diff --git a/backend/src/db/api/assets.ts b/backend/src/db/api/assets.ts
index a5ebe51..613671f 100644
--- a/backend/src/db/api/assets.ts
+++ b/backend/src/db/api/assets.ts
@@ -9,6 +9,12 @@ import type {
   DbRelationFilterConfig,
 } from '../../types/index.ts';
 
+function mapProjectId(data: AssetData): string | null | undefined {
+  if (data.projectId !== undefined) return data.projectId;
+  if (data.project !== undefined) return data.project;
+  return undefined;
+}
+
 class AssetsDBApi extends GenericDBApi {
   declare static findBy: AssetsDbApi['findBy'];
 
@@ -105,7 +111,7 @@ class AssetsDBApi extends GenericDBApi {
       embed_provider: data.embed_provider || null,
       checksum: data.checksum || null,
       is_public: data.is_public || false,
-      projectId: data.projectId || data.project || null,
+      projectId: mapProjectId(data),
     };
   }
 }
diff --git a/backend/src/db/api/project_element_defaults.ts b/backend/src/db/api/project_element_defaults.ts
index d4de173..1614f16 100644
--- a/backend/src/db/api/project_element_defaults.ts
+++ b/backend/src/db/api/project_element_defaults.ts
@@ -46,6 +46,14 @@ function isElementSettingsJson(value: unknown): value is ElementSettingsJson {
   return Boolean(value) && typeof value === 'object' && !Array.isArray(value);
 }
 
+function mapProjectId(
+  data: ProjectElementDefaultsData,
+): string | null | undefined {
+  if (data.projectId !== undefined) return data.projectId;
+  if (data.project !== undefined) return data.project;
+  return undefined;
+}
+
 function isGlobalElementDefaultRecord(
   value: EntityRecord,
 ): value is GlobalElementDefaultRecord {
@@ -206,7 +214,7 @@ class Project_element_defaultsDBApi extends GenericDBApi {
       settings_json: stringifySettings(data.settings_json),
       source_element_id: data.source_element_id ?? null,
       snapshot_version: data.snapshot_version ?? 1,
-      projectId: data.projectId || data.project || null,
+      projectId: mapProjectId(data),
     };
   }
 
diff --git a/backend/src/types/assets.ts b/backend/src/types/assets.ts
index fc72db3..cd87a4d 100644
--- a/backend/src/types/assets.ts
+++ b/backend/src/types/assets.ts
@@ -69,7 +69,7 @@ export interface AssetFieldMapping {
   embed_provider: string | null;
   checksum: string | null;
   is_public: boolean;
-  projectId: string | null;
+  projectId: string | null | undefined;
 }
 
 export interface AssetVariantData {
diff --git a/backend/src/types/project-element-defaults.ts b/backend/src/types/project-element-defaults.ts
index 9413b3e..de0d789 100644
--- a/backend/src/types/project-element-defaults.ts
+++ b/backend/src/types/project-element-defaults.ts
@@ -46,7 +46,7 @@ export interface ProjectElementDefaultsFieldMapping {
   settings_json: string | null;
   source_element_id: string | null;
   snapshot_version: number;
-  projectId: string | null;
+  projectId: string | null | undefined;
 }
 
 export interface ProjectElementDefaultsListFilter {
diff --git a/backend/tests/update-contracts.test.ts b/backend/tests/update-contracts.test.ts
index 2795065..ff6baa9 100644
--- a/backend/tests/update-contracts.test.ts
+++ b/backend/tests/update-contracts.test.ts
@@ -2,7 +2,9 @@ import assert from 'node:assert/strict';
 import test from 'node:test';
 
 import db from '../src/db/models/index.ts';
+import AssetsDBApi from '../src/db/api/assets.ts';
 import GenericDBApi from '../src/db/api/base.api.ts';
+import ProjectElementDefaultsDBApi from '../src/db/api/project_element_defaults.ts';
 import { createEntityService } from '../src/factories/service.factory.ts';
 import type {
   CurrentUser,
@@ -377,6 +379,48 @@ void test('GenericDBApi.partialUpdate rejects positional signature', async () =>
   );
 });
 
+void test('ProjectElementDefaultsDBApi mapping preserves project relation when omitted', () => {
+  const mapped = ProjectElementDefaultsDBApi.getFieldMapping({
+    element_type: 'navigation_next',
+    name: 'Navigation Forward Button',
+    sort_order: 1,
+    settings_json: { opacity: '0.5' },
+  });
+
+  assert.equal(mapped.projectId, undefined);
+});
+
+void test('ProjectElementDefaultsDBApi mapping keeps explicit project relation', () => {
+  const mapped = ProjectElementDefaultsDBApi.getFieldMapping({
+    element_type: 'navigation_next',
+    projectId: 'project-1',
+    settings_json: { opacity: '0.5' },
+  });
+
+  assert.equal(mapped.projectId, 'project-1');
+});
+
+void test('AssetsDBApi mapping preserves project relation when omitted', () => {
+  const mapped = AssetsDBApi.getFieldMapping({
+    name: 'Lobby image',
+    asset_type: 'image',
+    storage_key: 'assets/lobby.jpg',
+  });
+
+  assert.equal(mapped.projectId, undefined);
+});
+
+void test('AssetsDBApi mapping keeps explicit project relation', () => {
+  const mapped = AssetsDBApi.getFieldMapping({
+    name: 'Lobby image',
+    asset_type: 'image',
+    projectId: 'project-1',
+    storage_key: 'assets/lobby.jpg',
+  });
+
+  assert.equal(mapped.projectId, 'project-1');
+});
+
 void test('createEntityService update uses object signature and manages own transaction', async () => {
   const calls: UpdateContractCalls = {};
   const transaction: TestManagedTransaction = {
diff --git a/frontend/src/lib/elementStyles.ts b/frontend/src/lib/elementStyles.ts
index 1d18ee0..ef3b86a 100644
--- a/frontend/src/lib/elementStyles.ts
+++ b/frontend/src/lib/elementStyles.ts
@@ -240,6 +240,7 @@ export const ELEMENT_STYLE_PROPS = [
   'fontWeight',
   'border',
   'borderRadius',
+  'opacity',
   'boxShadow',
   'display',
   'position',
@@ -251,11 +252,6 @@ export const ELEMENT_STYLE_PROPS = [
   'color',
 ] as const;
 
-/**
- * Properties that need numeric conversion
- */
-const NUMERIC_PROPS = ['opacity', 'zIndex'] as const;
-
 /**
  * Get trimmed CSS value from unknown input.
  * Returns empty string for null/undefined, but preserves '0' for explicit zero values.
@@ -343,9 +339,9 @@ export function buildElementStyle(
 }
 
 /**
- * All style property names including numeric ones.
+ * All style property names.
  * Used for form state management in element-type-defaults admin.
  */
-export const ALL_STYLE_PROPS = [...ELEMENT_STYLE_PROPS, 'opacity'] as const;
+export const ALL_STYLE_PROPS = ELEMENT_STYLE_PROPS;
 
 export type StylePropName = (typeof ALL_STYLE_PROPS)[number];