Someone shipped an open source alternative to Claude in Slack. 1 day after Anthropic launched it.

It's called OpenTag.

What you get:

→ Generative UI - renders charts, tables, and components inline inside Slack

→ Streaming replies with full thread context

→ Human-in-the-loop approval gates - agent waits for you before acting

→ One codebase. Slack, MS Teams, Discord, Telegram, WhatsApp.

→ MIT license - fully hackable

The entire agent behavior is controlled by one system prompt.

Rewrite it, you have a completely different agent.

Built on CopilotKit's open SDK. 35k+ GitHub stars. Created the AG-UI protocol.

Clone it, point it at your model and tools, and you own the whole stack.