Revise preview feature stability note

Updated the preview feature note for stability.

.github/workflows/docker-build.yml

@@ -64,3 +64,27 @@ jobs:
           cache-to: type=gha,mode=max
           platforms: linux/amd64,linux/arm64
 
+      # Push to AWS ECR for App Runner auto-deploy
+      - name: Configure AWS credentials
+        if: github.event_name != 'pull_request' && github.ref == 'refs/heads/main'
+        uses: aws-actions/configure-aws-credentials@v4
+        with:
+          aws-access-key-id: ${{ secrets.AWS_ACCESS_KEY_ID }}
+          aws-secret-access-key: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
+          aws-region: ap-northeast-1
+
+      - name: Login to Amazon ECR
+        if: github.event_name != 'pull_request' && github.ref == 'refs/heads/main'
+        id: login-ecr
+        uses: aws-actions/amazon-ecr-login@v2
+
+      - name: Push to ECR (triggers App Runner auto-deploy)
+        if: github.event_name != 'pull_request' && github.ref == 'refs/heads/main'
+        env:
+          REPO_LOWER: ${{ github.repository }}
+        run: |
+          REPO_LOWER=$(echo "$REPO_LOWER" | tr '[:upper:]' '[:lower:]')
+          docker pull ghcr.io/${REPO_LOWER}:latest
+          docker tag ghcr.io/${REPO_LOWER}:latest ${{ secrets.AWS_ACCOUNT_ID }}.dkr.ecr.ap-northeast-1.amazonaws.com/next-ai-draw-io:latest
+          docker push ${{ secrets.AWS_ACCOUNT_ID }}.dkr.ecr.ap-northeast-1.amazonaws.com/next-ai-draw-io:latest
+

.gitignore

@@ -2,6 +2,8 @@
 
 # dependencies
 /node_modules
+packages/*/node_modules
+packages/*/dist
 /.pnp
 .pnp.*
 .yarn/*
@@ -46,3 +48,5 @@ push-via-ec2.sh
 .dev.vars
 .open-next/
 .wrangler/
+.env*.local
+

Dockerfile

@@ -54,6 +54,6 @@ EXPOSE 3000
 ENV PORT=3000
 ENV HOSTNAME="0.0.0.0"
 
-# Start the application
-CMD ["node", "server.js"]
+# Start the application (HOSTNAME override needed for AWS App Runner)
+CMD ["sh", "-c", "HOSTNAME=0.0.0.0 exec node server.js"]
 

README.md

@@ -30,6 +30,7 @@ https://github.com/user-attachments/assets/9d60a3e8-4a1c-4b5e-acbb-26af2d3eabd1
   - [Table of Contents](#table-of-contents)
   - [Examples](#examples)
   - [Features](#features)
+  - [MCP Server (Preview)](#mcp-server-preview)
   - [Getting Started](#getting-started)
     - [Try it Online](#try-it-online)
     - [Run with Docker (Recommended)](#run-with-docker-recommended)
@@ -92,6 +93,36 @@ Here are some example prompts and their generated diagrams:
 -   **Cloud Architecture Diagram Support**: Specialized support for generating cloud architecture diagrams (AWS, GCP, Azure)
 -   **Animated Connectors**: Create dynamic and animated connectors between diagram elements for better visualization
 
+## MCP Server (Preview)
+
+> **Preview Feature**: This feature is experimental and may not stable.
+
+Use Next AI Draw.io with AI agents like Claude Desktop, Cursor, and VS Code via MCP (Model Context Protocol).
+
+```json
+{
+  "mcpServers": {
+    "drawio": {
+      "command": "npx",
+      "args": ["@next-ai-drawio/mcp-server@latest"]
+    }
+  }
+}
+```
+
+### Claude Code CLI
+
+```bash
+claude mcp add drawio -- npx @next-ai-drawio/mcp-server@latest
+```
+
+Then ask Claude to create diagrams:
+> "Create a flowchart showing user authentication with login, MFA, and session management"
+
+The diagram appears in your browser in real-time!
+
+See the [MCP Server README](./packages/mcp-server/README.md) for VS Code, Cursor, and other client configurations.
+
 ## Getting Started
 
 ### Try it Online
@@ -207,7 +238,7 @@ All providers except AWS Bedrock and OpenRouter support custom endpoints.
 
 **Model Requirements**: This task requires strong model capabilities for generating long-form text with strict formatting constraints (draw.io XML). Recommended models include Claude Sonnet 4.5, GPT-5.1, Gemini 3 Pro, and DeepSeek V3.2/R1.
 
-Note that `claude` series has trained on draw.io diagrams with cloud architecture logos like AWS, Azue, GCP. So if you want to create cloud architecture diagrams, this is the best choice.
+Note that `claude` series has trained on draw.io diagrams with cloud architecture logos like AWS, Azure, GCP. So if you want to create cloud architecture diagrams, this is the best choice.
 
 
 ## How It Works

app/api/chat/route.ts

@@ -3,10 +3,12 @@ import {
     convertToModelMessages,
     createUIMessageStream,
     createUIMessageStreamResponse,
+    InvalidToolInputError,
     LoadAPIKeyError,
     stepCountIs,
     streamText,
 } from "ai"
+import { jsonrepair } from "jsonrepair"
 import { z } from "zod"
 import { getAIModel, supportsPromptCaching } from "@/lib/ai-providers"
 import { findCachedResponse } from "@/lib/cached-responses"
@@ -68,29 +70,41 @@ function isMinimalDiagram(xml: string): boolean {
 
 // Helper function to replace historical tool call XML with placeholders
 // This reduces token usage and forces LLM to rely on the current diagram XML (source of truth)
+// Also fixes invalid/undefined inputs from interrupted streaming
 function replaceHistoricalToolInputs(messages: any[]): any[] {
     return messages.map((msg) => {
         if (msg.role !== "assistant" || !Array.isArray(msg.content)) {
             return msg
         }
-        const replacedContent = msg.content.map((part: any) => {
-            if (part.type === "tool-call") {
-                const toolName = part.toolName
-                if (
-                    toolName === "display_diagram" ||
-                    toolName === "edit_diagram"
-                ) {
-                    return {
-                        ...part,
-                        input: {
-                            placeholder:
-                                "[XML content replaced - see current diagram XML in system context]",
-                        },
+        const replacedContent = msg.content
+            .map((part: any) => {
+                if (part.type === "tool-call") {
+                    const toolName = part.toolName
+                    // Fix invalid/undefined inputs from interrupted streaming
+                    if (
+                        !part.input ||
+                        typeof part.input !== "object" ||
+                        Object.keys(part.input).length === 0
+                    ) {
+                        // Skip tool calls with invalid inputs entirely
+                        return null
+                    }
+                    if (
+                        toolName === "display_diagram" ||
+                        toolName === "edit_diagram"
+                    ) {
+                        return {
+                            ...part,
+                            input: {
+                                placeholder:
+                                    "[XML content replaced - see current diagram XML in system context]",
+                            },
+                        }
                     }
                 }
-            }
-            return part
-        })
+                return part
+            })
+            .filter(Boolean) // Remove null entries (invalid tool calls)
         return { ...msg, content: replacedContent }
     })
 }
@@ -200,6 +214,9 @@ async function handleChatRequest(req: Request): Promise<Response> {
         modelId: req.headers.get("x-ai-model"),
     }
 
+    // Read minimal style preference from header
+    const minimalStyle = req.headers.get("x-minimal-style") === "true"
+
     // Get AI model with optional client overrides
     const { model, providerOptions, headers, modelId } =
         getAIModel(clientOverrides)
@@ -211,7 +228,7 @@ async function handleChatRequest(req: Request): Promise<Response> {
     )
 
     // Get the appropriate system prompt based on model (extended for Opus/Haiku 4.5)
-    const systemMessage = getSystemPrompt(modelId)
+    const systemMessage = getSystemPrompt(modelId, minimalStyle)
 
     // Extract file parts (images) from the last message
     const fileParts =
@@ -226,6 +243,36 @@ ${userInputText}
     // Convert UIMessages to ModelMessages and add system message
     const modelMessages = convertToModelMessages(messages)
 
+    // DEBUG: Log incoming messages structure
+    console.log("[route.ts] Incoming messages count:", messages.length)
+    messages.forEach((msg: any, idx: number) => {
+        console.log(
+            `[route.ts] Message ${idx} role:`,
+            msg.role,
+            "parts count:",
+            msg.parts?.length,
+        )
+        if (msg.parts) {
+            msg.parts.forEach((part: any, partIdx: number) => {
+                if (
+                    part.type === "tool-invocation" ||
+                    part.type === "tool-result"
+                ) {
+                    console.log(`[route.ts]   Part ${partIdx}:`, {
+                        type: part.type,
+                        toolName: part.toolName,
+                        hasInput: !!part.input,
+                        inputType: typeof part.input,
+                        inputKeys:
+                            part.input && typeof part.input === "object"
+                                ? Object.keys(part.input)
+                                : null,
+                    })
+                }
+            })
+        }
+    })
+
     // Replace historical tool call XML with placeholders to reduce tokens
     // Disabled by default - some models (e.g. minimax) copy placeholders instead of generating XML
     const enableHistoryReplace =
@@ -241,6 +288,63 @@ ${userInputText}
             msg.content && Array.isArray(msg.content) && msg.content.length > 0,
     )
 
+    // Filter out tool-calls with invalid inputs (from failed repair or interrupted streaming)
+    // Bedrock API rejects messages where toolUse.input is not a valid JSON object
+    enhancedMessages = enhancedMessages
+        .map((msg: any) => {
+            if (msg.role !== "assistant" || !Array.isArray(msg.content)) {
+                return msg
+            }
+            const filteredContent = msg.content.filter((part: any) => {
+                if (part.type === "tool-call") {
+                    // Check if input is a valid object (not null, undefined, or empty)
+                    if (
+                        !part.input ||
+                        typeof part.input !== "object" ||
+                        Object.keys(part.input).length === 0
+                    ) {
+                        console.warn(
+                            `[route.ts] Filtering out tool-call with invalid input:`,
+                            { toolName: part.toolName, input: part.input },
+                        )
+                        return false
+                    }
+                }
+                return true
+            })
+            return { ...msg, content: filteredContent }
+        })
+        .filter((msg: any) => msg.content && msg.content.length > 0)
+
+    // DEBUG: Log modelMessages structure (what's being sent to AI)
+    console.log("[route.ts] Model messages count:", enhancedMessages.length)
+    enhancedMessages.forEach((msg: any, idx: number) => {
+        console.log(
+            `[route.ts] ModelMsg ${idx} role:`,
+            msg.role,
+            "content count:",
+            msg.content?.length,
+        )
+        if (msg.content) {
+            msg.content.forEach((part: any, partIdx: number) => {
+                if (part.type === "tool-call" || part.type === "tool-result") {
+                    console.log(`[route.ts]   Content ${partIdx}:`, {
+                        type: part.type,
+                        toolName: part.toolName,
+                        hasInput: !!part.input,
+                        inputType: typeof part.input,
+                        inputValue:
+                            part.input === undefined
+                                ? "undefined"
+                                : part.input === null
+                                  ? "null"
+                                  : "object",
+                    })
+                }
+            })
+        }
+    })
+
     // Update the last message with user input only (XML moved to separate cached system message)
     if (enhancedMessages.length >= 1) {
         const lastModelMessage = enhancedMessages[enhancedMessages.length - 1]
@@ -320,6 +424,67 @@ ${userInputText}
             maxOutputTokens: parseInt(process.env.MAX_OUTPUT_TOKENS, 10),
         }),
         stopWhen: stepCountIs(5),
+        // Repair truncated tool calls when maxOutputTokens is reached mid-JSON
+        experimental_repairToolCall: async ({ toolCall, error }) => {
+            // DEBUG: Log what we're trying to repair
+            console.log(`[repairToolCall] Tool: ${toolCall.toolName}`)
+            console.log(
+                `[repairToolCall] Error: ${error.name} - ${error.message}`,
+            )
+            console.log(`[repairToolCall] Input type: ${typeof toolCall.input}`)
+            console.log(`[repairToolCall] Input value:`, toolCall.input)
+
+            // Only attempt repair for invalid tool input (broken JSON from truncation)
+            if (
+                error instanceof InvalidToolInputError ||
+                error.name === "AI_InvalidToolInputError"
+            ) {
+                try {
+                    // Pre-process to fix common LLM JSON errors that jsonrepair can't handle
+                    let inputToRepair = toolCall.input
+                    if (typeof inputToRepair === "string") {
+                        // Fix `:=` instead of `: ` (LLM sometimes generates this)
+                        inputToRepair = inputToRepair.replace(/:=/g, ": ")
+                        // Fix `= "` instead of `: "`
+                        inputToRepair = inputToRepair.replace(/=\s*"/g, ': "')
+                    }
+                    // Use jsonrepair to fix truncated JSON
+                    const repairedInput = jsonrepair(inputToRepair)
+                    console.log(
+                        `[repairToolCall] Repaired truncated JSON for tool: ${toolCall.toolName}`,
+                    )
+                    return { ...toolCall, input: repairedInput }
+                } catch (repairError) {
+                    console.warn(
+                        `[repairToolCall] Failed to repair JSON for tool: ${toolCall.toolName}`,
+                        repairError,
+                    )
+                    // Return a placeholder input to avoid API errors in multi-step
+                    // The tool will fail gracefully on client side
+                    if (toolCall.toolName === "edit_diagram") {
+                        return {
+                            ...toolCall,
+                            input: {
+                                operations: [],
+                                _error: "JSON repair failed - no operations to apply",
+                            },
+                        }
+                    }
+                    if (toolCall.toolName === "display_diagram") {
+                        return {
+                            ...toolCall,
+                            input: {
+                                xml: "",
+                                _error: "JSON repair failed - empty diagram",
+                            },
+                        }
+                    }
+                    return null
+                }
+            }
+            // Don't attempt to repair other errors (like NoSuchToolError)
+            return null
+        },
         messages: allMessages,
         ...(providerOptions && { providerOptions }), // This now includes all reasoning configs
         ...(headers && { headers }),
@@ -340,36 +505,32 @@ ${userInputText}
         tools: {
             // Client-side tool that will be executed on the client
             display_diagram: {
-                description: `Display a diagram on draw.io. Pass the XML content inside <root> tags.
+                description: `Display a diagram on draw.io. Pass ONLY the mxCell elements - wrapper tags and root cells are added automatically.
 
 VALIDATION RULES (XML will be rejected if violated):
-1. All mxCell elements must be DIRECT children of <root> - never nested
-2. Every mxCell needs a unique id
-3. Every mxCell (except id="0") needs a valid parent attribute
-4. Edge source/target must reference existing cell IDs
-5. Escape special chars in values: &lt; &gt; &amp; &quot;
-6. Always start with: <mxCell id="0"/><mxCell id="1" parent="0"/>
+1. Generate ONLY mxCell elements - NO wrapper tags (<mxfile>, <mxGraphModel>, <root>)
+2. Do NOT include root cells (id="0" or id="1") - they are added automatically
+3. All mxCell elements must be siblings - never nested
+4. Every mxCell needs a unique id (start from "2")
+5. Every mxCell needs a valid parent attribute (use "1" for top-level)
+6. Escape special chars in values: &lt; &gt; &amp; &quot;
 
-Example with swimlanes and edges (note: all mxCells are siblings):
-<root>
-  <mxCell id="0"/>
-  <mxCell id="1" parent="0"/>
-  <mxCell id="lane1" value="Frontend" style="swimlane;" vertex="1" parent="1">
-    <mxGeometry x="40" y="40" width="200" height="200" as="geometry"/>
-  </mxCell>
-  <mxCell id="step1" value="Step 1" style="rounded=1;" vertex="1" parent="lane1">
-    <mxGeometry x="20" y="60" width="160" height="40" as="geometry"/>
-  </mxCell>
-  <mxCell id="lane2" value="Backend" style="swimlane;" vertex="1" parent="1">
-    <mxGeometry x="280" y="40" width="200" height="200" as="geometry"/>
-  </mxCell>
-  <mxCell id="step2" value="Step 2" style="rounded=1;" vertex="1" parent="lane2">
-    <mxGeometry x="20" y="60" width="160" height="40" as="geometry"/>
-  </mxCell>
-  <mxCell id="edge1" style="edgeStyle=orthogonalEdgeStyle;endArrow=classic;" edge="1" parent="1" source="step1" target="step2">
-    <mxGeometry relative="1" as="geometry"/>
-  </mxCell>
-</root>
+Example (generate ONLY this - no wrapper tags):
+<mxCell id="lane1" value="Frontend" style="swimlane;" vertex="1" parent="1">
+  <mxGeometry x="40" y="40" width="200" height="200" as="geometry"/>
+</mxCell>
+<mxCell id="step1" value="Step 1" style="rounded=1;" vertex="1" parent="lane1">
+  <mxGeometry x="20" y="60" width="160" height="40" as="geometry"/>
+</mxCell>
+<mxCell id="lane2" value="Backend" style="swimlane;" vertex="1" parent="1">
+  <mxGeometry x="280" y="40" width="200" height="200" as="geometry"/>
+</mxCell>
+<mxCell id="step2" value="Step 2" style="rounded=1;" vertex="1" parent="lane2">
+  <mxGeometry x="20" y="60" width="160" height="40" as="geometry"/>
+</mxCell>
+<mxCell id="edge1" style="edgeStyle=orthogonalEdgeStyle;endArrow=classic;" edge="1" parent="1" source="step1" target="step2">
+  <mxGeometry relative="1" as="geometry"/>
+</mxCell>
 
 Notes:
 - For AWS diagrams, use **AWS 2025 icons**.
@@ -382,32 +543,56 @@ Notes:
                 }),
             },
             edit_diagram: {
-                description: `Edit specific parts of the current diagram by replacing exact line matches. Use this tool to make targeted fixes without regenerating the entire XML.
-CRITICAL: Copy-paste the EXACT search pattern from the "Current diagram XML" in system context. Do NOT reorder attributes or reformat - the attribute order in draw.io XML varies and you MUST match it exactly.
-IMPORTANT: Keep edits concise:
-- COPY the exact mxCell line from the current XML (attribute order matters!)
-- Only include the lines that are changing, plus 1-2 surrounding lines for context if needed
-- Break large changes into multiple smaller edits
-- Each search must contain complete lines (never truncate mid-line)
-- First match only - be specific enough to target the right element
+                description: `Edit the current diagram by ID-based operations (update/add/delete cells).
 
-⚠️ JSON ESCAPING: Every " inside string values MUST be escaped as \\". Example: x=\\"100\\" y=\\"200\\" - BOTH quotes need backslashes!`,
+Operations:
+- update: Replace an existing cell by its id. Provide cell_id and complete new_xml.
+- add: Add a new cell. Provide cell_id (new unique id) and new_xml.
+- delete: Remove a cell by its id. Only cell_id is needed.
+
+For update/add, new_xml must be a complete mxCell element including mxGeometry.
+
+⚠️ JSON ESCAPING: Every " inside new_xml MUST be escaped as \\". Example: id=\\"5\\" value=\\"Label\\"`,
                 inputSchema: z.object({
-                    edits: z
+                    operations: z
                         .array(
                             z.object({
-                                search: z
+                                type: z
+                                    .enum(["update", "add", "delete"])
+                                    .describe("Operation type"),
+                                cell_id: z
                                     .string()
                                     .describe(
-                                        "EXACT lines copied from current XML (preserve attribute order!)",
+                                        "The id of the mxCell. Must match the id attribute in new_xml.",
                                     ),
-                                replace: z
+                                new_xml: z
                                     .string()
-                                    .describe("Replacement lines"),
+                                    .optional()
+                                    .describe(
+                                        "Complete mxCell XML element (required for update/add)",
+                                    ),
                             }),
                         )
+                        .describe("Array of operations to apply"),
+                }),
+            },
+            append_diagram: {
+                description: `Continue generating diagram XML when previous display_diagram output was truncated due to length limits.
+
+WHEN TO USE: Only call this tool after display_diagram was truncated (you'll see an error message about truncation).
+
+CRITICAL INSTRUCTIONS:
+1. Do NOT include any wrapper tags - just continue the mxCell elements
+2. Continue from EXACTLY where your previous output stopped
+3. Complete the remaining mxCell elements
+4. If still truncated, call append_diagram again with the next fragment
+
+Example: If previous output ended with '<mxCell id="x" style="rounded=1', continue with ';" vertex="1">...' and complete the remaining elements.`,
+                inputSchema: z.object({
+                    xml: z
+                        .string()
                         .describe(
-                            "Array of search/replace pairs to apply sequentially",
+                            "Continuation XML fragment to append (NO wrapper tags)",
                         ),
                 }),
             },
@@ -435,6 +620,7 @@ IMPORTANT: Keep edits concise:
                 return {
                     inputTokens: totalInputTokens,
                     outputTokens: usage.outputTokens ?? 0,
+                    finishReason: (part as any).finishReason,
                 }
             }
             return undefined

app/api/chat/xml_guide.md

@@ -81,16 +81,15 @@ Contains the actual diagram data.
 
 ## Root Cell Container: `<root>`
 
-Contains all the cells in the diagram.
+Contains all the cells in the diagram. **Note:** When generating diagrams, you only need to provide the mxCell elements - the root container and root cells (id="0", id="1") are added automatically.
 
