MCP Servers with Internal addresses cannot be initialized without setting them in allowedDomains

[2000DS]

What happened?

I just updated from 0.8.1 to 0.8.2-rc2 and my mcp servers cannot be initialized anymore. I'm getting the error message that the mcp server domain is not on the list of allowed domains. PR #11013 mentions that if nothing is configured, all domains are allowed for backward compatibility. That seems not to be the case.

In my case I'm running librechat in a docker container.

This is my librechat.yaml:

version: 1.2.8
cache: true
endpoints:
  custom:
    - name: "LM Studio"
      apiKey: "lmstudio"
      baseURL: "http://172.24.1.165:1234/v1"
      models:
        default: ["qwen/qwen3-4b-2507"]
        fetch: true
      titleConvo: true
      titleMethod: "completion"
      titleModel: "current_model"
      summarize: false
      summaryModel: "current_model"
      forcePrompt: false
      modelDisplayLabel: "LM Studio"
    - name: "Ollama"
      apiKey: "ollama"
      # use 'host.docker.internal' instead of localhost if running LibreChat in a docker container
      baseURL: "http://172.24.1.165:11434/v1/"
      models:
        default: ["qwen3:4b-instruct-2507-q8_0"]
        # fetching list of models is supported but the `name` field must start
        # with `ollama` (case-insensitive), as it does in this example.
        fetch: true
      titleConvo: true
      titleModel: "current_model"
      summarize: false
      summaryModel: "current_model"
      forcePrompt: false
      modelDisplayLabel: "Ollama"
mcpServers:  
  prod_mcp:
    type: streamable-http
    url: http://172.24.1.165:8000/mcp
    timeout: 120000
  test_mcp:
    type: streamable-http
    url: http://172.24.1.165:8001/mcp

Also with the new MCP management UI it is not possible to add a new mcp server --> same error.

Version Information

da10815

Steps to Reproduce

1. Configure MCP server in librechat.yaml
2. Start librechat

What browsers are you seeing the problem on?

No response

Relevant log output

This is the log output on startup:

2026-01-09 10:17:04 info: RAG API is running and reachable at [http://rag_api:8000.⁠](http://rag_api:8000./)

2026-01-09 10:17:04 info: Server listening on all interfaces at port 3080. Use [http://localhost:3080⁠](http://localhost:3080/) to access it

2026-01-09 10:17:04 info: [MCPServersRegistry] Creating new instance

2026-01-09 10:17:04 error: [MCPServersRegistry] Failed to inspect server "fluro_mcp": Domain "http://172.24.1.165:8000" is not allowed

2026-01-09 10:17:04 error: [MCPServersRegistry] Failed to inspect server "test_mcp": Domain "http://172.24.1.165:8001" is not allowed

2026-01-09 10:17:04 error: [MCP][fluro_mcp] Failed to initialize: Domain "http://172.24.1.165:8000" is not allowed

2026-01-09 10:17:04 error: [MCP][test_mcp] Failed to initialize: Domain "http://172.24.1.165:8001" is not allowed

2026-01-09 10:17:04 info: [MCP] Initialized with 2 configured servers and 0 tools.

Screenshots

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[viastolfi]

Hi,
I’m seeing the same issue when deploying LibreChat on a Kubernetes cluster.

In my setup, LibreChat and the MCP servers are running within the same cluster. Even though the deployment method differs, this is a common point with the original report.

Without trying to solve the issue on behalf of the devs, I’m wondering if this could be related to MCP servers being hosted in the same network/cluster as LibreChat.

Hope this helps, and happy to share more details if needed.

[danny-avila]

You need to explicitly set these internal IPs in allowedDomains.

The docs need to be updated as we changed the default behavior to protect misuse of addresses local to the server hosting LibreChat.

[2000DS]

Allright, thanks for the fast clarification.

Where do I set the allowedDomains for mcp servers in the librechat.yaml?

Something like this?

mcpServers:  
  allowedDomains:
    - "172.24.1.165"
   my_mcp:
     type: streamable-http
     url: http://172.24.1.165:8000/mcp
     timeout: 120000

[dvejsada]

@2000DS No, a separate key in librechat.yaml, see below what works for us:

mcpSettings:
  allowedDomains:
    - "example.com" # For main domain only
    - "*.example.com" # For all subdomains
    - "mcp-xxxx" # For local docker domain
    - "192.158.5.12" # For specific IP