The Agent Rewrote the Shell Script in Python and Dropped the Exit Code

AI agents are refactoring legacy code, such as converting if/else chains into lookup maps and porting bash scripts to Python. While the resulting code appears cleaner and passes linters, critical functional losses occur. In one instance, an agent removed side effects from a status mapping function. In another, a Python port omitted the implicit failure modes of set -euo pipefail, causing CI to report success despite npm test failures and deploying stale artifacts.