TanStack Start Devtools MCP

Local development bridge between TanStack Devtools and MCP-capable coding agents.

This repo is clone-and-use local tooling, not an npm-published package. See INSTALL.md for setup instructions and an agent install prompt.

Packages

• @barreloflube/tanstack-start-dev-tool-mcp-shared: shared browser/server protocol schemas.

• @barreloflube/tanstack-start-dev-tool-mcp-react: React panel for @tanstack/react-devtools.

• @barreloflube/tanstack-start-dev-tool-mcp-server: MCP server plus local WebSocket bridge.

Related MCP server: mcacp

Development

pnpm install
pnpm dev:mcp

pnpm dev:mcp uses tsx watch, so edits to the MCP server restart the process automatically.

Environment

• TANSTACK_AGENT_DEVTOOLS_PORT: bridge port, defaults to 8129.

• TANSTACK_AGENT_DEVTOOLS_HOST: bridge host, defaults to 127.0.0.1.

• TANSTACK_AGENT_DEVTOOLS_TOKEN: shared browser/server token, defaults to tanstack-agent-devtools-local.

MCP Client Config

For stdio-based clients:

{
  "mcpServers": {
    "tanstack-start-devtools": {
      "command": "/Users/barreloflube/Desktop/tanstack-start-dev-tool-mcp/node_modules/.bin/tsx",
      "args": [
        "/Users/barreloflube/Desktop/tanstack-start-dev-tool-mcp/packages/mcp-server/src/cli.ts"
      ],
      "env": {
        "TANSTACK_AGENT_DEVTOOLS_TOKEN": "tanstack-agent-devtools-local"
      }
    }
  }
}

For stdio clients, launch tsx directly instead of pnpm mcp; package-manager lifecycle banners can corrupt the MCP JSON-RPC stream.

Codex launches its own MCP process. Stop pnpm dev:mcp before restarting Codex unless you are intentionally testing the watched development server.

Prompts used to build this

1. “i want to make a mcp server that allows the tanstack start dev tool's access to the agent. how should we go around making it”

2. “i want a sep personal repo for this.”

3. “you can make the sep repo in the Desktop/tanstack-start-dev-tool-mcp folder and work in there, import it here and start the mcp server test it, dont stop until it works, also support hmr for the mcp server so you can itereate quickly.”