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Connecting to Hugging Face login is broken #234

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Connecting to Hugging Face login is broken#234
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Highest PrioritybugSomething isn't working

Description

@matteo8p
matteo8p
opened on Jul 10, 2025

Issue

I recently read from this article that the Hugging Face MCP supports OAuth. The endpoint for their OAuth is https://huggingface.co/mcp?login. I am able to start the Auth flow and redirect, but I am unable to load the server on MCPJam

I tried it on the official inspector, and it works. However, it's broken on our end.

How to reproduce the bug

  1. Open MCPJam
  2. Connect to https://huggingface.co/mcp?login via Streamable HTTP
  3. Observe that you go through the log in flow, but after authenticating, it fails to connect.

Error message

[1] [INFO] Creating connection f1f2bd0e-44b5-4797-b7a3-6915c2dc27db for server-1752166602677
[1] [INFO] Creating sse transport for server-1752166602677
[1] [INFO] 🚀 SSE transport: url=https://huggingface.co/mcp?login
[1] [ERROR] Transport error for 7b5e4d7c-acad-4238-a250-e7929c099fb6: SseError: SSE error: Non-200 status code (405)
[1]     at EventSource._eventSource.onerror (/Users/matt8p/Desktop/inspector/node_modules/@modelcontextprotocol/sdk/src/client/sse.ts:153:23)
[1]     at EventSource.failConnection_fn (/Users/matt8p/Desktop/inspector/node_modules/eventsource/src/EventSource.ts:534:5)
[1]     at <anonymous> (/Users/matt8p/Desktop/inspector/node_modules/eventsource/src/EventSource.ts:374:7)
[1]     at process.processTicksAndRejections (node:internal/process/task_queues:95:5) {
[1]   code: 405,
[1]   event: {
[1]     type: 'error',
[1]     message: 'Non-200 status code (405)',
[1]     code: 405,
[1]     defaultPrevented: false,
[1]     cancelable: false,
[1]     timeStamp: 2622.219209
[1]   }
[1] }
[1] [ERROR] Failed to create transport for server-1752166602677: SseError: SSE error: Non-200 status code (405)
[1]     at EventSource._eventSource.onerror (/Users/matt8p/Desktop/inspector/node_modules/@modelcontextprotocol/sdk/src/client/sse.ts:153:23)
[1]     at EventSource.failConnection_fn (/Users/matt8p/Desktop/inspector/node_modules/eventsource/src/EventSource.ts:534:5)
[1]     at <anonymous> (/Users/matt8p/Desktop/inspector/node_modules/eventsource/src/EventSource.ts:374:7)
[1]     at process.processTicksAndRejections (node:internal/process/task_queues:95:5) {
[1]   code: 405,
[1]   event: {
[1]     type: 'error',
[1]     message: 'Non-200 status code (405)',
[1]     code: 405,
[1]     defaultPrevented: false,
[1]     cancelable: false,
[1]     timeStamp: 2622.219209
[1]   }
[1] }
[1] [ERROR] Failed to create connection f1f2bd0e-44b5-4797-b7a3-6915c2dc27db: SseError: SSE error: Non-200 status code (405)
[1]     at EventSource._eventSource.onerror (/Users/matt8p/Desktop/inspector/node_modules/@modelcontextprotocol/sdk/src/client/sse.ts:153:23)
[1]     at EventSource.failConnection_fn (/Users/matt8p/Desktop/inspector/node_modules/eventsource/src/EventSource.ts:534:5)
[1]     at <anonymous> (/Users/matt8p/Desktop/inspector/node_modules/eventsource/src/EventSource.ts:374:7)
[1]     at process.processTicksAndRejections (node:internal/process/task_queues:95:5) {
[1]   code: 405,
[1]   event: {
[1]     type: 'error',
[1]     message: 'Non-200 status code (405)',
[1]     code: 405,
[1]     defaultPrevented: false,
[1]     cancelable: false,
[1]     timeStamp: 2622.219209
[1]   }
[1] }
[1] ❌ Error in /sse route: SseError: SSE error: Non-200 status code (405)
[1]     at EventSource._eventSource.onerror (/Users/matt8p/Desktop/inspector/node_modules/@modelcontextprotocol/sdk/src/client/sse.ts:153:23)
[1]     at EventSource.failConnection_fn (/Users/matt8p/Desktop/inspector/node_modules/eventsource/src/EventSource.ts:534:5)
