One thing I'd add from the enterprise side, where codebases tend to be measured in decades rather than years: the golden files principle runs into a wall when the "approved pattern" in the codebase is itself a workaround for something nobody documented. I've seen teams point AI to golden files that were golden by convention, not by design — the file was just the one nobody broke. The AI learns the workaround as the standard, and the instructions quietly encode technical debt as policy.