The 14-Month Half-Life of Your Prompt Expert
Every company shipping AI features in production has one or two engineers it cannot afford to lose, and most of them do not know who those engineers are until the resignation email arrives.
The person in question is rarely the loudest in the room. They are the one who remembers that the customer-support summarizer's tone got fixed by a three-line system-prompt edit after the Q2 escalation, that the eval suite added six cases the week the model provider quietly changed its default sampling, and that the judge calibration drifted the last time someone "cleaned up" the rubric. None of this is written down in a place a successor would find. It lives in one head, and that head is being messaged by a recruiter with a 25% raise attached roughly every two weeks.
