test: read the failed edit's output without unsafe optional chaining

fix(chat): the AI reads and draws the page the user is viewing
The model always got the first page and display_diagram replaced the whole file with one page, so drawing on page 3 of a multi-page file deleted the other pages (#241), and edits went to page 1 while the user looked at another page. Now a turn records the page the user is viewing when the message is sent. That page's model goes to the model (also as previousXml, on regenerate and in edit_diagram error messages), selected shapes are sent on any page, display_diagram and append_diagram replace only that page (a drawing that brings several pages still replaces the file), edit_diagram targets it, and the streaming preview draws on it. Compact cells and default styles take the layer and the edges of that page, in the preview and in editDiagram. The editor bridge replaces the current page in place when the other pages are unchanged, so Ctrl+Z undoes an AI change on a multi-page file in one step; when a full load is needed, the user's page is shown again afterwards. Version summaries and the compare dialog count the page the change was made on.
2026-10-11 03:59:58 +08:00 · 2026-10-10 22:43:05 +09:00 · 2026-10-10 22:14:50 +09:00 · 2026-10-10 21:58:21 +09:00 · 2026-10-10 21:53:37 +09:00
43 changed files with 4625 additions and 2085 deletions
@@ -12,13 +12,13 @@ jobs:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6
        with:
          ref: ${{ github.event.pull_request.head.sha }}
          token: ${{ secrets.GITHUB_TOKEN }}

      - name: Setup Node.js
-        uses: actions/setup-node@v7
+        uses: actions/setup-node@v6
        with:
          node-version: '24'

@@ -20,10 +20,10 @@ jobs:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6

      - name: Setup Node.js
-        uses: actions/setup-node@v7
+        uses: actions/setup-node@v6
        with:
          node-version: '24'
          cache: 'npm'
@@ -26,14 +26,14 @@ jobs:
      
    steps:
      - name: Checkout repository
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6

      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v4
+        uses: docker/setup-buildx-action@v3

      - name: Log in to GitHub Container Registry
        if: github.event_name != 'pull_request'
-        uses: docker/login-action@v4
+        uses: docker/login-action@v3
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
@@ -41,7 +41,7 @@ jobs:

      - name: Extract metadata (tags, labels)
        id: meta
-        uses: docker/metadata-action@v6
+        uses: docker/metadata-action@v5
        with:
          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
          tags: |
@@ -54,7 +54,7 @@ jobs:
            type=raw,value=latest,enable={{is_default_branch}}

      - name: Build and push Docker image
-        uses: docker/build-push-action@v7
+        uses: docker/build-push-action@v6
        with:
          context: .
          push: ${{ github.event_name != 'pull_request' }}
@@ -71,7 +71,7 @@ jobs:
      # 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@v6
+        uses: aws-actions/configure-aws-credentials@v5
        with:
          aws-access-key-id: ${{ secrets.AWS_ACCESS_KEY_ID }}
          aws-secret-access-key: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
@@ -26,10 +26,10 @@ jobs:
    runs-on: ${{ matrix.os }}
    steps:
      - name: Checkout code
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6

      - name: Setup Node.js
-        uses: actions/setup-node@v7
+        uses: actions/setup-node@v6
        with:
          node-version: 24
          cache: "npm"
@@ -50,10 +50,10 @@ jobs:
    runs-on: windows-latest
    steps:
      - name: Checkout code
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6

      - name: Setup Node.js
-        uses: actions/setup-node@v7
+        uses: actions/setup-node@v6
        with:
          node-version: 24
          cache: "npm"
@@ -69,7 +69,7 @@ jobs:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}

      - name: Upload unsigned artifacts for signing
-        uses: actions/upload-artifact@v7
+        uses: actions/upload-artifact@v6
        id: upload-unsigned
        with:
          name: windows-unsigned
@@ -77,7 +77,7 @@ jobs:
          retention-days: 1

      - name: Sign with SignPath
-        uses: signpath/github-action-submit-signing-request@v3
+        uses: signpath/github-action-submit-signing-request@v2
        with:
          api-token: ${{ secrets.SIGNPATH_API_TOKEN }}
          organization-id: '880a211d-2cd3-4e7b-8d04-3d1f8eb39df5'
@@ -92,7 +92,7 @@ jobs:
          output-artifact-directory: release-signed

      - name: Upload signed artifacts to release
-        uses: softprops/action-gh-release@v3
+        uses: softprops/action-gh-release@v2
        with:
          files: release-signed/*.exe
        env:
@@ -28,10 +28,10 @@ jobs:
        working-directory: packages/mcp-server
    steps:
      - name: Checkout
-        uses: actions/checkout@v7
+        uses: actions/checkout@v6

      - name: Setup Node.js
-        uses: actions/setup-node@v7
+        uses: actions/setup-node@v6
        with:
          node-version: 24
          cache: "npm"
@@ -11,12 +11,12 @@ jobs:
    name: Lint & Unit Tests
    runs-on: ubuntu-latest
    steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@v6

      - name: Setup Node.js
-        uses: actions/setup-node@v7
+        uses: actions/setup-node@v6
        with:
-          node-version: "24"
+          node-version: "20"
          cache: "npm"

      - name: Install dependencies
@@ -52,19 +52,19 @@ jobs:
      matrix:
        shard: [1, 2, 3, 4, 5, 6]
    steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@v6

      - name: Setup Node.js
-        uses: actions/setup-node@v7
+        uses: actions/setup-node@v6
        with:
-          node-version: "24"
+          node-version: "20"
          cache: "npm"

      - name: Install dependencies
        run: npm ci

      - name: Cache Playwright browsers
-        uses: actions/cache@v6
+        uses: actions/cache@v5
        id: playwright-cache
        with:
          path: ~/.cache/ms-playwright
@@ -87,7 +87,7 @@ jobs:
          CI: true

      - name: Upload test results
-        uses: actions/upload-artifact@v7
+        uses: actions/upload-artifact@v6
        if: always()
        with:
          name: playwright-report-${{ matrix.shard }}
@@ -55,12 +55,16 @@ import { allowPrivateUrls, isPrivateUrl } from "@/lib/ssrf-protection"
 import { getSystemPrompt } from "@/lib/system-prompts"
 import { normalizeBaseUrl } from "@/lib/types/model-config"
 import { getUserIdFromRequest } from "@/lib/user-id"
+import { foldCells } from "@/packages/mcp-server/src/compact-cells.ts"
 import { hasCells } from "@/packages/mcp-server/src/pages.ts"
 import {
    getShapeLibrary,
    SHAPE_LIBRARY_LIST,
 } from "@/packages/mcp-server/src/shape-library.ts"
-import { SWIMLANE_EXAMPLE } from "@/packages/mcp-server/src/xml-examples.ts"
+import {
+    STYLE_CLASS_EXAMPLE,
+    SWIMLANE_EXAMPLE,
+} from "@/packages/mcp-server/src/xml-examples.ts"

 // No explicit cap: a reasoning model can spend minutes planning before it emits
 // the tool call, so take whatever the host allows. Vercel's own default is 300s,
@@ -520,18 +524,20 @@ ${userInputText}
        SINGLE_SYSTEM_PROVIDERS.has(resolvedProvider) || isCustomOpenAIEndpoint

    const selectionContext = formatSelectionContext(body.selectedCells)
+    // The model reads the diagram in the compact notation it writes
+    // (compact-cells.ts); the canvas itself keeps the full XML
    const xmlContext = `${
        previousXml
            ? `Previous diagram XML (before user's last message):
 """xml
-${previousXml}
+${foldCells(previousXml)}
 """

 `
            : ""
-    }Current diagram XML (AUTHORITATIVE - the source of truth):
+    }Current diagram XML (AUTHORITATIVE - the source of truth), shown in the same compact notation you write (shapes with x, y, w, h; edges with source and target):
 """xml
-${xml || ""}
+${foldCells(xml || "")}
 """

 IMPORTANT: The "Current diagram XML" is the SINGLE SOURCE OF TRUTH for what's on the canvas right now. The user can manually add, delete, or modify shapes directly in draw.io. Always count and describe elements based on the CURRENT XML, not on what you previously generated. If both previous and current XML are shown, compare them to understand what the user changed.${selectionContext ? `\n\n${selectionContext}` : ""}`
@@ -659,19 +665,24 @@ IMPORTANT: The "Current diagram XML" is the SINGLE SOURCE OF TRUTH for what's on
        tools: {
            // Client-side tool that will be executed on the client
            display_diagram: {
-                description: `Display a diagram on draw.io. Pass ONLY the mxCell elements - wrapper tags and root cells are added automatically.
+                description: `Display a diagram on draw.io. Pass ONLY the mxStyle definitions and the mxCell elements - wrapper tags and root cells are added automatically.

 VALIDATION RULES (XML will be rejected if violated):
-1. Generate ONLY mxCell elements - NO wrapper tags (<mxfile>, <mxGraphModel>, <root>)
+1. Generate ONLY mxStyle definitions and 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)
+5. parent defaults to "1"; write parent="<container-id>" only for shapes inside a container
 6. Escape special chars in values: &lt; &gt; &amp; &quot;

+A shape is one self-closing mxCell with x, y, w and h; an edge is one with source and target (a cell with source or target is always an edge). vertex="1", edge="1", parent="1" and the mxGeometry element are added automatically. Write parent only for a shape inside a container, and an mxGeometry element only for edge waypoints or for a separate label cell placed on an edge: <mxCell id="9" value="yes" style="edgeLabel;" parent="<edge id>" connectable="0"><mxGeometry x="-0.5" relative="1" as="geometry"/></mxCell>. An edge's own text simply goes in its value.
+
 Example (generate ONLY this - no wrapper tags):
 ${SWIMLANE_EXAMPLE}

+Styles: define a style used by several cells ONCE with <mxStyle name="..." value="..."/> before the cells and use the name in style like a CSS class; overrides after the name win. Name only styles that two or more cells share; names must not be draw.io's own style names (text, ellipse, rhombus, swimlane, label, image, blue, green, red, gray, yellow, orange, purple, pink). A definition applies to the call it is in. html=1 and whiteSpace=wrap are added automatically, never write them. Labels are HTML: use &lt;br&gt; for a line break, never \\n; a literal < or > is written &amp;lt; or &amp;gt;.
+${STYLE_CLASS_EXAMPLE}
+
 Notes:
 - For AWS diagrams, use **AWS 2025 icons**.
 - For animated connectors, add "flowAnimation=1" to edge style.
@@ -690,12 +701,12 @@ Operations:
 - add: Add a new cell. Provide cell_id (new unique id) and new_xml.
 - delete: Remove a cell. Cascade is automatic: children AND edges (source/target) are auto-deleted. Only specify ONE cell_id.

-For update/add, new_xml must be a complete mxCell element including mxGeometry.
+For update/add, new_xml is the complete mxCell in the compact form (a shape with x, y, w, h; an edge with source and target), with its complete style (named styles are not available in edit_diagram).

 ⚠️ JSON ESCAPING: Every " inside new_xml MUST be escaped as \\". Example: id=\\"5\\" value=\\"Label\\"

 Example - Add a rectangle:
-{"operations": [{"operation": "add", "cell_id": "rect-1", "new_xml": "<mxCell id=\\"rect-1\\" value=\\"Hello\\" style=\\"rounded=0;\\" vertex=\\"1\\" parent=\\"1\\"><mxGeometry x=\\"100\\" y=\\"100\\" width=\\"120\\" height=\\"60\\" as=\\"geometry\\"/></mxCell>"}]}
+{"operations": [{"operation": "add", "cell_id": "rect-1", "new_xml": "<mxCell id=\\"rect-1\\" value=\\"Hello\\" style=\\"rounded=1;\\" x=\\"100\\" y=\\"100\\" w=\\"120\\" h=\\"60\\"/>"}]}

 Example - Delete container (children & edges auto-deleted):
 {"operations": [{"operation": "delete", "cell_id": "2"}]}`,
@@ -735,7 +746,7 @@ CRITICAL INSTRUCTIONS:
 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.`,
+Example: If previous output ended with '<mxCell id="x" style="rounded=1', continue with ';" x="40" y="40" w="120" h="60"/>' and complete the remaining elements.`,
                inputSchema: z.object({
                    xml: z
                        .string()
@@ -46,11 +46,6 @@ export function CanvasStage({
    const engine = useChatEngine()
    const isDark = useSettingsStore((s) => s.isDark)
    const hasEditor = useCanvasStore((s) => s.hasEditor)
-    // The model sees the first page only, so asking about shapes elsewhere
-    // would change the wrong page
-    const onFirstPage = useCanvasStore(
-        (s) => s.pages.length === 0 || s.pages[0]?.id === s.currentPageId,
-    )
    // Canvas width when the chat panel starts sliding in or out
    const slideStartWidthRef = useRef(0)

@@ -168,7 +163,7 @@ export function CanvasStage({
                <SelectionAsk
                    width={size.width}
                    height={size.height}
-                    hidden={engine.isBusy || !onFirstPage}
+                    hidden={engine.isBusy}
                />
            )}
        </div>
@@ -42,6 +42,7 @@ import { useValidateDiagram } from "@/hooks/use-validate-diagram"
 import { getApiEndpoint } from "@/lib/base-path"
 import { findCachedResponse } from "@/lib/cached-responses"
 import { buildChatHeaders } from "@/lib/chat-request"
+import { pageModelXml, placeOnPage } from "@/lib/diagram-pages"
 import { EMPTY_DRAWIO_DOCUMENT } from "@/lib/drawio/drawio-config"
 import { formatMessage } from "@/lib/i18n/utils"
 import { isPdfFile, isTextFile } from "@/lib/pdf-utils"
@@ -90,15 +91,20 @@ function hasToolErrors(messages: UIMessage[]): boolean {
 }

 /**
- * Snapshots keep the full multi-page document, but the model only sees and
- * edits the first page, so give it the first page's mxGraphModel.
- * Older snapshots already hold a single mxGraphModel and are returned as is.
+ * Snapshots keep the full multi-page document, but the model sees and
+ * edits one page, the one the user is viewing (the first when unknown), so
+ * give it that page's mxGraphModel. Older snapshots already hold a single
+ * mxGraphModel and are returned as is.
 */
-function getFirstPageXml(xml: string): string {
+function getPageXml(xml: string, pageId: string | null): string {
    if (!xml.includes("<mxfile")) return xml
-    const doc = new DOMParser().parseFromString(xml, "text/xml")
-    const model = doc.querySelector("diagram")?.querySelector("mxGraphModel")
-    return model ? formatXML(new XMLSerializer().serializeToString(model)) : xml
+    const model = pageModelXml(xml, pageId)
+    return model ? formatXML(model) : xml
+}
+
+/** The page the user is viewing; null with an external draw.io */
+function viewedPageId(): string | null {
+    return useCanvasStore.getState().currentPageId
 }

 // Shapes sent with a user message (also kept in its metadata)
@@ -374,6 +380,9 @@ export function ChatEngineProvider({

    // XML snapshot taken before each user message (keyed by message index)
    const xmlSnapshotsRef = useRef<Map<number, string>>(new Map())
+    // The page the running turn's model reads and writes: the one the user
+    // viewed when the message was sent (null: the first page)
+    const turnPageIdRef = useRef<string | null>(null)
    // Index of the user message whose turn is running (versions belong to it)
    const currentTurnRef = useRef(0)
    // The chat (its generation) the running turn was sent in: a reply that
@@ -450,6 +459,7 @@ export function ChatEngineProvider({
        validationRetryCountRef,
        // A preview undone just before the tool call is in this one already
        chartXMLRef: liveChartXMLRef,
+        turnPageIdRef,
        onDisplayChart,
        onFetchChart,
        captureValidationPng,
@@ -748,6 +758,7 @@ export function ChatEngineProvider({
        processedToolCallsRef,
        editDiagramOriginalXmlRef,
        loadedMessageIdsRef,
+        turnPageIdRef,
    })

    const { restoreVersion, undoVersion } = useVersions({
@@ -762,14 +773,10 @@ export function ChatEngineProvider({
    // ---------------------------------------------------------------------

    const selection = useCanvasStore((s) => s.selection)
-    // The model sees and edits the first page only
-    const onFirstPage = useCanvasStore(
-        (s) => s.pages.length === 0 || s.pages[0]?.id === s.currentPageId,
-    )
    const [dismissedSelectionKey, setDismissedSelectionKey] = useState("")
    const selectionKey = selection.map((c) => c.id).join(",")
    const chatSelection =
-        !onFirstPage || selectionKey === dismissedSelectionKey ? [] : selection
+        selectionKey === dismissedSelectionKey ? [] : selection
    // Once nothing is selected, picking the same shapes again attaches them
    useEffect(() => {
        if (selection.length === 0) setDismissedSelectionKey("")
@@ -1178,8 +1185,9 @@ export function ChatEngineProvider({
            .filter((k) => k < beforeIndex)
            .sort((a, b) => b - a)
        return snapshotKeys.length > 0
-            ? getFirstPageXml(
+            ? getPageXml(
                  xmlSnapshotsRef.current.get(snapshotKeys[0]) || "",
+                  viewedPageId(),
              )
            : ""
    }
@@ -1198,6 +1206,7 @@ export function ChatEngineProvider({
        continuationOriginalRef.current = null
        stoppedRef.current = false
        currentTurnRef.current = turnIndex
+        turnPageIdRef.current = viewedPageId()
        turnChatRef.current = getChatGeneration()
        // Busy from now on, before the next render says so
        busyRef.current = true
@@ -1254,7 +1263,8 @@ export function ChatEngineProvider({
        const turnIndex = messagesRef.current.length
        const previousXml = getPreviousXml(turnIndex)
        // Snapshot the full multi-page document (kept fresh by autosave) so
-        // regenerate/edit can restore every page; the model gets page 1 only
+        // regenerate/edit can restore every page; the model gets the page
+        // the user is viewing
        xmlSnapshotsRef.current.set(turnIndex, chartXMLRef.current || chartXml)
        sendChatMessage(parts, chartXml, previousXml, turnIndex, selectedCells)
        return true
@@ -1328,11 +1338,16 @@ export function ChatEngineProvider({
                    pageName: "Page-1",
                })
                if (prepared.ok) {
+                    const pageId = viewedPageId()
+                    const canvasXml = chartXMLRef.current || ""
                    onDisplayChart(
-                        keepFileVars(prepared.xml, chartXMLRef.current || ""),
+                        keepFileVars(
+                            placeOnPage(prepared.xml, canvasXml, pageId),
+                            canvasXml,
+                        ),
                        true,
                        "commit",
-                        { toolCallId },
+                        { toolCallId, pageId },
                    )
                }
                clearComposer()
@@ -1492,7 +1507,7 @@ export function ChatEngineProvider({
        })
        sendChatMessage(
            parts,
-            getFirstPageXml(savedXml),
+            getPageXml(savedXml, viewedPageId()),
            previousXml,
            index,
            selectionOf(messages[index]),
@@ -56,11 +56,11 @@ export function CompareDialog() {
        () => !version || isSameDocument(version.xml, chartXML),
        [version, chartXML],
    )
-    // What the canvas has changed since this version on the first page
-    // (null: nothing there)
+    // What the canvas has changed since this version on the page it was
+    // made on (null: nothing there)
    const changes = useMemo(() => {
        if (!version || same) return null
-        const { summary } = diffDiagrams(version.xml, chartXML)
+        const { summary } = diffDiagrams(version.xml, chartXML, version.pageId)
        return Object.values(summary).some((n) => n > 0) ? summary : null
    }, [version, chartXML, same])

@@ -5,13 +5,25 @@ import type { RefObject } from "react"
 import { useCallback, useEffect, useRef } from "react"
 import type { DiagramOperation, ToolPartLike } from "@/components/chat/types"
 import { useDiagram } from "@/contexts/diagram-context"
+import { pageSelectorFor } from "@/lib/diagram-pages"
 import {
    convertToLegalXml,
    extractCompleteMxCells,
    replaceNodes,
 } from "@/lib/utils"
+import {
+    defaultLayerOf,
+    expandCompactCells,
+} from "@/packages/mcp-server/src/compact-cells.ts"
 import { applyDiagramOperations } from "@/packages/mcp-server/src/diagram-operations.ts"
+import { targetPageXml } from "@/packages/mcp-server/src/edit-diagram.ts"
 import { BLANK_MXFILE } from "@/packages/mcp-server/src/pages.ts"
+import {
+    addDefaultStyles,
+    applyStyleClasses,
+    edgeIdsOf,
+    readStyleClasses,
+} from "@/packages/mcp-server/src/style-classes.ts"

 // Helper to extract complete operations from streaming input
 function getCompleteOperations(
@@ -34,6 +46,8 @@ interface UseDiagramStreamingParams {
    processedToolCallsRef: RefObject<Set<string>>
    editDiagramOriginalXmlRef: RefObject<Map<string, string>>
    loadedMessageIdsRef: RefObject<Set<string>>
+    // The page the model draws on in this turn; null: the first page
+    turnPageIdRef?: RefObject<string | null>
 }

 /**
@@ -50,6 +64,7 @@ export function useDiagramStreaming({
    processedToolCallsRef,
    editDiagramOriginalXmlRef,
    loadedMessageIdsRef,
+    turnPageIdRef,
 }: UseDiagramStreamingParams) {
    const { chartXML, chartXMLRef, loadDiagram } = useDiagram()
    const previousXML = useRef<string>("")
@@ -71,9 +86,17 @@ export function useDiagramStreaming({
    // so far. The tool handler validates and loads the final diagram.
    const handleDisplayChart = useCallback(
        (xml: string) => {
-            const completeCells = extractCompleteMxCells(xml || "")
+            // Named styles come before the cells, so the ones written so
+            // far are known by the time their cells stream in
+            const { classes, xml: cellsXml } = readStyleClasses(xml || "")
+            const completeCells = extractCompleteMxCells(cellsXml)
            if (!completeCells) return
-            const convertedXml = convertToLegalXml(completeCells)
+            const convertedXml = addDefaultStyles(
+                applyStyleClasses(
+                    expandCompactCells(convertToLegalXml(completeCells)),
+                    classes,
+                ),
+            )
            if (convertedXml === previousXML.current) return

            // Skip this update while the cells written so far don't parse
@@ -84,10 +107,15 @@ export function useDiagramStreaming({
            if (testDoc.querySelector("parsererror")) return

            try {
-                // Replace the first page's cells so other pages stay intact.
-                // An empty canvas gets a default mxfile to put the cells in.
+                // Replace the model's page's cells so other pages stay
+                // intact. An empty canvas gets a default mxfile to put the
+                // cells in.
                const baseXML = chartXML || BLANK_MXFILE
-                const replacedXML = replaceNodes(baseXML, convertedXml)
+                const replacedXML = replaceNodes(
+                    baseXML,
+                    convertedXml,
+                    turnPageIdRef?.current,
+                )
                previousXML.current = convertedXml
                loadDiagram(replacedXML, true, "preview")
            } catch (error) {
@@ -202,9 +230,29 @@ export function useDiagramStreaming({
            if (lastProcessedXmlRef.current.get(opsKey) === ops) continue
            lastProcessedXmlRef.current.set(opsKey, ops)
            try {
+                // The model's page: the edges on it and its first layer,
+                // as editDiagram reads them
+                const selector = pageSelectorFor(
+                    originalXml,
+                    turnPageIdRef?.current,
+                )
+                const page = targetPageXml(originalXml, selector)
+                const edges = edgeIdsOf(page)
+                const layer = defaultLayerOf(page)
                const { result } = applyDiagramOperations(
                    originalXml,
-                    completeOps,
+                    completeOps.map((op) =>
+                        op.new_xml
+                            ? {
+                                  ...op,
+                                  new_xml: addDefaultStyles(
+                                      expandCompactCells(op.new_xml, layer),
+                                      edges,
+                                  ),
+                              }
+                            : op,
+                    ),
+                    selector,
                )
                if (lastProcessedXmlRef.current.get(resultKey) === result) {
                    continue
@@ -46,15 +46,17 @@ export function useVersions({
    // (effect cleanups run before the streaming hook commits). The handler
    // only reads refs and stable functions.
    useEffect(() => {
-        setCommitHandler(({ beforeXml, afterXml, toolCallId }) => {
+        setCommitHandler(({ beforeXml, afterXml, toolCallId, pageId }) => {
            if (restoringRef.current) return
            const { summary, touchedIds, fromScratch } = diffDiagrams(
                beforeXml,
                afterXml,
+                pageId,
            )
            const id = useVersionsStore.getState().addVersion({
                xml: afterXml,
                beforeXml,
+                ...(pageId && { pageId }),
                turnIndex: currentTurnRef.current,
                toolCallId,
                summary,
@@ -23,12 +23,14 @@ import {
    previewDiagram,
    resetPreview,
    revertPreview,
+    selectPage,
 } from "@/lib/drawio/editor-bridge"
 import {
    BLANK_MXFILE,
    normalizeToMxfile,
 } from "@/packages/mcp-server/src/pages.ts"
 import { validateAndFixXml } from "@/packages/mcp-server/src/xml-validation.ts"
+import { useCanvasStore } from "@/stores/canvas-store"
 import { extractDiagramXML, isRealDiagram } from "../lib/utils"

