diff --git a/MCPForUnity/Editor/Clients/Configurators/RiderConfigurator.cs b/MCPForUnity/Editor/Clients/Configurators/RiderConfigurator.cs
index 5db02acaf..ea1087ea4 100644
--- a/MCPForUnity/Editor/Clients/Configurators/RiderConfigurator.cs
+++ b/MCPForUnity/Editor/Clients/Configurators/RiderConfigurator.cs
@@ -10,9 +10,10 @@ public class RiderConfigurator : JsonFileMcpConfigurator
         public RiderConfigurator() : base(new McpClient
         {
             name = "Rider GitHub Copilot",
-            windowsConfigPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "JetBrains", "Rider", "mcp.json"),
-            macConfigPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), "Library", "Application Support", "JetBrains", "Rider", "mcp.json"),
-            linuxConfigPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), ".config", "JetBrains", "Rider", "mcp.json"),
+            // Rider GitHub Copilot uses github-copilot/intellij path under appropriate per-OS data directories
+            windowsConfigPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), "github-copilot", "intellij", "mcp.json"),
+            macConfigPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), "Library", "Application Support", "github-copilot", "intellij", "mcp.json"),
+            linuxConfigPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), ".local", "share", "github-copilot", "intellij", "mcp.json"),
             IsVsCodeLayout = true
         })
         { }
diff --git a/MCPForUnity/Editor/Clients/McpClientConfiguratorBase.cs b/MCPForUnity/Editor/Clients/McpClientConfiguratorBase.cs
index 897e7dfd8..5a0bb0317 100644
--- a/MCPForUnity/Editor/Clients/McpClientConfiguratorBase.cs
+++ b/MCPForUnity/Editor/Clients/McpClientConfiguratorBase.cs
@@ -540,9 +540,8 @@ private void RegisterWithCapturedValues(
             }
             else
             {
-                // Note: --reinstall is not supported by uvx, use --no-cache --refresh instead
-                string devFlags = shouldForceRefresh ? "--no-cache --refresh " : string.Empty;
-                args = $"mcp add --transport stdio UnityMCP -- \"{uvxPath}\" {devFlags}--from \"{gitUrl}\" {packageName}";
+                string packageArgs = BuildClaudeUvxArgs(uvxPath, gitUrl, packageName, shouldForceRefresh);
+                args = $"mcp add --transport stdio UnityMCP -- {packageArgs}";
             }
 
             // Remove any existing registrations - handle both "UnityMCP" and "unityMCP" (legacy)
@@ -599,10 +598,9 @@ private void Register()
             else
             {
                 var (uvxPath, gitUrl, packageName) = AssetPathUtility.GetUvxCommandParts();
-                // Use central helper that checks both DevModeForceServerRefresh AND local path detection.
-                // Note: --reinstall is not supported by uvx, use --no-cache --refresh instead
-                string devFlags = AssetPathUtility.ShouldForceUvxRefresh() ? "--no-cache --refresh " : string.Empty;
-                args = $"mcp add --transport stdio UnityMCP -- \"{uvxPath}\" {devFlags}--from \"{gitUrl}\" {packageName}";
+                bool shouldForceRefresh = AssetPathUtility.ShouldForceUvxRefresh();
+                string packageArgs = BuildClaudeUvxArgs(uvxPath, gitUrl, packageName, shouldForceRefresh);
+                args = $"mcp add --transport stdio UnityMCP -- {packageArgs}";
             }
 
             string projectDir = Path.GetDirectoryName(Application.dataPath);
@@ -698,13 +696,12 @@ public override string GetManualSnippet()
                 return "# Error: Configuration not available - check paths in Advanced Settings";
             }
 
-            string packageSource = AssetPathUtility.GetMcpServerPackageSource();
-            // Use central helper that checks both DevModeForceServerRefresh AND local path detection.
-            // Note: --reinstall is not supported by uvx, use --no-cache --refresh instead
-            string devFlags = AssetPathUtility.ShouldForceUvxRefresh() ? "--no-cache --refresh " : string.Empty;
+            var (_, gitUrl, packageName) = AssetPathUtility.GetUvxCommandParts();
+            bool shouldForceRefresh = AssetPathUtility.ShouldForceUvxRefresh();
+            string packageArgs = BuildClaudeUvxArgs(uvxPath, gitUrl, packageName, shouldForceRefresh);
 
