Powerlevel9k
Powerlevel9k was a tool for building a functional CLI
...However, Powerlevel9k is relatively heavy in terms of prompt rendering and status checks (e.g. querying Git status), which can make it slower on large repositories or slower machines. Over time, many users migrated or forked to lighter or faster versions (e.g. Powerlevel10k) that maintain compatibility with existing configuration. Despite performance trade-offs, it remains well known for combining aesthetics and utility in the Zsh ecosystem.