PowerShell
diff --git a/‎src/System.Management.Automation/engine/CommandCompletion/CompletionCompleters.cs
Lines changed: 9 additions & 12 deletions b/‎src/System.Management.Automation/engine/CommandCompletion/CompletionCompleters.cs
Lines changed: 9 additions & 12 deletions
diff --git a/‎test/powershell/Host/TabCompletion/TabCompletion.Tests.ps1
Lines changed: 5 additions & 0 deletions b/‎test/powershell/Host/TabCompletion/TabCompletion.Tests.ps1
Lines changed: 5 additions & 0 deletions
@@ -4629,22 +4629,19 @@ private static List<CompletionResult> GetFileSystemProviderResults(
                 string basePath;
                 if (!relativePaths)
                 {
-                    string providerName = $"{provider.ModuleName}\\{provider.Name}::";
-                    if (pathInfo.Path.StartsWith(providerName, StringComparison.OrdinalIgnoreCase))
+                    if (pathInfo.Drive is null)
                     {
-                        basePath = pathInfo.Path.Substring(providerName.Length);
+                        basePath = dirInfo.FullName;
                     }
                     else
                     {
-                        providerName = $"{provider.Name}::";
-                        if (pathInfo.Path.StartsWith(providerName, StringComparison.OrdinalIgnoreCase))
-                        {
-                            basePath = pathInfo.Path.Substring(providerName.Length);
-                        }
-                        else
-                        {
-                            basePath = pathInfo.Path;
-                        }
+                        int stringStartIndex = pathInfo.Drive.Root.EndsWith(provider.ItemSeparator) && pathInfo.Drive.Root.Length > 1
+                            ? pathInfo.Drive.Root.Length - 1
+                            : pathInfo.Drive.Root.Length;
+
+                        basePath = pathInfo.Drive.VolumeSeparatedByColon
+                            ? string.Concat(pathInfo.Drive.Name, ":", dirInfo.FullName.AsSpan(stringStartIndex))
+                            : string.Concat(pathInfo.Drive.Name, dirInfo.FullName.AsSpan(stringStartIndex));
                     }
 
                     basePath = basePath.EndsWith(provider.ItemSeparator)
 
@@ -1276,6 +1276,11 @@ class InheritedClassTest : System.Attribute
         }
     }
 
+    It 'Should correct slashes in UNC path completion' -Skip:(!$IsWindows) {
+        $Res = TabExpansion2 -inputScript 'Get-ChildItem //localhost/c$/Windows'
+        $Res.CompletionMatches[0].CompletionText | Should -Be "'\\localhost\c$\Windows'"
+    }
+
     It 'Should keep custom drive names when completing file paths' {
         $TempDriveName = "asdf"
         $null = New-PSDrive -Name $TempDriveName -PSProvider FileSystem -Root $HOME
Original file line number	Diff line number	Diff line change
`@@ -1276,6 +1276,11 @@ class InheritedClassTest : System.Attribute`
`1276`	`1276`	`}`
`1277`	`1277`	`}`
`1278`	`1278`
	`1279`	`+ It 'Should correct slashes in UNC path completion' -Skip:(!$IsWindows) {`
	`1280`	`+ $Res = TabExpansion2 -inputScript 'Get-ChildItem //localhost/c$/Windows'`
	`1281`	`+ $Res.CompletionMatches[0].CompletionText \| Should -Be "'\\localhost\c$\Windows'"`
	`1282`	`+ }`
	`1283`	`+`
`1279`	`1284`	`It 'Should keep custom drive names when completing file paths' {`
`1280`	`1285`	`$TempDriveName = "asdf"`
`1281`	`1286`	`$null = New-PSDrive -Name $TempDriveName -PSProvider FileSystem -Root $HOME`