fix(mcp-server): add graceful shutdown to prevent zombie processes (#477)

* fix(mcp-server): add graceful shutdown to prevent zombie processes

Add lifecycle handlers to properly exit the MCP server when the parent
application closes:

- Listen for stdin close/end events (primary method for all platforms)
- Handle SIGINT/SIGTERM signals
- Handle stdout broken pipe errors
- Export shutdown() function from http-server to clean up resources

* chore(mcp-server): bump version to 0.1.11

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

components/chat-panel.tsx

@@ -335,7 +335,10 @@ export default function ChatPanel({
                 }
 
                 // Translate image not supported error
-                if (friendlyMessage.includes("image content block")) {
+                if (
+                    friendlyMessage.includes("image content block") ||
+                    friendlyMessage.toLowerCase().includes("image_url")
+                ) {
                     friendlyMessage = "This model doesn't support image input."
                 }
 
@@ -902,7 +905,6 @@ export default function ChatPanel({
                     className="text-sm font-medium text-muted-foreground mt-8 tracking-wide"
                     style={{
                         writingMode: "vertical-rl",
-                        transform: "rotate(180deg)",
                     }}
                 >
                     {dict.nav.aiChat}

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
+}

package-lock.json

@@ -93,6 +93,11 @@
                 "typescript": "^5",
                 "wait-on": "^9.0.3",
                 "wrangler": "4.54.0"
+            },
+            "optionalDependencies": {
+                "@tailwindcss/oxide-linux-x64-gnu": "^4.1.18",
+                "lightningcss": "^1.30.2",
+                "lightningcss-linux-x64-gnu": "^1.30.2"
             }
         },
         "node_modules/@acemir/cssom": {
@@ -8714,6 +8719,22 @@
                 "node": ">= 10"
             }
         },
+        "node_modules/@tailwindcss/oxide-linux-x64-gnu": {
+            "version": "4.1.18",
+            "resolved": "https://registry.npmjs.org/@tailwindcss/oxide-linux-x64-gnu/-/oxide-linux-x64-gnu-4.1.18.tgz",
+            "integrity": "sha512-v3gyT0ivkfBLoZGF9LyHmts0Isc8jHZyVcbzio6Wpzifg/+5ZJpDiRiUhDLkcr7f/r38SWNe7ucxmGW3j3Kb/g==",
+            "cpu": [
+                "x64"
+            ],
+            "license": "MIT",
+            "optional": true,
+            "os": [
+                "linux"
+            ],
+            "engines": {
+                "node": ">= 10"
+            }
+        },
         "node_modules/@tailwindcss/postcss": {
             "version": "4.1.18",
             "resolved": "https://registry.npmjs.org/@tailwindcss/postcss/-/postcss-4.1.18.tgz",
@@ -15122,7 +15143,7 @@
             "version": "1.30.2",
             "resolved": "https://registry.npmjs.org/lightningcss/-/lightningcss-1.30.2.tgz",
             "integrity": "sha512-utfs7Pr5uJyyvDETitgsaqSyjCb2qNRAtuqUeWIAKztsOYdcACf2KtARYXg2pSvhkt+9NfoaNY7fxjl6nuMjIQ==",
-            "dev": true,
+            "devOptional": true,
             "license": "MPL-2.0",
             "dependencies": {
                 "detect-libc": "^2.0.3"
@@ -15155,7 +15176,6 @@
             "cpu": [
                 "arm64"
             ],
-            "dev": true,
             "license": "MPL-2.0",
             "optional": true,
             "os": [
@@ -15169,6 +15189,26 @@
                 "url": "https://opencollective.com/parcel"
             }
         },
+        "node_modules/lightningcss-linux-x64-gnu": {
+            "version": "1.30.2",
+            "resolved": "https://registry.npmjs.org/lightningcss-linux-x64-gnu/-/lightningcss-linux-x64-gnu-1.30.2.tgz",
+            "integrity": "sha512-Cfd46gdmj1vQ+lR6VRTTadNHu6ALuw2pKR9lYq4FnhvgBc4zWY1EtZcAc6EffShbb1MFrIPfLDXD6Xprbnni4w==",
+            "cpu": [
+                "x64"
+            ],
+            "license": "MPL-2.0",
+            "optional": true,
+            "os": [
+                "linux"
+            ],
+            "engines": {
+                "node": ">= 12.0.0"
+            },
+            "funding": {
+                "type": "opencollective",
+                "url": "https://opencollective.com/parcel"
+            }
+        },
         "node_modules/lint-staged": {
             "version": "16.2.7",
             "resolved": "https://registry.npmjs.org/lint-staged/-/lint-staged-16.2.7.tgz",
@@ -17972,9 +18012,9 @@
             }
         },
         "node_modules/qs": {
-            "version": "6.14.0",
+            "version": "6.14.1",
-            "resolved": "https://registry.npmjs.org/qs/-/qs-6.14.0.tgz",
+            "resolved": "https://registry.npmjs.org/qs/-/qs-6.14.1.tgz",
-            "integrity": "sha512-YWWTjgABSKcvs/nWBi9PycY/JiPJqOD4JA6o9Sej2AtvSGarXxKC3OQSk4pAarbdQlKAh5D4FCQkJNkW+GAn3w==",
+            "integrity": "sha512-4EK3+xJl8Ts67nLYNwqw/dsFVnCf+qR7RgXSK9jEEm9unao3njwMDdmsdvoKBKHzxd7tCYz5e5M+SnMjdtXGQQ==",
             "license": "BSD-3-Clause",
             "dependencies": {
                 "side-channel": "^1.1.0"

