The same busy afternoon, in Slack and in Zulip. Do four small tasks in each and see what changes.
Explained out loud, topic-based threading sounds like a small UI difference. The only way to feel that it isn't is to sit in a busy channel. So here is one: an afternoon in #engineering, thirty messages, five things going on at once. Below, the exact same messages appear in a replica of Slack and a replica of Zulip. Nothing is rewritten between the two — only organized differently.
| Task | Slack | Zulip | What happened |
|---|
None of these tasks is unusual. They are what a normal day in a busy channel is made of — and in a feed, every one of them gets harder as the team grows. So teams split into more and more channels, and then forget to check them.
With a topic on every conversation, none of that happens. You read one conversation at a time, skip the ones that don't concern you, mute the ones that never will, and pick up a thread days later without losing the context. A busy channel stops being a problem.
That's the core problem Zulip is built around: every conversation in every channel has a topic, and everything else — the inbox, resolving, following, moving messages between conversations — builds on that.