Data from six months of production from one SaaS codebase provides a more limited response. Maintainability doesn't depend on the level of AI usage. Maintainability depends on the discipline during diff reviews. Good sessions: One topic per session; scope defined prior to the agent starting; all diffs read prior to committing. Poor sessions: Broad scope; undefined constraints; rubber-stamped results.

The quality of the codebase decays precisely at the rate you stop reading the results. This is not an issue of AI writing the code. This is an issue of unreviewed code. geohot's issue is entirely valid. This problem does exist. But this isn't dependent on the generation phase.