diff --git a/frontends/nextjs/src/app/api/github/actions/runs/[runId]/logs/route.ts b/frontends/nextjs/src/app/api/github/actions/runs/[runId]/logs/route.ts
index fdcd10691..afe19d493 100644
--- a/frontends/nextjs/src/app/api/github/actions/runs/[runId]/logs/route.ts
+++ b/frontends/nextjs/src/app/api/github/actions/runs/[runId]/logs/route.ts
@@ -37,7 +37,7 @@ export const GET = async (request: NextRequest, { params }: RouteParams) => {
       jobLimit,
     })
 
-    if (!result) {
+    if (result === null || result === undefined) {
       return NextResponse.json({ error: 'Failed to fetch workflow logs' }, { status: 500 })
     }
 
diff --git a/frontends/nextjs/src/app/api/github/actions/runs/route.ts b/frontends/nextjs/src/app/api/github/actions/runs/route.ts
index a4456b9ed..c59d0c18b 100644
--- a/frontends/nextjs/src/app/api/github/actions/runs/route.ts
+++ b/frontends/nextjs/src/app/api/github/actions/runs/route.ts
@@ -11,7 +11,7 @@ export const GET = async (request: NextRequest) => {
     const perPageParam = request.nextUrl.searchParams.get('perPage')
     let perPage = 20
 
-    if (perPageParam) {
+    if (perPageParam !== null && perPageParam !== undefined && perPageParam.length > 0) {
       const parsed = Number(perPageParam)
       if (!Number.isNaN(parsed)) {
         perPage = Math.max(1, Math.min(100, Math.floor(parsed)))
diff --git a/frontends/nextjs/src/app/api/health/route.test.tsx b/frontends/nextjs/src/app/api/health/route.test.tsx
index debe644b8..49b1e0c41 100644
--- a/frontends/nextjs/src/app/api/health/route.test.tsx
+++ b/frontends/nextjs/src/app/api/health/route.test.tsx
@@ -6,7 +6,7 @@ import { GET } from './route'
 describe('GET /api/health', () => {
   it('returns OK status and permission level count', async () => {
     const response = GET(new NextRequest('http://example.com/api/health'))
-    const payload = await response.json()
+    const payload = await response.json() as Record<string, unknown>
 
     expect(payload.status).toBe('ok')
     expect(typeof payload.timestamp).toBe('string')
diff --git a/frontends/nextjs/src/app/api/packages/data/[packageId]/handlers/put-package-data.ts b/frontends/nextjs/src/app/api/packages/data/[packageId]/handlers/put-package-data.ts
index 00969862d..c35d6464d 100644
--- a/frontends/nextjs/src/app/api/packages/data/[packageId]/handlers/put-package-data.ts
+++ b/frontends/nextjs/src/app/api/packages/data/[packageId]/handlers/put-package-data.ts
@@ -18,7 +18,7 @@ interface RouteParams {
 export async function PUT(request: NextRequest, { params }: RouteParams) {
   try {
     const body = await readJson<PackageDataPayload>(request)
-    if (!body?.data || Array.isArray(body.data)) {
+    if (body?.data === null || body?.data === undefined || Array.isArray(body.data)) {
       return NextResponse.json({ error: 'Package data is required' }, { status: 400 })
     }
 
diff --git a/frontends/nextjs/src/app/page.tsx b/frontends/nextjs/src/app/page.tsx
index d00fc6cf8..f5e710980 100644
--- a/frontends/nextjs/src/app/page.tsx
+++ b/frontends/nextjs/src/app/page.tsx
@@ -52,7 +52,7 @@ export default async function RootPage() {
 
     // If route has full component tree, render it directly
     if (route.componentTree !== null && route.componentTree !== undefined && route.componentTree.length > 0) {
-      const componentDef = JSON.parse(route.componentTree)
+      const componentDef = JSON.parse(route.componentTree) as Record<string, unknown>
       return renderJSONComponent(componentDef, {}, {})
     }
 
diff --git a/frontends/nextjs/src/lib/db/app-config/get-app-config.test.ts b/frontends/nextjs/src/lib/db/app-config/get-app-config.test.ts
index e099ac1cd..146e7d7a4 100644
--- a/frontends/nextjs/src/lib/db/app-config/get-app-config.test.ts
+++ b/frontends/nextjs/src/lib/db/app-config/get-app-config.test.ts
@@ -36,7 +36,7 @@ describe('getAppConfig', () => {
 
     const result = await getAppConfig()
 
