Why your EA's safety net might secretly be your main stop-loss

Every EA I run has a hard EUR-based loss cap as a last-resort safety net - a broker-side backstop against slippage, not the real stop. Yesterday I found mine had quietly become the ONLY stop firing on every single trade.

The cap (0.65 EUR) was tuned weeks earlier for gold's fast slippage on a different symbol. When the bot switched back to EURUSD, nobody re-checked whether that number still made sense at EURUSD's pip scale. It didn't: at the live lot size, 0.65 EUR worked out to about 1.8 pips - tighter than the strategy's own minimum stop distance. Every trade was getting cut on ordinary noise before the real signal even had a chance to be right or wrong.

The fix took one line. Finding it took building a proper live-code replay harness that fed real historical bars through the actual, unmodified signal function - because the bug was invisible in the logs; it looked exactly like "the strategy just isn't working."

Lesson for anyone running a multi-symbol EA: any EUR or fixed-unit threshold needs to be re-validated against the current symbol's pip value every time you switch instruments. A "safety net" sized for one symbol can silently become the primary - and wrong - stop on another.