How do you test shorter agent instructions for changes in meaning?
Shortening a coding agent's system prompt sounds harmless until meaning quietly drifts — one builder caught keyword-coverage tests missing intentional flips like 'stop only for P0' becoming 'stop only for P1'. Verbatim checks are brittle against paraphrases. The recommended approach: behavioral probes, concrete scenarios where only the correct instruction produces the right action. Test the decisions, not the wording.