fix: add confirmation dialog to prevent accidental back navigation

Addresses conflict between right-click drag and browser back gesture in
Chromium-based browsers. Shows browser confirmation dialog when user
tries to navigate away, preventing accidental page exits.

Closes #80

amplify.yml

@@ -0,0 +1,22 @@
+version: 1
+frontend:
+  phases:
+    preBuild:
+      commands:
+        - npm ci --cache .npm --prefer-offline
+    build:
+      commands:
+        # Write env vars to .env.production for Next.js SSR runtime
+        - env | grep -e AI_MODEL >> .env.production
+        - env | grep -e AI_PROVIDER >> .env.production
+        - env | grep -e OPENAI_API_KEY >> .env.production
+        - env | grep -e NEXT_PUBLIC_ >> .env.production
+        - npm run build
+  artifacts:
+    baseDirectory: .next
+    files:
+      - '**/*'
+  cache:
+    paths:
+      - .next/cache/**/*
+      - .npm/**/*

app/api/chat/route.ts

@@ -154,9 +154,28 @@ ${lastMessageText}
     messages: allMessages,
     ...(providerOptions && { providerOptions }),
     ...(headers && { headers }),
-    onFinish: ({ usage, providerMetadata }) => {
-      console.log('[Cache] Full providerMetadata:', JSON.stringify(providerMetadata, null, 2));
-      console.log('[Cache] Usage:', JSON.stringify(usage, null, 2));
+    onFinish: ({ usage, providerMetadata, finishReason, text, toolCalls }) => {
+      // Detect potential mid-stream failures (e.g., Bedrock 503 ServiceUnavailableException)
+      // When this happens, usage is empty and providerMetadata is undefined
+      const hasUsage = usage && Object.keys(usage).length > 0;
+      if (!hasUsage) {
+        console.error('[Stream Error] Empty usage detected - possible Bedrock 503 or mid-stream failure');
+        console.error('[Stream Error] finishReason:', finishReason);
+        console.error('[Stream Error] text received:', text?.substring(0, 200) || '(none)');
+        console.error('[Stream Error] toolCalls:', toolCalls?.length || 0);
+        // Log the user's last message for debugging
+        const lastUserMsg = enhancedMessages.filter(m => m.role === 'user').pop();
+        if (lastUserMsg) {
+          const content = lastUserMsg.content;
+          const preview = Array.isArray(content)
+            ? (content.find((c) => c.type === 'text') as { type: 'text'; text: string } | undefined)?.text?.substring(0, 100)
+            : String(content).substring(0, 100);
+          console.error('[Stream Error] Last user message preview:', preview);
+        }
+      } else {
+        console.log('[Cache] Full providerMetadata:', JSON.stringify(providerMetadata, null, 2));
+        console.log('[Cache] Usage:', JSON.stringify(usage, null, 2));
+      }
     },
     tools: {
       // Client-side tool that will be executed on the client
@@ -232,6 +251,23 @@ IMPORTANT: Keep edits concise:
         ? error.message
         : JSON.stringify(error);
 
+    // Check for Bedrock service errors (503, throttling, etc.)
+    if (errorString.includes('ServiceUnavailable') ||
+      errorString.includes('503') ||
+      errorString.includes('temporarily unavailable')) {
+      console.error('[Bedrock Error] ServiceUnavailableException:', errorString);
+      return 'The AI service is temporarily unavailable. Please try again in a few seconds.';
+    }
+
+    // Check for throttling errors
+    if (errorString.includes('ThrottlingException') ||
+      errorString.includes('rate limit') ||
+      errorString.includes('too many requests') ||
+      errorString.includes('429')) {
+      console.error('[Bedrock Error] ThrottlingException:', errorString);
+      return 'Too many requests. Please wait a moment and try again.';
+    }
+
     // Check for image not supported error (e.g., DeepSeek models)
     if (errorString.includes('image_url') ||
       errorString.includes('unknown variant') ||

app/page.tsx

@@ -32,6 +32,18 @@ export default function Home() {
         return () => window.removeEventListener('keydown', handleKeyDown);
     }, []);
 
