I am working on an agent implementation that you might like: https://github.com/OleksandrChekhovskyi/hax

Written in C, tiny footprint, minimalist approach to system prompt and tools (yet essential batteries are included, for example - it has subagents with presets, and background bash tasks out of the box), high quality polished presentation, inspectable (usable transcript view), does not mess with terminal scrollback, respects XDG directory spec, etc.

Open source, MIT-licensed, no commercial agenda. A tool that I myself wanted, so I built it.