-**Example:**
+**Internal structure (auto-generated):**
 
 ```xml
 <root>
-<mxCell id="0"/>
-<mxCell id="1" parent="0"/>
-
-  <!-- Other cells go here -->
+  <mxCell id="0"/>           <!-- Auto-added -->
+  <mxCell id="1" parent="0"/> <!-- Auto-added -->
+  <!-- Your mxCell elements go here (start from id="2") -->
 </root>
 ```
 
@@ -203,15 +202,15 @@ Draw.io files contain two special cells that are always present:
 1.  **Root Cell** (id = "0"): The parent of all cells
 2.  **Default Parent Cell** (id = "1", parent = "0"): The default layer and parent for most cells
 
-## Tips for Manually Creating Draw.io XML
+## Tips for Creating Draw.io XML
 
-1.  Start with the basic structure (`mxfile`, `diagram`, `mxGraphModel`, `root`)
-2.  Always include the two special cells (id = "0" and id = "1")
+1.  **Generate ONLY mxCell elements** - wrapper tags and root cells (id="0", id="1") are added automatically
+2.  Start IDs from "2" (id="0" and id="1" are reserved for root cells)
 3.  Assign unique and sequential IDs to all cells
-4.  Define parent relationships correctly
+4.  Define parent relationships correctly (use parent="1" for top-level shapes)
 5.  Use `mxGeometry` elements to position shapes
 6.  For connectors, specify `source` and `target` attributes
-7.  **CRITICAL: All mxCell elements must be DIRECT children of `<root>`. NEVER nest mxCell inside another mxCell.**
+7.  **CRITICAL: All mxCell elements must be siblings. NEVER nest mxCell inside another mxCell.**
 
 ## Common Patterns
 

app/manifest.ts

@@ -0,0 +1,27 @@
+import type { MetadataRoute } from "next";
+
+export default function manifest(): MetadataRoute.Manifest {
+  return {
+    name: 'Next AI Draw.io',
+    short_name: 'AIDraw.io',
+    description: 'Create AWS architecture diagrams, flowcharts, and technical diagrams using AI. Free online tool integrating draw.io with AI assistance for professional diagram creation.',
+    start_url: '/',
+    display: 'standalone',
+    background_color: '#f9fafb',
+    theme_color: '#171d26',
+    icons: [
+      {
+        src: '/favicon-192x192.png',
+        sizes: '192x192',
+        type: 'image/png',
+        purpose: 'any',
+      },
+      {
+        src: '/favicon-512x512.png',
+        sizes: '512x512',
+        type: 'image/png',
+        purpose: 'any',
+      },
+    ],
+  }
+}

app/page.tsx

@@ -15,8 +15,13 @@ 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,
+        onDrawioLoad,
+        resetDrawioReady,
+        saveDiagramToStorage,
+    } = useDiagram()
     const [isMobile, setIsMobile] = useState(false)
     const [isChatVisible, setIsChatVisible] = useState(true)
     const [drawioUi, setDrawioUi] = useState<"min" | "sketch">("min")
@@ -35,12 +40,10 @@ export default function Home() {
 
         const savedDarkMode = localStorage.getItem("next-ai-draw-io-dark-mode")
         if (savedDarkMode !== null) {
-            // Use saved preference
             const isDark = savedDarkMode === "true"
             setDarkMode(isDark)
             document.documentElement.classList.toggle("dark", isDark)
         } else {
-            // First visit: match browser preference
             const prefersDark = window.matchMedia(
                 "(prefers-color-scheme: dark)",
             ).matches
@@ -58,12 +61,20 @@ export default function Home() {
         setIsLoaded(true)
     }, [])
 
-    const toggleDarkMode = () => {
+    const handleDarkModeChange = async () => {
+        await saveDiagramToStorage()
         const newValue = !darkMode
         setDarkMode(newValue)
         localStorage.setItem("next-ai-draw-io-dark-mode", String(newValue))
         document.documentElement.classList.toggle("dark", newValue)
-        // Reset so onDrawioLoad fires again after remount
+        resetDrawioReady()
+    }
+
+    const handleDrawioUiChange = async () => {
+        await saveDiagramToStorage()
+        const newUi = drawioUi === "min" ? "sketch" : "min"
+        localStorage.setItem("drawio-theme", newUi)
+        setDrawioUi(newUi)
         resetDrawioReady()
     }
 
@@ -182,15 +193,9 @@ export default function Home() {
                             isVisible={isChatVisible}
                             onToggleVisibility={toggleChatPanel}
                             drawioUi={drawioUi}
-                            onToggleDrawioUi={() => {
-                                const newUi =
-                                    drawioUi === "min" ? "sketch" : "min"
-                                localStorage.setItem("drawio-theme", newUi)
-                                setDrawioUi(newUi)
-                                resetDrawioReady()
-                            }}
+                            onToggleDrawioUi={handleDrawioUiChange}
                             darkMode={darkMode}
-                            onToggleDarkMode={toggleDarkMode}
+                            onToggleDarkMode={handleDarkModeChange}
                             isMobile={isMobile}
                             onCloseProtectionChange={setCloseProtection}
                         />

components/chat-example-panel.tsx

@@ -1,6 +1,13 @@
 "use client"
 
-import { Cloud, FileText, GitBranch, Palette, Zap } from "lucide-react"
+import {
+    Cloud,
+    FileText,
+    GitBranch,
+    Palette,
+    Terminal,
+    Zap,
+} from "lucide-react"
 
 interface ExampleCardProps {
     icon: React.ReactNode
@@ -108,6 +115,33 @@ export default function ExamplePanel({
 
     return (
         <div className="py-6 px-2 animate-fade-in">
+            {/* MCP Server Notice */}
+            <a
+                href="https://github.com/DayuanJiang/next-ai-draw-io/tree/main/packages/mcp-server"
+                target="_blank"
+                rel="noopener noreferrer"
+                className="block mb-4 p-3 rounded-xl bg-gradient-to-r from-purple-500/10 to-blue-500/10 border border-purple-500/20 hover:border-purple-500/40 transition-colors group"
+            >
+                <div className="flex items-center gap-3">
+                    <div className="w-8 h-8 rounded-lg bg-purple-500/20 flex items-center justify-center shrink-0">
+                        <Terminal className="w-4 h-4 text-purple-500" />
+                    </div>
+                    <div className="min-w-0">
+                        <div className="flex items-center gap-2">
+                            <span className="text-sm font-medium text-foreground group-hover:text-purple-500 transition-colors">
+                                MCP Server
+                            </span>
+                            <span className="px-1.5 py-0.5 text-[10px] font-semibold bg-purple-500 text-white rounded">
+                                PREVIEW
+                            </span>
+                        </div>
+                        <p className="text-xs text-muted-foreground">
+                            Use in Claude Desktop, VS Code & Cursor
+                        </p>
+                    </div>
+                </div>
+            </a>
+
             {/* Welcome section */}
             <div className="text-center mb-6">
                 <h2 className="text-lg font-semibold text-foreground mb-2">

components/chat-input.tsx

@@ -17,7 +17,13 @@ import { HistoryDialog } from "@/components/history-dialog"
 import { ResetWarningModal } from "@/components/reset-warning-modal"
 import { SaveDialog } from "@/components/save-dialog"
 import { Button } from "@/components/ui/button"
+import { Switch } from "@/components/ui/switch"
 import { Textarea } from "@/components/ui/textarea"
+import {
+    Tooltip,
+    TooltipContent,
+    TooltipTrigger,
+} from "@/components/ui/tooltip"
 import { useDiagram } from "@/contexts/diagram-context"
 import { isPdfFile, isTextFile } from "@/lib/pdf-utils"
 import { FilePreviewList } from "./file-preview-list"
@@ -129,6 +135,8 @@ interface ChatInputProps {
     onToggleHistory?: (show: boolean) => void
     sessionId?: string
     error?: Error | null
+    minimalStyle?: boolean
+    onMinimalStyleChange?: (value: boolean) => void
 }
 
 export function ChatInput({
@@ -144,6 +152,8 @@ export function ChatInput({
     onToggleHistory = () => {},
     sessionId,
     error = null,
+    minimalStyle = false,
+    onMinimalStyleChange = () => {},
 }: ChatInputProps) {
     const { diagramHistory, saveDiagramToFile } = useDiagram()
     const textareaRef = useRef<HTMLTextAreaElement>(null)
@@ -343,6 +353,32 @@ export function ChatInput({
                             showHistory={showHistory}
                             onToggleHistory={onToggleHistory}
                         />
+
+                        <Tooltip>
+                            <TooltipTrigger asChild>
+                                <div className="flex items-center gap-1.5">
+                                    <Switch
+                                        id="minimal-style"
+                                        checked={minimalStyle}
+                                        onCheckedChange={onMinimalStyleChange}
+                                        className="scale-75"
+                                    />
+                                    <label
+                                        htmlFor="minimal-style"
+                                        className={`text-xs cursor-pointer select-none ${
+                                            minimalStyle
+                                                ? "text-primary font-medium"
+                                                : "text-muted-foreground"
+                                        }`}
+                                    >
+                                        {minimalStyle ? "Minimal" : "Styled"}
+                                    </label>
+                                </div>
+                            </TooltipTrigger>
+                            <TooltipContent side="top">
+                                Use minimal for faster generation (no colors)
+                            </TooltipContent>
+                        </Tooltip>
                     </div>
 
                     {/* Right actions */}

components/chat-message-display.tsx

@@ -10,9 +10,7 @@ import {
     Cpu,
     FileCode,
     FileText,
-    Minus,
     Pencil,
-    Plus,
     RotateCcw,
     ThumbsDown,
     ThumbsUp,
@@ -29,13 +27,37 @@ import {
     ReasoningTrigger,
 } from "@/components/ai-elements/reasoning"
 import { ScrollArea } from "@/components/ui/scroll-area"
-import { convertToLegalXml, replaceNodes, validateAndFixXml } from "@/lib/utils"
+import {
+    applyDiagramOperations,
+    convertToLegalXml,
+    isMxCellXmlComplete,
+    replaceNodes,
+    validateAndFixXml,
+} from "@/lib/utils"
 import ExamplePanel from "./chat-example-panel"
 import { CodeBlock } from "./code-block"
 
-interface EditPair {
-    search: string
-    replace: string
+interface DiagramOperation {
+    type: "update" | "add" | "delete"
+    cell_id: string
+    new_xml?: string
+}
+
+// Helper to extract complete operations from streaming input
+function getCompleteOperations(
+    operations: DiagramOperation[] | undefined,
+): DiagramOperation[] {
+    if (!operations || !Array.isArray(operations)) return []
+    return operations.filter(
+        (op) =>
+            op &&
+            typeof op.type === "string" &&
+            ["update", "add", "delete"].includes(op.type) &&
+            typeof op.cell_id === "string" &&
+            op.cell_id.length > 0 &&
+            // delete doesn't need new_xml, update/add do
+            (op.type === "delete" || typeof op.new_xml === "string"),
+    )
 }
 
 // Tool part interface for type safety
@@ -43,49 +65,44 @@ interface ToolPartLike {
     type: string
     toolCallId: string
     state?: string
-    input?: { xml?: string; edits?: EditPair[] } & Record<string, unknown>
+    input?: {
+        xml?: string
+        operations?: DiagramOperation[]
+    } & Record<string, unknown>
     output?: string
 }
 
-function EditDiffDisplay({ edits }: { edits: EditPair[] }) {
+function OperationsDisplay({ operations }: { operations: DiagramOperation[] }) {
     return (
         <div className="space-y-3">
-            {edits.map((edit, index) => (
+            {operations.map((op, index) => (
                 <div
-                    key={`${(edit.search || "").slice(0, 50)}-${(edit.replace || "").slice(0, 50)}-${index}`}
+                    key={`${op.type}-${op.cell_id}-${index}`}
                     className="rounded-lg border border-border/50 overflow-hidden bg-background/50"
                 >
                     <div className="px-3 py-1.5 bg-muted/40 border-b border-border/30 flex items-center gap-2">
-                        <span className="text-xs font-medium text-muted-foreground">
-                            Change {index + 1}
+                        <span
+                            className={`text-[10px] font-medium uppercase tracking-wide ${
+                                op.type === "delete"
+                                    ? "text-red-600"
+                                    : op.type === "add"
+                                      ? "text-green-600"
+                                      : "text-blue-600"
+                            }`}
+                        >
+                            {op.type}
+                        </span>
+                        <span className="text-xs text-muted-foreground">
+                            cell_id: {op.cell_id}
                         </span>
                     </div>
-                    <div className="divide-y divide-border/30">
-                        {/* Search (old) */}
+                    {op.new_xml && (
                         <div className="px-3 py-2">
-                            <div className="flex items-center gap-1.5 mb-1.5">
-                                <Minus className="w-3 h-3 text-red-500" />
-                                <span className="text-[10px] font-medium text-red-600 uppercase tracking-wide">
-                                    Remove
-                                </span>
-                            </div>
-                            <pre className="text-[11px] font-mono text-red-700 bg-red-50 rounded px-2 py-1.5 overflow-x-auto whitespace-pre-wrap break-all">
-                                {edit.search}
+                            <pre className="text-[11px] font-mono text-foreground/80 bg-muted/30 rounded px-2 py-1.5 overflow-x-auto whitespace-pre-wrap break-all">
+                                {op.new_xml}
                             </pre>
                         </div>
-                        {/* Replace (new) */}
-                        <div className="px-3 py-2">
-                            <div className="flex items-center gap-1.5 mb-1.5">
-                                <Plus className="w-3 h-3 text-green-500" />
-                                <span className="text-[10px] font-medium text-green-600 uppercase tracking-wide">
-                                    Add
-                                </span>
-                            </div>
-                            <pre className="text-[11px] font-mono text-green-700 bg-green-50 rounded px-2 py-1.5 overflow-x-auto whitespace-pre-wrap break-all">
-                                {edit.replace}
-                            </pre>
-                        </div>
-                    </div>
+                    )}
                 </div>
             ))}
         </div>
@@ -168,6 +185,7 @@ interface ChatMessageDisplayProps {
     setInput: (input: string) => void
     setFiles: (files: File[]) => void
     processedToolCallsRef: MutableRefObject<Set<string>>
+    editDiagramOriginalXmlRef: MutableRefObject<Map<string, string>>
     sessionId?: string
     onRegenerate?: (messageIndex: number) => void
     onEditMessage?: (messageIndex: number, newText: string) => void
@@ -179,6 +197,7 @@ export function ChatMessageDisplay({
     setInput,
     setFiles,
     processedToolCallsRef,
+    editDiagramOriginalXmlRef,
     sessionId,
     onRegenerate,
     onEditMessage,
@@ -188,6 +207,22 @@ export function ChatMessageDisplay({
     const messagesEndRef = useRef<HTMLDivElement>(null)
     const previousXML = useRef<string>("")
     const processedToolCalls = processedToolCallsRef
+    // Track the last processed XML per toolCallId to skip redundant processing during streaming
+    const lastProcessedXmlRef = useRef<Map<string, string>>(new Map())
+    // Debounce streaming diagram updates - store pending XML and timeout
+    const pendingXmlRef = useRef<string | null>(null)
+    const debounceTimeoutRef = useRef<ReturnType<typeof setTimeout> | null>(
+        null,
+    )
+    const STREAMING_DEBOUNCE_MS = 150 // Only update diagram every 150ms during streaming
+    // Refs for edit_diagram streaming
+    const pendingEditRef = useRef<{
+        operations: DiagramOperation[]
+        toolCallId: string
+    } | null>(null)
+    const editDebounceTimeoutRef = useRef<ReturnType<typeof setTimeout> | null>(
+        null,
+    )
     const [expandedTools, setExpandedTools] = useState<Record<string, boolean>>(
         {},
     )
@@ -288,11 +323,14 @@ export function ChatMessageDisplay({
                 const parseError = testDoc.querySelector("parsererror")
 
                 if (parseError) {
-                    console.error(
-                        "[ChatMessageDisplay] Malformed XML detected - skipping update",
-                    )
-                    // Only show toast if this is the final XML (not during streaming)
+                    // Use console.warn instead of console.error to avoid triggering
+                    // Next.js dev mode error overlay for expected streaming states
+                    // (partial XML during streaming is normal and will be fixed by subsequent updates)
                     if (showToast) {
+                        // Only log as error and show toast if this is the final XML
+                        console.error(
+                            "[ChatMessageDisplay] Malformed XML detected in final output",
+                        )
                         toast.error(
                             "AI generated invalid diagram XML. Please try regenerating.",
                         )
@@ -364,7 +402,12 @@ export function ChatMessageDisplay({
     }, [editingMessageId])
 
     useEffect(() => {
-        messages.forEach((message) => {
+        // Only process the last message for streaming performance
+        // Previous messages are already processed and won't change
+        const messagesToProcess =
+            messages.length > 0 ? [messages[messages.length - 1]] : []
+
+        messagesToProcess.forEach((message) => {
             if (message.parts) {
                 message.parts.forEach((part) => {
                     if (part.type?.startsWith("tool-")) {
@@ -383,26 +426,194 @@ export function ChatMessageDisplay({
                             input?.xml
                         ) {
                             const xml = input.xml as string
+
+                            // Skip if XML hasn't changed since last processing
+                            const lastXml =
+                                lastProcessedXmlRef.current.get(toolCallId)
+                            if (lastXml === xml) {
+                                return // Skip redundant processing
+                            }
+
                             if (
                                 state === "input-streaming" ||
                                 state === "input-available"
                             ) {
-                                // During streaming, don't show toast (XML may be incomplete)
-                                handleDisplayChart(xml, false)
+                                // Debounce streaming updates - queue the XML and process after delay
+                                pendingXmlRef.current = xml
+
+                                if (!debounceTimeoutRef.current) {
+                                    // No pending timeout - set one up
+                                    debounceTimeoutRef.current = setTimeout(
+                                        () => {
+                                            const pendingXml =
+                                                pendingXmlRef.current
+                                            debounceTimeoutRef.current = null
+                                            pendingXmlRef.current = null
+                                            if (pendingXml) {
+                                                handleDisplayChart(
+                                                    pendingXml,
+                                                    false,
+                                                )
+                                                lastProcessedXmlRef.current.set(
+                                                    toolCallId,
+                                                    pendingXml,
+                                                )
+                                            }
+                                        },
+                                        STREAMING_DEBOUNCE_MS,
+                                    )
+                                }
                             } else if (
                                 state === "output-available" &&
                                 !processedToolCalls.current.has(toolCallId)
                             ) {
+                                // Final output - process immediately (clear any pending debounce)
+                                if (debounceTimeoutRef.current) {
+                                    clearTimeout(debounceTimeoutRef.current)
+                                    debounceTimeoutRef.current = null
+                                    pendingXmlRef.current = null
+                                }
                                 // Show toast only if final XML is malformed
                                 handleDisplayChart(xml, true)
                                 processedToolCalls.current.add(toolCallId)
+                                // Clean up the ref entry - tool is complete, no longer needed
+                                lastProcessedXmlRef.current.delete(toolCallId)
+                            }
+                        }
+
+                        // Handle edit_diagram streaming - apply operations incrementally for preview
+                        // Uses shared editDiagramOriginalXmlRef to coordinate with tool handler
+                        if (
+                            part.type === "tool-edit_diagram" &&
+                            input?.operations
+                        ) {
+                            const completeOps = getCompleteOperations(
+                                input.operations as DiagramOperation[],
+                            )
+
+                            if (completeOps.length === 0) return
+
+                            // Capture original XML when streaming starts (store in shared ref)
+                            if (
+                                !editDiagramOriginalXmlRef.current.has(
+                                    toolCallId,
+                                )
+                            ) {
+                                if (!chartXML) {
+                                    console.warn(
+                                        "[edit_diagram streaming] No chart XML available",
+                                    )
+                                    return
+                                }
+                                editDiagramOriginalXmlRef.current.set(
+                                    toolCallId,
+                                    chartXML,
+                                )
+                            }
+
+                            const originalXml =
+                                editDiagramOriginalXmlRef.current.get(
+                                    toolCallId,
+                                )
+                            if (!originalXml) return
+
+                            // Skip if no change from last processed state
+                            const lastCount = lastProcessedXmlRef.current.get(
+                                toolCallId + "-opCount",
+                            )
+                            if (lastCount === String(completeOps.length)) return
+
+                            if (
+                                state === "input-streaming" ||
+                                state === "input-available"
+                            ) {
+                                // Queue the operations for debounced processing
+                                pendingEditRef.current = {
+                                    operations: completeOps,
+                                    toolCallId,
+                                }
+
+                                if (!editDebounceTimeoutRef.current) {
+                                    editDebounceTimeoutRef.current = setTimeout(
+                                        () => {
+                                            const pending =
+                                                pendingEditRef.current
+                                            editDebounceTimeoutRef.current =
+                                                null
+                                            pendingEditRef.current = null
+
+                                            if (pending) {
+                                                const origXml =
+                                                    editDiagramOriginalXmlRef.current.get(
+                                                        pending.toolCallId,
+                                                    )
+                                                if (!origXml) return
+
+                                                try {
+                                                    const {
+                                                        result: editedXml,
+                                                    } = applyDiagramOperations(
+                                                        origXml,
+                                                        pending.operations,
+                                                    )
+                                                    handleDisplayChart(
+                                                        editedXml,
+                                                        false,
+                                                    )
+                                                    lastProcessedXmlRef.current.set(
+                                                        pending.toolCallId +
+                                                            "-opCount",
+                                                        String(
+                                                            pending.operations
+                                                                .length,
+                                                        ),
+                                                    )
+                                                } catch (e) {
+                                                    console.warn(
+                                                        `[edit_diagram streaming] Operation failed:`,
+                                                        e instanceof Error
+                                                            ? e.message
+                                                            : e,
+                                                    )
+                                                }
+                                            }
+                                        },
+                                        STREAMING_DEBOUNCE_MS,
+                                    )
+                                }
+                            } else if (
+                                state === "output-available" &&
+                                !processedToolCalls.current.has(toolCallId)
+                            ) {
+                                // Final state - cleanup streaming refs (tool handler does final application)
+                                if (editDebounceTimeoutRef.current) {
+                                    clearTimeout(editDebounceTimeoutRef.current)
+                                    editDebounceTimeoutRef.current = null
+                                }
+                                lastProcessedXmlRef.current.delete(
+                                    toolCallId + "-opCount",
+                                )
+                                processedToolCalls.current.add(toolCallId)
+                                // Note: Don't delete editDiagramOriginalXmlRef here - tool handler needs it
                             }
                         }
                     }
                 })
             }
         })
-    }, [messages, handleDisplayChart])
+
+        // Cleanup: clear any pending debounce timeout on unmount
+        return () => {
+            if (debounceTimeoutRef.current) {
+                clearTimeout(debounceTimeoutRef.current)
+                debounceTimeoutRef.current = null
+            }
+            if (editDebounceTimeoutRef.current) {
+                clearTimeout(editDebounceTimeoutRef.current)
+                editDebounceTimeoutRef.current = null
+            }
+        }
+    }, [messages, handleDisplayChart, chartXML])
 
     const renderToolPart = (part: ToolPartLike) => {
         const callId = part.toolCallId
@@ -451,11 +662,23 @@ export function ChatMessageDisplay({
                                 Complete
                             </span>
                         )}
-                        {state === "output-error" && (
-                            <span className="text-xs font-medium text-red-600 bg-red-50 px-2 py-0.5 rounded-full">
-                                Error
-                            </span>
-                        )}
+                        {state === "output-error" &&
+                            (() => {
+                                // Check if this is a truncation (incomplete XML) vs real error
+                                const isTruncated =
+                                    (toolName === "display_diagram" ||
+                                        toolName === "append_diagram") &&
+                                    !isMxCellXmlComplete(input?.xml)
+                                return isTruncated ? (
+                                    <span className="text-xs font-medium text-yellow-600 bg-yellow-50 px-2 py-0.5 rounded-full">
+                                        Truncated
+                                    </span>
+                                ) : (
+                                    <span className="text-xs font-medium text-red-600 bg-red-50 px-2 py-0.5 rounded-full">
+                                        Error
+                                    </span>
+                                )
+                            })()}
                         {input && Object.keys(input).length > 0 && (
                             <button
                                 type="button"
@@ -476,9 +699,9 @@ export function ChatMessageDisplay({
                         {typeof input === "object" && input.xml ? (
                             <CodeBlock code={input.xml} language="xml" />
                         ) : typeof input === "object" &&
-                          input.edits &&
-                          Array.isArray(input.edits) ? (
-                            <EditDiffDisplay edits={input.edits} />
+                          input.operations &&
+                          Array.isArray(input.operations) ? (
+                            <OperationsDisplay operations={input.operations} />
                         ) : typeof input === "object" &&
                           Object.keys(input).length > 0 ? (
                             <CodeBlock
@@ -488,11 +711,23 @@ export function ChatMessageDisplay({
                         ) : null}
                     </div>
                 )}
-                {output && state === "output-error" && (
-                    <div className="px-4 py-3 border-t border-border/40 text-sm text-red-600">
-                        {output}
-                    </div>
-                )}
+                {output &&
+                    state === "output-error" &&
+                    (() => {
+                        const isTruncated =
+                            (toolName === "display_diagram" ||
+                                toolName === "append_diagram") &&
+                            !isMxCellXmlComplete(input?.xml)
+                        return (
+                            <div
+                                className={`px-4 py-3 border-t border-border/40 text-sm ${isTruncated ? "text-yellow-600" : "text-red-600"}`}
+                            >
+                                {isTruncated
+                                    ? "Output truncated due to length limits. Try a simpler request or increase the maxOutputLength."
+                                    : output}
+                            </div>
+                        )
+                    })()}
             </div>
         )
     }

components/chat-panel.tsx

@@ -26,7 +26,7 @@ import { findCachedResponse } from "@/lib/cached-responses"
 import { isPdfFile, isTextFile } from "@/lib/pdf-utils"
 import { type FileData, useFileProcessor } from "@/lib/use-file-processor"
 import { useQuotaManager } from "@/lib/use-quota-manager"
-import { formatXML, wrapWithMxFile } from "@/lib/utils"
+import { formatXML, isMxCellXmlComplete, wrapWithMxFile } from "@/lib/utils"
 import { ChatMessageDisplay } from "./chat-message-display"
 
 // localStorage keys for persistence
@@ -40,6 +40,7 @@ interface MessagePart {
     type: string
     state?: string
     toolName?: string
+    input?: { xml?: string; [key: string]: unknown }
     [key: string]: unknown
 }
 
