fix: harden persistence checks and export timeout

- Enable draw.io autosave and handle autosave events to update chartXML
- Clear modified state after autosave to avoid beforeunload prompts
- Disable confirmExit in draw.io configuration
- Set modified=false and keepmodified=false URL parameters
- Fix session save condition to also save when only diagram exists

app/[lang]/page.tsx

@@ -11,10 +11,16 @@ import {
 } from "@/components/ui/resizable"
 import { useDiagram } from "@/contexts/diagram-context"
 import { i18n, type Locale } from "@/lib/i18n/config"
+import { isIndexedDBUsable } from "@/lib/session-storage"
 
 export default function Home() {
-    const { drawioRef, handleDiagramExport, onDrawioLoad, resetDrawioReady } =
-        useDiagram()
+    const {
+        drawioRef,
+        handleDiagramExport,
+        handleDiagramAutoSave,
+        onDrawioLoad,
+        resetDrawioReady,
+    } = useDiagram()
     const router = useRouter()
     const pathname = usePathname()
     // Extract current language from pathname (e.g., "/zh/about" → "zh")
@@ -26,6 +32,7 @@ export default function Home() {
     const [isLoaded, setIsLoaded] = useState(false)
     const [isDrawioReady, setIsDrawioReady] = useState(false)
     const [isElectron, setIsElectron] = useState(false)
+    const [canPersist, setCanPersist] = useState(false)
     const [drawioBaseUrl, setDrawioBaseUrl] = useState(
         process.env.NEXT_PUBLIC_DRAWIO_BASE_URL || "https://embed.diagrams.net",
     )
@@ -76,6 +83,10 @@ export default function Home() {
             setDrawioBaseUrl(`${window.location.origin}/drawio/index.html`)
         }
 
+        void (async () => {
+            const usable = await isIndexedDBUsable()
+            setCanPersist(usable)
+        })()
         setIsLoaded(true)
     }, [pathname, router])
 
@@ -84,6 +95,17 @@ export default function Home() {
         onDrawioLoad()
     }, [onDrawioLoad])
 
+    const handleDrawioAutoSave = useCallback(
+        (data: { xml?: string }) => {
+            handleDiagramAutoSave(data)
+            // Only suppress modified state when persistence is available
+            if (canPersist) {
+                drawioRef.current?.status({ message: "", modified: false })
+            }
+        },
+        [canPersist, drawioRef, handleDiagramAutoSave],
+    )
+
     const handleDarkModeChange = () => {
         const newValue = !darkMode
         setDarkMode(newValue)
@@ -174,13 +196,25 @@ export default function Home() {
                                     <DrawIoEmbed
                                         key={`${drawioUi}-${darkMode}-${currentLang}-${isElectron}`}
                                         ref={drawioRef}
+                                        autosave
+                                        onAutoSave={handleDrawioAutoSave}
                                         onExport={handleDiagramExport}
                                         onLoad={handleDrawioLoad}
                                         baseUrl={drawioBaseUrl}
+                                        configuration={
+                                            canPersist
+                                                ? { confirmExit: false }
+                                                : undefined
+                                        }
                                         urlParameters={{
                                             ui: drawioUi,
                                             spin: false,
                                             libraries: false,
+                                            // Disable modified tracking only when persistence is available
+                                            ...(canPersist && {
+                                                modified: false,
+                                                keepmodified: false,
+                                            }),
                                             saveAndExit: false,
                                             noSaveBtn: true,
                                             noExitBtn: true,

components/chat-panel.tsx

@@ -137,26 +137,22 @@ export default function ChatPanel({
     const onFetchChart = (saveToHistory = true) => {
         return Promise.race([
             new Promise<string>((resolve) => {
-                if (resolverRef && "current" in resolverRef) {
-                    resolverRef.current = resolve
-                }
+                resolverRef.current = resolve
                 if (saveToHistory) {
                     onExport()
                 } else {
                     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)
+            }),
         ])
     }
 
@@ -585,7 +581,7 @@ export default function ChatPanel({
 
         try {
             const currentSession = sessionManager.currentSession
-            if (currentSession) {
+            if (currentSession && currentSession.messages.length > 0) {
                 // Restore from session manager (IndexedDB)
                 justLoadedSessionRef.current = true
                 syncUIWithSession(currentSession)
@@ -622,7 +618,7 @@ export default function ChatPanel({
         lastSyncedSessionIdRef.current = newSessionId
 