+    // Show confirmation dialog when user tries to leave the page
+    // This helps prevent accidental navigation from browser back gestures
+    useEffect(() => {
+        const handleBeforeUnload = (event: BeforeUnloadEvent) => {
+            event.preventDefault();
+            return '';
+        };
+
+        window.addEventListener('beforeunload', handleBeforeUnload);
+        return () => window.removeEventListener('beforeunload', handleBeforeUnload);
+    }, []);
+
     return (
         <div className="flex h-screen bg-background relative overflow-hidden">
             {/* Mobile warning overlay */}

components/button-with-tooltip.tsx

@@ -27,7 +27,7 @@ export function ButtonWithTooltip({
                 <TooltipTrigger asChild>
                     <Button {...buttonProps}>{children}</Button>
                 </TooltipTrigger>
-                <TooltipContent>{tooltipContent}</TooltipContent>
+                <TooltipContent className="max-w-xs text-wrap">{tooltipContent}</TooltipContent>
             </Tooltip>
         </TooltipProvider>
     );

components/chat-example-panel.tsx

@@ -90,7 +90,10 @@ export default function ExamplePanel({
                         icon={<Zap className="w-4 h-4 text-primary" />}
                         title="Animated Diagram"
                         description="Draw a transformer architecture with animated connectors"
-                        onClick={() => setInput("Give me a **animated connector** diagram of transformer's architecture")}
+                        onClick={() => {
+                            setInput("Give me a **animated connector** diagram of transformer's architecture")
+                            setFiles([])
+                        }}
                     />
 
                     <ExampleCard
@@ -111,7 +114,10 @@ export default function ExamplePanel({
                         icon={<Palette className="w-4 h-4 text-primary" />}
                         title="Creative Drawing"
                         description="Draw something fun and creative"
-                        onClick={() => setInput("Draw a cat for me")}
+                        onClick={() => {
+                            setInput("Draw a cat for me")
+                            setFiles([])
+                        }}
                     />
                 </div>
 

components/chat-input.tsx

@@ -29,6 +29,7 @@ interface ChatInputProps {
     onFileChange?: (files: File[]) => void;
     showHistory?: boolean;
     onToggleHistory?: (show: boolean) => void;
+    error?: Error | null;
 }
 
 export function ChatInput({
@@ -41,6 +42,7 @@ export function ChatInput({
     onFileChange = () => {},
     showHistory = false,
     onToggleHistory = () => {},
+    error = null,
 }: ChatInputProps) {
     const { diagramHistory, saveDiagramToFile } = useDiagram();
     const textareaRef = useRef<HTMLTextAreaElement>(null);
@@ -49,7 +51,8 @@ export function ChatInput({
     const [showClearDialog, setShowClearDialog] = useState(false);
     const [showSaveDialog, setShowSaveDialog] = useState(false);
 
-    const isDisabled = status === "streaming" || status === "submitted";
+    // Allow retry when there's an error (even if status is still "streaming" or "submitted")
+    const isDisabled = (status === "streaming" || status === "submitted") && !error;
 
     useEffect(() => {
         console.log('[ChatInput] Status changed to:', status, '| Input disabled:', isDisabled);

components/chat-message-display.tsx

@@ -115,7 +115,7 @@ export function ChatMessageDisplay({
                     previousXML.current = convertedXml;
                     onDisplayChart(replacedXML);
                 } else {
-                    console.error("[ChatMessageDisplay] XML validation failed:", validationError);
+                    console.log("[ChatMessageDisplay] XML validation failed:", validationError);
                 }
             }
         },

components/chat-panel.tsx

@@ -4,7 +4,7 @@ import type React from "react";
 import { useRef, useEffect, useState } from "react";
 import { flushSync } from "react-dom";
 import { FaGithub } from "react-icons/fa";
-import { PanelRightClose, PanelRightOpen } from "lucide-react";
+import { PanelRightClose, PanelRightOpen, CheckCircle } from "lucide-react";
 import Link from "next/link";
 import Image from "next/image";
 
@@ -61,6 +61,7 @@ export default function ChatPanel({
     const [files, setFiles] = useState<File[]>([]);
     const [showHistory, setShowHistory] = useState(false);
     const [input, setInput] = useState("");
+    const [streamingError, setStreamingError] = useState<Error | null>(null);
 
     // Store XML snapshots for each user message (keyed by message index)
     const xmlSnapshotsRef = useRef<Map<number, string>>(new Map());
@@ -71,75 +72,88 @@ export default function ChatPanel({
         chartXMLRef.current = chartXML;
     }, [chartXML]);
 
