Had anybody success in using MCP server in WebUI?

[TheItschi]

Can anybody give me a hint on how to get "Brave search MCP" server running with the WebUI of llama.cpp? I did setup "Brave search MCP" in Docker (https://github.com/Shoofio/brave-search-mcp-sse) and it starts correct according to the logs. I can cannect to it with the browser too.

I added --webui-mcp-proxy as start parameter for llama-sever

Configured http://192.168.100.100:8088/sse as MCP server (beeing [192.168.100.100:8088 my mcp server)

The llama.cpp WebUI gives me a Streamable HTTP error: Error POSTing to endpoint: 8f <title> error

The llama-server shows

srv proxy_reques: proxying POST request to http://192.168.100.100:8088/sse

srv log_server_r: done request: POST /cors-proxy 192.168.100.79 404

Wherer 192.168.100.79 is my browser client running th llama.cpp WebUI.

[c64z89]

No luck here either :c

I get the error with Tavily: {"error":{"code":500,"message":"invalid URL: no scheme","type":"server_error"}}

I also have these error messages in the MCP config in the webui itself:
01:34:12
Transport ready (streamable_http)
01:34:12
Sending initialize request...
01:34:13
Connection failed: Failed to fetch

[TheItschi]

Did you start llama-server with --webui-mcp-proxy as parameter? I got mine working last night with the use of the original mcp/brave-search repo.

This is the docker-compose.yaml that made it for me:

services:
  mcp-server:
    image: mcp/brave-search
    container_name: brave-search
    cap_drop:
      - all
    deploy:
      restart_policy:
        condition: any
        delay: 5s
    environment:
      - BRAVE_API_KEY=YourApiKey
      - BRAVE_MCP_TRANSPORT=http
      - BRAVE_MCP_PORT=8080
      - BRAVE_MCP_STATELESS=true
    init: true
    ports:
      - 8089:8080

Of curse you would need to insert your Brave API-Key and change the port section to what you want. These are the llama.cpp-server settings in the WebUI (change the IP and port to your Docker machine and the port you set in the compose file above):

[c64z89]

Thanks! And yep I started it with the webui proxy to no avail :/

[ywiyogo]

@TheItschi I copied your docker-compose-yml.
The output of docker compose logs after starting the container is:

brave-search  | Server is running on http://0.0.0.0:8080/mcp

Then, I add a new MCP server on the WebUI with this URL: http://0.0.0.0:8090/mcp. It shows error:

19:01:01 Creating transport for http://0.0.0.0:8090/mcp
19:01:01 Transport ready (streamable_http)
19:01:01 Sending initialize request...
19:01:01 Connection failed: Streamable HTTP error: Error POSTing to endpoint: proxy error: Could not establish connection

changing to http://localhost:8090/mcp shows the same error. I start the llama-server with --webui-mcp-proxy and enable "use llama server proxy".

Any clue?

[Green-Sky]

Looks like llama.cpp does not support the "sse" variants of the protocol.

[TheItschi]

It does, as you can see in my example above. 192.168.100.100:8098/mcp is a sse sever.

[standby24x7]

https://github.com/ggml-org/llama.cpp/blob/master/tools/server/webui/src/lib/services/mcp.service.ts#L95

/**
* Create transport based on server configuration.
* Supports WebSocket, StreamableHTTP (modern), and SSE (legacy) transports.
* When useProxy is enabled, routes HTTP requests through llama-server's CORS proxy.
*
* Fallback Order:
* 1. WebSocket — if explicitly configured (no CORS proxy support)
* 2. StreamableHTTP — default for HTTP connections
* 3. SSE — automatic fallback if StreamableHTTP fails

[Green-Sky]

Odd, not my experience.

[c64z89]

I think somebody else has a similar problem:

#20666

[c64z89]

Success! I had to click the pen icon to modify the already set up connection then toggle the "use llama-server proxy" button that shows up here. Now MCP is working.

[TheItschi]

We should suggest a change request for that. I dont understand why the proxy switch isn't displayed if you add a MCP server but if you change an existing it is.

[gogich77]

My interpretation of the situation.
JavaScript client ( in the browser ) use CORS security . Use the Web Browser Network Debugger tool to see the issue.

Example of a MCP Server that works . (I didn't use the mcp llama_server settings from the command line yet)

[zkirill]

I managed to get WebUI to work with local FastMCP. The trick was to set the Server URL to 127.0.0.1 instead of localhost, since my FastMCP was listening on http://127.0.0.1:8081/mcp by default.

[jansenicus]

I use the flag --ui-mcp-proxy then finally it accepts CORS

Common params

Argument	Explanation
--webui-mcp-proxy, --no-webui-mcp-proxy	[DEPRECATED: use --ui-mcp-proxy/--no-ui-mcp-proxy] experimental: whether to enable MCP CORS proxy (env: LLAMA_ARG_WEBUI_MCP_PROXY)
--ui-mcp-proxy, --no-ui-mcp-proxy	experimental: whether to enable MCP CORS proxy - do not enable in untrusted environments (default: disabled) (env: LLAMA_ARG_UI_MCP_PROXY)