diff --git a/src/models/Config.tsx b/src/models/Config.tsx
index 407c824..adbc5b5 100644
--- a/src/models/Config.tsx
+++ b/src/models/Config.tsx
@@ -97,29 +97,48 @@ export class Config {
    * Updates template by adding placeholders for environment params
    */
   public updateTemplateFromEnv(env: Env): void {
-    let templateObj: Record<string, string> = {};
+    // If template is empty, initialize with empty object
+    if (!this.template.content || !this.template.content.trim()) {
+      this.template = new ConfigTemplate('{}');
+    }
 
     // Try to parse existing template
+    let templateObj: Record<string, any> = {};
+    let hasExistingContent = false;
+    
     try {
       if (this.template.content.trim()) {
         templateObj = JSON.parse(this.template.content);
+        hasExistingContent = Object.keys(templateObj).length > 0;
       }
     } catch {
-      // Start fresh if invalid JSON
+      // If invalid JSON, preserve the raw content and don't modify
+      return;
     }
 
     // Add placeholders for params that don't exist yet
+    let hasChanges = false;
     for (const param of env.params) {
       if (param.name && param.name.trim()) {
-        const placeholder = `@${param.name}@`;
+        const paramName = param.name.trim();
+        const placeholder = `@${paramName}@`;
+        const templateKey = `!!! ${paramName}`;
 
+        // Check if placeholder exists anywhere in template
         if (!this.template.content.includes(placeholder)) {
-          templateObj[`!!! ${param.name}`] = placeholder;
+          // Only add if not already in templateObj
+          if (!templateObj[templateKey]) {
+            templateObj[templateKey] = placeholder;
+            hasChanges = true;
+          }
         }
       }
     }
 
-    this.template = new ConfigTemplate(JSON.stringify(templateObj, null, 4));
+    // Only update if there are actual changes
+    if (hasChanges || !hasExistingContent) {
+      this.template = new ConfigTemplate(JSON.stringify(templateObj, null, 4));
+    }
   }
 
