diff --git a/.architecture-rules/frontend.yaml b/.architecture-rules/frontend.yaml
index ab912b25..3d26158d 100644
--- a/.architecture-rules/frontend.yaml
+++ b/.architecture-rules/frontend.yaml
@@ -561,6 +561,39 @@ template_rules:
       exceptions:
         - "shared/macros/pagination.html"
 
+  - id: "TPL-015"
+    name: "Use correct page_header macro API"
+    severity: "error"
+    description: |
+      The page_header macro does not accept a buttons=[] parameter.
+      Use action_label/action_onclick for a single action button,
+      or use page_header_flex with {% call %} for multiple buttons.
+
+      OLD (deprecated - will break):
+        {{ page_header('Title', buttons=[
+            {'text': 'Add', 'icon': 'plus', 'click': 'doSomething()'}
+        ]) }}
+
+      NEW (single action button):
+        {{ page_header('Title', action_label='Add', action_icon='plus', action_onclick='doSomething()') }}
+
+      NEW (multiple buttons - use page_header_flex):
+        {% call page_header_flex(title='Title') %}
+        <button @click="action1()">Button 1</button>
+        <button @click="action2()">Button 2</button>
+        {% endcall %}
+
+      Parameters for page_header:
+        - title, subtitle
+        - action_label, action_url, action_icon, action_onclick
+        - back_url, back_label
+    pattern:
+      file_pattern: "app/templates/**/*.html"
+      anti_patterns:
+        - "page_header\\s*\\([^)]*buttons\\s*="
+      exceptions:
+        - "shared/macros/headers.html"
+
   - id: "TPL-014"
     name: "Use new modal_simple macro API with call block"
     severity: "error"
diff --git a/scripts/validate_architecture.py b/scripts/validate_architecture.py
index 92a34c4d..3bf43e62 100755
--- a/scripts/validate_architecture.py
+++ b/scripts/validate_architecture.py
@@ -1306,6 +1306,38 @@ class ArchitectureValidator:
                     )
                     break  # Only report once per line
 
+    def _check_page_header_macro_api(
+        self, file_path: Path, content: str, lines: list[str]
+    ):
+        """
+        TPL-015: Check for old page_header macro API.
+
+        The page_header macro does not accept a buttons=[] parameter.
+        Use action_label/action_onclick for single button, or page_header_flex for multiple.
+
+        OLD (deprecated): {{ page_header('Title', buttons=[...]) }}
+        NEW (correct):    {{ page_header('Title', action_label='Add', action_onclick='...') }}
+        """
+        # Skip the macro definition file
+        if "shared/macros/headers.html" in str(file_path):
+            return
+
+        if "noqa: tpl-015" in content.lower():
+            return
+
+        for i, line in enumerate(lines, 1):
+            if re.search(r"page_header\s*\([^)]*buttons\s*=", line):
+                self._add_violation(
+                    rule_id="TPL-015",
+                    rule_name="Use correct page_header macro API",
+                    severity=Severity.ERROR,
+                    file_path=file_path,
+                    line_number=i,
+                    message="page_header does not accept 'buttons' parameter",
+                    context=line.strip()[:80],
+                    suggestion="Use action_label/action_onclick, or page_header_flex with {% call %}",
+                )
+
     def _check_alpine_template_vars(
         self, file_path: Path, content: str, lines: list[str], js_content: str
     ):
@@ -3286,6 +3318,9 @@ class ArchitectureValidator:
             # TPL-014: Check for old modal_simple macro API
             self._check_modal_simple_macro_api(file_path, content, lines)
 
+            # TPL-015: Check for old page_header macro API
+            self._check_page_header_macro_api(file_path, content, lines)
+
             # Skip base/partials for TPL-001 check
             if is_base_or_partial:
                 continue