When does an AI-built internal tool break down, and when should I bring in a professional developer?

The community calls it the Spaghetti Point: around month three, new features start breaking old ones because generated code was never read, and rescue engineering on a grown app can run $50k or more. The signals to get help are consistent: recurring data-integrity bugs, a one-day feature taking weeks, or the first time real money or customer data flows through the tool. Keep AI-built tools on internal, low-blast-radius jobs, and budget a professional hardening pass (typically 2-4x the original build time) before anything becomes business-critical.

A quick orientation. The real value is below: resources worth your time, from people who've actually done it.