-    if (expected) {
+    if (expected !== null && expected !== undefined) {
       expect(result).toMatchObject(expected)
     } else {
       expect(result).toBeNull()
diff --git a/frontends/nextjs/src/lib/db/comments/crud/set-comments.test.ts b/frontends/nextjs/src/lib/db/comments/crud/set-comments.test.ts
index 59d141119..b1a8991dd 100644
--- a/frontends/nextjs/src/lib/db/comments/crud/set-comments.test.ts
+++ b/frontends/nextjs/src/lib/db/comments/crud/set-comments.test.ts
@@ -23,8 +23,15 @@ describe('setComments', () => {
     mockDelete.mockResolvedValue(undefined)
     mockCreate.mockResolvedValue(undefined)
 
-    // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    await setComments([{ id: 'new', userId: 'u1', content: 'Hi', createdAt: 1000 }] as any)
+    const testComment: Comment = { 
+      id: 'new', 
+      userId: 'u1', 
+      entityType: 'test',
+      entityId: 'test1',
+      content: 'Hi', 
+      createdAt: 1000 
+    }
+    await setComments([testComment])
 
     expect(mockDelete).toHaveBeenCalledTimes(1)
     expect(mockCreate).toHaveBeenCalledTimes(1)
diff --git a/frontends/nextjs/src/lib/db/components/config/get-component-configs.ts b/frontends/nextjs/src/lib/db/components/config/get-component-configs.ts
index 13f550adb..a8e66c8ba 100644
--- a/frontends/nextjs/src/lib/db/components/config/get-component-configs.ts
+++ b/frontends/nextjs/src/lib/db/components/config/get-component-configs.ts
@@ -18,11 +18,11 @@ export async function getComponentConfigs(): Promise<Record<string, ComponentCon
     configs[config.id] = {
       id: config.id,
       componentId: config.componentId,
-      props: JSON.parse(config.props),
-      styles: JSON.parse(config.styles),
-      events: JSON.parse(config.events),
-      conditionalRendering: config.conditionalRendering
-        ? JSON.parse(config.conditionalRendering)
+      props: JSON.parse(config.props) as Record<string, unknown>,
+      styles: JSON.parse(config.styles) as Record<string, unknown>,
+      events: JSON.parse(config.events) as Record<string, unknown>,
+      conditionalRendering: config.conditionalRendering !== null && config.conditionalRendering !== undefined
+        ? (JSON.parse(config.conditionalRendering) as Record<string, unknown>)
         : undefined,
     }
   }
diff --git a/frontends/nextjs/src/lib/db/css-classes/crud/get-css-classes.ts b/frontends/nextjs/src/lib/db/css-classes/crud/get-css-classes.ts
index c783ae95d..6a4e1614f 100644
--- a/frontends/nextjs/src/lib/db/css-classes/crud/get-css-classes.ts
+++ b/frontends/nextjs/src/lib/db/css-classes/crud/get-css-classes.ts
@@ -10,6 +10,6 @@ export async function getCssClasses(): Promise<CssCategory[]> {
   const rows = result.data as Array<{ name: string; classes: string | string[] }>
   return rows.map(c => ({
     name: c.name,
-    classes: typeof c.classes === 'string' ? JSON.parse(c.classes) : c.classes,
+    classes: typeof c.classes === 'string' ? (JSON.parse(c.classes) as string[]) : c.classes,
   }))
 }
diff --git a/frontends/nextjs/src/lib/db/error-logs/tests/add-error-log.test.ts b/frontends/nextjs/src/lib/db/error-logs/tests/add-error-log.test.ts
index 42cad4f00..40baca45c 100644
--- a/frontends/nextjs/src/lib/db/error-logs/tests/add-error-log.test.ts
+++ b/frontends/nextjs/src/lib/db/error-logs/tests/add-error-log.test.ts
@@ -47,8 +47,8 @@ describe('addErrorLog', () => {
     expect(mockCreate).toHaveBeenCalledWith(
       'ErrorLog',
       expect.objectContaining({
-        id: expect.stringContaining('error_'),
-        timestamp: expect.any(BigInt),
+        id: expect.stringContaining('error_') as string,
+        timestamp: expect.any(BigInt) as bigint,
         level: log.level,
         message: log.message,
         resolved: false,
diff --git a/frontends/nextjs/src/lib/db/error-logs/tests/get-error-logs.test.ts b/frontends/nextjs/src/lib/db/error-logs/tests/get-error-logs.test.ts
index 7eb29dd9f..038e9d16e 100644
--- a/frontends/nextjs/src/lib/db/error-logs/tests/get-error-logs.test.ts
+++ b/frontends/nextjs/src/lib/db/error-logs/tests/get-error-logs.test.ts
@@ -125,7 +125,7 @@ describe('getErrorLogs', () => {
     expect(mockList).toHaveBeenCalledWith('ErrorLog')
     expect(result).toHaveLength(expectedLength)
 
-    if (options?.tenantId && result.length > 0) {
+    if (options?.tenantId !== null && options?.tenantId !== undefined && result.length > 0) {
       expect(result.every(log => log.tenantId === options.tenantId)).toBe(true)
     }
   })