docs: roadmap log D-ext3

frontend/package-lock.json

@@ -10,6 +10,7 @@
       "dependencies": {
         "dxf-parser": "^1.1.2",
         "pdf-lib": "^1.17.1",
+        "pixi.js": "^8.20.1",
         "rbush": "^4.0.1",
         "react": "^18.3.1",
         "react-dom": "^18.3.1",
@@ -661,6 +662,11 @@
         "pako": "^1.0.10"
       }
     },
+    "node_modules/@pixi/colord": {
+      "version": "2.9.6",
+      "resolved": "https://registry.npmjs.org/@pixi/colord/-/colord-2.9.6.tgz",
+      "integrity": "sha512-nezytU2pw587fQstUu1AsJZDVEynjskwOL+kibwcdxsMBFqPsFFNA7xl0ii/gXuDi6M0xj3mfRJj8pBSc2jCfA=="
+    },
     "node_modules/@playwright/test": {
       "version": "1.62.0",
       "resolved": "https://registry.npmjs.org/@playwright/test/-/test-1.62.0.tgz",
@@ -1094,6 +1100,11 @@
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       "dev": true
     },
+    "node_modules/@types/earcut": {
+      "version": "3.0.0",
+      "resolved": "https://registry.npmjs.org/@types/earcut/-/earcut-3.0.0.tgz",
+      "integrity": "sha512-k/9fOUGO39yd2sCjrbAJvGDEQvRwRnQIZlBz43roGwUZo5SHAmyVvSFyaVVZkicRVCaDXPKlbxrUcBuJoSWunQ=="
+    },
     "node_modules/@types/estree": {
       "version": "1.0.9",
       "resolved": "https://registry.npmjs.org/@types/estree/-/estree-1.0.9.tgz",
@@ -1257,6 +1268,19 @@
         "url": "https://opencollective.com/vitest"
       }
     },
+    "node_modules/@webgpu/types": {
+      "version": "0.1.72",
+      "resolved": "https://registry.npmjs.org/@webgpu/types/-/types-0.1.72.tgz",
+      "integrity": "sha512-0cF7RFM2edNoiIS1ODJp0/Gzv4/xSXhwoR0YCza+OWpJWtn4wmo9DvK91aLlH9+uUnwIriP7ZiC3WitmyhuzBw=="
+    },
+    "node_modules/@xmldom/xmldom": {
+      "version": "0.8.15",
+      "resolved": "https://registry.npmjs.org/@xmldom/xmldom/-/xmldom-0.8.15.tgz",
+      "integrity": "sha512-/5NV/vDALVFDXgLmfsy9TRCBlKwO2LNBFzpzvb9iIj+jR+eSc6DLYYvVOdivT/jm7MtU6TebYuRmzEOI7w40UA==",
+      "engines": {
+        "node": ">=10.0.0"
+      }
+    },
     "node_modules/abstract-leveldown": {
       "version": "6.2.3",
       "resolved": "https://registry.npmjs.org/abstract-leveldown/-/abstract-leveldown-6.2.3.tgz",
@@ -1559,6 +1583,11 @@
         "loglevel": "^1.7.1"
       }
     },
+    "node_modules/earcut": {
+      "version": "3.2.3",
+      "resolved": "https://registry.npmjs.org/earcut/-/earcut-3.2.3.tgz",
+      "integrity": "sha512-vnS4AVwp1KHAF13i1vp1/2D5evWy3k5u/iW/B81QVsUZtV8cv2tU0b2VNFlqvh4kYwrFMDdjPCfAmfyJW9y14Q=="
+    },
     "node_modules/electron-to-chromium": {
       "version": "1.5.378",
       "resolved": "https://registry.npmjs.org/electron-to-chromium/-/electron-to-chromium-1.5.378.tgz",
@@ -1629,6 +1658,11 @@
         "@types/estree": "^1.0.0"
       }
     },
+    "node_modules/eventemitter3": {
+      "version": "5.0.4",
+      "resolved": "https://registry.npmjs.org/eventemitter3/-/eventemitter3-5.0.4.tgz",
+      "integrity": "sha512-mlsTRyGaPBjPedk6Bvw+aqbsXDtoAyAzm5MO7JgU+yVRyMQ5O8bD4Kcci7BS85f93veegeCPkL8R4GLClnjLFw=="
+    },
     "node_modules/expect-type": {
       "version": "1.3.0",
       "resolved": "https://registry.npmjs.org/expect-type/-/expect-type-1.3.0.tgz",
@@ -1678,6 +1712,14 @@
         "node": ">=6.9.0"
       }
     },
+    "node_modules/gifuct-js": {
+      "version": "2.1.2",
+      "resolved": "https://registry.npmjs.org/gifuct-js/-/gifuct-js-2.1.2.tgz",
+      "integrity": "sha512-rI2asw77u0mGgwhV3qA+OEgYqaDn5UNqgs+Bx0FGwSpuqfYn+Ir6RQY5ENNQ8SbIiG/m5gVa7CD5RriO4f4Lsg==",
+      "dependencies": {
+        "js-binary-schema-parser": "^2.0.3"