-    const { messages, sendMessage, addToolResult, status, error, setMessages } =
-        useChat({
-            transport: new DefaultChatTransport({
-                api: "/api/chat",
-            }),
-            async onToolCall({ toolCall }) {
-                if (toolCall.toolName === "display_diagram") {
-                    const { xml } = toolCall.input as { xml: string };
+    const {
+        messages,
+        sendMessage,
+        addToolResult,
+        status,
+        error,
+        setMessages,
+        stop,
+    } = useChat({
+        transport: new DefaultChatTransport({
+            api: "/api/chat",
+        }),
+        async onToolCall({ toolCall }) {
+            if (toolCall.toolName === "display_diagram") {
+                const { xml } = toolCall.input as { xml: string };
 
-                    const validationError = validateMxCellStructure(xml);
+                const validationError = validateMxCellStructure(xml);
 
-                    if (validationError) {
-                        addToolResult({
-                            tool: "display_diagram",
-                            toolCallId: toolCall.toolCallId,
-                            output: validationError,
-                        });
+                if (validationError) {
+                    addToolResult({
+                        tool: "display_diagram",
+                        toolCallId: toolCall.toolCallId,
+                        output: validationError,
+                    });
+                } else {
+                    addToolResult({
+                        tool: "display_diagram",
+                        toolCallId: toolCall.toolCallId,
+                        output: "Successfully displayed the diagram.",
+                    });
+                }
+            } else if (toolCall.toolName === "edit_diagram") {
+                const { edits } = toolCall.input as {
+                    edits: Array<{ search: string; replace: string }>;
+                };
+
+                let currentXml = "";
+                try {
+                    console.log("[edit_diagram] Starting...");
+                    // Use chartXML from ref directly - more reliable than export
+                    // especially on Vercel where DrawIO iframe may have latency issues
+                    // Using ref to avoid stale closure in callback
+                    const cachedXML = chartXMLRef.current;
+                    if (cachedXML) {
+                        currentXml = cachedXML;
+                        console.log(
+                            "[edit_diagram] Using cached chartXML, length:",
+                            currentXml.length
+                        );
                     } else {
-                        addToolResult({
-                            tool: "display_diagram",
-                            toolCallId: toolCall.toolCallId,
-                            output: "Successfully displayed the diagram.",
-                        });
+                        // Fallback to export only if no cached XML
+                        console.log(
+                            "[edit_diagram] No cached XML, fetching from DrawIO..."
+                        );
+                        currentXml = await onFetchChart(false);
+                        console.log(
+                            "[edit_diagram] Got XML from export, length:",
+                            currentXml.length
+                        );
                     }
-                } else if (toolCall.toolName === "edit_diagram") {
-                    const { edits } = toolCall.input as {
-                        edits: Array<{ search: string; replace: string }>;
-                    };
 
-                    let currentXml = "";
-                    try {
-                        console.log("[edit_diagram] Starting...");
-                        // Use chartXML from ref directly - more reliable than export
-                        // especially on Vercel where DrawIO iframe may have latency issues
-                        // Using ref to avoid stale closure in callback
-                        const cachedXML = chartXMLRef.current;
-                        if (cachedXML) {
-                            currentXml = cachedXML;
-                            console.log("[edit_diagram] Using cached chartXML, length:", currentXml.length);
-                        } else {
-                            // Fallback to export only if no cached XML
-                            console.log("[edit_diagram] No cached XML, fetching from DrawIO...");
-                            currentXml = await onFetchChart(false);
-                            console.log("[edit_diagram] Got XML from export, length:", currentXml.length);
-                        }
+                    const { replaceXMLParts } = await import("@/lib/utils");
+                    const editedXml = replaceXMLParts(currentXml, edits);
 
-                        const { replaceXMLParts } = await import("@/lib/utils");
-                        const editedXml = replaceXMLParts(currentXml, edits);
+                    onDisplayChart(editedXml);
 
-                        onDisplayChart(editedXml);
+                    addToolResult({
+                        tool: "edit_diagram",
+                        toolCallId: toolCall.toolCallId,
+                        output: `Successfully applied ${edits.length} edit(s) to the diagram.`,
+                    });
+                    console.log("[edit_diagram] Success");
+                } catch (error) {
+                    console.error("[edit_diagram] Failed:", error);
 