   /**
diff --git a/src/test/ConfigUpdate.test.ts b/src/test/ConfigUpdate.test.ts
new file mode 100644
index 0000000..80a3463
--- /dev/null
+++ b/src/test/ConfigUpdate.test.ts
@@ -0,0 +1,159 @@
+import { describe, it, expect } from 'vitest';
+import { Config } from '../models/Config';
+import { Env } from '../models/Env';
+import { EnvParam } from '../models/EnvParam';
+
+describe('Config Template Update', () => {
+  it('should preserve existing template when adding new parameter', () => {
+    // Arrange: Create config with existing template
+    const config = new Config();
+    const existingTemplate = `{
+  "existingKey": "existingValue",
+  "anotherKey": 123
+}`;
+    config.setTemplate(existingTemplate);
+    
+    const env = new Env(0, 'DEFAULT', [
+      new EnvParam(1, 'host', 'localhost'),
+      new EnvParam(2, 'port', '8080')
+    ]);
+    config.setEnvs([env]);
+
+    // Act: Update template from env (simulating adding parameters)
+    config.updateTemplateFromEnv(env);
+
+    // Assert: Template should have both existing content and new placeholders
+    const templateContent = config.template.content;
+    const templateObj = JSON.parse(templateContent);
+    
+    expect(templateObj.existingKey).toBe('existingValue');
+    expect(templateObj.anotherKey).toBe(123);
+    expect(templateObj['!!! host']).toBe('@host@');
+    expect(templateObj['!!! port']).toBe('@port@');
+  });
+
+  it('should not duplicate placeholders that already exist', () => {
+    // Arrange: Create config with template that already has placeholder
+    const config = new Config();
+    const existingTemplate = `{
+  "host": "@host@",
+  "port": 8080
+}`;
+    config.setTemplate(existingTemplate);
+    
+    const env = new Env(0, 'DEFAULT', [
+      new EnvParam(1, 'host', 'localhost'), // Already in template
+      new EnvParam(2, 'port', '8080')       // Already in template
+    ]);
+    config.setEnvs([env]);
+
+    // Act: Update template
+    config.updateTemplateFromEnv(env);
+
+    // Assert: Should not add !!! entries for existing placeholders
+    const templateContent = config.template.content;
+    // Count occurrences of @host@
+    const hostCount = (templateContent.match(/@host@/g) || []).length;
+    expect(hostCount).toBe(1); // Only original, no duplicate
+    
+    // Should preserve original structure
+    expect(templateContent).toContain('"host": "@host@"');
+  });
+
+  it('should initialize empty template', () => {
+    // Arrange: Create config with empty template
+    const config = new Config();
+    config.setTemplate('');
+    
+    const env = new Env(0, 'DEFAULT', [
+      new EnvParam(1, 'host', 'localhost')
+    ]);
+    config.setEnvs([env]);
+
+    // Act: Update template
+    config.updateTemplateFromEnv(env);
+
+    // Assert: Should create template with placeholder
+    const templateContent = config.template.content;
+    const templateObj = JSON.parse(templateContent);
+    expect(templateObj['!!! host']).toBe('@host@');
+  });
+
+  it('should not modify invalid JSON template', () => {
+    // Arrange: Create config with invalid JSON template
+    const config = new Config();
+    const invalidTemplate = `{
+  "key": "value"  // missing comma
+  "another": "key"
+}`;
+    config.setTemplate(invalidTemplate);
+    const originalTemplate = config.template.content;
+    
+    const env = new Env(0, 'DEFAULT', [
+      new EnvParam(1, 'host', 'localhost')
+    ]);
+    config.setEnvs([env]);
+
+    // Act: Update template (should not modify invalid JSON)
+    config.updateTemplateFromEnv(env);
+
+    // Assert: Template should remain unchanged
+    expect(config.template.content).toBe(originalTemplate);
+  });
+
+  it('should add multiple new placeholders to existing template', () => {
+    // Arrange
+    const config = new Config();
+    const existingTemplate = `{
+  "name": "myapp"
+}`;
+    config.setTemplate(existingTemplate);
+    
+    const env = new Env(0, 'DEFAULT', [
+      new EnvParam(1, 'host', 'localhost'),
+      new EnvParam(2, 'port', '8080'),
+      new EnvParam(3, 'user', 'admin')
+    ]);
+    config.setEnvs([env]);
+
+    // Act
+    config.updateTemplateFromEnv(env);
+
+    // Assert
+    const templateObj = JSON.parse(config.template.content);
+    expect(templateObj.name).toBe('myapp');
+    expect(templateObj['!!! host']).toBe('@host@');
+    expect(templateObj['!!! port']).toBe('@port@');
+    expect(templateObj['!!! user']).toBe('@user@');
+  });
+
+  it('should only add placeholders for params not in template', () => {
+    // Arrange: Template has @host@ but not @port@
+    const config = new Config();
+    config.setTemplate(`{
+  "host": "@host@",
+  "name": "test"
+}`);
+    
+    const env = new Env(0, 'DEFAULT', [
+      new EnvParam(1, 'host', 'localhost'), // In template
+      new EnvParam(2, 'port', '8080')       // Not in template
+    ]);
+    config.setEnvs([env]);
+
+    // Act
+    config.updateTemplateFromEnv(env);
+
+    // Assert
+    const templateContent = config.template.content;
+    const templateObj = JSON.parse(templateContent);
+    
+    // Should preserve original
+    expect(templateObj.host).toBe('@host@');
+    expect(templateObj.name).toBe('test');
+    
+    // Should add only missing
+    expect(templateObj['!!! port']).toBe('@port@');
+    expect(templateObj['!!! host']).toBeUndefined(); // Not added, already exists
+  });
+});
diff --git a/src/test/JsonValidation.test.ts b/src/test/JsonValidation.test.ts
new file mode 100644
index 0000000..d6a5486
--- /dev/null
+++ b/src/test/JsonValidation.test.ts
@@ -0,0 +1,204 @@
+import { describe, it, expect } from 'vitest';
+
+/**
+ * Helper function that mimics the validation logic in ConfigTemplate.tsx
+ * This is the improved version with comment support
+ */