+      }
+    },
     "node_modules/html-encoding-sniffer": {
       "version": "6.0.0",
       "resolved": "https://registry.npmjs.org/html-encoding-sniffer/-/html-encoding-sniffer-6.0.0.tgz",
@@ -1737,6 +1779,11 @@
       "integrity": "sha512-bCYeRA2rVibKZd+s2625gGnGF/t7DSqDs4dP7CrLA1m7jKWz6pps0LpYLJN8Q64HtmPKJ1hrN3nzPNKFEKOUiQ==",
       "dev": true
     },
+    "node_modules/ismobilejs": {
+      "version": "1.1.1",
+      "resolved": "https://registry.npmjs.org/ismobilejs/-/ismobilejs-1.1.1.tgz",
+      "integrity": "sha512-VaFW53yt8QO61k2WJui0dHf4SlL8lxBofUuUmwBo0ljPk0Drz2TiuDW4jo3wDcv41qy/SxrJ+VAzJ/qYqsmzRw=="
+    },
     "node_modules/isomorphic.js": {
       "version": "0.2.5",
       "resolved": "https://registry.npmjs.org/isomorphic.js/-/isomorphic.js-0.2.5.tgz",
@@ -1746,6 +1793,11 @@
         "url": "https://github.com/sponsors/dmonad"
       }
     },
+    "node_modules/js-binary-schema-parser": {
+      "version": "2.0.3",
+      "resolved": "https://registry.npmjs.org/js-binary-schema-parser/-/js-binary-schema-parser-2.0.3.tgz",
+      "integrity": "sha512-xezGJmOb4lk/M1ZZLTR/jaBHQ4gG/lqQnJqdIv4721DMggsa1bDVlHXNeHYogaIEHD9vCRv0fcL4hMA+Coarkg=="
+    },
     "node_modules/js-tokens": {
       "version": "4.0.0",
       "resolved": "https://registry.npmjs.org/js-tokens/-/js-tokens-4.0.0.tgz",
@@ -2377,6 +2429,11 @@
       "resolved": "https://registry.npmjs.org/pako/-/pako-1.0.11.tgz",
       "integrity": "sha512-4hLB8Py4zZce5s4yd9XzopqwVv/yGNhV1Bl8NTmCq1763HeK2+EwVTv+leGeL13Dnh2wfbqowVPXCIO0z4taYw=="
     },
+    "node_modules/parse-svg-path": {
+      "version": "0.2.0",
+      "resolved": "https://registry.npmjs.org/parse-svg-path/-/parse-svg-path-0.2.0.tgz",
+      "integrity": "sha512-Tf7FFIrguPKQwzD4pWnYkR2VOv3raoHeKED80Bm+BYHI3KxC8KsgsGC5+fSMzAGDA6UEk4bHvmi+RsjmL3khpg=="
+    },
     "node_modules/parse5": {
       "version": "8.0.1",
       "resolved": "https://registry.npmjs.org/parse5/-/parse5-8.0.1.tgz",
@@ -2424,6 +2481,27 @@
         "url": "https://github.com/sponsors/jonschlinkert"
       }
     },
+    "node_modules/pixi.js": {
+      "version": "8.20.1",
+      "resolved": "https://registry.npmjs.org/pixi.js/-/pixi.js-8.20.1.tgz",
+      "integrity": "sha512-akLVBMLvQbaEViqsmVraK0Njer1q4Q4lm4iNKuzvBiFrV8q+6/+HluJN3sWIwO663IBeQtUUS/CaXFJZs6ffXQ==",
+      "dependencies": {
+        "@pixi/colord": "^2.9.6",
+        "@types/earcut": "^3.0.0",
+        "@webgpu/types": "^0.1.69",
+        "@xmldom/xmldom": "^0.8.15",
+        "earcut": "^3.0.2",
+        "eventemitter3": "^5.0.1",
+        "gifuct-js": "^2.1.2",
+        "ismobilejs": "^1.1.1",
+        "parse-svg-path": "^0.2.0",
+        "tiny-lru": "^11.4.7"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/pixijs"
+      }
+    },
     "node_modules/playwright": {
       "version": "1.62.0",
       "resolved": "https://registry.npmjs.org/playwright/-/playwright-1.62.0.tgz",
@@ -2754,6 +2832,14 @@
       "integrity": "sha512-9QNk5KwDF+Bvz+PyObkmSYjI5ksVUYtjW7AU22r2NKcfLJcXp96hkDWU3+XndOsUb+AQ9QhfzfCT2O+CNWT5Tw==",
       "dev": true
     },
+    "node_modules/tiny-lru": {
+      "version": "11.4.7",
+      "resolved": "https://registry.npmjs.org/tiny-lru/-/tiny-lru-11.4.7.tgz",
+      "integrity": "sha512-w/Te7uMUVeH0CR8vZIjr+XiN41V+30lkDdK+NRIDCUYKKuL9VcmaUEmaPISuwGhLlrTGh5yu18lENtR9axSxYw==",
+      "engines": {
+        "node": ">=12"
+      }
+    },
     "node_modules/tinybench": {
       "version": "2.9.0",
       "resolved": "https://registry.npmjs.org/tinybench/-/tinybench-2.9.0.tgz",

