How a Clean Docker Container Exposed Hidden Global Dependencies in AI-Generated Code

A developer nearly shipped a feature-flag helper function that worked locally but crashed inside a clean Docker container with a NameError. The AI-generated function silently relied on three global variables — DEBUG, FEATURE_STORE, and DEFAULT_FEATURES — that were never declared as parameters or imports. The local environment happened to carry leftover globals from a previous session, masking the bug entirely during smoke testing. Running the same code in an empty namespace immediately revealed the hidden dependency. The developer resolved the issue by building an AST-based pre-execution check that identifies free globals in generated code before it leaves the test directory.