What causes "Assignment was not expected for {order_event.symbol}" in QuantConnect/Lean?

Confirm the put is genuinely OTM relative to the underlying at expiry in the current data.

QuantConnect/Lean · error · AssertionError

Assignment was not expected for {order_event.symbol}

Error message

Assignment was not expected for {order_event.symbol}

What it means

In assert_future_option_contract_order, an OTM short put expiring worthless must NOT be assigned. If order_event.is_assignment is true, the regression treats it as an error — the option was assigned when the test's scenario expects it to expire worthless.

Source

Thrown at Algorithm.Python/FutureOptionShortPutOTMExpiryRegressionAlgorithm.py:100

            raise AssertionError(f"Expected no order events for underlying Symbol {security.symbol}")

        if security.symbol == self.expected_contract:
            self.assert_future_option_contract_order(order_event, security)

        else:
            raise AssertionError(f"Received order event for unknown Symbol: {order_event.symbol}")

        self.log(f"{order_event}")

    def assert_future_option_contract_order(self, order_event: OrderEvent, option_contract: Security):
        if order_event.direction == OrderDirection.SELL and option_contract.holdings.quantity != -1:
            raise AssertionError(f"No holdings were created for option contract {option_contract.symbol}")

        if order_event.direction == OrderDirection.BUY and option_contract.holdings.quantity != 0:
            raise AssertionError("Expected no options holdings after closing position")

        if order_event.is_assignment:
            raise AssertionError(f"Assignment was not expected for {order_event.symbol}")

    def on_end_of_algorithm(self):
        if self.portfolio.invested:
            raise AssertionError(f"Expected no holdings at end of algorithm, but are invested in: {', '.join([str(i.id) for i in self.portfolio.keys()])}")

View on GitHub (pinned to d2c3659f87)

Solutions

Confirm the put is genuinely OTM relative to the underlying at expiry in the current data.
If you modified the option assignment/exercise or pricing model, verify OTM options are not assigned.
Check the strike vs underlying settlement price for the test contract.

Defensive patterns

Strategy: validation

Validate before calling

# Compute moneyness at expiry to decide whether assignment is valid
underlying_price = self.securities[self.es19m20].price
is_itm = underlying_price < self.put_strike  # short put ITM if underlying < strike
if order_event.is_assignment and not is_itm:
    raise AssertionError(f'OTM put assigned: underlying={underlying_price}, strike={self.put_strike}')

Prevention

Encode the ITM condition explicitly so the test fails with a clear moneyness message instead of a bare assignment error.
When modifying the exercise/assignment pipeline, re-run OTM-expiry regressions to catch over-assignment.

When it happens

Trigger: An OrderEvent with is_assignment == True reaches the assertion. Assignment of an OTM put at expiry indicates the option was treated as ITM, or the assignment pipeline fired incorrectly.

Common situations: Data/pricing change made the put ITM near expiry; the auto-exercise threshold logic changed; or expiration/assignment pipeline was modified to over-assign.

Related errors

AI-assisted analysis of QuantConnect/Lean@d2c3659f87 (2026-08-13). Data as JSON: /api/errors/28ad32102770795c. Report an issue: GitHub.