[1]     at <anonymous> (/Users/matt8p/Desktop/inspector/node_modules/eventsource/src/EventSource.ts:374:7)
[1]     at process.processTicksAndRejections (node:internal/process/task_queues:95:5) {
[1]   code: 405,
[1]   event: {
[1]     type: 'error',
[1]     message: 'Non-200 status code (405)',
[1]     code: 405,
[1]     defaultPrevented: false,
[1]     cancelable: false,
[1]     timeStamp: 2622.219209
[1]   }
[1] }
[1] 📥 Received POST message for sessionId undefined
[1] 🔄 New streamable-http connection
[1] [INFO] Creating connection 541739b3-6801-43fb-b934-d883e7d510e3 for server-1752166610202
[1] [INFO] Creating streamable-http transport for server-1752166610202
[1] [INFO] 🚀 StreamableHTTP transport: url=https://huggingface.co/mcp?login
[1] ✨ Connected MCP client to backing server transport for session 541739b3-6801-43fb-b934-d883e7d510e3
[1] [INFO] ✨ Created streamable web app transport 541739b3-6801-43fb-b934-d883e7d510e3
[1] [INFO] Web app transport set for session 541739b3-6801-43fb-b934-d883e7d510e3
[1] Error from MCP server: Error: Error POSTing to endpoint (HTTP 401): Unauthorized
[1]     at StreamableHTTPClientTransport.send (/Users/matt8p/Desktop/inspector/node_modules/@modelcontextprotocol/sdk/src/client/streamableHttp.ts:423:15)
[1]     at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
[1] 📥 Received POST message for sessionId undefined
[1] 🔄 New streamable-http connection
[1] [INFO] Creating connection 7503f0bc-1390-4361-8259-beb834358b8f for server-1752166611130
[1] [INFO] Creating streamable-http transport for server-1752166611130
[1] [INFO] 🚀 StreamableHTTP transport: url=https://huggingface.co/mcp?login
[1] ✨ Connected MCP client to backing server transport for session 7503f0bc-1390-4361-8259-beb834358b8f
[1] [INFO] ✨ Created streamable web app transport 7503f0bc-1390-4361-8259-beb834358b8f
[1] [INFO] Web app transport set for session 7503f0bc-1390-4361-8259-beb834358b8f
[1] 📥 Received POST message for sessionId undefined
[1] 🔄 New streamable-http connection
[1] [INFO] Creating connection 45c145ef-0233-45d8-b803-fb8935010f47 for server-1752166611138
[1] [INFO] Creating streamable-http transport for server-1752166611138
[1] [INFO] 🚀 StreamableHTTP transport: url=https://huggingface.co/mcp?login
[1] ✨ Connected MCP client to backing server transport for session 45c145ef-0233-45d8-b803-fb8935010f47
[1] [INFO] ✨ Created streamable web app transport 45c145ef-0233-45d8-b803-fb8935010f47
[1] [INFO] Web app transport set for session 45c145ef-0233-45d8-b803-fb8935010f47
[1] 📥 Received POST message for sessionId undefined
[1] 🔄 New streamable-http connection
[1] [INFO] Creating connection 98861f56-622d-4eef-9be8-caa31afa3e9c for server-1752166611141
[1] [INFO] Creating streamable-http transport for server-1752166611141
[1] [INFO] 🚀 StreamableHTTP transport: url=https://huggingface.co/mcp?login
[1] ✨ Connected MCP client to backing server transport for session 98861f56-622d-4eef-9be8-caa31afa3e9c
[1] [INFO] ✨ Created streamable web app transport 98861f56-622d-4eef-9be8-caa31afa3e9c
[1] [INFO] Web app transport set for session 98861f56-622d-4eef-9be8-caa31afa3e9c
[1] Error from MCP server: Error: Error POSTing to endpoint (HTTP 401): Unauthorized
[1]     at StreamableHTTPClientTransport.send (/Users/matt8p/Desktop/inspector/node_modules/@modelcontextprotocol/sdk/src/client/streamableHttp.ts:423:15)
[1]     at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
[1] Error from MCP server: Error: Error POSTing to endpoint (HTTP 401): Unauthorized
[1]     at StreamableHTTPClientTransport.send (/Users/matt8p/Desktop/inspector/node_modules/@modelcontextprotocol/sdk/src/client/streamableHttp.ts:423:15)
[1]     at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
[1] Error from MCP server: Error: Error POSTing to endpoint (HTTP 401): Unauthorized
[1]     at StreamableHTTPClientTransport.send (/Users/matt8p/Desktop/inspector/node_modules/@modelcontextprotocol/sdk/src/client/streamableHttp.ts:423:15)