-                        addToolResult({
-                            tool: "edit_diagram",
-                            toolCallId: toolCall.toolCallId,
-                            output: `Successfully applied ${edits.length} edit(s) to the diagram.`,
-                        });
-                        console.log("[edit_diagram] Success");
-                    } catch (error) {
-                        console.error("[edit_diagram] Failed:", error);
+                    const errorMessage =
+                        error instanceof Error ? error.message : String(error);
 
-                        const errorMessage =
-                            error instanceof Error
-                                ? error.message
-                                : String(error);
-
-                        addToolResult({
-                            tool: "edit_diagram",
-                            toolCallId: toolCall.toolCallId,
-                            output: `Edit failed: ${errorMessage}
+                    addToolResult({
+                        tool: "edit_diagram",
+                        toolCallId: toolCall.toolCallId,
+                        output: `Edit failed: ${errorMessage}
 
 Current diagram XML:
 \`\`\`xml
@@ -147,14 +161,73 @@ ${currentXml || "No XML available"}
 \`\`\`
 
 Please retry with an adjusted search pattern or use display_diagram if retries are exhausted.`,
-                        });
-                    }
+                    });
                 }
-            },
-            onError: (error) => {
-                console.error("Chat error:", error);
-            },
-        });
+            }
+        },
+        onError: (error) => {
+            console.error("Chat error:", error);
+            setStreamingError(error);
+        },
+    });
+
+    // Streaming timeout detection - detects when stream stalls mid-response (e.g., Bedrock 503)
+    // This catches cases where onError doesn't fire because headers were already sent
+    const lastMessageCountRef = useRef(0);
+    const lastMessagePartsRef = useRef(0);
+
+    useEffect(() => {
+        // Clear streaming error when status changes to ready
+        if (status === "ready") {
+            setStreamingError(null);
+            lastMessageCountRef.current = 0;
+            lastMessagePartsRef.current = 0;
+            return;
+        }
+
+        if (status !== "streaming") return;
+
+        const STALL_TIMEOUT_MS = 15000; // 15 seconds without any update
+
+        // Capture current state BEFORE setting timeout
+        // This way we compare against values at the time timeout was set
+        const currentPartsCount = messages.reduce(
+            (acc, msg) => acc + (msg.parts?.length || 0),
+            0
+        );
+        const capturedMessageCount = messages.length;
+        const capturedPartsCount = currentPartsCount;
+
+        // Update refs immediately so next effect run has fresh values
+        lastMessageCountRef.current = messages.length;
+        lastMessagePartsRef.current = currentPartsCount;
+
+        const timeoutId = setTimeout(() => {
+            // Re-count parts at timeout time
+            const newPartsCount = messages.reduce(
+                (acc, msg) => acc + (msg.parts?.length || 0),
+                0
+            );
+
+            // If no change since timeout was set, stream has stalled
+            if (
+                messages.length === capturedMessageCount &&
+                newPartsCount === capturedPartsCount
+            ) {
+                console.error(
+                    "[Streaming Timeout] No activity for 15s - forcing error state"
+                );
+                setStreamingError(
+                    new Error(
+                        "Connection lost. The AI service may be temporarily unavailable. Please try again."
+                    )
+                );
+                stop(); // Allow user to retry by transitioning status to "ready"
+            }
+        }, STALL_TIMEOUT_MS);
+
+        return () => clearTimeout(timeoutId);
+    }, [status, messages, stop]);
 
     const messagesEndRef = useRef<HTMLDivElement>(null);
 
@@ -164,11 +237,15 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
         }
     }, [messages]);
 
-
     const onFormSubmit = async (e: React.FormEvent<HTMLFormElement>) => {
         e.preventDefault();
-        const isProcessing = status === "streaming" || status === "submitted";
+        // Allow retry if there's a streaming error (workaround for stop() not transitioning status)
+        const isProcessing =
+            (status === "streaming" || status === "submitted") &&
+            !streamingError;
         if (input.trim() && !isProcessing) {
+            // Clear any previous streaming error before starting new request
+            setStreamingError(null);
             try {
                 let chartXml = await onFetchChart();
                 chartXml = formatXML(chartXml);
@@ -233,7 +310,10 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
 
         // Find the user message before this assistant message
         let userMessageIndex = messageIndex - 1;
-        while (userMessageIndex >= 0 && messages[userMessageIndex].role !== "user") {
+        while (
+            userMessageIndex >= 0 &&
+            messages[userMessageIndex].role !== "user"
+        ) {
             userMessageIndex--;
         }
 