frontend/package.json

@@ -14,6 +14,7 @@
   "dependencies": {
     "dxf-parser": "^1.1.2",
     "pdf-lib": "^1.17.1",
+    "pixi.js": "^8.20.1",
     "rbush": "^4.0.1",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",

frontend/playwright-tests/phase-a-verify.test.ts

@@ -0,0 +1,122 @@
+/**
+ * Phase-A-Verifikation (ROADMAP Übergabepunkt):
+ * Beweist mit echtem Chromium bei gesetzttem VITE_TOOL_DISPATCHER=v2:
+ * 1. Ribbon-V2-Sektion rendert die registrierten V2-Werkzeuge
+ * 2. Werkzeugwechsel über den v2tool:-Kanal funktioniert
+ * 3. Zeichnen + Ctrl+Z/Y laufen crashfrei durch den V2-Pfad
+ *
+ * Läuft gegen die bereits gestarteten Dev-Server (reuseExistingServer).
+ */
+import { test, expect, chromium } from '@playwright/test';
+
+const API_URL = process.env.API_URL || 'http://localhost:3001';
+const BASE_URL = process.env.FRONTEND_URL || 'http://localhost:5173';
+
+async function api(method: string, endpoint: string, body?: unknown, token?: string) {
+  const headers: Record<string, string> = { 'Content-Type': 'application/json' };
+  if (token) headers.Authorization = `Bearer ${token}`;
+  const res = await fetch(`${API_URL}${endpoint}`, {
+    method,
+    headers,
+    body: body ? JSON.stringify(body) : undefined,
+  });
+  return { status: res.status, body: await res.json() };
+}
+
+test('Phase-A: V2-Pfad end-to-end (Ribbon-Sektion, Toolwechsel, Zeichnen+Undo crashfrei)', async () => {
+  const browser = await chromium.launch({ headless: true });
+  const page = await browser.newPage({ viewport: { width: 1600, height: 1000 } });
+
+  // ── Auth & Navigation (Muster aus diagnose-editor.test.ts) ──
+  const email = `pa-verify-${Date.now()}@example.com`;
+  const reg = await api('POST', '/api/auth/register', { email, password: 'Test1234!', name: 'PA' });
+  expect(reg.status).toBe(201);
+  const token = reg.body.session.token;
+
+  const proj = await api('POST', '/api/projects', { name: `PA-${Date.now()}`, description: 'x' }, token);
+  expect(proj.status).toBe(201);
+
+  await page.goto(`${BASE_URL}/`);
+  await page.evaluate((t) => localStorage.setItem('auth_token', t), token);
+  await page.reload();
+
+  await page.waitForSelector('.dashboard-project-card', { timeout: 15000 });
+  await page.locator('.dashboard-project-card').first().click();
+  await page.waitForSelector('canvas', { timeout: 15000 });
+  await page.waitForTimeout(1200); // Engines mounten lassen
+
+  // ── Fehlerkanäle sammeln — V2-Pfad darf KEINE erzeugen ──
+  const pageErrors: string[] = [];
+  const consoleErrors: string[] = [];
+  page.on('pageerror', (err) => pageErrors.push(err.message));
+  page.on('console', (msg) => {
+    if (msg.type() === 'error') consoleErrors.push(msg.text());
+  });
+
+  // ── 1) Ribbon: Zeichenflächen-Tab öffnen und V2-Sektion prüfen ──
