diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 8a7267c..a7ae755 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -45,16 +45,44 @@ build_windows:
         }
 
         # Configure private NuGet source from GitLab Packages using CI_JOB_TOKEN
+        # Fallback to repository variables NUGET_USERNAME/NUGET_PASSWORD for shared runners
         $nugetUrl = 'https://gitlab.com/api/v4/projects/79509532/packages/nuget/index.json'
+        $authMode = $null
         if ($env:CI_JOB_TOKEN) {
           Write-Host 'Configuring private NuGet source Nuget-GitLab-AIFotoONLUS using CI_JOB_TOKEN...'
           try { & $dotnetExe nuget remove source Nuget-GitLab-AIFotoONLUS } catch {}
           & $dotnetExe nuget add source $nugetUrl --name Nuget-GitLab-AIFotoONLUS --username gitlab-ci-token --password $env:CI_JOB_TOKEN --store-password-in-clear-text
+          $authMode = 'JobToken'
+        } elseif ($env:NUGET_USERNAME -and $env:NUGET_PASSWORD) {
+          Write-Host 'Configuring private NuGet source Nuget-GitLab-AIFotoONLUS using NUGET_USERNAME/NUGET_PASSWORD...'
+          try { & $dotnetExe nuget remove source Nuget-GitLab-AIFotoONLUS } catch {}
+          & $dotnetExe nuget add source $nugetUrl --name Nuget-GitLab-AIFotoONLUS --username $env:NUGET_USERNAME --password $env:NUGET_PASSWORD --store-password-in-clear-text
+          $authMode = 'UserCreds'
         } else {
-          Write-Host 'CI_JOB_TOKEN not available; skipping private NuGet source configuration.'
+          Write-Host 'No credentials available; skipping private NuGet source configuration.'
         }
 
         & $dotnetExe --info
+        # Diagnostic: verify GitLab NuGet feed and package visibility using configured auth
+        if ($authMode) {
+          Write-Host 'Checking GitLab NuGet feed index and project packages for AIFotoONLUS.Core using auth mode:' $authMode
+          try {
+            if ($authMode -eq 'JobToken') {
+              $headers = @{ 'JOB-TOKEN' = $env:CI_JOB_TOKEN }
+            } else {
+              $pair = "$env:NUGET_USERNAME:$env:NUGET_PASSWORD"
+              $b64 = [Convert]::ToBase64String([Text.Encoding]::ASCII.GetBytes($pair))
+              $headers = @{ Authorization = "Basic $b64" }
+            }
+            Invoke-RestMethod -Uri $nugetUrl -Headers $headers -Method Get | ConvertTo-Json | Write-Host
+          } catch { Write-Host "Failed to fetch feed index: $_" }
+          try {
+            $pkgApi = "https://gitlab.com/api/v4/projects/79509532/packages?package_name=AIFotoONLUS.Core"
+            Invoke-RestMethod -Uri $pkgApi -Headers $headers -Method Get | ConvertTo-Json | Write-Host
+          } catch { Write-Host "Failed to query project packages API: $_" }
+        } else {
+          Write-Host 'Skipping feed diagnostics because no auth configured.'
+        }
         & $dotnetExe restore
         & $dotnetExe build "imagecatalog\ImageCatalog 2.csproj" -c $env:BUILD_CONFIG -v minimal
       }
@@ -88,13 +116,18 @@ publish_release:
         Write-Host "Published to $(pwd)\\publish"
 
         # Configure private NuGet source from GitLab Packages using CI_JOB_TOKEN
+        # Fallback to repository variables NUGET_USERNAME/NUGET_PASSWORD for shared runners
         $nugetUrl = 'https://gitlab.com/api/v4/projects/79509532/packages/nuget/index.json'
         if ($env:CI_JOB_TOKEN) {
           Write-Host 'Configuring private NuGet source Nuget-GitLab-AIFotoONLUS using CI_JOB_TOKEN...'
           try { & $dotnetExe nuget remove source Nuget-GitLab-AIFotoONLUS } catch {}
           & $dotnetExe nuget add source $nugetUrl --name Nuget-GitLab-AIFotoONLUS --username gitlab-ci-token --password $env:CI_JOB_TOKEN --store-password-in-clear-text
+        } elseif ($env:NUGET_USERNAME -and $env:NUGET_PASSWORD) {
+          Write-Host 'Configuring private NuGet source Nuget-GitLab-AIFotoONLUS using NUGET_USERNAME/NUGET_PASSWORD...'
+          try { & $dotnetExe nuget remove source Nuget-GitLab-AIFotoONLUS } catch {}
+          & $dotnetExe nuget add source $nugetUrl --name Nuget-GitLab-AIFotoONLUS --username $env:NUGET_USERNAME --password $env:NUGET_PASSWORD --store-password-in-clear-text
         } else {
-          Write-Host 'CI_JOB_TOKEN not available; skipping private NuGet source configuration.'
+          Write-Host 'No credentials available; skipping private NuGet source configuration.'
         }
 
         # Find first file in publish folder