AI Coding Guardrails

Coding agents fail in a small number of predictable ways. This is the checklist that catches them before the diff lands.

The Rules

1. Match the codebase, not your preferences. Read two or three neighbouring files before writing. Use the project's existing patterns, naming, error handling, and comment density — even when you would have done it differently. A diff that reads like the rest of the repo is the goal. Introducing a new pattern is a decision the user makes, not a default.

2. Change the smallest thing that works. No speculative abstraction. No config option nobody asked for. No "while I was in here" rewrite. If a fix is three lines, the diff is three lines. Refactors ride separately from behavior changes so a reviewer can see one thing at a time.

3. Never invent an API. If you cannot see a function's signature in the repo, in installed source, or in the documentation, do not call it. Grep for it first. A plausible-looking method that does not exist is the single most common way agent code fails, and it fails at runtime, in front of the user.

4. Verify before claiming. "Done" means you ran something and saw it pass. Build, test, hit the endpoint, load the page. If you did not run it, say "untested". Reporting success you did not observe is worse than reporting nothing.