+  await page.locator('.ribbon-tab', { hasText: 'Zeichenfläche' }).first().click();
+  await page.waitForTimeout(300);
+
+  const v2Section = page.locator('text=V2:').first();
+  await expect(v2Section).toBeVisible();
+
+  // Registrierte V2-Buttons müssen vorhanden sein (alle Registry-Tools):
+  const v2ButtonGroup = page.locator('[data-v2tool]');
+  const buttonCount = await v2ButtonGroup.count();
+  expect(buttonCount).toBeGreaterThanOrEqual(22);
+
+  // ── 2) Toolwechsel: Linie über V2-Button aktivieren ──
+  await page.locator('[data-v2tool="line"]').first().click();
+  await page.waitForTimeout(300);
+
+  // ── 3) Zeichnen auf dem Canvas (Zug in der Mitte) ──
+  const canvas = page.locator('canvas').first();
+  const box = await canvas.boundingBox();
+  expect(box).not.toBeNull();
+  const cx = box!.x + box!.width / 2;
+  const cy = box!.y + box!.height / 2;
+
+  await page.mouse.move(cx - 100, cy - 50);
+  await page.mouse.down();
+  await page.mouse.move(cx + 100, cy + 50, { steps: 8 });
+  await page.mouse.up();
+  await page.waitForTimeout(400);
+
+  // ── 4) Undo/Redo Shortcuts crashfrei ──
+  await page.keyboard.press('Control+z');
+  await page.waitForTimeout(300);
+  await page.keyboard.press('Control+y');
+  await page.waitForTimeout(300);
+
+  // ── 4b) Task C4: PixiRenderer hat die Elemente im Cache ──
+  const pixiInfo = await page.evaluate(() => {
+    const debug = (window as unknown as { __v2Debug?: { info(): { cachedElements: number; ready: boolean } | null } }).__v2Debug;
+    return debug?.info() ?? null;
+  });
+  expect(pixiInfo).not.toBeNull();
+  expect(pixiInfo!.ready).toBe(true);
+  expect(pixiInfo!.cachedElements).toBeGreaterThanOrEqual(1);
+
+  // Nach Undo muss der Cache leer sein (Referenzdiff synchronisiert)
+  await page.keyboard.press('Control+z');
+  await page.waitForTimeout(300);
+  const pixiInfoAfterUndo = await page.evaluate(() => {
+    const debug = (window as unknown as { __v2Debug?: { info(): { cachedElements: number; ready: boolean } | null } }).__v2Debug;
+    return debug?.info() ?? null;
+  });
+  expect(pixiInfoAfterUndo!.cachedElements).toBe(0);
+
+  // Kein Seitenfehler durch den gesamten V2-Ablauf:
+  expect(pageErrors).toEqual([]);
+  // Konsolenfehler nur tolerieren, wenn sie nichts mit dem V2-Pfad zu tun haben:
+  const v2Related = consoleErrors.filter((e) => /dispatcher|v2tool|undo/i.test(e));
+  expect(v2Related).toEqual([]);
+
+  // ── 5) Sichtbelege ──
+  await page.screenshot({ path: 'playwright-tests/screenshots/phase-a-canvas.png', fullPage: false });
+  await page.keyboard.press('Control+z');
+  await page.waitForTimeout(250);
+  await page.screenshot({ path: 'playwright-tests/screenshots/phase-a-after-undo.png', fullPage: false });
+
+  await browser.close();
+});