@@ -67,7 +68,7 @@ const MAX_AUTO_RETRY_COUNT = 1
 
 /**
  * Check if auto-resubmit should happen based on tool errors.
- * Does NOT handle retry count or quota - those are handled by the caller.
+ * Only checks the LAST tool part (most recent tool call), not all tool parts.
  */
 function hasToolErrors(messages: ChatMessage[]): boolean {
     const lastMessage = messages[messages.length - 1]
@@ -84,7 +85,8 @@ function hasToolErrors(messages: ChatMessage[]): boolean {
         return false
     }
 
-    return toolParts.some((part) => part.state === TOOL_ERROR_STATE)
+    const lastToolPart = toolParts[toolParts.length - 1]
+    return lastToolPart?.state === TOOL_ERROR_STATE
 }
 
 export default function ChatPanel({
@@ -144,6 +146,7 @@ export default function ChatPanel({
     const [dailyTokenLimit, setDailyTokenLimit] = useState(0)
     const [tpmLimit, setTpmLimit] = useState(0)
     const [showNewChatDialog, setShowNewChatDialog] = useState(false)
+    const [minimalStyle, setMinimalStyle] = useState(false)
 
     // Check config on mount
     useEffect(() => {
@@ -192,9 +195,26 @@ export default function ChatPanel({
     // Ref to track consecutive auto-retry count (reset on user action)
     const autoRetryCountRef = useRef(0)
 
+    // Ref to accumulate partial XML when output is truncated due to maxOutputTokens
+    // When partialXmlRef.current.length > 0, we're in continuation mode
+    const partialXmlRef = useRef<string>("")
+
     // Persist processed tool call IDs so collapsing the chat doesn't replay old tool outputs
     const processedToolCallsRef = useRef<Set<string>>(new Set())
 
+    // Store original XML for edit_diagram streaming - shared between streaming preview and tool handler
+    // Key: toolCallId, Value: original XML before any operations applied
+    const editDiagramOriginalXmlRef = useRef<Map<string, string>>(new Map())
+
+    // Debounce timeout for localStorage writes (prevents blocking during streaming)
+    const localStorageDebounceRef = useRef<ReturnType<
+        typeof setTimeout
+    > | null>(null)
+    const xmlStorageDebounceRef = useRef<ReturnType<typeof setTimeout> | null>(
+        null,
+    )
+    const LOCAL_STORAGE_DEBOUNCE_MS = 1000 // Save at most once per second
+
     const {
         messages,
         sendMessage,
@@ -216,14 +236,50 @@ export default function ChatPanel({
 
             if (toolCall.toolName === "display_diagram") {
                 const { xml } = toolCall.input as { xml: string }
-                if (DEBUG) {
-                    console.log(
-                        `[display_diagram] Received XML length: ${xml.length}`,
-                    )
+
+                // DEBUG: Log raw input to diagnose false truncation detection
+                console.log(
+                    "[display_diagram] XML ending (last 100 chars):",
+                    xml.slice(-100),
+                )
+                console.log("[display_diagram] XML length:", xml.length)
+
+                // Check if XML is truncated (incomplete mxCell indicates truncated output)
+                const isTruncated = !isMxCellXmlComplete(xml)
+                console.log("[display_diagram] isTruncated:", isTruncated)
+
+                if (isTruncated) {
+                    // Store the partial XML for continuation via append_diagram
+                    partialXmlRef.current = xml
+
+                    // Tell LLM to use append_diagram to continue
+                    const partialEnding = partialXmlRef.current.slice(-500)
+                    addToolOutput({
+                        tool: "display_diagram",
+                        toolCallId: toolCall.toolCallId,
+                        state: "output-error",
+                        errorText: `Output was truncated due to length limits. Use the append_diagram tool to continue.
+
+Your output ended with:
+\`\`\`
+${partialEnding}
+\`\`\`
+
+NEXT STEP: Call append_diagram with the continuation XML.
+- Do NOT include wrapper tags or root cells (id="0", id="1")
+- Start from EXACTLY where you stopped
+- Complete all remaining mxCell elements`,
+                    })
+                    return
                 }
 
+                // Complete XML received - use it directly
+                // (continuation is now handled via append_diagram tool)
+                const finalXml = xml
+                partialXmlRef.current = "" // Reset any partial from previous truncation
+
                 // Wrap raw XML with full mxfile structure for draw.io
-                const fullXml = wrapWithMxFile(xml)
+                const fullXml = wrapWithMxFile(finalXml)
 
                 // loadDiagram validates and returns error if invalid
                 const validationError = onDisplayChart(fullXml)
@@ -249,7 +305,7 @@ Please fix the XML issues and call display_diagram again with corrected XML.
 
 Your failed XML:
 \`\`\`xml
-${xml}
+${finalXml}
 \`\`\``,
                     })
                 } else {
@@ -271,37 +327,68 @@ ${xml}
                     }
                 }
             } else if (toolCall.toolName === "edit_diagram") {
-                const { edits } = toolCall.input as {
-                    edits: Array<{ search: string; replace: string }>
+                const { operations } = toolCall.input as {
+                    operations: Array<{
+                        type: "update" | "add" | "delete"
+                        cell_id: string
+                        new_xml?: 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,
-                        )
+                    // Use the original XML captured during streaming (shared with chat-message-display)
+                    // This ensures we apply operations to the same base XML that streaming used
+                    const originalXml = editDiagramOriginalXmlRef.current.get(
+                        toolCall.toolCallId,
+                    )
+                    if (originalXml) {
+                        currentXml = originalXml
                     } 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,
-                        )
+                        // Fallback: use chartXML from ref if streaming didn't capture original
+                        const cachedXML = chartXMLRef.current
+                        if (cachedXML) {
+                            currentXml = cachedXML
+                        } else {
+                            // Last resort: export from iframe
+                            currentXml = await onFetchChart(false)
+                        }
                     }
 
-                    const { replaceXMLParts } = await import("@/lib/utils")
-                    const editedXml = replaceXMLParts(currentXml, edits)
+                    const { applyDiagramOperations } = await import(
+                        "@/lib/utils"
+                    )
+                    const { result: editedXml, errors } =
+                        applyDiagramOperations(currentXml, operations)
+
+                    // Check for operation errors
+                    if (errors.length > 0) {
+                        const errorMessages = errors
+                            .map(
+                                (e) =>
+                                    `- ${e.type} on cell_id="${e.cellId}": ${e.message}`,
+                            )
+                            .join("\n")
+
+                        addToolOutput({
+                            tool: "edit_diagram",
+                            toolCallId: toolCall.toolCallId,
+                            state: "output-error",
+                            errorText: `Some operations failed:\n${errorMessages}
+
+Current diagram XML:
+\`\`\`xml
+${currentXml}
+\`\`\`
+
+Please check the cell IDs and retry.`,
+                        })
+                        // Clean up the shared original XML ref
+                        editDiagramOriginalXmlRef.current.delete(
+                            toolCall.toolCallId,
+                        )
+                        return
+                    }
 
                     // loadDiagram validates and returns error if invalid
                     const validationError = onDisplayChart(editedXml)
@@ -321,24 +408,30 @@ Current diagram XML:
 ${currentXml}
 \`\`\`
 
-Please fix the edit to avoid structural issues (e.g., duplicate IDs, invalid references).`,
+Please fix the operations to avoid structural issues.`,
                         })
+                        // Clean up the shared original XML ref
+                        editDiagramOriginalXmlRef.current.delete(
+                            toolCall.toolCallId,
+                        )
                         return
                     }
                     onExport()
                     addToolOutput({
                         tool: "edit_diagram",
                         toolCallId: toolCall.toolCallId,
-                        output: `Successfully applied ${edits.length} edit(s) to the diagram.`,
+                        output: `Successfully applied ${operations.length} operation(s) to the diagram.`,
                     })
-                    console.log("[edit_diagram] Success")
+                    // Clean up the shared original XML ref
+                    editDiagramOriginalXmlRef.current.delete(
+                        toolCall.toolCallId,
+                    )
                 } catch (error) {
                     console.error("[edit_diagram] Failed:", error)
 
                     const errorMessage =
                         error instanceof Error ? error.message : String(error)
 
-                    // Use addToolOutput with state: 'output-error' for proper error signaling
                     addToolOutput({
                         tool: "edit_diagram",
                         toolCallId: toolCall.toolCallId,
@@ -350,7 +443,92 @@ Current diagram XML:
 ${currentXml || "No XML available"}
 \`\`\`
 
-Please retry with an adjusted search pattern or use display_diagram if retries are exhausted.`,
+Please check cell IDs and retry, or use display_diagram to regenerate.`,
+                    })
+                    // Clean up the shared original XML ref even on error
+                    editDiagramOriginalXmlRef.current.delete(
+                        toolCall.toolCallId,
+                    )
+                }
+            } else if (toolCall.toolName === "append_diagram") {
+                const { xml } = toolCall.input as { xml: string }
+
+                // Detect if LLM incorrectly started fresh instead of continuing
+                // LLM should only output bare mxCells now, so wrapper tags indicate error
+                const trimmed = xml.trim()
+                const isFreshStart =
+                    trimmed.startsWith("<mxGraphModel") ||
+                    trimmed.startsWith("<root") ||
+                    trimmed.startsWith("<mxfile") ||
+                    trimmed.startsWith('<mxCell id="0"') ||
+                    trimmed.startsWith('<mxCell id="1"')
+
+                if (isFreshStart) {
+                    addToolOutput({
+                        tool: "append_diagram",
+                        toolCallId: toolCall.toolCallId,
+                        state: "output-error",
+                        errorText: `ERROR: You started fresh with wrapper tags. Do NOT include wrapper tags or root cells (id="0", id="1").
+
+Continue from EXACTLY where the partial ended:
+\`\`\`
+${partialXmlRef.current.slice(-500)}
+\`\`\`
+
+Start your continuation with the NEXT character after where it stopped.`,
+                    })
+                    return
+                }
+
+                // Append to accumulated XML
+                partialXmlRef.current += xml
+
+                // Check if XML is now complete (last mxCell is complete)
+                const isComplete = isMxCellXmlComplete(partialXmlRef.current)
+
+                if (isComplete) {
+                    // Wrap and display the complete diagram
+                    const finalXml = partialXmlRef.current
+                    partialXmlRef.current = "" // Reset
+
+                    const fullXml = wrapWithMxFile(finalXml)
+                    const validationError = onDisplayChart(fullXml)
+
+                    if (validationError) {
+                        addToolOutput({
+                            tool: "append_diagram",
+                            toolCallId: toolCall.toolCallId,
+                            state: "output-error",
+                            errorText: `Validation error after assembly: ${validationError}
+
+Assembled XML:
+\`\`\`xml
+${finalXml.substring(0, 2000)}...
+\`\`\`
+
+Please use display_diagram with corrected XML.`,
+                        })
+                    } else {
+                        addToolOutput({
+                            tool: "append_diagram",
+                            toolCallId: toolCall.toolCallId,
+                            output: "Diagram assembly complete and displayed successfully.",
+                        })
+                    }
+                } else {
+                    // Still incomplete - signal to continue
+                    addToolOutput({
+                        tool: "append_diagram",
+                        toolCallId: toolCall.toolCallId,
+                        state: "output-error",
+                        errorText: `XML still incomplete (mxCell not closed). Call append_diagram again to continue.
+
+Current ending:
+\`\`\`
+${partialXmlRef.current.slice(-500)}
+\`\`\`
+
+Continue from EXACTLY where you stopped.`,
                     })
                 }
             }
@@ -359,6 +537,32 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
             // Silence access code error in console since it's handled by UI
             if (!error.message.includes("Invalid or missing access code")) {
                 console.error("Chat error:", error)
+                // Debug: Log messages structure when error occurs
+                console.log("[onError] messages count:", messages.length)
+                messages.forEach((msg, idx) => {
+                    console.log(`[onError] Message ${idx}:`, {
+                        role: msg.role,
+                        partsCount: msg.parts?.length,
+                    })
+                    if (msg.parts) {
+                        msg.parts.forEach((part: any, partIdx: number) => {
+                            console.log(
+                                `[onError]   Part ${partIdx}:`,
+                                JSON.stringify({
+                                    type: part.type,
+                                    toolName: part.toolName,
+                                    hasInput: !!part.input,
+                                    inputType: typeof part.input,
+                                    inputKeys:
+                                        part.input &&
+                                        typeof part.input === "object"
+                                            ? Object.keys(part.input)
+                                            : null,
+                                }),
+                            )
+                        })
+                    }
+                })
             }
 
             // Translate technical errors into user-friendly messages
@@ -371,6 +575,12 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
                 friendlyMessage = "Network error. Please check your connection."
             }
 
+            // Truncated tool input error (model output limit too low)
+            if (friendlyMessage.includes("toolUse.input is invalid")) {
+                friendlyMessage =
+                    "Output was truncated before the diagram could be generated. Try a simpler request or increase the maxOutputLength."
+            }
+
             // Translate image not supported error
             if (friendlyMessage.includes("image content block")) {
                 friendlyMessage = "This model doesn't support image input."
@@ -398,6 +608,11 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
             const metadata = message?.metadata as
                 | Record<string, unknown>
                 | undefined
+
+            // DEBUG: Log finish reason to diagnose truncation
+            console.log("[onFinish] finishReason:", metadata?.finishReason)
+            console.log("[onFinish] metadata:", metadata)
+
             if (metadata) {
                 // Use Number.isFinite to guard against NaN (typeof NaN === 'number' is true)
                 const inputTokens = Number.isFinite(metadata.inputTokens)
@@ -414,65 +629,55 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
             }
         },
         sendAutomaticallyWhen: ({ messages }) => {
+            const isInContinuationMode = partialXmlRef.current.length > 0
+
             const shouldRetry = hasToolErrors(
                 messages as unknown as ChatMessage[],
             )
 
             if (!shouldRetry) {
-                // No error, reset retry count
+                // No error, reset retry count and clear state
                 autoRetryCountRef.current = 0
-                if (DEBUG) {
-                    console.log("[sendAutomaticallyWhen] No errors, stopping")
-                }
+                partialXmlRef.current = ""
                 return false
             }
 
-            // Check retry count limit
-            if (autoRetryCountRef.current >= MAX_AUTO_RETRY_COUNT) {
-                if (DEBUG) {
-                    console.log(
-                        `[sendAutomaticallyWhen] Max retry count (${MAX_AUTO_RETRY_COUNT}) reached, stopping`,
+            // Continuation mode: unlimited retries (truncation continuation, not real errors)
+            // Server limits to 5 steps via stepCountIs(5)
+            if (isInContinuationMode) {
+                // Don't count against retry limit for continuation
+                // Quota checks still apply below
+            } else {
+                // Regular error: check retry count limit
+                if (autoRetryCountRef.current >= MAX_AUTO_RETRY_COUNT) {
+                    toast.error(
+                        `Auto-retry limit reached (${MAX_AUTO_RETRY_COUNT}). Please try again manually.`,
                     )
+                    autoRetryCountRef.current = 0
+                    partialXmlRef.current = ""
+                    return false
                 }
-                toast.error(
-                    `Auto-retry limit reached (${MAX_AUTO_RETRY_COUNT}). Please try again manually.`,
-                )
-                autoRetryCountRef.current = 0
-                return false
+                // Increment retry count for actual errors
+                autoRetryCountRef.current++
             }
 
             // Check quota limits before auto-retry
             const tokenLimitCheck = quotaManager.checkTokenLimit()
             if (!tokenLimitCheck.allowed) {
-                if (DEBUG) {
-                    console.log(
-                        "[sendAutomaticallyWhen] Token limit exceeded, stopping",
-                    )
-                }
                 quotaManager.showTokenLimitToast(tokenLimitCheck.used)
                 autoRetryCountRef.current = 0
+                partialXmlRef.current = ""
                 return false
             }
 
             const tpmCheck = quotaManager.checkTPMLimit()
             if (!tpmCheck.allowed) {
-                if (DEBUG) {
-                    console.log(
-                        "[sendAutomaticallyWhen] TPM limit exceeded, stopping",
-                    )
-                }
                 quotaManager.showTPMLimitToast()
                 autoRetryCountRef.current = 0
+                partialXmlRef.current = ""
                 return false
             }
 
-            // Increment retry count and allow retry
-            autoRetryCountRef.current++
-            if (DEBUG) {
-                console.log(
-                    `[sendAutomaticallyWhen] Retrying (${autoRetryCountRef.current}/${MAX_AUTO_RETRY_COUNT})`,
-                )
-            }
             return true
         },
     })
@@ -513,6 +718,10 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
             }
         } catch (error) {
             console.error("Failed to restore from localStorage:", error)
+            // On complete failure, clear storage to allow recovery
+            localStorage.removeItem(STORAGE_MESSAGES_KEY)
+            localStorage.removeItem(STORAGE_XML_SNAPSHOTS_KEY)
+            toast.error("Session data was corrupted. Starting fresh.")
         }
     }, [setMessages])
 
@@ -557,21 +766,54 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
         }, 500)
     }, [isDrawioReady, onDisplayChart])
 
-    // Save messages to localStorage whenever they change
+    // Save messages to localStorage whenever they change (debounced to prevent blocking during streaming)
     useEffect(() => {
         if (!hasRestoredRef.current) return
-        try {
-            localStorage.setItem(STORAGE_MESSAGES_KEY, JSON.stringify(messages))
-        } catch (error) {
-            console.error("Failed to save messages to localStorage:", error)
+
+        // Clear any pending save
+        if (localStorageDebounceRef.current) {
+            clearTimeout(localStorageDebounceRef.current)
+        }
+
+        // Debounce: save after 1 second of no changes
+        localStorageDebounceRef.current = setTimeout(() => {
+            try {
+                localStorage.setItem(
+                    STORAGE_MESSAGES_KEY,
+                    JSON.stringify(messages),
+                )
+            } catch (error) {
+                console.error("Failed to save messages to localStorage:", error)
+            }
+        }, LOCAL_STORAGE_DEBOUNCE_MS)
+
+        // Cleanup on unmount
+        return () => {
+            if (localStorageDebounceRef.current) {
+                clearTimeout(localStorageDebounceRef.current)
+            }
         }
     }, [messages])
 
-    // Save diagram XML to localStorage whenever it changes
+    // Save diagram XML to localStorage whenever it changes (debounced)
     useEffect(() => {
         if (!canSaveDiagram) return
-        if (chartXML && chartXML.length > 300) {
+        if (!chartXML || chartXML.length <= 300) return
+
+        // Clear any pending save
+        if (xmlStorageDebounceRef.current) {
+            clearTimeout(xmlStorageDebounceRef.current)
+        }
+
+        // Debounce: save after 1 second of no changes
+        xmlStorageDebounceRef.current = setTimeout(() => {
             localStorage.setItem(STORAGE_DIAGRAM_XML_KEY, chartXML)
+        }, LOCAL_STORAGE_DEBOUNCE_MS)
+
+        return () => {
+            if (xmlStorageDebounceRef.current) {
+                clearTimeout(xmlStorageDebounceRef.current)
+            }
         }
     }, [chartXML, canSaveDiagram])
 
@@ -817,8 +1059,9 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
         previousXml: string,
         sessionId: string,
     ) => {
-        // Reset auto-retry count on user-initiated message
+        // Reset all retry/continuation state on user-initiated message
         autoRetryCountRef.current = 0
+        partialXmlRef.current = ""
 
         const config = getAIConfig()
 
@@ -838,6 +1081,9 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
                         }),
                         ...(config.aiModel && { "x-ai-model": config.aiModel }),
                     }),
+                    ...(minimalStyle && {
+                        "x-minimal-style": "true",
+                    }),
                 },
             },
         )
@@ -1023,6 +1269,7 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
                     style: {
                         maxWidth: "480px",
                     },
+                    duration: 2000,
                 }}
             />
             {/* Header */}
@@ -1128,6 +1375,7 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
                     setInput={setInput}
                     setFiles={handleFileChange}
                     processedToolCallsRef={processedToolCallsRef}
+                    editDiagramOriginalXmlRef={editDiagramOriginalXmlRef}
                     sessionId={sessionId}
                     onRegenerate={handleRegenerate}
                     status={status}
@@ -1152,6 +1400,8 @@ Please retry with an adjusted search pattern or use display_diagram if retries a
                     onToggleHistory={setShowHistory}
                     sessionId={sessionId}
                     error={error}
+                    minimalStyle={minimalStyle}
+                    onMinimalStyleChange={setMinimalStyle}
                 />
             </footer>
 

contexts/diagram-context.tsx

@@ -23,6 +23,7 @@ interface DiagramContextType {
         format: ExportFormat,
         sessionId?: string,
     ) => void
+    saveDiagramToStorage: () => Promise<void>
     isDrawioReady: boolean
     onDrawioLoad: () => void
     resetDrawioReady: () => void
@@ -82,6 +83,30 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
         }
     }
 
+    // Save current diagram to localStorage (used before theme/UI changes)
+    const saveDiagramToStorage = async (): Promise<void> => {
+        if (!drawioRef.current) return
+
+        try {
+            const currentXml = await Promise.race([
+                new Promise<string>((resolve) => {
+                    resolverRef.current = resolve
+                    drawioRef.current?.exportDiagram({ format: "xmlsvg" })
+                }),
+                new Promise<string>((_, reject) =>
+                    setTimeout(() => reject(new Error("Export timeout")), 2000),
+                ),
+            ])
+
+            // Only save if diagram has meaningful content (not empty template)
+            if (currentXml && currentXml.length > 300) {
+                localStorage.setItem(STORAGE_DIAGRAM_XML_KEY, currentXml)
+            }
+        } catch (error) {
+            console.error("Failed to save diagram to storage:", error)
+        }
+    }
+
     const loadDiagram = (
         chart: string,
         skipValidation?: boolean,
@@ -138,14 +163,20 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
         setLatestSvg(data.data)
 
         // Only add to history if this was a user-initiated export
+        // Limit to 20 entries to prevent memory leaks during long sessions
+        const MAX_HISTORY_SIZE = 20
         if (expectHistoryExportRef.current) {
-            setDiagramHistory((prev) => [
-                ...prev,
-                {
-                    svg: data.data,
-                    xml: extractedXML,
-                },
-            ])
+            setDiagramHistory((prev) => {
+                const newHistory = [
+                    ...prev,
+                    {
+                        svg: data.data,
+                        xml: extractedXML,
+                    },
+                ]
+                // Keep only the last MAX_HISTORY_SIZE entries (circular buffer)
+                return newHistory.slice(-MAX_HISTORY_SIZE)
+            })
             expectHistoryExportRef.current = false
         }
 
@@ -274,6 +305,7 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
                 handleDiagramExport,
                 clearDiagram,
                 saveDiagramToFile,
+                saveDiagramToStorage,
                 isDrawioReady,
                 onDrawioLoad,
                 resetDrawioReady,

docs/README_CN.md

@@ -26,6 +26,7 @@ https://github.com/user-attachments/assets/b2eef5f3-b335-4e71-a755-dc2e80931979
   - [目录](#目录)
   - [示例](#示例)
   - [功能特性](#功能特性)
+  - [MCP服务器（预览）](#mcp服务器预览)
   - [快速开始](#快速开始)
     - [在线试用](#在线试用)
     - [使用Docker运行（推荐）](#使用docker运行推荐)
@@ -88,6 +89,36 @@ https://github.com/user-attachments/assets/b2eef5f3-b335-4e71-a755-dc2e80931979
 -   **云架构图支持**：专门支持生成云架构图（AWS、GCP、Azure）
 -   **动画连接器**：在图表元素之间创建动态动画连接器，实现更好的可视化效果
 
