Introduction
The Knowledge Base covers common questions, architecture details, and practical guidance for building agents with 21st SDK. Use it as a reference alongside the Getting Started guide and API Reference.
Topics
Claude Code Agent
How to build, deploy, and embed a production AI agent powered by Claude Code - sandboxing, streaming, custom tools, and React UI.
Models & Providers
Use Claude, GPT, Gemini, DeepSeek, Llama, Qwen, GLM and more through OpenRouter. Compare models, switch at runtime, and optimize for cost or performance.
Messages & History
How message persistence works, lazy loading history, and restoring conversations on mount.
Sandboxes & Infrastructure
Sandbox specs, shared volumes, lifecycle hooks, concurrent users, and persistent storage.
Troubleshooting
Auth issues, missing messages, tool permission errors, and streaming problems.
Best Practices
Optimizing cost, choosing between skills and system prompts, and security considerations.
Can't find what you need?
If your question isn't covered here, check the API Reference for endpoint details or reach out on Discord.