packages/mcp-server/package.json

@@ -1,6 +1,6 @@
 {
     "name": "@next-ai-drawio/mcp-server",
-    "version": "0.1.10",
+    "version": "0.1.11",
     "description": "MCP server for Next AI Draw.io - AI-powered diagram generation with real-time browser preview",
     "type": "module",
     "main": "dist/index.js",

packages/mcp-server/src/http-server.ts

@@ -127,7 +127,12 @@ function cleanupExpiredSessions(): void {
     }
 }
 
-setInterval(cleanupExpiredSessions, 5 * 60 * 1000)
+const cleanupIntervalId = setInterval(cleanupExpiredSessions, 5 * 60 * 1000)
+
+export function shutdown(): void {
+    clearInterval(cleanupIntervalId)
+    stopHttpServer()
+}
 
 export function getServerPort(): number {
     return serverPort

packages/mcp-server/src/index.ts

@@ -39,6 +39,7 @@ import {
     getState,
     requestSync,
     setState,
+    shutdown,
     startHttpServer,
     waitForSync,
 } from "./http-server.js"
@@ -618,6 +619,31 @@ server.registerTool(
     },
 )
 
+// Graceful shutdown handler
+let isShuttingDown = false
+function gracefulShutdown(reason: string) {
+    if (isShuttingDown) return
+    isShuttingDown = true
+    log.info(`Shutting down: ${reason}`)
+    shutdown()
+    process.exit(0)
+}
+
+// Handle stdin close (primary method - works on all platforms including Windows)
+process.stdin.on("close", () => gracefulShutdown("stdin closed"))
+process.stdin.on("end", () => gracefulShutdown("stdin ended"))
+
+// Handle signals (may not work reliably on Windows)
+process.on("SIGINT", () => gracefulShutdown("SIGINT"))
+process.on("SIGTERM", () => gracefulShutdown("SIGTERM"))
+
+// Handle broken pipe (writing to closed stdout)
+process.stdout.on("error", (err) => {
+    if (err.code === "EPIPE" || err.code === "ERR_STREAM_DESTROYED") {
+        gracefulShutdown("stdout error")
+    }
+})
+
 // Start the MCP server
 async function main() {
     log.info("Starting MCP server for Next AI Draw.io (embedded mode)...")