As a zellij sponsor I’ve been wondering the same.

I rebuild herdr from master every few days to gauge the direction it’s moving in.

What herdr gets right over zellij:

- Default keybinds don’t conflict with helix. Even the leader key mode in zellij keeps alt-bindings around. Herdr keeps things nicely tucked away.

- There’s beta support for the kitty image protocol. Three years on, we’re still waiting in zellij.

- Notifications get passed correctly through to the terminal.

As for herdr’s killer feature, agent status monitoring, there is apparently a zellij plugin.

Big win for zellij: the docs and code feel human. By contrast, herdr’s docs have all the tells of a vibe coded project. Not to say the maintainer hasn’t put care into it! But I’m getting burned out on LLM docs.