             return "# Register the MCP server with Claude Code:\n" +
-                   $"claude mcp add --transport stdio UnityMCP -- \"{uvxPath}\" {devFlags}--from \"{packageSource}\" mcp-for-unity\n\n" +
+                   $"claude mcp add --transport stdio UnityMCP -- {packageArgs}\n\n" +
                    "# Unregister the MCP server:\n" +
                    "claude mcp remove UnityMCP\n\n" +
                    "# List registered servers:\n" +
@@ -763,5 +760,24 @@ private static string ExtractPackageSourceFromCliOutput(string cliOutput)
 
             return null;
         }
+
+        /// <summary>
+        /// Builds the correct uvx package arguments for Claude CLI mcp add command.
+        /// IMPORTANT: We always need --from because the PyPI package name (mcpforunityserver)
+        /// differs from the executable name (mcp-for-unity). The uvx command format is:
+        /// uvx --from PACKAGE_SOURCE EXECUTABLE_NAME --transport stdio
+        /// Example: uvx --from mcpforunityserver==9.0.8 mcp-for-unity --transport stdio
+        /// </summary>
+        private static string BuildClaudeUvxArgs(string uvxPath, string fromUrl, string packageName, bool shouldForceRefresh)
+        {
+            // Dev flags
+            string devFlags = shouldForceRefresh ? "--no-cache --refresh " : string.Empty;
+
+            // Always use --from because package name != executable name
+            // Example: uvx --from mcpforunityserver==9.0.8 mcp-for-unity
+            string packageArgs = $"\"{uvxPath}\" {devFlags}--from \"{fromUrl}\" {packageName}";
+
+            return packageArgs;
+        }
     }
 }
diff --git a/MCPForUnity/Editor/Helpers/AssetPathUtility.cs b/MCPForUnity/Editor/Helpers/AssetPathUtility.cs
index b65cf21ea..1669bf52c 100644
--- a/MCPForUnity/Editor/Helpers/AssetPathUtility.cs
+++ b/MCPForUnity/Editor/Helpers/AssetPathUtility.cs
@@ -153,7 +153,7 @@ public static JObject GetPackageJson()
         /// Checks for EditorPrefs override first (supports git URLs, file:// paths, etc.),
         /// then falls back to PyPI package reference.
         /// </summary>
-        /// <returns>Package source string for uvx --from argument</returns>
+        /// <returns>Package source string for uvx --from argument (guaranteed non-null)</returns>
         public static string GetMcpServerPackageSource()
         {
             // Check for override first (supports git URLs, file:// paths, local paths)
@@ -182,13 +182,25 @@ public static string GetMcpServerPackageSource()
         public static string GetMcpServerGitUrl() => GetMcpServerPackageSource();
 
         /// <summary>
-        /// Gets structured uvx command parts for different client configurations
+        /// Gets structured uvx command parts for different client configurations.
         /// </summary>
-        /// <returns>Tuple containing (uvxPath, fromUrl, packageName)</returns>
+        /// <returns>Tuple containing (uvxPath, fromUrl, packageName) - fromUrl is guaranteed non-null</returns>
+        /// <exception cref="InvalidOperationException">Thrown when uvx path cannot be determined</exception>
         public static (string uvxPath, string fromUrl, string packageName) GetUvxCommandParts()
         {
             string uvxPath = MCPServiceLocator.Paths.GetUvxPath();
+            if (string.IsNullOrEmpty(uvxPath))
+            {
+                throw new InvalidOperationException("Cannot determine uvx path. Please ensure uv is installed and configured.");
+            }
+
             string fromUrl = GetMcpServerPackageSource();
+            // GetMcpServerPackageSource() guarantees non-null, but validate for defense in depth
+            if (string.IsNullOrEmpty(fromUrl))
+            {
+                throw new InvalidOperationException("Cannot determine MCP server package source. This should never happen - please report this bug.");
+            }
+
             string packageName = "mcp-for-unity";
 
             return (uvxPath, fromUrl, packageName);
diff --git a/MCPForUnity/Editor/Helpers/CodexConfigHelper.cs b/MCPForUnity/Editor/Helpers/CodexConfigHelper.cs
index 10f2bacb3..32dae58d0 100644
--- a/MCPForUnity/Editor/Helpers/CodexConfigHelper.cs
+++ b/MCPForUnity/Editor/Helpers/CodexConfigHelper.cs
@@ -27,6 +27,33 @@ private static void AddDevModeArgs(TomlArray args)
             args.Add(new TomlString { Value = "--refresh" });
         }
 