 /**
@@ -54,6 +56,8 @@ export interface DiagramCommit {
    beforeXml: string
    afterXml: string
    toolCallId?: string
+    /** The page the change was made on; null or absent: the first page */
+    pageId?: string | null
 }

 interface DiagramContextType {
@@ -65,12 +69,12 @@ interface DiagramContextType {
        chart: string,
        skipValidation?: boolean,
        mode?: LoadMode,
-        meta?: { toolCallId?: string },
+        meta?: { toolCallId?: string; pageId?: string | null },
    ) => string | null
    // Returns the export's tag (empty when draw.io is not there yet)
    handleExport: () => string
-    // Pending exports by tag; a plain export's resolver gets the first
-    // page's XML
+    // Pending exports by tag; a plain export's resolver gets the XML of the
+    // page on screen
    exportResolversRef: React.MutableRefObject<
        Record<string, (data: string, xml?: string) => void>
    >
@@ -134,17 +138,28 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
        null,
    )

+    // The page to show again once a full load is done: draw.io shows the
+    // first page of a loaded document
+    const pageAfterLoadRef = useRef<string | null>(null)
+
    // Sends a full load. draw.io runs it when its message arrives, and then
    // reports "load": until then the editor shows the diagram from before,
    // so later changes go the same way and keep their order
    const fullLoad = (xml: string) => {
        if (!drawioRef.current) return
+        const pageId = useCanvasStore.getState().currentPageId
+        pageAfterLoadRef.current =
+            pageId && xml.includes(`id="${pageId}"`) ? pageId : null
        pendingLoadsRef.current++
        drawioRef.current.load({ xml })
    }

    const onDrawioLoad = () => {
        pendingLoadsRef.current = Math.max(0, pendingLoadsRef.current - 1)
+        // Back to the page the user was on
+        const pageId = pageAfterLoadRef.current
+        pageAfterLoadRef.current = null
+        if (pageId) selectPage(pageId)
        // Only set ready state once to prevent infinite loops
        if (hasCalledOnLoadRef.current) return
        hasCalledOnLoadRef.current = true
@@ -241,7 +256,7 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
        chart: string,
        skipValidation?: boolean,
        mode: LoadMode = "load",
-        meta?: { toolCallId?: string },
+        meta?: { toolCallId?: string; pageId?: string | null },
    ): string | null => {
        // The editor bridge is shared: a page that is gone (another language
        // mounted a new one) must not change the new page's canvas
@@ -308,6 +323,7 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
                beforeXml,
                afterXml: xmlToLoad,
                toolCallId: meta?.toolCallId,
+                pageId: meta?.pageId,
            })
        }

@@ -332,7 +348,12 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
        // data.xml from xmlsvg exports has compressed <diagram> payloads that
        // would break edit_diagram/display_diagram. Autosave keeps chartXML
        // up to date with the full uncompressed multi-page document (#879).
-        const extractedXML = extractDiagramXML(data.data)
+        // The chat gets the page the user is viewing (the first one with
+        // an external draw.io, which cannot tell us)
+        const extractedXML = extractDiagramXML(
+            data.data,
+            useCanvasStore.getState().currentPageId,
+        )
        setLatestSvg(data.data)

        // The chat's own export (onFetchChart), not another one in flight
@@ -1,7 +1,6 @@
 appId: com.nextaidrawio.app
 productName: Next AI Draw.io
 copyright: Copyright © 2024 Next AI Draw.io
-electronVersion: 39.2.7

 directories:
  output: release
@@ -5,15 +5,19 @@ import type {
    ValidationStatus,
 } from "@/components/chat/ValidationCard"
 import type { LoadMode } from "@/contexts/diagram-context"
+import { pageModelXml, pageSelectorFor, placeOnPage } from "@/lib/diagram-pages"
 import type { ValidationResult } from "@/lib/diagram-validator"
 import { formatValidationFeedback } from "@/lib/diagram-validator"
 import { isMxCellXmlComplete } from "@/lib/utils"
+import { foldCells } from "@/packages/mcp-server/src/compact-cells.ts"
 import { editDiagram } from "@/packages/mcp-server/src/edit-diagram.ts"
 import { prepareNewDiagram } from "@/packages/mcp-server/src/new-diagram.ts"
+import { hasCells } from "@/packages/mcp-server/src/pages.ts"

 const DEBUG = process.env.NODE_ENV === "development"

-// display_diagram replaces the document with this one page
+// The page a drawing is wrapped in; on the canvas it replaces the page the
+// model works on, so the canvas page keeps its own id and name
 const NEW_PAGE = { pageId: "page-1", pageName: "Page-1" }

 /**
@@ -81,11 +85,14 @@ interface UseDiagramToolHandlersParams {
    // Failed VLM validations in the current user turn (reset on each user message)
    validationRetryCountRef: RefObject<number>
    chartXMLRef: RefObject<string>
+    // The page the model reads and writes in this turn (the one the user
+    // viewed when it began); null, or absent, means the first page
+    turnPageIdRef?: RefObject<string | null>
    onDisplayChart: (
        xml: string,
        skipValidation?: boolean,
        mode?: LoadMode,
-        meta?: { toolCallId?: string },
+        meta?: { toolCallId?: string; pageId?: string | null },
    ) => string | null
    onFetchChart: () => Promise<string>
    captureValidationPng?: () => Promise<string | null>
@@ -117,6 +124,7 @@ export function useDiagramToolHandlers({
    processedToolCallsRef,
    validationRetryCountRef,
    chartXMLRef,
+    turnPageIdRef,
    onDisplayChart,
    onFetchChart,
    captureValidationPng,
@@ -180,11 +188,29 @@ export function useDiagramToolHandlers({
    const commit = (xml: string, toolCallId: string) => {
        const original = continuationOriginalRef.current
        if (original !== null) onDisplayChart(original, true, "revert")
-        const error = onDisplayChart(xml, true, "commit", { toolCallId })
+        const error = onDisplayChart(xml, true, "commit", {
+            toolCallId,
+            pageId: aiPageId(),
+        })
        if (!error) continuationOriginalRef.current = null
        return error
    }

+    const aiPageId = () => turnPageIdRef?.current ?? null
+
+    // The diagram as the model sees it in the chat request: its page only
+    const shownToModel = (xml: string) =>
+        foldCells(pageModelXml(xml, aiPageId()) ?? xml)
+
+    // A drawn page goes onto the model's page of the canvas file, which
+    // keeps its other pages; a drawing that brings several pages replaces
+    // the file, and gets its variables
+    const onAiPage = (drawnXml: string) =>
+        keepFileVars(
+            placeOnPage(drawnXml, chartXMLRef.current, aiPageId()),
+            chartXMLRef.current,
+        )
+
    const takeOriginals = (): string | undefined => {
        const [originalXml] = editDiagramOriginalXmlRef.current.values()
        for (const id of editDiagramOriginalXmlRef.current.keys()) {
@@ -263,10 +289,7 @@ NEXT STEP: Call append_diagram with the continuation XML.
        // finds the diagram already in place
        const prepared = prepareNewDiagram(finalXml, NEW_PAGE)
        const validationError = prepared.ok
-            ? commit(
-                  keepFileVars(prepared.xml, chartXMLRef.current),
-                  toolCall.toolCallId,
-              )
+            ? commit(onAiPage(prepared.xml), toolCall.toolCallId)
            : prepared.error

        if (validationError) {
@@ -501,8 +524,12 @@ ${finalXml}
            }

            // All or nothing, checked like the MCP server's edit_diagram.
-            // The model sees the first page, so edits target it.
-            const outcome = editDiagram(currentXml, operations, {})
+            // The model sees its page, so edits target it.
+            const outcome = editDiagram(
+                currentXml,
+                operations,
+                pageSelectorFor(currentXml, aiPageId()),
+            )
            if (!outcome.ok) {
                const reason = outcome.pageError
                    ? outcome.errors[0]
@@ -516,7 +543,7 @@ ${finalXml}

 Current diagram XML:
 \`\`\`xml
-${currentXml}
+${shownToModel(currentXml)}
 \`\`\`

 Please check the cell IDs and retry.`,
@@ -545,7 +572,7 @@ Please check the cell IDs and retry.`,

 Current diagram XML:
 \`\`\`xml
-${currentXml || "No XML available"}
+${currentXml ? shownToModel(currentXml) : "No XML available"}
 \`\`\`

 Please check cell IDs and retry, or use display_diagram to regenerate.`,
@@ -575,7 +602,10 @@ Use display_diagram to create the complete diagram, or edit_diagram to change th
        // 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()
+        // Definitions at the start are a restart only once cells were written
        const isFreshStart =
+            (trimmed.startsWith("<mxStyle") &&
+                hasCells(partialXmlRef.current)) ||
            trimmed.startsWith("<mxGraphModel") ||
            trimmed.startsWith("<root") ||
            trimmed.startsWith("<mxfile") ||
@@ -615,10 +645,7 @@ Start your continuation with the NEXT character after where it stopped.`,
            // originals, so the preview code undoes none of them later
            const originalXml = takeOriginals()
            const validationError = prepared.ok
-                ? commit(
-                      keepFileVars(prepared.xml, chartXMLRef.current),
-                      toolCall.toolCallId,
-                  )
+                ? commit(onAiPage(prepared.xml), toolCall.toolCallId)
                : prepared.error

            if (validationError) {
@@ -1,6 +1,6 @@
-import { decompressPageContent } from "@/packages/mcp-server/src/load-diagram.ts"
+import { modelOfPage, pageElement } from "@/lib/diagram-pages"

-/** What changed on the first page between two versions of a diagram */
+/** What changed on one page between two versions of a diagram */
 export interface ChangeSummary {
    shapesAdded: number
    shapesRemoved: number
@@ -32,27 +32,20 @@ interface CellInfo {
    signature: string
 }

-/** A page's mxGraphModel element, inflated when the page is compressed */
-function modelOfPage(diagram: Element): Element | null {
-    const model = diagram.querySelector("mxGraphModel")
-    if (model) return model
-    const inflated = decompressPageContent(diagram.textContent || "")
-    if (!inflated) return null
-    const inner = new DOMParser().parseFromString(inflated, "text/xml")
-    return inner.querySelector("mxGraphModel")
-}
-
 function parse(xml: string): Document | null {
    if (!xml?.trim()) return null
    const doc = new DOMParser().parseFromString(xml, "text/xml")
    return doc.querySelector("parsererror") ? null : doc
 }

-/** The first page's mxGraphModel element, whatever wrapper the XML has */
-function firstPageModel(xml: string): Element | null {
+/**
+ * A page's mxGraphModel element, whatever wrapper the XML has: the page
+ * with this id, else the first
+ */
+function pageModel(xml: string, pageId?: string | null): Element | null {
    const doc = parse(xml)
    if (!doc) return null
-    const diagram = doc.querySelector("diagram")
+    const diagram = pageElement(doc, pageId)
    if (diagram) return modelOfPage(diagram)
    return doc.querySelector("mxGraphModel") ?? doc.documentElement
 }
@@ -133,10 +126,13 @@ function cellsIn(model: Element | null) {
    })
 }

-/** Shapes and connectors of the first page (not the root and its layers) */
-function collectCells(xml: string): Map<string, CellInfo> {
+/** Shapes and connectors of one page (not the root and its layers) */
+function collectCells(
+    xml: string,
+    pageId?: string | null,
+): Map<string, CellInfo> {
    const cells = new Map<string, CellInfo>()
-    for (const { id, cell, node } of cellsIn(firstPageModel(xml))) {
+    for (const { id, cell, node } of cellsIn(pageModel(xml, pageId))) {
        if (id === "0" || cell.getAttribute("parent") === "0") continue
        cells.set(id, {
            isEdge: cell.getAttribute("edge") === "1",
@@ -146,9 +142,14 @@ function collectCells(xml: string): Map<string, CellInfo> {
    return cells
 }

-export function diffDiagrams(beforeXml: string, afterXml: string): DiagramDiff {
-    const before = collectCells(beforeXml)
-    const after = collectCells(afterXml)
+/** What changed on one page (the first when no id is given) */
+export function diffDiagrams(
+    beforeXml: string,
+    afterXml: string,
+    pageId?: string | null,
+): DiagramDiff {
+    const before = collectCells(beforeXml, pageId)
+    const after = collectCells(afterXml, pageId)
    const summary: ChangeSummary = { ...EMPTY_SUMMARY }
    const touchedIds: string[] = []

@@ -0,0 +1,138 @@
+/**
+ * The page the AI works on is the page the user is viewing. These helpers
+ * read that page out of a multi-page document and write a drawing into it
+ * while the other pages stay as they are. A page id that matches no page
+ * (or none at all, as with an external draw.io that cannot tell us) means
+ * the first page, which is what the app always used before.
+ */
+
+import { decompressPageContent } from "@/packages/mcp-server/src/load-diagram.ts"
+import {
+    BLANK_MXFILE,
+    type PageSelector,
+} from "@/packages/mcp-server/src/pages.ts"
+
+function parse(xml: string): Document | null {
+    if (!xml?.trim()) return null
+    const doc = new DOMParser().parseFromString(xml, "text/xml")
+    return doc.querySelector("parsererror") ? null : doc
+}
+
+/** The <diagram> the AI works on: the one with this id, else the first */
+export function pageElement(
+    doc: Document,
+    pageId: string | null | undefined,
+): Element | null {
+    const diagrams = Array.from(doc.getElementsByTagName("diagram"))
+    if (diagrams.length === 0) return null
+    return (
+        (pageId &&
+            diagrams.find(
+                (diagram) => diagram.getAttribute("id") === pageId,
+            )) ||
+        diagrams[0]
+    )
+}
+
+/** A page's mxGraphModel element, inflated when the page is compressed */
+export function modelOfPage(diagram: Element): Element | null {
+    const model = diagram.querySelector("mxGraphModel")
+    if (model) return model
+    const inflated = decompressPageContent(diagram.textContent || "")
+    if (!inflated) return null
+    return parse(inflated)?.querySelector("mxGraphModel") ?? null
+}
+
+/**
+ * Selector for editDiagram and applyDiagramOperations: the page with this
+ * id when the document has it, else their default (the first page)
+ */
+export function pageSelectorFor(
+    xml: string,
+    pageId: string | null | undefined,
+): PageSelector {
+    if (!pageId) return {}
+    const doc = parse(xml)
+    const found = doc
+        ? Array.from(doc.getElementsByTagName("diagram")).some(
+              (diagram) => diagram.getAttribute("id") === pageId,
+          )
+        : false
+    return found ? { page_id: pageId } : {}
+}
+
+/**
+ * The page's mxGraphModel as XML. A bare mxGraphModel is returned as it
+ * is; null when the XML does not parse or has no model.
+ */
+export function pageModelXml(
+    xml: string,
+    pageId: string | null | undefined,
+): string | null {
+    const doc = parse(xml)
+    if (!doc) return null
+    const root = doc.documentElement
+    if (root.nodeName === "mxGraphModel") return xml
+    if (root.nodeName !== "mxfile") return null
+    const diagram = pageElement(doc, pageId)
+    const model = diagram ? modelOfPage(diagram) : null
+    return model ? new XMLSerializer().serializeToString(model) : null
+}
+
+/**
+ * The document with one page's content replaced by this model. The page
+ * keeps its id and name, the other pages and the file's attributes (its
+ * variables) stay. Without a document to put the page in, the blank
+ * one-page file is used.
+ */
+export function replacePageModel(
+    fileXml: string,
+    pageId: string | null | undefined,
+    modelXml: string,
+): string {
+    const model = parse(modelXml)
+    if (model?.documentElement.nodeName !== "mxGraphModel") {
+        throw new Error("replacePageModel needs an <mxGraphModel>")
+    }
+    let doc = parse(fileXml)
+    if (doc?.documentElement.nodeName !== "mxfile") doc = parse(BLANK_MXFILE)
+    let diagram = pageElement(doc as Document, pageId)
+    if (!diagram) {
+        doc = parse(BLANK_MXFILE)
+        diagram = pageElement(doc as Document, null)
+    }
+    const target = diagram as Element
+    while (target.firstChild) target.removeChild(target.firstChild)
+    target.appendChild(
+        (doc as Document).importNode(model.documentElement, true),
+    )
+    return new XMLSerializer().serializeToString(doc as Document)
+}
+
+/**
+ * Where a drawn diagram goes. One page's worth (bare cells wrapped by
+ * prepareNewDiagram, or a one-page file) replaces the AI's page of the
+ * canvas file; file variables the drawn file sets replace the canvas
+ * file's. A file with several pages replaces the whole document: the model
+ * wrote the pages on purpose.
+ */
+export function placeOnPage(
+    drawnXml: string,
+    canvasXml: string,
+    pageId: string | null | undefined,
+): string {
+    const doc = parse(drawnXml)
+    const drawnFile =
+        doc?.documentElement.nodeName === "mxfile" ? doc.documentElement : null
+    if (drawnFile && drawnFile.getElementsByTagName("diagram").length > 1) {
+        return drawnXml
+    }
+    const model = pageModelXml(drawnXml, null)
+    if (!model) return drawnXml
+    const placed = replacePageModel(canvasXml, pageId, model)
+    const vars = drawnFile?.getAttribute("vars")
+    if (vars === null || vars === undefined) return placed
+    const result = parse(placed) as Document
+    result.documentElement.setAttribute("vars", vars)
+    return new XMLSerializer().serializeToString(result)
+}
@@ -9,7 +9,7 @@
 * With an external draw.io (cross-origin) none of this is available and the
 * app uses the postMessage protocol only.
 */
-import { sameFileVars } from "@/lib/diagram-diff"
+import { isSameDocument, sameFileVars } from "@/lib/diagram-diff"
 import { hasCells } from "@/packages/mcp-server/src/pages.ts"
 import { type SelectedCell, useCanvasStore } from "@/stores/canvas-store"

@@ -152,23 +152,18 @@ function withoutUndo(fn: () => void) {
    }
 }

-/**
- * replaceDiagramData replaces the current page with one <mxGraphModel>. Only
- * single-page documents qualify; multi-page ones fall back to a full load.
- */
-function toSinglePageModel(xml: string): string | null {
-    const doc = new DOMParser().parseFromString(xml, "text/xml")
-    if (doc.querySelector("parsererror")) return null
-    const root = doc.documentElement
-    if (root.nodeName === "mxGraphModel") return xml
-    if (root.nodeName !== "mxfile") return null
-    const diagrams = root.getElementsByTagName("diagram")
-    if (diagrams.length !== 1) return null
-    const model = diagrams[0].getElementsByTagName("mxGraphModel")[0]
+/** Id of the page on the canvas, when draw.io has pages */
+function currentPageId(): string | null {
+    const id = ui?.currentPage?.getId?.()
+    return id === undefined || id === null ? null : String(id)
+}
+
+/** A page's <mxGraphModel> as XML, inflated when the page is compressed */
+function modelXmlOf(diagram: Element): string | null {
+    const model = diagram.getElementsByTagName("mxGraphModel")[0]
    if (model) return new XMLSerializer().serializeToString(model)
-    // Compressed page
    try {
-        const text = diagrams[0].textContent?.trim()
+        const text = diagram.textContent?.trim()
        const inflated = text ? win?.Graph?.decompress?.(text) : null
        return typeof inflated === "string" &&
            inflated.includes("<mxGraphModel")
@@ -179,8 +174,62 @@ function toSinglePageModel(xml: string): string | null {
    }
 }

+/**
+ * replaceDiagramData replaces the current page with one <mxGraphModel>:
+ * the document's page with the canvas page's id, or its only page
+ */
+function pageModelOf(xml: string): string | null {
+    const doc = new DOMParser().parseFromString(xml, "text/xml")
+    if (doc.querySelector("parsererror")) return null
+    const root = doc.documentElement
+    if (root.nodeName === "mxGraphModel") return xml
+    if (root.nodeName !== "mxfile") return null
+    const diagrams = Array.from(root.getElementsByTagName("diagram"))
+    const id = currentPageId()
+    const diagram =
+        diagrams.length === 1
+            ? diagrams[0]
+            : diagrams.find((d) => d.getAttribute("id") === id)
+    return diagram ? modelXmlOf(diagram) : null
+}
+
+/**
+ * The document without the current page, for comparing the other pages.
+ * null when the XML is not a document; "" for a single page.
+ */
+function withoutCurrentPage(xml: string | null): string | null {
+    if (!xml) return null
+    const doc = new DOMParser().parseFromString(xml, "text/xml")
+    if (doc.querySelector("parsererror")) return null
+    const root = doc.documentElement
+    if (root.nodeName === "mxGraphModel") return ""
+    if (root.nodeName !== "mxfile") return null
+    const diagrams = Array.from(root.getElementsByTagName("diagram"))
+    if (diagrams.length <= 1) return ""
+    const id = currentPageId()
+    for (const diagram of diagrams) {
+        if (diagram.getAttribute("id") === id) root.removeChild(diagram)
+    }
+    return new XMLSerializer().serializeToString(root)
+}
+
+/**
+ * The document changes the current page only: its other pages are the
+ * canvas's (same names, cells and page settings; draw.io fills in settings
+ * a loaded file left out, so the text can differ)
+ */
+function otherPagesSame(xml: string): boolean {
+    const theirs = withoutCurrentPage(xml)
+    if (theirs === null) return false
+    const pageCount = Array.isArray(ui.pages) ? ui.pages.length : 1
+    if (pageCount <= 1 && theirs === "") return true
+    const ours = withoutCurrentPage(currentFileXml())
+    if (ours === null || ours === "" || theirs === "") return false
+    return isSameDocument(theirs, ours)
+}
+
 function replace(xml: string) {
-    const model = toSinglePageModel(xml)
+    const model = pageModelOf(xml)
    if (!model || typeof ui?.replaceDiagramData !== "function") {
        throw new Error("Diagram can't be replaced in place")
    }
@@ -202,7 +251,7 @@ function isEmptyModel(): boolean {

 /** Whether a page has shapes; layers (cells under the root) are none */
 function hasShapes(xml: string): boolean {
-    const model = toSinglePageModel(xml)
+    const model = pageModelOf(xml)
    if (model === null) return hasCells(xml)
    const cells = new DOMParser()
        .parseFromString(model, "text/xml")
@@ -256,8 +305,9 @@ export function canReplaceDiagram(xml: string): boolean {
        warnOnce("replace", "replaceDiagramData not found, using full loads")
        return false
    }
-    const pageCount = Array.isArray(ui.pages) ? ui.pages.length : 1
-    if (pageCount > 1) return false
+    // Replacing changes the current page only: a document whose other
+    // pages differ from the canvas's loads in full
+    if (!otherPagesSame(xml)) return false
    // Replacing the page keeps the file's variables: other ones, or none
    // over a file with some, load in full
    if (
@@ -268,7 +318,7 @@ export function canReplaceDiagram(xml: string): boolean {
    ) {
        return false
    }
-    const model = toSinglePageModel(xml)
+    const model = pageModelOf(xml)
    // A document with them, or replacing one with them, loads in full
    return (
        model !== null &&
@@ -285,13 +335,21 @@ export function previewDiagram(xml: string) {
    if (wasEmpty) fitDiagram()
 }

