Large legacy projects are where LLMs are the worst, historically. And I suspect the hard part of Linux isn't typing things, and that the rigorous spec required to get an LLM to generate the correct code is basically the code itself.

I'm reminded of some of the coding stories at NASA where there'd be a ton of discussion for just a few lines of code. And the space shuttle code was apparently some of the most defect-free coffee ever written.

My hypothesis:

Linux kernel is a huge project - with a lot of people volunteering. You’d be burning through a crazy amount of input tokens to gain enough context to get any work done. I doubt many volunteers pay for their own top-tier subscription plans that would be able to do so cost-effectively.

Embedded code and systems code tends to have a lot of extra constraints the model doesn't know about and aren't necessarily written down where it can see. This produces a higher rate of "superficially plausible but doesn't actually work" code.

(There are probably wider benchmarks, but this was a definite finding in our company wide evaluation of effectiveness. LLMs aren't great at RTL either)

The Linux kernel is essentially the nightmare scenario for a LLM.

No tests, not much documentation to work with, a very high acceptability bar, multiple ways to do the smallest change and every single word on your commit messages is very important.

You can start with a LLM but there going to be some manual modifications you will have to make, even with the best model available

Small changes can have a huge impact.. far beyond your context window ;-)

How big is your circle? What industries does it span? Maybe the people writing 0% code manually are outliers and your circle is relatively small?

I would assume that linux devs are relatively older. Furthermore they are probably very knowledgeable in that area, and one thing I've noted on here is people who are knowledgeable not liking the quality of code output from LLMs, if they have stringent quality requirements it might be easier for them to write the code themselves.