I had a quick look, the implementation is interesting Node uses undici JS library. Undici includes a C HTTP parser that is used via webassembly. The parser is

I had a quick look, the implementation is interesting Node uses undici JS library. Undici includes a C HTTP parser that is used via webassembly. The parser is generated from rules that are implemented in JS/TS using llparse framework. A native C binary there in the middle is quite surprising.