-/** Name and id of the page in a single-page mxfile, if it has them */
+/**
+ * Name and id the document gives the canvas page: of its page with that
+ * id, or of its only page
+ */
 function pageOf(xml: string): { name: string | null; id: string | null } {
    const doc = new DOMParser().parseFromString(xml, "text/xml")
-    const diagram =
+    const diagrams =
        doc.documentElement?.nodeName === "mxfile"
-            ? doc.getElementsByTagName("diagram")[0]
-            : undefined
+            ? Array.from(doc.getElementsByTagName("diagram"))
+            : []
+    const id = currentPageId()
+    const diagram =
+        diagrams.length === 1
+            ? diagrams[0]
+            : diagrams.find((d) => d.getAttribute("id") === id)
    return {
        name: diagram?.getAttribute("name") || null,
        id: diagram?.getAttribute("id") || null,
@@ -322,7 +380,7 @@ function changePageId(page: any, id: string) {
 export function commitDiagram(xml: string) {
    const wasEmpty =
        isEmptyModel() || (previewBase !== null && !hasShapes(previewBase))
-    const base = previewBase ? toSinglePageModel(previewBase) : null
+    const base = previewBase ? pageModelOf(previewBase) : null
    previewBase = null
    // Undo goes back to the diagram before streaming started. draw.io's
    // ReplaceDiagram change keeps the document it replaced for undo: hand it
@@ -337,7 +395,7 @@ export function commitDiagram(xml: string) {
    const page = ui?.currentPage
    model?.beginUpdate()
    try {
-        const next = toSinglePageModel(xml)
+        const next = pageModelOf(xml)
        if (direct && next) {
            const change = new ReplaceDiagram(ui, parse(next))
            model.execute(change)
@@ -368,6 +426,18 @@ export function resetPreview() {
    previewBase = null
 }

+/** Show the page with this id; false when draw.io has no such page */
+export function selectPage(pageId: string): boolean {
+    try {
+        const page = ui?.getPageById?.(pageId)
+        if (!page || typeof ui.selectPage !== "function") return false
+        if (ui.currentPage !== page) ui.selectPage(page, true)
+        return true
+    } catch {
+        return false
+    }
+}
+
 // When the app last fitted the diagram on its own; a canvas resize right
 // after (the chat panel sliding in) fits again, unless the user zoomed since
 let lastAutoFitAt = 0
@@ -4,6 +4,7 @@
 */

 import {
+    STYLE_CLASS_EXAMPLE,
    SWIMLANE_EXAMPLE,
    TWO_EDGES_EXAMPLE,
    WAYPOINT_EXAMPLE,
@@ -100,45 +101,41 @@ Note that:

 When using edit_diagram tool:
 - 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 update/add: provide cell_id and the complete new_xml in the same compact form (a shape with x, y, w, h; an edge with source and target)
 - For delete: only cell_id is needed
+- Named styles are not available in edit_diagram: write each cell's complete style
 - Find the cell_id from "Current diagram XML" in system context
- Example update: {"operations": [{"operation": "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 update: {"operations": [{"operation": "update", "cell_id": "3", "new_xml": "<mxCell id=\\"3\\" value=\\"New Label\\" style=\\"rounded=1;\\" x=\\"100\\" y=\\"100\\" w=\\"120\\" h=\\"60\\"/>"}]}
 - Example delete: {"operations": [{"operation": "delete", "cell_id": "5"}]}
- Example add: {"operations": [{"operation": "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>"}]}
+- Example add: {"operations": [{"operation": "add", "cell_id": "new1", "new_xml": "<mxCell id=\\"new1\\" value=\\"New Box\\" style=\\"rounded=1;\\" x=\\"400\\" y=\\"200\\" w=\\"120\\" h=\\"60\\"/>"}]}

 ⚠️ JSON ESCAPING: Every " inside new_xml MUST be escaped as \\". Example: id=\\"5\\" value=\\"Label\\"

 ## Draw.io XML Structure Reference

-**IMPORTANT:** You only generate the mxCell elements. The wrapper structure and root cells (id="0", id="1") are added automatically.
+**IMPORTANT:** You only generate the named styles and the mxCell elements. The wrapper structure and root cells (id="0", id="1") are added automatically. A named style is written before the cells as <mxStyle name="n" value="...style pairs..."/>; a cell uses it by putting the name among its style tokens (see Styles). A shape is one self-closing mxCell with x, y, w and h; an edge is one with source and target (a cell with source or target is always an edge). vertex="1", edge="1", parent="1" and the mxGeometry element are added automatically. Write parent only for a shape inside a container, and an mxGeometry element only for edge waypoints or for a separate label cell placed on an edge: <mxCell id="9" value="yes" style="edgeLabel;" parent="<edge id>" connectable="0"><mxGeometry x="-0.5" relative="1" as="geometry"/></mxCell>. An edge's own text simply goes in its value.

 Example - generate ONLY this:
 \`\`\`xml
-<mxCell id="2" value="Label" style="rounded=1;" vertex="1" parent="1">
-  <mxGeometry x="100" y="100" width="120" height="60" as="geometry"/>
-</mxCell>
+<mxCell id="2" value="Label" style="rounded=1;" x="100" y="100" w="120" h="60"/>
 \`\`\`

 CRITICAL RULES:
-1. Generate ONLY mxCell elements - NO wrapper tags (<mxfile>, <mxGraphModel>, <root>)
+1. Generate ONLY mxStyle definitions and 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
+5. Write parent="<container-id>" only for shapes inside a container; top-level cells need no parent

 Shape (vertex) example:
 \`\`\`xml
-<mxCell id="2" value="Label" style="rounded=1;whiteSpace=wrap;html=1;" vertex="1" parent="1">
-  <mxGeometry x="100" y="100" width="120" height="60" as="geometry"/>
-</mxCell>
+<mxCell id="2" value="Label" style="rounded=1;" x="100" y="100" w="120" h="60"/>
 \`\`\`

 Connector (edge) example:
 \`\`\`xml
-<mxCell id="3" style="endArrow=classic;html=1;" edge="1" parent="1" source="2" target="4">
-  <mxGeometry relative="1" as="geometry"/>
-</mxCell>
+<mxCell id="3" style="edgeStyle=orthogonalEdgeStyle;" source="2" target="4"/>
+\`\`\`

 ### Edge Routing Rules:
 When creating edges/connectors, you MUST follow these rules to avoid overlapping lines:
@@ -153,7 +150,7 @@ When creating edges/connectors, you MUST follow these rules to avoid overlapping

 **Rule 3: Always specify exitX, exitY, entryX, entryY explicitly**
 - Every edge MUST have these 4 attributes set in the style
- Example: style="edgeStyle=orthogonalEdgeStyle;exitX=1;exitY=0.3;entryX=0;entryY=0.3;endArrow=classic;"
+- Example: style="edgeStyle=orthogonalEdgeStyle;exitX=1;exitY=0.3;entryX=0;entryY=0.3;"

 **Rule 4: Route edges AROUND intermediate shapes (obstacle avoidance) - CRITICAL!**
 - Before creating an edge, identify ALL shapes positioned between source and target
@@ -188,17 +185,18 @@ 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
+## Styles
+Define each style used by several cells ONCE, as a named style before the cells, and use the name in the cells like a CSS class. A cell's style can combine a shape token, a name and overrides; later pairs win. Name only styles that two or more cells share; a style used by one cell stays inline. Names must not be draw.io's own style names: shapes such as text, ellipse, rhombus, swimlane, label, image, and colors such as blue, green, red, gray, yellow, orange, purple, pink. A definition applies to the call it is in: each display_diagram call defines the names it uses. The app expands the names, so the saved file is standard draw.io XML.
+\`\`\`xml
+${STYLE_CLASS_EXAMPLE}
+\`\`\`
+- NEVER write html=1 or whiteSpace=wrap: the app adds html=1 to every cell and whiteSpace=wrap to shapes. Labels are HTML: use &lt;br&gt; for a line break and &lt;b&gt; for bold, never \\n; a literal < or > in a label is written &amp;lt; or &amp;gt;.
+- Do NOT repeat what draw.io already uses. For a plain shape: rounded=0, align=center, verticalAlign=middle, fontSize=12, strokeWidth=1, fillColor=#ffffff, strokeColor=#000000, fontColor=#000000. For an edge: endArrow=classic, strokeColor=#000000. Writing one of them is right only when it overrides what a name or the shape sets: an edge is rounded by default, so rounded=0 on an edge is a real setting, and a text cell is left/top aligned by default, so there align=center or verticalAlign=middle are real settings.
+- Keys: shapes rounded=1, fillColor=#hex, strokeColor=#hex; edges endArrow=block/open/none, startArrow=classic, curved=1, dashed=1, edgeStyle=orthogonalEdgeStyle; text fontSize=14, fontStyle=1 (bold), align=center/right.
 `

 // Minimal style instruction - skip styling and focus on layout (prepended to prompt for emphasis)
@@ -208,13 +206,13 @@ const MINIMAL_STYLE_INSTRUCTION = `
 ### 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
+- Shapes: no style, or only the shape (ellipse, rhombus). Edges: edgeStyle=orthogonalEdgeStyle plus the exit/entry points from the Edge Routing Rules, nothing else. html=1 and whiteSpace=wrap are added automatically.
 - 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
+- Example: style="fillColor=none;" for container rectangles

 ### Focus on Layout Quality
 Since we skip styling, STRICTLY follow the "Edge Routing Rules" section below:
@@ -235,10 +233,10 @@ const EXTENDED_ADDITIONS = `
 ### display_diagram Details

 **VALIDATION RULES** (XML will be rejected if violated):
-1. Generate ONLY mxCell elements - wrapper tags and root cells are added automatically
+1. Generate ONLY mxStyle definitions and 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)
+4. parent defaults to "1"; write it only for a shape inside a container (the container's id)
 5. Edge source/target attributes must reference existing cell IDs
 6. Escape special characters in values: &lt; for <, &gt; for >, &amp; for &, &quot; for "

@@ -257,7 +255,7 @@ ${SWIMLANE_EXAMPLE}
 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.
+**Example:** If previous output ended with \`<mxCell id="x" style="rounded=1\`, continue with \`;" x="40" y="40" w="120" h="60"/>\` and complete the remaining elements.

 ### edit_diagram Details

@@ -283,12 +281,12 @@ edit_diagram uses ID-based operations to modify cells directly by their id attri

 Change label:
 \`\`\`json
-{"operations": [{"operation": "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>"}]}
+{"operations": [{"operation": "update", "cell_id": "3", "new_xml": "<mxCell id=\\"3\\" value=\\"New Label\\" style=\\"rounded=1;\\" x=\\"100\\" y=\\"100\\" w=\\"120\\" h=\\"60\\"/>"}]}
 \`\`\`

 Add new shape:
 \`\`\`json
-{"operations": [{"operation": "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>"}]}
+{"operations": [{"operation": "add", "cell_id": "new1", "new_xml": "<mxCell id=\\"new1\\" value=\\"New Box\\" style=\\"rounded=1;fillColor=#dae8fc;\\" x=\\"400\\" y=\\"200\\" w=\\"120\\" h=\\"60\\"/>"}]}
 \`\`\`

 Delete container (children & edges auto-deleted):
@@ -312,7 +310,7 @@ ${TWO_EDGES_EXAMPLE}

 ### Edge with single waypoint (simple detour):
 \`\`\`xml
-<mxCell id="edge1" style="edgeStyle=orthogonalEdgeStyle;exitX=0.5;exitY=1;entryX=0.5;entryY=0;endArrow=classic;" edge="1" parent="1" source="a" target="b">
+<mxCell id="edge1" style="edgeStyle=orthogonalEdgeStyle;exitX=0.5;exitY=1;entryX=0.5;entryY=0;" edge="1" parent="1" source="a" target="b">
  <mxGeometry relative="1" as="geometry">
    <Array as="points">
      <mxPoint x="300" y="150"/>
@@ -2,6 +2,8 @@ import { type ClassValue, clsx } from "clsx"
 import * as pako from "pako"
 import { twMerge } from "tailwind-merge"
 import { hasCells } from "@/packages/mcp-server/src/pages.ts"
+import { readStyleClasses } from "@/packages/mcp-server/src/style-classes.ts"
+import { repairQuoteBeforeSlash } from "@/packages/mcp-server/src/xml-validation.ts"

 export function cn(...inputs: ClassValue[]) {
    return twMerge(clsx(inputs))
@@ -41,7 +43,12 @@ export function isRealDiagram(xml: string | undefined | null): boolean {
 * @returns true if XML appears complete, false if truncated or empty
 */
 export function isMxCellXmlComplete(xml: string | undefined | null): boolean {
-    const trimmed = xml?.trim() || ""
+    // Named style definitions before the cells are not cells: output cut off
+    // right after them is incomplete. A compact cell whose last quote is
+    // missing is complete; prepareNewDiagram repairs it.
+    const trimmed = repairQuoteBeforeSlash(
+        readStyleClasses(xml || "").xml,
+    ).trim()
    if (!trimmed) return false

    // Find position of last complete mxCell ending (either /> or </mxCell>)
@@ -89,7 +96,9 @@ export function extractCompleteMxCells(xml: string | undefined | null): string {
    // Match self-closing <mxCell ... /> or <mxCell ...>...</mxCell>, in document order.
    // The lazy [^>]*? tries "/>" first, so a self-closing cell never swallows
    // the following cells up to the next </mxCell>.
-    const cellPattern = /<mxCell\b[^>]*?(?:\/>|>[\s\S]*?<\/mxCell>)/g
+    // Quoted values may hold ">", so the tag ends at the first ">" outside them
+    const cellPattern =
+        /<mxCell\b(?:[^<>"']|"[^"]*"|'[^']*')*?(?:\/>|>[\s\S]*?<\/mxCell>)/g

    return (xml.match(cellPattern) || []).join("\n")
 }
@@ -152,7 +161,8 @@ export function formatXML(xml: string, indent: string = "  "): string {
 export function convertToLegalXml(xmlString: string): string {
    // This regex will match either self-closing <mxCell .../> or a block element
    // <mxCell ...> ... </mxCell>. Unfinished ones are left out because they don't match.
-    const regex = /<mxCell\b[^>]*(?:\/>|>([\s\S]*?)<\/mxCell>)/g
+    const regex =
+        /<mxCell\b(?:[^<>"']|"[^"]*"|'[^']*')*?(?:\/>|>([\s\S]*?)<\/mxCell>)/g
    let match: RegExpExecArray | null
    let result = "<root>\n"

@@ -217,12 +227,18 @@ export function convertToLegalXml(xmlString: string): string {
 }

 /**
- * Replace nodes in a Draw.io XML diagram
+ * Replace the cells of one page of a Draw.io XML document
 * @param currentXML - The original Draw.io XML string
 * @param nodes - The XML string containing new nodes to replace in the diagram
+ * @param pageId - The page whose cells are replaced; the first page when
+ * missing or not found
 * @returns The updated XML string with replaced nodes
 */
-export function replaceNodes(currentXML: string, nodes: string): string {
+export function replaceNodes(
+    currentXML: string,
+    nodes: string,
+    pageId?: string | null,
+): string {
    // Check for valid inputs
    if (!currentXML || !nodes) {
        throw new Error("Both currentXML and nodes must be provided")
@@ -241,16 +257,23 @@ export function replaceNodes(currentXML: string, nodes: string): string {

        const nodesDoc = parser.parseFromString(nodesString, "text/xml")

+        // The page to draw on, when the document has it
+        const page = pageId
+            ? Array.from(currentDoc.getElementsByTagName("diagram")).find(
+                  (diagram) => diagram.getAttribute("id") === pageId,
+              )
+            : undefined
+        const scope: ParentNode = page ?? currentDoc
        // Find the root element in the current document
-        let currentRoot = currentDoc.querySelector("mxGraphModel > root")
+        let currentRoot = scope.querySelector("mxGraphModel > root")
        if (!currentRoot) {
            // If no root element is found, create the proper structure
            const mxGraphModel =
-                currentDoc.querySelector("mxGraphModel") ||
+                scope.querySelector("mxGraphModel") ||
                currentDoc.createElement("mxGraphModel")

            if (!currentDoc.contains(mxGraphModel)) {
-                currentDoc.appendChild(mxGraphModel)
+                ;(page ?? currentDoc).appendChild(mxGraphModel)
            }

            currentRoot = currentDoc.createElement("root")
@@ -320,10 +343,13 @@ export function replaceNodes(currentXML: string, nodes: string): string {

 /**
 * Decode an xmlsvg export (SVG data URL) into uncompressed diagram XML.
- * Only the first page is returned; for the full multi-page document use the
- * autosaved chartXML instead.
+ * One page is returned: the one with the given id, else the first; for the
+ * full multi-page document use the autosaved chartXML instead.
 */
-export function extractDiagramXML(xml_svg_string: string): string {
+export function extractDiagramXML(
+    xml_svg_string: string,
+    pageId?: string | null,
+): string {
    try {
        // 1. Parse the SVG string (using built-in DOMParser in a browser-like environment)
        const svgString = atob(xml_svg_string.slice(26))
@@ -347,7 +373,13 @@ export function extractDiagramXML(xml_svg_string: string): string {

        // 4. Parse the XML content
        const xmlDoc = parser.parseFromString(xmlContent, "text/xml")
-        const diagramElement = xmlDoc.querySelector("diagram")
+        const diagrams = Array.from(xmlDoc.getElementsByTagName("diagram"))
+        const diagramElement =
+            (pageId &&
+                diagrams.find(
+                    (diagram) => diagram.getAttribute("id") === pageId,
+                )) ||
+            diagrams[0]

        if (!diagramElement) {
            throw new Error("No diagram element found")
@@ -45,11 +45,11 @@
        "@aihubmix/ai-sdk-provider": "^2.2.1",
        "@aws-sdk/client-dynamodb": "^3.957.0",
        "@aws-sdk/credential-providers": "^3.943.0",
-        "@extractus/article-extractor": "^9.0.0",
+        "@extractus/article-extractor": "^8.0.18",
        "@formatjs/intl-localematcher": "^0.9.0",
-        "@langfuse/client": "^5.0.0",
-        "@langfuse/otel": "^5.0.0",
-        "@langfuse/tracing": "^5.0.0",
+        "@langfuse/client": "^4.4.9",
+        "@langfuse/otel": "^4.4.4",
+        "@langfuse/tracing": "^4.4.9",
        "@next/third-parties": "^16.0.6",
        "@opennextjs/cloudflare": "^1.17.1",
        "@openrouter/ai-sdk-provider": "^2.10.0",
@@ -74,13 +74,13 @@
        "cmdk": "^1.1.1",
        "idb": "^8.0.3",
        "jsonrepair": "^3.13.1",
-        "lucide-react": "^1.0.0",
-        "motion": "^14.0.0",
-        "nanoid": "^6.0.0",
+        "lucide-react": "^0.577.0",
+        "motion": "^12.23.25",
+        "nanoid": "^5.0.0",
        "negotiator": "^1.0.0",
        "next": "^16.0.7",
        "ollama-ai-provider-v2": "^3.6.0",
-        "pako": "^3.0.0",
+        "pako": "^2.1.0",
        "prism-react-renderer": "^2.4.1",
        "react": "^19.1.2",
        "react-dom": "^19.1.2",
@@ -119,27 +119,27 @@
        "@testing-library/user-event": "^14.6.1",
        "@types/negotiator": "^0.6.4",
        "@types/node": "^24.0.0",
-        "@types/pako": "^3.0.0",
+        "@types/pako": "^2.0.3",
        "@types/react": "^19",
        "@types/react-dom": "^19",
        "@types/turndown": "^5.0.6",
-        "@vitejs/plugin-react": "^6.0.0",
-        "@vitest/coverage-v8": "^5.0.0",
-        "concurrently": "^10.0.0",
+        "@vitejs/plugin-react": "^5.1.2",
+        "@vitest/coverage-v8": "^4.0.16",
+        "concurrently": "^9.2.1",
        "cross-env": "^10.1.0",
-        "electron": "^39.2.7",
+        "electron": "^41.10.6",
        "electron-builder": "^26.0.12",
        "esbuild": "^0.28.0",
-        "eslint": "10.12.0",
+        "eslint": "9.39.5",
        "eslint-config-next": "16.1.6",
        "husky": "^9.1.7",
-        "jsdom": "^30.0.0",
-        "lint-staged": "^17.0.0",
+        "jsdom": "^27.4.0",
+        "lint-staged": "^16.2.7",
        "shx": "^0.4.0",
        "tailwindcss": "^4",
-        "typescript": "^7.0.0",
+        "typescript": "^5",
        "vite-tsconfig-paths": "^6.0.3",
-        "vitest": "^5.0.0",
+        "vitest": "^4.0.16",
        "wait-on": "^9.0.3",
        "wrangler": "^4.60.0"
    },
@@ -42,16 +42,16 @@
        "@modelcontextprotocol/sdk": "^1.31.0",
        "linkedom": "^0.18.0",
        "open": "^11.0.0",
-        "pako": "^3.0.0",
+        "pako": "^2.2.0",
        "saxes": "^6.0.0",
        "zod": "^4.0.0"
    },
    "devDependencies": {
        "@types/node": "^24.0.0",
-        "@types/pako": "^3.0.0",
+        "@types/pako": "^2.0.4",
        "tsx": "^4.19.0",
-        "typescript": "^7.0.0",
-        "vitest": "^5.0.0"
+        "typescript": "^5",
+        "vitest": "^4.1.8"
    },
    "engines": {
        "node": ">=18"
@@ -0,0 +1,196 @@
+/**
+ * Compact cells: the short way the model writes shapes and edges.
+ *
+ * A shape is one self-closing mxCell with its position and size as x, y, w
+ * and h attributes; an edge is one with source and target. The fixed parts
+ * of draw.io's XML are left out and filled in here:
+ *
+ *   <mxCell id="2" value="Start" style="step;" x="40" y="40" w="120" h="60"/>
+ *   <mxCell id="5" style="down;" source="2" target="3"/>
+ *
+ * becomes
+ *
+ *   <mxCell id="2" value="Start" style="step;" vertex="1" parent="1">
+ *     <mxGeometry x="40" y="40" width="120" height="60" as="geometry"/>
+ *   </mxCell>
+ *   <mxCell id="5" style="down;" edge="1" parent="1" source="2" target="3">
+ *     <mxGeometry relative="1" as="geometry"/>
+ *   </mxCell>
+ *
+ * The long form stays accepted, and anything beyond the plain case (edge
+ * waypoints, a label on an edge, a parent other than the layer) is written
+ * the long way, so a cell may mix both: compact attributes with an explicit
+ * parent, for example. A cell is an edge when it says so or connects a
+ * source or target, a shape when it says so, has a size or has a geometry.
+ *
+ * foldCells is the reverse, for the diagram shown to the model: it writes
+ * the plain shapes and edges compactly and leaves everything else as it is,
+ * so the model reads the notation it is asked to write. Folding then
+ * expanding gives the same cells back.
+ */
+import { readAttributes, type TagAttribute } from "./xml-attributes.ts"
+
+// A whole mxCell: self-closing, or with its children (cells never nest)
+const CELL_BLOCK =
+    /<mxCell\b((?:[^<>"']|"[^"]*"|'[^']*')*?)\s*(?:\/>|>([\s\S]*?)<\/mxCell>)/g
+
+// The cell's own geometry, as opposed to one inside its custom data
+const OWN_GEOMETRY = /<mxGeometry\b(?:[^<>"']|"[^"]*"|'[^']*')*?\bas="geometry"/
+
+// The four compact attributes and the names draw.io uses for them
+const SIZE_ATTRS = new Map([
+    ["x", "x"],
+    ["y", "y"],
+    ["w", "width"],
+    ["h", "height"],
+    ["width", "width"],
+    ["height", "height"],
+])
+const isSize = (name: string) => SIZE_ATTRS.has(name)
+
+// Attributes a cell is written with, in draw.io's usual order
+const FIRST = ["id", "value", "style"]
+const LAST = ["vertex", "edge", "parent", "source", "target"]
+
+// A value read from a single-quoted attribute may hold a double quote
+const attr = (name: string, value: string) =>
+    ` ${name}="${value.replace(/"/g, "&quot;")}"`
+const attributeText = (attrs: TagAttribute[]) =>
+    attrs.map((a) => attr(a.name, a.value)).join("")
+
+/** The id of the page's first layer (a cell whose parent is "0"), or "1" */
+export function defaultLayerOf(xml: string): string {
+    for (const [, attrText] of xml.matchAll(CELL_BLOCK)) {
+        const attrs = new Map(
+            readAttributes(attrText).map((a) => [a.name, a.value]),
+        )
+        if (attrs.get("parent") === "0" && attrs.get("id")) {
+            return attrs.get("id") ?? "1"
+        }
+    }
+    return "1"
+}
+
+/**
+ * Turn compact shapes and edges into standard draw.io cells. A cell with no
+ * parent goes on `layer`, the page's first layer ("1" on a new page).
+ */
+export function expandCompactCells(xml: string, layer = "1"): string {
+    return xml.replace(CELL_BLOCK, (block, attrText: string, body?: string) => {
+        const attrs = readAttributes(attrText)
+        const byName = new Map(attrs.map((a) => [a.name, a.value]))
+        const size = attrs.filter((a) => isSize(a.name))
+        const inner = body ?? ""
+        const hasGeometry = OWN_GEOMETRY.test(inner)
+        const isEdge =
+            byName.get("edge") === "1" ||
+            (byName.get("vertex") !== "1" &&
+                (byName.has("source") || byName.has("target")))
+        const isVertex =
+            !isEdge &&
+            (byName.get("vertex") === "1" || size.length > 0 || hasGeometry)
+        // Root cells and anything else the model wrote in full are left alone
+        if (!isEdge && !isVertex) return block
+        const complete =
+            size.length === 0 &&
+            byName.has(isEdge ? "edge" : "vertex") &&
+            byName.has("parent") &&
+            hasGeometry
+        if (complete) return block
+
+        // The compact attributes become the geometry; when the cell has its
+        // own geometry already they stay as written, in case they mean
+        // something else to whoever wrote them
+        const consumed = !hasGeometry && isVertex
+        const rest = attrs.filter(
+            (a) =>
+                !FIRST.includes(a.name) &&
+                !LAST.includes(a.name) &&
+                !(consumed && isSize(a.name)) &&
+                !(isEdge && isSize(a.name)),
+        )
+        // Rebuilt in the usual order: id, value, style, the rest, then the
+        // flags and the connections
+        const ordered: [string, string][] = [
+            ...FIRST.flatMap((n): [string, string][] =>
+                byName.has(n) ? [[n, byName.get(n) ?? ""]] : [],
+            ),
+            ...rest.map((a): [string, string] => [a.name, a.value]),
+            [isEdge ? "edge" : "vertex", "1"],
+            ["parent", byName.get("parent") ?? layer],
+            ...["source", "target"].flatMap((n): [string, string][] =>
+                byName.has(n) ? [[n, byName.get(n) ?? ""]] : [],
+            ),
+        ]
+        const written = ordered.map(([n, v]) => attr(n, v)).join("")
+        let geometry = ""
+        if (!hasGeometry) {
+            if (isEdge) {
+                geometry = '<mxGeometry relative="1" as="geometry"/>'
+            } else {
+                const get = (short: string, long: string, fallback: string) =>
+                    byName.get(short) ?? byName.get(long) ?? fallback
+                geometry = `<mxGeometry${attr("x", get("x", "x", "0"))}${attr("y", get("y", "y", "0"))}${attr("width", get("w", "width", "120"))}${attr("height", get("h", "height", "60"))} as="geometry"/>`
+            }
+        }
+        return `<mxCell${written}>${geometry}${inner}</mxCell>`
+    })
+}
+
+/** Attributes of a single self-closing mxGeometry, or null for anything else */
+function plainGeometry(body: string): Map<string, string> | null {
+    const trimmed = body.trim()
+    const m = trimmed.match(
+        /^<mxGeometry\b((?:[^<>"']|"[^"]*"|'[^']*')*?)\s*\/>$/,
+    )
+    if (!m) return null
+    const attrs = new Map(readAttributes(m[1]).map((a) => [a.name, a.value]))
+    // Anything odd, such as a wrong "as", stays as written so folding and
+    // expanding give the same cells back
+    return attrs.get("as") === "geometry" ? attrs : null
+}
+
+/**
+ * Write plain shapes and edges compactly, for the diagram shown to the
+ * model. A shape is plain when its only child is an mxGeometry with x, y,
+ * width and height; an edge when its only child is the relative geometry.
+ * Both must name their parent, since expanding fills in the layer for a
+ * missing one. Everything else, including wrapped cells' extra data and
+ * edge labels, is left as written.
+ */
+export function foldCells(xml: string, layer = "1"): string {
+    return xml.replace(CELL_BLOCK, (block, attrText: string, body?: string) => {
+        if (body === undefined) return block
+        const attrs = readAttributes(attrText)
+        const byName = new Map(attrs.map((a) => [a.name, a.value]))
+        if (attrs.some((a) => isSize(a.name))) return block
+        if (!byName.has("parent")) return block
+        const geometry = plainGeometry(body)
+        if (!geometry) return block
+        const geometryKeys = [...geometry.keys()]
+            .filter((k) => k !== "as")
+            .sort()
+        const kept = attrs.filter(
+            (a) =>
+                a.name !== "vertex" &&
+                a.name !== "edge" &&
+                !(a.name === "parent" && a.value === layer),
+        )
+        if (byName.get("vertex") === "1" && byName.get("edge") !== "1") {
+            if (geometryKeys.join() !== "height,width,x,y") return block
+            const size = `${attr("x", geometry.get("x") ?? "")}${attr("y", geometry.get("y") ?? "")}${attr("w", geometry.get("width") ?? "")}${attr("h", geometry.get("height") ?? "")}`
+            return `<mxCell${attributeText(kept)}${size}/>`
+        }
+        if (byName.get("edge") === "1" && byName.get("vertex") !== "1") {
+            if (
+                geometryKeys.join() !== "relative" ||
+                geometry.get("relative") !== "1"
+            ) {
+                return block
+            }
+            if (!byName.has("source") || !byName.has("target")) return block
+            return `<mxCell${attributeText(kept)}/>`
+        }
+        return block
+    })
+}
@@ -9,6 +9,7 @@

