Being left with an unfamiliar codebase is always a concern and comes about through regular attrition, particularly if inadequate review is not in place or people are cycling in and out of the org too fast for proper knowledge transfer (so, cultural problems basically).

If anything, I'd bet that agent-written code will get better review than average because the turn around time on fixes is fast and no one will sass you for nit-picking, so it's "worth it" to look closely and ensure it's done just the way you want.