What causes "`close_position` cannot be combined with `reduce_only` on Binance" in nautechsystems/nautilus_trader?

Set reduce_only=false when using close_position — the flag is redundant for a whole-position close

nautechsystems/nautilus_trader · error · anyhow::Error

`close_position` cannot be combined with `reduce_only` on…

Error message

`close_position` cannot be combined with `reduce_only` on Binance

What it means

Binance Futures treats closePosition and reduceOnly as mutually exclusive: closePosition already implies closing the whole position, so combining them is rejected by the venue. The adapter validates this before submission and fails fast with this message.

Solutions

Set reduce_only=false when using close_position — the flag is redundant for a whole-position close
Or keep reduce_only and drop close_position, sizing the order to the position manually

Example fix

// before — both flags set
// order: reduce_only = true; params: close_position = true

// after — close_position implies the reduce
// order: reduce_only = false; params: close_position = true

Defensive patterns

Strategy: validation

Validate before calling

// Before submit_order()
let close_position = params.get_bool("close_position").unwrap_or(false);
if close_position {
    assert!(!order.is_reduce_only(), "close_position cannot combine with reduce_only");
}

Type guard

fn close_position_flags_valid(close_position: bool, reduce_only: bool) -> bool {
    !(close_position && reduce_only)
}

Try / catch

On this local rejection, rebuild the order with reduce_only=false (close_position already implies the reduce) and resubmit.

Prevention

Do not apply blanket reduce-only flags to exit orders in risk wrappers
Test flag combinations for exit orders before deployment
Keep exit-order parameter sets in one reviewed location

When it happens

Trigger: SubmitOrder where params has close_position=true and the order was built with reduce_only=true.

Common situations: Risk-management wrappers that mark every exit order reduce-only; ported strategies stacking protective flags on close orders.

Related errors

AI-assisted analysis of nautechsystems/nautilus_trader@d1527c24af (2026-08-16). Data as JSON: /api/errors/424c46c76658129e. Report an issue: GitHub.

Appendix: source

Thrown at crates/adapters/binance/src/futures/execution.rs:2633

            .params
            .as_ref()
            .and_then(|p| p.get_bool(PARAMS_CLOSE_POSITION))
            .unwrap_or(false);

        if close_position {
            let order_type = order.order_type();

            if !matches!(
                order_type,
                OrderType::StopMarket | OrderType::MarketIfTouched
            ) {
                anyhow::bail!(
                    "`close_position` is not supported for order type {order_type:?} on Binance"
                );
            }

            if order.is_reduce_only() {
                anyhow::bail!("`close_position` cannot be combined with `reduce_only` on Binance");
            }
        }

        if let Some(pm_str) = cmd.params.as_ref().and_then(|p| p.get_str("price_match")) {
            BinancePriceMatch::from_param(pm_str)?;
            let order_type = order.order_type();
            anyhow::ensure!(
                !order.is_post_only(),
                "price_match cannot be combined with post-only orders"
            );
            anyhow::ensure!(
                order_type == OrderType::Limit,
                "price_match is not supported for order type {order_type:?}"
            );
        }

        let lifetime = determine_futures_order_lifetime(
            self.product_type,

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