diff --git a/packages/design/src/FormManager/FormEdit/components/PreviewSequencePattern/index.tsx b/packages/design/src/FormManager/FormEdit/components/PreviewSequencePattern/index.tsx
index 0f7d0405..6dfe7144 100644
--- a/packages/design/src/FormManager/FormEdit/components/PreviewSequencePattern/index.tsx
+++ b/packages/design/src/FormManager/FormEdit/components/PreviewSequencePattern/index.tsx
@@ -8,6 +8,7 @@ import { PatternEditComponent } from '../../types';
 
 // TODO: consider merging this component with DraggableList, to clean up
 // sematics around how its children are handled.
+// Counterpoint: it's nice to have state management separate from DraggableList.
 export const PatternPreviewSequence: PatternEditComponent<
   SequenceProps
 > = props => {
diff --git a/packages/forms/src/builder/builder.test.ts b/packages/forms/src/builder/builder.test.ts
index e15c80aa..96f4037b 100644
--- a/packages/forms/src/builder/builder.test.ts
+++ b/packages/forms/src/builder/builder.test.ts
@@ -17,15 +17,15 @@ describe('form builder', () => {
 
   it('addPattern preserves existing structure', () => {
     const initial = createTestBlueprint();
-    const newBuilder = new BlueprintBuilder(defaultFormConfig, initial);
-    const newPattern = newBuilder.addPatternToPage('input');
-    expect(newBuilder.form.patterns[newPattern.id]).toEqual(newPattern);
+    const builder = new BlueprintBuilder(defaultFormConfig, initial);
+    const newPattern = builder.addPatternToPage('input');
+    expect(builder.form.patterns[newPattern.id]).toEqual(newPattern);
     const oldPage = getPattern<PagePattern>(initial, 'page-1');
-    const newPage = getPattern<PagePattern>(newBuilder.form, 'page-1');
-    expect(newPage.data.patterns).toEqual([
-      ...oldPage.data.patterns,
-      newPattern.id,
-    ]);
+    const newPage = getPattern<PagePattern>(builder.form, 'page-1');
+    expect(newPage.data).toEqual({
+      ...oldPage.data,
+      patterns: [...oldPage.data.patterns, newPattern.id],
+    });
   });
 
   it('removePattern removes pattern and sequence reference', () => {
diff --git a/packages/forms/src/index.ts b/packages/forms/src/index.ts
index b2027016..68edf48e 100644
--- a/packages/forms/src/index.ts
+++ b/packages/forms/src/index.ts
@@ -203,6 +203,7 @@ export const addPatternToPage = (
       [pagePattern.id]: {
         ...pagePattern,
         data: {
+          ...pagePattern.data,
           patterns: [...pagePattern.data.patterns, pattern.id],
         },
       } satisfies SequencePattern,