Cancel Order

A user can cancel an order created by himself and with status pending sending action cancel, the rumor's content of the message will look like this:

[
  {
    "order": {
      "version": 1,
      "id": "<Order Id>",
      "action": "cancel",
      "payload": null
    }
  },
  "<index N signature of the sha256 hash of the serialized first element of content>"
]

Mostro response

Mostro will send a message with action cancel confirming the order was canceled, here an example of rumor's content of the message:

[
  {
    "order": {
      "version": 1,
      "id": "<Order Id>",
      "action": "canceled",
      "payload": null
    }
  },
  null
]

Mostro updates the addressable event with d tag <Order Id> to change the status to canceled:

[
  "EVENT",
  "RAND",
  {
    "id": "<Event id>",
    "pubkey": "<Mostro's pubkey>",
    "created_at": 1702549437,
    "kind": 38383,
    "tags": [
      ["d", "<Order Id>"],
      ["k", "sell"],
      ["f", "VES"],
      ["s", "canceled"],
      ["amt", "7851"],
      ["fa", "100"],
      ["pm", "face to face"],
      ["premium", "1"],
      ["network", "mainnet"],
      ["layer", "lightning"],
      ["expiration", "1719391096"],
      ["y", "mostro", "[Mostro instance name]"],
      ["z", "order"]
    ],
    "content": "",
    "sig": "<Mostro's signature>"
  }
]

Bond race during take

Multiple takers may simultaneously attempt to take the same order: each creates their own bond hold invoice (a Requested bond row) and whichever HTLC is accepted first by LND wins. When a bond locks, all other concurrent Requested bonds on the same order are released and their takers each receive Action::Canceled.

A client that sent take-buy / take-sell and is waiting for pay-bond-invoice may therefore receive canceled instead — meaning another taker's bond locked first. Surface this clearly to the user, e.g. "Order was taken by another user before you locked the bond." Do not silently retry the take — the order may no longer be available.

Cancel during waiting-taker-bond

An order remains in the daemon-internal waiting-taker-bond state (NIP-33 s tag still pending) while one or more taker bonds are outstanding. Cancels during this window are routed differently from cancels on pending orders.

Taker self-cancel

A taker who has a Requested (unpaid) bond on an order may cancel it by sending cancel. Mostro releases only that taker's bond (LND invoice cancelled, funds returned). Other concurrent takers' bonds are unaffected and continue racing.

• If the cancelling taker was the only prospective taker, the order drops back to pending and is visible on the order book again.
• If other takers' bonds are still Requested, the order remains in waiting-taker-bond with those bonds still racing.

The maker is not notified; the NIP-33 order event stays pending throughout.

Maker cancel

The maker can cancel the order at any point before trade flow starts (i.e. while in pending or waiting-taker-bond). Sending cancel releases all concurrent taker bonds on the order, notifies each prospective taker with canceled, transitions the order to canceled, and publishes the updated NIP-33 event.

Cancel cooperatively

A user can cancel an active order, but will need the counterparty to agree, let's look at an example where the seller initiates a cooperative cancellation:

[
  {
    "order": {
      "version": 1,
      "id": "<Order Id>",
      "action": "cancel",
      "payload": null
    }
  },
  null
]

Mostro will send this message to the seller:

[
  {
    "order": {
      "version": 1,
      "id": "<Order Id>",
      "action": "cooperative-cancel-initiated-by-you",
      "payload": null
    }
  },
  null
]

And this message to the buyer:

[
  {
    "order": {
      "version": 1,
      "id": "<Order Id>",
      "action": "cooperative-cancel-initiated-by-peer",
      "payload": null
    }
  },
  null
]

The buyer can accept the cooperative cancellation sending this message:

[
  {
    "order": {
      "version": 1,
      "id": "<Order Id>",
      "action": "cancel",
      "payload": null
    }
  },
  null
]

And Mostro will send this message to both parties:

[
  {
    "order": {
      "version": 1,
      "id": "<Order Id>",
      "action": "cooperative-cancel-accepted",
      "payload": null
    }
  },
  null
]

Mostro updates the addressable event with d tag <Order Id> to change the status to canceled:

[
  "EVENT",
  "RAND",
  {
    "id": "<Event id>",
    "pubkey": "<Mostro's pubkey>",
    "created_at": 1702549437,
    "kind": 38383,
    "tags": [
      ["d", "<Order Id>"],
      ["k", "sell"],
      ["f", "VES"],
      ["s", "canceled"],
      ["amt", "7851"],
      ["fa", "100"],
      ["pm", "face to face"],
      ["premium", "1"],
      ["network", "mainnet"],
      ["layer", "lightning"],
      ["expiration", "1719391096"],
      ["y", "mostro", "[Mostro instance name]"],
      ["z", "order"]
    ],
    "content": "",
    "sig": "<Mostro's signature>"
  }
]