Air-Gapped Dev Environment?

Hello HN, there are a lot of great AI tools out there for coding at the moment but what many of them seem to have in common is streaming data to a cloud server somewhere.

I am trying to learn what options exist out there that would let someone develop software with "all the amenities" in a nearly or actually fully airgapped environment. Bonus points for low-power consideration.

So version control, LLM, Agent, etc. but assume no access to the internet. Local hub server on a LAN is okay to assume. I am thinking a tower under a desk and one or more people working on a laptop.

For context, the situation I'm thinking of is a friend who does a lot of environmental field research in remote locations (like truly middle of nowhere places). Sometimes the local office will have decent internet but most of the time it's a situation with a super spotty or non-existent connection. Remarkably, people still need to write code in environments like this at times!

Any and all answers very much appreciated, thank you.