fix: harden persistence checks and export timeout

app/[lang]/page.tsx

@@ -11,7 +11,7 @@ import {
 } from "@/components/ui/resizable"
 import { useDiagram } from "@/contexts/diagram-context"
 import { i18n, type Locale } from "@/lib/i18n/config"
-import { isIndexedDBAvailable } from "@/lib/session-storage"
+import { isIndexedDBUsable } from "@/lib/session-storage"
 
 export default function Home() {
     const {
@@ -83,7 +83,10 @@ export default function Home() {
             setDrawioBaseUrl(`${window.location.origin}/drawio/index.html`)
         }
 
-        setCanPersist(isIndexedDBAvailable())
+        void (async () => {
+            const usable = await isIndexedDBUsable()
+            setCanPersist(usable)
+        })()
         setIsLoaded(true)
     }, [pathname, router])
 

components/chat-panel.tsx

@@ -144,17 +144,15 @@ export default function ChatPanel({
                     handleExportWithoutHistory()
                 }
             }),
-            new Promise<string>((_, reject) =>
-                setTimeout(
-                    () =>
-                        reject(
-                            new Error(
-                                "Chart export timed out after 10 seconds",
-                            ),
-                        ),
-                    10000,
-                ),
-            ),
+            new Promise<string>((_, reject) => {
+                const currentResolver = resolverRef.current
+                setTimeout(() => {
+                    if (resolverRef.current === currentResolver) {
+                        resolverRef.current = null
+                    }
+                    reject(new Error("Chart export timed out after 10 seconds"))
+                }, 10000)
+            }),
         ])
     }
 

lib/session-storage.ts

@@ -75,6 +75,18 @@ export function isIndexedDBAvailable(): boolean {
     }
 }
 
+// Check if IndexedDB is actually usable (not just present).
+export async function isIndexedDBUsable(): Promise<boolean> {
+    if (!isIndexedDBAvailable()) return false
+    try {
+        const db = await getDB()
+        db.close()
+        return true
+    } catch {
+        return false
+    }
+}
+
 // CRUD Operations
 export async function getAllSessionMetadata(): Promise<SessionMetadata[]> {
     if (!isIndexedDBAvailable()) return []