QuantConnect/Lean · error · RegressionTestException

Expected option assignment but got: {orderEvent}

Error message

Expected option assignment but got: {orderEvent}

What it means

In OnOrderEvent, after the initial option sell fill, the next expected Filled event must be the option assignment: OrderType.OptionExercise with IsAssignment == true. If the event is not an assignment (e.g., the limit order from line 78 filled, or an unexpected fill arrived), the regression fails.

Source

Thrown at Algorithm.CSharp/DuplicateOptionAssignmentRegressionAlgorithm.cs:87

        public override void OnOrderEvent(OrderEvent orderEvent)
        {
            if (orderEvent.Status == OrderStatus.Filled)
            {
                // This is the fill for the option sell order
                if (!_optionSold)
                {
                    // Let's close the position but with a limit order that won't ever fill (limit price too low)
                    // just so we keep it open until the brokerage tries to assign it
                    LimitOrder(_option, 1, Securities[_option].Price * 0.1m);

                    _optionSold = true;
                }
                // This is the assignment
                else if (!_optionAssigned)
                {
                    if (orderEvent.Ticket.OrderType != OrderType.OptionExercise || !orderEvent.IsAssignment)
                    {
                        throw new RegressionTestException($"Expected option assignment but got: {orderEvent}");
                    }

                    _optionAssigned = true;
                }
                else if (!_stockAssigned)
                {
                    if (orderEvent.Ticket.OrderType != OrderType.OptionExercise || orderEvent.IsAssignment || orderEvent.Symbol != _stock)
                    {
                        throw new RegressionTestException($"Expected stock assignment but got: {orderEvent}");
                    }

                    _stockAssigned = true;
                }
                else
                {
                    throw new RegressionTestException($"Unexpected order fill event: {orderEvent}");
                }
            }

View on GitHub (pinned to d2c3659f87)

Solutions

1. Confirm the LimitOrder price (10% of current) is far enough from market that it cannot fill; lower the factor if needed.
2. Log every OrderEvent with its Status, OrderType, IsAssignment, and Symbol to trace the sequence.
3. Verify the option (GOOG Put $800 expiring 2015-12-24) is in-the-money at expiry so assignment occurs.
4. Check for a Lean regression in option-exercise event generation.

else if (!_optionAssigned)
{
    if (orderEvent.Ticket.OrderType != OrderType.OptionExercise || !orderEvent.IsAssignment)
    {
        Debug($"Unexpected event: {orderEvent.Status} {orderEvent.Ticket.OrderType} IsAssign={orderEvent.IsAssignment}");
        throw new RegressionTestException($"Expected option assignment but got: {orderEvent}");
    }
    _optionAssigned = true;
}

When it happens

Trigger: The LimitOrder placed at 10% of price unexpectedly filled (it is designed never to fill), or an order event arrives out of the expected sequence (sell -> option assignment -> stock assignment), or assignment did not fire by expiry.

Common situations: A Lean change where low-priced limit orders fill against the bid, a change in option-exercise/assignment event ordering, or the option not being assigned at expiry due to a data/exercise-logic regression.

Related errors

• Expected stock assignment but got: {orderEvent}
• Unexpected order fill event: {orderEvent}
• Option was not assigned
• Stock was not assigned
• Index is not tradable.

AI-assisted analysis of QuantConnect/Lean@d2c3659f87 (2026-08-13). Data as JSON: /api/errors/907d2fcb41907a19. Report an issue: GitHub.