 import {
    indent,
+    STYLE_CLASS_EXAMPLE,
    SWIMLANE_EXAMPLE,
    TWO_EDGES_EXAMPLE,
    WAYPOINT_EXAMPLE,
@@ -26,21 +27,17 @@ export const DRAWING_GUIDE = `# Draw.io drawing guide
 - The preview page has History (it saves a snapshot before every AI change and can restore any of the last 20 versions) and Download. You can make changes freely; nothing is lost.

 ## The XML you send
-Single page (create_new_diagram, add_page): send ONLY the mxCell elements. The server adds <mxfile>, <mxGraphModel>, <root> and the root cells id="0" and id="1".
+Single page (create_new_diagram, add_page): send ONLY the named styles and the mxCell elements. The server adds <mxfile>, <mxGraphModel>, <root> and the root cells id="0" and id="1", expands named styles (see Styles), adds html=1 to every cell and whiteSpace=wrap to shapes, and fills in vertex, edge, parent="1" and the mxGeometry element. A shape is one self-closing mxCell with x, y, w and h; an edge is one with source and target. A cell with source or target is always an edge. Write parent only for a shape inside a container, and an mxGeometry element only for edge waypoints or for a separate label cell placed on an edge: <mxCell id="9" value="yes" style="edgeLabel;" parent="<edge id>" connectable="0"><mxGeometry x="-0.5" relative="1" as="geometry"/></mxCell>. An edge's own text simply goes in its value.

-    <mxCell id="2" value="Label" style="rounded=1;whiteSpace=wrap;html=1;" vertex="1" parent="1">
-      <mxGeometry x="100" y="100" width="120" height="60" as="geometry"/>
-    </mxCell>
-    <mxCell id="3" style="edgeStyle=orthogonalEdgeStyle;exitX=1;exitY=0.5;entryX=0;entryY=0.5;endArrow=classic;html=1;" edge="1" parent="1" source="2" target="4">
-      <mxGeometry relative="1" as="geometry"/>
-    </mxCell>
+    <mxCell id="2" value="Label" style="rounded=1;" x="100" y="100" w="120" h="60"/>
+    <mxCell id="3" style="edgeStyle=orthogonalEdgeStyle;exitX=1;exitY=0.5;entryX=0;entryY=0.5;" source="2" target="4"/>

 Several pages at once (create_new_diagram only): send a full <mxfile> with one <diagram id="..." name="..."> per page. Every page's <root> must start with <mxCell id="0"/><mxCell id="1" parent="0"/>.

 Rules (XML that breaks them is rejected):
 1. All mxCell elements are siblings. NEVER nest an mxCell inside another mxCell.
 2. Ids are unique within a page and start from "2" ("0" and "1" are the root cells).
-3. parent="1" for top-level shapes, parent="<container id>" for shapes inside a container.
+3. parent="<container id>" for shapes inside a container; top-level cells need no parent.
 4. Edge source and target must reference existing cell ids.
 5. Escape special characters in attribute values: &lt; for <, &gt; for >, &amp; for &, &quot; for ".
 6. NEVER include XML comments (<!-- -->). draw.io strips them.
@@ -59,7 +56,7 @@ ${indent(SWIMLANE_EXAMPLE)}
 ## Edge routing rules
 Rule 1: Never let two edges share a path. Two edges between the same nodes exit and enter at different points (exitY=0.3 for the first, exitY=0.7 for the second, not both 0.5).
 Rule 2: For bidirectional connections (A to B and B to A), use opposite sides: A exits right (exitX=1) into the left of B (entryX=0); B exits left (exitX=0) into the right of A (entryX=1).
-Rule 3: Always set exitX, exitY, entryX and entryY in the edge style, e.g. style="edgeStyle=orthogonalEdgeStyle;exitX=1;exitY=0.3;entryX=0;entryY=0.3;endArrow=classic;".
+Rule 3: Always set exitX, exitY, entryX and entryY in the edge style, e.g. style="edgeStyle=orthogonalEdgeStyle;exitX=1;exitY=0.3;entryX=0;entryY=0.3;".
 Rule 4: Route edges AROUND shapes in the way. Before drawing an edge, find every shape between source and target; if one is in the path, add waypoints. Route diagonal connections along the outside of the diagram, not through the middle. Keep 20-30px clearance from shapes. An edge must never cross another shape's box.
 Rule 5: Plan the layout first. Organize shapes into rows or columns following the flow, space them 150-200px apart so edges have room, and prefer one flow direction (left to right or top to bottom).
 Rule 6: Use 2-3 waypoints for L-shaped or U-shaped paths. Each change of direction needs a waypoint, and segments should be horizontal or vertical.
@@ -80,27 +77,33 @@ Waypoints go inside <Array as="points"> in the edge geometry. Example: Hotfix (r
 ${indent(WAYPOINT_EXAMPLE)}

 ## Styles
- Shapes: rounded=1, fillColor=#hex, strokeColor=#hex, whiteSpace=wrap;html=1;
- Edges: endArrow=classic, block, open or none; startArrow=none or classic; curved=1; edgeStyle=orthogonalEdgeStyle
- Text: fontSize=14, fontStyle=1 (bold), align=center, left or right
+Define each style used by several cells ONCE, as a named style before the cells, and use the name in the cells like a CSS class. A cell's style can combine a shape token, a name and overrides; later pairs win. Name only styles that two or more cells share; a style used by one cell stays inline. Names must not be draw.io's own style names: shapes such as text, ellipse, rhombus, swimlane, label, image, and colors such as blue, green, red, gray, yellow, orange, purple, pink. A definition applies to the call it is in: each create_new_diagram or add_page call defines the names it uses. The server expands the names, so the saved file is standard draw.io XML.
+
+${indent(STYLE_CLASS_EXAMPLE)}
+
+- NEVER write html=1 or whiteSpace=wrap: the server adds html=1 to every cell and whiteSpace=wrap to shapes. Labels are HTML: use &lt;br&gt; for a line break and &lt;b&gt; for bold, never \\n; a literal < or > in a label is written &amp;lt; or &amp;gt;.
+- Do NOT repeat what draw.io already uses. For a plain shape: rounded=0, align=center, verticalAlign=middle, fontSize=12, strokeWidth=1, fillColor=#ffffff, strokeColor=#000000, fontColor=#000000. For an edge: endArrow=classic, strokeColor=#000000. Writing one of them is right only when it overrides what a name or the shape sets: an edge is rounded by default, so rounded=0 on an edge is a real setting, and a text cell is left/top aligned by default, so there align=center or verticalAlign=middle are real settings.
+- Shapes: rounded=1, fillColor=#hex, strokeColor=#hex
+- Edges: endArrow=block, open or none; startArrow=classic; curved=1; dashed=1; edgeStyle=orthogonalEdgeStyle
+- Text: fontSize=14, fontStyle=1 (bold), align=center or right
 - Animated connectors: add flowAnimation=1 to the edge style.

 ## Minimal style
 When the user asks for a minimal, plain, black-and-white or unstyled diagram, use these rules instead of the styles above:
 - No fillColor, strokeColor, rounded, fontSize, fontStyle or hex colors.
- Shapes use style "whiteSpace=wrap;html=1;", edges use "html=1;endArrow=classic;".
- Containers that hold other shapes use "whiteSpace=wrap;html=1;fillColor=none;" so they do not cover their children.
+- Shapes have no style, or only the shape (ellipse, rhombus); edges have edgeStyle=orthogonalEdgeStyle plus the exit and entry points from the routing rules, nothing else.
+- Containers that hold other shapes use "fillColor=none;" so they do not cover their children.
 - Keep at least 50px between elements, and follow all edge routing rules strictly.

 ## Editing with edit_diagram
- update replaces a cell: send the complete mxCell including mxGeometry, with the same id as cell_id.
+- update replaces a cell: send the complete mxCell in the same compact form (x, y, w, h for a shape), with the same id as cell_id. Named styles are not available here: write each cell's complete style.
 - add inserts a new cell with a new id. One cell per operation.
 - delete removes a cell. Its children and every edge connected to it are deleted too, so give only the container's id.
 - All-or-nothing: if any operation fails, nothing is applied. A rejected call includes the current XML of the page; rebuild your operations on it and retry.
 - If the diagram is large, change it with edit_diagram instead of redrawing it.

-    {"operations": [{"operation": "update", "cell_id": "3", "new_xml": "<mxCell id=\\"3\\" value=\\"New Label\\" style=\\"rounded=1;\\" vertex=\\"1\\" parent=\\"1\\"><mxGeometry x=\\"100\\" y=\\"100\\" width=\\"120\\" height=\\"60\\" as=\\"geometry\\"/></mxCell>"}]}
-    {"page_name": "CNN", "operations": [{"operation": "add", "cell_id": "conv-1", "new_xml": "<mxCell id=\\"conv-1\\" value=\\"Conv\\" vertex=\\"1\\" parent=\\"1\\"><mxGeometry x=\\"40\\" y=\\"40\\" width=\\"120\\" height=\\"60\\" as=\\"geometry\\"/></mxCell>"}]}
+    {"operations": [{"operation": "update", "cell_id": "3", "new_xml": "<mxCell id=\\"3\\" value=\\"New Label\\" style=\\"rounded=1;\\" x=\\"100\\" y=\\"100\\" w=\\"120\\" h=\\"60\\"/>"}]}
+    {"page_name": "CNN", "operations": [{"operation": "add", "cell_id": "conv-1", "new_xml": "<mxCell id=\\"conv-1\\" value=\\"Conv\\" x=\\"40\\" y=\\"40\\" w=\\"120\\" h=\\"60\\"/>"}]}
    {"page_index": 1, "operations": [{"operation": "delete", "cell_id": "5"}]}

 Pages: list_pages shows every page's id, name and index. edit_diagram, get_diagram and export_diagram take an optional page_id, page_name or page_index; without one they use the first page.
@@ -7,11 +7,13 @@
 * so the model never builds on a half-applied edit.
 */

+import { defaultLayerOf, expandCompactCells } from "./compact-cells.ts"
 import {
    applyDiagramOperations,
    type DiagramOperation,
 } from "./diagram-operations.ts"
 import { type PageSelector, projectPage } from "./pages.ts"
+import { addDefaultStyles, edgeIdsOf } from "./style-classes.ts"
 import { validateAndFixXml, validateMxCellStructure } from "./xml-validation.ts"

 export type EditOutcome =
@@ -48,11 +50,22 @@ export function editDiagram(
    const fixes: string[] = []
    const prepared: DiagramOperation[] = []

+    // Edges already on the page, so a label added to one is not wrapped, and
+    // the layer a compact cell without a parent goes on
+    const page = targetPageXml(xml, selector)
+    const edges = edgeIdsOf(page)
+    const layer = defaultLayerOf(page)
    for (const op of operations) {
        if (op.operation === "delete" || !op.new_xml) {
            prepared.push(op)
            continue
        }
+        if (/<mxStyle\b/i.test(op.new_xml)) {
+            errors.push(
+                `${op.operation} ${op.cell_id}: named styles (mxStyle) are not available in edit_diagram; write the cell's complete style`,
+            )
+            continue
+        }
        // Checked before validation: several cells fail the strict parser
        // with a misleading "only one root" syntax error.
        if (countTopLevelElements(op.new_xml) > 1) {
@@ -71,7 +84,15 @@ export function editDiagram(
        if (check.fixed) {
            fixes.push(`${op.cell_id}: ${check.fixes.join(", ")}`)
        }
-        prepared.push({ ...op, new_xml: check.fixed ?? op.new_xml })
+        // The defaults the model is told not to write (style-classes.ts),
+        // added after the fixes so a repaired cell gets them too
+        prepared.push({
+            ...op,
+            new_xml: addDefaultStyles(
+                expandCompactCells(check.fixed ?? op.new_xml, layer),
+                edges,
+            ),
+        })
    }
    if (errors.length > 0) return { ok: false, errors, pageError: false }

@@ -23,6 +23,7 @@ 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 { expandCompactCells, foldCells } from "./compact-cells.ts"
 import type { DiagramOperation } from "./diagram-operations.ts"
 import { installDomPolyfill } from "./dom.ts"
 import { DRAWING_GUIDE } from "./drawing-guide.ts"
@@ -48,7 +49,11 @@ import {
 } from "./http-server.ts"
 import { parseDrawioFileContent } from "./load-diagram.ts"
 import { log } from "./logger.ts"
-import { prepareNewDiagram, reservedIdError } from "./new-diagram.ts"
+import {
+    prepareNewDiagram,
+    reservedIdError,
+    takeStyleDefinitions,
+} from "./new-diagram.ts"
 import {
    addPageToDoc,
    deletePageFromDoc,
@@ -66,6 +71,7 @@ import {
 } from "./pages.ts"
 import { Autosaver, defaultDataDir, expandHome } from "./persistence.ts"
 import { getShapeLibrary, SHAPE_LIBRARY_LIST } from "./shape-library.ts"
+import { addDefaultStyles, applyStyleClasses } from "./style-classes.ts"
 import { validateAndFixXml } from "./xml-validation.ts"

 // DOMParser/XMLSerializer globals for the XML helpers (Node has neither)
@@ -336,11 +342,11 @@ Before using icon shapes (AWS, Azure, GCP, Kubernetes, Cisco...), call get_shape

 Accepted xml:
 1) Only the mxCell elements of one page (recommended). The server adds <mxfile>, <mxGraphModel>, <root> and the root cells "0" and "1":
-<mxCell id="2" value="Shape" style="rounded=1;whiteSpace=wrap;html=1;" vertex="1" parent="1"><mxGeometry x="40" y="40" width="120" height="60" as="geometry"/></mxCell>
+<mxCell id="2" value="Shape" style="rounded=1;" x="40" y="40" w="120" h="60"/>
 2) A bare <mxGraphModel> with <root> (one page).
 3) A full <mxfile> with one or more <diagram> pages. Every page's <root> must start with <mxCell id="0"/><mxCell id="1" parent="0"/>.

-Rules: cells are siblings (never nested), ids are unique per page and start from "2", parent="1" for top-level shapes, no XML comments, and shapes stay within x 0 to 800 and y 0 to 600.`,
+Rules: cells are siblings (never nested), ids are unique per page and start from "2", parent only for shapes inside a container, no XML comments, and shapes stay within x 0 to 800 and y 0 to 600. A style used by several cells is defined once with <mxStyle name="..." value="..."/> before the cells and used by name (see the drawing guide); html=1 and whiteSpace=wrap are added automatically.`,
        inputSchema: {
            xml: z
                .string()
@@ -589,10 +595,10 @@ registerWriteTool(
            "- add: Add a new cell. Provide cell_id (new unique id within the page) and new_xml. One cell per operation.\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. Its children and connected edges are deleted too, so give only a container's id.\n\n" +
-            "For add/update, new_xml must be a complete mxCell element including mxGeometry. No XML comments. " +
+            "For add/update, new_xml is the complete mxCell in the compact form (a shape with x, y, w, h; an edge with source and target). No XML comments. " +
            'Every " inside new_xml must be escaped as \\" in the JSON.\n\n' +
            "Example - Add a rectangle on the default (first) page:\n" +
-            '{"operations": [{"operation": "add", "cell_id": "rect-1", "new_xml": "<mxCell id=\\"rect-1\\" value=\\"Hello\\" style=\\"rounded=0;\\" vertex=\\"1\\" parent=\\"1\\"><mxGeometry x=\\"100\\" y=\\"100\\" width=\\"120\\" height=\\"60\\" as=\\"geometry\\"/></mxCell>"}]}\n\n' +
+            '{"operations": [{"operation": "add", "cell_id": "rect-1", "new_xml": "<mxCell id=\\"rect-1\\" value=\\"Hello\\" style=\\"rounded=1;\\" x=\\"100\\" y=\\"100\\" w=\\"120\\" h=\\"60\\"/>"}]}\n\n' +
            "Example - Delete a cell on the default page:\n" +
            '{"operations": [{"operation": "delete", "cell_id": "rect-1"}]}',
        inputSchema: {
@@ -700,7 +706,7 @@ registerWriteTool(
                    content: [
                        {
                            type: "text",
-                            text: `Error: ${reason}\n\nCurrent XML of ${describeSelector(pageSelector)}:\n\n${targetPageXml(currentSession.xml, pageSelector)}\n\n${next}`,
+                            text: `Error: ${reason}\n\nCurrent XML of ${describeSelector(pageSelector)}:\n\n${foldCells(targetPageXml(currentSession.xml, pageSelector))}\n\n${next}`,
                        },
                    ],
                    isError: true,
@@ -720,7 +726,7 @@ registerWriteTool(
                log.warn(`Edit rejected: ${outcome.errors.join("; ")}`)
                const text = outcome.pageError
                    ? `Error: ${outcome.errors[0]}`
-                    : `Error: No changes were made because ${outcome.errors.length} operation(s) failed:\n${outcome.errors.map((e) => `- ${e}`).join("\n")}\n\nCurrent XML of ${describeSelector(pageSelector)}:\n\n${targetPageXml(currentSession.xml, pageSelector)}\n\nFix the operations against this XML and retry.`
+                    : `Error: No changes were made because ${outcome.errors.length} operation(s) failed:\n${outcome.errors.map((e) => `- ${e}`).join("\n")}\n\nCurrent XML of ${describeSelector(pageSelector)}:\n\n${foldCells(targetPageXml(currentSession.xml, pageSelector))}\n\nFix the operations against this XML and retry.`
                return {
                    content: [{ type: "text", text }],
                    isError: true,
@@ -869,7 +875,7 @@ server.registerTool(
                    content: [
                        {
                            type: "text",
-                            text: `Current diagram XML:\n\n${session.xml}\n\n${pageList}${staleNote}`,
+                            text: `Current diagram XML:\n\n${foldCells(session.xml)}\n\n${pageList}${staleNote}`,
                        },
                    ],
                }
@@ -906,7 +912,7 @@ server.registerTool(
                content: [
                    {
                        type: "text",
-                        text: `Page ${projection.index} ("${projection.name}"):\n\n${projection.xml}\n\n${pageList}${staleNote}${otherPagesNote}`,
+                        text: `Page ${projection.index} ("${projection.name}"):\n\n${foldCells(projection.xml)}\n\n${pageList}${staleNote}${otherPagesNote}`,
                    },
                ],
            }
@@ -1587,14 +1593,28 @@ registerWriteTool(