+## MCP服务器（预览）
+
+> **预览功能**：此功能为实验性功能，可能会有变化。
+
+通过MCP（模型上下文协议）在Claude Desktop、Cursor和VS Code等AI代理中使用Next AI Draw.io。
+
+```json
+{
+  "mcpServers": {
+    "drawio": {
+      "command": "npx",
+      "args": ["@next-ai-drawio/mcp-server@latest"]
+    }
+  }
+}
+```
+
+### Claude Code CLI
+
+```bash
+claude mcp add drawio -- npx @next-ai-drawio/mcp-server@latest
+```
+
+然后让Claude创建图表：
+> "创建一个展示用户认证流程的流程图，包含登录、MFA和会话管理"
+
+图表会实时显示在浏览器中！
+
+详情请参阅[MCP服务器README](../packages/mcp-server/README.md)，了解VS Code、Cursor等客户端配置。
+
 ## 快速开始
 
 ### 在线试用

docs/README_JA.md

@@ -26,6 +26,7 @@ https://github.com/user-attachments/assets/b2eef5f3-b335-4e71-a755-dc2e80931979
   - [目次](#目次)
   - [例](#例)
   - [機能](#機能)
+  - [MCPサーバー（プレビュー）](#mcpサーバープレビュー)
   - [はじめに](#はじめに)
     - [オンラインで試す](#オンラインで試す)
     - [Dockerで実行（推奨）](#dockerで実行推奨)
@@ -88,6 +89,36 @@ https://github.com/user-attachments/assets/b2eef5f3-b335-4e71-a755-dc2e80931979
 -   **クラウドアーキテクチャダイアグラムサポート**：クラウドアーキテクチャダイアグラムの生成を専門的にサポート（AWS、GCP、Azure）
 -   **アニメーションコネクタ**：より良い可視化のためにダイアグラム要素間に動的でアニメーション化されたコネクタを作成
 
+## MCPサーバー（プレビュー）
+
+> **プレビュー機能**：この機能は実験的であり、変更される可能性があります。
+
+MCP（Model Context Protocol）を介して、Claude Desktop、Cursor、VS CodeなどのAIエージェントでNext AI Draw.ioを使用できます。
+
+```json
+{
+  "mcpServers": {
+    "drawio": {
+      "command": "npx",
+      "args": ["@next-ai-drawio/mcp-server@latest"]
+    }
+  }
+}
+```
+
+### Claude Code CLI
+
+```bash
+claude mcp add drawio -- npx @next-ai-drawio/mcp-server@latest
+```
+
+Claudeにダイアグラムの作成を依頼：
+> 「ログイン、MFA、セッション管理を含むユーザー認証のフローチャートを作成してください」
+
+ダイアグラムがリアルタイムでブラウザに表示されます！
+
+詳細は[MCPサーバーREADME](../packages/mcp-server/README.md)をご覧ください（VS Code、Cursorなどのクライアント設定も含む）。
+
 ## はじめに
 
 ### オンラインで試す

docs/ai-providers.md

@@ -136,6 +136,23 @@ Optional custom URL:
 OLLAMA_BASE_URL=http://localhost:11434
 ```
 
+### Vercel AI Gateway
+
+Vercel AI Gateway provides unified access to multiple AI providers through a single API key. This simplifies authentication and allows you to switch between providers without managing multiple API keys.
+
+```bash
+AI_GATEWAY_API_KEY=your_gateway_api_key
+AI_MODEL=openai/gpt-4o
+```
+
+Model format uses `provider/model` syntax:
+
+-   `openai/gpt-4o` - OpenAI GPT-4o
+-   `anthropic/claude-sonnet-4-5` - Anthropic Claude Sonnet 4.5
+-   `google/gemini-2.0-flash` - Google Gemini 2.0 Flash
+
+Get your API key from the [Vercel AI Gateway dashboard](https://vercel.com/ai-gateway).
+
 ## Auto-Detection
 
 If you only configure **one** provider's API key, the system will automatically detect and use that provider. No need to set `AI_PROVIDER`.
@@ -143,7 +160,7 @@ If you only configure **one** provider's API key, the system will automatically
 If you configure **multiple** API keys, you must explicitly set `AI_PROVIDER`:
 
