Alpha Market SIP defected Tick Print
I have an algo that trades on breakouts. Today a SPY trade got stopped out at ~$769.94 while the underlying was at ~$771. My coding agent blamed on Alpha's bad tick print. Is it normal for Alpha Market SIP to send bad data once in a while?
This is the agent's answer, when I ask if there was a bug in the code:
Not a logic bug like “wrong stop” or “compared the wrong price.”
The code did what it was written to do: one trade tick ≤ SL → exit. Tick said $769.94, SL was $769.98, so it fired.
What was on us: weak safeguards. We already knew bad SIP prints exist (that’s why the outlier filter is there), but a ~0.2% garbage print still got through the 1% filter, and we exited on a single tick. That’s a design hole, not a miscalculated SL.
So: bad print from the feed + our code being too eager to trust it. Not a broken stop formula.
