Unknown connection regression #699
Description
Describe the bug
Note in the screenshot below with version 0.16.3, the initialization request is successful, but it says there's an error connecting:
In 0.16.2 the connection works without issue:
To Reproduce
Steps to reproduce the behavior:
git clone https://github.com/epicweb-dev/epic-me-mcp.git
cd ./epic-me-mcp
git checkout a34cb30e8fb921b6d28341e8ddff20693bd214a3
npm install
npm run dev
In another tab:
npx @modelcontextprotocol/[email protected]
Connect to http://localhost:8787/mcp over streamable http
Expected behavior
Connection should show as successful and it should show the tools.
Logs
All logs appear normal, check them out below:
inspector logs
npx @modelcontextprotocol/[email protected]
Need to install the following packages:
@modelcontextprotocol/[email protected]
Ok to proceed? (y)
Starting MCP inspector...
⚙️ Proxy server listening on localhost:6277
🔑 Session token: 31e0f9a5899dd05457dc93fe8fe07337b786584f20f62b0bf0073334327dcad1
Use this token to authenticate requests or set DANGEROUSLY_OMIT_AUTH=true to disable auth
🚀 MCP Inspector is up and running at:
http://localhost:6274/?MCP_PROXY_AUTH_TOKEN=31e0f9a5899dd05457dc93fe8fe07337b786584f20f62b0bf0073334327dcad1
🌐 Opening browser...
New StreamableHttp connection request
Query parameters: {"url":"http://localhost:8787/mcp","transportType":"streamable-http"}
Created StreamableHttp server transport
Created StreamableHttp client transport
Client <-> Proxy sessionId: 5175848e-3e9f-4d1a-8fbb-8e3ec64d1599
Error from MCP server: Error: Error POSTing to endpoint (HTTP 401): {"error":"invalid_token","error_description":"Missing or invalid access token"}
at StreamableHTTPClientTransport.send (file:///Users/kentcdodds/.npm/_npx/7e8b431f3a526226/node_modules/@modelcontextprotocol/sdk/dist/esm/client/streamableHttp.js:284:23)
at process.processTicksAndRejections (node:internal/process/task_queues:105:5)
New StreamableHttp connection request
Query parameters: {"url":"http://localhost:8787/mcp","transportType":"streamable-http"}
Created StreamableHttp server transport
Created StreamableHttp client transport
Client <-> Proxy sessionId: 91484b63-9d2c-4384-af77-dcee85104bc5
Proxy <-> Server sessionId: fa1f46413b2235a12f1befeee4345a33fb8ea8c6cb6031ab8d5031127841dca9
Received POST message for sessionId 91484b63-9d2c-4384-af77-dcee85104bc5
Received GET message for sessionId 91484b63-9d2c-4384-af77-dcee85104bc5
Received POST message for sessionId 91484b63-9d2c-4384-af77-dcee85104bc5MCP Server Logs
npm run dev
> dev
> wrangler dev
⛅️ wrangler 4.28.1
───────────────────
Using vars defined in .env
Your Worker has access to the following bindings:
Binding Resource Mode
env.EPIC_ME_MCP_OBJECT (EpicMeMCP) Durable Object local
env.OAUTH_KV (8008746588ab4b6e8d3396cdb588700f) KV Namespace local
env.EPIC_ME_DB (epic-me) D1 Database local
env.MOCKS ("(hidden)") Environment Variable local
╭──────────────────────────────────────────────────────────────────────╮
│ [b] open a browser [d] open devtools [c] clear console [x] to exit │
╰──────────────────────────────────────────────────────────────────────╯
⎔ Starting local server...
[wrangler:info] Ready on http://localhost:8787
▲ [WARNING] OAuth error response: 401 invalid_token - Missing or invalid access token
[wrangler:info] POST /mcp 401 Unauthorized (6ms)
[wrangler:info] OPTIONS /.well-known/oauth-protected-resource/mcp 404 Not Found (1ms)
[wrangler:info] GET /.well-known/oauth-protected-resource/mcp 404 Not Found (0ms)
[wrangler:info] OPTIONS /.well-known/oauth-protected-resource 404 Not Found (0ms)
[wrangler:info] GET /.well-known/oauth-protected-resource 404 Not Found (0ms)
[wrangler:info] OPTIONS /.well-known/oauth-authorization-server/mcp 404 Not Found (0ms)
[wrangler:info] GET /.well-known/oauth-authorization-server/mcp 404 Not Found (1ms)
[wrangler:info] GET /.well-known/oauth-authorization-server 200 OK (1ms)
[wrangler:info] POST /oauth/register 201 Created (4ms)
Starting migration process...
Schema versions table ready
Current schema version: 1
Migration process completed successfully
[wrangler:info] GET /authorize 302 Found (8ms)
[wrangler:info] OPTIONS /.well-known/oauth-protected-resource/mcp 404 Not Found (1ms)
[wrangler:info] GET /.well-known/oauth-protected-resource/mcp 404 Not Found (0ms)
[wrangler:info] OPTIONS /.well-known/oauth-protected-resource 404 Not Found (1ms)
[wrangler:info] GET /.well-known/oauth-protected-resource 404 Not Found (1ms)
[wrangler:info] OPTIONS /.well-known/oauth-authorization-server/mcp 404 Not Found (0ms)
[wrangler:info] GET /.well-known/oauth-authorization-server/mcp 404 Not Found (1ms)
[wrangler:info] GET /.well-known/oauth-authorization-server 200 OK (0ms)
[wrangler:info] POST /oauth/token 200 OK (4ms)
Starting migration process...
Schema versions table ready
Current schema version: 1
Migration process completed successfully
{
displayMessage: 'State updated',
id: '0lryhIIjknIIqeXaIn7ng',
payload: { previousState: {}, state: { userId: null } },
timestamp: 1754949017002,
type: 'state:update'
}
[wrangler:info] POST /mcp 200 OK (14ms)
[wrangler:info] POST /mcp 202 Accepted (3ms)
Connection established
Connection FRbEJZjSMT1I8IU_7CYwc connected to _a:0542610fbeefbb5bc80ff66f1e04439bfffe8f02b50ba43969ec696b1000896a
[wrangler:info] POST /mcp 200 OK (3ms)
[wrangler:info] GET /mcp 405 Method Not Allowed (1ms)
Connection established
Connection OdOxxjlIz0peb-cESP_PQ connected to _a:0542610fbeefbb5bc80ff66f1e04439bfffe8f02b50ba43969ec696b1000896a
Connection established
Connection eKr5cvSpGnedKRVmGlw0d connected to _a:0542610fbeefbb5bc80ff66f1e04439bfffe8f02b50ba43969ec696b1000896aAdditional context
I'm pretty sure the 404s on the /.well-known are acceptable and the 405 on the GET /mcp is fine as well (though I did raise an issue about that over here cloudflare/agents#403).