 ```bash
-AI_PROVIDER=google  # or: openai, anthropic, deepseek, siliconflow, azure, bedrock, openrouter, ollama
+AI_PROVIDER=google  # or: openai, anthropic, deepseek, siliconflow, azure, bedrock, openrouter, ollama, gateway
 ```
 
 ## Model Capability Requirements

env.example

@@ -1,6 +1,6 @@
 # AI Provider Configuration
 # AI_PROVIDER: Which provider to use
-# Options: bedrock, openai, anthropic, google, azure, ollama, openrouter, deepseek, siliconflow
+# Options: bedrock, openai, anthropic, google, azure, ollama, openrouter, deepseek, siliconflow, gateway
 # Default: bedrock
 AI_PROVIDER=bedrock
 
@@ -68,6 +68,11 @@ AI_MODEL=global.anthropic.claude-sonnet-4-5-20250929-v1:0
 # SILICONFLOW_API_KEY=sk-...
 # SILICONFLOW_BASE_URL=https://api.siliconflow.com/v1  # Optional: switch to https://api.siliconflow.cn/v1 if needed
 
+# Vercel AI Gateway Configuration
+# Get your API key from: https://vercel.com/ai-gateway
+# Model format: "provider/model" e.g., "openai/gpt-4o", "anthropic/claude-sonnet-4-5"
+# AI_GATEWAY_API_KEY=...
+
 # Langfuse Observability (Optional)
 # Enable LLM tracing and analytics - https://langfuse.com
 # LANGFUSE_PUBLIC_KEY=pk-lf-...

lib/ai-providers.ts

@@ -2,6 +2,7 @@ import { createAmazonBedrock } from "@ai-sdk/amazon-bedrock"
 import { createAnthropic } from "@ai-sdk/anthropic"
 import { azure, createAzure } from "@ai-sdk/azure"
 import { createDeepSeek, deepseek } from "@ai-sdk/deepseek"
+import { gateway } from "@ai-sdk/gateway"
 import { createGoogleGenerativeAI, google } from "@ai-sdk/google"
 import { createOpenAI, openai } from "@ai-sdk/openai"
 import { fromNodeProviderChain } from "@aws-sdk/credential-providers"
@@ -18,6 +19,7 @@ export type ProviderName =
     | "openrouter"
     | "deepseek"
     | "siliconflow"
+    | "gateway"
 
 interface ModelConfig {
     model: any
@@ -42,6 +44,7 @@ const ALLOWED_CLIENT_PROVIDERS: ProviderName[] = [
     "openrouter",
     "deepseek",
     "siliconflow",
+    "gateway",
 ]
 
 // Bedrock provider options for Anthropic beta features
@@ -333,8 +336,10 @@ function buildProviderOptions(
 
         case "deepseek":
         case "openrouter":
-        case "siliconflow": {
+        case "siliconflow":
+        case "gateway": {
             // These providers don't have reasoning configs in AI SDK yet
+            // Gateway passes through to underlying providers which handle their own configs
             break
         }
 
@@ -356,6 +361,7 @@ const PROVIDER_ENV_VARS: Record<ProviderName, string | null> = {
     openrouter: "OPENROUTER_API_KEY",
     deepseek: "DEEPSEEK_API_KEY",
     siliconflow: "SILICONFLOW_API_KEY",
+    gateway: "AI_GATEWAY_API_KEY",
 }
 
 /**
@@ -438,6 +444,16 @@ function validateProviderCredentials(provider: ProviderName): void {
  * - SILICONFLOW_BASE_URL: SiliconFlow endpoint (optional, defaults to https://api.siliconflow.com/v1)
  */
 export function getAIModel(overrides?: ClientOverrides): ModelConfig {
+    // SECURITY: Prevent SSRF attacks (GHSA-9qf7-mprq-9qgm)
+    // If a custom baseUrl is provided, an API key MUST also be provided.
+    // This prevents attackers from redirecting server API keys to malicious endpoints.
+    if (overrides?.baseUrl && !overrides?.apiKey) {
+        throw new Error(
+            `API key is required when using a custom base URL. ` +
+                `Please provide your own API key in Settings.`,
+        )
+    }
+
     // Check if client is providing their own provider override
     const isClientOverride = !!(overrides?.provider && overrides?.apiKey)
 
@@ -485,6 +501,7 @@ export function getAIModel(overrides?: ClientOverrides): ModelConfig {
             if (configured.length === 0) {
                 throw new Error(
                     `No AI provider configured. Please set one of the following API keys in your .env.local file:\n` +
+                        `- AI_GATEWAY_API_KEY for Vercel AI Gateway\n` +
                         `- DEEPSEEK_API_KEY for DeepSeek\n` +
                         `- OPENAI_API_KEY for OpenAI\n` +
                         `- ANTHROPIC_API_KEY for Anthropic\n` +
@@ -662,9 +679,17 @@ export function getAIModel(overrides?: ClientOverrides): ModelConfig {
             break
         }
 
+        case "gateway": {
+            // Vercel AI Gateway - unified access to multiple AI providers
+            // Model format: "provider/model" e.g., "openai/gpt-4o", "anthropic/claude-sonnet-4-5"
+            // See: https://vercel.com/ai-gateway
+            model = gateway(modelId)
+            break
+        }
+
         default:
             throw new Error(
-                `Unknown AI provider: ${provider}. Supported providers: bedrock, openai, anthropic, google, azure, ollama, openrouter, deepseek, siliconflow`,
+                `Unknown AI provider: ${provider}. Supported providers: bedrock, openai, anthropic, google, azure, ollama, openrouter, deepseek, siliconflow, gateway`,
             )
     }
 

lib/cached-responses.ts

@@ -9,12 +9,7 @@ export const CACHED_EXAMPLE_RESPONSES: CachedResponse[] = [
         promptText:
             "Give me a **animated connector** diagram of transformer's architecture",
         hasImage: false,
-        xml: `<root>
-  <mxCell id="0"/>
-  <mxCell id="1" parent="0"/>
-
-
-  <mxCell id="title" value="Transformer Architecture" style="text;html=1;strokeColor=none;fillColor=none;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;fontSize=20;fontStyle=1;" vertex="1" parent="1">
+        xml: `<mxCell id="title" value="Transformer Architecture" style="text;html=1;strokeColor=none;fillColor=none;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;fontSize=20;fontStyle=1;" vertex="1" parent="1">
     <mxGeometry x="300" y="20" width="250" height="30" as="geometry"/>
   </mxCell>
 
@@ -254,18 +249,12 @@ export const CACHED_EXAMPLE_RESPONSES: CachedResponse[] = [
 
   <mxCell id="output_label" value="Outputs&#xa;(shifted right)" style="text;html=1;strokeColor=none;fillColor=none;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;fontSize=12;fontStyle=1;" vertex="1" parent="1">
     <mxGeometry x="660" y="530" width="100" height="30" as="geometry"/>
-  </mxCell>
-</root>`,
+  </mxCell>`,
     },
     {
         promptText: "Replicate this in aws style",
         hasImage: true,
-        xml: `<root>
-  <mxCell id="0"/>
-  <mxCell id="1" parent="0"/>
-
-
-  <mxCell id="2" value="AWS" style="sketch=0;outlineConnect=0;gradientColor=none;html=1;whiteSpace=wrap;fontSize=12;fontStyle=0;container=1;pointerEvents=0;collapsible=0;recursiveResize=0;shape=mxgraph.aws4.group;grIcon=mxgraph.aws4.group_aws_cloud;strokeColor=#232F3E;fillColor=none;verticalAlign=top;align=left;spacingLeft=30;fontColor=#232F3E;dashed=0;rounded=1;arcSize=5;" vertex="1" parent="1">
+        xml: `<mxCell id="2" value="AWS" style="sketch=0;outlineConnect=0;gradientColor=none;html=1;whiteSpace=wrap;fontSize=12;fontStyle=0;container=1;pointerEvents=0;collapsible=0;recursiveResize=0;shape=mxgraph.aws4.group;grIcon=mxgraph.aws4.group_aws_cloud;strokeColor=#232F3E;fillColor=none;verticalAlign=top;align=left;spacingLeft=30;fontColor=#232F3E;dashed=0;rounded=1;arcSize=5;" vertex="1" parent="1">
     <mxGeometry x="340" y="40" width="880" height="520" as="geometry"/>
   </mxCell>
 
@@ -324,18 +313,12 @@ export const CACHED_EXAMPLE_RESPONSES: CachedResponse[] = [
       <mxPoint x="700" y="350" as="sourcePoint"/>
       <mxPoint x="750" y="300" as="targetPoint"/>
     </mxGeometry>
-  </mxCell>
-</root>`,
+  </mxCell>`,
     },
     {
         promptText: "Replicate this flowchart.",
         hasImage: true,
-        xml: `<root>
-  <mxCell id="0"/>
-  <mxCell id="1" parent="0"/>
-
-
-  <mxCell id="2" value="Lamp doesn't work" style="rounded=1;whiteSpace=wrap;html=1;fillColor=#ffcccc;strokeColor=#000000;strokeWidth=2;fontSize=18;fontStyle=0;" vertex="1" parent="1">
+        xml: `<mxCell id="2" value="Lamp doesn't work" style="rounded=1;whiteSpace=wrap;html=1;fillColor=#ffcccc;strokeColor=#000000;strokeWidth=2;fontSize=18;fontStyle=0;" vertex="1" parent="1">
     <mxGeometry x="140" y="40" width="180" height="60" as="geometry"/>
   </mxCell>
 
@@ -391,16 +374,12 @@ export const CACHED_EXAMPLE_RESPONSES: CachedResponse[] = [
 
   <mxCell id="12" value="Repair lamp" style="rounded=1;whiteSpace=wrap;html=1;fillColor=#99ff99;strokeColor=#000000;strokeWidth=2;fontSize=18;fontStyle=0;" vertex="1" parent="1">
     <mxGeometry x="130" y="650" width="200" height="60" as="geometry"/>
-  </mxCell>
-</root>`,
+  </mxCell>`,
     },
     {
         promptText: "Summarize this paper as a diagram",
         hasImage: true,
-        xml: `            <root>
-                <mxCell id="0" />
-                <mxCell id="1" parent="0" />
-                <mxCell id="title_bg" parent="1"
+        xml: `<mxCell id="title_bg" parent="1"
                     style="rounded=1;whiteSpace=wrap;html=1;fillColor=#1a237e;strokeColor=none;arcSize=8;"
                     value="" vertex="1">
                     <mxGeometry height="80" width="720" x="40" y="20" as="geometry" />
@@ -751,18 +730,12 @@ export const CACHED_EXAMPLE_RESPONSES: CachedResponse[] = [
                     value="Foundational technique for modern LLM reasoning - inspired many follow-up works including Self-Consistency, Tree-of-Thought, etc."
                     vertex="1">
                     <mxGeometry height="55" width="230" x="530" y="600" as="geometry" />
-                </mxCell>
-            </root>`,
+                </mxCell>`,
     },
     {
         promptText: "Draw a cat for me",
         hasImage: false,
-        xml: `<root>
-  <mxCell id="0"/>
-  <mxCell id="1" parent="0"/>
-
-
-  <mxCell id="2" value="" style="ellipse;whiteSpace=wrap;html=1;aspect=fixed;fillColor=#FFE6CC;strokeColor=#000000;strokeWidth=2;" vertex="1" parent="1">
+        xml: `<mxCell id="2" value="" style="ellipse;whiteSpace=wrap;html=1;aspect=fixed;fillColor=#FFE6CC;strokeColor=#000000;strokeWidth=2;" vertex="1" parent="1">
     <mxGeometry x="300" y="150" width="120" height="120" as="geometry"/>
   </mxCell>
 
@@ -902,9 +875,7 @@ export const CACHED_EXAMPLE_RESPONSES: CachedResponse[] = [
         <mxPoint x="235" y="290"/>
       </Array>
     </mxGeometry>
-  </mxCell>
-
-</root>`,
+  </mxCell>`,
     },
 ]
 

lib/system-prompts.ts

@@ -42,11 +42,18 @@ description: Edit specific parts of the EXISTING diagram. Use this when making s
 parameters: {
   edits: Array<{search: string, replace: string}>
 }
+---Tool3---
+tool name: append_diagram
+description: Continue generating diagram XML when display_diagram was truncated due to output length limits. Only use this after display_diagram truncation.
+parameters: {
+  xml: string  // Continuation fragment (NO wrapper tags like <mxGraphModel> or <root>)
+}
 ---End of tools---
 
 IMPORTANT: Choose the right tool:
 - Use display_diagram for: Creating new diagrams, major restructuring, or when the current diagram XML is empty
 - Use edit_diagram for: Small modifications, adding/removing elements, changing text/colors, repositioning items
+- Use append_diagram for: ONLY when display_diagram was truncated due to output length - continue generating from where you stopped
 
 Core capabilities:
 - Generate valid, well-formed XML strings for draw.io diagrams
@@ -81,38 +88,33 @@ Note that:
 - NEVER include XML comments (<!-- ... -->) in your generated XML. Draw.io strips comments, which breaks edit_diagram patterns.
 
 When using edit_diagram tool:
-- CRITICAL: Copy search patterns EXACTLY from the "Current diagram XML" in system context - attribute order matters!
-- Always include the element's id attribute for unique targeting: {"search": "<mxCell id=\\"5\\"", ...}
-- Include complete elements (mxCell + mxGeometry) for reliable matching
-- Preserve exact whitespace, indentation, and line breaks
-- BAD: {"search": "value=\\"Label\\"", ...} - too vague, matches multiple elements
-- GOOD: {"search": "<mxCell id=\\"3\\" value=\\"Old\\" style=\\"...\\">", "replace": "<mxCell id=\\"3\\" value=\\"New\\" style=\\"...\\">"}
-- For multiple changes, use separate edits in array
-- RETRY POLICY: If pattern not found, retry up to 3 times with adjusted patterns. After 3 failures, use display_diagram instead.
+- Use operations: update (modify cell by id), add (new cell), delete (remove cell by id)
+- For update/add: provide cell_id and complete new_xml (full mxCell element including mxGeometry)
+- For delete: only cell_id is needed
+- Find the cell_id from "Current diagram XML" in system context
+- Example update: {"operations": [{"type": "update", "cell_id": "3", "new_xml": "<mxCell id=\\"3\\" value=\\"New Label\\" style=\\"rounded=1;\\" vertex=\\"1\\" parent=\\"1\\">\\n  <mxGeometry x=\\"100\\" y=\\"100\\" width=\\"120\\" height=\\"60\\" as=\\"geometry\\"/>\\n</mxCell>"}]}
+- Example delete: {"operations": [{"type": "delete", "cell_id": "5"}]}
+- Example add: {"operations": [{"type": "add", "cell_id": "new1", "new_xml": "<mxCell id=\\"new1\\" value=\\"New Box\\" style=\\"rounded=1;\\" vertex=\\"1\\" parent=\\"1\\">\\n  <mxGeometry x=\\"400\\" y=\\"200\\" width=\\"120\\" height=\\"60\\" as=\\"geometry\\"/>\\n</mxCell>"}]}
 
-⚠️ CRITICAL JSON ESCAPING: When outputting edit_diagram tool calls, you MUST escape ALL double quotes inside string values:
-- CORRECT: "y=\\"119\\""  (both quotes escaped)
-- WRONG: "y="119\\""  (missing backslash before first quote - causes JSON parse error!)
-- Every " inside a JSON string value needs \\" - no exceptions!
+⚠️ JSON ESCAPING: Every " inside new_xml MUST be escaped as \\". Example: id=\\"5\\" value=\\"Label\\"
 
 ## Draw.io XML Structure Reference
 
-Basic structure:
+**IMPORTANT:** You only generate the mxCell elements. The wrapper structure and root cells (id="0", id="1") are added automatically.
+
+Example - generate ONLY this:
 \`\`\`xml
-<mxGraphModel>
-  <root>
-    <mxCell id="0"/>
-    <mxCell id="1" parent="0"/>
-  </root>
-</mxGraphModel>
+<mxCell id="2" value="Label" style="rounded=1;" vertex="1" parent="1">
+  <mxGeometry x="100" y="100" width="120" height="60" as="geometry"/>
+</mxCell>
 \`\`\`
-Note: All other mxCell elements go as siblings after id="1".
 
 CRITICAL RULES:
-1. Always include the two root cells: <mxCell id="0"/> and <mxCell id="1" parent="0"/>
-2. ALL mxCell elements must be DIRECT children of <root> - NEVER nest mxCell inside another mxCell
-3. Use unique sequential IDs for all cells (start from "2" for user content)
-4. Set parent="1" for top-level shapes, or parent="<container-id>" for grouped elements
+1. Generate ONLY mxCell elements - NO wrapper tags (<mxfile>, <mxGraphModel>, <root>)
+2. Do NOT include root cells (id="0" or id="1") - they are added automatically
+3. ALL mxCell elements must be siblings - NEVER nest mxCell inside another mxCell
+4. Use unique sequential IDs starting from "2"
+5. Set parent="1" for top-level shapes, or parent="<container-id>" for grouped elements
 
 Shape (vertex) example:
 \`\`\`xml
@@ -126,122 +128,6 @@ Connector (edge) example:
 <mxCell id="3" style="endArrow=classic;html=1;" edge="1" parent="1" source="2" target="4">
   <mxGeometry relative="1" as="geometry"/>
 </mxCell>
-\`\`\`
-
-Common styles:
-- Shapes: rounded=1 (rounded corners), fillColor=#hex, strokeColor=#hex
-- Edges: endArrow=classic/block/open/none, startArrow=none/classic, curved=1, edgeStyle=orthogonalEdgeStyle
-- Text: fontSize=14, fontStyle=1 (bold), align=center/left/right
-
-`
-
-// Extended additions (~2600 tokens) - appended for models with 4000 token cache minimum
-// Total EXTENDED_SYSTEM_PROMPT = ~4400 tokens
-const EXTENDED_ADDITIONS = `
-
-## Extended Tool Reference
-
-### display_diagram Details
-
-**VALIDATION RULES** (XML will be rejected if violated):
-1. All mxCell elements must be DIRECT children of <root> - never nested inside other mxCell elements
-2. Every mxCell needs a unique id attribute
-3. Every mxCell (except id="0") needs a valid parent attribute referencing an existing cell
-4. Edge source/target attributes must reference existing cell IDs
-5. Escape special characters in values: &lt; for <, &gt; for >, &amp; for &, &quot; for "
-6. Always start with the two root cells: <mxCell id="0"/><mxCell id="1" parent="0"/>
-
-**Example with swimlanes and edges** (note: all mxCells are siblings under <root>):
-\`\`\`xml
-<root>
-  <mxCell id="0"/>
-  <mxCell id="1" parent="0"/>
-  <mxCell id="lane1" value="Frontend" style="swimlane;" vertex="1" parent="1">
-    <mxGeometry x="40" y="40" width="200" height="200" as="geometry"/>
-  </mxCell>
-  <mxCell id="step1" value="Step 1" style="rounded=1;" vertex="1" parent="lane1">
-    <mxGeometry x="20" y="60" width="160" height="40" as="geometry"/>
-  </mxCell>
-  <mxCell id="lane2" value="Backend" style="swimlane;" vertex="1" parent="1">
-    <mxGeometry x="280" y="40" width="200" height="200" as="geometry"/>
-  </mxCell>
-  <mxCell id="step2" value="Step 2" style="rounded=1;" vertex="1" parent="lane2">
-    <mxGeometry x="20" y="60" width="160" height="40" as="geometry"/>
-  </mxCell>
-  <mxCell id="edge1" style="edgeStyle=orthogonalEdgeStyle;endArrow=classic;" edge="1" parent="1" source="step1" target="step2">
-    <mxGeometry relative="1" as="geometry"/>
-  </mxCell>
-</root>
-\`\`\`
-
-### edit_diagram Details
-
-**CRITICAL RULES:**
-- Copy-paste the EXACT search pattern from the "Current diagram XML" in system context
-- Do NOT reorder attributes or reformat - the attribute order in draw.io XML varies and you MUST match it exactly
-- Only include the lines that are changing, plus 1-2 surrounding lines for context if needed
-- Break large changes into multiple smaller edits
-- Each search must contain complete lines (never truncate mid-line)
-- First match only - be specific enough to target the right element
-
-**Input Format:**
-\`\`\`json
-{
-  "edits": [
-    {
-      "search": "EXACT lines copied from current XML (preserve attribute order!)",
-      "replace": "Replacement lines"
-    }
-  ]
-}
-\`\`\`
-
-## edit_diagram Best Practices
-
-### Core Principle: Unique & Precise Patterns
-Your search pattern MUST uniquely identify exactly ONE location in the XML. Before writing a search pattern:
-1. Review the "Current diagram XML" in the system context
-2. Identify the exact element(s) to modify by their unique id attribute
-3. Include enough context to ensure uniqueness
-
-### Pattern Construction Rules
-
-**Rule 1: Always include the element's id attribute**
-\`\`\`json
-{"search": "<mxCell id=\\"node5\\"", "replace": "<mxCell id=\\"node5\\" value=\\"New Label\\""}
-\`\`\`
-
-**Rule 2: Include complete XML elements when possible**
-\`\`\`json
-{
-  "search": "<mxCell id=\\"3\\" value=\\"Old\\" style=\\"rounded=1;\\" vertex=\\"1\\" parent=\\"1\\">\\n  <mxGeometry x=\\"100\\" y=\\"100\\" width=\\"120\\" height=\\"60\\" as=\\"geometry\\"/>\\n</mxCell>",
-  "replace": "<mxCell id=\\"3\\" value=\\"New\\" style=\\"rounded=1;\\" vertex=\\"1\\" parent=\\"1\\">\\n  <mxGeometry x=\\"100\\" y=\\"100\\" width=\\"120\\" height=\\"60\\" as=\\"geometry\\"/>\\n</mxCell>"
-}
-\`\`\`
-
-**Rule 3: Preserve exact whitespace and formatting**
-Copy the search pattern EXACTLY from the current XML, including leading spaces, line breaks (\\n), and attribute order.
-
-### Good vs Bad Patterns
-
-**BAD:** \`{"search": "value=\\"Label\\""}\` - Too vague, matches multiple elements
-**BAD:** \`{"search": "<mxCell value=\\"X\\" id=\\"5\\""}\` - Reordered attributes won't match
-**GOOD:** \`{"search": "<mxCell id=\\"5\\" parent=\\"1\\" style=\\"...\\" value=\\"Old\\" vertex=\\"1\\">"}\` - Uses unique id with full context
-
-### ⚠️ JSON Escaping (CRITICAL)
-Every double quote inside JSON string values MUST be escaped with backslash:
-- **CORRECT:** \`"x=\\"100\\" y=\\"200\\""\` - both quotes escaped
-- **WRONG:** \`"x=\\"100\\" y="200\\""\` - missing backslash causes JSON parse error!
-
-### Error Recovery
-If edit_diagram fails with "pattern not found":
-1. **First retry**: Check attribute order - copy EXACTLY from current XML
-2. **Second retry**: Expand context - include more surrounding lines
-3. **Third retry**: Try matching on just \`<mxCell id="X"\` prefix + full replacement
-4. **After 3 failures**: Fall back to display_diagram to regenerate entire diagram
-
-
-
 
 ### Edge Routing Rules:
 When creating edges/connectors, you MUST follow these rules to avoid overlapping lines:
@@ -291,6 +177,135 @@ When creating edges/connectors, you MUST follow these rules to avoid overlapping
 3. "Are any connection points at corners (both X and Y are 0 or 1)?" → If yes, use edge centers instead
 4. "Could I rearrange shapes to reduce edge crossings?" → If yes, revise layout
 
+
+\`\`\`
+
+`
+
+// Style instructions - only included when minimalStyle is false
+const STYLE_INSTRUCTIONS = `
+Common styles:
+- Shapes: rounded=1 (rounded corners), fillColor=#hex, strokeColor=#hex
+- Edges: endArrow=classic/block/open/none, startArrow=none/classic, curved=1, edgeStyle=orthogonalEdgeStyle
+- Text: fontSize=14, fontStyle=1 (bold), align=center/left/right
+`
+
+// Minimal style instruction - skip styling and focus on layout (prepended to prompt for emphasis)
+const MINIMAL_STYLE_INSTRUCTION = `
+## ⚠️ MINIMAL STYLE MODE ACTIVE ⚠️
+
+### No Styling - Plain Black/White Only
+- NO fillColor, NO strokeColor, NO rounded, NO fontSize, NO fontStyle
+- NO color attributes (no hex colors like #ff69b4)
+- Style: "whiteSpace=wrap;html=1;" for shapes, "html=1;endArrow=classic;" for edges
+- IGNORE all color/style examples below
+
+### Container/Group Shapes - MUST be Transparent
+- For container shapes (boxes that contain other shapes): use "fillColor=none;" to make background transparent
+- This prevents containers from covering child elements
+- Example: style="whiteSpace=wrap;html=1;fillColor=none;" for container rectangles
+
+### Focus on Layout Quality
+Since we skip styling, STRICTLY follow the "Edge Routing Rules" section below:
+- SPACING: Minimum 50px gap between all elements
+- NO OVERLAPS: Elements and edges must never overlap
+- Follow ALL 7 Edge Routing Rules for arrow positioning
+- Use waypoints to route edges AROUND obstacles
+- Use different exitY/entryY values for multiple edges between same nodes
+
+`
+
+// Extended additions (~2600 tokens) - appended for models with 4000 token cache minimum
+// Total EXTENDED_SYSTEM_PROMPT = ~4400 tokens
+const EXTENDED_ADDITIONS = `
+
+## Extended Tool Reference
+
+### display_diagram Details
+
+**VALIDATION RULES** (XML will be rejected if violated):
+1. Generate ONLY mxCell elements - wrapper tags and root cells are added automatically
+2. All mxCell elements must be siblings - never nested inside other mxCell elements
+3. Every mxCell needs a unique id attribute (start from "2")
+4. Every mxCell needs a valid parent attribute (use "1" for top-level, or container-id for grouped)
+5. Edge source/target attributes must reference existing cell IDs
+6. Escape special characters in values: &lt; for <, &gt; for >, &amp; for &, &quot; for "
+
+**Example with swimlanes and edges** (generate ONLY this - no wrapper tags):
+\`\`\`xml
+<mxCell id="lane1" value="Frontend" style="swimlane;" vertex="1" parent="1">
+  <mxGeometry x="40" y="40" width="200" height="200" as="geometry"/>
+</mxCell>
+<mxCell id="step1" value="Step 1" style="rounded=1;" vertex="1" parent="lane1">
+  <mxGeometry x="20" y="60" width="160" height="40" as="geometry"/>
+</mxCell>
+<mxCell id="lane2" value="Backend" style="swimlane;" vertex="1" parent="1">
+  <mxGeometry x="280" y="40" width="200" height="200" as="geometry"/>
+</mxCell>
+<mxCell id="step2" value="Step 2" style="rounded=1;" vertex="1" parent="lane2">
+  <mxGeometry x="20" y="60" width="160" height="40" as="geometry"/>
+</mxCell>
+<mxCell id="edge1" style="edgeStyle=orthogonalEdgeStyle;endArrow=classic;" edge="1" parent="1" source="step1" target="step2">
+  <mxGeometry relative="1" as="geometry"/>
+</mxCell>
+\`\`\`
+
+### append_diagram Details
+
+**WHEN TO USE:** Only call this tool when display_diagram output was truncated (you'll see an error message about truncation).
+
+**CRITICAL RULES:**
+1. Do NOT include any wrapper tags - just continue the mxCell elements
+2. Continue from EXACTLY where your previous output stopped
+3. Complete the remaining mxCell elements
+4. If still truncated, call append_diagram again with the next fragment
+
+**Example:** If previous output ended with \`<mxCell id="x" style="rounded=1\`, continue with \`;" vertex="1">...\` and complete the remaining elements.
+
+### edit_diagram Details
+
+edit_diagram uses ID-based operations to modify cells directly by their id attribute.
+
+**Operations:**
+- **update**: Replace an existing cell. Provide cell_id and new_xml.
+- **add**: Add a new cell. Provide cell_id (new unique id) and new_xml.
+- **delete**: Remove a cell. Only cell_id is needed.
+
+**Input Format:**
+\`\`\`json
+{
+  "operations": [
+    {"type": "update", "cell_id": "3", "new_xml": "<mxCell ...complete element...>"},
+    {"type": "add", "cell_id": "new1", "new_xml": "<mxCell ...new element...>"},
+    {"type": "delete", "cell_id": "5"}
+  ]
+}
+\`\`\`
+
+**Examples:**
+
+Change label:
+\`\`\`json
+{"operations": [{"type": "update", "cell_id": "3", "new_xml": "<mxCell id=\\"3\\" value=\\"New Label\\" style=\\"rounded=1;\\" vertex=\\"1\\" parent=\\"1\\">\\n  <mxGeometry x=\\"100\\" y=\\"100\\" width=\\"120\\" height=\\"60\\" as=\\"geometry\\"/>\\n</mxCell>"}]}
+\`\`\`
+
+Add new shape:
+\`\`\`json
+{"operations": [{"type": "add", "cell_id": "new1", "new_xml": "<mxCell id=\\"new1\\" value=\\"New Box\\" style=\\"rounded=1;fillColor=#dae8fc;\\" vertex=\\"1\\" parent=\\"1\\">\\n  <mxGeometry x=\\"400\\" y=\\"200\\" width=\\"120\\" height=\\"60\\" as=\\"geometry\\"/>\\n</mxCell>"}]}
+\`\`\`
+
+Delete cell:
+\`\`\`json
+{"operations": [{"type": "delete", "cell_id": "5"}]}
+\`\`\`
+
+**Error Recovery:**
+If cell_id not found, check "Current diagram XML" for correct IDs. Use display_diagram if major restructuring is needed
+
+
+
+
+
 ## Edge Examples
 
 ### Two edges between same nodes (CORRECT - no overlap):
@@ -343,12 +358,16 @@ const EXTENDED_PROMPT_MODEL_PATTERNS = [
 ]
 
 /**
- * Get the appropriate system prompt based on the model ID
+ * Get the appropriate system prompt based on the model ID and style preference
  * Uses extended prompt for Opus 4.5 and Haiku 4.5 which have 4000 token cache minimum
  * @param modelId - The AI model ID from environment
+ * @param minimalStyle - If true, removes style instructions to save tokens
  * @returns The system prompt string
  */
-export function getSystemPrompt(modelId?: string): string {
+export function getSystemPrompt(
+    modelId?: string,
+    minimalStyle?: boolean,
+): string {
     const modelName = modelId || "AI"
 
     let prompt: string
@@ -369,5 +388,15 @@ export function getSystemPrompt(modelId?: string): string {
         prompt = DEFAULT_SYSTEM_PROMPT
     }
 
+    // Add style instructions based on preference
+    // Minimal style: prepend instruction at START (more prominent)
+    // Normal style: append at end
+    if (minimalStyle) {
+        console.log(`[System Prompt] Minimal style mode ENABLED`)
+        prompt = MINIMAL_STYLE_INSTRUCTION + prompt
+    } else {
+        prompt += STYLE_INSTRUCTIONS
+    }
+
     return prompt.replace("{{MODEL_NAME}}", modelName)
 }

lib/utils.ts

@@ -29,6 +29,38 @@ const STRUCTURAL_ATTRS = [
 /** Valid XML entity names */
 const VALID_ENTITIES = new Set(["lt", "gt", "amp", "quot", "apos"])
 
+// ============================================================================
+// mxCell XML Helpers
+// ============================================================================
+
+/**
+ * Check if mxCell XML output is complete (not truncated).
+ * Complete XML ends with a self-closing tag (/>) or closing mxCell tag.
+ * Also handles function-calling wrapper tags that may be incorrectly included.
+ * @param xml - The XML string to check (can be undefined/null)
+ * @returns true if XML appears complete, false if truncated or empty
+ */
+export function isMxCellXmlComplete(xml: string | undefined | null): boolean {
+    let trimmed = xml?.trim() || ""
+    if (!trimmed) return false
+
+    // Strip Anthropic function-calling wrapper tags if present
+    // These can leak into tool input due to AI SDK parsing issues
+    // Use loop because tags are nested: </mxCell></mxParameter></invoke>
+    let prev = ""
+    while (prev !== trimmed) {
+        prev = trimmed
+        trimmed = trimmed
+            .replace(/<\/mxParameter>\s*$/i, "")
+            .replace(/<\/invoke>\s*$/i, "")
+            .replace(/<\/antml:parameter>\s*$/i, "")
+            .replace(/<\/antml:invoke>\s*$/i, "")
+            .trim()
+    }
+
+    return trimmed.endsWith("/>") || trimmed.endsWith("</mxCell>")
+}
+
 // ============================================================================
 // XML Parsing Helpers
 // ============================================================================
@@ -182,6 +214,13 @@ export function convertToLegalXml(xmlString: string): string {
             )
         }
 
+        // Fix unescaped & characters in attribute values (but not valid entities)
+        // This prevents DOMParser from failing on content like "semantic & missing-step"
+        cellContent = cellContent.replace(
+            /&(?!(?:lt|gt|amp|quot|apos|#[0-9]+|#x[0-9a-fA-F]+);)/g,
+            "&amp;",
+        )
+
         // Indent each line of the matched block for readability.
