# Chain of Thought

> A collapsible step-by-step timeline for showing an AI assistant's reasoning or tool-execution trace, with per-step status, expandable output, and auto-close when all steps finish.

- Author: [nexus-ui](https://21st.dev/@nexus-ui)
- Library: Nexus UI
- License: MIT
- Tags: Timeline, Chat, AI, Collapsible, Reasoning
- npm dependencies: lucide-react
- Live preview: https://21st.dev/@nexus-ui/components/chain-of-thought

## Install

```bash
npx shadcn@latest add "https://21st.dev/r/nexus-ui/chain-of-thought?api_key=$API_KEY_21ST"
```

Requires a 21st API key (generate one at https://21st.dev/mcp) passed as `API_KEY_21ST`. Free accounts get a limited number of installs per day; unlimited on a paid plan — see https://21st.dev/pricing.

Full component directory: https://21st.dev/llms.txt · More like this: https://21st.dev/community/components/s/timeline.md