Prompt changes break production more than model updates. Here's how to test them safely. Your AI customer support bot starts returning wrong refund policies. The document parser starts stripping legal disclaimers. The code reviewer starts approving things it shouldn't. None of the models changed. You changed the prompt. Prompt changes are the #1 source of LLM regressions in production. Model updates are visible — you get a changelog, a version bump, an announcement. Prompt changes are silent. You edit a string, deploy it, and find out three days later when a customer screenshots your bot saying something it shouldn't. The fix is not "be more careful with prompts." The fix is a testing pipeline that treats prompt changes like code changes: run them against a benchmark, measure the impact, ship only when you have evidence.…