Custom nuget-feed no longer used, breaking package updates

TL;DR

Issue dependabot/dependabot-core#11525 (closed, 44 comments): ### Is there an existing issue for this? - [x] I have searched the existing issues ### Package ecosystem nuget ### Package manager version No response ### Language version No response ### Manifest location and content before the Dependabot update Our repos have multiple csproj files (under various subfolders like src/ and test/) and Directory.Build.props at the root ### dependabot.

Steps

1. If Dependabot ignores your custom NuGet feed and falls back to nuget.org, check the casing of your NuGet config filename. NuGet only recognizes exactly 'nuget.config', 'NuGet.config', or 'NuGet.Config'; variants like 'Nuget.config' are silently not found, and NuGet falls back to the default api.nuget.org feed. Rename the file to one of the three allowed casings. (Separately, NU1507 warnings can be suppressed with a NoWarn entry; the updater-side fix went out via dependabot-core PR #11718.)

When to use

You are seeing this: If Dependabot ignores your custom NuGet feed and falls back to nuget.org, check the casing of your NuGet config filename. Use this skill when you run into "Custom nuget-feed no longer used, breaking package updates".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

In the GitHub issue gh:dependabot/dependabot-core#11525 (https://github.com/dependabot/dependabot-core/issues/11525), the problem reported was: Issue dependabot/dependabot-core#11525 (closed, 44 comments): ### Is there an existing issue for this? - [x] I have searched the existing issues ### Package ecosystem nuget ### Package manager version No response ### Language version No response ### Manifest location and content before the Dependabot update Our repos have multiple csproj files (under various subfolders like src/ and test/) and Directory.Build.props at the root ### dependabot. The verified resolution was: If Dependabot ignores your custom NuGet feed and falls back to nuget.org, check the casing of your NuGet config filename. NuGet only recognizes exactly 'nuget.config', 'NuGet.config', or 'NuGet.Config'; variants like 'Nuget.config' are silently not found, and NuGet falls back to the default api.nuget.org feed. Rename the file to one of the three allowed casings. (Separately, NU1507 warnings can be suppressed with a NoWarn entry; the updater-side fix went out via dependabot-core PR #11718.)