Convex MCP errors for local projects

[fubz]

I have a local convex deployment that I am unable to connect to the mcp server.

I started the dev server with: npx convex dev --local

I added the mcp to claude code with: claude mcp add-json convex '{"type":"stdio","command":"npx","args":["convex","mcp","start"]}'

● convex - status (MCP)(projectDir: "/home/user/my-cool-project")
⎿ Error: {"error":"Not Authorized: Run npx convex dev to login to your Convex project."}

[thomasballinger]

What happens when you run npx convex dev in that directory?

[fubz]

Both dashboard and web client startup.

npx convex dev
✔ Started running a deployment locally at http://127.0.0.1:3210 and saved its name as CONVEX_DEPLOYMENT to .env.local
Run `npx convex login` at any time to create an account and link this deployment.

Write your Convex functions in convex/
Give us feedback at https://convex.dev/community or support@convex.dev
View the Convex dashboard at http://127.0.0.1:6790/?d=anonymous-app4fun

✔ 20:04:57 Convex functions ready! (743.35ms)

---

.env.local contains the CONVEX_URL=http://127.0.0.1:3210 and CONVEX_DEPLOYMENT=anonymous:anonymous-app4fun

---

Here are the mcp-logs-convex. They indicate an authorization error but I am not trying to use the cloud hosting options.

[
  {
    "debug": "Starting connection attempt",
    "timestamp": "2025-08-26T00:05:19.617Z",
    "sessionId": "a6b040cd-208f-450a-ae13-6a982a8c06b5",
    "cwd": "/home/user/Projects/app4fun"
  },
  {
    "debug": "Starting connection attempt",
    "timestamp": "2025-08-26T00:05:19.621Z",
    "sessionId": "a6b040cd-208f-450a-ae13-6a982a8c06b5",
    "cwd": "/home/user/Projects/app4fun"
  },
  {
    "debug": "Starting connection attempt",
    "timestamp": "2025-08-26T00:05:19.621Z",
    "sessionId": "a6b040cd-208f-450a-ae13-6a982a8c06b5",
    "cwd": "/home/user/Projects/app4fun"
  },
  {
    "debug": "Connection attempt completed in 363ms - status: connected",
    "timestamp": "2025-08-26T00:05:19.981Z",
    "sessionId": "a6b040cd-208f-450a-ae13-6a982a8c06b5",
    "cwd": "/home/user/Projects/app4fun"
  },
  {
    "debug": "Connection attempt completed in 360ms - status: connected",
    "timestamp": "2025-08-26T00:05:19.981Z",
    "sessionId": "a6b040cd-208f-450a-ae13-6a982a8c06b5",
    "cwd": "/home/user/Projects/app4fun"
  },
  {
    "debug": "Connection attempt completed in 362ms - status: connected",
    "timestamp": "2025-08-26T00:05:19.983Z",
    "sessionId": "a6b040cd-208f-450a-ae13-6a982a8c06b5",
    "cwd": "/home/user/Projects/app4fun"
  },
  {
    "debug": "Calling MCP tool: status",
    "timestamp": "2025-08-26T00:06:11.899Z",
    "sessionId": "a6b040cd-208f-450a-ae13-6a982a8c06b5",
    "cwd": "/home/user/Projects/app4fun"
  },
  {
    "error": "{\"error\":\"Not Authorized: Run `npx convex dev` to login to your Convex project.\"}",
    "timestamp": "2025-08-26T00:06:11.906Z",
    "sessionId": "a6b040cd-208f-450a-ae13-6a982a8c06b5",
    "cwd": "/home/user/Projects/app4fun"
  }
]

[JustYannicc]

Following same issue.