Errors: see error codes

---

Example (JavaScript)

socket.emit("history:undo", { batchId: "b8e0c4cb-8ab7-4b2e-91cd-8fd92e1b9a20" }, (ack) => {
  if (!ack.ok) return console.error("Undo failed:", ack);
  console.log("Undo successful, new batch:", ack.batchId);
});

---

Example (Python)

import socketio

sio = socketio.Client()

@sio.event
def connect():
    print("connected")
    sio.emit("batch:undo", {"batchId": "<uuid>"}, callback=lambda ack: print("ACK:", ack))

sio.connect("https://synaptask.space",
            headers={"Authorization": "Bearer <API_TOKEN>"},
            transports=["websocket"])
sio.wait()

See also history:redo