            // If caller provided XML, validate it before splicing it in so we
            // never get a half-broken mxfile written to the session.
-            const reserved = xml && reservedIdError(xml)
+            // Named style definitions come out first and are expanded on the
+            // validated XML, like prepareNewDiagram
+            const {
+                classes,
+                xml: startXml,
+                error: styleError,
+            } = takeStyleDefinitions(xml ?? "")
+            if (styleError) {
+                return {
+                    content: [{ type: "text", text: `Error: ${styleError}` }],
+                    isError: true,
+                }
+            }
+            const reserved = startXml && reservedIdError(startXml)
            if (reserved) {
                return {
                    content: [{ type: "text", text: `Error: ${reserved}` }],
                    isError: true,
                }
            }
-            let cleanXml: string | undefined = xml && wrapCellsInModel(xml)
+            let cleanXml: string | undefined =
+                startXml && wrapCellsInModel(startXml)
            if (cleanXml) {
                const { valid, error, fixed, fixes } =
                    validateAndFixXml(cleanXml)
@@ -1615,6 +1635,9 @@ registerWriteTool(
                        isError: true,
                    }
                }
+                cleanXml = addDefaultStyles(
+                    applyStyleClasses(expandCompactCells(cleanXml), classes),
+                )
            }

            let info
@@ -2,8 +2,16 @@
 * A whole new diagram written by the model, for the create_new_diagram tool
 * and the web app's display_diagram tool.
 */
-import { normalizeToMxfile, wrapCellsInModel } from "./pages.ts"
+import { expandCompactCells } from "./compact-cells.ts"
+import { hasCells, normalizeToMxfile, wrapCellsInModel } from "./pages.ts"
+import {
+    addDefaultStyles,
+    applyStyleClasses,
+    readStyleClasses,
+    type StyleClasses,
+} from "./style-classes.ts"
 import { readAttributes } from "./xml-attributes.ts"
+import { getXmlSyntaxError } from "./xml-syntax.ts"
 import { validateAndFixXml } from "./xml-validation.ts"

 export type NewDiagram =
@@ -29,11 +37,15 @@ export function reservedIdError(input: string): string | null {
        )
        const id = attrs.get("id")
        if (id !== "0" && id !== "1") continue
-        // A wrapper's id is its cell's; an mxCell counts as a shape or edge
+        // A wrapper's id is its cell's; an mxCell counts as a shape or edge,
+        // also when written compactly (a size, or a connection)
        if (
            tag !== "mxCell" ||
            attrs.get("vertex") === "1" ||
-            attrs.get("edge") === "1"
+            attrs.get("edge") === "1" ||
+            ["x", "y", "w", "h", "width", "height", "source", "target"].some(
+                (a) => attrs.has(a),
+            )
        ) {
            return 'Cell ids "0" and "1" are the root cells, which are added automatically. Give shapes and edges ids starting at "2".'
        }
@@ -42,23 +54,64 @@ export function reservedIdError(input: string): string | null {
 }

 /**
- * Bare cells get the wrapper and root cells first, since the strict parser
- * rejects several top-level elements. Then the XML is validated and
- * auto-fixed while it is still a bare model, where duplicate ids are
- * renamed, and finally turned into an <mxfile>.
+ * The named style definitions are taken out first (style-classes.ts). Bare
+ * cells then get the wrapper and root cells, since the strict parser rejects
+ * several top-level elements. Then the XML is validated and auto-fixed while
+ * it is still a bare model, where duplicate ids are renamed. Compact cells
+ * (compact-cells.ts) are expanded, the names expanded and the default styles
+ * added on the fixed XML, so repaired cells get them too, and finally it is
+ * turned into an <mxfile>.
 */
+/**
+ * Take the named style definitions out of the model's XML (style-classes.ts).
+ * Returns the error for the model when a definition never closed or when
+ * nothing but definitions was sent.
+ */
+export function takeStyleDefinitions(input: string): {
+    classes: StyleClasses
+    xml: string
+    error: string | null
+} {
+    const { classes, xml } = readStyleClasses(input)
+    let error: string | null = null
+    if (/<mxStyle\b/i.test(xml)) {
+        error =
+            'A named style definition is not closed. Write it as <mxStyle name="..." value="..."/> before the cells.'
+    } else if (classes.size > 0 && !hasCells(xml)) {
+        error =
+            "Only named style definitions were sent, no cells. Send the mxCell elements after the definitions."
+    }
+    return { classes, xml, error }
+}
+
 export function prepareNewDiagram(
    input: string,
    page: { pageId?: string; pageName?: string } = {},
 ): NewDiagram {
-    const reserved = reservedIdError(input)
+    const {
+        classes,
+        xml: cells,
+        error: styleError,
+    } = takeStyleDefinitions(input)
+    if (styleError) return { ok: false, error: styleError }
+    const reserved = reservedIdError(cells)
    if (reserved) return { ok: false, error: reserved }
-    let xml = wrapCellsInModel(input)
+    let xml = wrapCellsInModel(cells)
    const { valid, error, fixed, fixes } = validateAndFixXml(xml)
    if (fixed) xml = fixed
    if (!valid) {
        return { ok: false, error: `XML validation failed - ${error}` }
    }
+    xml = addDefaultStyles(applyStyleClasses(expandCompactCells(xml), classes))
+    // The rewrites copy attribute values as written; a check that they
+    // produced well-formed XML, in case one of them ever does not
+    const rewriteError = getXmlSyntaxError(xml)
+    if (rewriteError) {
+        return {
+            ok: false,
+            error: `XML validation failed after expanding the cells - ${rewriteError}`,
+        }
+    }
    const normalized = normalizeToMxfile(xml, page)
    if (!normalized) {
        return {
@@ -0,0 +1,232 @@
+/**
+ * Named styles, written once and used by name like CSS classes.
+ *
+ * The model defines a style before the cells and refers to it from any
+ * number of cells, so a style string is not repeated in every cell:
+ *
+ *   <mxStyle name="blue" value="fillColor=#dae8fc;strokeColor=#6c8ebf;"/>
+ *   <mxCell id="2" value="A" style="rounded=1;blue;" vertex="1" parent="1">...</mxCell>
+ *   <mxCell id="3" value="B" style="rhombus;blue;fontSize=14;" vertex="1" parent="1">...</mxCell>
+ *
+ * draw.io resolves a style token without "=" through its stylesheet, which
+ * is not saved in the file, so the names are expanded here and the saved
+ * XML is plain draw.io XML. A name without a definition is left as it is:
+ * draw.io ignores it, unless its own stylesheet knows the name (text,
+ * ellipse, label, blue, green, ...), which then keeps its meaning.
+ *
+ * html=1 and whiteSpace=wrap, which draw.io itself puts on every new shape,
+ * are added here too, so the model never has to write them.
+ *
+ * The callers validate and auto-fix the XML first and rewrite the styles
+ * after, so a repaired cell (quotes written as entities, a lowercase tag)
+ * gets its defaults too, and the rewrite only ever sees proper attributes.
+ */
+import { readAttributes } from "./xml-attributes.ts"
+
+export type StyleClasses = Map<string, string>
+
+// <mxStyle name="..." value="..."/> with the whitespace after it, also when
+// written as <mxStyle ...> or <mxStyle ...></mxStyle>; quoted values may hold ">"
+const STYLE_DEFINITION =
+    /<mxStyle\b((?:[^<>"']|"[^"]*"|'[^']*')*?)\s*\/?>(?:\s*<\/mxStyle>)?\s*/gi
+
+// An mxCell opening tag; the attributes stop before a closing "/" so a
+// self-closing cell keeps its "/>"
+const CELL_TAG = /<mxCell\b((?:[^<>"']|"[^"]*"|'[^']*')*?)\s*(\/?)>/g
+
+// draw.io reads keys and tokens as written, " html" is not "html", so the
+// checks are exact too
+/** Whether the style sets the key (as `key=` at the start or after a ";") */
+const hasKey = (style: string, key: string) =>
+    new RegExp(`(^|;)${key}=`).test(style)
+
+/** Whether the style holds this exact token */
+const hasToken = (style: string, token: string) =>
+    style.split(";").includes(token)
+
+/**
+ * Replace the names among the tokens with their definitions. The tokens are
+ * kept exactly as written, empty ones included: a leading ";" is draw.io's
+ * "no default style" marker, and an entity such as &quot; ends in ";" too.
+ * A name whose definition is empty is dropped, so it does not leave such a
+ * marker behind.
+ */
+function applyToStyle(style: string, classes: StyleClasses): string {
+    const out: string[] = []
+    for (const token of style.split(";")) {
+        const definition = token.includes("=")
+            ? undefined
+            : classes.get(token.trim())
+        if (definition === undefined) out.push(token)
+        else if (definition !== "") out.push(definition)
+    }
+    return out.join(";")
+}
+
+/**
+ * A definition's value goes into a style attribute unchecked by the XML
+ * validator (the definitions are taken out before it runs), so the two
+ * characters that would break the attribute are escaped here, the way the
+ * validator repairs them in cells.
+ */
+function escapeForAttribute(value: string): string {
+    return value
+        .replace(
+            /&(?!(?:lt|gt|amp|quot|apos|#[0-9]+|#x[0-9a-fA-F]+);)/g,
+            "&amp;",
+        )
+        .replace(/</g, "&lt;")
+}
+
+/**
+ * The definitions, resolved against each other, and the XML without them.
+ * A definition may use names defined before or after it; a name using
+ * itself stays a bare token.
+ */
+export function readStyleClasses(xml: string): {
+    classes: StyleClasses
+    xml: string
+} {
+    const classes: StyleClasses = new Map()
+    const rest = xml.replace(STYLE_DEFINITION, (_match, attrText: string) => {
+        const attrs = new Map(
+            readAttributes(attrText).map((a) => [a.name, a.value]),
+        )
+        // "name" may end in the ";" the model is used to; "style" is the
+        // attribute the model may reach for instead of "value"
+        const name = attrs.get("name")?.trim().replace(/;+$/, "")
+        const value = attrs.get("value") ?? attrs.get("style")
+        if (name && value !== undefined) {
+            // Without the trailing ";", so a name followed by ";" in a cell
+            // expands to "...;" and not to "...;;"
+            classes.set(name, escapeForAttribute(value).replace(/;+$/, ""))
+        }
+        return ""
+    })
+    // Two passes resolve names used by other definitions, in either order
+    for (let pass = 0; pass < 2; pass++) {
+        for (const [name, value] of classes) {
+            const others = new Map(classes)
+            others.delete(name)
+            classes.set(name, applyToStyle(value, others))
+        }
+    }
+    return { classes, xml: rest }
+}
+
+/**
+ * Rewrite the style of every mxCell. The callback returns the new style, or
+ * undefined to leave the cell alone. A cell without a style attribute gets
+ * one when the callback returns a style for it.
+ */
+function rewriteCellStyles(
+    xml: string,
+    rewrite: (
+        style: string | undefined,
+        attrs: Map<string, string>,
+    ) => string | undefined,
+): string {
+    return xml.replace(CELL_TAG, (tag, attrText: string, selfClose: string) => {
+        const attributes = readAttributes(attrText)
+        const attrs = new Map(attributes.map((a) => [a.name, a.value]))
+        const style = attributes.find((a) => a.name === "style")
+        const next = rewrite(style?.value, attrs)
+        if (next === undefined || next === style?.value) return tag
+        // The value is copied from attributes as written, so only a quote
+        // from a single-quoted source needs escaping
+        const written = `style="${next.replace(/"/g, "&quot;")}"`
+        if (!style) {
+            return `<mxCell${attrText} ${written}${selfClose}>`
+        }
+        // Keep the attribute where it was, with the whitespace before it
+        const space =
+            attrText.slice(style.start, style.end).match(/^\s*/)?.[0] ?? " "
+        return `<mxCell${attrText.slice(0, style.start)}${space}${written}${attrText.slice(style.end)}${selfClose}>`
+    })
+}
+
+/** Expand the names in every cell's style; the overrides after a name still win */
+export function applyStyleClasses(xml: string, classes: StyleClasses): string {
+    if (classes.size === 0) return xml
+    return rewriteCellStyles(xml, (style) =>
+        style === undefined ? undefined : applyToStyle(style, classes),
+    )
+}
+
+/** The ids of the edges in the XML, whose child vertices are edge labels */
+export function edgeIdsOf(xml: string): Set<string> {
+    const ids = new Set<string>()
+    for (const [, attrText] of xml.matchAll(CELL_TAG)) {
+        const attrs = new Map(
+            readAttributes(attrText).map((a) => [a.name, a.value]),
+        )
+        const id = attrs.get("id")
+        if (id && attrs.get("edge") === "1") ids.add(id)
+    }
+    return ids
+}
+
+/**
+ * Whether the label sits outside the shape, as with library icons (their
+ * styles position the label below) and images, so wrapping it to the
+ * shape's width would be wrong.
+ */
+function hasLabelOutside(style: string): boolean {
+    return (
+        hasKey(style, "verticalLabelPosition") ||
+        hasKey(style, "labelPosition") ||
+        hasKey(style, "image") ||
+        hasToken(style, "shape=image")
+    )
+}
+
+/**
+ * draw.io's own defaults for a new shape: html=1 (so labels may hold <br>
+ * and <b>) and whiteSpace=wrap. Wrapping is not added to shapes whose label
+ * sits outside (icons, images), to text that sizes itself (autosize=1), to
+ * edge labels (their label box has no width of its own) or next to html=0
+ * (draw.io renders a wrapping label as HTML). Edges get html=1. Root cells
+ * and cells that already set a key are left alone.
+ *
+ * An edit adds cells to a page the XML does not show, so the caller passes
+ * the ids of the edges already on it (edgeIdsOf), or new edge labels would
+ * be wrapped like shapes.
+ */
+export function addDefaultStyles(
+    xml: string,
+    knownEdgeIds: Iterable<string> = [],
+): string {
+    const edges = new Set([...knownEdgeIds, ...edgeIdsOf(xml)])
+    return rewriteCellStyles(xml, (style, attrs) => {
+        // A cell marked as both is drawn as an edge
+        const isEdge = attrs.get("edge") === "1"
+        const isVertex = attrs.get("vertex") === "1" && !isEdge
+        if (!isVertex && !isEdge) return undefined
+        const current = style ?? ""
+        const isEdgeLabel =
+            hasToken(current, "edgeLabel") ||
+            attrs.get("connectable") === "0" ||
+            edges.has(attrs.get("parent") ?? "")
+        const added: string[] = []
+        if (
+            isVertex &&
+            !hasKey(current, "whiteSpace") &&
+            !hasLabelOutside(current) &&
+            !isEdgeLabel &&
+            !hasToken(current, "autosize=1") &&
+            !hasToken(current, "html=0")
+        ) {
+            added.push("whiteSpace=wrap")
+        }
+        if (!hasKey(current, "html")) added.push("html=1")
+        if (added.length === 0) return undefined
+        const separator = current === "" || current.endsWith(";") ? "" : ";"
+        return `${current}${separator}${added.join(";")};`
+    })
+}
+
+/** Expand the named styles of a model's XML and add the default styles */
+export function expandStyles(xml: string): string {
+    const { classes, xml: cells } = readStyleClasses(xml)
+    return addDefaultStyles(applyStyleClasses(cells, classes))
+}
@@ -3,30 +3,16 @@
 * prompt and tool descriptions, so both teach the model the same thing.
 */

-export const SWIMLANE_EXAMPLE = `<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>`
+export const SWIMLANE_EXAMPLE = `<mxCell id="lane1" value="Frontend" style="swimlane;" x="40" y="40" w="200" h="200"/>
+<mxCell id="step1" value="Step 1" style="rounded=1;" parent="lane1" x="20" y="60" w="160" h="40"/>
+<mxCell id="lane2" value="Backend" style="swimlane;" x="280" y="40" w="200" h="200"/>
+<mxCell id="step2" value="Step 2" style="rounded=1;" parent="lane2" x="20" y="60" w="160" h="40"/>
+<mxCell id="edge1" style="edgeStyle=orthogonalEdgeStyle;" source="step1" target="step2"/>`

-export const TWO_EDGES_EXAMPLE = `<mxCell id="e1" value="A to B" style="edgeStyle=orthogonalEdgeStyle;exitX=1;exitY=0.3;entryX=0;entryY=0.3;endArrow=classic;" edge="1" parent="1" source="a" target="b">
-  <mxGeometry relative="1" as="geometry"/>
-</mxCell>
-<mxCell id="e2" value="B to A" style="edgeStyle=orthogonalEdgeStyle;exitX=0;exitY=0.7;entryX=1;entryY=0.7;endArrow=classic;" edge="1" parent="1" source="b" target="a">
-  <mxGeometry relative="1" as="geometry"/>
-</mxCell>`
+export const TWO_EDGES_EXAMPLE = `<mxCell id="e1" value="A to B" style="edgeStyle=orthogonalEdgeStyle;exitX=1;exitY=0.3;entryX=0;entryY=0.3;" source="a" target="b"/>
+<mxCell id="e2" value="B to A" style="edgeStyle=orthogonalEdgeStyle;exitX=0;exitY=0.7;entryX=1;entryY=0.7;" source="b" target="a"/>`

-export const WAYPOINT_EXAMPLE = `<mxCell id="hotfix_to_main" style="edgeStyle=orthogonalEdgeStyle;exitX=0.5;exitY=0;entryX=1;entryY=0.5;endArrow=classic;" edge="1" parent="1" source="hotfix" target="main">
+export const WAYPOINT_EXAMPLE = `<mxCell id="hotfix_to_main" style="edgeStyle=orthogonalEdgeStyle;exitX=0.5;exitY=0;entryX=1;entryY=0.5;" edge="1" parent="1" source="hotfix" target="main">
  <mxGeometry relative="1" as="geometry">
    <Array as="points">
      <mxPoint x="750" y="80"/>
@@ -35,6 +21,15 @@ export const WAYPOINT_EXAMPLE = `<mxCell id="hotfix_to_main" style="edgeStyle=or
  </mxGeometry>
 </mxCell>`

+/** Named styles defined once and used by name, like CSS classes */
+export const STYLE_CLASS_EXAMPLE = `<mxStyle name="step" value="fillColor=#dae8fc;strokeColor=#6c8ebf;"/>
+<mxStyle name="down" value="edgeStyle=orthogonalEdgeStyle;exitX=0.5;exitY=1;entryX=0.5;entryY=0;"/>
+<mxCell id="2" value="Start" style="rounded=1;step;" x="40" y="40" w="120" h="60"/>
+<mxCell id="3" value="Check" style="rhombus;step;fontStyle=1;" x="40" y="160" w="120" h="80"/>
+<mxCell id="4" value="Done" style="rounded=1;step;" x="40" y="300" w="120" h="60"/>
+<mxCell id="5" style="down;" source="2" target="3"/>
+<mxCell id="6" style="down;" source="3" target="4"/>`
+
 /** Indent every line, for an indented code block in Markdown */
 export const indent = (text: string, prefix = "    ") =>
    text
@@ -334,22 +334,25 @@ function checkEntityReferences(xml: string): string | null {

 /** Check for nested mxCell tags using regex */
 function checkNestedMxCells(xml: string): string | null {
-    const cellTagPattern = /<\/?mxCell[^>]*>/g
+    // Quoted values may hold ">", so the tag ends at the first ">" outside them
+    const cellTagPattern = /<\/?mxCell\b(?:[^<>"']|"[^"]*"|'[^']*')*>/g
    const cellStack: number[] = []
    let cellMatch
    while ((cellMatch = cellTagPattern.exec(xml)) !== null) {
        const tag = cellMatch[0]
+        const nested =
+            "Invalid XML: Found nested mxCell tags. Cells should be siblings, not nested inside other mxCell elements."
+        const isLabelOrGeometry =
+            /\sas\s*=\s*["'](valueLabel|geometry)["']/.test(tag)
        if (tag.startsWith("</mxCell>")) {
            if (cellStack.length > 0) cellStack.pop()
-        } else if (!tag.endsWith("/>")) {
-            const isLabelOrGeometry =
-                /\sas\s*=\s*["'](valueLabel|geometry)["']/.test(tag)
-            if (!isLabelOrGeometry) {
-                cellStack.push(cellMatch.index)
-                if (cellStack.length > 1) {
-                    return "Invalid XML: Found nested mxCell tags. Cells should be siblings, not nested inside other mxCell elements."
-                }
-            }
+        } else if (tag.endsWith("/>")) {
+            // A self-closing cell inside an open one is nested too (or the
+            // open one lacks its </mxCell>; the auto-fix sorts that out)
+            if (cellStack.length > 0 && !isLabelOrGeometry) return nested
+        } else if (!isLabelOrGeometry) {
+            cellStack.push(cellMatch.index)
+            if (cellStack.length > 1) return nested
        }
    }
    return null
@@ -556,6 +559,19 @@ export function validateMxCellStructure(
 * @param xml - The XML string to fix
 * @returns Object with fixed XML and list of fixes applied
 */
+/**
+ * A compact cell's last attribute is a number, and the model sometimes
+ * drops its closing quote: h="112/>. Only a cell whose earlier attributes
+ * are all properly quoted is touched, so a label that happens to contain
+ * such text is left alone.
+ */
+export function repairQuoteBeforeSlash(xml: string): string {
+    return xml.replace(
+        /<mxCell\b((?:\s+[\w:.-]+="[^"]*")*)(\s+(?:x|y|w|h|width|height)="-?\d+(?:\.\d+)?)\s*\/>/g,
+        '<mxCell$1$2"/>',
+    )
+}
+
 export function autoFixXml(xml: string): { fixed: string; fixes: string[] } {
    let fixed = xml
    const fixes: string[] = []
@@ -657,6 +673,29 @@ export function autoFixXml(xml: string): { fixed: string; fixes: string[] } {
        fixes.push("Fixed malformed attribute quotes")
    }

+    // 6b. Missing closing quote on the last attribute of a compact cell
+    // (h="112/>), see repairQuoteBeforeSlash
+    const quoted = repairQuoteBeforeSlash(fixed)
+    if (quoted !== fixed) {
+        fixed = quoted
+        fixes.push("Added a missing closing quote before />")
+    }
+
+    // 6c. A compact cell written without the slash: <mxCell ... h="60">
+    // followed by the next cell, a definition or the end. Only cells that
+    // carry a size or a connection, so an open container stays open.
+    const slashless =
+        /<mxCell\b((?:\s+[\w:.-]+="[^"]*")*)\s*>(?=\s*(?:<mxCell\b|<mxStyle\b|$))/g
+    const closed = fixed.replace(slashless, (tag, attrText: string) =>
+        /\s(?:x|y|w|h|width|height|source|target)="/.test(attrText)
+            ? `<mxCell${attrText}/>`
+            : tag,
+    )
+    if (closed !== fixed) {
+        fixed = closed
+        fixes.push("Closed compact cells written without the slash")
+    }
+
    // 7. Fix malformed closing tags
    const malformedClosingTag = /<\/([a-zA-Z][a-zA-Z0-9]*)\s*\/>/g
    if (malformedClosingTag.test(fixed)) {
@@ -987,16 +1026,39 @@ export function autoFixXml(xml: string): { fixed: string; fixes: string[] } {
            /<mxCell\s/.test(trimmed) &&
            !trimmed.endsWith("/>") &&
            !trimmed.endsWith("</mxCell>")
+        // A self-closing (compact) cell is the next sibling too
+        const isSelfClosingCell =
+            /<mxCell\s/.test(trimmed) && trimmed.endsWith("/>")
        const isCloseCell = trimmed === "</mxCell>"
+        // The last cell's closing tag may share its line with the wrapper's
+        const startsWithClose = !isCloseCell && trimmed.startsWith("</mxCell>")

-        if (isOpenCell) {
+        if (isOpenCell || isSelfClosingCell) {
            if (cellDepth > 0) {
                const indent = line.match(/^(\s*)/)?.[1] || ""
                newLines.push(indent + "</mxCell>")
                trueNestedFixed++
-                pendingCloseRemoval++
+                // The open cell's own </mxCell> is removed later, when there
+                // is one before the next open cell; a cell that simply lacks
+                // its closing tag has none to remove
+                const nextOpen = lines2.findIndex(
+                    (l, j) =>
+                        j > i &&
+                        /<mxCell\s/.test(l.trim()) &&
+                        !l.trim().endsWith("/>"),
+                )
+                const nextClose = lines2.findIndex(
+                    (l, j) => j > i && l.trim().startsWith("</mxCell>"),
+                )
+                if (
+                    isOpenCell ||
+                    (nextClose !== -1 &&
+                        (nextOpen === -1 || nextClose < nextOpen))
+                ) {
+                    pendingCloseRemoval++
+                }
            }
-            cellDepth = 1
+            cellDepth = isOpenCell ? 1 : 0
            newLines.push(line)
        } else if (isCloseCell) {
            if (pendingCloseRemoval > 0) {
@@ -1005,6 +1067,9 @@ export function autoFixXml(xml: string): { fixed: string; fixes: string[] } {
                cellDepth = Math.max(0, cellDepth - 1)
                newLines.push(line)
            }
+        } else if (startsWithClose && pendingCloseRemoval > 0) {
+            pendingCloseRemoval--
+            newLines.push(line.replace("</mxCell>", ""))
        } else {
            newLines.push(line)
        }
@@ -10,6 +10,8 @@ export interface DiagramVersion {
    number: number
    /** Full multi-page document after the change */
    xml: string
+    /** The page the change was made on; older sessions have none (the first page) */
+    pageId?: string
    /** Diagram before the change; kept only on the latest version */
    beforeXml?: string
    /** SVG data URL thumbnail; "" when none could be made */
@@ -131,7 +131,7 @@ const NEW_CELLS =
    cell("3", "R&D", 400) +
    `<UserObject id="4" label="Docs" link="https://example.com"><mxCell style="rounded=1;" vertex="1" parent="1"><mxGeometry x="580" y="40" width="120" height="60" as="geometry"/></mxCell></UserObject>`