         const formatted = cellContent
             .split("\n")
@@ -197,13 +236,17 @@ export function convertToLegalXml(xmlString: string): string {
 
 /**
  * Wrap XML content with the full mxfile structure required by draw.io.
- * Handles cases where XML is just <root>, <mxGraphModel>, or already has <mxfile>.
- * @param xml - The XML string (may be partial or complete)
- * @returns Full mxfile-wrapped XML string
+ * Always adds root cells (id="0" and id="1") automatically.
+ * If input already contains root cells, they are removed to avoid duplication.
+ * LLM should only generate mxCell elements starting from id="2".
+ * @param xml - The XML string (bare mxCells, <root>, <mxGraphModel>, or full <mxfile>)
+ * @returns Full mxfile-wrapped XML string with root cells included
  */
 export function wrapWithMxFile(xml: string): string {
-    if (!xml) {
-        return `<mxfile><diagram name="Page-1" id="page-1"><mxGraphModel><root><mxCell id="0"/><mxCell id="1" parent="0"/></root></mxGraphModel></diagram></mxfile>`
+    const ROOT_CELLS = '<mxCell id="0"/><mxCell id="1" parent="0"/>'
+
+    if (!xml || !xml.trim()) {
+        return `<mxfile><diagram name="Page-1" id="page-1"><mxGraphModel><root>${ROOT_CELLS}</root></mxGraphModel></diagram></mxfile>`
     }
 
     // Already has full structure
@@ -216,9 +259,20 @@ export function wrapWithMxFile(xml: string): string {
         return `<mxfile><diagram name="Page-1" id="page-1">${xml}</diagram></mxfile>`
     }
 
-    // Just <root> content - extract inner content and wrap fully
-    const rootContent = xml.replace(/<\/?root>/g, "").trim()
-    return `<mxfile><diagram name="Page-1" id="page-1"><mxGraphModel><root>${rootContent}</root></mxGraphModel></diagram></mxfile>`
+    // Has <root> wrapper - extract inner content
+    let content = xml
+    if (xml.includes("<root>")) {
+        content = xml.replace(/<\/?root>/g, "").trim()
+    }
+
+    // Remove any existing root cells from content (LLM shouldn't include them, but handle it gracefully)
+    // Use flexible patterns that match both self-closing (/>) and non-self-closing (></mxCell>) formats
+    content = content
+        .replace(/<mxCell[^>]*\bid=["']0["'][^>]*(?:\/>|><\/mxCell>)/g, "")
+        .replace(/<mxCell[^>]*\bid=["']1["'][^>]*(?:\/>|><\/mxCell>)/g, "")
+        .trim()
+
+    return `<mxfile><diagram name="Page-1" id="page-1"><mxGraphModel><root>${ROOT_CELLS}${content}</root></mxGraphModel></diagram></mxfile>`
 }
 
 /**
@@ -323,303 +377,223 @@ export function replaceNodes(currentXML: string, nodes: string): string {
     }
 }
 
-/**
- * Create a character count dictionary from a string
- * Used for attribute-order agnostic comparison
- */
-function charCountDict(str: string): Map<string, number> {
-    const dict = new Map<string, number>()
-    for (const char of str) {
-        dict.set(char, (dict.get(char) || 0) + 1)
-    }
-    return dict
+// ============================================================================
+// ID-based Diagram Operations
+// ============================================================================
+
+export interface DiagramOperation {
+    type: "update" | "add" | "delete"
+    cell_id: string
+    new_xml?: string
+}
+
+export interface OperationError {
+    type: "update" | "add" | "delete"
+    cellId: string
+    message: string
+}
+
+export interface ApplyOperationsResult {
+    result: string
+    errors: OperationError[]
 }
 
 /**
- * Compare two strings by character frequency (order-agnostic)
+ * Apply diagram operations (update/add/delete) using ID-based lookup.
+ * This replaces the text-matching approach with direct DOM manipulation.
+ *
+ * @param xmlContent - The full mxfile XML content
+ * @param operations - Array of operations to apply
+ * @returns Object with result XML and any errors
  */
-function sameCharFrequency(a: string, b: string): boolean {
-    const trimmedA = a.trim()
-    const trimmedB = b.trim()
-    if (trimmedA.length !== trimmedB.length) return false
-
-    const dictA = charCountDict(trimmedA)
-    const dictB = charCountDict(trimmedB)
-
-    if (dictA.size !== dictB.size) return false
-
-    for (const [char, count] of dictA) {
-        if (dictB.get(char) !== count) return false
-    }
-    return true
-}
-
-/**
- * Replace specific parts of XML content using search and replace pairs
- * @param xmlContent - The original XML string
- * @param searchReplacePairs - Array of {search: string, replace: string} objects
- * @returns The updated XML string with replacements applied
- */
-export function replaceXMLParts(
+export function applyDiagramOperations(
     xmlContent: string,
-    searchReplacePairs: Array<{ search: string; replace: string }>,
-): string {
-    // Format the XML first to ensure consistent line breaks
-    let result = formatXML(xmlContent)
+    operations: DiagramOperation[],
+): ApplyOperationsResult {
+    const errors: OperationError[] = []
 
-    for (const { search, replace } of searchReplacePairs) {
-        // Also format the search content for consistency
-        const formattedSearch = formatXML(search)
-        const searchLines = formattedSearch.split("\n")
+    // Parse the XML
+    const parser = new DOMParser()
+    const doc = parser.parseFromString(xmlContent, "text/xml")
 
-        // Split into lines for exact line matching
-        const resultLines = result.split("\n")
-
-        // Remove trailing empty line if exists (from the trailing \n in search content)
-        if (searchLines[searchLines.length - 1] === "") {
-            searchLines.pop()
+    // Check for parse errors
+    const parseError = doc.querySelector("parsererror")
+    if (parseError) {
+        return {
+            result: xmlContent,
+            errors: [
+                {
+                    type: "update",
+                    cellId: "",
+                    message: `XML parse error: ${parseError.textContent}`,
+                },
+            ],
         }
-
-        // Always search from the beginning - pairs may not be in document order
-        const startLineNum = 0
-
-        // Try to find match using multiple strategies
-        let matchFound = false
-        let matchStartLine = -1
-        let matchEndLine = -1
-
-        // First try: exact match
-        for (
-            let i = startLineNum;
-            i <= resultLines.length - searchLines.length;
-            i++
-        ) {
-            let matches = true
-
-            for (let j = 0; j < searchLines.length; j++) {
-                if (resultLines[i + j] !== searchLines[j]) {
-                    matches = false
-                    break
-                }
-            }
-
-            if (matches) {
-                matchStartLine = i
-                matchEndLine = i + searchLines.length
-                matchFound = true
-                break
-            }
-        }
-
-        // Second try: line-trimmed match (fallback)
-        if (!matchFound) {
-            for (
-                let i = startLineNum;
-                i <= resultLines.length - searchLines.length;
-                i++
-            ) {
-                let matches = true
-
-                for (let j = 0; j < searchLines.length; j++) {
-                    const originalTrimmed = resultLines[i + j].trim()
-                    const searchTrimmed = searchLines[j].trim()
-
-                    if (originalTrimmed !== searchTrimmed) {
-                        matches = false
-                        break
-                    }
-                }
-
-                if (matches) {
-                    matchStartLine = i
-                    matchEndLine = i + searchLines.length
-                    matchFound = true
-                    break
-                }
-            }
-        }
-
-        // Third try: substring match as last resort (for single-line XML)
-        if (!matchFound) {
-            // Try to find as a substring in the entire content
-            const searchStr = search.trim()
-            const resultStr = result
-            const index = resultStr.indexOf(searchStr)
-
-            if (index !== -1) {
-                // Found as substring - replace it
-                result =
-                    resultStr.substring(0, index) +
-                    replace.trim() +
-                    resultStr.substring(index + searchStr.length)
-                // Re-format after substring replacement
-                result = formatXML(result)
-                continue // Skip the line-based replacement below
-            }
-        }
-
-        // Fourth try: character frequency match (attribute-order agnostic)
-        // This handles cases where the model generates XML with different attribute order
-        if (!matchFound) {
-            for (
-                let i = startLineNum;
-                i <= resultLines.length - searchLines.length;
-                i++
-            ) {
-                let matches = true
-
-                for (let j = 0; j < searchLines.length; j++) {
-                    if (
-                        !sameCharFrequency(resultLines[i + j], searchLines[j])
-                    ) {
-                        matches = false
-                        break
-                    }
-                }
-
-                if (matches) {
-                    matchStartLine = i
-                    matchEndLine = i + searchLines.length
-                    matchFound = true
-                    break
-                }
-            }
-        }
-
-        // Fifth try: Match by mxCell id attribute
-        // Extract id from search pattern and find the element with that id
-        if (!matchFound) {
-            const idMatch = search.match(/id="([^"]+)"/)
-            if (idMatch) {
-                const searchId = idMatch[1]
-                // Find lines that contain this id
-                for (let i = startLineNum; i < resultLines.length; i++) {
-                    if (resultLines[i].includes(`id="${searchId}"`)) {
-                        // Found the element with matching id
-                        // Now find the extent of this element (it might span multiple lines)
-                        let endLine = i + 1
-                        const line = resultLines[i].trim()
-
-                        // Check if it's a self-closing tag or has children
-                        if (!line.endsWith("/>")) {
-                            // Find the closing tag or the end of the mxCell block
-                            let depth = 1
-                            while (endLine < resultLines.length && depth > 0) {
-                                const currentLine = resultLines[endLine].trim()
-                                if (
-                                    currentLine.startsWith("<") &&
-                                    !currentLine.startsWith("</") &&
-                                    !currentLine.endsWith("/>")
-                                ) {
-                                    depth++
-                                } else if (currentLine.startsWith("</")) {
-                                    depth--
-                                }
-                                endLine++
-                            }
-                        }
-
-                        matchStartLine = i
-                        matchEndLine = endLine
-                        matchFound = true
-                        break
-                    }
-                }
-            }
-        }
-
-        // Sixth try: Match by value attribute (label text)
-        // Extract value from search pattern and find elements with that value
-        if (!matchFound) {
-            const valueMatch = search.match(/value="([^"]*)"/)
-            if (valueMatch) {
-                const searchValue = valueMatch[0] // Use full match like value="text"
-                for (let i = startLineNum; i < resultLines.length; i++) {
-                    if (resultLines[i].includes(searchValue)) {
-                        // Found element with matching value
-                        let endLine = i + 1
-                        const line = resultLines[i].trim()
-
-                        if (!line.endsWith("/>")) {
-                            let depth = 1
-                            while (endLine < resultLines.length && depth > 0) {
-                                const currentLine = resultLines[endLine].trim()
-                                if (
-                                    currentLine.startsWith("<") &&
-                                    !currentLine.startsWith("</") &&
-                                    !currentLine.endsWith("/>")
-                                ) {
-                                    depth++
-                                } else if (currentLine.startsWith("</")) {
-                                    depth--
-                                }
-                                endLine++
-                            }
-                        }
-
-                        matchStartLine = i
-                        matchEndLine = endLine
-                        matchFound = true
-                        break
-                    }
-                }
-            }
-        }
-
-        // Seventh try: Normalized whitespace match
-        // Collapse all whitespace and compare
-        if (!matchFound) {
-            const normalizeWs = (s: string) => s.replace(/\s+/g, " ").trim()
-            const normalizedSearch = normalizeWs(search)
-
-            for (
-                let i = startLineNum;
-                i <= resultLines.length - searchLines.length;
-                i++
-            ) {
-                // Build a normalized version of the candidate lines
-                const candidateLines = resultLines.slice(
-                    i,
-                    i + searchLines.length,
-                )
-                const normalizedCandidate = normalizeWs(
-                    candidateLines.join(" "),
-                )
-
-                if (normalizedCandidate === normalizedSearch) {
-                    matchStartLine = i
-                    matchEndLine = i + searchLines.length
-                    matchFound = true
-                    break
-                }
-            }
-        }
-
-        if (!matchFound) {
-            throw new Error(
-                `Search pattern not found in the diagram. The pattern may not exist in the current structure.`,
-            )
-        }
-
-        // Replace the matched lines
-        const replaceLines = replace.split("\n")
-
-        // Remove trailing empty line if exists
-        if (replaceLines[replaceLines.length - 1] === "") {
-            replaceLines.pop()
-        }
-
-        // Perform the replacement
-        const newResultLines = [
-            ...resultLines.slice(0, matchStartLine),
-            ...replaceLines,
-            ...resultLines.slice(matchEndLine),
-        ]
-
-        result = newResultLines.join("\n")
     }
 
-    return result
+    // Find the root element (inside mxGraphModel)
+    const root = doc.querySelector("root")
+    if (!root) {
+        return {
+            result: xmlContent,
+            errors: [
+                {
+                    type: "update",
+                    cellId: "",
+                    message: "Could not find <root> element in XML",
+                },
+            ],
+        }
+    }
+
+    // Build a map of cell IDs to elements
+    const cellMap = new Map<string, Element>()
+    root.querySelectorAll("mxCell").forEach((cell) => {
+        const id = cell.getAttribute("id")
+        if (id) cellMap.set(id, cell)
+    })
+
+    // Process each operation
+    for (const op of operations) {
+        if (op.type === "update") {
+            const existingCell = cellMap.get(op.cell_id)
+            if (!existingCell) {
+                errors.push({
+                    type: "update",
+                    cellId: op.cell_id,
+                    message: `Cell with id="${op.cell_id}" not found`,
+                })
+                continue
+            }
+
+            if (!op.new_xml) {
+                errors.push({
+                    type: "update",
+                    cellId: op.cell_id,
+                    message: "new_xml is required for update operation",
+                })
+                continue
+            }
+
+            // Parse the new XML
+            const newDoc = parser.parseFromString(
+                `<wrapper>${op.new_xml}</wrapper>`,
+                "text/xml",
+            )
+            const newCell = newDoc.querySelector("mxCell")
+            if (!newCell) {
+                errors.push({
+                    type: "update",
+                    cellId: op.cell_id,
+                    message: "new_xml must contain an mxCell element",
+                })
+                continue
+            }
+
+            // Validate ID matches
+            const newCellId = newCell.getAttribute("id")
+            if (newCellId !== op.cell_id) {
+                errors.push({
+                    type: "update",
+                    cellId: op.cell_id,
+                    message: `ID mismatch: cell_id is "${op.cell_id}" but new_xml has id="${newCellId}"`,
+                })
+                continue
+            }
+
+            // Import and replace the node
+            const importedNode = doc.importNode(newCell, true)
+            existingCell.parentNode?.replaceChild(importedNode, existingCell)
+
+            // Update the map with the new element
+            cellMap.set(op.cell_id, importedNode)
+        } else if (op.type === "add") {
+            // Check if ID already exists
+            if (cellMap.has(op.cell_id)) {
+                errors.push({
+                    type: "add",
+                    cellId: op.cell_id,
+                    message: `Cell with id="${op.cell_id}" already exists`,
+                })
+                continue
+            }
+
+            if (!op.new_xml) {
+                errors.push({
+                    type: "add",
+                    cellId: op.cell_id,
+                    message: "new_xml is required for add operation",
+                })
+                continue
+            }
+
+            // Parse the new XML
+            const newDoc = parser.parseFromString(
+                `<wrapper>${op.new_xml}</wrapper>`,
+                "text/xml",
+            )
+            const newCell = newDoc.querySelector("mxCell")
+            if (!newCell) {
+                errors.push({
+                    type: "add",
+                    cellId: op.cell_id,
+                    message: "new_xml must contain an mxCell element",
+                })
+                continue
+            }
+
+            // Validate ID matches
+            const newCellId = newCell.getAttribute("id")
+            if (newCellId !== op.cell_id) {
+                errors.push({
+                    type: "add",
+                    cellId: op.cell_id,
+                    message: `ID mismatch: cell_id is "${op.cell_id}" but new_xml has id="${newCellId}"`,
+                })
+                continue
+            }
+
+            // Import and append the node
+            const importedNode = doc.importNode(newCell, true)
+            root.appendChild(importedNode)
+
+            // Add to map
+            cellMap.set(op.cell_id, importedNode)
+        } else if (op.type === "delete") {
+            const existingCell = cellMap.get(op.cell_id)
+            if (!existingCell) {
+                errors.push({
+                    type: "delete",
+                    cellId: op.cell_id,
+                    message: `Cell with id="${op.cell_id}" not found`,
+                })
+                continue
+            }
+
+            // Check for edges referencing this cell (warning only, still delete)
+            const referencingEdges = root.querySelectorAll(
+                `mxCell[source="${op.cell_id}"], mxCell[target="${op.cell_id}"]`,
+            )
+            if (referencingEdges.length > 0) {
+                const edgeIds = Array.from(referencingEdges)
+                    .map((e) => e.getAttribute("id"))
+                    .join(", ")
+                console.warn(
+                    `[applyDiagramOperations] Deleting cell "${op.cell_id}" which is referenced by edges: ${edgeIds}`,
+                )
+            }
+
+            // Remove the node
+            existingCell.parentNode?.removeChild(existingCell)
+            cellMap.delete(op.cell_id)
+        }
+    }
+
+    // Serialize back to string
+    const serializer = new XMLSerializer()
+    const result = serializer.serializeToString(doc)
+
+    return { result, errors }
 }
 
 // ============================================================================
@@ -808,7 +782,9 @@ export function validateMxCellStructure(xml: string): string | null {
 
     // 2. Check for duplicate structural attributes
     const dupAttrError = checkDuplicateAttributes(xml)
-    if (dupAttrError) return dupAttrError
+    if (dupAttrError) {
+        return dupAttrError
+    }
 
     // 3. Check for unescaped < in attribute values
     const attrValuePattern = /=\s*"([^"]*)"/g
@@ -822,15 +798,21 @@ export function validateMxCellStructure(xml: string): string | null {
 
     // 4. Check for duplicate IDs
     const dupIdError = checkDuplicateIds(xml)
-    if (dupIdError) return dupIdError
+    if (dupIdError) {
+        return dupIdError
+    }
 
     // 5. Check for tag mismatches
     const tagMismatchError = checkTagMismatches(xml)
-    if (tagMismatchError) return tagMismatchError
+    if (tagMismatchError) {
+        return tagMismatchError
+    }
 
     // 6. Check invalid character references
     const charRefError = checkCharacterReferences(xml)
-    if (charRefError) return charRefError
+    if (charRefError) {
+        return charRefError
+    }
 
     // 7. Check for invalid comment syntax (-- inside comments)
     const commentPattern = /<!--([\s\S]*?)-->/g
@@ -843,7 +825,9 @@ export function validateMxCellStructure(xml: string): string | null {
 
     // 8. Check for unescaped entity references and invalid entity names
     const entityError = checkEntityReferences(xml)
-    if (entityError) return entityError
+    if (entityError) {
+        return entityError
+    }
 
     // 9. Check for empty id attributes on mxCell
     if (/<mxCell[^>]*\sid\s*=\s*["']\s*["'][^>]*>/g.test(xml)) {
@@ -852,7 +836,9 @@ export function validateMxCellStructure(xml: string): string | null {
 
     // 10. Check for nested mxCell tags
     const nestedCellError = checkNestedMxCells(xml)
-    if (nestedCellError) return nestedCellError
+    if (nestedCellError) {
+        return nestedCellError
+    }
 
     return null
 }
@@ -1057,12 +1043,56 @@ export function autoFixXml(xml: string): { fixed: string; fixes: string[] } {
     // This handles both opening and closing tags
     const hasCellTags = /<\/?Cell[\s>]/i.test(fixed)
     if (hasCellTags) {
+        console.log("[autoFixXml] Step 8: Found <Cell> tags to fix")
+        const beforeFix = fixed
         fixed = fixed.replace(/<Cell(\s)/gi, "<mxCell$1")
         fixed = fixed.replace(/<Cell>/gi, "<mxCell>")
         fixed = fixed.replace(/<\/Cell>/gi, "</mxCell>")
+        if (beforeFix !== fixed) {
+            console.log("[autoFixXml] Step 8: Fixed <Cell> tags")
+        }
         fixes.push("Fixed <Cell> tags to <mxCell>")
     }
 
+    // 8b. Remove non-draw.io tags (LLM sometimes includes Claude's function calling XML)
+    // Valid draw.io tags: mxfile, diagram, mxGraphModel, root, mxCell, mxGeometry, mxPoint, Array, Object
+    const validDrawioTags = new Set([
+        "mxfile",
+        "diagram",
+        "mxGraphModel",
+        "root",
+        "mxCell",
+        "mxGeometry",
+        "mxPoint",
+        "Array",
+        "Object",
+        "mxRectangle",
+    ])
+    const foreignTagPattern = /<\/?([a-zA-Z][a-zA-Z0-9_]*)[^>]*>/g
+    let foreignMatch
+    const foreignTags = new Set<string>()
+    while ((foreignMatch = foreignTagPattern.exec(fixed)) !== null) {
+        const tagName = foreignMatch[1]
+        if (!validDrawioTags.has(tagName)) {
+            foreignTags.add(tagName)
+        }
+    }
+    if (foreignTags.size > 0) {
+        console.log(
+            "[autoFixXml] Step 8b: Found foreign tags:",
+            Array.from(foreignTags),
+        )
+        for (const tag of foreignTags) {
+            // Remove opening tags (with or without attributes)
+            fixed = fixed.replace(new RegExp(`<${tag}[^>]*>`, "gi"), "")
+            // Remove closing tags
+            fixed = fixed.replace(new RegExp(`</${tag}>`, "gi"), "")
+        }
+        fixes.push(
+            `Removed foreign tags: ${Array.from(foreignTags).join(", ")}`,
+        )
+    }
+
     // 9. Fix common closing tag typos
     const tagTypos = [
         { wrong: /<\/mxElement>/gi, right: "</mxCell>", name: "</mxElement>" },
@@ -1128,6 +1158,98 @@ export function autoFixXml(xml: string): { fixed: string; fixes: string[] } {
         }
     }
 
+    // 10b. Remove extra closing tags (more closes than opens)
+    // Need to properly count self-closing tags (they don't need closing tags)
+    const tagCounts = new Map<
+        string,
+        { opens: number; closes: number; selfClosing: number }
+    >()
+    // Match full tags to detect self-closing by checking if ends with />
+    const fullTagPattern = /<(\/?[a-zA-Z][a-zA-Z0-9]*)[^>]*>/g
+    let tagCountMatch
+    while ((tagCountMatch = fullTagPattern.exec(fixed)) !== null) {
+        const fullMatch = tagCountMatch[0] // e.g., "<mxCell .../>" or "</mxCell>"
+        const tagPart = tagCountMatch[1] // e.g., "mxCell" or "/mxCell"
+        const isClosing = tagPart.startsWith("/")
+        const isSelfClosing = fullMatch.endsWith("/>")
+        const tagName = isClosing ? tagPart.slice(1) : tagPart
+
+        let counts = tagCounts.get(tagName)
+        if (!counts) {
+            counts = { opens: 0, closes: 0, selfClosing: 0 }
+            tagCounts.set(tagName, counts)
+        }
+        if (isClosing) {
+            counts.closes++
+        } else if (isSelfClosing) {
+            counts.selfClosing++
+        } else {
+            counts.opens++
+        }
+    }
+
+    // Log tag counts for debugging
+    for (const [tagName, counts] of tagCounts) {
+        if (
+            tagName === "mxCell" ||
+            tagName === "mxGeometry" ||
+            counts.opens !== counts.closes
+        ) {
+            console.log(
+                `[autoFixXml] Step 10b: ${tagName} - opens: ${counts.opens}, closes: ${counts.closes}, selfClosing: ${counts.selfClosing}`,
+            )
+        }
+    }
+
+    // Find tags with extra closing tags (self-closing tags are balanced, don't need closing)
+    for (const [tagName, counts] of tagCounts) {
+        const extraCloses = counts.closes - counts.opens // Only compare opens vs closes (self-closing are balanced)
+        if (extraCloses > 0) {
+            console.log(
+                `[autoFixXml] Step 10b: ${tagName} has ${counts.opens} opens, ${counts.closes} closes, removing ${extraCloses} extra`,
+            )
+            // Remove extra closing tags from the end
+            let removed = 0
+            const closeTagPattern = new RegExp(`</${tagName}>`, "g")
+            const matches = [...fixed.matchAll(closeTagPattern)]
+            // Remove from the end (last occurrences are likely the extras)
+            for (
+                let i = matches.length - 1;
+                i >= 0 && removed < extraCloses;
+                i--
+            ) {
+                const match = matches[i]
+                const idx = match.index ?? 0
+                fixed = fixed.slice(0, idx) + fixed.slice(idx + match[0].length)
+                removed++
+            }
+            if (removed > 0) {
+                console.log(
+                    `[autoFixXml] Step 10b: Removed ${removed} extra </${tagName}>`,
+                )
+                fixes.push(
+                    `Removed ${removed} extra </${tagName}> closing tag(s)`,
+                )
+            }
+        }
+    }
+
+    // 10c. Remove trailing garbage after last XML tag (e.g., stray backslashes, text)
+    // Find the last valid closing tag or self-closing tag
+    const closingTagPattern = /<\/[a-zA-Z][a-zA-Z0-9]*>|\/>/g
+    let lastValidTagEnd = -1
+    let closingMatch
+    while ((closingMatch = closingTagPattern.exec(fixed)) !== null) {
+        lastValidTagEnd = closingMatch.index + closingMatch[0].length
+    }
+    if (lastValidTagEnd > 0 && lastValidTagEnd < fixed.length) {
+        const trailing = fixed.slice(lastValidTagEnd).trim()
+        if (trailing) {
+            fixed = fixed.slice(0, lastValidTagEnd)
+            fixes.push("Removed trailing garbage after last XML tag")
+        }
+    }
+
     // 11. Fix nested mxCell by flattening
     // Pattern A: <mxCell id="X">...<mxCell id="X">...</mxCell></mxCell> (duplicate ID)
     // Pattern B: <mxCell id="X">...<mxCell id="Y">...</mxCell></mxCell> (different ID - true nesting)
@@ -1337,16 +1459,26 @@ export function validateAndFixXml(xml: string): {
 
     // Try to fix
     const { fixed, fixes } = autoFixXml(xml)
+    console.log("[validateAndFixXml] Fixes applied:", fixes)
 
     // Validate the fixed version
     error = validateMxCellStructure(fixed)
+    if (error) {
+        console.log("[validateAndFixXml] Still invalid after fix:", error)
