fix: save session when diagram is modified via autosave

Add chartXML to dependency array of auto-save effect so that user
modifications in draw.io (captured via autosave) trigger session save.

app/[lang]/page.tsx

@@ -16,8 +16,13 @@ const drawioBaseUrl =
     process.env.NEXT_PUBLIC_DRAWIO_BASE_URL || "https://embed.diagrams.net"
 
 export default function Home() {
-    const { drawioRef, handleDiagramExport, onDrawioLoad, resetDrawioReady } =
-        useDiagram()
+    const {
+        drawioRef,
+        handleDiagramExport,
+        handleAutoSave,
+        onDrawioLoad,
+        resetDrawioReady,
+    } = useDiagram()
     const router = useRouter()
     const pathname = usePathname()
     // Extract current language from pathname (e.g., "/zh/about" → "zh")
@@ -164,6 +169,8 @@ export default function Home() {
                                         ref={drawioRef}
                                         onExport={handleDiagramExport}
                                         onLoad={handleDrawioLoad}
+                                        onAutoSave={handleAutoSave}
+                                        autosave={true}
                                         baseUrl={drawioBaseUrl}
                                         urlParameters={{
                                             ui: drawioUi,
@@ -172,6 +179,7 @@ export default function Home() {
                                             saveAndExit: false,
                                             noSaveBtn: true,
                                             noExitBtn: true,
+                                            modified: false,
                                             dark: darkMode,
                                             lang: currentLang,
                                         }}

components/chat-panel.tsx

@@ -639,6 +639,7 @@ export default function ChatPanel({
         sessionIsAvailable,
         currentSessionId,
         buildSessionData,
+        chartXML,
     ])
 
     // Update URL when a new session is created (first message sent)

contexts/diagram-context.tsx

@@ -2,7 +2,7 @@
 
 import type React from "react"
 import { createContext, useContext, useEffect, useRef, useState } from "react"
-import type { DrawIoEmbedRef } from "react-drawio"
+import type { DrawIoEmbedRef, EventAutoSave } from "react-drawio"
 import { toast } from "sonner"
 import type { ExportFormat } from "@/components/save-dialog"
 import { getApiEndpoint } from "@/lib/base-path"
@@ -23,6 +23,7 @@ interface DiagramContextType {
     resolverRef: React.Ref<((value: string) => void) | null>
     drawioRef: React.Ref<DrawIoEmbedRef | null>
     handleDiagramExport: (data: any) => void
+    handleAutoSave: (data: EventAutoSave) => void
     clearDiagram: () => void
     saveDiagramToFile: (
         filename: string,
@@ -226,6 +227,13 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
         }
     }
 
+    // Handle autosave events from draw.io - keeps chartXML in sync with user modifications
+    const handleAutoSave = (data: EventAutoSave) => {
+        if (data.xml) {
+            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)
@@ -350,6 +358,7 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
                 resolverRef,
                 drawioRef,
                 handleDiagramExport,
+                handleAutoSave,
                 clearDiagram,
                 saveDiagramToFile,
                 getThumbnailSvg,