"Configuration file not found" error when installing extension

[medal-io]

What happened?

Gemini CLI Extension Installation Bug Report

Summary

The official Gemini CLI extension installation command gemini extensions install <github-url> consistently fails with the error:

Configuration file not found at /tmp/gemini-extensionXXXXXX/gemini-extension.json

This occurs even when the gemini-extension.json file exists at the root of the repository.

What did you expect to happen?

Steps to Reproduce

Test Case 1: Context7 Extension

gemini extensions install https://github.com/upstash/context7

Expected Result:
Extension should install successfully

Actual Result:

Configuration file not found at /tmp/gemini-extensionWxk0Af/gemini-extension.json

Test Case 2: GitHub MCP Server

gemini extensions install https://github.com/github/github-mcp-server

Expected Result:
Extension should install successfully

Actual Result:

Configuration file not found at /tmp/gemini-extensionLaky9x/gemini-extension.json

---

Client information

Client Information

Run gemini to enter the interactive CLI, then run the /about command.

> /about
About Gemini CLI                              │
│                                               │
│ CLI Version     0.9.0                         │
│ Git Commit      a93d92a3                      │
│ Model           gemini-2.5-pro                │
│ Sandbox         no sandbox                    │
│ OS              linux                         │
│ Auth Method     OAuth           

Login information

No response

Anything else we need to know?

Misleading AI Response

When querying Google's Gemini AI about this issue, it incorrectly attributed the problem to branch naming (master vs main), which testing proved to be false. This may indicate:

• The AI model is not aware of this bug
• Similar issues may have been reported but misdiagnosed

[swissspidy]

As far as I can tell, Gemini CLI downloads the latest release of a repository and tries to install it from there. Neither of these two repositories have had a release since they've added the extension manifest file.

You should be able to work around this by installing the version from the main branch, like so: gemini extensions install https://github.com/github/github-mcp-server.git --ref=main

That said, the logging & error message could be much improved here so it's easier to know what's going on.

[niicholai]

After testing, I can confirm 3 things:

1. It is correct. The file is indeed not in the specified location, because the temporary folder for the extension is never created.
2. It does not appear to be version specific. I have tried with 0.10.0 Preview 1, 0.9.0, and 0.8.2 so far.
3. Running CMD with admin privileges seems to change nothing.

---

Client Info:
│ About Gemini CLI
│
│ CLI Version 0.8.2
│ Git Commit 9b2d4c6
│ Model gemini-2.5-pro
│ Sandbox no sandbox
│ OS win32
│ Auth Method OAuth

---

A key point in the directory path kept bothering me so I looked into it. My username is not NIICHO~1, yet my error states:

"Configuration file not found at C:\Users\NIICHO~1\AppData\Local\Temp\gemini-extensionWRyHQu\gemini-extension.json"

Now, while File Explorer seems to understand what that means and gets me to the right place, it stood out enough for me to bring it up. After researching I now understand that is apparently the Short Filename or SFN.

@Med-Al667 can you confirm if your error also uses the SFN with a tilde key instead of your full username?

---

I am going to do further testing and see if I can narrow down the exact issue. I will also try the workaround listed by @swissspidy and see how that goes.

---

EDIT: UPDATE

Alright, so here is what I have tested since I posted earlier:

• echo %TEMP% and echo %TMP% outputs exactly what Gemini was working with. So SFN shouldn't matter.
• node -p "require('os').tmpdir()" also output the same, so definitely not a SFN issue.
• Oddly enough, mkdir "%TEMP%\test_dir_125" rd "%TEMP%\test_dir_125" gave strange results. I did it three times for 123, 124, and 125. All three of which I watched it take my input, make the folder, then tell me the folder already exists and errored out. So it worked, but still gave an error as if it didn't.
• I ran icacls "%USERPROFILE%\AppData\Local" and that worked fine, processed one file and had no failures.
• Ran git --version where git and that was fine with git version 2.45.1.windows.1.
• Did a manual test with git clone https://github.com/github/github-mcp-server.git manual_clone_test which created the folder and pulled all of the files with no errors.

Finally, I ran the command @swissspidy suggested in Gemini CLI and it worked.

---

Upon further digging I believe I found the culprit.

swissspidy stated:
"Gemini CLI downloads the latest release of a repository"

Assuming swissspidy actually meant release, and not commit, then we found the problem. The manifest was added to the repo two days ago on October 17th with a commit tag of 84ae009. The latest release v0.18.0, tagged f9343e6, was added on October 10th and nowhere in it is the manifest available.

So if Gemini CLI pulls from releases, then the issue is it's trying to pull from releases which do not have the manifest in them, rather than the main branches latest commit which does.

[thekoma]

@swissspidy You are right. For example the repository of context7 has as latest release v1.0.21 which does not contain the extension file gemini-extension.json which has been committed in upstash/context7@be0bbe2 which happened 10 days after the last release.
The fix in my case is also:
gemini -d extensions -d install https://github.com/upstash/context7 --ref=master

Maybe the error could be more explicative telling something on the lines of:

Pulling release $release.
Configuration file not found in the release $release. If the configuration file is in a specific branch use --ref to force a pointer.

[jackwotherspoon]

CC @chrstnb on this one as it is extension related.