+    }
 
     if (!error) {
         return { valid: true, error: null, fixed, fixes }
     }
 
-    // Still invalid after fixes
-    return { valid: false, error, fixed: null, fixes }
+    // Still invalid after fixes - but return the partially fixed XML
+    // so we can see what was fixed and what error remains
+    return {
+        valid: false,
+        error,
+        fixed: fixes.length > 0 ? fixed : null,
+        fixes,
+    }
 }
 
 export function extractDiagramXML(xml_svg_string: string): string {

package-lock.json

@@ -1,18 +1,19 @@
 {
     "name": "next-ai-draw-io",
-    "version": "0.4.0",
+    "version": "0.4.2",
     "lockfileVersion": 3,
     "requires": true,
     "packages": {
         "": {
             "name": "next-ai-draw-io",
-            "version": "0.4.0",
+            "version": "0.4.2",
             "license": "Apache-2.0",
             "dependencies": {
                 "@ai-sdk/amazon-bedrock": "^3.0.70",
                 "@ai-sdk/anthropic": "^2.0.44",
                 "@ai-sdk/azure": "^2.0.69",
                 "@ai-sdk/deepseek": "^1.0.30",
+                "@ai-sdk/gateway": "^2.0.21",
                 "@ai-sdk/google": "^2.0.0",
                 "@ai-sdk/openai": "^2.0.19",
                 "@ai-sdk/react": "^2.0.107",
@@ -40,6 +41,7 @@
                 "clsx": "^2.1.1",
                 "js-tiktoken": "^1.0.21",
                 "jsdom": "^26.0.0",
+                "jsonrepair": "^3.13.1",
                 "lucide-react": "^0.483.0",
                 "motion": "^12.23.25",
                 "next": "^16.0.7",
@@ -198,13 +200,13 @@
             }
         },
         "node_modules/@ai-sdk/gateway": {
-            "version": "2.0.18",
-            "resolved": "https://registry.npmjs.org/@ai-sdk/gateway/-/gateway-2.0.18.tgz",
-            "integrity": "sha512-sDQcW+6ck2m0pTIHW6BPHD7S125WD3qNkx/B8sEzJp/hurocmJ5Cni0ybExg6sQMGo+fr/GWOwpHF1cmCdg5rQ==",
+            "version": "2.0.21",
+            "resolved": "https://registry.npmjs.org/@ai-sdk/gateway/-/gateway-2.0.21.tgz",
+            "integrity": "sha512-BwV7DU/lAm3Xn6iyyvZdWgVxgLu3SNXzl5y57gMvkW4nGhAOV5269IrJzQwGt03bb107sa6H6uJwWxc77zXoGA==",
             "license": "Apache-2.0",
             "dependencies": {
                 "@ai-sdk/provider": "2.0.0",
-                "@ai-sdk/provider-utils": "3.0.18",
+                "@ai-sdk/provider-utils": "3.0.19",
                 "@vercel/oidc": "3.0.5"
             },
             "engines": {
@@ -214,6 +216,23 @@
                 "zod": "^3.25.76 || ^4.1.8"
             }
         },
+        "node_modules/@ai-sdk/gateway/node_modules/@ai-sdk/provider-utils": {
+            "version": "3.0.19",
+            "resolved": "https://registry.npmjs.org/@ai-sdk/provider-utils/-/provider-utils-3.0.19.tgz",
+            "integrity": "sha512-W41Wc9/jbUVXVwCN/7bWa4IKe8MtxO3EyA0Hfhx6grnmiYlCvpI8neSYWFE0zScXJkgA/YK3BRybzgyiXuu6JA==",
+            "license": "Apache-2.0",
+            "dependencies": {
+                "@ai-sdk/provider": "2.0.0",
+                "@standard-schema/spec": "^1.0.0",
+                "eventsource-parser": "^3.0.6"
+            },
+            "engines": {
+                "node": ">=18"
+            },
+            "peerDependencies": {
+                "zod": "^3.25.76 || ^4.1.8"
+            }
+        },
         "node_modules/@ai-sdk/google": {
             "version": "2.0.0",
             "resolved": "https://registry.npmjs.org/@ai-sdk/google/-/google-2.0.0.tgz",
@@ -6129,6 +6148,23 @@
                 "zod": "^3.25.76 || ^4.1.8"
             }
         },
+        "node_modules/ai/node_modules/@ai-sdk/gateway": {
+            "version": "2.0.18",
+            "resolved": "https://registry.npmjs.org/@ai-sdk/gateway/-/gateway-2.0.18.tgz",
+            "integrity": "sha512-sDQcW+6ck2m0pTIHW6BPHD7S125WD3qNkx/B8sEzJp/hurocmJ5Cni0ybExg6sQMGo+fr/GWOwpHF1cmCdg5rQ==",
+            "license": "Apache-2.0",
+            "dependencies": {
+                "@ai-sdk/provider": "2.0.0",
+                "@ai-sdk/provider-utils": "3.0.18",
+                "@vercel/oidc": "3.0.5"
+            },
+            "engines": {
+                "node": ">=18"
+            },
+            "peerDependencies": {
+                "zod": "^3.25.76 || ^4.1.8"
+            }
+        },
         "node_modules/ajv": {
             "version": "6.12.6",
             "resolved": "https://registry.npmjs.org/ajv/-/ajv-6.12.6.tgz",
@@ -9199,6 +9235,15 @@
                 "node": ">=6"
             }
         },
+        "node_modules/jsonrepair": {
+            "version": "3.13.1",
+            "resolved": "https://registry.npmjs.org/jsonrepair/-/jsonrepair-3.13.1.tgz",
+            "integrity": "sha512-WJeiE0jGfxYmtLwBTEk8+y/mYcaleyLXWaqp5bJu0/ZTSeG0KQq/wWQ8pmnkKenEdN6pdnn6QtcoSUkbqDHWNw==",
+            "license": "ISC",
+            "bin": {
+                "jsonrepair": "bin/cli.js"
+            }
+        },
         "node_modules/jsx-ast-utils": {
             "version": "3.3.5",
             "resolved": "https://registry.npmjs.org/jsx-ast-utils/-/jsx-ast-utils-3.3.5.tgz",

package.json

@@ -1,6 +1,6 @@
 {
     "name": "next-ai-draw-io",
-    "version": "0.4.0",
+    "version": "0.4.3",
     "license": "Apache-2.0",
     "private": true,
     "scripts": {
@@ -17,6 +17,7 @@
         "@ai-sdk/anthropic": "^2.0.44",
         "@ai-sdk/azure": "^2.0.69",
         "@ai-sdk/deepseek": "^1.0.30",
+        "@ai-sdk/gateway": "^2.0.21",
         "@ai-sdk/google": "^2.0.0",
         "@ai-sdk/openai": "^2.0.19",
         "@ai-sdk/react": "^2.0.107",
@@ -44,6 +45,7 @@
         "clsx": "^2.1.1",
         "js-tiktoken": "^1.0.21",
         "jsdom": "^26.0.0",
+        "jsonrepair": "^3.13.1",
         "lucide-react": "^0.483.0",
         "motion": "^12.23.25",
         "next": "^16.0.7",

packages/mcp-server/README.md

@@ -0,0 +1,162 @@
+# Next AI Draw.io MCP Server
+
+MCP (Model Context Protocol) server that enables AI agents like Claude Desktop and Cursor to generate and edit draw.io diagrams with **real-time browser preview**.
+
+**Self-contained** - includes an embedded HTTP server, no external dependencies required.
+
+## Quick Start
+
+```json
+{
+  "mcpServers": {
+    "drawio": {
+      "command": "npx",
+      "args": ["@next-ai-drawio/mcp-server@latest"]
+    }
+  }
+}
+```
+
+## Installation
+
+### Claude Desktop
+
+Add to your Claude Desktop config (`~/Library/Application Support/Claude/claude_desktop_config.json` on macOS):
+
+```json
+{
+  "mcpServers": {
+    "drawio": {
+      "command": "npx",
+      "args": ["@next-ai-drawio/mcp-server@latest"]
+    }
+  }
+}
+```
+
+### VS Code
+
+Add to your VS Code settings (`.vscode/mcp.json` in workspace or user settings):
+
+```json
+{
+  "mcpServers": {
+    "drawio": {
+      "command": "npx",
+      "args": ["@next-ai-drawio/mcp-server@latest"]
+    }
+  }
+}
+```
+
+### Cursor
+
+Add to Cursor MCP config (`~/.cursor/mcp.json`):
+
+```json
+{
+  "mcpServers": {
+    "drawio": {
+      "command": "npx",
+      "args": ["@next-ai-drawio/mcp-server@latest"]
+    }
+  }
+}
+```
+
+### Claude Code CLI
+
+```bash
+claude mcp add drawio -- npx @next-ai-drawio/mcp-server@latest
+```
+
+### Other MCP Clients
+
+Use the standard MCP configuration with:
+- **Command**: `npx`
+- **Args**: `["@next-ai-drawio/mcp-server@latest"]`
+
+## Usage
+
+1. Restart your MCP client after updating config
+2. Ask the AI to create a diagram:
+   > "Create a flowchart showing user authentication with login, MFA, and session management"
+3. The diagram appears in your browser in real-time!
+
+## Features
+
+- **Real-time Preview**: Diagrams appear and update in your browser as the AI creates them
+- **Natural Language**: Describe diagrams in plain text - flowcharts, architecture diagrams, etc.
+- **Edit Support**: Modify existing diagrams with natural language instructions
+- **Export**: Save diagrams as `.drawio` files
+- **Self-contained**: Embedded server, works offline (except draw.io UI which loads from embed.diagrams.net)
+
+## Available Tools
+
+| Tool | Description |
+|------|-------------|
+| `start_session` | Opens browser with real-time diagram preview |
+| `display_diagram` | Create a new diagram from XML |
+| `edit_diagram` | Edit diagram by ID-based operations (update/add/delete cells) |
+| `get_diagram` | Get the current diagram XML |
+| `export_diagram` | Save diagram to a `.drawio` file |
+
+## How It Works
+
+```
+┌─────────────────┐     stdio      ┌─────────────────┐
+│  Claude Desktop │ <───────────> │   MCP Server    │
+│    (AI Agent)   │               │  (this package) │
+└─────────────────┘               └────────┬────────┘
+                                          │
+                                 ┌────────▼────────┐
+                                 │ Embedded HTTP   │
+                                 │ Server (:6002)  │
+                                 └────────┬────────┘
+                                          │
+                                 ┌────────▼────────┐
+                                 │  User's Browser │
+                                 │ (draw.io embed) │
+                                 └─────────────────┘
+```
+
+1. **MCP Server** receives tool calls from Claude via stdio
+2. **Embedded HTTP Server** serves the draw.io UI and handles state
+3. **Browser** shows real-time diagram updates via polling
+
+## Configuration
+
+| Variable | Default | Description |
+|----------|---------|-------------|
+| `PORT` | `6002` | Port for the embedded HTTP server |
+
+## Troubleshooting
+
+### Port already in use
+
+If port 6002 is in use, the server will automatically try the next available port (up to 6020).
+
+Or set a custom port:
+```json
+{
+  "mcpServers": {
+    "drawio": {
+      "command": "npx",
+      "args": ["@next-ai-drawio/mcp-server@latest"],
+      "env": { "PORT": "6003" }
+    }
+  }
+}
+```
+
+### "No active session"
+
+Call `start_session` first to open the browser window.
+
+### Browser not updating
+
+Check that the browser URL has the `?mcp=` query parameter. The MCP session ID connects the browser to the server.
+
+## License
+
+Apache-2.0

packages/mcp-server/package.json

@@ -0,0 +1,55 @@
+{
+    "name": "@next-ai-drawio/mcp-server",
+    "version": "0.1.2",
+    "description": "MCP server for Next AI Draw.io - AI-powered diagram generation with real-time browser preview",
+    "type": "module",
+    "main": "dist/index.js",
+    "bin": {
+        "next-ai-drawio-mcp": "./dist/index.js"
+    },
+    "scripts": {
+        "build": "tsc",
+        "dev": "tsx watch src/index.ts",
+        "start": "node dist/index.js",
+        "prepublishOnly": "npm run build"
+    },
+    "keywords": [
+        "mcp",
+        "drawio",
+        "diagram",
+        "ai",
+        "claude",
+        "model-context-protocol"
+    ],
+    "author": "Biki-dev",
+    "license": "Apache-2.0",
+    "repository": {
+        "type": "git",
+        "url": "https://github.com/Biki-dev/next-ai-draw-io",
+        "directory": "packages/mcp-server"
+    },
+    "homepage": "https://next-ai-drawio.jiang.jp",
+    "bugs": {
+        "url": "https://github.com/Biki-dev/next-ai-draw-io/issues"
+    },
+    "publishConfig": {
+        "access": "public"
+    },
+    "dependencies": {
+        "@modelcontextprotocol/sdk": "^1.0.4",
+        "linkedom": "^0.18.0",
+        "open": "^10.1.0",
+        "zod": "^3.24.0"
+    },
+    "devDependencies": {
+        "@types/node": "^20",
+        "tsx": "^4.19.0",
+        "typescript": "^5"
+    },
+    "engines": {
+        "node": ">=18"
+    },
+    "files": [
+        "dist"
+    ]
+}

packages/mcp-server/src/diagram-operations.ts

@@ -0,0 +1,219 @@
+/**
+ * ID-based diagram operations
+ * Copied from lib/utils.ts to avoid cross-package imports
+ */
+
+export interface DiagramOperation {
+    type: "update" | "add" | "delete"
+    cell_id: string
+    new_xml?: string
+}
+
+export interface OperationError {
+    type: "update" | "add" | "delete"
+    cellId: string
+    message: string
+}
+
+export interface ApplyOperationsResult {
+    result: string
+    errors: OperationError[]
+}
+
+/**
+ * Apply diagram operations (update/add/delete) using ID-based lookup.
+ * This replaces the text-matching approach with direct DOM manipulation.
+ *
+ * @param xmlContent - The full mxfile XML content
+ * @param operations - Array of operations to apply
+ * @returns Object with result XML and any errors
+ */
+export function applyDiagramOperations(
+    xmlContent: string,
+    operations: DiagramOperation[],
+): ApplyOperationsResult {
+    const errors: OperationError[] = []
+
+    // Parse the XML
+    const parser = new DOMParser()
+    const doc = parser.parseFromString(xmlContent, "text/xml")
+
+    // Check for parse errors
+    const parseError = doc.querySelector("parsererror")
+    if (parseError) {
+        return {
+            result: xmlContent,
+            errors: [
+                {
+                    type: "update",
+                    cellId: "",
+                    message: `XML parse error: ${parseError.textContent}`,
+                },
+            ],
+        }
+    }
+
+    // Find the root element (inside mxGraphModel)
+    const root = doc.querySelector("root")
+    if (!root) {
+        return {
+            result: xmlContent,
+            errors: [
+                {
+                    type: "update",
+                    cellId: "",
+                    message: "Could not find <root> element in XML",
+                },
+            ],
+        }
+    }
+
+    // Build a map of cell IDs to elements
+    const cellMap = new Map<string, Element>()
+    root.querySelectorAll("mxCell").forEach((cell) => {
+        const id = cell.getAttribute("id")
+        if (id) cellMap.set(id, cell)
+    })
+
+    // Process each operation
+    for (const op of operations) {
+        if (op.type === "update") {
+            const existingCell = cellMap.get(op.cell_id)
+            if (!existingCell) {
+                errors.push({
+                    type: "update",
+                    cellId: op.cell_id,
+                    message: `Cell with id="${op.cell_id}" not found`,
+                })
+                continue
+            }
+
+            if (!op.new_xml) {
+                errors.push({
+                    type: "update",
+                    cellId: op.cell_id,
+                    message: "new_xml is required for update operation",
+                })
+                continue
+            }
+
+            // Parse the new XML
+            const newDoc = parser.parseFromString(
+                `<wrapper>${op.new_xml}</wrapper>`,
+                "text/xml",
+            )
+            const newCell = newDoc.querySelector("mxCell")
+            if (!newCell) {
+                errors.push({
+                    type: "update",
+                    cellId: op.cell_id,
+                    message: "new_xml must contain an mxCell element",
+                })
+                continue
+            }
+
+            // Validate ID matches
+            const newCellId = newCell.getAttribute("id")
+            if (newCellId !== op.cell_id) {
+                errors.push({
+                    type: "update",
+                    cellId: op.cell_id,
+                    message: `ID mismatch: cell_id is "${op.cell_id}" but new_xml has id="${newCellId}"`,
+                })
+                continue
+            }
+
+            // Import and replace the node
+            const importedNode = doc.importNode(newCell, true)
+            existingCell.parentNode?.replaceChild(importedNode, existingCell)
+
+            // Update the map with the new element
+            cellMap.set(op.cell_id, importedNode)
+        } else if (op.type === "add") {
+            // Check if ID already exists
+            if (cellMap.has(op.cell_id)) {
+                errors.push({
+                    type: "add",
+                    cellId: op.cell_id,
+                    message: `Cell with id="${op.cell_id}" already exists`,
+                })
+                continue
+            }
+
+            if (!op.new_xml) {
+                errors.push({
+                    type: "add",
+                    cellId: op.cell_id,
+                    message: "new_xml is required for add operation",
+                })
+                continue
+            }
+
+            // Parse the new XML
+            const newDoc = parser.parseFromString(
+                `<wrapper>${op.new_xml}</wrapper>`,
+                "text/xml",
+            )
+            const newCell = newDoc.querySelector("mxCell")
+            if (!newCell) {
+                errors.push({
+                    type: "add",
+                    cellId: op.cell_id,
+                    message: "new_xml must contain an mxCell element",
+                })
+                continue
+            }
+
+            // Validate ID matches
+            const newCellId = newCell.getAttribute("id")
+            if (newCellId !== op.cell_id) {
+                errors.push({
+                    type: "add",
+                    cellId: op.cell_id,
+                    message: `ID mismatch: cell_id is "${op.cell_id}" but new_xml has id="${newCellId}"`,
+                })
+                continue
+            }
+
+            // Import and append the node
+            const importedNode = doc.importNode(newCell, true)
+            root.appendChild(importedNode)
+
+            // Add to map
+            cellMap.set(op.cell_id, importedNode)
+        } else if (op.type === "delete") {
+            const existingCell = cellMap.get(op.cell_id)
+            if (!existingCell) {
+                errors.push({
+                    type: "delete",
+                    cellId: op.cell_id,
+                    message: `Cell with id="${op.cell_id}" not found`,
+                })
+                continue
+            }
+
+            // Check for edges referencing this cell (warning only, still delete)
+            const referencingEdges = root.querySelectorAll(
+                `mxCell[source="${op.cell_id}"], mxCell[target="${op.cell_id}"]`,
+            )
+            if (referencingEdges.length > 0) {
+                const edgeIds = Array.from(referencingEdges)
+                    .map((e) => e.getAttribute("id"))
+                    .join(", ")
+                console.warn(
+                    `[applyDiagramOperations] Deleting cell "${op.cell_id}" which is referenced by edges: ${edgeIds}`,
+                )
+            }
+
+            // Remove the node
+            existingCell.parentNode?.removeChild(existingCell)
+            cellMap.delete(op.cell_id)
+        }
+    }
+
+    // Serialize back to string
+    const serializer = new XMLSerializer()
+    const result = serializer.serializeToString(doc)
+
+    return { result, errors }
+}

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

@@ -0,0 +1,384 @@
+/**
+ * Embedded HTTP Server for MCP
+ *
+ * Serves a static HTML page with draw.io embed and handles state sync.
+ * This eliminates the need for an external Next.js app.
+ */
+
+import http from "node:http"
+import { log } from "./logger.js"
+
+interface SessionState {
+    xml: string
+    version: number
+    lastUpdated: Date
+}
+
+// In-memory state store (shared with MCP server in same process)
+export const stateStore = new Map<string, SessionState>()
+
+let server: http.Server | null = null
+let serverPort: number = 6002
+const MAX_PORT = 6020 // Don't retry beyond this port
+const SESSION_TTL = 60 * 60 * 1000 // 1 hour
+
+/**
+ * Get state for a session
+ */
+export function getState(sessionId: string): SessionState | undefined {
+    return stateStore.get(sessionId)
+}
+
+/**
+ * Set state for a session
+ */
+export function setState(sessionId: string, xml: string): number {
+    const existing = stateStore.get(sessionId)
+    const newVersion = (existing?.version || 0) + 1
+
+    stateStore.set(sessionId, {
+        xml,
+        version: newVersion,
+        lastUpdated: new Date(),
+    })
+
+    log.debug(`State updated: session=${sessionId}, version=${newVersion}`)
+    return newVersion
+}
+
+/**
+ * Start the embedded HTTP server
+ */
+export function startHttpServer(port: number = 6002): Promise<number> {
+    return new Promise((resolve, reject) => {
+        if (server) {
+            resolve(serverPort)
+            return
+        }
+
+        serverPort = port
+        server = http.createServer(handleRequest)
+
+        server.on("error", (err: NodeJS.ErrnoException) => {
+            if (err.code === "EADDRINUSE") {
+                if (port >= MAX_PORT) {
+                    reject(
+                        new Error(
+                            `No available ports in range 6002-${MAX_PORT}`,
+                        ),
+                    )
+                    return
+                }
+                log.info(`Port ${port} in use, trying ${port + 1}`)
+                server = null
+                startHttpServer(port + 1)
+                    .then(resolve)
+                    .catch(reject)
+            } else {
+                reject(err)
+            }
+        })
+
+        server.listen(port, () => {
+            serverPort = port
+            log.info(`Embedded HTTP server running on http://localhost:${port}`)
+            resolve(port)
+        })
+    })
+}
+
+/**
+ * Stop the HTTP server
+ */
+export function stopHttpServer(): void {
+    if (server) {
+        server.close()
+        server = null
+    }
+}
+
+/**
+ * Clean up expired sessions
+ */
+function cleanupExpiredSessions(): void {
+    const now = Date.now()
+    for (const [sessionId, state] of stateStore) {
+        if (now - state.lastUpdated.getTime() > SESSION_TTL) {
+            stateStore.delete(sessionId)
+            log.info(`Cleaned up expired session: ${sessionId}`)
+        }
+    }
+}
+
+// Run cleanup every 5 minutes
+setInterval(cleanupExpiredSessions, 5 * 60 * 1000)
+
+/**
+ * Get the current server port
+ */
+export function getServerPort(): number {
+    return serverPort
+}
+
+/**
+ * Handle HTTP requests
+ */
+function handleRequest(
+    req: http.IncomingMessage,
+    res: http.ServerResponse,
+): void {
+    const url = new URL(req.url || "/", `http://localhost:${serverPort}`)
+
+    // CORS headers for local development
+    res.setHeader("Access-Control-Allow-Origin", "*")
+    res.setHeader("Access-Control-Allow-Methods", "GET, POST, OPTIONS")
+    res.setHeader("Access-Control-Allow-Headers", "Content-Type")
+
+    if (req.method === "OPTIONS") {
+        res.writeHead(204)
+        res.end()
+        return
+    }
+
+    // Route handling
+    if (url.pathname === "/" || url.pathname === "/index.html") {
+        serveHtml(req, res, url)
+    } else if (
+        url.pathname === "/api/state" ||
+        url.pathname === "/api/mcp/state"
+    ) {
+        handleStateApi(req, res, url)
+    } else if (
+        url.pathname === "/api/health" ||
+        url.pathname === "/api/mcp/health"
+    ) {
+        res.writeHead(200, { "Content-Type": "application/json" })
+        res.end(JSON.stringify({ status: "ok", mcp: true }))
+    } else {
+        res.writeHead(404)
+        res.end("Not Found")
+    }
+}
+
+/**
+ * Serve the HTML page with draw.io embed
+ */
+function serveHtml(
+    req: http.IncomingMessage,
+    res: http.ServerResponse,
+    url: URL,
+): void {
+    const sessionId = url.searchParams.get("mcp") || ""
+
+    res.writeHead(200, { "Content-Type": "text/html" })
+    res.end(getHtmlPage(sessionId))
+}
+
+/**
+ * Handle state API requests
+ */
+function handleStateApi(
+    req: http.IncomingMessage,
+    res: http.ServerResponse,
+    url: URL,
+): void {
+    if (req.method === "GET") {
+        const sessionId = url.searchParams.get("sessionId")
+        if (!sessionId) {
+            res.writeHead(400, { "Content-Type": "application/json" })
+            res.end(JSON.stringify({ error: "sessionId required" }))
+            return
+        }
+
+        const state = stateStore.get(sessionId)
+        res.writeHead(200, { "Content-Type": "application/json" })
+        res.end(
+            JSON.stringify({
+                xml: state?.xml || null,
+                version: state?.version || 0,
+                lastUpdated: state?.lastUpdated?.toISOString() || null,
+            }),
+        )
+    } else if (req.method === "POST") {
+        let body = ""
+        req.on("data", (chunk) => {
+            body += chunk
+        })
+        req.on("end", () => {
+            try {
+                const { sessionId, xml } = JSON.parse(body)
+                if (!sessionId) {
+                    res.writeHead(400, { "Content-Type": "application/json" })
+                    res.end(JSON.stringify({ error: "sessionId required" }))
+                    return
+                }
+
+                const version = setState(sessionId, xml)
+                res.writeHead(200, { "Content-Type": "application/json" })
+                res.end(JSON.stringify({ success: true, version }))
+            } catch {
+                res.writeHead(400, { "Content-Type": "application/json" })
+                res.end(JSON.stringify({ error: "Invalid JSON" }))
+            }
+        })
+    } else {
+        res.writeHead(405)
+        res.end("Method Not Allowed")
+    }
+}
+
+/**
+ * Generate the HTML page with draw.io embed
+ */
+function getHtmlPage(sessionId: string): string {
+    return `<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Draw.io MCP - ${sessionId || "No Session"}</title>
+    <style>
+        * { margin: 0; padding: 0; box-sizing: border-box; }
+        html, body { width: 100%; height: 100%; overflow: hidden; }
+        #container { width: 100%; height: 100%; display: flex; flex-direction: column; }
+        #header {
+            padding: 8px 16px;
+            background: #1a1a2e;
+            color: #eee;
+            font-family: system-ui, sans-serif;
+            font-size: 14px;
+            display: flex;
+            justify-content: space-between;
+            align-items: center;
+        }
+        #header .session { color: #888; font-size: 12px; }
+        #header .status { font-size: 12px; }
+        #header .status.connected { color: #4ade80; }
+        #header .status.disconnected { color: #f87171; }
+        #drawio { flex: 1; border: none; }
+    </style>
+</head>
+<body>
+    <div id="container">
+        <div id="header">
+            <div>
+                <strong>Draw.io MCP</strong>
+                <span class="session">${sessionId ? `Session: ${sessionId}` : "No MCP session"}</span>
+            </div>
+            <div id="status" class="status disconnected">Connecting...</div>
+        </div>
+        <iframe id="drawio" src="https://embed.diagrams.net/?embed=1&proto=json&spin=1&libraries=1"></iframe>
+    </div>
+
+    <script>
+        const sessionId = "${sessionId}";
+        const iframe = document.getElementById('drawio');
+        const statusEl = document.getElementById('status');
+
+        let currentVersion = 0;
+        let isDrawioReady = false;
+        let pendingXml = null;
+        let lastLoadedXml = null;
+
+        // Listen for messages from draw.io
+        window.addEventListener('message', (event) => {
+            if (event.origin !== 'https://embed.diagrams.net') return;
+
+            try {
+                const msg = JSON.parse(event.data);
+                handleDrawioMessage(msg);
+            } catch (e) {
+                // Ignore non-JSON messages
+            }
+        });
+
+        function handleDrawioMessage(msg) {
+            if (msg.event === 'init') {
+                isDrawioReady = true;
+                statusEl.textContent = 'Ready';
+                statusEl.className = 'status connected';
+
+                // Load pending XML if any
+                if (pendingXml) {
+                    loadDiagram(pendingXml);
+                    pendingXml = null;
+                }
+            } else if (msg.event === 'save') {
+                // User saved - push to state
+                if (msg.xml && msg.xml !== lastLoadedXml) {
+                    pushState(msg.xml);
+                }
+            } else if (msg.event === 'export') {
+                // Export completed
+                if (msg.data) {
+                    pushState(msg.data);
+                }
+            } else if (msg.event === 'autosave') {
+                // Autosave - push to state
+                if (msg.xml && msg.xml !== lastLoadedXml) {
+                    pushState(msg.xml);
+                }
+            }
+        }
+
+        function loadDiagram(xml) {
+            if (!isDrawioReady) {
+                pendingXml = xml;
+                return;
+            }
+
+            lastLoadedXml = xml;
+            iframe.contentWindow.postMessage(JSON.stringify({
+                action: 'load',
+                xml: xml,
+                autosave: 1
+            }), '*');
+        }
+
+        async function pushState(xml) {
+            if (!sessionId) return;
+
+            try {
+                const response = await fetch('/api/state', {
+                    method: 'POST',
+                    headers: { 'Content-Type': 'application/json' },
+                    body: JSON.stringify({ sessionId, xml })
+                });
+
+                if (response.ok) {
+                    const result = await response.json();
