From my experience a good thing to do is to set up strong static code analysis (like eslint, TypeScript strict mode, IntelliJ inspections, Sonarqube, ...) when

From my experience a good thing to do is to set up strong static code analysis (like eslint, TypeScript strict mode, IntelliJ inspections, Sonarqube, ...) when the project begins. This helps to avoid some endless discussions and some bugs. Another upside is, that the rules are enforced automatically what is better than to remind your colleagues each and every time when the break the rules. With a set of rules written down as a config file for a code analysis tool, there is a definition of clean code (even if not a complete one). Starting with overly strong rules and relaxing them later is better than starting with loose rules and tighten them later, because it would require much refactoring to introduce a new rule, whereas dropping a rule is a thing of a few seconds.