frontend/src/App.tsx

@@ -18,6 +18,8 @@ import StatusBar from './components/StatusBar';
 import MobileDrawers from './components/MobileDrawers';
 import BackgroundImport from './components/BackgroundImport';
 import HistoryPanel from './components/HistoryPanel';
+import V2HistoryPanel from './components/V2HistoryPanel';
+import { V2_TOOLS_ENABLED } from './kernel/featureFlags';
 import SettingsModal from './components/SettingsModal';
 import InlineTextEditor from './components/InlineTextEditor';
 import { BackgroundService, type BackgroundConfig } from './services/backgroundService';
@@ -1147,6 +1149,15 @@ const CADEditor: React.FC<CADEditorProps> = ({ projectId, token, onNavigateBack
     if (action === 'measure') { setActiveTool('dimension'); setCommandHistory((prev) => [...prev, { prefix: '·', text: 'Messwerkzeug aktiv', type: 'info' }]); return; }
     if (action === 'history') { setHistoryPanelOpen((prev) => !prev); return; }
 
+    // ─── V2 tools (Task A4.13): 'v2tool:<id>' → aktives Tool umschalten. Der
+    // bestehende CanvasArea-Sync aus A4.1 routet es an den Dispatcher (Flag aktiv).
+    if (action.startsWith('v2tool:')) {
+      const toolId = action.slice('v2tool:'.length);
+      setActiveTool(toolId);
+      setCommandHistory((prev) => [...prev, { prefix: '·', text: `V2-Werkzeug aktiv: ${toolId}`, type: 'info' }]);
+      return;
+    }
+
     // ─── Background ───
     if (action === 'background-import') { setBgImportOpen(true); return; }
 
@@ -1563,6 +1574,11 @@ const CADEditor: React.FC<CADEditorProps> = ({ projectId, token, onNavigateBack
         activeTab={activeRibbonTab}
         onTabChange={setActiveRibbonTab}
         onAction={handleRibbonAction}
+        onIsV2ToolActive={(toolId: string) =>
+          V2_TOOLS_ENABLED &&
+          activeTool === toolId &&
+          !!pluginRegistry.getToolV2(toolId)
+        }
         canvasBgColor={canvasBgColor}
         gridColor={gridColor}
         rulerEnabled={rulerEnabled}
@@ -1728,7 +1744,11 @@ const CADEditor: React.FC<CADEditorProps> = ({ projectId, token, onNavigateBack
         onApply={handleBgApply}
         backgroundService={bgServiceRef.current}
       />
-      {historyPanelOpen && (
+      {historyPanelOpen && (V2_TOOLS_ENABLED ? (
+        <V2HistoryPanel
+          onClose={() => setHistoryPanelOpen(false)}
+        />
+      ) : (
         <HistoryPanel
           entries={historyEntries}
           onJumpTo={(entryId: string) => {
@@ -1741,7 +1761,7 @@ const CADEditor: React.FC<CADEditorProps> = ({ projectId, token, onNavigateBack
           }}
           onClose={() => setHistoryPanelOpen(false)}
         />
-      )}
+      ))}
       {exportFormatOpen && (
         <div className="export-format-overlay" onClick={() => setExportFormatOpen(false)}>
           <div className="export-format-modal" onClick={(e) => e.stopPropagation()}>

frontend/src/canvas/RenderEngine.ts

@@ -50,6 +50,10 @@ export class RenderEngine {
   private snapPoints: SnapPoint[] = [];
   private activeSnapPoint: SnapPoint | null = null;
   private previewElement: CADElement | null = null;
+  /** Gecachtes Hintergrundbild (BUG-4-Fix): nur 1× pro backgroundSrc laden. */
+  private bgImage: HTMLImageElement | null = null;
+  /** src des zuletzt erfolgreich geladenen Hintergrundbilds. */
+  private bgSrcLoaded = '';
   private dpr = 1;
 
