diff --git a/src/components/FormGenerator/ActionButtons/ExpandActionButton/ExpandActionButton.module.css b/src/components/FormGenerator/ActionButtons/ExpandActionButton/ExpandActionButton.module.css
index 9437cb0..26f5372 100644
--- a/src/components/FormGenerator/ActionButtons/ExpandActionButton/ExpandActionButton.module.css
+++ b/src/components/FormGenerator/ActionButtons/ExpandActionButton/ExpandActionButton.module.css
@@ -31,9 +31,15 @@
 
 .chevronIcon {
   font-size: 11px;
-  transition: transform 0.15s ease;
+  transition: transform 0.32s cubic-bezier(0.4, 0, 0.2, 1);
 }
 
 .chevronIconExpanded {
   transform: rotate(90deg);
 }
+
+@media (prefers-reduced-motion: reduce) {
+  .chevronIcon {
+    transition: none;
+  }
+}
diff --git a/src/components/FormGenerator/FormGeneratorTable/ExpandableDetailRow.tsx b/src/components/FormGenerator/FormGeneratorTable/ExpandableDetailRow.tsx
new file mode 100644
index 0000000..c5c956b
--- /dev/null
+++ b/src/components/FormGenerator/FormGeneratorTable/ExpandableDetailRow.tsx
@@ -0,0 +1,67 @@
+import React, { useState, useEffect, useRef, useCallback } from 'react';
+import styles from './FormGeneratorTable.module.css';
+
+export interface ExpandableDetailRowProps {
+  open: boolean;
+  colSpan: number;
+  children: React.ReactNode;
+}
+
+/**
+ * Table detail row with smooth expand/collapse (grid 0fr → 1fr).
+ * Stays mounted until the close animation finishes.
+ */
+export function ExpandableDetailRow({ open, colSpan, children }: ExpandableDetailRowProps) {
+  const [mounted, setMounted] = useState(open);
+  const [revealed, setRevealed] = useState(false);
+  const openRef = useRef(open);
+  openRef.current = open;
+
+  useEffect(() => {
+    if (open) {
+      setMounted(true);
+      const id = requestAnimationFrame(() => {
+        requestAnimationFrame(() => {
+          if (openRef.current) setRevealed(true);
+        });
+      });
+      return () => cancelAnimationFrame(id);
+    }
+    setRevealed(false);
+    const fallback = window.setTimeout(() => {
+      if (!openRef.current) setMounted(false);
+    }, 420);
+    return () => window.clearTimeout(fallback);
+  }, [open]);
+
+  const handleTransitionEnd = useCallback((e: React.TransitionEvent<HTMLDivElement>) => {
+    if (e.target !== e.currentTarget) return;
+    if (e.propertyName !== 'grid-template-rows') return;
+    if (!openRef.current) {
+      setMounted(false);
+    }
+  }, []);
+
+  if (!mounted) return null;
+
+  return (
+    <tr className={styles.expandedDetailRow}>
+      <td
+        colSpan={colSpan}
+        className={`${styles.expandedDetailCell} ${revealed ? styles.expandedDetailCellOpen : ''}`}
+        onClick={(e) => e.stopPropagation()}
+      >
+        <div
+          className={`${styles.expandedCollapsible} ${revealed ? styles.expandedCollapsibleOpen : ''}`}
+          onTransitionEnd={handleTransitionEnd}
+        >
+          <div className={styles.expandedCollapsibleInner}>
+            <div className={styles.expandedDetailInner}>{children}</div>
+          </div>
+        </div>
+      </td>
+    </tr>
+  );
+}
+
+export default ExpandableDetailRow;
diff --git a/src/components/FormGenerator/FormGeneratorTable/FormGeneratorTable.module.css b/src/components/FormGenerator/FormGeneratorTable/FormGeneratorTable.module.css
index 2cc58a6..0fbafd7 100644
--- a/src/components/FormGenerator/FormGeneratorTable/FormGeneratorTable.module.css
+++ b/src/components/FormGenerator/FormGeneratorTable/FormGeneratorTable.module.css
@@ -592,10 +592,37 @@
 }
 
 .expandedDetailCell {
-  padding: 12px 16px 16px;
+  padding: 0 16px;
   vertical-align: top;
-  border-bottom: 2px solid var(--color-border, #e2e8f0);
+  border-bottom: 2px solid transparent;
   box-sizing: border-box;
+  transition:
+    padding 0.32s cubic-bezier(0.4, 0, 0.2, 1),
+    border-color 0.32s cubic-bezier(0.4, 0, 0.2, 1);
+}
+
+.expandedDetailCellOpen {
+  padding: 12px 16px 16px;
+  border-bottom-color: var(--color-border, #e2e8f0);
+}
+
+.expandedCollapsible {
+  display: grid;
+  grid-template-rows: 0fr;
+  opacity: 0;
+  transition:
+    grid-template-rows 0.36s cubic-bezier(0.4, 0, 0.2, 1),
+    opacity 0.28s cubic-bezier(0.4, 0, 0.2, 1);
+}
+
+.expandedCollapsibleOpen {
+  grid-template-rows: 1fr;
+  opacity: 1;
+}
+
+.expandedCollapsibleInner {
+  overflow: hidden;
+  min-height: 0;
 }
 
 .expandedDetailInner {
@@ -604,6 +631,24 @@
   min-width: 0;
   overflow-x: auto;
   overflow-y: visible;
+  transform: translateY(-6px);
+  transition: transform 0.36s cubic-bezier(0.4, 0, 0.2, 1);
+}
+
+.expandedCollapsibleOpen .expandedDetailInner {
+  transform: translateY(0);
+}
+
+@media (prefers-reduced-motion: reduce) {
+  .expandedDetailCell,
+  .expandedCollapsible,
+  .expandedDetailInner {
+    transition: none;
+  }
+
+  .expandedCollapsibleOpen .expandedDetailInner {
+    transform: none;
+  }
 }
 
 /* Items that live inside a group — subtle tint + left connector */
diff --git a/src/components/FormGenerator/FormGeneratorTable/FormGeneratorTable.tsx b/src/components/FormGenerator/FormGeneratorTable/FormGeneratorTable.tsx
index 2815c83..a9943e5 100644
--- a/src/components/FormGenerator/FormGeneratorTable/FormGeneratorTable.tsx
+++ b/src/components/FormGenerator/FormGeneratorTable/FormGeneratorTable.tsx
@@ -79,6 +79,7 @@ import {
   isNumberType,
 } from '../../../utils/attributeTypeMapper';
 import type { AttributeType } from '../../../utils/attributeTypeMapper';
+import { ExpandableDetailRow } from './ExpandableDetailRow';
 import { FaFilter } from 'react-icons/fa';
 import api from '../../../api';
 import { PeriodPicker } from '../../PeriodPicker';
@@ -2760,18 +2761,10 @@ export function FormGeneratorTable<T extends Record<string, any>>({
             );
           })}
         </tr>
-        {isExpanded && renderExpandedRow && (
-          <tr className={styles.expandedDetailRow}>
-            <td
-              colSpan={detailColSpan}
-              className={styles.expandedDetailCell}
-              onClick={(e) => e.stopPropagation()}
-            >
-              <div className={styles.expandedDetailInner}>
-                {renderExpandedRow(row)}
-              </div>
-            </td>
-          </tr>
+        {renderExpandedRow && (
+          <ExpandableDetailRow open={isExpanded} colSpan={detailColSpan}>
+            {renderExpandedRow(row)}
+          </ExpandableDetailRow>
         )}
       </React.Fragment>
     );