diff --git a/.github/copilot-instructions.md b/.github/copilot-instructions.md
new file mode 100644
index 0000000000..19be10e2fa
--- /dev/null
+++ b/.github/copilot-instructions.md
@@ -0,0 +1,30 @@
+This is a .NET based repository that contains the VSTest test platform. Please follow these guidelines when contributing:
+
+## Code Standards
+
+You MUST follow all code-formatting and naming conventions defined in [`.editorconfig`](../.editorconfig).
+
+In addition to the rules enforced by `.editorconfig`, you SHOULD:
+
+- Favor style and conventions that are consistent with the existing codebase.
+- Prefer file-scoped namespace declarations and single-line using directives.
+- Ensure that the final return statement of a method is on its own line.
+- Use pattern matching and switch expressions wherever possible.
+- Use `nameof` instead of string literals when referring to member names.
+- Always use `is null` or `is not null` instead of `== null` or `!= null`.
+- Trust the C# null annotations and don't add null checks when the type system says a value cannot be null.
+- Prefer `?.` if applicable (e.g. `scope?.Dispose()`).
+- Use `ObjectDisposedException.ThrowIf` where applicable.
+- Respect StyleCop.Analyzers rules, in particular:
+  - SA1028: Code must not contain trailing whitespace
+  - SA1316: Tuple element names should use correct casing
+  - SA1518: File is required to end with a single newline character
+
+You MUST minimize adding public API surface area but any newly added public API MUST be declared in the related `PublicAPI.Unshipped.txt` file.
+
+## Localization Guidelines
+
+Anytime you add a new localization resource, you MUST:
+- Add a corresponding entry in the localization resource file.
+- Add an entry in all `*.xlf` files related to the modified `.resx` file.
+- Do not modify existing entries in '*.xlf' files unless you are also modifying the corresponding `.resx` file.
diff --git a/src/vstest.console/Internal/FilePatternParser.cs b/src/vstest.console/Internal/FilePatternParser.cs
index 804739ca7e..9dfcd08678 100644
--- a/src/vstest.console/Internal/FilePatternParser.cs
+++ b/src/vstest.console/Internal/FilePatternParser.cs
@@ -5,6 +5,7 @@
 using System.Collections.Generic;
 using System.Globalization;
 using System.IO;
+using System.Runtime.InteropServices;
 
 using Microsoft.Extensions.FileSystemGlobbing;
 using Microsoft.Extensions.FileSystemGlobbing.Abstractions;
@@ -96,7 +97,24 @@ private Tuple<string, string> SplitFilePatternOnWildCard(string filePattern)
     {
         // Split the pattern based on first wild card character found.
         var splitOnWildCardIndex = filePattern.IndexOfAny(_wildCardCharacters);
-        var directorySeparatorIndex = filePattern.Substring(0, splitOnWildCardIndex).LastIndexOf(Path.DirectorySeparatorChar);
+        var pathBeforeWildCard = filePattern.Substring(0, splitOnWildCardIndex);
+
+        // Find the last directory separator before the wildcard
+        // On Windows, we need to check both \ and / as both are valid
+        // On Unix-like systems, only / is the directory separator
+        int directorySeparatorIndex;
+        if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+        {
+            // On Windows, check both separators and take the last one found
+            directorySeparatorIndex = Math.Max(
+                pathBeforeWildCard.LastIndexOf(Path.DirectorySeparatorChar),
+                pathBeforeWildCard.LastIndexOf(Path.AltDirectorySeparatorChar));
+        }
+        else
+        {
+            // On Unix-like systems, only use the forward slash
+            directorySeparatorIndex = pathBeforeWildCard.LastIndexOf(Path.DirectorySeparatorChar);
+        }
 
         string searchDir = filePattern.Substring(0, directorySeparatorIndex);
         string pattern = filePattern.Substring(directorySeparatorIndex + 1);
diff --git a/test/vstest.console.UnitTests/Internal/FilePatternParserTests.cs b/test/vstest.console.UnitTests/Internal/FilePatternParserTests.cs
index 571936d859..4c7e7e0f29 100644
--- a/test/vstest.console.UnitTests/Internal/FilePatternParserTests.cs
+++ b/test/vstest.console.UnitTests/Internal/FilePatternParserTests.cs
@@ -114,6 +114,61 @@ public void FilePatternParserShouldThrowCommandLineExceptionIfFileDoesNotExist()
         Assert.ThrowsException<TestSourceException>(() => _filePatternParser.GetMatchingFiles(TranslatePath(@"E:\path\to\project\tests\Blame.Tests\\abc.Tests.dll")));
     }
 
