Rars: a Rust RAR implementation, mostly written by LLMs

A hobbyist built rars, a full RAR format compressor in Rust supporting multiple RAR versions, using OpenAI Codex 5.5 and Claude Opus 4.7 over 5 weeks at ~£40 cost. The 55k-line codebase demonstrates LLM-assisted reverse engineering at scale, compressing what would have been a multi-year project. Practitioners should note both the capability ceiling and quality tradeoffs of LLM-generated systems code.