"Transient error connecting to streamableHttp server: fetch failed, MCP HTTP exchange failed"

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1

Hi, I try to setup MCP server for gerrit but it doesn’t want to work. I have no idea why.

5

Hey @Marcin_Pietrzak, thanks for the report.

fetch failed here means Cursor never got any response from the Gerrit MCP server (the request failed before it reached HTTP). That is almost always one of three things: the hostname does not resolve (for example when the VPN is not connected), the server uses a company-issued TLS certificate that the client does not trust, or a proxy is in the way. Your other MCP server connects fine, so this looks specific to the Gerrit one.

Could you run through these and reply with what you see?

  1. Paste the Gerrit entry from your mcp.json with any tokens removed. Is it a url server, and does the URL point to an internal hostname or to localhost?
  2. While connected to your company network, open that same URL in your browser. Does a page load (an error or login page is fine), or do you get a certificate warning or “site cannot be reached”?
  3. In a terminal with Node.js installed, run this with your real URL and paste the output:
    node -e "fetch('https://YOUR-GERRIT-MCP-URL').then(r=>console.log('OK',r.status)).catch(e=>console.log('FAIL',e.cause?.code??e.message))"
  4. Run the same command once more with the --use-system-ca flag added, and paste that output too:
    node --use-system-ca -e "fetch('https://YOUR-GERRIT-MCP-URL').then(r=>console.log('OK',r.status)).catch(e=>console.log('FAIL',e.cause?.code??e.message))"
  5. In Cursor, open View → Output, choose MCP Logs in the dropdown, then in Cursor Settings → Tools & MCP click the refresh icon on the Gerrit server and paste the lines that appear.

The FAIL code from steps 4 and 5 (for example, ENOTFOUND or UNABLE_TO_VERIFY_LEAF_SIGNATURE) tells us exactly what is blocking the connection!

7

Hi Colin,
Thanks for responding.

1. Where to paste the url ?

2. After URL address opening attempt in the browser I got the window looking as I would try to open json file in a browser, with the message

error “failed to parse authentication credentials”"

3. I got the response: “OK 401”

4. I got the response: “OK 401”

5. In Cursor Version: 3.21.16
VS Code Extension API: 1.128.0
Commit: 8ae78e8eee1e63479c7e0504b664bc0a80c68000
Date: 2026-09-19T06:43:22.276Z
there is no such setting path. I can only find MCPs in Customize, but I do not have Refresh icon, and the Reload button is not active there. In the MCP logs I can only see one record:
“2026-09-23 08:46:23.867 [info] [cursor-mcp] Sandbox prerequisites configured for stdio MCP: supported=true”.

8

Hi @Colin
Do you have any further instructions/proposals?

16

Hey @Marcin_Pietrzak, sorry for the slow reply, and thanks for running those checks.

The OK 401 result is good news: your machine can reach the Gerrit MCP server and trusts its certificate. The 401 and failed to parse authentication credentials just mean the server wants credentials, which is expected for a plain request with no token.

So the difference is inside Cursor. Unlike the node test, Cursor sends MCP traffic through your system proxy settings, so the most likely cause is that the proxy route to the Gerrit host fails. Could you try this:

  1. Open your mcp.json file. On Windows it is at C:\Users\<you>\.cursor\mcp.json, on macOS/Linux at ~/.cursor/mcp.json (or .cursor/mcp.json inside your project). Paste the Gerrit entry here with any tokens or passwords replaced by xxx.
  2. Press Ctrl+Shift+P (Cmd+Shift+P on Mac), run Preferences: Open User Settings (JSON) and add this line with your real Gerrit hostname: "http.noProxy": ["your-gerrit-host.example.com"] (keep the square brackets).
  3. Fully quit Cursor and reopen it.
  4. Go to Customize > MCPs and switch the Gerrit server off and back on.
  5. Open View > Output and pick MCP: user-mcp-gerrit in the dropdown (not MCP Logs, which only shows general startup lines in this version). Paste the lines that appear, and let me know which OS you are on.

Also, if a colleague already has the Gerrit MCP working in Cursor, it is worth comparing your mcp.json entry with theirs (URL and headers), since a small difference there can cause this too.

If it connects after that, you will probably see an authentication error next, because the server answered 401. At that point we can set up the right headers entry for your Gerrit credentials.