diff --git a/core/test/utils/redos_vulnerability_test.dart b/core/test/utils/redos_vulnerability_test.dart
index 5be4bed6f..e8f4f14a0 100644
--- a/core/test/utils/redos_vulnerability_test.dart
+++ b/core/test/utils/redos_vulnerability_test.dart
@@ -174,6 +174,134 @@ void main() {
         expect(stopwatch.elapsedMilliseconds, lessThan(500));
         expect(result, contains('content'));
       });
+
+      test('Should handle Gmail newsletter HTML structure', () {
+        // Real pattern from Gmail promotional emails
+        const gmailHtml = '''
+        <div dir="ltr">
+        <table cellpadding="0" cellspacing="0" border="0" width="100%">
+            <tr>
+            <td style="background-image: url('https://ci3.googleusercontent.com/proxy/ABCDEFGHIJKLMNOP1234567890abcdefghijklmnop=s0-d-e1-ft#https://example.com/images/header.jpg'); background-size: cover;">
+                <p style="font-family: Arial, sans-serif;">Hello User,</p>
+                <p>Visit https://example.com/products for our latest offers.</p>
+            </td>
+            </tr>
+        </table>
+        </div>
+    ''';
+
+        final stopwatch = Stopwatch()..start();
+
+        // Extract plain text
+        final plainText = HtmlUtils.extractPlainText(gmailHtml);
+
+        // Wrap URLs
+        final linkedHtml = HtmlUtils.wrapPlainTextLinks(gmailHtml);
+
+        stopwatch.stop();
+
+        // Performance check
+        expect(stopwatch.elapsedMilliseconds, lessThan(200),
+            reason: 'Gmail HTML processing should be fast');
+
+        // Functional check
+        expect(plainText, contains('Hello User'));
+        expect(plainText, contains('Visit'));
+        expect(linkedHtml, contains('<a href='));
+      });
+
+      test('Should handle URLs with complex query parameters', () {
+        const complexUrls = [
+          // Tracking parameters
+          'https://example.com/article?utm_source=email&utm_medium=newsletter&utm_campaign=spring2024',
+          // Nested URL in parameter
+          'https://redirect.example.com?url=https://target.com/page&ref=email',
+          // Fragment identifier
+          'https://docs.example.com/guide#installation-steps',
+          // Multiple fragments (invalid but should handle)
+          'https://example.com/page#section1#subsection',
+          // Query + Fragment
+          'https://api.example.com/v1/users?id=123&format=json#results',
+          // Encoded characters
+          'https://example.com/search?q=hello%20world&lang=en',
+        ];
+
+        for (final url in complexUrls) {
+          final html = '<p>Visit $url for details</p>';
+
+          final stopwatch = Stopwatch()..start();
+          final result = HtmlUtils.wrapPlainTextLinks(html);
+          stopwatch.stop();
+
+          // Performance check
+          expect(stopwatch.elapsedMilliseconds, lessThan(100),
+              reason: 'Should process quickly: $url');
+
+          // Functional check
+          expect(result, contains('<a href='),
+              reason: 'Should wrap URL: $url');
+          expect(result, contains(url.split('?')[0]),
+              reason: 'Should preserve URL base: $url');
+        }
+      });
+
+      test('Should handle HTML tags at 128 character boundary', () {
+        final exactly128 = '</div${'x' * 122}>';
+
+        // 129 characters (over limit, should still process fast)
+        final over128 = '</div${'x' * 123}>';
+
+        // Very long (1000 chars - malicious)
+        final malicious = '</div${'x' * 995}>';
+
+        final stopwatch1 = Stopwatch()..start();
+        HtmlUtils.addQuoteToggle('Text $exactly128 end');
+        stopwatch1.stop();
+
+        final stopwatch2 = Stopwatch()..start();
+        HtmlUtils.addQuoteToggle('Text $over128 end');
+        stopwatch2.stop();
+
+        final stopwatch3 = Stopwatch()..start();
+        HtmlUtils.addQuoteToggle('Text $malicious end');
+        stopwatch3.stop();
+
+        // All should complete quickly (bounded quantifier prevents backtracking)
+        expect(stopwatch1.elapsedMilliseconds, lessThan(100),
+            reason: '128 chars (boundary) should be fast');
+        expect(stopwatch2.elapsedMilliseconds, lessThan(100),
+            reason: '129 chars (over boundary) should be fast');
+        expect(stopwatch3.elapsedMilliseconds, lessThan(100),
+            reason: '1000 chars (malicious) should be fast');
+      });
+
+      test('Should handle deeply nested HTML structure', () {
+        // 50 levels (realistic maximum)
+        final deepNesting = '${'<div>' * 50}<p>Deep content with https://example.com link</p>${'</div>' * 50}';
+
+        // 100 levels (extreme)
+        final extremeNesting = '${'<span>' * 100}Content${'</span>' * 100}';
+
+        final stopwatch1 = Stopwatch()..start();
+        final plainText1 = HtmlUtils.extractPlainText(deepNesting);
+        final linked1 = HtmlUtils.wrapPlainTextLinks(deepNesting);
+        stopwatch1.stop();
+
+        final stopwatch2 = Stopwatch()..start();
+        final plainText2 = HtmlUtils.extractPlainText(extremeNesting);
+        stopwatch2.stop();
+
+        // Performance checks
+        expect(stopwatch1.elapsedMilliseconds, lessThan(200),
+            reason: '50 levels of nesting should process quickly');
+        expect(stopwatch2.elapsedMilliseconds, lessThan(300),
+            reason: '100 levels of nesting should process quickly');
+
+        // Functional checks
+        expect(plainText1, contains('Deep content'));
+        expect(linked1, contains('<a href='));
+        expect(plainText2, contains('Content'));
+      });
     });
 
     group('StringConvert regex patterns', () {
@@ -238,6 +366,51 @@ void main() {
         expect(result, contains('another@test.com'));
       });
 
+      test('Should handle emails with special characters and edge cases', () {
+        final specialCharEmails = [
+          // Valid special characters in local part
+          'user+tag@example.com',
+          'user.name@example.com',
+          'user_name@example.com',
+          'user-name@example.com',
+          'user123@example.com',
+          '123user@example.com',
+          // International domain
+          'user@example.co.uk',
+          'user@sub.domain.example.com',
+          // Quoted local part (valid but rare)
+          '"user@name"@example.com',
+          '"user name"@example.com',
+          // Edge cases with dots
+          'a.b.c.d@example.com',
+          'user.@example.com', // Invalid but should handle gracefully
+          '.user@example.com', // Invalid but should handle gracefully
+          // Unicode/international emails (if supported)
+          'user@例え.jp',
+          // Very long local part
+          '${'a' * 64}@example.com',
+          // Mixed with other text
+          'Contact us at support@example.com for help',
+          'Multiple emails: alice@test.com, bob@test.org',
+        ];
+
+        for (final input in specialCharEmails) {
+          final stopwatch = Stopwatch()..start();
+          final result = StringConvert.extractEmailAddress(input);
+          stopwatch.stop();
+
+          // Performance check
+          expect(stopwatch.elapsedMilliseconds, lessThan(100),
+              reason: 'Should process quickly: $input');
+
+          // If it looks like a valid email, should extract something
+          if (input.contains('@') && !input.startsWith('.') && !input.endsWith('.')) {
+            expect(result, isNotEmpty,
+                reason: 'Should extract email from: $input');
+          }
+        }
+      });
+
       test('isTextTable should correctly identify valid tables', () {
         const validTables = [
           '''