Some of the issues mentioned above like dead code removal, code duplication, unreachable code are already solved using deterministic linters for quite a while now for most language ecosystems.

You can get the LLM to run a script which checks for all of these and also enforce them by running the same script as a pre-commit hook. Setting this up religiously in every code base I work on has been what's given me the most mileage with agentic coding.

I wrote down a more detailed post of the various linters I use here:

https://www.balajeerc.info/Use-Deterministic-Guardrails-for-...