+                    currentVersion = result.version;
+                    lastLoadedXml = xml;
+                }
+            } catch (e) {
+                console.error('Failed to push state:', e);
+            }
+        }
+
+        async function pollState() {
+            if (!sessionId) return;
+
+            try {
+                const response = await fetch('/api/state?sessionId=' + encodeURIComponent(sessionId));
+                if (!response.ok) return;
+
+                const state = await response.json();
+
+                if (state.version && state.version > currentVersion && state.xml) {
+                    currentVersion = state.version;
+                    loadDiagram(state.xml);
+                }
+            } catch (e) {
+                console.error('Failed to poll state:', e);
+            }
+        }
+
+        // Start polling if we have a session
+        if (sessionId) {
+            pollState();
+            setInterval(pollState, 2000);
+        }
+    </script>
+</body>
+</html>`
+}

packages/mcp-server/src/index.ts

@@ -0,0 +1,476 @@
+#!/usr/bin/env node
+/**
+ * MCP Server for Next AI Draw.io
+ *
+ * Enables AI agents (Claude Desktop, Cursor, etc.) to generate and edit
+ * draw.io diagrams with real-time browser preview.
+ *
+ * Uses an embedded HTTP server - no external dependencies required.
+ */
+
+// Setup DOM polyfill for Node.js (required for XML operations)
+import { DOMParser } from "linkedom"
+;(globalThis as any).DOMParser = DOMParser
+
+// Create XMLSerializer polyfill using outerHTML
+class XMLSerializerPolyfill {
+    serializeToString(node: any): string {
+        if (node.outerHTML !== undefined) {
+            return node.outerHTML
+        }
+        if (node.documentElement) {
+            return node.documentElement.outerHTML
+        }
+        return ""
+    }
+}
+;(globalThis as any).XMLSerializer = XMLSerializerPolyfill
+
+import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js"
+import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js"
+import open from "open"
+import { z } from "zod"
+import {
+    applyDiagramOperations,
+    type DiagramOperation,
+} from "./diagram-operations.js"
+import {
+    getServerPort,
+    getState,
+    setState,
+    startHttpServer,
+} from "./http-server.js"
+import { log } from "./logger.js"
+
+// Server configuration
+const config = {
+    port: parseInt(process.env.PORT || "6002"),
+}
+
+// Session state (single session for simplicity)
+let currentSession: {
+    id: string
+    xml: string
+    version: number
+} | null = null
+
+// Create MCP server
+const server = new McpServer({
+    name: "next-ai-drawio",
+    version: "0.1.2",
+})
+
+// Register prompt with workflow guidance
+server.prompt(
+    "diagram-workflow",
+    "Guidelines for creating and editing draw.io diagrams",
+    () => ({
+        messages: [
+            {
+                role: "user",
+                content: {
+                    type: "text",
+                    text: `# Draw.io Diagram Workflow Guidelines
+
+## Creating a New Diagram
+1. Call start_session to open the browser preview
+2. Use display_diagram with complete mxGraphModel XML to create a new diagram
+
+## Adding Elements to Existing Diagram
+1. Use edit_diagram with "add" operation
+2. Provide a unique cell_id and complete mxCell XML
+3. No need to call get_diagram first - the server fetches latest state automatically
+
+## Modifying or Deleting Existing Elements
+1. FIRST call get_diagram to see current cell IDs and structure
+2. THEN call edit_diagram with "update" or "delete" operations
+3. For update, provide the cell_id and complete new mxCell XML
+
+## Important Notes
+- display_diagram REPLACES the entire diagram - only use for new diagrams
+- edit_diagram PRESERVES user's manual changes (fetches browser state first)
+- Always use unique cell_ids when adding elements (e.g., "shape-1", "arrow-2")`,
+                },
+            },
+        ],
+    }),
+)
+
+// Tool: start_session
+server.registerTool(
+    "start_session",
+    {
+        description:
+            "Start a new diagram session and open the browser for real-time preview. " +
+            "Starts an embedded server and opens a browser window with draw.io. " +
+            "The browser will show diagram updates as they happen.",
+        inputSchema: {},
+    },
+    async () => {
+        try {
+            // Start embedded HTTP server
+            const port = await startHttpServer(config.port)
+
+            // Create session
+            const sessionId = `mcp-${Date.now().toString(36)}-${Math.random().toString(36).substring(2, 8)}`
+            currentSession = {
+                id: sessionId,
+                xml: "",
+                version: 0,
+            }
+
+            // Open browser
+            const browserUrl = `http://localhost:${port}?mcp=${sessionId}`
+            await open(browserUrl)
+
+            log.info(`Started session ${sessionId}, browser at ${browserUrl}`)
+
+            return {
+                content: [
+                    {
+                        type: "text",
+                        text: `Session started successfully!\n\nSession ID: ${sessionId}\nBrowser URL: ${browserUrl}\n\nThe browser will now show real-time diagram updates.`,
+                    },
+                ],
+            }
+        } catch (error) {
+            const message =
+                error instanceof Error ? error.message : String(error)
+            log.error("start_session failed:", message)
+            return {
+                content: [{ type: "text", text: `Error: ${message}` }],
+                isError: true,
+            }
+        }
+    },
+)
+
+// Tool: display_diagram
+server.registerTool(
+    "display_diagram",
+    {
+        description:
+            "Display a NEW draw.io diagram from XML. REPLACES the entire diagram. " +
+            "Use this for creating new diagrams from scratch. " +
+            "To ADD elements to an existing diagram, use edit_diagram with 'add' operation instead. " +
+            "You should generate valid draw.io/mxGraph XML format.",
+        inputSchema: {
+            xml: z
+                .string()
+                .describe("The draw.io XML to display (mxGraphModel format)"),
+        },
+    },
+    async ({ xml }) => {
+        try {
+            if (!currentSession) {
+                return {
+                    content: [
+                        {
+                            type: "text",
+                            text: "Error: No active session. Please call start_session first.",
+                        },
+                    ],
+                    isError: true,
+                }
+            }
+
+            log.info(`Displaying diagram, ${xml.length} chars`)
+
+            // Update session state
+            currentSession.xml = xml
+            currentSession.version++
+
+            // Push to embedded server state
+            setState(currentSession.id, xml)
+
+            log.info(`Diagram displayed successfully`)
+
+            return {
+                content: [
+                    {
+                        type: "text",
+                        text: `Diagram displayed successfully!\n\nThe diagram is now visible in your browser.\n\nXML length: ${xml.length} characters`,
+                    },
+                ],
+            }
+        } catch (error) {
+            const message =
+                error instanceof Error ? error.message : String(error)
+            log.error("display_diagram failed:", message)
+            return {
+                content: [{ type: "text", text: `Error: ${message}` }],
+                isError: true,
+            }
+        }
+    },
+)
+
+// Tool: edit_diagram
+server.registerTool(
+    "edit_diagram",
+    {
+        description:
+            "Edit the current diagram by ID-based operations (update/add/delete cells). " +
+            "ALWAYS fetches the latest state from browser first, so user's manual changes are preserved.\n\n" +
+            "IMPORTANT workflow:\n" +
+            "- For ADD operations: Can use directly - just provide new unique cell_id and new_xml.\n" +
+            "- For UPDATE/DELETE: Call get_diagram FIRST to see current cell IDs, then edit.\n\n" +
+            "Operations:\n" +
+            "- add: Add a new cell. Provide cell_id (new unique id) and new_xml.\n" +
+            "- update: Replace an existing cell by its id. Provide cell_id and complete new_xml.\n" +
+            "- delete: Remove a cell by its id. Only cell_id is needed.\n\n" +
+            "For add/update, new_xml must be a complete mxCell element including mxGeometry.",
+        inputSchema: {
+            operations: z
+                .array(
+                    z.object({
+                        type: z
+                            .enum(["update", "add", "delete"])
+                            .describe("Operation type"),
+                        cell_id: z.string().describe("The id of the mxCell"),
+                        new_xml: z
+                            .string()
+                            .optional()
+                            .describe(
+                                "Complete mxCell XML element (required for update/add)",
+                            ),
+                    }),
+                )
+                .describe("Array of operations to apply"),
+        },
+    },
+    async ({ operations }) => {
+        try {
+            if (!currentSession) {
+                return {
+                    content: [
+                        {
+                            type: "text",
+                            text: "Error: No active session. Please call start_session first.",
+                        },
+                    ],
+                    isError: true,
+                }
+            }
+
+            // Fetch latest state from browser
+            const browserState = getState(currentSession.id)
+            if (browserState?.xml) {
+                currentSession.xml = browserState.xml
+                log.info("Fetched latest diagram state from browser")
+            }
+
+            if (!currentSession.xml) {
+                return {
+                    content: [
+                        {
+                            type: "text",
+                            text: "Error: No diagram to edit. Please create a diagram first with display_diagram.",
+                        },
+                    ],
+                    isError: true,
+                }
+            }
+
+            log.info(`Editing diagram with ${operations.length} operation(s)`)
+
+            // Apply operations
+            const { result, errors } = applyDiagramOperations(
+                currentSession.xml,
+                operations as DiagramOperation[],
+            )
+
+            if (errors.length > 0) {
+                const errorMessages = errors
+                    .map((e) => `${e.type} ${e.cellId}: ${e.message}`)
+                    .join("\n")
+                log.warn(`Edit had ${errors.length} error(s): ${errorMessages}`)
+            }
+
+            // Update state
+            currentSession.xml = result
+            currentSession.version++
+
+            // Push to embedded server
+            setState(currentSession.id, result)
+
+            log.info(`Diagram edited successfully`)
+
+            const successMsg = `Diagram edited successfully!\n\nApplied ${operations.length} operation(s).`
+            const errorMsg =
+                errors.length > 0
+                    ? `\n\nWarnings:\n${errors.map((e) => `- ${e.type} ${e.cellId}: ${e.message}`).join("\n")}`
+                    : ""
+
+            return {
+                content: [
+                    {
+                        type: "text",
+                        text: successMsg + errorMsg,
+                    },
+                ],
+            }
+        } catch (error) {
+            const message =
+                error instanceof Error ? error.message : String(error)
+            log.error("edit_diagram failed:", message)
+            return {
+                content: [{ type: "text", text: `Error: ${message}` }],
+                isError: true,
+            }
+        }
+    },
+)
+
+// Tool: get_diagram
+server.registerTool(
+    "get_diagram",
+    {
+        description:
+            "Get the current diagram XML (fetches latest from browser, including user's manual edits). " +
+            "Call this BEFORE edit_diagram if you need to update or delete existing elements, " +
+            "so you can see the current cell IDs and structure.",
+    },
+    async () => {
+        try {
+            if (!currentSession) {
+                return {
+                    content: [
+                        {
+                            type: "text",
+                            text: "Error: No active session. Please call start_session first.",
+                        },
+                    ],
+                    isError: true,
+                }
+            }
+
+            // Fetch latest state from browser
+            const browserState = getState(currentSession.id)
+            if (browserState?.xml) {
+                currentSession.xml = browserState.xml
+            }
+
+            if (!currentSession.xml) {
+                return {
+                    content: [
+                        {
+                            type: "text",
+                            text: "No diagram exists yet. Use display_diagram to create one.",
+                        },
+                    ],
+                }
+            }
+
+            return {
+                content: [
+                    {
+                        type: "text",
+                        text: `Current diagram XML:\n\n${currentSession.xml}`,
+                    },
+                ],
+            }
+        } catch (error) {
+            const message =
+                error instanceof Error ? error.message : String(error)
+            log.error("get_diagram failed:", message)
+            return {
+                content: [{ type: "text", text: `Error: ${message}` }],
+                isError: true,
+            }
+        }
+    },
+)
+
+// Tool: export_diagram
+server.registerTool(
+    "export_diagram",
+    {
+        description: "Export the current diagram to a .drawio file.",
+        inputSchema: {
+            path: z
+                .string()
+                .describe(
+                    "File path to save the diagram (e.g., ./diagram.drawio)",
+                ),
+        },
+    },
+    async ({ path }) => {
+        try {
+            if (!currentSession) {
+                return {
+                    content: [
+                        {
+                            type: "text",
+                            text: "Error: No active session. Please call start_session first.",
+                        },
+                    ],
+                    isError: true,
+                }
+            }
+
+            // Fetch latest state
+            const browserState = getState(currentSession.id)
+            if (browserState?.xml) {
+                currentSession.xml = browserState.xml
+            }
+
+            if (!currentSession.xml) {
+                return {
+                    content: [
+                        {
+                            type: "text",
+                            text: "Error: No diagram to export. Please create a diagram first.",
+                        },
+                    ],
+                    isError: true,
+                }
+            }
+
+            const fs = await import("node:fs/promises")
+            const nodePath = await import("node:path")
+
+            let filePath = path
+            if (!filePath.endsWith(".drawio")) {
+                filePath = `${filePath}.drawio`
+            }
+
+            const absolutePath = nodePath.resolve(filePath)
+            await fs.writeFile(absolutePath, currentSession.xml, "utf-8")
+
+            log.info(`Diagram exported to ${absolutePath}`)
+
+            return {
+                content: [
+                    {
+                        type: "text",
+                        text: `Diagram exported successfully!\n\nFile: ${absolutePath}\nSize: ${currentSession.xml.length} characters`,
+                    },
+                ],
+            }
+        } catch (error) {
+            const message =
+                error instanceof Error ? error.message : String(error)
+            log.error("export_diagram failed:", message)
+            return {
+                content: [{ type: "text", text: `Error: ${message}` }],
+                isError: true,
+            }
+        }
+    },
+)
+
+// Start the MCP server
+async function main() {
+    log.info("Starting MCP server for Next AI Draw.io (embedded mode)...")
+
+    const transport = new StdioServerTransport()
+    await server.connect(transport)
+
+    log.info("MCP server running on stdio")
+}
+
+main().catch((error) => {
+    log.error("Fatal error:", error)
+    process.exit(1)
+})

packages/mcp-server/src/logger.ts

@@ -0,0 +1,24 @@
+/**
+ * Logger for MCP server
+ *
+ * CRITICAL: MCP servers communicate via STDIO (stdin/stdout).
+ * Using console.log() will corrupt the JSON-RPC protocol messages.
+ * ALL logging MUST use console.error() which writes to stderr.
+ */
+
+export const log = {
+    info: (msg: string, ...args: unknown[]) => {
+        console.error(`[MCP-DrawIO] [INFO] ${msg}`, ...args)
+    },
+    error: (msg: string, ...args: unknown[]) => {
+        console.error(`[MCP-DrawIO] [ERROR] ${msg}`, ...args)
+    },
+    debug: (msg: string, ...args: unknown[]) => {
+        if (process.env.DEBUG === "true") {
+            console.error(`[MCP-DrawIO] [DEBUG] ${msg}`, ...args)
+        }
+    },
+    warn: (msg: string, ...args: unknown[]) => {
+        console.error(`[MCP-DrawIO] [WARN] ${msg}`, ...args)
+    },
+}

packages/mcp-server/tsconfig.json

@@ -0,0 +1,19 @@
+{
+    "compilerOptions": {
+        "target": "ES2022",
+        "module": "Node16",
+        "moduleResolution": "Node16",
+        "outDir": "./dist",
+        "rootDir": "./src",
+        "strict": true,
+        "esModuleInterop": true,
+        "skipLibCheck": true,
+        "forceConsistentCasingInFileNames": true,
+        "declaration": true,
+        "declarationMap": true,
+        "sourceMap": true,
+        "resolveJsonModule": true
+    },
+    "include": ["src/**/*"],
+    "exclude": ["node_modules", "dist"]
+}

scripts/test-diagram-operations.mjs

@@ -0,0 +1,251 @@
+/**
+ * Simple test script for applyDiagramOperations function
+ * Run with: node scripts/test-diagram-operations.mjs
+ */
+
+import { JSDOM } from "jsdom"
+
+// Set up DOMParser for Node.js environment
+const dom = new JSDOM()
+globalThis.DOMParser = dom.window.DOMParser
+globalThis.XMLSerializer = dom.window.XMLSerializer
+
+// Import the function (we'll inline it since it's not ESM exported)
+function applyDiagramOperations(xmlContent, operations) {
+    const errors = []
+    const parser = new DOMParser()
+    const doc = parser.parseFromString(xmlContent, "text/xml")
+
+    const parseError = doc.querySelector("parsererror")
+    if (parseError) {
+        return {
+            result: xmlContent,
+            errors: [{ type: "update", cellId: "", message: `XML parse error: ${parseError.textContent}` }],
+        }
+    }
+
+    const root = doc.querySelector("root")
+    if (!root) {
+        return {
+            result: xmlContent,
+            errors: [{ type: "update", cellId: "", message: "Could not find <root> element in XML" }],
+        }
+    }
+
+    const cellMap = new Map()
+    root.querySelectorAll("mxCell").forEach((cell) => {
+        const id = cell.getAttribute("id")
+        if (id) cellMap.set(id, cell)
+    })
+
+    for (const op of operations) {
+        if (op.type === "update") {
+            const existingCell = cellMap.get(op.cell_id)
+            if (!existingCell) {
+                errors.push({ type: "update", cellId: op.cell_id, message: `Cell with id="${op.cell_id}" not found` })
+                continue
+            }
+            if (!op.new_xml) {
+                errors.push({ type: "update", cellId: op.cell_id, message: "new_xml is required for update operation" })
+                continue
+            }
+            const newDoc = parser.parseFromString(`<wrapper>${op.new_xml}</wrapper>`, "text/xml")
+            const newCell = newDoc.querySelector("mxCell")
+            if (!newCell) {
+                errors.push({ type: "update", cellId: op.cell_id, message: "new_xml must contain an mxCell element" })
+                continue
+            }
+            const newCellId = newCell.getAttribute("id")
+            if (newCellId !== op.cell_id) {
+                errors.push({ type: "update", cellId: op.cell_id, message: `ID mismatch: cell_id is "${op.cell_id}" but new_xml has id="${newCellId}"` })
+                continue
+            }
+            const importedNode = doc.importNode(newCell, true)
+            existingCell.parentNode?.replaceChild(importedNode, existingCell)
+            cellMap.set(op.cell_id, importedNode)
+        } else if (op.type === "add") {
+            if (cellMap.has(op.cell_id)) {
+                errors.push({ type: "add", cellId: op.cell_id, message: `Cell with id="${op.cell_id}" already exists` })
+                continue
+            }
+            if (!op.new_xml) {
+                errors.push({ type: "add", cellId: op.cell_id, message: "new_xml is required for add operation" })
+                continue
+            }
+            const newDoc = parser.parseFromString(`<wrapper>${op.new_xml}</wrapper>`, "text/xml")
+            const newCell = newDoc.querySelector("mxCell")
+            if (!newCell) {
+                errors.push({ type: "add", cellId: op.cell_id, message: "new_xml must contain an mxCell element" })
+                continue
+            }
+            const newCellId = newCell.getAttribute("id")
+            if (newCellId !== op.cell_id) {
+                errors.push({ type: "add", cellId: op.cell_id, message: `ID mismatch: cell_id is "${op.cell_id}" but new_xml has id="${newCellId}"` })
+                continue
+            }
+            const importedNode = doc.importNode(newCell, true)
+            root.appendChild(importedNode)
+            cellMap.set(op.cell_id, importedNode)
+        } else if (op.type === "delete") {
+            const existingCell = cellMap.get(op.cell_id)
+            if (!existingCell) {
+                errors.push({ type: "delete", cellId: op.cell_id, message: `Cell with id="${op.cell_id}" not found` })
+                continue
+            }
+            existingCell.parentNode?.removeChild(existingCell)
+            cellMap.delete(op.cell_id)
+        }
+    }
+
+    const serializer = new XMLSerializer()
+    const result = serializer.serializeToString(doc)
+    return { result, errors }
+}
+
+// Test data
+const sampleXml = `<?xml version="1.0" encoding="UTF-8"?>
+<mxfile>
+  <diagram>
+    <mxGraphModel>
+      <root>
+        <mxCell id="0"/>
+        <mxCell id="1" parent="0"/>
+        <mxCell id="2" value="Box A" style="rounded=1;" vertex="1" parent="1">
+          <mxGeometry x="100" y="100" width="120" height="60" as="geometry"/>
+        </mxCell>
+        <mxCell id="3" value="Box B" style="rounded=1;" vertex="1" parent="1">
+          <mxGeometry x="300" y="100" width="120" height="60" as="geometry"/>
+        </mxCell>
+        <mxCell id="4" value="" style="edgeStyle=orthogonalEdgeStyle;" edge="1" parent="1" source="2" target="3">
+          <mxGeometry relative="1" as="geometry"/>
+        </mxCell>
+      </root>
+    </mxGraphModel>
+  </diagram>
+</mxfile>`
+
+let passed = 0
+let failed = 0
+
+function test(name, fn) {
+    try {
+        fn()
+        console.log(`✓ ${name}`)
+        passed++
+    } catch (e) {
+        console.log(`✗ ${name}`)
+        console.log(`  Error: ${e.message}`)
+        failed++
+    }
+}
+
+function assert(condition, message) {
+    if (!condition) throw new Error(message || "Assertion failed")
+}
+
+// Tests
+test("Update operation changes cell value", () => {
+    const { result, errors } = applyDiagramOperations(sampleXml, [
+        {
+            type: "update",
+            cell_id: "2",
+            new_xml: '<mxCell id="2" value="Updated Box A" style="rounded=1;" vertex="1" parent="1"><mxGeometry x="100" y="100" width="120" height="60" as="geometry"/></mxCell>',
+        },
+    ])
+    assert(errors.length === 0, `Expected no errors, got: ${JSON.stringify(errors)}`)
+    assert(result.includes('value="Updated Box A"'), "Updated value should be in result")
+    assert(!result.includes('value="Box A"'), "Old value should not be in result")
+})
+
+test("Update operation fails for non-existent cell", () => {
+    const { errors } = applyDiagramOperations(sampleXml, [
+        { type: "update", cell_id: "999", new_xml: '<mxCell id="999" value="Test"/>' },
+    ])
+    assert(errors.length === 1, "Should have one error")
+    assert(errors[0].message.includes("not found"), "Error should mention not found")
+})
+
+test("Update operation fails on ID mismatch", () => {
+    const { errors } = applyDiagramOperations(sampleXml, [
+        { type: "update", cell_id: "2", new_xml: '<mxCell id="WRONG" value="Test"/>' },
+    ])
+    assert(errors.length === 1, "Should have one error")
+    assert(errors[0].message.includes("ID mismatch"), "Error should mention ID mismatch")
+})
+
+test("Add operation creates new cell", () => {
+    const { result, errors } = applyDiagramOperations(sampleXml, [
+        {
+            type: "add",
+            cell_id: "new1",
+            new_xml: '<mxCell id="new1" value="New Box" style="rounded=1;" vertex="1" parent="1"><mxGeometry x="500" y="100" width="120" height="60" as="geometry"/></mxCell>',
+        },
+    ])
+    assert(errors.length === 0, `Expected no errors, got: ${JSON.stringify(errors)}`)
+    assert(result.includes('id="new1"'), "New cell should be in result")
+    assert(result.includes('value="New Box"'), "New cell value should be in result")
+})
+
+test("Add operation fails for duplicate ID", () => {
+    const { errors } = applyDiagramOperations(sampleXml, [
+        { type: "add", cell_id: "2", new_xml: '<mxCell id="2" value="Duplicate"/>' },
+    ])
+    assert(errors.length === 1, "Should have one error")
+    assert(errors[0].message.includes("already exists"), "Error should mention already exists")
+})
+
+test("Add operation fails on ID mismatch", () => {
+    const { errors } = applyDiagramOperations(sampleXml, [
+        { type: "add", cell_id: "new1", new_xml: '<mxCell id="WRONG" value="Test"/>' },
+    ])
+    assert(errors.length === 1, "Should have one error")
+    assert(errors[0].message.includes("ID mismatch"), "Error should mention ID mismatch")
+})
+
+test("Delete operation removes cell", () => {
+    const { result, errors } = applyDiagramOperations(sampleXml, [{ type: "delete", cell_id: "3" }])
+    assert(errors.length === 0, `Expected no errors, got: ${JSON.stringify(errors)}`)
+    assert(!result.includes('id="3"'), "Deleted cell should not be in result")
+    assert(result.includes('id="2"'), "Other cells should remain")
+})
+
+test("Delete operation fails for non-existent cell", () => {
+    const { errors } = applyDiagramOperations(sampleXml, [{ type: "delete", cell_id: "999" }])
+    assert(errors.length === 1, "Should have one error")
+    assert(errors[0].message.includes("not found"), "Error should mention not found")
+})
+
+test("Multiple operations in sequence", () => {
+    const { result, errors } = applyDiagramOperations(sampleXml, [
+        {
+            type: "update",
+            cell_id: "2",
+            new_xml: '<mxCell id="2" value="Updated" style="rounded=1;" vertex="1" parent="1"><mxGeometry x="100" y="100" width="120" height="60" as="geometry"/></mxCell>',
+        },
+        {
+            type: "add",
+            cell_id: "new1",
+            new_xml: '<mxCell id="new1" value="Added" style="rounded=1;" vertex="1" parent="1"><mxGeometry x="500" y="100" width="120" height="60" as="geometry"/></mxCell>',
+        },
+        { type: "delete", cell_id: "3" },
+    ])
+    assert(errors.length === 0, `Expected no errors, got: ${JSON.stringify(errors)}`)
+    assert(result.includes('value="Updated"'), "Updated value should be present")
+    assert(result.includes('id="new1"'), "Added cell should be present")
+    assert(!result.includes('id="3"'), "Deleted cell should not be present")
+})
+
+test("Invalid XML returns parse error", () => {
+    const { errors } = applyDiagramOperations("<not valid xml", [{ type: "delete", cell_id: "1" }])
+    assert(errors.length === 1, "Should have one error")
+})
+
+test("Missing root element returns error", () => {
+    const { errors } = applyDiagramOperations("<mxfile></mxfile>", [{ type: "delete", cell_id: "1" }])
+    assert(errors.length === 1, "Should have one error")
+    assert(errors[0].message.includes("root"), "Error should mention root element")
+})
+
+// Summary
+console.log(`\n${passed} passed, ${failed} failed`)
+process.exit(failed > 0 ? 1 : 0)

tsconfig.json

@@ -29,5 +29,5 @@
         ".next/types/**/*.ts",
         ".next/dev/types/**/*.ts"
     ],
-    "exclude": ["node_modules"]
+    "exclude": ["node_modules", "packages"]
 }