Prompt Engineering Fails Quietly —  Prompt Regression Is Why

Prompt Engineering often fails due to vague instructions that force models to guess roles and formats, leading to inconsistent outputs. To ensure reliability, developers should treat prompts as reusable specs rather than one-off questions, clearly defining roles and expected outputs. Additionally, small prompt changes can cause silent regressions in production. Implementing a practical framework to detect these hidden failures is essential to maintain critical behavior and ensure high-quality performance before users encounter issues.