C++

Modern LLMs are chat models that use Jinja2 templates to format conversations. But Jinja is Python-centric, making deployment hard in C and edge environments. Here's how to build a Jinja2 template engine from scratch in C — covering lexing, parsing, and evaluation — so you can render chat templates natively without Python.

I gave Claude Opus 4.6 and GPT 5.4 the same task: rewrite pigz (a parallel gzip tool) in modern C++23. After 70 minutes, one delivered a clean-room rewrite, the other a wrapper around the old code. Then I pushed the winner to beat pigz — and it did.