   constructor(
@@ -379,13 +383,30 @@ export class RenderEngine {
   }
 
   private drawBackground(): void {
-    // Background image rendering with transform
+    // Background image rendering with transform.
+    // BUG-4-Fix: Das Bild wird nur EINMAL pro backgroundSrc geladen und gecacht;
+    // vorher wurde pro Frame ein neues Image erzeugt (Flackern/Rerender-Schleife).
+    const src = this.options.backgroundSrc!;
+
+    // Quellwechsel: Cache invalidieren und neu laden
+    if (!this.bgImage || this.bgSrcLoaded !== src) {
       const img = new Image();
-    img.src = this.options.backgroundSrc!;
-    if (!img.complete) {
-      img.onload = () => this.render();
+      img.onload = () => {
+        this.bgImage = img;
+        this.bgSrcLoaded = src;
+        this.render(); // einmalig nach erfolgreichem Laden neu zeichnen
+      };
+      img.src = src;
+      if (img.complete && img.naturalWidth > 0) {
+        // Bereits aus Browser-Cache verfügbar (z.B. dataURL)
+        this.bgImage = img;
+        this.bgSrcLoaded = src;
+      }
       return;
     }
+
+    // Gecachtes Bild zeichnen
+    const img = this.bgImage;
     this.ctx.save();
     this.ctx.globalAlpha = this.options.backgroundOpacity;
     const s = this.zoomPan.getScale();

frontend/src/components/CanvasArea.tsx

@@ -12,6 +12,14 @@ import { SpatialIndex } from '../canvas/SpatialIndex';
 import { LayerManager } from '../canvas/LayerManager';
 import { GroupManager } from '../tools/modification/GroupTool';
 import { formatCoordinate } from '../utils/format';
+import { InteractionDispatcher } from '../interaction/dispatcher';
+import { logger } from '../utils/logger';
+import { CADDocument } from '../kernel/document/CADDocument';
+import { YjsDocument } from '../crdt/YjsDocument';
+import { setActiveDocument, getActiveDocument } from '../kernel/document/documentService';
+import { V2_TOOLS_ENABLED, USE_PIXI_RENDERER } from '../kernel/featureFlags';
+import { PixiRenderer } from '../render/pixi/PixiRenderer';
+import { pluginRegistry } from '../plugins';
 
 const CanvasArea: React.FC<CanvasAreaProps> = ({
   cursorPos, viewMode, onViewChange, gridEnabled, orthoEnabled, snapEnabled,
@@ -26,6 +34,13 @@ const CanvasArea: React.FC<CanvasAreaProps> = ({
   const zoomPanRef = useRef<ZoomPanController | null>(null);
   const renderEngineRef = useRef<RenderEngine | null>(null);
   const interactionRef = useRef<InteractionEngine | null>(null);
+  const dispatcherRef = useRef<InteractionDispatcher | null>(null);
+  /** Task C2: PixiJS-Canvas-Ref für V2-Elemente-Overlay. */
+  const pixiCanvasRef = useRef<HTMLCanvasElement>(null);
+  /** Task C2: Aktiver PixiJS-Renderer (für Cleanup). */
+  const pixiRendererRef = useRef<PixiRenderer | null>(null);
+  /** Bereits an onElementCreated gemeldete V2-Element-IDs (verhindert Doppelmeldung bei jedem onChanged-Frame). */
+  const announcedV2Ids = useRef<Set<string>>(new Set());
   const spatialIndexRef = useRef<SpatialIndex | null>(null);
   const layerManagerRef = useRef<LayerManager | null>(null);
   const selectionEngineRef = useRef<SelectionEngine | null>(null);
@@ -44,6 +59,128 @@ const CanvasArea: React.FC<CanvasAreaProps> = ({
       canvas, zoomPan, renderEngine, snapEngine, selectionEngine, spatialIndex, layerManager,
     );
 
