Host matrix

Run mountly-mcp dev while you iterate. Ship the same dist/ artifacts to a real host over the transport you choose.

Local preview

pnpm dev   # scaffold: mountly-mcp dev --server ./server.mjs

You exercise handshake, CSP, tool results, and View-initiated tool calls. Open the App once in Claude or VS Code before you call it done.

Host status

Host	Status	Connect
mountly-mcp dev	Supported	Built-in AppBridge + sandbox proxy
Claude Desktop	Supported (stdio)	claude_desktop_config.json → node + serve-stdio.mjs
VS Code MCP	Supported (stdio)	.vscode/mcp.json → same stdio entry
ChatGPT	Partial	Custom connector or hosted HTTP MCP; you own OAuth
Other SEP-1865 hosts	Untested here	Same manifest if the host implements ui://

“Untested” means this repo has no CI against that host. Do not assume coverage.

Stdio entry

Scaffolds ship serve-stdio.mjs:

import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import createServer from "./server.mjs";

const server = await createServer();
await server.connect(new StdioServerTransport());

Log to stderr. stdout is the JSON-RPC channel.

Claude Desktop

~/Library/Application Support/Claude/claude_desktop_config.json (macOS):

{
  "mcpServers": {
    "my-app": {
      "command": "node",
      "args": ["/absolute/path/to/serve-stdio.mjs"]
    }
  }
}

VS Code

.vscode/mcp.json:

{
  "servers": {
    "my-app": {
      "type": "stdio",
      "command": "node",
      "args": ["${workspaceFolder}/serve-stdio.mjs"]
    }
  }
}

ChatGPT

Point your connector at the same stdio process or at an HTTP transport you deploy. Mountly does not ship OAuth or hosting.

Before host smoke

npx mountly-mcp build
npx mountly-mcp verify --strict --render

--render fails blank Views in Chromium. Host screenshots stay manual until each vendor exposes stable automation.

Text-only hosts

Hosts without MCP Apps still get tool text: Mountly adds a JSON text block when your handler returns only structuredContent. How it works.