-test("display_diagram replaces the document with the fixed diagram", async ({
+test("display_diagram redraws the page on screen and keeps the other pages", async ({
    page: p,
 }) => {
    const canvas = await mockReplies(p, [
@@ -155,9 +155,11 @@ test("display_diagram replaces the document with the fixed diagram", async ({
            timeout: 15000,
        })
    }
-    // The old pages are gone
+    // The first page was redrawn; the second page is still there
    await expect(canvas.getByText("Old A")).toHaveCount(0)
-    await expect(pageTabs.getByText("Second", { exact: true })).toHaveCount(0)
+    await expect(pageTabs.getByText("Second", { exact: true })).toBeVisible()
+    await pageTabs.getByText("Second", { exact: true }).click()
+    await expect(canvas.getByText("Old B")).toBeVisible()
 })

 test("an edit with a fixable cell is fixed, not rejected", async ({
@@ -1001,7 +1001,7 @@ test.describe("Workspace", () => {
        await expect(canvas.getByText("Old A")).toBeVisible()
        await sendMessage(page, "Create a flowchart")
        await waitForComplete(page)
-        // Multi-page documents are loaded in full: the card is the way back
+        // The card is one way back
        await page.waitForTimeout(2000)
        await page.locator('[data-testid="version-undo"]').click()
        await expect(canvas.getByText("Old A")).toBeVisible()
@@ -1533,7 +1533,7 @@ test.describe("Workspace", () => {
        await expect.poll(savedPageId, { timeout: 10000 }).toBe("orig")
    })

-    test("Ctrl+Z after an AI drawing gives the page its id back", async ({
+    test("an AI drawing keeps the page's id, for links to the page", async ({
        page,
    }) => {
        await page.route("**/api/chat", drawThenEdit())
@@ -1567,7 +1567,7 @@ test.describe("Workspace", () => {
                    .querySelector("diagram")
                    ?.getAttribute("id")
            })
-        await expect.poll(savedPageId, { timeout: 10000 }).toBe("page-1")
+        await expect.poll(savedPageId, { timeout: 10000 }).toBe("orig")
        await canvas
            .locator(".geDiagramContainer")
            .click({ position: { x: 10, y: 10 } })
@@ -1576,7 +1576,62 @@ test.describe("Workspace", () => {
        await expect.poll(savedPageId, { timeout: 10000 }).toBe("orig")
        await page.keyboard.press("ControlOrMeta+Shift+z")
        await expect(canvas.getByText("Process", { exact: true })).toBeVisible()
-        await expect.poll(savedPageId, { timeout: 10000 }).toBe("page-1")
+        await expect.poll(savedPageId, { timeout: 10000 }).toBe("orig")
+    })
+
+    test("the AI reads and draws the page the user is viewing", async ({
+        page,
+    }) => {
+        const bodies: any[] = []
+        await page.route(
+            "**/api/chat",
+            drawThenEdit((body) => bodies.push(body)),
+        )
+        await openApp(page)
+        await openDrawioFile(page, "two.drawio", TWO_PAGE_FILE)
+        const canvas = getIframeContent(page)
+        await expect(canvas.getByText("Old A")).toBeVisible()
+        // The second page, through draw.io's own tabs
+        await drawioTabs(page).getByText("P1", { exact: true }).click()
+        await expect(canvas.getByText("Old B")).toBeVisible()
+        await sendMessage(page, "Create a flowchart")
+        await waitForComplete(page)
+        // The model got the page on screen
+        expect(bodies[0].xml).toContain("Old B")
+        expect(bodies[0].xml).not.toContain("Old A")
+        // Its drawing replaced that page, and only that page
+        await expect(canvas.getByText("Process", { exact: true })).toBeVisible()
+        await expect(canvas.getByText("Old B")).toHaveCount(0)
+        const pagesIn = (xml: string) =>
+            Object.fromEntries(
+                Array.from(
+                    xml.matchAll(
+                        /<diagram[^>]*\bid="([^"]+)"[^>]*>([\s\S]*?)<\/diagram>/g,
+                    ),
+                    (m) => [m[1], m[2]],
+                ),
+            )
+        await expect
+            .poll(
+                async () => {
+                    const pages = pagesIn(await savedDiagram(page))
+                    return {
+                        p0: pages.p0?.includes("Old A"),
+                        p1: pages.p1?.includes("Process"),
+                        oldB: pages.p1?.includes("Old B"),
+                    }
+                },
+                { timeout: 10000 },
+            )
+            .toEqual({ p0: true, p1: true, oldB: false })
+        // One undo step takes the drawing back, as on a one-page file
+        await canvas
+            .locator(".geDiagramContainer")
+            .click({ position: { x: 10, y: 10 } })
+        await page.keyboard.press("ControlOrMeta+z")
+        await expect(canvas.getByText("Old B")).toBeVisible()
+        await drawioTabs(page).getByText("P0", { exact: true }).click()
+        await expect(canvas.getByText("Old A")).toBeVisible()
    })

    test("page settings the AI writes in single quotes are applied too", async ({
@@ -0,0 +1,370 @@
+import { describe, expect, it } from "vitest"
+import { extractCompleteMxCells, isMxCellXmlComplete } from "@/lib/utils"
+import {
+    expandCompactCells,
+    foldCells,
+} from "@/packages/mcp-server/src/compact-cells.ts"
+import { editDiagram } from "@/packages/mcp-server/src/edit-diagram.ts"
+import { prepareNewDiagram } from "@/packages/mcp-server/src/new-diagram.ts"
+import {
+    normalizeToMxfile,
+    wrapCellsInModel,
+} from "@/packages/mcp-server/src/pages.ts"
+
+const shape =
+    '<mxCell id="2" value="Start" style="rounded=1;" x="40" y="40" w="120" h="60"/>'
+const shapeLong =
+    '<mxCell id="2" value="Start" style="rounded=1;" vertex="1" parent="1"><mxGeometry x="40" y="40" width="120" height="60" as="geometry"/></mxCell>'
+const edge = '<mxCell id="5" style="down;" source="2" target="3"/>'
+const edgeLong =
+    '<mxCell id="5" style="down;" edge="1" parent="1" source="2" target="3"><mxGeometry relative="1" as="geometry"/></mxCell>'
+
+/** Cells compared by what they mean, not by attribute order */
+function canonical(xml: string): string {
+    const doc = new DOMParser().parseFromString(
+        `<root>${xml}</root>`,
+        "text/xml",
+    )
+    const describe = (el: Element): string => {
+        const attrs = Array.from(el.attributes)
+            .map((a) => `${a.name}=${a.value}`)
+            .sort()
+            .join(" ")
+        const children = Array.from(el.children).map(describe).join("")
+        return `<${el.tagName} ${attrs}>${children}</${el.tagName}>`
+    }
+    return Array.from(doc.documentElement.children).map(describe).join("\n")
+}
+
+describe("expandCompactCells", () => {
+    it("gives a compact shape its flags, parent and geometry", () => {
+        expect(expandCompactCells(shape)).toBe(shapeLong)
+    })
+
+    it("gives a compact edge its flags, parent and relative geometry", () => {
+        expect(expandCompactCells(edge)).toBe(edgeLong)
+    })
+
+    it("keeps an explicit parent and accepts width/height as names", () => {
+        const inLane =
+            '<mxCell id="3" value="Step" style="rounded=1;" parent="lane1" x="20" y="60" width="160" height="40"/>'
+        expect(expandCompactCells(inLane)).toBe(
+            '<mxCell id="3" value="Step" style="rounded=1;" vertex="1" parent="lane1"><mxGeometry x="20" y="60" width="160" height="40" as="geometry"/></mxCell>',
+        )
+    })
+
+    it("fills in a default position and size when some are missing", () => {
+        expect(expandCompactCells('<mxCell id="2" value="A" w="100"/>')).toBe(
+            '<mxCell id="2" value="A" vertex="1" parent="1"><mxGeometry x="0" y="0" width="100" height="60" as="geometry"/></mxCell>',
+        )
+    })
+
+    it("lets an explicit geometry win over compact attributes", () => {
+        // The stray attributes stay as written; the geometry is the one used
+        const both =
+            '<mxCell id="2" x="1" y="1" w="1" h="1"><mxGeometry x="40" y="40" width="120" height="60" as="geometry"/></mxCell>'
+        expect(expandCompactCells(both)).toBe(
+            '<mxCell id="2" x="1" y="1" w="1" h="1" vertex="1" parent="1"><mxGeometry x="40" y="40" width="120" height="60" as="geometry"/></mxCell>',
+        )
+    })
+
+    it("adds the relative geometry to a long-form edge that has none", () => {
+        const noGeometry =
+            '<mxCell id="5" style="down;" edge="1" parent="1" source="2" target="3"/>'
+        expect(expandCompactCells(noGeometry)).toBe(edgeLong)
+    })
+
+    it("leaves root cells, long-form cells and edge labels alone", () => {
+        const roots = '<mxCell id="0"/><mxCell id="1" parent="0"/>'
+        const label =
+            '<mxCell id="9" value="yes" style="edgeLabel;" vertex="1" connectable="0" parent="5"><mxGeometry x="-0.5" relative="1" as="geometry"/></mxCell>'
+        expect(expandCompactCells(roots + shapeLong + edgeLong + label)).toBe(
+            roots + shapeLong + edgeLong + label,
+        )
+    })
+
+    it("works on a cell inside a UserObject wrapper", () => {
+        const wrapped =
+            '<UserObject id="4" label="Docs" link="https://example.com"><mxCell style="rounded=1;" x="580" y="40" w="120" h="60"/></UserObject>'
+        expect(expandCompactCells(wrapped)).toBe(
+            '<UserObject id="4" label="Docs" link="https://example.com"><mxCell style="rounded=1;" vertex="1" parent="1"><mxGeometry x="580" y="40" width="120" height="60" as="geometry"/></mxCell></UserObject>',
+        )
+    })
+})
+
+describe("foldCells", () => {
+    it("writes plain shapes and edges compactly", () => {
+        expect(foldCells(shapeLong)).toBe(shape)
+        expect(foldCells(edgeLong)).toBe(edge)
+    })
+
+    it("keeps a parent other than 1 and leaves special cells as written", () => {
+        const inLane =
+            '<mxCell id="3" value="Step" style="rounded=1;" vertex="1" parent="lane1"><mxGeometry x="20" y="60" width="160" height="40" as="geometry"/></mxCell>'
+        expect(foldCells(inLane)).toBe(
+            '<mxCell id="3" value="Step" style="rounded=1;" parent="lane1" x="20" y="60" w="160" h="40"/>',
+        )
+        const waypoints =
+            '<mxCell id="6" edge="1" parent="1" source="2" target="3"><mxGeometry relative="1" as="geometry"><Array as="points"><mxPoint x="750" y="80"/></Array></mxGeometry></mxCell>'
+        const label =
+            '<mxCell id="9" value="yes" style="edgeLabel;" vertex="1" connectable="0" parent="5"><mxGeometry x="-0.5" relative="1" as="geometry"/></mxCell>'
+        const sourcePoint =
+            '<mxCell id="7" edge="1" parent="1" target="3"><mxGeometry relative="1" as="geometry"><mxPoint x="10" y="10" as="sourcePoint"/></mxGeometry></mxCell>'
+        const roots = '<mxCell id="0"/><mxCell id="1" parent="0"/>'
+        const wrongAs =
+            '<mxCell id="8" vertex="1" parent="1"><mxGeometry x="1" y="1" width="2" height="2" as="33"/></mxCell>'
+        for (const xml of [waypoints, label, sourcePoint, roots, wrongAs]) {
+            expect(foldCells(xml)).toBe(xml)
+        }
+    })
+
+    it("round-trips through expandCompactCells", () => {
+        const page = `<mxGraphModel><root><mxCell id="0"/><mxCell id="1" parent="0"/>${shapeLong}${edgeLong}<mxCell id="lane1" value="Lane" style="swimlane;" vertex="1" parent="1"><mxGeometry x="40" y="40" width="200" height="200" as="geometry"/></mxCell><mxCell id="3" value="Step" style="rounded=1;" vertex="1" parent="lane1"><mxGeometry x="20" y="60" width="160" height="40" as="geometry"/></mxCell><mxCell id="6" edge="1" parent="1" source="2" target="3"><mxGeometry relative="1" as="geometry"><Array as="points"><mxPoint x="750" y="80"/></Array></mxGeometry></mxCell></root></mxGraphModel>`
+        const folded = foldCells(page)
+        expect(folded).not.toContain("vertex=")
+        expect(canonical(expandCompactCells(folded))).toBe(canonical(page))
+    })
+})
+
+describe("compact cells through the pipeline", () => {
+    const geometryOf = (xml: string, id: string) =>
+        xml.match(
+            new RegExp(`<mxCell id="${id}"[^>]*>(<mxGeometry[^>]*/>)`),
+        )?.[1]
+
+    it("prepareNewDiagram expands them and still adds the defaults", () => {
+        const prepared = prepareNewDiagram(`${shape}\n${edge}`)
+        expect(prepared.ok).toBe(true)
+        if (!prepared.ok) return
+        expect(prepared.xml).toContain(
+            'style="rounded=1;whiteSpace=wrap;html=1;" vertex="1" parent="1"',
+        )
+        expect(geometryOf(prepared.xml, "2")).toBe(
+            '<mxGeometry x="40" y="40" width="120" height="60" as="geometry"/>',
+        )
+        expect(prepared.xml).toContain(
+            '<mxCell id="5" style="down;html=1;" edge="1" parent="1" source="2" target="3"><mxGeometry relative="1" as="geometry"/></mxCell>',
+        )
+    })
+
+    it("editDiagram accepts a compact cell in new_xml", () => {
+        const file =
+            normalizeToMxfile(wrapCellsInModel(shapeLong), {
+                pageId: "p1",
+                pageName: "Page-1",
+            }) ?? ""
+        const outcome = editDiagram(
+            file,
+            [
+                {
+                    operation: "add",
+                    cell_id: "3",
+                    new_xml:
+                        '<mxCell id="3" value="Next" style="rounded=1;" x="200" y="40" w="120" h="60"/>',
+                },
+                {
+                    operation: "update",
+                    cell_id: "2",
+                    new_xml:
+                        '<mxCell id="2" value="Begin" style="rounded=1;" x="40" y="40" w="120" h="60"/>',
+                },
+            ],
+            {},
+        )
+        expect(outcome.ok).toBe(true)
+        if (!outcome.ok) return
+        expect(outcome.xml).toContain('value="Next"')
+        expect(outcome.xml).toContain('value="Begin"')
+        expect(geometryOf(outcome.xml, "3")).toBe(
+            '<mxGeometry x="200" y="40" width="120" height="60" as="geometry"/>',
+        )
+    })
+})
+
+describe("a compact cell with a slip", () => {
+    it("repairs a missing closing quote before the slash", () => {
+        const prepared = prepareNewDiagram(
+            '<mxCell id="12" value="Coin Flip" style="rounded=1;" x="535" y="276" w="225" h="112/>',
+        )
+        expect(prepared.ok).toBe(true)
+        if (!prepared.ok) return
+        expect(prepared.xml).toContain(
+            '<mxGeometry x="535" y="276" width="225" height="112" as="geometry"/>',
+        )
+    })
+})
+
+describe("review round: cells the model may write", () => {
+    it("escapes a double quote from a single-quoted value", () => {
+        const out = expandCompactCells(
+            `<mxCell id='2' value='Say "hi"' x='1' y='2' w='3' h='4'/>`,
+        )
+        expect(out).toContain('value="Say &quot;hi&quot;"')
+        const prepared = prepareNewDiagram(
+            `<mxCell id='2' value='a" visible="0' x="1" y="2" w="3" h="4"/>`,
+        )
+        expect(prepared.ok).toBe(true)
+        if (!prepared.ok) return
+        expect(prepared.xml).toContain('value="a&quot; visible=&quot;0"')
+        expect(prepared.xml).not.toContain(' visible="0"')
+        const folded = foldCells(
+            `<mxCell id="2" value='Say "hi"' vertex="1" parent="1"><mxGeometry x="1" y="2" width="3" height="4" as="geometry"/></mxCell>`,
+        )
+        expect(folded).toBe(
+            '<mxCell id="2" value="Say &quot;hi&quot;" x="1" y="2" w="3" h="4"/>',
+        )
+    })
+
+    it("accepts labels with > in compact self-closing cells", () => {
+        const prepared = prepareNewDiagram(
+            `<mxCell id="2" value="x > 5" style="rounded=1;" x="40" y="40" w="120" h="60"/>
+<mxCell id="3" value="A -> B" style="rounded=1;" x="40" y="200" w="120" h="60"/>
+<mxCell id="5" source="2" target="3"/>`,
+        )
+        expect(prepared.ok).toBe(true)
+        expect(
+            isMxCellXmlComplete(
+                '<mxCell id="2" value="A > B" x="0" y="0" w="120" h="60"/>',
+            ),
+        ).toBe(true)
+        expect(
+            extractCompleteMxCells(
+                '<mxCell id="2" value="A > B" x="0" y="0" w="120" h="60"/>\n<mxCell id="3" value="C" x="0" y="0" w="1',
+            ),
+        ).toBe('<mxCell id="2" value="A > B" x="0" y="0" w="120" h="60"/>')
+    })
+
+    it("infers a vertex for an edge label with a geometry and an edge for a connection with a size", () => {
+        const label =
+            '<mxCell id="9" value="yes" style="edgeLabel;" parent="5" connectable="0"><mxGeometry x="-0.5" relative="1" as="geometry"/></mxCell>'
+        expect(expandCompactCells(label)).toBe(
+            '<mxCell id="9" value="yes" style="edgeLabel;" connectable="0" vertex="1" parent="5"><mxGeometry x="-0.5" relative="1" as="geometry"/></mxCell>',
+        )
+        expect(
+            expandCompactCells(
+                '<mxCell id="e" source="2" target="3" x="0" y="0"/>',
+            ),
+        ).toBe(
+            '<mxCell id="e" edge="1" parent="1" source="2" target="3"><mxGeometry relative="1" as="geometry"/></mxCell>',
+        )
+        // A dangling edge has only one end
+        expect(
+            expandCompactCells('<mxCell id="e" style="a;" source="2"/>'),
+        ).toBe(
+            '<mxCell id="e" style="a;" edge="1" parent="1" source="2"><mxGeometry relative="1" as="geometry"/></mxCell>',
+        )
+    })
+
+    it("does not take a geometry inside custom data for the cell's own", () => {
+        const out = expandCompactCells(
+            '<mxCell id="2" x="10" y="20" w="120" h="60"><Object as="payload"><mxGeometry as="backup"/></Object></mxCell>',
+        )
+        expect(out).toBe(
+            '<mxCell id="2" vertex="1" parent="1"><mxGeometry x="10" y="20" width="120" height="60" as="geometry"/><Object as="payload"><mxGeometry as="backup"/></Object></mxCell>',
+        )
+    })
+
+    it("keeps stray size attributes when the cell has its own geometry", () => {
+        const xml =
+            '<mxCell id="2" x="99" vertex="1" parent="1"><mxGeometry x="1" y="2" width="3" height="4" as="geometry"/></mxCell>'
+        expect(expandCompactCells(xml)).toBe(xml)
+        expect(foldCells(xml)).toBe(xml)
+    })
+
+    it("ignores prototype names and folds only cells that name their parent", () => {
+        expect(expandCompactCells('<mxCell id="2" toString="x"/>')).toBe(
+            '<mxCell id="2" toString="x"/>',
+        )
+        const noParent =
+            '<mxCell id="2" vertex="1"><mxGeometry x="1" y="2" width="3" height="4" as="geometry"/></mxCell>'
+        expect(foldCells(noParent)).toBe(noParent)
+    })
+
+    it("puts a compact cell on the page's first layer when editing", () => {
+        const file = `<mxfile><diagram id="p1" name="Page-1"><mxGraphModel><root><mxCell id="0"/><mxCell id="L1" parent="0"/>${shapeLong.replace('parent="1"', 'parent="L1"')}</root></mxGraphModel></diagram></mxfile>`
+        const outcome = editDiagram(
+            file,
+            [
+                {
+                    operation: "add",
+                    cell_id: "3",
+                    new_xml:
+                        '<mxCell id="3" value="B" x="1" y="2" w="3" h="4"/>',
+                },
+            ],
+            {},
+        )
+        expect(outcome.ok).toBe(true)
+        if (!outcome.ok) return
+        expect(outcome.xml).toContain(
+            '<mxCell id="3" value="B" vertex="1" parent="L1"',
+        )
+        expect(foldCells(file, "L1")).toContain(
+            '<mxCell id="2" value="Start" style="rounded=1;" x="40" y="40" w="120" h="60"/>',
+        )
+    })
+
+    it("refuses a compact shape with a root cell id instead of dropping it", () => {
+        const prepared = prepareNewDiagram(
+            '<mxCell id="1" value="A" x="0" y="0" w="10" h="10"/>',
+        )
+        expect(prepared.ok).toBe(false)
+        if (!prepared.ok) expect(prepared.error).toContain("root cells")
+    })
+
+    it("repairs the quote slip only on a cell's last numeric attribute", () => {
+        expect(
+            isMxCellXmlComplete('<mxCell id="2" x="1" y="2" w="3" h="4/>'),
+        ).toBe(true)
+        const prepared = prepareNewDiagram(
+            '<mxCell id="2" value="5/>" x="1" y="2" w="3" h="4"/>',
+        )
+        expect(prepared.ok).toBe(true)
+        if (!prepared.ok) return
+        expect(prepared.xml).toContain('value="5/>"')
+        expect(prepared.xml).toContain(
+            '<mxGeometry x="1" y="2" width="3" height="4" as="geometry"/>',
+        )
+    })
+
+    it("closes a compact cell written without the slash", () => {
+        const prepared = prepareNewDiagram(
+            '<mxCell id="2" value="A" x="1" y="2" w="3" h="4">\n<mxCell id="3" value="B" x="1" y="2" w="3" h="4"/>',
+        )
+        expect(prepared.ok).toBe(true)
+        if (!prepared.ok) return
+        expect(prepared.xml).toContain('value="A"')
+        expect(prepared.xml).toContain('value="B"')
+        expect(prepared.fixes.join()).toContain("without the slash")
+    })
+})
+
+describe("a long-form cell missing its closing tag next to compact cells", () => {
+    it("is closed before the compact cell that follows", () => {
+        const prepared = prepareNewDiagram(
+            `<mxCell id="2" value="A" x="0" y="0" w="80" h="40"/>
+<mxCell id="4" edge="1" parent="1" source="2" target="5">
+  <mxGeometry relative="1" as="geometry"><Array as="points"><mxPoint x="300" y="150"/></Array></mxGeometry>
+<mxCell id="5" value="C" x="400" y="0" w="80" h="40"/>`,
+        )
+        expect(prepared.ok).toBe(true)
+        if (!prepared.ok) return
+        expect(prepared.xml).toContain('<mxPoint x="300" y="150"/>')
+        expect(prepared.xml).toContain('value="C"')
+        expect((prepared.xml.match(/<mxCell\b/g) || []).length).toBe(5)
+    })
+
+    it("still flattens a compact cell nested inside an open cell", () => {
+        const prepared = prepareNewDiagram(
+            `<mxCell id="2" value="A" vertex="1" parent="1">
+  <mxGeometry x="0" y="0" width="80" height="40" as="geometry"/>
+  <mxCell id="3" value="B" x="100" y="0" w="80" h="40"/>
+</mxCell>`,
+        )
+        expect(prepared.ok).toBe(true)
+        if (!prepared.ok) return
+        expect(prepared.xml).toContain('value="A"')
+        expect(prepared.xml).toContain('value="B"')
+        expect((prepared.xml.match(/<mxCell\b/g) || []).length).toBe(4)
+    })
+})
@@ -153,9 +153,19 @@ describe("diffDiagrams", () => {
        expect(touchedIds).toEqual(["u1"])
    })