[1]     at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
[1] 🔄 New sse connection
[1] [INFO] Creating connection 36c920dd-abea-4b0c-9b8a-d27337415ecd for server-1752166614352
[1] [INFO] Creating sse transport for server-1752166614352
[1] [INFO] 🚀 SSE transport: url=https://huggingface.co/mcp?login
[1] [ERROR] Transport error for ee531ade-7bcd-409d-9d44-bc6f49584205: SseError: SSE error: Non-200 status code (405)
[1]     at EventSource._eventSource.onerror (/Users/matt8p/Desktop/inspector/node_modules/@modelcontextprotocol/sdk/src/client/sse.ts:153:23)
[1]     at EventSource.failConnection_fn (/Users/matt8p/Desktop/inspector/node_modules/eventsource/src/EventSource.ts:534:5)
[1]     at <anonymous> (/Users/matt8p/Desktop/inspector/node_modules/eventsource/src/EventSource.ts:374:7)
[1]     at process.processTicksAndRejections (node:internal/process/task_queues:95:5) {
[1]   code: 405,
[1]   event: {
[1]     type: 'error',
[1]     message: 'Non-200 status code (405)',
[1]     code: 405,
[1]     defaultPrevented: false,
[1]     cancelable: false,
[1]     timeStamp: 14186.217292
[1]   }
[1] }
[1] [ERROR] Failed to create transport for server-1752166614352: SseError: SSE error: Non-200 status code (405)
[1]     at EventSource._eventSource.onerror (/Users/matt8p/Desktop/inspector/node_modules/@modelcontextprotocol/sdk/src/client/sse.ts:153:23)
[1]     at EventSource.failConnection_fn (/Users/matt8p/Desktop/inspector/node_modules/eventsource/src/EventSource.ts:534:5)
[1]     at <anonymous> (/Users/matt8p/Desktop/inspector/node_modules/eventsource/src/EventSource.ts:374:7)
[1]     at process.processTicksAndRejections (node:internal/process/task_queues:95:5) {
[1]   code: 405,
[1]   event: {
[1]     type: 'error',
[1]     message: 'Non-200 status code (405)',
[1]     code: 405,
[1]     defaultPrevented: false,
[1]     cancelable: false,
[1]     timeStamp: 14186.217292
[1]   }
[1] }
[1] [ERROR] Failed to create connection 36c920dd-abea-4b0c-9b8a-d27337415ecd: SseError: SSE error: Non-200 status code (405)
[1]     at EventSource._eventSource.onerror (/Users/matt8p/Desktop/inspector/node_modules/@modelcontextprotocol/sdk/src/client/sse.ts:153:23)
[1]     at EventSource.failConnection_fn (/Users/matt8p/Desktop/inspector/node_modules/eventsource/src/EventSource.ts:534:5)
[1]     at <anonymous> (/Users/matt8p/Desktop/inspector/node_modules/eventsource/src/EventSource.ts:374:7)
[1]     at process.processTicksAndRejections (node:internal/process/task_queues:95:5) {
[1]   code: 405,
[1]   event: {
[1]     type: 'error',
[1]     message: 'Non-200 status code (405)',
[1]     code: 405,
[1]     defaultPrevented: false,
[1]     cancelable: false,
[1]     timeStamp: 14186.217292
[1]   }
[1] }
[1] ❌ Error in /sse route: SseError: SSE error: Non-200 status code (405)
[1]     at EventSource._eventSource.onerror (/Users/matt8p/Desktop/inspector/node_modules/@modelcontextprotocol/sdk/src/client/sse.ts:153:23)
[1]     at EventSource.failConnection_fn (/Users/matt8p/Desktop/inspector/node_modules/eventsource/src/EventSource.ts:534:5)
[1]     at <anonymous> (/Users/matt8p/Desktop/inspector/node_modules/eventsource/src/EventSource.ts:374:7)
[1]     at process.processTicksAndRejections (node:internal/process/task_queues:95:5) {
[1]   code: 405,
[1]   event: {
[1]     type: 'error',
[1]     message: 'Non-200 status code (405)',
[1]     code: 405,
[1]     defaultPrevented: false,
[1]     cancelable: false,
[1]     timeStamp: 14186.217292
[1]   }
[1] }

Activity

  1. matteo8p
    added
    bugSomething isn't working
    Highest Priority
    on Jul 10, 2025

  2. matteo8p commented on Jul 11, 2025

    @matteo8p
    matteo8p
    on Jul 11, 2025
    ContributorAuthor

    Fixed #241

  3. matteo8p
    closed this as completedon Jul 11, 2025
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