I personally build rules using static analysis tools. All my guardrails hook into my .NET static analyzer pipeline. This makes the agent fail at build time then it goes and corrects itself.

Additionally, .NET added a bunch of formatting rules in its static analyzer for .NET 11 that give greater control on the styling of the code the agent generates. For example you can ban `=>` function syntax using editorconfig. The build will fail and the agent has to adjust.