How do I prevent nuget:NU1101 in CI?

Commit a repo-scoped `NuGet.Config` with sources and mapping. Validate restore on clean machines and agents instead of relying on warm caches.

How can I manually validate nuget:NU1101?

Re-run the failing command and confirm the original code/message is gone. Confirm expected artifacts or outputs exist (packages restored, build/publish succeeds).

NU1101: Unable to find package in source

Fix it fast

Most likely: The package ID is not visible in any enabled source because the feed is wrong, the package name is wrong, credentials failed, or package source mapping excludes the right feed.

1. Confirm this is your error

error NU1101: Unable to find package MyCompany.Internal.Package. No packages exist with this id in source(s): MyPrivateFeed

2. Check the cause

dotnet nuget list source
dotnet restore -v normal
grep -n "packageSourceMapping\|packageSources\|PackageReference" NuGet.Config *.csproj

3. Apply the safe fix

# Fix NuGet.Config so the feed that contains the package is enabled for this repo.
dotnet nuget add source <feed-url> --name <source-name>

# After fixing sources/auth/mapping, restore from a clean view of metadata.
dotnet nuget locals http-cache --clear
dotnet restore

4. Verify it works

dotnet restore
dotnet list package

Don't use unsafe shortcuts

Do not rename the package reference until you confirm the exact package ID in the intended feed.
Do not rely on a warm local cache, test restore on a clean machine or CI agent.
Do not add broad public sources when the missing package should come from a private feed.

What NuGet Could Not Find

NuGet could not find the requested package ID in any enabled source, which usually means the wrong feed, mapping, name, or credentials.

Validation

Re-run the failing command and confirm the original code/message is gone, and confirm expected artifacts or outputs exist (packages restored, build/publish succeeds).

Confirm the exact package you asked for

Confirm the package ID exists in the intended feed, check sources and mapping with dotnet nuget list source, update NuGet.Config, and fix auth (PAT or credential provider) then rerun with dotnet restore.

Why It Was Not Found

Usually this comes down to wrong package ID or wrong feed configured, private feed auth failed, so the package isn’t visible, or source mapping or policy prevents using the feed that contains the package.

Prove the Source Resolves Correctly Now

dotnet restore succeeds without NU1101, and dotnet list package shows the dependency resolved.

Mechanism

NuGet queries each enabled feed for package metadata by ID. If every feed reports no such ID, or cannot be queried, restore fails with NU1101.

Avoid Version and Source Drift

To prevent this, commit a repo-scoped NuGet.Config with sources and mapping, and validate restore on clean machines and agents instead of relying on warm caches.

Docs and source code

NU1101 message template

User-facing message template. - GitHub

  <data name="Error_NoPackageVersionsExist" xml:space="preserve">
    <value>Unable to find package {0}. No packages exist with this id in source(s): {1}</value>
  </data>
  <data name="Error_NoPackageVersionsExistInRange" xml:space="preserve">