-    it("only looks at the first page", () => {
+    it("looks at the first page unless told which page", () => {
        const twoPages = file(pageOf("p1", box("a")), pageOf("p2", box("z")))
        expect(diffDiagrams("", twoPages).summary.shapesAdded).toBe(1)
+        const changedP2 = file(
+            pageOf("p1", box("a")),
+            pageOf("p2", box("z") + box("y")),
+        )
+        expect(diffDiagrams(twoPages, changedP2, "p2").touchedIds).toEqual([
+            "y",
+        ])
+        expect(diffDiagrams(twoPages, changedP2, "p1").touchedIds).toEqual([])
+        // An unknown page is the first one
+        expect(diffDiagrams(twoPages, changedP2, "p9").touchedIds).toEqual([])
    })

    it("reads compressed pages", () => {
@@ -0,0 +1,125 @@
+import pako from "pako"
+import { describe, expect, it } from "vitest"
+import {
+    pageModelXml,
+    pageSelectorFor,
+    placeOnPage,
+    replacePageModel,
+} from "@/lib/diagram-pages"
+
+const box = (id: string) =>
+    `<mxCell id="${id}" value="${id}" vertex="1" parent="1"><mxGeometry x="0" y="0" width="80" height="40" as="geometry"/></mxCell>`
+const model = (cells: string) =>
+    `<mxGraphModel><root><mxCell id="0"/><mxCell id="1" parent="0"/>${cells}</root></mxGraphModel>`
+const page = (id: string, cells: string) =>
+    `<diagram id="${id}" name="Page ${id}">${model(cells)}</diagram>`
+const packedPage = (id: string, cells: string) => {
+    const packed = Buffer.from(
+        pako.deflateRaw(encodeURIComponent(model(cells))),
+    ).toString("base64")
+    return `<diagram id="${id}" name="Page ${id}">${packed}</diagram>`
+}
+const TWO_PAGES = `<mxfile vars="{&quot;x&quot;:&quot;1&quot;}">${page("a", box("A"))}${page("b", box("B"))}</mxfile>`
+
+const pagesOf = (xml: string) =>
+    Array.from(
+        new DOMParser()
+            .parseFromString(xml, "text/xml")
+            .getElementsByTagName("diagram"),
+    ).map((d) => ({
+        id: d.getAttribute("id"),
+        name: d.getAttribute("name"),
+        cells: Array.from(d.getElementsByTagName("mxCell"))
+            .map((c) => c.getAttribute("id"))
+            .filter((id) => id !== "0" && id !== "1"),
+    }))
+
+describe("pageModelXml", () => {
+    it("gives the page with the id, and the first page without one", () => {
+        expect(pageModelXml(TWO_PAGES, "b")).toContain('id="B"')
+        expect(pageModelXml(TWO_PAGES, "b")).not.toContain('id="A"')
+        expect(pageModelXml(TWO_PAGES, null)).toContain('id="A"')
+        expect(pageModelXml(TWO_PAGES, "missing")).toContain('id="A"')
+    })
+
+    it("inflates a compressed page and passes a bare model through", () => {
+        const file = `<mxfile>${page("a", box("A"))}${packedPage("b", box("B"))}</mxfile>`
+        expect(pageModelXml(file, "b")).toContain('id="B"')
+        expect(pageModelXml(model(box("Z")), "b")).toBe(model(box("Z")))
+        expect(pageModelXml("<broken", "a")).toBeNull()
+    })
+})
+
+describe("pageSelectorFor", () => {
+    it("selects the page only when the document has it", () => {
+        expect(pageSelectorFor(TWO_PAGES, "b")).toEqual({ page_id: "b" })
+        expect(pageSelectorFor(TWO_PAGES, "missing")).toEqual({})
+        expect(pageSelectorFor(TWO_PAGES, null)).toEqual({})
+        expect(pageSelectorFor(model(box("Z")), "b")).toEqual({})
+    })
+})
+
+describe("replacePageModel", () => {
+    it("replaces one page and keeps the others, the names and the variables", () => {
+        const result = replacePageModel(TWO_PAGES, "b", model(box("N")))
+        expect(pagesOf(result)).toEqual([
+            { id: "a", name: "Page a", cells: ["A"] },
+            { id: "b", name: "Page b", cells: ["N"] },
+        ])
+        expect(result).toContain('vars="{&quot;x&quot;:&quot;1&quot;}"')
+    })
+
+    it("falls back to the first page for an unknown or missing id", () => {
+        for (const id of ["missing", null]) {
+            const result = replacePageModel(TWO_PAGES, id, model(box("N")))
+            expect(pagesOf(result).map((p) => p.cells)).toEqual([["N"], ["B"]])
+        }
+    })
+
+    it("starts from the blank file when there is no document", () => {
+        for (const base of ["", "<mxGraphModel/>", "<broken"]) {
+            const result = replacePageModel(base, "any", model(box("N")))
+            expect(pagesOf(result)).toEqual([
+                { id: "page-1", name: "Page-1", cells: ["N"] },
+            ])
+        }
+    })
+
+    it("refuses anything but a model", () => {
+        expect(() => replacePageModel(TWO_PAGES, "a", "<root/>")).toThrow()
+    })
+})
+
+describe("placeOnPage", () => {
+    it("puts one page's worth of drawing on the model's page", () => {
+        const drawn = `<mxfile><diagram id="page-1" name="Page-1">${model(box("N"))}</diagram></mxfile>`
+        const result = placeOnPage(drawn, TWO_PAGES, "b")
+        expect(pagesOf(result)).toEqual([
+            { id: "a", name: "Page a", cells: ["A"] },
+            { id: "b", name: "Page b", cells: ["N"] },
+        ])
+    })
+
+    it("applies the drawn file's variables, and keeps the canvas's otherwise", () => {
+        const withVars = `<mxfile vars="{&quot;team&quot;:&quot;New&quot;}"><diagram id="p" name="P">${model(box("N"))}</diagram></mxfile>`
+        expect(placeOnPage(withVars, TWO_PAGES, "b")).toContain(
+            'vars="{&quot;team&quot;:&quot;New&quot;}"',
+        )
+        const without = `<mxfile><diagram id="p" name="P">${model(box("N"))}</diagram></mxfile>`
+        expect(placeOnPage(without, TWO_PAGES, "b")).toContain(
+            'vars="{&quot;x&quot;:&quot;1&quot;}"',
+        )
+    })
+
+    it("lets a drawing with several pages replace the document", () => {
+        const drawn = `<mxfile>${page("x", box("X"))}${page("y", box("Y"))}</mxfile>`
+        expect(placeOnPage(drawn, TWO_PAGES, "b")).toBe(drawn)
+    })
+
+    it("draws on the blank file when the canvas is empty", () => {
+        const drawn = `<mxfile><diagram id="page-1" name="Page-1">${model(box("N"))}</diagram></mxfile>`
+        expect(pagesOf(placeOnPage(drawn, "", null))).toEqual([
+            { id: "page-1", name: "Page-1", cells: ["N"] },
+        ])
+    })
+})
@@ -263,3 +263,50 @@ describe("applyDiagramOperations with wrapped cells", () => {
        expect(errors[0]?.message).toContain("not found")
    })
 })
+
+describe("edit_diagram on one page of a multi-page file", () => {
+    // Page A has an edge "g"; on page B, "g" is a shape on layer "L"
+    const twoPages = `<mxfile><diagram id="pa" name="A"><mxGraphModel><root><mxCell id="0"/><mxCell id="1" parent="0"/>${box("s")}${box("t")}<mxCell id="g" edge="1" parent="1" source="s" target="t"><mxGeometry relative="1" as="geometry"/></mxCell></root></mxGraphModel></diagram><diagram id="pb" name="B"><mxGraphModel><root><mxCell id="0"/><mxCell id="L" parent="0"/>${box("g", "L")}</root></mxGraphModel></diagram></mxfile>`
+    const cellOn = (xml: string, pageId: string, id: string) =>
+        new DOMParser()
+            .parseFromString(xml, "text/xml")
+            .querySelector(`diagram[id="${pageId}"] mxCell[id="${id}"]`)
+
+    it("puts a compact cell without a parent on that page's layer", () => {
+        const outcome = editDiagram(
+            twoPages,
+            [
+                {
+                    operation: "add",
+                    cell_id: "c",
+                    new_xml:
+                        '<mxCell id="c" value="c" x="10" y="10" w="80" h="40"/>',
+                },
+            ],
+            { page_id: "pb" },
+        )
+        if (!outcome.ok) throw new Error(outcome.errors.join("; "))
+        expect(cellOn(outcome.xml, "pb", "c")?.getAttribute("parent")).toBe("L")
+        expect(cellOn(outcome.xml, "pa", "c")).toBeNull()
+    })
+
+    it("reads the edges of that page only", () => {
+        // A shape inside the group "g" is no edge label on page B
+        const outcome = editDiagram(
+            twoPages,
+            [
+                {
+                    operation: "add",
+                    cell_id: "c",
+                    new_xml:
+                        '<mxCell id="c" value="c" parent="g" x="10" y="10" w="80" h="40"/>',
+                },
+            ],
+            { page_id: "pb" },
+        )
+        if (!outcome.ok) throw new Error(outcome.errors.join("; "))
+        expect(cellOn(outcome.xml, "pb", "c")?.getAttribute("style")).toContain(
+            "whiteSpace=wrap",
+        )
+    })
+})
@@ -0,0 +1,499 @@
+import { describe, expect, it } from "vitest"
+import { isMxCellXmlComplete } from "@/lib/utils"
+import { editDiagram } from "@/packages/mcp-server/src/edit-diagram.ts"
+import { prepareNewDiagram } from "@/packages/mcp-server/src/new-diagram.ts"
+import {
+    normalizeToMxfile,
+    wrapCellsInModel,
+} from "@/packages/mcp-server/src/pages.ts"
+import {
+    addDefaultStyles,
+    applyStyleClasses,
+    expandStyles,
+    readStyleClasses,
+} from "@/packages/mcp-server/src/style-classes.ts"
+
+const geometry =
+    '<mxGeometry x="0" y="0" width="80" height="40" as="geometry"/>'
+const cell = (id: string, style: string, extra = "") =>
+    `<mxCell id="${id}" value="${id}" style="${style}" vertex="1" parent="1"${extra}>${geometry}</mxCell>`
+const edge = (id: string, style: string) =>
+    `<mxCell id="${id}" style="${style}" edge="1" parent="1" source="2" target="3"><mxGeometry relative="1" as="geometry"/></mxCell>`
+
+const BLUE =
+    '<mxStyle name="blue" value="fillColor=#dae8fc;strokeColor=#6c8ebf;"/>'
+
+describe("readStyleClasses", () => {
+    it("reads the definitions and removes them from the XML", () => {
+        const xml = `${BLUE}\n<mxStyle name="flow" value="edgeStyle=orthogonalEdgeStyle;"></mxStyle>\n${cell("2", "blue;")}`
+        const { classes, xml: rest } = readStyleClasses(xml)
+        expect(classes.get("blue")).toBe(
+            "fillColor=#dae8fc;strokeColor=#6c8ebf",
+        )
+        expect(classes.get("flow")).toBe("edgeStyle=orthogonalEdgeStyle")
+        expect(rest).toBe(cell("2", "blue;"))
+    })
+
+    it("resolves a definition that uses an earlier name", () => {
+        const xml = `${BLUE}<mxStyle name="pill" value="rounded=1;blue;arcSize=50;"/>`
+        const { classes } = readStyleClasses(xml)
+        expect(classes.get("pill")).toBe(
+            "rounded=1;fillColor=#dae8fc;strokeColor=#6c8ebf;arcSize=50",
+        )
+    })
+
+    it("leaves a definition that is still streaming in place", () => {
+        const xml = `${BLUE}<mxStyle name="flow" value="edgeSt`
+        const { classes, xml: rest } = readStyleClasses(xml)
+        expect(classes.size).toBe(1)
+        expect(rest).toBe('<mxStyle name="flow" value="edgeSt')
+    })
+})
+
+describe("applyStyleClasses", () => {
+    const classes = readStyleClasses(BLUE).classes
+
+    it("expands a name in place, so the overrides after it still win", () => {
+        const out = applyStyleClasses(
+            cell("2", "rhombus;blue;fontSize=14;"),
+            classes,
+        )
+        expect(out).toBe(
+            cell(
+                "2",
+                "rhombus;fillColor=#dae8fc;strokeColor=#6c8ebf;fontSize=14;",
+            ),
+        )
+    })
+
+    it("leaves unknown names, key=value tokens and other attributes alone", () => {
+        const xml = `${cell("2", "text;fontSize=blue;")}<mxCell id="3" vertex="1" parent="1" value="blue">${geometry}</mxCell>`
+        expect(applyStyleClasses(xml, classes)).toBe(xml)
+    })
+
+    it("works inside a wrapped model and keeps the attribute order", () => {
+        const xml = `<mxGraphModel><root><mxCell id="0"/><mxCell id="1" parent="0"/><mxCell id="2" style="blue;" value="A" vertex="1" parent="1">${geometry}</mxCell></root></mxGraphModel>`
+        expect(applyStyleClasses(xml, classes)).toBe(
+            xml.replace(
+                'style="blue;"',
+                'style="fillColor=#dae8fc;strokeColor=#6c8ebf;"',
+            ),
+        )
+    })
+})
+
+describe("addDefaultStyles", () => {
+    it("adds whiteSpace=wrap and html=1 to a shape", () => {
+        expect(addDefaultStyles(cell("2", "rounded=1;"))).toBe(
+            cell("2", "rounded=1;whiteSpace=wrap;html=1;"),
+        )
+    })
+
+    it("gives a shape without a style attribute one", () => {
+        const xml = `<mxCell id="2" value="A" vertex="1" parent="1">${geometry}</mxCell>`
+        expect(addDefaultStyles(xml)).toBe(
+            `<mxCell id="2" value="A" vertex="1" parent="1" style="whiteSpace=wrap;html=1;">${geometry}</mxCell>`,
+        )
+    })
+
+    it("keeps html=0 and an existing whiteSpace", () => {
+        const xml = cell("2", "html=0;whiteSpace=nowrap;")
+        expect(addDefaultStyles(xml)).toBe(xml)
+    })
+
+    it("adds only html=1 to icon shapes, images and edge labels", () => {
+        const icon = cell(
+            "2",
+            "shape=mxgraph.aws4.resourceIcon;resIcon=mxgraph.aws4.ec2;verticalLabelPosition=bottom;",
+        )
+        const image = cell("3", "image=data:image/png,abc;")
+        const label = cell("4", "edgeLabel;align=center;")
+        const unconnectable = cell("5", "align=center;", ' connectable="0"')
+        expect(addDefaultStyles(icon)).toBe(
+            cell(
+                "2",
+                "shape=mxgraph.aws4.resourceIcon;resIcon=mxgraph.aws4.ec2;verticalLabelPosition=bottom;html=1;",
+            ),
+        )
+        expect(addDefaultStyles(image)).toBe(
+            cell("3", "image=data:image/png,abc;html=1;"),
+        )
+        expect(addDefaultStyles(label)).toBe(
+            cell("4", "edgeLabel;align=center;html=1;"),
+        )
+        expect(addDefaultStyles(unconnectable)).toBe(
+            cell("5", "align=center;html=1;", ' connectable="0"'),
+        )
+    })
+
+    it("adds html=1 to edges and leaves the root cells alone", () => {
+        const roots = '<mxCell id="0"/><mxCell id="1" parent="0"/>'
+        expect(addDefaultStyles(roots + edge("4", "endArrow=block;"))).toBe(
+            roots + edge("4", "endArrow=block;html=1;"),
+        )
+    })
+})
+
+describe("expandStyles", () => {
+    it("expands the names, then adds the defaults", () => {
+        const xml = `${BLUE}${cell("2", "blue;")}`
+        expect(expandStyles(xml)).toBe(
+            cell(
+                "2",
+                "fillColor=#dae8fc;strokeColor=#6c8ebf;whiteSpace=wrap;html=1;",
+            ),
+        )
+    })
+})
+
+describe("prepareNewDiagram with named styles", () => {
+    it("saves plain draw.io XML without the definitions", () => {
+        const xml = `${BLUE}\n<mxStyle name="flow" value="edgeStyle=orthogonalEdgeStyle;exitX=0.5;exitY=1;entryX=0.5;entryY=0;"/>\n${cell("2", "blue;")}\n${cell("3", "rhombus;blue;")}\n${edge("4", "flow;")}`
+        const prepared = prepareNewDiagram(xml, { pageId: "p1" })
+        expect(prepared.ok).toBe(true)
+        if (!prepared.ok) return
+        expect(prepared.xml).not.toContain("mxStyle")
+        expect(prepared.xml).toContain(
+            'style="fillColor=#dae8fc;strokeColor=#6c8ebf;whiteSpace=wrap;html=1;"',
+        )
+        expect(prepared.xml).toContain(
+            'style="rhombus;fillColor=#dae8fc;strokeColor=#6c8ebf;whiteSpace=wrap;html=1;"',
+        )
+        expect(prepared.xml).toContain(
+            'style="edgeStyle=orthogonalEdgeStyle;exitX=0.5;exitY=1;entryX=0.5;entryY=0;html=1;"',
+        )
+    })
+})
+
+describe("editDiagram adds the default styles", () => {
+    it("adds html=1 and whiteSpace=wrap to an added cell", () => {
+        const file =
+            normalizeToMxfile(wrapCellsInModel(cell("2", "")), {
+                pageId: "p1",
+                pageName: "Page-1",
+            }) ?? ""
+        const outcome = editDiagram(
+            file,
+            [
+                {
+                    operation: "add",
+                    cell_id: "3",
+                    new_xml: cell("3", "rounded=1;"),
+                },
+            ],
+            {},
+        )
+        expect(outcome.ok).toBe(true)
+        if (!outcome.ok) return
+        expect(outcome.xml).toContain(
+            'style="rounded=1;whiteSpace=wrap;html=1;"',
+        )
+    })
+})
+
+describe("cells written in other shapes", () => {
+    it("keeps a self-closing cell without a style self-closing", () => {
+        const edge =
+            '<mxCell id="4" edge="1" parent="1" source="2" target="3"/>'
+        expect(addDefaultStyles(edge)).toBe(
+            '<mxCell id="4" edge="1" parent="1" source="2" target="3" style="html=1;"/>',
+        )
+        const shape = '<mxCell id="5" value="A" vertex="1" parent="1" />'
+        expect(addDefaultStyles(shape)).toBe(
+            '<mxCell id="5" value="A" vertex="1" parent="1" style="whiteSpace=wrap;html=1;"/>',
+        )
+    })
+
+    it("expands a name in a cell wrapped in a UserObject", () => {
+        const xml = `${BLUE}<UserObject id="4" label="Docs" link="https://example.com"><mxCell style="blue;" vertex="1" parent="1">${geometry}</mxCell></UserObject>`
+        expect(expandStyles(xml)).toBe(
+            `<UserObject id="4" label="Docs" link="https://example.com"><mxCell style="fillColor=#dae8fc;strokeColor=#6c8ebf;whiteSpace=wrap;html=1;" vertex="1" parent="1">${geometry}</mxCell></UserObject>`,
+        )
+    })
+
+    it("leaves text that sizes itself unwrapped", () => {
+        const xml = cell("2", "text;autosize=1;")
+        expect(addDefaultStyles(xml)).toBe(cell("2", "text;autosize=1;html=1;"))
+    })
+
+    it("reads a definition written without the closing slash", () => {
+        const { classes, xml } = readStyleClasses(
+            `<mxStyle name="a" value="x=1">\n${cell("2", "a;")}`,
+        )
+        expect(classes.get("a")).toBe("x=1")
+        expect(xml).toBe(cell("2", "a;"))
+    })
+
+    it("adds the defaults inside a full mxfile", () => {
+        const file = `<mxfile><diagram id="p" name="Page-1"><mxGraphModel><root><mxCell id="0"/><mxCell id="1" parent="0"/>${cell("2", "rounded=1;")}</root></mxGraphModel></diagram></mxfile>`
+        const prepared = prepareNewDiagram(file)
+        expect(prepared.ok).toBe(true)
+        if (!prepared.ok) return
+        expect(prepared.xml).toContain(
+            '<mxCell id="0"/><mxCell id="1" parent="0"/>',
+        )
+        expect(prepared.xml).toContain(
+            'style="rounded=1;whiteSpace=wrap;html=1;"',
+        )
+    })
+})
+
+describe("truncation check with named styles", () => {
+    it("treats output cut off right after the definitions as incomplete", () => {
+        expect(isMxCellXmlComplete(BLUE)).toBe(false)
+        expect(
+            isMxCellXmlComplete(`${BLUE}<mxStyle name="flow" value="edgeSt`),
+        ).toBe(false)
+        expect(isMxCellXmlComplete(`${BLUE}${cell("2", "blue;")}`)).toBe(true)
+    })
+})
+
+describe("styles are rewritten as written", () => {
+    it("keeps entities, a leading semicolon and a missing trailing one", () => {
+        const quoted = cell(
+            "2",
+            "fontFamily=&quot;Times New Roman&quot;;fillColor=red;",
+        )
+        expect(addDefaultStyles(quoted)).toBe(
+            cell(
+                "2",
+                "fontFamily=&quot;Times New Roman&quot;;fillColor=red;whiteSpace=wrap;html=1;",
+            ),
+        )
+        const noDefaults = cell("3", ";shape=rectangle;strokeColor=#000000")
+        expect(addDefaultStyles(noDefaults)).toBe(
+            cell(
+                "3",
+                ";shape=rectangle;strokeColor=#000000;whiteSpace=wrap;html=1;",
+            ),
+        )
+        const classes = readStyleClasses(BLUE).classes
+        expect(applyStyleClasses(cell("4", "blue"), classes)).toBe(
+            cell("4", "fillColor=#dae8fc;strokeColor=#6c8ebf"),
+        )
+    })
+
+    it("does not add wrapping next to html=0, since wrapping turns HTML on", () => {
+        const xml = cell("2", "html=0;")
+        expect(addDefaultStyles(xml)).toBe(xml)
+    })
+
+    it("wraps ordinary shape= shapes and leaves library icons alone", () => {
+        expect(
+            addDefaultStyles(
+                cell(
+                    "2",
+                    "shape=parallelogram;perimeter=parallelogramPerimeter;",
+                ),
+            ),
+        ).toBe(
+            cell(
+                "2",
+                "shape=parallelogram;perimeter=parallelogramPerimeter;whiteSpace=wrap;html=1;",
+            ),
+        )
+        expect(
+            addDefaultStyles(
+                cell(
+                    "3",
+                    "shape=mxgraph.cisco19.router;verticalLabelPosition=bottom;",
+                ),
+            ),
+        ).toBe(
+            cell(
+                "3",
+                "shape=mxgraph.cisco19.router;verticalLabelPosition=bottom;html=1;",
+            ),
+        )
+        // Library shapes whose label sits inside wrap like any shape
+        expect(
+            addDefaultStyles(cell("5", "shape=mxgraph.flowchart.process;")),
+        ).toBe(
+            cell(
+                "5",
+                "shape=mxgraph.flowchart.process;whiteSpace=wrap;html=1;",
+            ),
+        )
+        expect(addDefaultStyles(cell("4", "shape=image;image=a.png;"))).toBe(
+            cell("4", "shape=image;image=a.png;html=1;"),
+        )
+    })
+
+    it("escapes a quote that a single-quoted definition brings in", () => {
+        const xml = `<mxStyle name="a" value='fontFamily="Arial";'/>${cell("2", "a;")}`
+        expect(expandStyles(xml)).toBe(
+            cell("2", "fontFamily=&quot;Arial&quot;;whiteSpace=wrap;html=1;"),
+        )
+    })
+
+    it("resolves references in either order; duplicates and built-in names", () => {
+        const { classes } = readStyleClasses(
+            `<mxStyle name="b" value="c;x=1;"/><mxStyle name="c" value="y=2;"/><mxStyle name="c" value="y=3;"/><mxStyle name="loop" value="loop;z=1;"/>`,
+        )
+        // A name defined later still resolves; the last definition wins
+        expect(classes.get("b")).toBe("y=3;x=1")
+        // A name using itself stays a bare token
+        expect(classes.get("loop")).toBe("loop;z=1")
+        // The last definition of a name wins
+        expect(classes.get("c")).toBe("y=3")
+        // A definition named like a built-in replaces that built-in's meaning
+        const shadow = readStyleClasses(
+            '<mxStyle name="ellipse" value="fillColor=red;"/>',
+        ).classes
+        expect(applyStyleClasses(cell("2", "ellipse;"), shadow)).toBe(
+            cell("2", "fillColor=red;"),
+        )
+    })
+})
+
+describe("the auto-fix runs before the defaults", () => {
+    it("repairs quotes written as entities in an edit and then adds the defaults", () => {
+        const file = normalizeToMxfile(wrapCellsInModel(cell("2", "")), {
+            pageId: "p1",
+            pageName: "Page-1",
+        })
+        const outcome = editDiagram(
+            file ?? "",
+            [
+                {
+                    operation: "add",
+                    cell_id: "3",
+                    new_xml: `<mxCell id="3" value="B" style=&quot;rounded=1;&quot; vertex="1" parent="1">${geometry}</mxCell>`,
+                },
+            ],
+            {},
+        )
+        expect(outcome.ok).toBe(true)
+        if (!outcome.ok) return
+        expect(outcome.xml).toContain(
+            'style="rounded=1;whiteSpace=wrap;html=1;"',
+        )
+    })
+
+    it("repairs a new diagram the same way", () => {
+        const prepared = prepareNewDiagram(
+            `${BLUE}<mxCell id="2" value="A" style=&quot;blue;&quot; vertex="1" parent="1">${geometry}</mxCell>`,
+        )
+        expect(prepared.ok).toBe(true)
+        if (!prepared.ok) return
+        expect(prepared.xml).toContain(
+            'style="fillColor=#dae8fc;strokeColor=#6c8ebf;whiteSpace=wrap;html=1;"',
+        )
+    })
+})
+
+describe("definitions and cells the model may write imperfectly", () => {
+    it("escapes & and < in a definition, which the validator never sees", () => {
+        const xml = `<mxStyle name="f" value="fontFamily=A&B <C;"/>${cell("2", "f;")}`
+        const prepared = prepareNewDiagram(xml)
+        expect(prepared.ok).toBe(true)
+        if (!prepared.ok) return
+        expect(prepared.xml).toContain(
+            'style="fontFamily=A&amp;B &lt;C;whiteSpace=wrap;html=1;"',
+        )
+    })
+
+    it("accepts a lowercase tag, a style attribute and a name ending in ;", () => {
+        const { classes, xml } = readStyleClasses(
+            `<mxstyle name="blue;" style="fillColor=red;"/>${cell("2", "blue;")}`,
+        )
+        expect(classes.get("blue")).toBe("fillColor=red")
+        expect(xml).toBe(cell("2", "blue;"))
+    })
+
+    it("reads keys exactly, like draw.io, so a key after a space does not count", () => {
+        const xml = cell("2", "rounded=1; html=1; whiteSpace=wrap;")
+        expect(addDefaultStyles(xml)).toBe(
+            cell(
+                "2",
+                "rounded=1; html=1; whiteSpace=wrap;whiteSpace=wrap;html=1;",
+            ),
+        )
+        const classes = readStyleClasses(BLUE).classes
+        expect(
+            applyStyleClasses(
+                cell("3", "rounded=1; blue; fontSize=14;"),
+                classes,
+            ),
+        ).toBe(
+            cell(
+                "3",
+                "rounded=1;fillColor=#dae8fc;strokeColor=#6c8ebf; fontSize=14;",
+            ),
+        )
+    })
+
+    it("treats a vertex whose parent is an edge as an edge label", () => {
+        const xml = `${edge("e1", "")}<mxCell id="lbl" value="yes" style="align=center;" vertex="1" parent="e1"><mxGeometry relative="1" as="geometry"/></mxCell>`
+        expect(addDefaultStyles(xml)).toContain('style="align=center;html=1;"')
+    })
+
+    it("reports a definition that never closed and definitions without cells", () => {
+        const open = prepareNewDiagram(
+            `${BLUE}<mxStyle name="flow" value="edgeSt`,
+        )
+        expect(open.ok).toBe(false)
+        if (!open.ok) expect(open.error).toContain("not closed")
+        const only = prepareNewDiagram(BLUE)
+        expect(only.ok).toBe(false)
+        if (!only.ok) expect(only.error).toContain("no cells")
+    })
+})
+
+describe("edge labels and empty definitions", () => {
+    it("does not wrap a label added to an edge the XML does not show", () => {
+        const file =
+            normalizeToMxfile(
+                wrapCellsInModel(cell("2", "") + cell("3", "") + edge("4", "")),
+                {
+                    pageId: "p1",
+                    pageName: "Page-1",
+                },
+            ) ?? ""
+        const label = `<mxCell id="9" value="yes" style="text;" vertex="1" parent="4"><mxGeometry x="-0.5" relative="1" as="geometry"/></mxCell>`
+        const outcome = editDiagram(
+            file,
+            [{ operation: "add", cell_id: "9", new_xml: label }],
+            {},
+        )
+        expect(outcome.ok).toBe(true)
+        if (!outcome.ok) return
+        expect(outcome.xml).toContain('id="9" value="yes" style="text;html=1;"')
+        // The same through the function the preview uses
+        expect(addDefaultStyles(label, ["4"])).toContain('style="text;html=1;"')
+    })
+
+    it("treats a cell marked edge and vertex as an edge", () => {
+        const both = `<mxCell id="5" style="rounded=1;" edge="1" vertex="1" parent="1" source="2" target="3"><mxGeometry relative="1" as="geometry"/></mxCell>`
+        expect(addDefaultStyles(both)).toContain('style="rounded=1;html=1;"')
+    })
+
+    it("drops a name whose definition is empty instead of leaving a leading ;", () => {
+        const xml = `<mxStyle name="plain" value=""/>${cell("2", "plain;rounded=1;")}`
+        expect(expandStyles(xml)).toBe(
+            cell("2", "rounded=1;whiteSpace=wrap;html=1;"),
+        )
+    })
+
+    it("tells the model that edit_diagram has no named styles", () => {
+        const file =
+            normalizeToMxfile(wrapCellsInModel(cell("2", "")), {
+                pageId: "p1",
+                pageName: "Page-1",
+            }) ?? ""
+        const outcome = editDiagram(
+            file,
+            [
+                {
+                    operation: "add",
+                    cell_id: "3",
+                    new_xml: `${BLUE}${cell("3", "blue;")}`,
+                },
+            ],
+            {},
+        )
+        expect(outcome.ok).toBe(false)
+        if (!outcome.ok)
+            expect(outcome.errors[0]).toContain("not available in edit_diagram")
+    })
+})
@@ -11,11 +11,17 @@ const box = (id: string) =>
 const BEFORE_FIRST_EDIT = page(box("a"))
 const AFTER_FIRST_EDIT = page(box("a") + box("b"))

