What causes "modify_order requires a price (none on order or command)" in nautechsystems/nautilus_trader?

Include price in the ModifyOrder command (cmd.price = Some(current or new price)).

modify_order requires a price (none on order or command)

Error message

modify_order requires a price (none on order or command)

What it means

For non-market-style orders (limits, stop-limits, etc.) Lighter requires an explicit limit price in ticks on a modify. The adapter looks for the price on the ModifyOrder command first, then falls back to the order's own price; if both are absent it cannot build the modify.

Source

Thrown at crates/adapters/lighter/src/execution.rs:1972

        // acceptable `price` cap, derived from the trigger and slippage like submit.
        let price_ticks = match order.order_type() {
            OrderType::StopMarket | OrderType::MarketIfTouched => {
                let trigger = new_trigger.ok_or_else(|| {
                    anyhow::anyhow!("{:?} orders require a trigger_price", order.order_type())
                })?;
                let is_buy = matches!(order.order_side(), OrderSide::Buy);
                let slippage_bps = self.resolve_slippage_bps(cmd.params.as_ref());

                derive_market_order_price_ticks(
                    trigger.as_decimal(),
                    is_buy,
                    price_precision,
                    slippage_bps,
                )?
            }
            _ => {
                let new_price = cmd.price.or(order.price()).ok_or_else(|| {
                    anyhow::anyhow!("modify_order requires a price (none on order or command)")
                })?;

                price_to_ticks(&new_price, price_precision)?
            }
        };

        let base_amount = quantity_to_ticks(&new_qty, instrument.size_precision())?;
        anyhow::ensure!(
            base_amount > 0,
            "quantity `{new_qty}` rounds to 0 ticks at size_precision {}",
            instrument.size_precision(),
        );
        let trigger_price_ticks = match new_trigger {
            Some(trigger) if trigger.raw != 0 => price_to_ticks(&trigger, price_precision)?,
            _ => 0,
        };

        if matches!(

View on GitHub (pinned to 18893faf8b)

Solutions

Include price in the ModifyOrder command (cmd.price = Some(current or new price)).
Ensure the original order was created with a limit price so order.price() is populated.
If the order is truly market-style, expect the trigger_price branch instead and supply trigger_price.

Example fix

// before
let cmd = ModifyOrder::new(instrument_id, client_order_id).quantity(Some(new_qty));
// after
let cmd = ModifyOrder::new(instrument_id, client_order_id)
    .quantity(Some(new_qty))
    .price(Some(order.price().unwrap()));

Defensive patterns

Strategy: validation

Validate before calling

if cmd.price.is_none() && order.price().is_none() {
    return Err("modify needs a price: set cmd.price or use an order with a limit price".into());
}

Try / catch

if let Err(e) = client.modify_order(&cmd).await {
    if e.to_string().contains("requires a price") {
        let cmd = cmd.with_price(order.price().expect("order has no price"));
        client.modify_order(&cmd).await?;
    }
}

Prevention

Populate price on every limit-order modify command explicitly.
Reject order creation without a price for limit types at strategy level.
Keep price fields as Decimal end-to-end to avoid dropping them in conversions.

When it happens

Trigger: prepare_signed_modify_order reaches the non-market branch (order_type not StopMarket/MarketIfTouched) with cmd.price = None and order.price() = None — typically a market-typed order being routed through the modify path, or a limit order created without a price.

Common situations: Modifying only the quantity of a limit order but the order object was built without a persisted price; passing a ModifyOrder with quantity-only updates to a venue that always resends the full price; mixing up market and limit order types.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/b05bdbef60390af6. Report an issue: GitHub.