diff --git a/frontends/nextjs/src/app/api/v1/[...slug]/route.ts b/frontends/nextjs/src/app/api/v1/[...slug]/route.ts
index 7e7a0c208..47f3b62e7 100644
--- a/frontends/nextjs/src/app/api/v1/[...slug]/route.ts
+++ b/frontends/nextjs/src/app/api/v1/[...slug]/route.ts
@@ -67,11 +67,11 @@ async function handleRequest(
   const tenantResult = await validateTenantAccess(
     user,
     route.tenant,
-    packageResult.package?.minLevel || 1
+    packageResult.package?.minLevel ?? 1
   )
-  if (!tenantResult.allowed) {
-    const status = !user ? STATUS.UNAUTHORIZED : STATUS.FORBIDDEN
-    return errorResponse(tenantResult.reason || 'Access denied', status)
+  if (tenantResult.allowed === false) {
+    const status = user === null ? STATUS.UNAUTHORIZED : STATUS.FORBIDDEN
+    return errorResponse(tenantResult.reason ?? 'Access denied', status)
   }
 
   // 5. Execute the DBAL operation
diff --git a/frontends/nextjs/src/app/providers/use-theme.ts b/frontends/nextjs/src/app/providers/use-theme.ts
index 3ad5e0b2e..d091cc966 100644
--- a/frontends/nextjs/src/app/providers/use-theme.ts
+++ b/frontends/nextjs/src/app/providers/use-theme.ts
@@ -4,7 +4,7 @@ import { ThemeContext } from './theme-context'
 
 export function useTheme() {
   const context = useContext(ThemeContext)
-  if (!context) {
+  if (context === null || context === undefined) {
     throw new Error('useTheme must be used within Providers')
   }
   return context
diff --git a/frontends/nextjs/src/app/ui/[[...slug]]/page.tsx b/frontends/nextjs/src/app/ui/[[...slug]]/page.tsx
index 55aec75e0..c2d14844f 100644
--- a/frontends/nextjs/src/app/ui/[[...slug]]/page.tsx
+++ b/frontends/nextjs/src/app/ui/[[...slug]]/page.tsx
@@ -24,7 +24,7 @@ interface PageProps {
  */
 export default async function DynamicUIPage({ params }: PageProps) {
   const resolvedParams = await params
-  const slug = resolvedParams.slug || []
+  const slug = resolvedParams.slug ?? []
   const path = '/' + slug.join('/')
 
   // Prefer Lua package-based UI pages, fallback to database-backed pages
@@ -51,7 +51,7 @@ export default async function DynamicUIPage({ params }: PageProps) {
  */
 export async function generateMetadata({ params }: PageProps): Promise<Metadata> {
   const resolvedParams = await params
-  const slug = resolvedParams.slug || []
+  const slug = resolvedParams.slug ?? []
   const path = '/' + slug.join('/')
 
   const pageData = (await loadPageFromLuaPackages(path)) ?? (await loadPageFromDb(path))
diff --git a/frontends/nextjs/src/components/get-component-icon.tsx b/frontends/nextjs/src/components/get-component-icon.tsx
index 203288835..bf9954d7c 100644
--- a/frontends/nextjs/src/components/get-component-icon.tsx
+++ b/frontends/nextjs/src/components/get-component-icon.tsx
@@ -51,5 +51,5 @@ const iconMap: Record<string, ComponentType<IconProps>> = {
 
 export function getComponentIcon(iconName: string, props?: IconProps): ReactElement | null {
   const Icon = iconMap[iconName]
-  return Icon ? <Icon {...props} /> : null
+  return Icon !== null && Icon !== undefined ? <Icon {...props} /> : null
 }
diff --git a/frontends/nextjs/src/components/ui-page-renderer/UIPageRenderer.tsx b/frontends/nextjs/src/components/ui-page-renderer/UIPageRenderer.tsx
index bc7e376a6..989062ea7 100644
--- a/frontends/nextjs/src/components/ui-page-renderer/UIPageRenderer.tsx
+++ b/frontends/nextjs/src/components/ui-page-renderer/UIPageRenderer.tsx
@@ -23,7 +23,7 @@ export function UIPageRenderer({ pageData }: UIPageRendererProps) {
 