+        /// <summary>
+        /// Adds package arguments to the TOML array.
+        /// IMPORTANT: We always need --from because the PyPI package name (mcpforunityserver)
+        /// differs from the executable name (mcp-for-unity). The uvx command format is:
+        /// uvx --from PACKAGE_SOURCE EXECUTABLE_NAME --transport stdio
+        /// Example: uvx --from mcpforunityserver==9.0.8 mcp-for-unity --transport stdio
+        /// </summary>
+        /// <param name="args">The TOML array to add arguments to</param>
+        /// <param name="fromUrl">Package source for --from argument (guaranteed non-null from GetUvxCommandParts)</param>
+        /// <param name="packageName">Executable name to run</param>
+        private static void AddPackageArgs(TomlArray args, string fromUrl, string packageName)
+        {
+            if (args == null) return;
+
+            // fromUrl is guaranteed non-null by GetUvxCommandParts(), but validate for defense in depth
+            if (string.IsNullOrEmpty(fromUrl))
+            {
+                throw new InvalidOperationException("Package source (--from argument) cannot be empty. This should never happen - please report this bug.");
+            }
+
+            // Always use --from because package name != executable name
+            args.Add(new TomlString { Value = "--from" });
+            args.Add(new TomlString { Value = fromUrl });
+
+            args.Add(new TomlString { Value = packageName });
+        }
+
         public static string BuildCodexServerBlock(string uvPath)
         {
             var table = new TomlTable();
@@ -54,12 +81,7 @@ public static string BuildCodexServerBlock(string uvPath)
 
                 var args = new TomlArray();
                 AddDevModeArgs(args);
-                if (!string.IsNullOrEmpty(fromUrl))
-                {
-                    args.Add(new TomlString { Value = "--from" });
-                    args.Add(new TomlString { Value = fromUrl });
-                }
-                args.Add(new TomlString { Value = packageName });
+                AddPackageArgs(args, fromUrl, packageName);
                 args.Add(new TomlString { Value = "--transport" });
                 args.Add(new TomlString { Value = "stdio" });
 
@@ -203,12 +225,7 @@ private static TomlTable CreateUnityMcpTable(string uvPath)
 
                 var argsArray = new TomlArray();
                 AddDevModeArgs(argsArray);
-                if (!string.IsNullOrEmpty(fromUrl))
-                {
-                    argsArray.Add(new TomlString { Value = "--from" });
-                    argsArray.Add(new TomlString { Value = fromUrl });
-                }
-                argsArray.Add(new TomlString { Value = packageName });
+                AddPackageArgs(argsArray, fromUrl, packageName);
                 argsArray.Add(new TomlString { Value = "--transport" });
                 argsArray.Add(new TomlString { Value = "stdio" });
                 unityMCP["args"] = argsArray;
diff --git a/MCPForUnity/Editor/Helpers/ConfigJsonBuilder.cs b/MCPForUnity/Editor/Helpers/ConfigJsonBuilder.cs
index dd00d73d0..bc21f878c 100644
--- a/MCPForUnity/Editor/Helpers/ConfigJsonBuilder.cs
+++ b/MCPForUnity/Editor/Helpers/ConfigJsonBuilder.cs
@@ -161,7 +161,6 @@ private static IList<string> BuildUvxArgs(string fromUrl, string packageName)
             // Dev mode: force a fresh install/resolution (avoids stale cached builds while iterating).
             // `--no-cache` avoids reading from cache; `--refresh` ensures metadata is revalidated.
             // Note: --reinstall is not supported by uvx and will cause a warning.
-            // Keep ordering consistent with other uvx builders: dev flags first, then --from <url>, then package name.
             var args = new List<string>();
 
             // Use central helper that checks both DevModeForceServerRefresh AND local path detection.
@@ -170,13 +169,21 @@ private static IList<string> BuildUvxArgs(string fromUrl, string packageName)
                 args.Add("--no-cache");
                 args.Add("--refresh");
             }
-            if (!string.IsNullOrEmpty(fromUrl))
+
+            // IMPORTANT: We always need --from because the PyPI package name (mcpforunityserver)
+            // differs from the executable name (mcp-for-unity). The uvx command format is:
+            // uvx --from PACKAGE_SOURCE EXECUTABLE_NAME --transport stdio
+            // Example: uvx --from mcpforunityserver==9.0.8 mcp-for-unity --transport stdio
+            // fromUrl is guaranteed non-null by GetUvxCommandParts(), but validate for defense in depth
+            if (string.IsNullOrEmpty(fromUrl))
             {
-                args.Add("--from");
-                args.Add(fromUrl);
+                throw new InvalidOperationException("Package source (--from argument) cannot be empty. This should never happen - please report this bug.");
             }
-            args.Add(packageName);
 
+            args.Add("--from");
+            args.Add(fromUrl);
+
+            args.Add(packageName);
             args.Add("--transport");
             args.Add("stdio");