Can I ask how you set this up? Like is there some way to have that run automatically, similar to “auto mode” for approvals, or do you have to invoke it regularly?

Sure! I use an orchestrator main agent whose only job is to run subagents through the workflow process I've defined. Part of that workflow is to invoke a review subagent at particular points to check the spec, the implementation plan, and the code for rule conformance.

The review subagent has its own definition and gets invoked with a specific target, so the context is very focused on just rule enforcement and I don't have problems with it skipping rules.

The whole workflow is packaged up as a plugin, but you don't need that to get this approach to work. It should be sufficient to have the rules you want enforced written out somewhere, and to either kick off a focused review agent manually referencing them, or do something like I did and have it be a defined part of your workflow (depending on the automation level you want).

Hooks..

CI runs. Local Git hooks. Cursor also has hooks built into their agent. Other agent APIs probably have something similar.