diff --git a/frontends/nextjs/src/lib/api/retry.test.ts b/frontends/nextjs/src/lib/api/retry.test.ts
index d19626b2d..992995fb8 100644
--- a/frontends/nextjs/src/lib/api/retry.test.ts
+++ b/frontends/nextjs/src/lib/api/retry.test.ts
@@ -20,9 +20,11 @@ describe('retry utilities', () => {
       { statusCode: 503, shouldRetry: true, description: 'service unavailable (retryable)' },
       { statusCode: 429, shouldRetry: true, description: 'rate limited (retryable)' },
     ])('should handle $description correctly', async ({ statusCode, shouldRetry }) => {
+      let callCount = 0
       const mockFetch = vi.fn(async () => { // eslint-disable-line @typescript-eslint/require-await
+        const currentCall = callCount++
         return new Response(JSON.stringify({ test: 'data' }), {
-          status: shouldRetry ? (mockFetch.mock.calls.length === 0 ? statusCode : 200) : statusCode,
+          status: shouldRetry ? (currentCall === 0 ? statusCode : 200) : statusCode,
         })
       })
 
@@ -112,9 +114,10 @@ describe('retry utilities', () => {
         throw new Error('Network error')
       })
 
-      const promise = retryFetch(mockFetch, { maxRetries: 2, initialDelayMs: 10 })
-      
       // Fast-forward through all retry delays
+      const promise = retryFetch(mockFetch, { maxRetries: 2, initialDelayMs: 10 })
+      // Attach a catch handler to prevent unhandled rejection warning
+      promise.catch(() => {})
       await vi.advanceTimersByTimeAsync(500)
       
       await expect(promise).rejects.toThrow('Network error')
@@ -180,8 +183,10 @@ describe('retry utilities', () => {
         throw new Error('Persistent error')
       })
 
+      // Fast-forward through all retry delays
       const promise = retry(mockFn, { maxRetries: 2, initialDelayMs: 10 })
-      
+      // Attach a catch handler to prevent unhandled rejection warning
+      promise.catch(() => {})
       await vi.advanceTimersByTimeAsync(500)
       
       await expect(promise).rejects.toThrow('Persistent error')
diff --git a/frontends/nextjs/src/lib/compiler/index.ts b/frontends/nextjs/src/lib/compiler/index.ts
index c744ba10e..9810bb5fd 100644
--- a/frontends/nextjs/src/lib/compiler/index.ts
+++ b/frontends/nextjs/src/lib/compiler/index.ts
@@ -37,7 +37,7 @@ export async function compile(source: string, options?: CompileOptions): Promise
     return {
       code: result.code,
       // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition, @typescript-eslint/prefer-nullish-coalescing
-      map: (result.map !== null && result.map !== undefined) ? result.map : undefined,
+      map: (result.map !== null && result.map !== undefined && result.map !== '') ? result.map : undefined,
     }
   } catch (error) {
     // Return compilation error as a comment in the code
diff --git a/frontends/nextjs/src/lib/entities/api-client.ts b/frontends/nextjs/src/lib/entities/api-client.ts
index 1e32bf64f..cc5af2eec 100644
--- a/frontends/nextjs/src/lib/entities/api-client.ts
+++ b/frontends/nextjs/src/lib/entities/api-client.ts
@@ -72,7 +72,12 @@ export async function fetchEntityList(
     })
     
     if (!response.ok) {
-      const errorData = await response.json().catch(() => ({ error: 'Unknown error' })) as { error?: string }
+      let errorData: { error?: string } = { error: 'Unknown error' }
+      try {
+        errorData = await response.json() as { error?: string }
+      } catch {
+        // If JSON parsing fails, use default error
+      }
       return {
          
         error: errorData.error ?? `HTTP ${response.status}`,
@@ -121,7 +126,12 @@ export async function fetchEntity(
     })
     
     if (!response.ok) {
-      const errorData = await response.json().catch(() => ({ error: 'Unknown error' })) as { error?: string }
+      let errorData: { error?: string } = { error: 'Unknown error' }
+      try {
+        errorData = await response.json() as { error?: string }
+      } catch {
+        // If JSON parsing fails, use default error
+      }
       return {
          
         error: errorData.error ?? `HTTP ${response.status}`,
@@ -172,7 +182,12 @@ export async function createEntity(
     })
     
     if (!response.ok) {
-      const errorData = await response.json().catch(() => ({ error: 'Unknown error' })) as { error?: string }
+      let errorData: { error?: string } = { error: 'Unknown error' }
+      try {
+        errorData = await response.json() as { error?: string }
+      } catch {
+        // If JSON parsing fails, use default error
+      }
       return {
          
         error: errorData.error ?? `HTTP ${response.status}`,
@@ -225,7 +240,12 @@ export async function updateEntity(
     })
     
     if (!response.ok) {
-      const errorData = await response.json().catch(() => ({ error: 'Unknown error' })) as { error?: string }
+      let errorData: { error?: string } = { error: 'Unknown error' }
+      try {
+        errorData = await response.json() as { error?: string }
+      } catch {
+        // If JSON parsing fails, use default error
+      }
       return {
          
         error: errorData.error ?? `HTTP ${response.status}`,
@@ -275,7 +295,12 @@ export async function deleteEntity(
     })
     
     if (!response.ok) {
-      const errorData = await response.json().catch(() => ({ error: 'Unknown error' })) as { error?: string }
+      let errorData: { error?: string } = { error: 'Unknown error' }
+      try {
+        errorData = await response.json() as { error?: string }
+      } catch {
+        // If JSON parsing fails, use default error
+      }
       return {
          
         error: errorData.error ?? `HTTP ${response.status}`,
diff --git a/frontends/nextjs/src/lib/middleware/auth-middleware.ts b/frontends/nextjs/src/lib/middleware/auth-middleware.ts
index 41f0bbcf2..b79efb7fb 100644
--- a/frontends/nextjs/src/lib/middleware/auth-middleware.ts
+++ b/frontends/nextjs/src/lib/middleware/auth-middleware.ts
@@ -85,7 +85,7 @@ export async function authenticate(
     const user = await getCurrentUser()
 
     // Check if user is authenticated
-    if (user === null) {
+    if (user === null || user === undefined) {
       return {
         success: false,
         error: NextResponse.json(