I was looking it last night and the repo is something like 600k lines of Zig. Maybe 500k after comments and blank lines.
In my own experiments to build a tiny zig agent it came out to under 800kb.
I think the problem is that when you use agents to write Zig it will bruteforce code, because there isn't that much good reference code to work off of.
I'm always surprised how large harnesses are
By comparison, the recently open sourced grok harness was 840k lines, codex 950k, pi 250k https://simonwillison.net/2026/Jul/15/grok-build/