diff --git a/frontends/nextjs/src/hooks/auth/auth-store.ts b/frontends/nextjs/src/hooks/auth/auth-store.ts
index f5735edd4..fa98e0c09 100644
--- a/frontends/nextjs/src/hooks/auth/auth-store.ts
+++ b/frontends/nextjs/src/hooks/auth/auth-store.ts
@@ -38,7 +38,7 @@ export class AuthStore {
   }
 
   async ensureSessionChecked(): Promise<void> {
-    if (!this.sessionCheckPromise) {
+    if (this.sessionCheckPromise === null) {
       this.sessionCheckPromise = this.refresh().finally(() => {
         this.sessionCheckPromise = null
       })
@@ -129,6 +129,7 @@ export class AuthStore {
         isAuthenticated: false,
         isLoading: false,
       })
+      console.error('Failed to refresh session', error)
     }
   }
 }
diff --git a/frontends/nextjs/src/hooks/ui/state/__tests__/useAutoRefresh.polling.test.ts b/frontends/nextjs/src/hooks/ui/state/__tests__/useAutoRefresh.polling.test.ts
index 8c080d454..95e1b29d9 100644
--- a/frontends/nextjs/src/hooks/ui/state/__tests__/useAutoRefresh.polling.test.ts
+++ b/frontends/nextjs/src/hooks/ui/state/__tests__/useAutoRefresh.polling.test.ts
@@ -1,7 +1,7 @@
 /**
  * Auto-refresh polling tests
  */
-import { act, renderHook, waitFor } from '@testing-library/react'
+import { act, renderHook } from '@testing-library/react'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 
 import { useAutoRefresh } from '../useAutoRefresh'
diff --git a/frontends/nextjs/src/hooks/ui/state/useAutoRefresh.ts b/frontends/nextjs/src/hooks/ui/state/useAutoRefresh.ts
index 265bcd35c..3ca452ffe 100644
--- a/frontends/nextjs/src/hooks/ui/state/useAutoRefresh.ts
+++ b/frontends/nextjs/src/hooks/ui/state/useAutoRefresh.ts
@@ -34,7 +34,7 @@ export function useAutoRefresh({
     if (!isAutoRefreshing) return
 
     const refreshInterval = setInterval(() => {
-      onRefresh()
+      void onRefresh()
     }, intervalMs)
 
     const countdownInterval = setInterval(() => {
diff --git a/frontends/nextjs/src/hooks/ui/useFileTree.ts b/frontends/nextjs/src/hooks/ui/useFileTree.ts
index 67a6a920b..fd15dde78 100644
--- a/frontends/nextjs/src/hooks/ui/useFileTree.ts
+++ b/frontends/nextjs/src/hooks/ui/useFileTree.ts
@@ -19,8 +19,10 @@ export function useFileTree(initialFiles: FileNode[] = []) {
   const [files, setFiles] = useState<FileNode[]>(initialFiles)
 
   const findNodeById = useCallback(
-    (id: string, nodes = files): FileNode | null => {
-      for (const node of nodes) {
+    (id: string, nodes?: FileNode[]): FileNode | null => {
+      const searchNodes = nodes ?? files
+
+      for (const node of searchNodes) {
         if (node.id === id) return node
         if (node.children) {
           const found = findNodeById(id, node.children)
@@ -69,32 +71,29 @@ export function useFileTree(initialFiles: FileNode[] = []) {
 
   const addChild = useCallback(
     (parentId: string, child: FileNode) => {
-      const parent = findNodeById(parentId)
-      if (!parent || parent.type !== 'folder') return
+      setFiles(currentFiles => {
+        const parent = findNodeById(parentId, currentFiles)
+        if (!parent || parent.type !== 'folder') return currentFiles
 
-      setFiles(files =>
-        files.map(node => {
-          if (node.id === parentId) {
-            return {
-              ...node,
-              children: [...(node.children || []), child],
+        const appendChild = (nodes: FileNode[]): FileNode[] =>
+          nodes.map(node => {
+            if (node.id === parentId && node.type === 'folder') {
+              return {
+                ...node,
+                children: [...(node.children || []), child],
+              }
             }
-          }
-          if (node.children) {
-            return {
-              ...node,
-              children:
-                files.map(n =>
-                  n.id === parentId ? { ...n, children: [...(n.children || []), child] } : n
-                )[0]?.children || node.children,
+            if (node.children) {
+              return { ...node, children: appendChild(node.children) }
             }
-          }
-          return node
-        })
-      )
+            return node
+          })
+
+        return appendChild(currentFiles)
+      })
       toast.success('Created')
     },
-    [findNodeById, files]
+    [findNodeById]
   )
 
