After auditing several prop-firm bots, the same 5 bugs keep failing challenges. Posting them here so you don't lose your evaluation fee.
I run a funded futures account and over the past few weeks I've been looking at other traders' bots — code reviews, strategy audits, the works. Same bugs keep showing up. Posting them so people stop paying $300 evaluation fees over and over.
**Bug #1: Position sizing math is wrong by a factor of 2–4x.**
The most common pattern I see:
contracts = max_risk_usd / stop_loss_points
This ignores the dollar-per-point value of the instrument. NQ is $20/point. ES is $50/point. MES is $5/point. If your formula doesn't multiply by point-value, you're risking 20–50x what you think on every trade.
**Bug #2: Daily drawdown enforcement happens AFTER the broker enforces it.**
Most prop firms auto-flatten you the second you breach daily DD — and then the challenge is dead. Your bot needs to track unrealized + realized P&L in real time and refuse to take any new trade if the next trade's max loss would push you past the limit. The check needs to happen pre-trade, not post-trade.
**Bug #3: No news-event blackout.**
CPI, FOMC, NFP — these print at the same times every month and they will gap your stop-loss by 30+ points on NQ. If your bot is in a position during the release, you don't have a stop-loss; you have a suggestion.
**Bug #4: WebSocket disconnects silently and the bot keeps "trading".**
Broker WebSocket drops happen all the time. If your bot doesn't detect the drop, it'll keep computing signals from stale data and miss exits.
**Bug #5: Logic that treats every setup the same instead of grading confluence.**
Bots that take every signal underperform bots that take only the highest-grade setups. Add a scoring function before entry and threshold it.
Happy to answer questions in the comments.