+    [TestMethod]
+    // only on windows because we don't translate the path to be valid linux / mac path
+    [OSCondition(OperatingSystems.Windows)]
+    public void FilePatternParserShouldCorrectlySplitPatternAndDirectoryWithForwardSlashes()
+    {
+        var patternMatchingResult = new PatternMatchingResult(new List<FilePatternMatch>());
+        _mockMatcherHelper.Setup(x => x.Execute(It.IsAny<DirectoryInfoWrapper>())).Returns(patternMatchingResult);
+
+        // Test with forward slashes - this should work on all platforms
+        // This specifically tests the fix for issue #14993
+        _filePatternParser.GetMatchingFiles("C:/Users/someUser/Desktop/a/c/*bc.dll");
+
+        // Assert that the pattern is parsed correctly
+        _mockMatcherHelper.Verify(x => x.AddInclude("*bc.dll"));
+        // On Windows, the path may be normalized, so we verify the key components are present
+        _mockMatcherHelper.Verify(x => x.Execute(It.Is<DirectoryInfoWrapper>(y =>
+            y.FullName.Contains("someUser") && y.FullName.Contains("Desktop") &&
+            y.FullName.Contains("a") && y.FullName.EndsWith("c"))));
+    }
+
+    [TestMethod]
+    // only on windows because we don't translate the path to be valid linux / mac path
+    [OSCondition(OperatingSystems.Windows)]
+    public void FilePatternParserShouldCorrectlySplitWithArbitraryDirectoryDepthWithForwardSlashes()
+    {
+        var patternMatchingResult = new PatternMatchingResult(new List<FilePatternMatch>());
+        _mockMatcherHelper.Setup(x => x.Execute(It.IsAny<DirectoryInfoWrapper>())).Returns(patternMatchingResult);
+
+        // Test with forward slashes and recursive patterns
+        _filePatternParser.GetMatchingFiles("C:/Users/someUser/**/c/*bc.txt");
+
+        // Assert
+        _mockMatcherHelper.Verify(x => x.AddInclude("**/c/*bc.txt"));
+        _mockMatcherHelper.Verify(x => x.Execute(It.Is<DirectoryInfoWrapper>(y =>
+            y.FullName.Contains("someUser"))));
+    }
+
+    [TestMethod]
+    // only on windows because we don't translate the path to be valid linux / mac path
+    [OSCondition(OperatingSystems.Windows)]
+    public void FilePatternParserShouldHandleForwardSlashesWithoutThrowingException()
+    {
+        var patternMatchingResult = new PatternMatchingResult(new List<FilePatternMatch>());
+        _mockMatcherHelper.Setup(x => x.Execute(It.IsAny<DirectoryInfoWrapper>())).Returns(patternMatchingResult);
+
+        // This is the specific case from the original bug report that was throwing ArgumentOutOfRangeException
+        // Before the fix: System.ArgumentOutOfRangeException: length ('-1') must be a non-negative value
+        _filePatternParser.GetMatchingFiles("C:/path/to/my/tests/*_Tests.dll");
+
+        // Assert that we successfully parse without throwing and get the expected pattern
+        _mockMatcherHelper.Verify(x => x.AddInclude("*_Tests.dll"));
+        _mockMatcherHelper.Verify(x => x.Execute(It.Is<DirectoryInfoWrapper>(y =>
+            y.FullName.Contains("path") && y.FullName.Contains("tests"))));
+    }
+
     private static string TranslatePath(string path)
     {
         // RuntimeInformation has conflict when used