+const mocks = vi.hoisted(() => ({
+    loadDiagram: vi.fn((_xml: string, ..._rest: unknown[]) => null),
+    // The canvas for a test that needs another one
+    canvas: null as string | null,
+}))
+
 vi.mock("@/contexts/diagram-context", () => ({
    useDiagram: () => ({
-        chartXML: BEFORE_FIRST_EDIT,
-        chartXMLRef: { current: AFTER_FIRST_EDIT },
-        loadDiagram: vi.fn(() => null),
+        chartXML: mocks.canvas ?? BEFORE_FIRST_EDIT,
+        chartXMLRef: { current: mocks.canvas ?? AFTER_FIRST_EDIT },
+        loadDiagram: mocks.loadDiagram,
    }),
 }))

@@ -59,3 +65,163 @@ describe("the streaming preview of a second edit", () => {
        )
    })
 })
+
+describe("the streaming preview of display_diagram", () => {
+    it("expands the named styles and adds the defaults to the cells so far", () => {
+        mocks.loadDiagram.mockClear()
+        // A complete definition and cell, then a cell still being written
+        const xml = `<mxStyle name="blue" value="fillColor=#dae8fc;strokeColor=#6c8ebf;"/>
+<mxCell id="a" value="a" style="rounded=1;blue;" vertex="1" parent="1"><mxGeometry x="0" y="0" width="80" height="40" as="geometry"/></mxCell>
+<mxCell id="b" value="b" style="blue;" vertex="1" parent="1"><mxGeometry x="0" y="0" wid`
+        const messages = [
+            {
+                id: "m1",
+                role: "assistant",
+                parts: [
+                    {
+                        type: "tool-display_diagram",
+                        toolCallId: "draw-1",
+                        state: "input-streaming",
+                        input: { xml },
+                    },
+                ],
+            },
+        ] as any
+        renderHook(() =>
+            useDiagramStreaming({
+                messages,
+                processedToolCallsRef: { current: new Set() },
+                editDiagramOriginalXmlRef: { current: new Map() },
+                loadedMessageIdsRef: { current: new Set() },
+            }),
+        )
+        expect(mocks.loadDiagram).toHaveBeenCalledTimes(1)
+        const loaded = mocks.loadDiagram.mock.calls[0][0]
+        expect(loaded).toContain(
+            'style="rounded=1;fillColor=#dae8fc;strokeColor=#6c8ebf;whiteSpace=wrap;html=1;"',
+        )
+        expect(loaded).not.toContain("mxStyle")
+        expect(loaded).not.toContain('id="b"')
+    })
+})
+
+describe("the streaming preview of edit_diagram", () => {
+    it("adds the default styles to the cell being added, like the final edit", () => {
+        mocks.loadDiagram.mockClear()
+        const messages = [
+            {
+                id: "m1",
+                role: "assistant",
+                parts: [
+                    {
+                        type: "tool-edit_diagram",
+                        toolCallId: "edit-3",
+                        state: "input-streaming",
+                        input: {
+                            operations: [
+                                {
+                                    operation: "add",
+                                    cell_id: "c",
+                                    new_xml: box("c").replace(
+                                        'vertex="1"',
+                                        'style="rounded=1;" vertex="1"',
+                                    ),
+                                },
+                            ],
+                        },
+                    },
+                ],
+            },
+        ] as any
+        renderHook(() =>
+            useDiagramStreaming({
+                messages,
+                processedToolCallsRef: { current: new Set() },
+                editDiagramOriginalXmlRef: { current: new Map() },
+                loadedMessageIdsRef: { current: new Set() },
+            }),
+        )
+        expect(mocks.loadDiagram).toHaveBeenCalledTimes(1)
+        expect(mocks.loadDiagram.mock.calls[0][0]).toContain(
+            'style="rounded=1;whiteSpace=wrap;html=1;"',
+        )
+    })
+})
+
+describe("the streaming preview on the model's page", () => {
+    const box2 = (id: string, parent = "1") =>
+        `<mxCell id="${id}" value="${id}" vertex="1" parent="${parent}"><mxGeometry x="0" y="0" width="80" height="40" as="geometry"/></mxCell>`
+    // Page A has an edge "g"; on page B, "g" is a shape on layer "L"
+    const twoPages = `<mxfile><diagram id="pa" name="A"><mxGraphModel><root><mxCell id="0"/><mxCell id="1" parent="0"/>${box2("s")}${box2("t")}<mxCell id="g" edge="1" parent="1" source="s" target="t"><mxGeometry relative="1" as="geometry"/></mxCell></root></mxGraphModel></diagram><diagram id="pb" name="B"><mxGraphModel><root><mxCell id="0"/><mxCell id="L" parent="0"/>${box2("g", "L")}</root></mxGraphModel></diagram></mxfile>`
+    const cellOn = (xml: string, pageId: string, id: string) =>
+        new DOMParser()
+            .parseFromString(xml, "text/xml")
+            .querySelector(`diagram[id="${pageId}"] mxCell[id="${id}"]`)
+    const stream = (part: object) =>
+        renderHook(() =>
+            useDiagramStreaming({
+                messages: [
+                    { id: "m1", role: "assistant", parts: [part] },
+                ] as any,
+                processedToolCallsRef: { current: new Set() },
+                editDiagramOriginalXmlRef: { current: new Map() },
+                loadedMessageIdsRef: { current: new Set() },
+                turnPageIdRef: { current: "pb" },
+            }),
+        )
+
+    it("applies an edit to that page, with its layer and its edges", () => {
+        mocks.loadDiagram.mockClear()
+        mocks.canvas = twoPages
+        try {
+            stream({
+                type: "tool-edit_diagram",
+                toolCallId: "edit-p",
+                state: "input-streaming",
+                input: {
+                    operations: [
+                        {
+                            operation: "add",
+                            cell_id: "c",
+                            new_xml:
+                                '<mxCell id="c" value="c" x="10" y="10" w="80" h="40"/>',
+                        },
+                        {
+                            operation: "add",
+                            cell_id: "d",
+                            new_xml:
+                                '<mxCell id="d" value="d" parent="g" x="10" y="10" w="80" h="40"/>',
+                        },
+                    ],
+                },
+            })
+            const loaded = mocks.loadDiagram.mock.calls.at(-1)?.[0] as string
+            expect(cellOn(loaded, "pb", "c")?.getAttribute("parent")).toBe("L")
+            expect(cellOn(loaded, "pb", "d")?.getAttribute("style")).toContain(
+                "whiteSpace=wrap",
+            )
+            expect(cellOn(loaded, "pa", "c")).toBeNull()
+        } finally {
+            mocks.canvas = null
+        }
+    })
+
+    it("draws display_diagram's cells on that page", () => {
+        mocks.loadDiagram.mockClear()
+        mocks.canvas = twoPages
+        try {
+            stream({
+                type: "tool-display_diagram",
+                toolCallId: "draw-p",
+                state: "input-streaming",
+                input: { xml: box2("n") },
+            })
+            const loaded = mocks.loadDiagram.mock.calls.at(-1)?.[0] as string
+            expect(cellOn(loaded, "pb", "n")).not.toBeNull()
+            expect(cellOn(loaded, "pb", "g")).toBeNull()
+            expect(cellOn(loaded, "pa", "g")).not.toBeNull()
+        } finally {
+            mocks.canvas = null
+        }
+    })
+})
@@ -276,3 +276,102 @@ describe("a cut off drawing", () => {
        expect(refs.continuationOriginalRef.current).toBeNull()
    })
 })
+
+describe("the model's page", () => {
+    const page = (id: string, cells: string) =>
+        `<diagram id="${id}" name="Page ${id}"><mxGraphModel><root><mxCell id="0"/><mxCell id="1" parent="0"/>${cells}</root></mxGraphModel></diagram>`
+    const twoPages = `<mxfile>${page("a", box("A"))}${page("b", box("B"))}</mxfile>`
+    /** Ids of the shapes on a page (not the root cells) */
+    const shapesOn = (xml: string, pageId: string) =>
+        Array.from(
+            new DOMParser()
+                .parseFromString(xml, "text/xml")
+                .querySelectorAll(`diagram[id="${pageId}"] mxCell`),
+        )
+            .map((cell) => cell.getAttribute("id"))
+            .filter((id) => id !== "0" && id !== "1")
+
+    function setupOn(pageId: string | null) {
+        const onDisplayChart = vi.fn(
+            (
+                _xml: string,
+                _skipValidation?: boolean,
+                _mode?: string,
+                _meta?: object,
+            ): string | null => null,
+        )
+        const { result } = renderHook(() =>
+            useDiagramToolHandlers({
+                partialXmlRef: { current: "" },
+                continuationOriginalRef: { current: null },
+                editDiagramOriginalXmlRef: { current: new Map() },
+                processedToolCallsRef: { current: new Set() },
+                validationRetryCountRef: { current: 0 },
+                chartXMLRef: { current: twoPages },
+                turnPageIdRef: { current: pageId },
+                onDisplayChart,
+                onFetchChart: async () => twoPages,
+                enableVlmValidation: false,
+            }),
+        )
+        const addToolOutput = vi.fn()
+        const call = (toolName: string, input: object) =>
+            result.current.handleToolCall(
+                { toolCall: { toolCallId: "call-1", toolName, input } },
+                addToolOutput,
+            )
+        return { onDisplayChart, addToolOutput, call }
+    }
+
+    it("display_diagram draws on that page and keeps the others", async () => {
+        const { onDisplayChart, call } = setupOn("b")
+        await call("display_diagram", { xml: box("N") })
+        const [xml, , mode, meta] = onDisplayChart.mock.calls[0]
+        expect(mode).toBe("commit")
+        expect(meta).toEqual({ toolCallId: "call-1", pageId: "b" })
+        expect(shapesOn(xml, "a")).toEqual(["A"])
+        expect(shapesOn(xml, "b")).toEqual(["N"])
+        // The page keeps its own name
+        expect(xml).toContain('name="Page b"')
+    })
+
+    it("edit_diagram changes that page", async () => {
+        const { onDisplayChart, addToolOutput, call } = setupOn("b")
+        await call("edit_diagram", {
+            operations: [{ operation: "delete", cell_id: "B" }],
+        })
+        expect(addToolOutput.mock.lastCall?.[0].state).toBeUndefined()
+        const [xml] = onDisplayChart.mock.calls.at(-1) as [string]
+        expect(shapesOn(xml, "a")).toEqual(["A"])
+        expect(shapesOn(xml, "b")).toEqual([])
+    })
+
+    it("shows the model only its page when an edit fails", async () => {
+        const { addToolOutput, call } = setupOn("b")
+        await call("edit_diagram", {
+            operations: [{ operation: "delete", cell_id: "missing" }],
+        })
+        const output = addToolOutput.mock.lastCall?.[0]
+        expect(output?.state).toBe("output-error")
+        expect(output?.errorText).toContain('id="B"')
+        expect(output?.errorText).not.toContain('id="A"')
+    })
+
+    it("draws on the first page when the page is not known", async () => {
+        const { onDisplayChart, call } = setupOn(null)
+        await call("display_diagram", { xml: box("N") })
+        const [xml, , , meta] = onDisplayChart.mock.calls[0]
+        expect(meta).toEqual({ toolCallId: "call-1", pageId: null })
+        expect(shapesOn(xml, "a")).toEqual(["N"])
+        expect(shapesOn(xml, "b")).toEqual(["B"])
+    })
+
+    it("lets a drawing with several pages replace the document", async () => {
+        const { onDisplayChart, call } = setupOn("b")
+        const drawn = `<mxfile>${page("x", box("X"))}${page("y", box("Y"))}</mxfile>`
+        await call("display_diagram", { xml: drawn })
+        const [xml] = onDisplayChart.mock.calls[0]
+        expect(shapesOn(xml, "x")).toEqual(["X"])
+        expect(shapesOn(xml, "a")).toEqual([])
+    })
+})
@@ -1,9 +1,12 @@
+import pako from "pako"
 import { describe, expect, it } from "vitest"
 import {
    cn,
    extractCompleteMxCells,
+    extractDiagramXML,
    isMxCellXmlComplete,
    isRealDiagram,
+    replaceNodes,
 } from "@/lib/utils"
 import { BLANK_MXFILE } from "@/packages/mcp-server/src/pages.ts"

@@ -134,3 +137,63 @@ describe("extractCompleteMxCells", () => {
        )
    })
 })
+
+const pageBox = (id: string) => `<mxCell id="${id}" vertex="1" parent="1"/>`
+const pageModel = (cells: string) =>
+    `<mxGraphModel><root><mxCell id="0"/><mxCell id="1" parent="0"/>${cells}</root></mxGraphModel>`
+const pageOf = (id: string, cells: string) =>
+    `<diagram id="${id}" name="${id}">${pageModel(cells)}</diagram>`
+/** Ids of the shapes on a page (not the root cells) */
+const shapesOn = (xml: string, pageId: string) =>
+    Array.from(
+        new DOMParser()
+            .parseFromString(xml, "text/xml")
+            .querySelectorAll(`diagram[id="${pageId}"] mxCell`),
+    )
+        .map((cell) => cell.getAttribute("id"))
+        .filter((id) => id !== "0" && id !== "1")
+
+describe("replaceNodes", () => {
+    const two = `<mxfile>${pageOf("a", pageBox("A"))}${pageOf("b", pageBox("B"))}</mxfile>`
+
+    it("replaces the first page's cells by default", () => {
+        const out = replaceNodes(two, pageBox("N"))
+        expect(shapesOn(out, "a")).toEqual(["N"])
+        expect(shapesOn(out, "b")).toEqual(["B"])
+    })
+
+    it("replaces the given page's cells and keeps the others", () => {
+        const out = replaceNodes(two, pageBox("N"), "b")
+        expect(shapesOn(out, "a")).toEqual(["A"])
+        expect(shapesOn(out, "b")).toEqual(["N"])
+    })
+
+    it("uses the first page when the given page is not there", () => {
+        const out = replaceNodes(two, pageBox("N"), "zzz")
+        expect(shapesOn(out, "a")).toEqual(["N"])
+        expect(shapesOn(out, "b")).toEqual(["B"])
+    })
+})
+
+describe("extractDiagramXML", () => {
+    const packed = (model: string) =>
+        Buffer.from(pako.deflateRaw(encodeURIComponent(model))).toString(
+            "base64",
+        )
+    const file = `<mxfile><diagram id="a" name="a">${packed(pageModel(pageBox("A")))}</diagram><diagram id="b" name="b">${packed(pageModel(pageBox("B")))}</diagram></mxfile>`
+    const escapeAttr = (s: string) =>
+        s
+            .replace(/&/g, "&amp;")
+            .replace(/"/g, "&quot;")
+            .replace(/</g, "&lt;")
+            .replace(/>/g, "&gt;")
+    const svg = `<svg xmlns="http://www.w3.org/2000/svg" content="${escapeAttr(file)}"></svg>`
+    const dataUrl = `data:image/svg+xml;base64,${Buffer.from(svg).toString("base64")}`
+
+    it("returns the first page by default and a page by its id", () => {
+        expect(extractDiagramXML(dataUrl)).toContain('id="A"')
+        expect(extractDiagramXML(dataUrl, "b")).toContain('id="B"')
+        expect(extractDiagramXML(dataUrl, "b")).not.toContain('id="A"')
+        expect(extractDiagramXML(dataUrl, "zzz")).toContain('id="A"')
+    })
+})
Author	SHA1	Message	Date
dayuan.jiang	1067cba4d9	test: read the failed edit's output without unsafe optional chaining	2026-10-10 22:43:05 +09:00
dayuan.jiang	2757509d4e	fix(chat): the AI reads and draws the page the user is viewing The model always got the first page and display_diagram replaced the whole file with one page, so drawing on page 3 of a multi-page file deleted the other pages (#241), and edits went to page 1 while the user looked at another page. Now a turn records the page the user is viewing when the message is sent. That page's model goes to the model (also as previousXml, on regenerate and in edit_diagram error messages), selected shapes are sent on any page, display_diagram and append_diagram replace only that page (a drawing that brings several pages still replaces the file), edit_diagram targets it, and the streaming preview draws on it. Compact cells and default styles take the layer and the edges of that page, in the preview and in editDiagram. The editor bridge replaces the current page in place when the other pages are unchanged, so Ctrl+Z undoes an AI change on a multi-page file in one step; when a full load is needed, the user's page is shown again afterwards. Version summaries and the compare dialog count the page the change was made on.	2026-10-10 22:14:50 +09:00
Dayuan Jiang	cd5352ca88	feat(diagram): named styles and compact cells for shorter model output (#969 ) The model defines reused styles once as <mxStyle name="..." value="..."/> and refers to them by name, and writes shapes as one self-closing mxCell with x, y, w, h and edges with source and target. style-classes.ts and compact-cells.ts expand both back into standard draw.io XML after validation and add draw.io's html=1 / whiteSpace=wrap defaults; the diagram shown to the model is folded into the same notation. Prompts, tool descriptions and the MCP drawing guide teach the notation with shared examples. Measured on the five start-screen examples against main: gpt-6-luna 35% fewer output tokens, Claude Opus 5.5 41% fewer. Two five-model review rounds fixed quote-aware cell matching, attribute escaping, edge/vertex inference, root-id and layer handling, and several auto-fix gaps.	2026-10-10 21:58:21 +09:00
Dayuan Jiang	498ee628f1	fix(electron): upgrade to Electron 41.10.7 and let the builder follow package.json (#973 ) electron-builder.yml hard-coded electronVersion: 39.2.7 since #448, so every desktop release, including v0.5.0, shipped Electron 39.2.7 no matter which version package.json asked for. Removing the line makes electron-builder use the installed version (checked: the packaged Electron Framework reports 41.10.7 and the app starts and serves its page). Electron 41.10.7 fixes the four open Electron advisories (popup sandbox, webview Node integration, protocol handler cross-origin reads, sandboxed window inheritance) and its @electron/get 5 drops extract-zip, which clears two more alerts.	2026-10-10 21:53:37 +09:00