nautechsystems/nautilus_trader · error

Failed to build market order: {e}

Error message

Failed to build market order: {e}

What it means

Raised in `submit_market_order` after the order book fetch, when the order builder fails to construct and sign the FOK/FAK market order from price, signed_amount, neg_risk, and tick parameters. The underlying builder error (e.g. rounding to tick size failure, amount-to-lots conversion, signing error) is embedded in the message. Submission is aborted before any request is sent to the venue.

Source

Thrown at crates/adapters/polymarket/src/execution/submitter.rs:211

                price,
                ctx.fee_rate,
                ctx.fee_exponent,
                ctx.builder_taker_fee_rate,
            )?,
            _ => amount_dec,
        };

        let poly_order = self
            .order_builder
            .build_market_order(
                &token_id,
                poly_side,
                price,
                signed_amount,
                neg_risk,
                tick_decimals,
            )
            .map_err(|e| anyhow::anyhow!("Failed to build market order: {e}"))?;

        // Wire amounts are mantissas at USDC_DECIMALS (10^6) scale. The share-denominated leg is
        // the exact base quantity signed for the venue: takerAmount for BUY and makerAmount for
        // SELL. Market SELL signing truncates shares to two decimal places.
        let signed_base_qty =
            signed_base_quantity(poly_order.maker_amount, poly_order.taker_amount, poly_side);
        let expected_venue_order_id = self
            .order_builder
            .expected_order_id(&poly_order, neg_risk)?;

        let http_client = self.http_client.clone();
        let saw_unknown_outcome = Arc::new(AtomicBool::new(false));

        let response = match self
            .retry_manager
            .invocation(
                "submit_market_order",
                || {

View on GitHub (pinned to 18893faf8b)

Solutions

1. Read the inner builder error in the message for the exact cause
2. Align the order price/amount to the instrument's current tick_size and size precision before submitting
3. Refresh instrument metadata (tick size, neg_risk) rather than caching stale values
4. Verify the signing key/wallet is configured correctly

ensure!(price.as_decimal() % tick_size.as_decimal() == Decimal::ZERO, "price not on tick");
ensure!(neg_risk == market_neg_risk, "neg_risk mismatch");

if let Err(e) = submitter.submit_market_order(req).await {
    if e.to_string().contains("Failed to build market order") {
        // refresh tick size / neg_risk metadata and re-align price before retrying
    }
}

When it happens

Trigger: Price not aligned to the market tick_size; signed_amount below minimum size; negative-risk market flags inconsistent; malformed book data leading to no valid executable level; EIP-712 signing failure (bad signing key).

Common situations: Using a price rounded to more decimals than tick_decimals; trading neg-risk markets without the correct neg_risk flag; tick size changed by the venue (0.01 -> 0.001) so cached tick parameters are stale.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• Polymarket {signature_type:?} signature type requires a fund
• Polymarket collateral-sized limit BUY price must be positive
• Failed to derive order hash: {e}
• EIP-712 signing failed: {e}
• historical {field} {value} is not exactly representable as a

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/319e2e33408b5555. Report an issue: GitHub.