+function validateJsonWithComments(value: string): { valid: boolean; error?: string } {
+  try {
+    if (!value.trim()) {
+      return { valid: true };
+    }
+
+    // Step 1: Remove /* */ multi-line comments
+    let sanitized = value.replace(/\/\*[\s\S]*?\*\//g, '');
+
+    // Step 2: Process line by line to handle // comments outside quotes
+    const lines = sanitized.split('\n');
+    const processedLines = lines.map(line => {
+      let result = '';
+      let inQuote = false;
+      let quoteChar = '';
+      
+      for (let i = 0; i < line.length; i++) {
+        const char = line[i];
+        const prevChar = i > 0 ? line[i - 1] : '';
+        
+        // Check for quote start/end (not escaped)
+        if ((char === '"' || char === "'") && prevChar !== '\\') {
+          if (!inQuote) {
+            inQuote = true;
+            quoteChar = char;
+          } else if (char === quoteChar) {
+            inQuote = false;
+            quoteChar = '';
+          }
+          result += char;
+        }
+        // Check for // comment start (only outside quotes)
+        else if (!inQuote && char === '/' && line[i + 1] === '/') {
+          break; // Rest of line is comment
+        }
+        else {
+          result += char;
+        }
+      }
+      
+      return result;
+    });
+
+    sanitized = processedLines.join('\n');
+
+    // Step 3: Replace @placeholders@ with dummy values
+    sanitized = sanitized.replace(/@[^@]+@/g, '1');
+
+    JSON.parse(sanitized);
+    return { valid: true };
+  } catch (e) {
+    return { valid: false, error: (e as Error).message };
+  }
+}
+
+describe('JSON Validation - Comment Support', () => {
+  it('should remove single-line // comments outside quotes', () => {
+    const json = `{
+      "key": "value" // this is a comment
+    }`;
+    const result = validateJsonWithComments(json);
+    expect(result.valid).toBe(true);
+  });
+
+  it('should preserve // inside quoted strings', () => {
+    const json = `{
+      "url": "http://example.com/path",
+      "description": "This // that // other"
+    }`;
+    const result = validateJsonWithComments(json);
+    expect(result.valid).toBe(true);
+  });
+
+  it('should preserve URLs with // in values', () => {
+    const json = `{
+      "apiUrl": "http://localhost:8080/api",
+      "cdn": "https://cdn.example.com/assets"
+    }`;
+    const result = validateJsonWithComments(json);
+    expect(result.valid).toBe(true);
+  });
+
+  it('should remove multi-line /* */ comments', () => {
+    const json = `{
+      /* This is a 
+         multi-line comment */
+      "key": "value"
+    }`;
+    const result = validateJsonWithComments(json);
+    expect(result.valid).toBe(true);
+  });
+
+  it('should handle mixed comments and placeholders', () => {
+    const json = `{
+      // Host configuration
+      "host": "@host@",
+      "port": @port@, // unquoted placeholder
+      /* API settings */
+      "apiUrl": "http://@host@:@port@/api" // URL with placeholders
+    }`;
+    const result = validateJsonWithComments(json);
+    expect(result.valid).toBe(true);
+  });
+
+  it('should handle comment-only lines', () => {
+    const json = `{
+      // Just a comment
+      "key": "value"
+      // Another comment
+    }`;
+    const result = validateJsonWithComments(json);
+    expect(result.valid).toBe(true);
+  });
+
+  it('should preserve // in string values with special characters', () => {
+    const json = `{
+      "regex": "pattern // with slashes",
+      "path": "C://Program Files//App",
+      "comment": "text // more text // even more"
+    }`;
+    const result = validateJsonWithComments(json);
+    expect(result.valid).toBe(true);
+  });
+
+  it('should handle escaped quotes correctly', () => {
+    const json = `{
+      "message": "He said \\"hello // world\\""
+    }`;
+    const result = validateJsonWithComments(json);
+    expect(result.valid).toBe(true);
+  });
+
+  it('should reject invalid JSON with comments', () => {
+    const json = `{
+      "key": "value" // missing comma
+      "another": "key"
+    }`;
+    const result = validateJsonWithComments(json);
+    expect(result.valid).toBe(false);
+    expect(result.error).toContain('Expected');
+  });
+
+  it('should handle empty template', () => {
+    const result = validateJsonWithComments('');
+    expect(result.valid).toBe(true);
+  });
+
+  it('should handle whitespace only', () => {
+    const result = validateJsonWithComments('   \n\t  ');
+    expect(result.valid).toBe(true);
+  });
+});
+
+describe('JSON Validation - Placeholder Support', () => {
+  it('should validate quoted placeholders', () => {
+    const json = `{
+      "Host": "@host@",
+      "Port": "@port@"
+    }`;
+    const result = validateJsonWithComments(json);
+    expect(result.valid).toBe(true);
+  });
+
+  it('should validate unquoted placeholders', () => {
+    const json = `{
+      "Host": "@host@",
+      "Port": @port@
+    }`;
+    const result = validateJsonWithComments(json);
+    expect(result.valid).toBe(true);
+  });
+
+  it('should validate placeholders in URLs', () => {
+    const json = `{
+      "ApiUrl": "http://@host@:@port@/api/v1"
+    }`;
+    const result = validateJsonWithComments(json);
+    expect(result.valid).toBe(true);
+  });
+
+  it('should validate complex template with comments and placeholders', () => {
+    const json = `{
+      // Database config
+      "db": {
+        "host": "@db_host@",
+        "port": @db_port@,
+        "url": "jdbc:mysql://@db_host@:@db_port@/mydb" // connection string
+      },
+      /* API settings */
+      "api": {
+        "baseUrl": "https://@api_host@/v1",
+        "timeout": @timeout@
+      }
+    }`;
+    const result = validateJsonWithComments(json);
+    expect(result.valid).toBe(true);
+  });
+});