fix(deps): update dependency zod to v4

Some models (Kimi K2, DeepSeek, Qwen text models) don't support image/vision
input. The AI SDK silently drops unsupported image parts, causing confusing
responses where the model acts as if no image was uploaded.

Added supportsImageInput() function to detect unsupported models by name,
and return a 400 error with clear guidance when users try to upload images
to these models.

Closes #469

app/[lang]/page.tsx

@@ -28,6 +28,8 @@ export default function Home() {
     } = useDiagram()
     const router = useRouter()
     const pathname = usePathname()
+    // Extract current language from pathname (e.g., "/zh/about" → "zh")
+    const currentLang = (pathname.split("/")[1] || i18n.defaultLocale) as Locale
     const [isMobile, setIsMobile] = useState(false)
     const [isChatVisible, setIsChatVisible] = useState(true)
     const [drawioUi, setDrawioUi] = useState<"min" | "sketch">("min")
@@ -207,7 +209,7 @@ export default function Home() {
                         <div className="h-full rounded-xl overflow-hidden shadow-soft-lg border border-border/30">
                             {isLoaded ? (
                                 <DrawIoEmbed
-                                    key={`${drawioUi}-${darkMode}`}
+                                    key={`${drawioUi}-${darkMode}-${currentLang}`}
                                     ref={drawioRef}
                                     onExport={handleDiagramExport}
                                     onLoad={onDrawioLoad}
@@ -220,6 +222,7 @@ export default function Home() {
                                         saveAndExit: false,
                                         noExitBtn: true,
                                         dark: darkMode,
+                                        lang: currentLang,
                                     }}
                                 />
                             ) : (

app/api/chat/route.ts

@@ -12,7 +12,11 @@ import fs from "fs/promises"
 import { jsonrepair } from "jsonrepair"
 import path from "path"
 import { z } from "zod"
-import { getAIModel, supportsPromptCaching } from "@/lib/ai-providers"
+import {
+    getAIModel,
+    supportsImageInput,
+    supportsPromptCaching,
+} from "@/lib/ai-providers"
 import { findCachedResponse } from "@/lib/cached-responses"
 import {
     checkAndIncrementRequest,
@@ -295,6 +299,17 @@ async function handleChatRequest(req: Request): Promise<Response> {
         lastUserMessage?.parts?.filter((part: any) => part.type === "file") ||
         []
 
+    // Check if user is sending images to a model that doesn't support them
+    // AI SDK silently drops unsupported parts, so we need to catch this early
+    if (fileParts.length > 0 && !supportsImageInput(modelId)) {
+        return Response.json(
+            {
+                error: `The model "${modelId}" does not support image input. Please use a vision-capable model (e.g., GPT-4o, Claude, Gemini) or remove the image.`,
+            },
+            { status: 400 },
+        )
+    }
+
     // User input only - XML is now in a separate cached system message
     const formattedUserInput = `User input:
 """md

lib/ai-providers.ts

@@ -906,3 +906,34 @@ export function supportsPromptCaching(modelId: string): boolean {
         modelId.startsWith("eu.anthropic")
     )
 }
+
+/**
+ * Check if a model supports image/vision input.
+ * Some models silently drop image parts without error (AI SDK warning only).
+ */
+export function supportsImageInput(modelId: string): boolean {
+    const lowerModelId = modelId.toLowerCase()
+
+    // Helper to check if model has vision capability indicator
+    const hasVisionIndicator =
+        lowerModelId.includes("vision") || lowerModelId.includes("vl")
+
+    // Models that DON'T support image/vision input (unless vision variant)
+    // Kimi K2 models don't support images
+    if (lowerModelId.includes("kimi") && !hasVisionIndicator) {
+        return false
+    }
+
+    // DeepSeek text models (not vision variants)
+    if (lowerModelId.includes("deepseek") && !hasVisionIndicator) {
+        return false
+    }
+
+    // Qwen text models (not vision variants like qwen-vl)
+    if (lowerModelId.includes("qwen") && !hasVisionIndicator) {
+        return false
+    }
+
+    // Default: assume model supports images
+    return true
+}

packages/mcp-server/package-lock.json

@@ -1,18 +1,18 @@
 {
     "name": "@next-ai-drawio/mcp-server",
-    "version": "0.1.6",
+    "version": "0.1.10",
     "lockfileVersion": 3,
     "requires": true,
     "packages": {
         "": {
             "name": "@next-ai-drawio/mcp-server",
-            "version": "0.1.6",
+            "version": "0.1.10",
             "license": "Apache-2.0",
             "dependencies": {
                 "@modelcontextprotocol/sdk": "^1.0.4",
                 "linkedom": "^0.18.0",
                 "open": "^11.0.0",
-                "zod": "^3.24.0"
+                "zod": "^4.0.0"
             },
             "bin": {
                 "next-ai-drawio-mcp": "dist/index.js"
@@ -2051,9 +2051,9 @@
             }
         },
         "node_modules/zod": {
-            "version": "3.25.76",
-            "resolved": "https://registry.npmjs.org/zod/-/zod-3.25.76.tgz",
-            "integrity": "sha512-gzUt/qt81nXsFGKIFcC3YnfEAx5NkunCfnDlvuBSSFS02bcXu4Lmea0AFIUwbLWxWPx3d9p8S5QoaujKcNQxcQ==",
+            "version": "4.3.2",
+            "resolved": "https://registry.npmjs.org/zod/-/zod-4.3.2.tgz",
+            "integrity": "sha512-b8L8yn4rIVfiXyHAmnr52/ZEpDumlT0bmxiq3Ws1ybrinhflGpt12Hvv54kYnEsGPRs6o/Ka3/ppA2OWY21IVg==",
             "license": "MIT",
             "peer": true,
             "funding": {

packages/mcp-server/package.json

@@ -39,7 +39,7 @@
         "@modelcontextprotocol/sdk": "^1.0.4",
         "linkedom": "^0.18.0",
         "open": "^11.0.0",
-        "zod": "^3.24.0"
+        "zod": "^4.0.0"
     },
     "devDependencies": {
         "@types/node": "^24.0.0",