Possible Regression: + in Branch Name Breaks ref in API

[wojked]

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🐛 Possible Regression: + in Branch Name Breaks ref in API

Summary

When using the GitHub REST API to retrieve file contents via the ref query parameter, there's confusion around how special characters are handled. Specifically, branch names containing characters like / and + used to work without explicit encoding, but + is now interpreted as a space ( ), resulting in 404 errors for valid branches.

---

Example

Branch name:

my-branch/with-commits.2025-03-28+0000

API request:

GET https://api.github.com/repos/<org>/<repo>/contents/path/to/file.json?ref=my-branch/with-commits.2025-03-28+0000

API response:

{
  "message": "No commit found for the ref my-branch/with-commits.2025-03-28 0000",
  "status": "404",
  "documentation_url": "https://docs.github.com/v3/repos/contents/"
}

Note that the + character in the ref is interpreted as a space, causing the branch lookup to fail — even though the branch exists.

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Timing

• ✅ Confirmed working: 18 March 2025, 13:00 GMT+1 — + in the ref was handled correctly.
• ❌ First noticed failing: around 27 March 2025

The change appears to have occurred between these dates.

Our Approach

To avoid issues caused by special character interpretation in the ref parameter, we plan to avoid using + signs in branch names altogether moving forward. We'll adopt safer alternatives (e.g. - or Z in place of +) to ensure compatibility with API behavior and URL parsing.

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Expected Behavior

We believe there may have been a change in the GitHub API’s handling of the ref parameter — previously, + could be used in branch names without explicit encoding, but now it appears to be parsed as a space unless encoded. This shift breaks existing tooling and scripts that previously worked without encoding the +.

• The behavior of ref escaping should be consistent and well-documented.
• Either restore the previous behavior or clearly document that certain characters (like +) must be percent-encoded.

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[MegaMind1212]

As you noted, the + is now being interpreted as a space, which started failing around March 27, 2025—likely due to a recent API update. Looking at the GitHub Status page, there were several incidents around March 20-21, 2025, involving service degradations, but nothing specific to API behavior. However, this timing aligns with your observation of the issue starting between March 18 and March 27.

The expected behavior, as per GitHub’s REST API docs for Git references, is that the ref in the URL should be formatted as heads/, and special characters like + should either be handled correctly or require percent-encoding (e.g., + as %2B). Historically, GitHub was more lenient, but it seems they’ve tightened the parsing logic, causing this regression.

For now, your workaround of avoiding + in branch names is a good call. To fix existing scripts, you can percent-encode the + as %2B in the API request. So your request would look like:

GET https://api.github.com/repos/<org>/<repo>/contents/path/to/file.json?ref=my-branch/with-commits.2025-03-28%2B0000

This should resolve the 404 error. I’d also recommend adding a note to your team’s branching guidelines to stick with safer characters like - or Z, as you mentioned. I’ll flag this to the GitHub team to either restore the previous behavior or update the docs to clarify that + must be encoded.

[zonque]

We have bumped into this as well, even though the + signs are properly encoded with %2b.

I created a test repository to demonstrate the regression.

Accessing README.md from the main branch works fine:

$ curl -v https://api.github.com/repos/zonque/apitest/contents/README.md\?ref\=refs%2fheads%2fmain
...
> GET /repos/zonque/apitest/contents/README.md?ref=refs%2fheads%2fmain HTTP/2
> Host: api.github.com
> User-Agent: curl/8.9.1
...
< HTTP/2 200 
...

Using the branch+test branch however does not:

$ curl -v https://api.github.com/repos/zonque/apitest/contents/README.md\?ref\=refs%2fheads%2fbranch%2btest 
...
> GET /repos/zonque/apitest/contents/README.md?ref=refs%2fheads%2fbranch%2btest HTTP/2
> Host: api.github.com
> User-Agent: curl/8.9.1
...
< HTTP/2 404 
...
{
  "message": "No commit found for the ref refs/heads/branch test",
  "documentation_url": "https://docs.github.com/v3/repos/contents/",
  "status": "404"
}

Note the space in the "message" field of the reported status.

We have dozens of repositories in our company and cannot change the branch names as build pipelines are referencing the branches all over the place. So the impact of this bug is significant for us.

[zonque]

FWIW, the regression must have happened in the last 24 hours.

[zonque]

The issue seems to be resolved now.

[queenofcorgis]

Thanks everyone who reported this, we were able to pass these reports to our team ❤️ . This was the result of a feature flag rollback and I can confirm it is resolved. If you encounter anything related to this, please let us know on this discussion.