   // Provide action handlers via context
   return (
-    <UIPageActionsContext.Provider value={pageData.actions || {}}>
+    <UIPageActionsContext.Provider value={pageData.actions ?? {}}>
       {elements}
     </UIPageActionsContext.Provider>
   )
diff --git a/frontends/nextjs/src/lib/db/auth/queries/authenticate-user.ts b/frontends/nextjs/src/lib/db/auth/queries/authenticate-user.ts
index b42399258..fb516a7a3 100644
--- a/frontends/nextjs/src/lib/db/auth/queries/authenticate-user.ts
+++ b/frontends/nextjs/src/lib/db/auth/queries/authenticate-user.ts
@@ -42,7 +42,7 @@ export const authenticateUser = async (
     where: { username },
   })
 
-  if (!userRecord) {
+  if (userRecord === null || userRecord === undefined) {
     return { success: false, user: null, error: 'user_not_found' }
   }
 
diff --git a/frontends/nextjs/src/lib/db/auth/queries/get-user-by-email.ts b/frontends/nextjs/src/lib/db/auth/queries/get-user-by-email.ts
index 2fee7b5e4..d9158600b 100644
--- a/frontends/nextjs/src/lib/db/auth/queries/get-user-by-email.ts
+++ b/frontends/nextjs/src/lib/db/auth/queries/get-user-by-email.ts
@@ -15,11 +15,11 @@ export const getUserByEmail = async (
   const record = await adapter.findFirst('User', {
     where: {
       email,
-      ...(options?.tenantId ? { tenantId: options.tenantId } : {}),
+      ...(options?.tenantId !== null && options?.tenantId !== undefined ? { tenantId: options.tenantId } : {}),
     },
   })
 
-  if (!record) {
+  if (record === null || record === undefined) {
     return null
   }
 
diff --git a/frontends/nextjs/src/lib/db/auth/queries/get-user-by-username.ts b/frontends/nextjs/src/lib/db/auth/queries/get-user-by-username.ts
index 251da9f4a..fe65cdec6 100644
--- a/frontends/nextjs/src/lib/db/auth/queries/get-user-by-username.ts
+++ b/frontends/nextjs/src/lib/db/auth/queries/get-user-by-username.ts
@@ -15,11 +15,11 @@ export const getUserByUsername = async (
   const record = await adapter.findFirst('User', {
     where: {
       username,
-      ...(options?.tenantId ? { tenantId: options.tenantId } : {}),
+      ...(options?.tenantId !== null && options?.tenantId !== undefined ? { tenantId: options.tenantId } : {}),
     },
   })
 
-  if (!record) {
+  if (record === null || record === undefined) {
     return null
   }
 
