Identify the root cause before modifying code
Ask the agent to find the real underlying reason for a problem, and explain it to you, before it starts changing code.
Separate diagnosis from repair: trace the failure back to the specific defect, such as a wrong assumption, bad data, or a missing check, and confirm it explains every symptom before any fix is written.
A doctor figuring out why you have a fever before prescribing anything. Fever medicine makes you feel better, but if it's an infection, the infection is still there.
Agents are eager to change code. Without this instruction they often fix the first plausible thing, which can hide the symptom while the real cause keeps doing damage elsewhere.
Root cause: the coupon handler runs every time the page redraws, so the discount stacks. Rounding the total would only hide it. Want me to fix the handler?
Identify the root cause of the wrong checkout total and explain it to me, with evidence, before modifying any code.
Accepting the first explanation that sounds right. A real root cause explains every symptom, not just the one you noticed.