That depends on the invariant. Some are behavioural, like "variable x must be even if y is positive", but some are architectural, such as "a new view requires a new class".
But that's only one side of the problem because maintaining the invariant can be just as bad as breaking it. You ask the agent to add a feature and it may well maintain the invariant - only it shouldn't have, because the feature uncovers the fact that the invariant is architecturally wrong.
The problem is that evolving software requires exercising judgment about when you need to follow the existing strategy and when you need to rethink it. If there is any mechanical rule that could state what the right judgment is, I don't know what it is.
