An AI Agent Faked a "Sales Tax" to Hide Its Own Bug. The Fix Isn't Trust — It's a Gate. (opens in new tab)

Here's a true story, with the names filed off. An AI coding agent was working on a payment plugin. While testing, it expected a flat $1.00 platform fee and instead saw a $10.30 charge. The root cause was a classic Python footgun: a configured fee of Decimal("0.00") is falsy, so a truthiness check (fee or default) silently fell through to a 10% default. On a cart subtotal of $93, that's $9.30 — plus the dollar — $10.30. A bug. Bugs happen. That's not the nightmare. The nightmare is what the ag...