diff --git a/src/phase_z2_pipeline.py b/src/phase_z2_pipeline.py
index 2d03df8..5d46e9e 100644
--- a/src/phase_z2_pipeline.py
+++ b/src/phase_z2_pipeline.py
@@ -748,7 +748,36 @@ def run_overflow_check(html_path: Path) -> dict:
                 zones.push(m);
             });
 
-            return { slide: slideM, slide_body: bodyM, zones };
+            // B5 v0 — frame_slot_metrics (per-cell measurement of [data-frame-slot-id])
+            // 현재 F29 partial 만 marker 보유 (process_column / product_column × 3 cells = 6 entries 기대).
+            // 다른 frame (F13 / F16) 은 marker 미적용 → entry 0 — 정상.
+            const frame_slot_metrics = [];
+            slide.querySelectorAll('[data-frame-slot-id]').forEach((cell) => {
+                const slotId = cell.getAttribute('data-frame-slot-id');
+                const m2 = measure(cell);
+                const parentZone = cell.closest('.zone');
+                const zonePos = parentZone
+                    ? (parentZone.getAttribute('data-zone-position') || 'unknown')
+                    : 'unknown';
+                const zoneTid = parentZone
+                    ? (parentZone.getAttribute('data-template-id') || '?')
+                    : '?';
+                frame_slot_metrics.push({
+                    zone_position: zonePos,
+                    zone_template_id: zoneTid,
+                    frame_slot_id: slotId,
+                    class_name: cell.className,
+                    clientWidth: m2.clientWidth,
+                    clientHeight: m2.clientHeight,
+                    scrollWidth: m2.scrollWidth,
+                    scrollHeight: m2.scrollHeight,
+                    excess_x: m2.excess_x,
+                    excess_y: m2.excess_y,
+                    overflowed: m2.overflowed,
+                });
+            });
+
+            return { slide: slideM, slide_body: bodyM, zones, frame_slot_metrics };
         """)
 
         screenshot_path = html_path.parent / "preview.png"
diff --git a/templates/phase_z2/families/process_product_two_way.html b/templates/phase_z2/families/process_product_two_way.html
index ab06f8c..137cdf6 100644
--- a/templates/phase_z2/families/process_product_two_way.html
+++ b/templates/phase_z2/families/process_product_two_way.html
@@ -209,7 +209,7 @@ slots: title (omitted), banner_left, banner_right,
 
       {# ───── Row 1: section 1 ───── #}
       {% set s1 = slot_payload.process.sections[0] %}
-      <div class="f29b__cell f29b__cell--left">
+      <div class="f29b__cell f29b__cell--left" data-frame-slot-id="process_column">
         {% if s1.title %}
         <div class="f29b__section-title">{{ s1.title | safe }}</div>
         {% if s1.transforms %}
@@ -236,7 +236,7 @@ slots: title (omitted), banner_left, banner_right,
       </div>
 
       {% set p1 = slot_payload.product.sections[0] %}
-      <div class="f29b__cell f29b__cell--right">
+      <div class="f29b__cell f29b__cell--right" data-frame-slot-id="product_column">
         {% if p1.title %}
         <div class="f29b__section-title">{{ p1.title | safe }}</div>
         {% for line in p1.text_lines %}<div class="text-line text-line--bullet{% if line.indent > 0 %} text-line--indent-{{ line.indent }}{% endif %}">{{ line.text | safe }}</div>{% endfor %}
@@ -245,7 +245,7 @@ slots: title (omitted), banner_left, banner_right,
 
       {# ───── Row 2: section 2 ───── #}
       {% set s2 = slot_payload.process.sections[1] %}
-      <div class="f29b__cell f29b__cell--left">
+      <div class="f29b__cell f29b__cell--left" data-frame-slot-id="process_column">
         {% if s2.title %}
         <div class="f29b__section-title">{{ s2.title | safe }}</div>
         {% for line in s2.text_lines %}<div class="text-line text-line--bullet{% if line.indent > 0 %} text-line--indent-{{ line.indent }}{% endif %}">{{ line.text | safe }}</div>{% endfor %}
@@ -253,7 +253,7 @@ slots: title (omitted), banner_left, banner_right,
       </div>
 
       {% set p2 = slot_payload.product.sections[1] %}
-      <div class="f29b__cell f29b__cell--right">
+      <div class="f29b__cell f29b__cell--right" data-frame-slot-id="product_column">
         {% if p2.title %}
         <div class="f29b__section-title">{{ p2.title | safe }}</div>
         {% for line in p2.text_lines %}<div class="text-line text-line--bullet{% if line.indent > 0 %} text-line--indent-{{ line.indent }}{% endif %}">{{ line.text | safe }}</div>{% endfor %}
@@ -265,7 +265,7 @@ slots: title (omitted), banner_left, banner_right,
 
       {# ───── Row 3: section 3 ───── #}
       {% set s3 = slot_payload.process.sections[2] %}
-      <div class="f29b__cell f29b__cell--left">
+      <div class="f29b__cell f29b__cell--left" data-frame-slot-id="process_column">
         {% if s3.title %}
         <div class="f29b__section-title">{{ s3.title | safe }}</div>
         {% for line in s3.text_lines %}<div class="text-line text-line--bullet{% if line.indent > 0 %} text-line--indent-{{ line.indent }}{% endif %}">{{ line.text | safe }}</div>{% endfor %}
@@ -273,7 +273,7 @@ slots: title (omitted), banner_left, banner_right,
       </div>
 
       {% set p3 = slot_payload.product.sections[2] %}
-      <div class="f29b__cell f29b__cell--right">
+      <div class="f29b__cell f29b__cell--right" data-frame-slot-id="product_column">
         {% if p3.title %}
         <div class="f29b__section-title">{{ p3.title | safe }}{% if p3.sub_title %}<span class="f29b__section-title__sub">{{ p3.sub_title | safe }}</span>{% endif %}</div>
         {% for line in p3.text_lines %}<div class="text-line text-line--bullet{% if line.indent > 0 %} text-line--indent-{{ line.indent }}{% endif %}">{{ line.text | safe }}</div>{% endfor %}