Why Pre-Market Backtest Data May Not Be Available in Live Simulation

Summary

This short platform discussion distinguishes a backtest’s pre-market processing from live or simulated trading. In a backtest, the pre-market step may access the current day’s opening price, allowing a rule to use that price to decide on afternoon trading without necessarily introducing look-ahead bias, provided the decision occurs after the open is known.

The reply says simulated trading cannot access the next day’s data. Therefore, a signal generated after the previous afternoon’s close cannot use the next morning’s opening price to determine that day’s afternoon trade through the same mechanism. The exchange offers no implementation details or broader evidence, so the answer is limited to the platform behavior described in this discussion.

Key ideas

• Backtest pre-market processing may access the current day’s opening price.
• A strategy can use the open for a later decision if that price is already available at decision time.
• The discussion says simulation cannot access data from the following day when the prior-day signal is generated.
• The reply is a brief platform-specific explanation and does not document its technical implementation.

Tags

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.