diff --git a/frontends/nextjs/src/lib/db/comments/crud/add-comment.ts b/frontends/nextjs/src/lib/db/comments/crud/add-comment.ts
index edb102022..2aef7156f 100644
--- a/frontends/nextjs/src/lib/db/comments/crud/add-comment.ts
+++ b/frontends/nextjs/src/lib/db/comments/crud/add-comment.ts
@@ -11,7 +11,7 @@ export async function addComment(comment: Comment): Promise<void> {
     userId: comment.userId,
     content: comment.content,
     createdAt: BigInt(comment.createdAt),
-    updatedAt: comment.updatedAt ? BigInt(comment.updatedAt) : null,
-    parentId: comment.parentId,
+    updatedAt: comment.updatedAt !== null && comment.updatedAt !== undefined ? BigInt(comment.updatedAt) : null,
+    parentId: comment.parentId ?? null,
   })
 }
diff --git a/frontends/nextjs/src/lib/db/comments/crud/get-comments.ts b/frontends/nextjs/src/lib/db/comments/crud/get-comments.ts
index 31cb3b7ba..f52970be4 100644
--- a/frontends/nextjs/src/lib/db/comments/crud/get-comments.ts
+++ b/frontends/nextjs/src/lib/db/comments/crud/get-comments.ts
@@ -25,7 +25,7 @@ export async function getComments(): Promise<Comment[]> {
     entityId: c.entityId,
     content: c.content,
     createdAt: Number(c.createdAt),
-    updatedAt: c.updatedAt ? Number(c.updatedAt) : undefined,
-    parentId: c.parentId || undefined,
+    updatedAt: (c.updatedAt !== null && c.updatedAt !== undefined) ? Number(c.updatedAt) : undefined,
+    parentId: (c.parentId !== null && c.parentId !== undefined) ? c.parentId : undefined,
   }))
 }
diff --git a/frontends/nextjs/src/lib/db/comments/crud/set-comments.ts b/frontends/nextjs/src/lib/db/comments/crud/set-comments.ts
index 96b80fe18..d2a5052fd 100644
--- a/frontends/nextjs/src/lib/db/comments/crud/set-comments.ts
+++ b/frontends/nextjs/src/lib/db/comments/crud/set-comments.ts
@@ -24,8 +24,8 @@ export async function setComments(comments: Comment[]): Promise<void> {
       userId: comment.userId,
       content: comment.content,
       createdAt: BigInt(comment.createdAt),
-      updatedAt: comment.updatedAt ? BigInt(comment.updatedAt) : null,
-      parentId: comment.parentId,
+      updatedAt: comment.updatedAt !== null && comment.updatedAt !== undefined ? BigInt(comment.updatedAt) : null,
+      parentId: comment.parentId ?? null,
     })
   }
 }
diff --git a/frontends/nextjs/src/lib/db/components/config/crud/operations/add-component-config.ts b/frontends/nextjs/src/lib/db/components/config/crud/operations/add-component-config.ts
index c9b472133..6169d2db1 100644
--- a/frontends/nextjs/src/lib/db/components/config/crud/operations/add-component-config.ts
+++ b/frontends/nextjs/src/lib/db/components/config/crud/operations/add-component-config.ts
@@ -9,7 +9,7 @@ export async function addComponentConfig(config: ComponentConfig): Promise<void>
     props: JSON.stringify(config.props),
     styles: JSON.stringify(config.styles),
     events: JSON.stringify(config.events),
-    conditionalRendering: config.conditionalRendering
+    conditionalRendering: config.conditionalRendering !== null && config.conditionalRendering !== undefined
       ? JSON.stringify(config.conditionalRendering)
       : null,
   })
diff --git a/frontends/nextjs/src/lib/db/components/config/crud/operations/update-component-config.ts b/frontends/nextjs/src/lib/db/components/config/crud/operations/update-component-config.ts
index b51c1b548..3b00937f9 100644
--- a/frontends/nextjs/src/lib/db/components/config/crud/operations/update-component-config.ts
+++ b/frontends/nextjs/src/lib/db/components/config/crud/operations/update-component-config.ts
@@ -12,7 +12,7 @@ export async function updateComponentConfig(
   if (updates.styles !== undefined) data.styles = JSON.stringify(updates.styles)
   if (updates.events !== undefined) data.events = JSON.stringify(updates.events)
   if (updates.conditionalRendering !== undefined) {
-    data.conditionalRendering = updates.conditionalRendering
+    data.conditionalRendering = updates.conditionalRendering !== null && updates.conditionalRendering !== undefined
       ? JSON.stringify(updates.conditionalRendering)
       : null
   }
diff --git a/frontends/nextjs/src/lib/db/components/config/set-component-configs.ts b/frontends/nextjs/src/lib/db/components/config/set-component-configs.ts
index 256ba4c43..e7ae93767 100644
--- a/frontends/nextjs/src/lib/db/components/config/set-component-configs.ts
+++ b/frontends/nextjs/src/lib/db/components/config/set-component-configs.ts
@@ -22,7 +22,7 @@ export async function setComponentConfigs(configs: Record<string, ComponentConfi
       props: JSON.stringify(config.props),
       styles: JSON.stringify(config.styles),
       events: JSON.stringify(config.events),
-      conditionalRendering: config.conditionalRendering
+      conditionalRendering: config.conditionalRendering !== null && config.conditionalRendering !== undefined
         ? JSON.stringify(config.conditionalRendering)
         : null,
     })
diff --git a/frontends/nextjs/src/lib/db/components/hierarchy/get-component-hierarchy.ts b/frontends/nextjs/src/lib/db/components/hierarchy/get-component-hierarchy.ts
index c2a8ec5c2..2ab0e25d6 100644
--- a/frontends/nextjs/src/lib/db/components/hierarchy/get-component-hierarchy.ts
+++ b/frontends/nextjs/src/lib/db/components/hierarchy/get-component-hierarchy.ts
@@ -18,7 +18,7 @@ export async function getComponentHierarchy(): Promise<Record<string, ComponentN
     hierarchy[node.id] = {
       id: node.id,
       type: node.type,
-      parentId: node.parentId || undefined,
+      parentId: node.parentId !== null && node.parentId !== undefined ? node.parentId : undefined,
       childIds: JSON.parse(node.childIds),
       order: node.order,
       pageId: node.pageId,