diff --git a/Controllers/ShellController.cs b/Controllers/ShellController.cs
index dfb267d..a5f00e1 100644
--- a/Controllers/ShellController.cs
+++ b/Controllers/ShellController.cs
@@ -288,8 +288,26 @@ namespace RevitHttpControl.Controllers
             }
             catch (InvalidOperationException ex)
             {
+                if (ex.Message.Contains(ErrorMessages.NO_DOCUMENT_OPEN_MSG))
+                {
+                    return this.CreateErrorResponse(
+                        ErrorCodes.NO_DOCUMENT_OPEN,
+                        ex.Message,
+                        HttpStatusCode.BadRequest
+                    );
+                }
+
+                if (ex.Message.Contains("创建备份失败"))
+                {
+                    return this.CreateErrorResponse(
+                        ErrorCodes.FILE_WRITE_PERMISSION_DENIED,
+                        ex.Message,
+                        HttpStatusCode.Forbidden
+                    );
+                }
+
                 return this.CreateErrorResponse(
-                    ErrorCodes.NO_DOCUMENT_OPEN,
+                    ErrorCodes.REVIT_COMMAND_FAILED,
                     ex.Message,
                     HttpStatusCode.BadRequest
                 );
diff --git a/Services/ShellOptimizer.cs b/Services/ShellOptimizer.cs
index 2fa12f6..f8cc17b 100644
--- a/Services/ShellOptimizer.cs
+++ b/Services/ShellOptimizer.cs
@@ -274,10 +274,22 @@ namespace RevitHttpControl.Services
                 if (worksetId != WorksetId.InvalidWorksetId)
                 {
                     var doc = element.Document;
-                    var worksetTable = doc.GetWorksetTable();
-                    var workset = worksetTable.GetWorkset(worksetId);
-                    if (workset.IsOpen && workset.Owner != doc.Application.Username)
-                        return false;
+                    // 仅对工作共享文档执行“他人占用”校验，避免本地/样例文件误判。
+                    if (doc.IsWorkshared)
+                    {
+                        var worksetTable = doc.GetWorksetTable();
+                        var workset = worksetTable.GetWorkset(worksetId);
+                        var owner = workset?.Owner;
+                        var currentUser = doc.Application?.Username;
+
+                        if (workset != null &&
+                            workset.IsOpen &&
+                            !string.IsNullOrWhiteSpace(owner) &&
+                            !string.Equals(owner, currentUser, StringComparison.OrdinalIgnoreCase))
+                        {
+                            return false;
+                        }
+                    }
                 }
 
                 // 检查是否有依赖关系（如主体构件）
@@ -341,18 +353,38 @@ namespace RevitHttpControl.Services
                     throw new InvalidOperationException("文档必须先保存才能创建备份");
                 }
 
-                var directory = Path.GetDirectoryName(originalPath);
                 var fileName = Path.GetFileNameWithoutExtension(originalPath);
                 var extension = Path.GetExtension(originalPath);
                 var timestamp = DateTime.Now.ToString("yyyyMMdd_HHmmss");
-                
                 var backupFileName = $"{fileName}_backup_{timestamp}{extension}";
-                var backupPath = Path.Combine(directory, backupFileName);
 
-                // 复制文件
-                File.Copy(originalPath, backupPath, false);
-                
-                return backupPath;
+                // 先尝试写入原目录；若无权限则回退到用户本地目录。
+                var sourceDirectory = Path.GetDirectoryName(originalPath);
+                if (!string.IsNullOrWhiteSpace(sourceDirectory))
+                {
+                    var backupPathInSource = Path.Combine(sourceDirectory, backupFileName);
+                    try
+                    {
+                        File.Copy(originalPath, backupPathInSource, false);
+                        return backupPathInSource;
+                    }
+                    catch (UnauthorizedAccessException)
+                    {
+                        // Ignore and fallback.
+                    }
+                    catch (IOException ex) when (File.Exists(backupPathInSource))
+                    {
+                        throw new InvalidOperationException($"备份文件已存在: {backupPathInSource}", ex);
+                    }
+                }
+
+                var localAppData = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
+                var fallbackDirectory = Path.Combine(localAppData, "RevitHttpControl", "Backups");
+                Directory.CreateDirectory(fallbackDirectory);
+
+                var backupPathInFallback = Path.Combine(fallbackDirectory, backupFileName);
+                File.Copy(originalPath, backupPathInFallback, false);
+                return backupPathInFallback;
             }
             catch (Exception ex)
             {
@@ -367,9 +399,20 @@ namespace RevitHttpControl.Services
         {
             try
             {
-                if (doc.IsModified)
+                if (!doc.IsModified)
+                {
+                    return;
+                }
+
+                try
                 {
                     doc.Save();
+                    return;
+                }
+                catch (Exception ex) when (IsReadOnlySaveError(ex))
+                {
+                    SaveDocumentAsWritableCopy(doc);
+                    return;
                 }
             }
             catch (Exception ex)
@@ -378,6 +421,38 @@ namespace RevitHttpControl.Services
             }
         }
 
+        private bool IsReadOnlySaveError(Exception ex)
+        {
+            if (ex == null) return false;
+            var message = ex.Message ?? string.Empty;
+            return message.IndexOf("read-only", StringComparison.OrdinalIgnoreCase) >= 0 ||
+                   message.IndexOf("只读", StringComparison.OrdinalIgnoreCase) >= 0;
+        }
+
+        private void SaveDocumentAsWritableCopy(Document doc)
+        {
+            var originalPath = doc.PathName;
+            if (string.IsNullOrWhiteSpace(originalPath))
+                throw new InvalidOperationException("文档为只读且无法获取原始路径，不能自动另存为");
+
+            var fileName = Path.GetFileNameWithoutExtension(originalPath);
+            var extension = Path.GetExtension(originalPath);
+            var timestamp = DateTime.Now.ToString("yyyyMMdd_HHmmss");
+
+            var localAppData = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
+            var outputDirectory = Path.Combine(localAppData, "RevitHttpControl", "Optimized");
+            Directory.CreateDirectory(outputDirectory);
+
+            var outputPath = Path.Combine(outputDirectory, $"{fileName}_optimized_{timestamp}{extension}");
+            var saveAsOptions = new SaveAsOptions
+            {
+                OverwriteExistingFile = false,
+                Compact = true
+            };
+
+            doc.SaveAs(outputPath, saveAsOptions);
+        }
+
         /// <summary>
         /// 获取文档文件大小
         /// </summary>