@@ -249,7 +329,10 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
         // Get the saved XML snapshot for this user message
         const savedXml = xmlSnapshotsRef.current.get(userMessageIndex);
         if (!savedXml) {
-            console.error("No saved XML snapshot for message index:", userMessageIndex);
+            console.error(
+                "No saved XML snapshot for message index:",
+                userMessageIndex
+            );
             return;
         }
 
@@ -294,7 +377,10 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
         // Get the saved XML snapshot for this user message
         const savedXml = xmlSnapshotsRef.current.get(messageIndex);
         if (!savedXml) {
-            console.error("No saved XML snapshot for message index:", messageIndex);
+            console.error(
+                "No saved XML snapshot for message index:",
+                messageIndex
+            );
             return;
         }
 
@@ -388,6 +474,14 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
                         >
                             About
                         </Link>
+                        <ButtonWithTooltip
+                            tooltipContent="Recent generation failures were caused by our AI provider's infrastructure issue, not the app code. After extensive debugging, I've switched providers and observed 30+ minutes of stability. If issues persist, please report on GitHub."
+                            variant="ghost"
+                            size="icon"
+                            className="h-6 w-6 text-green-500 hover:text-green-600"
+                        >
+                            <CheckCircle className="h-4 w-4" />
+                        </ButtonWithTooltip>
                     </div>
                     <div className="flex items-center gap-1">
                         <a
@@ -415,7 +509,7 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
             <main className="flex-1 overflow-hidden">
                 <ChatMessageDisplay
                     messages={messages}
-                    error={error}
+                    error={error || streamingError}
                     setInput={setInput}
                     setFiles={handleFileChange}
                     onRegenerate={handleRegenerate}
@@ -439,6 +533,7 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
                     onFileChange={handleFileChange}
                     showHistory={showHistory}
                     onToggleHistory={setShowHistory}
+                    error={error || streamingError}
                 />
             </footer>
         </div>

lib/ai-providers.ts

@@ -1,4 +1,5 @@
-import { bedrock } from '@ai-sdk/amazon-bedrock';
+import { createAmazonBedrock } from '@ai-sdk/amazon-bedrock';
+import { fromNodeProviderChain } from '@aws-sdk/credential-providers';
 import { openai, createOpenAI } from '@ai-sdk/openai';
 import { createAnthropic } from '@ai-sdk/anthropic';
 import { google, createGoogleGenerativeAI } from '@ai-sdk/google';
@@ -38,7 +39,7 @@ const ANTHROPIC_BETA_HEADERS = {
 
 // Map of provider to required environment variable
 const PROVIDER_ENV_VARS: Record<ProviderName, string | null> = {
-  bedrock: 'AWS_ACCESS_KEY_ID',
+  bedrock: null, // AWS SDK auto-uses IAM role on AWS, or env vars locally
   openai: 'OPENAI_API_KEY',
   anthropic: 'ANTHROPIC_API_KEY',
   google: 'GOOGLE_GENERATIVE_AI_API_KEY',
@@ -159,13 +160,20 @@ export function getAIModel(): ModelConfig {
   let headers: Record<string, string> | undefined = undefined;
 
   switch (provider) {
-    case 'bedrock':
-      model = bedrock(modelId);
+    case 'bedrock': {
+      // Use credential provider chain for IAM role support (Amplify, Lambda, etc.)
+      // Falls back to env vars (AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY) for local dev
+      const bedrockProvider = createAmazonBedrock({
+        region: process.env.AWS_REGION || 'us-west-2',
+        credentialProvider: fromNodeProviderChain(),
+      });
+      model = bedrockProvider(modelId);
       // Add Anthropic beta options if using Claude models via Bedrock
       if (modelId.includes('anthropic.claude')) {
         providerOptions = BEDROCK_ANTHROPIC_BETA;
       }
       break;
+    }
 
     case 'openai':
       if (process.env.OPENAI_BASE_URL) {

package.json

@@ -17,6 +17,7 @@
         "@ai-sdk/google": "^2.0.0",
         "@ai-sdk/openai": "^2.0.19",
         "@ai-sdk/react": "^2.0.22",
+        "@aws-sdk/credential-providers": "^3.943.0",
         "@next/third-parties": "^16.0.6",
         "@openrouter/ai-sdk-provider": "^1.2.3",
         "@radix-ui/react-dialog": "^1.1.6",