         // Sync UI with new session
-        if (newSession) {
+        if (newSession && newSession.messages.length > 0) {
             justLoadedSessionRef.current = true
             syncUIWithSession(newSession)
         } else if (!newSession) {
@@ -677,7 +673,7 @@ export default function ChatPanel({
         // Debounce: save after 1 second of no changes
         localStorageDebounceRef.current = setTimeout(async () => {
             try {
-                if (messages.length > 0) {
+                if (messages.length > 0 || hasDiagramNow) {
                     const sessionData = await buildSessionData({
                         // Only capture thumbnail if there was a diagram AND this isn't a no-diagram session
                         withThumbnail: hasDiagramNow && !isNodiagramSession,
@@ -699,6 +695,7 @@ export default function ChatPanel({
             }
         }
     }, [
+        chartXML,
         messages,
         status,
         sessionIsAvailable,
@@ -729,7 +726,8 @@ export default function ChatPanel({
         const handleVisibilityChange = async () => {
             if (
                 document.visibilityState === "hidden" &&
-                messagesRef.current.length > 0
+                (messagesRef.current.length > 0 ||
+                    isRealDiagram(chartXMLRef.current))
             ) {
                 try {
                     // Attempt to save session - browser may not wait for completion

contexts/diagram-context.tsx

@@ -20,9 +20,10 @@ interface DiagramContextType {
     loadDiagram: (chart: string, skipValidation?: boolean) => string | null
     handleExport: () => void
     handleExportWithoutHistory: () => void
-    resolverRef: React.Ref<((value: string) => void) | null>
-    drawioRef: React.Ref<DrawIoEmbedRef | null>
+    resolverRef: React.MutableRefObject<((value: string) => void) | null>
+    drawioRef: React.MutableRefObject<DrawIoEmbedRef | null>
     handleDiagramExport: (data: any) => void
+    handleDiagramAutoSave: (data: { xml?: string }) => void
     clearDiagram: () => void
     saveDiagramToFile: (
         filename: string,
@@ -267,6 +268,11 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
         }
     }
 
+    const handleDiagramAutoSave = (data: { xml?: string }) => {
+        if (!data?.xml) return
+        setChartXML(data.xml)
+    }
+
     const clearDiagram = () => {
         const emptyDiagram = `<mxfile><diagram name="Page-1" id="page-1"><mxGraphModel><root><mxCell id="0"/><mxCell id="1" parent="0"/></root></mxGraphModel></diagram></mxfile>`
         // Skip validation for trusted internal template (loadDiagram also sets chartXML)
@@ -391,6 +397,7 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
                 resolverRef,
                 drawioRef,
                 handleDiagramExport,
+                handleDiagramAutoSave,
                 clearDiagram,
                 saveDiagramToFile,
                 getThumbnailSvg,

lib/session-storage.ts

@@ -47,33 +47,6 @@ interface ChatSessionDB extends DBSchema {
 
 // Database singleton
 let dbPromise: Promise<IDBPDatabase<ChatSessionDB>> | null = null
-const resetDBPromise = () => {
-    dbPromise = null
-}
-
-const isClosingError = (error: unknown): boolean => {
-    return (
-        error instanceof DOMException &&
-        error.name === "InvalidStateError" &&
-        /closing/i.test(error.message)
-    )
-}
-
-const withDB = async <T>(
-    action: (db: IDBPDatabase<ChatSessionDB>) => Promise<T>,
-): Promise<T> => {
-    try {
-        const db = await getDB()
-        return await action(db)
-    } catch (error) {
-        if (isClosingError(error)) {
-            resetDBPromise()
-            const db = await getDB()
-            return await action(db)
-        }
-        throw error
-    }
-}
 
 async function getDB(): Promise<IDBPDatabase<ChatSessionDB>> {
     if (!dbPromise) {
@@ -87,23 +60,7 @@ async function getDB(): Promise<IDBPDatabase<ChatSessionDB>> {
                 }
                 // Future migrations: if (oldVersion < 2) { ... }
             },
-            terminated() {
-                resetDBPromise()
-            },
         })
-        dbPromise
-            .then((db) => {
-                db.onversionchange = () => {
-                    db.close()
-                    resetDBPromise()
-                }
-                db.onclose = () => {
-                    resetDBPromise()
-                }
-            })
-            .catch(() => {
-                resetDBPromise()
-            })
     }
     return dbPromise
 }
@@ -118,33 +75,43 @@ 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 []
     try {
-        return await withDB(async (db) => {
-            const tx = db.transaction(STORE_NAME, "readonly")
-            const index = tx.store.index("by-updated")
-            const metadata: SessionMetadata[] = []
+        const db = await getDB()
+        const tx = db.transaction(STORE_NAME, "readonly")
+        const index = tx.store.index("by-updated")
+        const metadata: SessionMetadata[] = []
 