   return {
diff --git a/frontends/nextjs/src/hooks/use-dbal/use-cached-data.ts b/frontends/nextjs/src/hooks/use-dbal/use-cached-data.ts
index ee002fb13..5494c0308 100644
--- a/frontends/nextjs/src/hooks/use-dbal/use-cached-data.ts
+++ b/frontends/nextjs/src/hooks/use-dbal/use-cached-data.ts
@@ -8,18 +8,18 @@ import { useKVStore } from './use-kv-store'
  * Hook for storing and retrieving cached data with automatic serialization
  */
 export function useCachedData<T>(key: string, tenantId?: string, userId?: string) {
-  const kv = useKVStore(tenantId, userId)
+  const { isReady, get, set, delete: deleteKey } = useKVStore(tenantId, userId)
   const [data, setData] = useState<T | null>(null)
   const [loading, setLoading] = useState(true)
   const [error, setError] = useState<string | null>(null)
 
   useEffect(() => {
     const loadData = async () => {
-      if (!kv.isReady) return
+      if (!isReady) return
 
       try {
         setLoading(true)
-        const cached = await kv.get<T>(key)
+        const cached = await get<T>(key)
         setData(cached)
         setError(null)
       } catch (err) {
@@ -30,13 +30,13 @@ export function useCachedData<T>(key: string, tenantId?: string, userId?: string
       }
     }
 
-    loadData()
-  }, [key, kv.isReady])
+    void loadData()
+  }, [get, isReady, key])
 
   const save = useCallback(
     async (newData: T, ttl?: number) => {
       try {
-        await kv.set(key, newData, ttl)
+        await set(key, newData, ttl)
         setData(newData)
         setError(null)
       } catch (err) {
@@ -45,12 +45,12 @@ export function useCachedData<T>(key: string, tenantId?: string, userId?: string
         throw err
       }
     },
-    [key, kv]
+    [key, set]
   )
 
   const clear = useCallback(async () => {
     try {
-      await kv.delete(key)
+      await deleteKey(key)
       setData(null)
       setError(null)
     } catch (err) {
@@ -58,7 +58,7 @@ export function useCachedData<T>(key: string, tenantId?: string, userId?: string
       setError(errorInfo.message)
       throw err
     }
-  }, [key, kv])
+  }, [deleteKey, key])
 
   return {
     data,
@@ -66,6 +66,6 @@ export function useCachedData<T>(key: string, tenantId?: string, userId?: string
     error,
     save,
     clear,
-    isReady: kv.isReady,
+    isReady,
   }
 }
diff --git a/frontends/nextjs/src/hooks/use-dbal/use-dbal.ts b/frontends/nextjs/src/hooks/use-dbal/use-dbal.ts
index 059ca6870..f59c76824 100644
--- a/frontends/nextjs/src/hooks/use-dbal/use-dbal.ts
+++ b/frontends/nextjs/src/hooks/use-dbal/use-dbal.ts
@@ -23,7 +23,7 @@ export function useDBAL() {
       }
     }
 
-    init()
+    void init()
   }, [])
 
   return { isReady, error }
diff --git a/frontends/nextjs/src/hooks/use-dbal/use-kv-store.ts b/frontends/nextjs/src/hooks/use-dbal/use-kv-store.ts
index 60caf97f3..1657420a5 100644
--- a/frontends/nextjs/src/hooks/use-dbal/use-kv-store.ts
+++ b/frontends/nextjs/src/hooks/use-dbal/use-kv-store.ts
@@ -12,7 +12,7 @@ export function useKVStore(tenantId: string = 'default', userId: string = 'syste
   const { isReady } = useDBAL()
 
   const set = useCallback(
-    async (key: string, value: any, ttl?: number) => {
+    async (key: string, value: unknown, ttl?: number) => {
       if (!isReady) {
         throw new Error('DBAL not ready')
       }
@@ -28,7 +28,7 @@ export function useKVStore(tenantId: string = 'default', userId: string = 'syste
   )
 
   const get = useCallback(
-    async <T = any>(key: string): Promise<T | null> => {
+    async <T = unknown>(key: string): Promise<T | null> => {
       if (!isReady) {
         throw new Error('DBAL not ready')
       }
@@ -60,7 +60,7 @@ export function useKVStore(tenantId: string = 'default', userId: string = 'syste
   )
 
   const listAdd = useCallback(
-    async (key: string, items: any[]) => {
+    async <T = unknown>(key: string, items: T[]) => {
       if (!isReady) {
         throw new Error('DBAL not ready')
       }
@@ -76,7 +76,7 @@ export function useKVStore(tenantId: string = 'default', userId: string = 'syste
   )
 
   const listGet = useCallback(
-    async (key: string, start?: number, end?: number): Promise<any[]> => {
+    async <T = unknown>(key: string, start?: number, end?: number): Promise<T[]> => {
       if (!isReady) {
         throw new Error('DBAL not ready')
       }