> ## Documentation Index
> Fetch the complete documentation index at: https://docs.darknyx.trade/llms.txt
> Use this file to discover all available pages before exploring further.

> Which combinations of order type, time in force, execution attribute, and price field are valid.

# Order compatibility

# Order Compatibility

<Info>
  **TL;DR**

  Not every combination of type, time-in-force, and execution attribute makes
  sense. This page is the validity matrix; read it before assembling an order
  programmatically.
</Info>

## Type × Time in Force

| Type    | GTC / GTT (rests)               | IOC             | FOK             |
| ------- | ------------------------------- | --------------- | --------------- |
| `limit` | Yes, the standard resting order | n/a (use `ioc`) | n/a (use `fok`) |
| `ioc`   | No; IOC never rests             | Yes             | n/a             |
| `fok`   | No; FOK never rests             | n/a             | Yes             |

Time-in-force on Darknyx is carried by the order type plus `expiry_slot`: a resting
order is a `limit` with an expiry; an immediate order is `ioc` or `fok`. See
[Time in Force](./time-in-force.mdx).

## Type × Execution Attributes

| Type    | `min_fill_size` | All-or-none (`min_fill_size = amount`)                    |
| ------- | --------------- | --------------------------------------------------------- |
| `limit` | Yes             | Yes, rests until a batch can fill it whole                |
| `ioc`   | Yes             | Yes, takes whole-or-nothing immediately, residual cancels |
| `fok`   | Redundant       | Implicit; FOK is already whole-or-nothing                 |

## Type × Price field

| Type        | `price_limit`                                                                      |
| ----------- | ---------------------------------------------------------------------------------- |
| `limit`     | Required, the worst acceptable price.                                              |
| `ioc` (bid) | Required, the price cap (a "market bid" is an IOC with a cap).                     |
| `ioc` (ask) | Optional; `0` accepts any clearing price (a "market ask").                         |
| `fok`       | Required. A bid needs a positive cap; an ask may use `0` as an unrestricted floor. |

A bid always needs a positive `price_limit` (a buy at price zero is meaningless,
and the collateral must cover the worst case). An ask may set `price_limit = 0` to
sell into any clearing price.

## Modifiability

| Action                                           | Supported                                               |
| ------------------------------------------------ | ------------------------------------------------------- |
| Cancel a resting order                           | Yes, [Cancel Order](/api-reference/orders/cancel-order) |
| Modify a resting order (atomic cancel + replace) | Yes, [Modify Order](/api-reference/orders/modify-order) |

IOC and FOK orders do not rest, so there is nothing to cancel or modify
after they execute.

## Quick validity examples

| Intent                                | Type    | Price                              | `min_fill_size` | Expiry                  |
| ------------------------------------- | ------- | ---------------------------------- | --------------- | ----------------------- |
| Resting bid at a price (GTC)          | `limit` | required                           | `0`             | maximum allowed horizon |
| Resting bid, good for 10 min (GTT)    | `limit` | required                           | `0`             | deadline slot           |
| Resting bid, fill-whole-or-wait (AON) | `limit` | required                           | `= amount`      | maximum allowed horizon |
| Cross now up to a cap (market bid)    | `ioc`   | cap                                | `0`             | n/a                     |
| Sell now at any price (market ask)    | `ioc`   | `0`                                | `0`             | n/a                     |
| Immediate, whole, or nothing          | `fok`   | bid cap or ask floor (`0` allowed) | n/a             | n/a                     |