native messaging is a huge headache to set up reliably across all the OSs and (often headless) chrome setups in our experience, that's why we've avoided it.

Just using some remote endpoint message bus service is an easier solution, or something like ElectricSQL/RxDB/Replicache/etc.

We also can't really use in-page JS for much because it's easily detected by bot-blockers, though isolated worlds help in CDP.