-            // Use cursor to read only metadata fields (avoids loading full messages/XML)
-            let cursor = await index.openCursor(null, "prev") // newest first
-            while (cursor) {
-                const s = cursor.value
-                metadata.push({
-                    id: s.id,
-                    title: s.title,
-                    createdAt: s.createdAt,
-                    updatedAt: s.updatedAt,
-                    messageCount: s.messages.length,
-                    hasDiagram:
-                        !!s.diagramXml && s.diagramXml.trim().length > 0,
-                    thumbnailDataUrl: s.thumbnailDataUrl,
-                })
-                cursor = await cursor.continue()
-            }
-            return metadata
-        })
+        // Use cursor to read only metadata fields (avoids loading full messages/XML)
+        let cursor = await index.openCursor(null, "prev") // newest first
+        while (cursor) {
+            const s = cursor.value
+            metadata.push({
+                id: s.id,
+                title: s.title,
+                createdAt: s.createdAt,
+                updatedAt: s.updatedAt,
+                messageCount: s.messages.length,
+                hasDiagram: !!s.diagramXml && s.diagramXml.trim().length > 0,
+                thumbnailDataUrl: s.thumbnailDataUrl,
+            })
+            cursor = await cursor.continue()
+        }
+        return metadata
     } catch (error) {
         console.error("Failed to get session metadata:", error)
         return []
@@ -154,9 +121,8 @@ export async function getAllSessionMetadata(): Promise<SessionMetadata[]> {
 export async function getSession(id: string): Promise<ChatSession | null> {
     if (!isIndexedDBAvailable()) return null
     try {
-        return await withDB(async (db) => {
-            return (await db.get(STORE_NAME, id)) || null
-        })
+        const db = await getDB()
+        return (await db.get(STORE_NAME, id)) || null
     } catch (error) {
         console.error("Failed to get session:", error)
         return null
@@ -166,9 +132,8 @@ export async function getSession(id: string): Promise<ChatSession | null> {
 export async function saveSession(session: ChatSession): Promise<boolean> {
     if (!isIndexedDBAvailable()) return false
     try {
-        await withDB(async (db) => {
-            await db.put(STORE_NAME, session)
-        })
+        const db = await getDB()
+        await db.put(STORE_NAME, session)
         return true
     } catch (error) {
         // Handle quota exceeded
@@ -180,9 +145,8 @@ export async function saveSession(session: ChatSession): Promise<boolean> {
             await deleteOldestSession()
             // Retry once
             try {
-                await withDB(async (db) => {
-                    await db.put(STORE_NAME, session)
-                })
+                const db = await getDB()
+                await db.put(STORE_NAME, session)
                 return true
             } catch (retryError) {
                 console.error(
@@ -201,9 +165,8 @@ export async function saveSession(session: ChatSession): Promise<boolean> {
 export async function deleteSession(id: string): Promise<void> {
     if (!isIndexedDBAvailable()) return
     try {
-        await withDB(async (db) => {
-            await db.delete(STORE_NAME, id)
-        })
+        const db = await getDB()
+        await db.delete(STORE_NAME, id)
     } catch (error) {
         console.error("Failed to delete session:", error)
     }
@@ -212,9 +175,8 @@ export async function deleteSession(id: string): Promise<void> {
 export async function getSessionCount(): Promise<number> {
     if (!isIndexedDBAvailable()) return 0
     try {
-        return await withDB(async (db) => {
-            return await db.count(STORE_NAME)
-        })
+        const db = await getDB()
+        return await db.count(STORE_NAME)
     } catch (error) {
         console.error("Failed to get session count:", error)
         return 0
@@ -224,15 +186,14 @@ export async function getSessionCount(): Promise<number> {
 export async function deleteOldestSession(): Promise<void> {
     if (!isIndexedDBAvailable()) return
     try {
-        await withDB(async (db) => {
-            const tx = db.transaction(STORE_NAME, "readwrite")
-            const index = tx.store.index("by-updated")
-            const cursor = await index.openCursor()
-            if (cursor) {
-                await cursor.delete()
-            }
-            await tx.done
-        })
+        const db = await getDB()
+        const tx = db.transaction(STORE_NAME, "readwrite")
+        const index = tx.store.index("by-updated")
+        const cursor = await index.openCursor()
+        if (cursor) {
+            await cursor.delete()
+        }
+        await tx.done
     } catch (error) {
         console.error("Failed to delete oldest session:", error)
     }

lib/system-prompts.ts

@@ -11,7 +11,6 @@ export const DEFAULT_SYSTEM_PROMPT = `
 You are an expert diagram creation assistant specializing in draw.io XML generation.
 Your primary function is chat with user and crafting clear, well-organized visual diagrams through precise XML specifications.
 You can see images that users upload, and you can read the text content extracted from PDF documents they upload.
-ALWAYS respond in the same language as the user's last message.
 
 When you are asked to create a diagram, briefly describe your plan about the layout and structure to avoid object overlapping or edge cross the objects. (2-3 sentences max), then use display_diagram tool to generate the XML.
 After generating or editing a diagram, you don't need to say anything. The user can see the diagram - no need to describe it.