| Filename | Latest commit message | Latest commit date |
|---|---|---|
f6ebefe238* Add server selector to basic-host example - Add ServerSelector component to switch between MCP servers - Run all example servers concurrently on ports 3101-3107 - Update examples:start to launch all servers with assigned ports 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com> * Move server selector into tool call panel - Server selector now in same component as tool selector - Tool call results persist across server switches - Connection caching avoids reconnects when switching servers - Display server name with tool name in results (ServerName:ToolName) 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com> --------- Co-authored-by: Claude <noreply@anthropic.com> |
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| .. | ||
| src | ||
| index.html | ||
| package.json | ||
| README.md | ||
| sandbox.html | ||
| serve.ts | ||
| tsconfig.json | ||
| vite.config.ts | ||
Example: Basic Host
A reference implementation showing how to build an MCP Host application that connects to MCP servers and renders tool UIs in a secure sandbox.
This basic host can also be used to test MCP Apps during local development.
Key Files
index.html/src/index.tsx- React UI host with tool selection, parameter input, and iframe managementsandbox.html/src/sandbox.ts- Outer iframe proxy with security validation and bidirectional message relaysrc/implementation.ts- Core logic: server connection, tool calling, and AppBridge setup
Getting Started
npm install
npm run dev
# Open http://localhost:8080
Architecture
This example uses a double-iframe sandbox pattern for secure UI isolation:
Host (port 8080)
└── Outer iframe (port 8081) - sandbox proxy
└── Inner iframe (srcdoc) - untrusted tool UI
Why two iframes?
- The outer iframe runs on a separate origin (port 8081) preventing direct access to the host
- The inner iframe receives HTML via
srcdocand is restricted by sandbox attributes - Messages flow through the outer iframe which validates and relays them bidirectionally
This architecture ensures that even if tool UI code is malicious, it cannot access the host application's DOM, cookies, or JavaScript context.