The banned constructs per language were a table the agent read into context and applied by eye. defaults.py scans the added lines of git diff HEAD (or the index with --staged, or whole files with --file): Python through ast (parameter defaults, .get(k, v), getattr(o, n, v), os.environ.get / os.getenv with a value, add_argument(default=); None, False, empty strings and empty containers stay permitted, a mutable container as a parameter default is still reported), the other languages through masked regular expressions that skip strings and comments (shell, .env, Make, Dockerfile, Compose, YAML, Jinja, JS/TS, C#, Java, Rust, SQL, Terraform). Each hit prints file:line, language, construct and the replacement, marked candidate where it is often logic (??, || or or with a literal) or justified? next to a comment; exit 1 on hits.
The skill's detection step calls the script and the agent judges every hit; Go zero values, Helm values, Docker ENV placeholders and the judgement stay prose. constructs.md is gone. test_defaults covers every language, the permitted values, --staged, --file and the exit codes.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
