diff --git a/filter_plugins/generate_all_domains.py b/filter_plugins/generate_all_domains.py
new file mode 100644
index 00000000..b9084352
--- /dev/null
+++ b/filter_plugins/generate_all_domains.py
@@ -0,0 +1,47 @@
+import os
+from ansible.errors import AnsibleFilterError
+
+class FilterModule(object):
+    """
+    Custom Ansible filter to generate a flattened, deduplicated,
+    and sorted list of domains, with optional 'www.' prefixes.
+    """
+
+    def filters(self):
+        return {
+            'generate_all_domains': self.generate_all_domains,
+        }
+
+    @staticmethod
+    def generate_all_domains(domains_dict, include_www=True):
+        """
+        Transform a dict of domains into a flat list of domain strings.
+        Values in domains_dict may be strings, lists, or dicts.
+        If include_www is True, also generate "www." variants.
+        The final list is deduplicated and sorted alphabetically.
+
+        :param domains_dict: dict where each value is str, list, or dict of domains
+        :param include_www:  bool indicating if 'www.' prefixes should be added
+        :return:              sorted list of unique domain names
+        """
+        try:
+            flat = []
+            for val in domains_dict.values():
+                if isinstance(val, str):
+                    flat.append(val)
+                elif isinstance(val, list):
+                    flat.extend(val)
+                elif isinstance(val, dict):
+                    flat.extend(val.values())
+                else:
+                    # skip unsupported types
+                    continue
+
+            if include_www:
+                flat.extend(['www.' + d for d in flat])
+
+            # dedupe and sort
+            return sorted(set(flat))
+
+        except Exception as exc:
+            raise AnsibleFilterError(f"generate_all_domains failed: {exc}")
\ No newline at end of file
diff --git a/tasks/constructor.yml b/tasks/constructor.yml
index 2ece37bf..9964d5ea 100644
--- a/tasks/constructor.yml
+++ b/tasks/constructor.yml
@@ -75,18 +75,13 @@
     set_fact:
       base_sld_domains: "{{ base_domains | map('regex_replace', '^(?:.*\\.)?([^.]+\\.[^.]+)$', '\\1') | list | unique | sort }}"
 
-  - name: Initialise all_domains as empty list
-    set_fact:
-      all_domains: []
-
-  - name: Build all_domains with base + www via loop
-    set_fact:
-      all_domains: "{{ all_domains + [ item, 'www.' ~ item ] }}"
-    loop: "{{ base_domains }}"
-
-  - name: Deduplicate and sort all_domains
-    set_fact:
-      all_domains: "{{ all_domains | unique | sort }}"
+  - set_fact:
+      all_domains: >-
+        {{ domains
+          | generate_all_domains(
+              ('www_redirect' in group_names)
+            )
+        }}
 
   - name: "Merged Variables"
     # Add new merged variables here
diff --git a/tests/unit/test_generate_all_domains.py b/tests/unit/test_generate_all_domains.py
new file mode 100644
index 00000000..64d9c382
--- /dev/null
+++ b/tests/unit/test_generate_all_domains.py
@@ -0,0 +1,52 @@
+import sys
+import os
+import pytest
+
+from filter_plugins.generate_all_domains import FilterModule
+
+@pytest.fixture
+def generate_filter():
+    """
+    Fixture to return the generate_all_domains filter function.
+    """
+    fm = FilterModule()
+    return fm.generate_all_domains
+
+def test_simple_string_values(generate_filter):
+    domains = {'app': 'example.com'}
+    result = generate_filter(domains)
+    # Expect original and www-prefixed, deduped and sorted
+    expected = ['example.com', 'www.example.com']
+    assert result == expected
+
+def test_list_and_dict_values(generate_filter):
+    domains = {
+        'app1': ['one.com', 'two.com'],
+        'app2': {'x': 'x.com', 'y': 'y.com'}
+    }
+    result = generate_filter(domains)
+    expected = sorted([
+        'one.com', 'two.com', 'x.com', 'y.com',
+        'www.one.com', 'www.two.com', 'www.x.com', 'www.y.com'
+    ])
+    assert result == expected
+
+def test_include_www_false(generate_filter):
+    domains = {'app': 'no-www.com'}
+    result = generate_filter(domains, include_www=False)
+    # Only the original domain
+    assert result == ['no-www.com']
+
+def test_deduplicate_and_sort(generate_filter):
+    domains = {
+        'a': 'dup.com',
+        'b': 'dup.com',
+        'c': ['b.com', 'a.com'],
+    }
+    result = generate_filter(domains)
+    # Should contain unique domains sorted alphabetically
+    expected = ['a.com', 'b.com', 'dup.com', 'www.a.com', 'www.b.com', 'www.dup.com']
+    assert result == expected
+
+if __name__ == '__main__':
+    pytest.main()