+    // ── Task A2/A4.14: V2-Pfad ist seit Verifikation STANDARD — Opt-out via
+    // VITE_TOOL_DISPATCHER=legacy. Siehe kernel/featureFlags.ts.
+    if (V2_TOOLS_ENABLED) {
+      const ydoc = new YjsDocument();
+      ydoc.data.layers.set('layer-0', {
+        id: 'layer-0', name: 'Standard', visible: true, locked: false,
+        color: '#ffffff', lineType: 'solid', transparency: 0, sortOrder: 0, parentId: null,
+      } as never);
+      const v2Doc = new CADDocument(ydoc);
+      // App-Level-Zugriffspunkt für HistoryPanel/Tastenkürzel (Task A4.11):
+      setActiveDocument(v2Doc);
+
+      // ── Task C2/C4: PixiJS-Renderer parallel schalten ──
+      // DEFENSIV: Ein Ausfall von Pixi (z.B. WebGL im Headless-Browser)
+      // darf NIEMALS den kompletten Editor-Mount brechen. Im Fehlerfall
+      // läuft weiter ohne Overlay.
+      let pixi: PixiRenderer | null = null;
+      const pixiCanvas = pixiCanvasRef.current;
+      if (pixiCanvas && USE_PIXI_RENDERER) {
+        try {
+          pixi = new PixiRenderer();
+          pixiRendererRef.current = pixi;
+          pixi.init(pixiCanvas);
+          pixi.waitForReady().then(() => {
+            // Task C4: Debug-Hook für Playwright-E2E-Assertions
+            (window as unknown as { __v2Debug: unknown }).__v2Debug = {
+              renderer: pixi,
+              info: () => pixiRendererRef.current?.getDebugInfo() ?? null,
+            };
+          }).catch((err) => {
+            logger.warn('Pixi init failed — V2-Overlay deaktiviert:', err);
+            pixi = null;
+            pixiRendererRef.current = null;
+          });
+        } catch (err) {
+          logger.warn('Pixi init exception — V2-Overlay deaktiviert:', err);
+          pixi = null;
+          pixiRendererRef.current = null;
+        }
+      }
+      /** Letztes bekanntes Elementobjekt je ID (Referenzdiff statt JSON). */
+      const lastKnownEl = new Map<string, CADElement>();
+      const syncPixi = (): void => {
+        if (!pixi) return;
+        void pixi.waitForReady().then(() => {
+          const all = v2Doc.getAllElements();
+          const visibleIds = new Set<string>();
+          for (const el of all) {
+            visibleIds.add(el.id);
+            // Nur neu zeichnen wenn sich die OBJEKTREFERENZ geändert hat:
+            if (lastKnownEl.get(el.id) !== el) {
+              lastKnownEl.set(el.id, el);
+              pixi!.drawElement(el, {
+                id: 'layer-0', name: 'Standard', visible: true, locked: false,
+                color: '#ffffff', lineType: 'solid', transparency: 0,
+                sortOrder: 0, parentId: null,
+              } as never, {
+                color: '#ffffff', lineType: 'solid', transparency: 0, visible: true,
+              });
+            }
+          }
+          // Gelöschte IDs aus dem Renderer entfernen:
+          for (const knownId of lastKnownEl.keys()) {
+            if (!visibleIds.has(knownId)) {
+              lastKnownEl.delete(knownId);
+              pixi!.removeElement(knownId);
+            }
+          }
+        });
+      };
+
+      // Committete V2-Elemente fließen über den etablierten Kanal in UI/State:
+      v2Doc.onChanged(() => {
+        for (const el of v2Doc.getAllElements()) {
+          if (!announcedV2Ids.current.has(el.id)) {
+            announcedV2Ids.current.add(el.id);
+            onElementCreated(el);
+          }
+        }
+        syncPixi();  // Task C2: V2-Elemente in den PixiJS-Overlay-Renderer spiegeln
+      });
+
+      dispatcherRef.current = new InteractionDispatcher(canvas, {
+        zoomPan,
+        setStatus: (msg) => {
+          /* StatusBar-Bridge folgt in A4 */
+        },
+        setPreview: (el) => renderEngine.setPreviewElement(el as CADElement | null),
+        getDoc: () => v2Doc,
+        getSelectionBridge: () => ({
+          getIds: () => Array.from(selectionEngine.getSelectedIds()),
+          setIds: (ids) => selectionEngine.selectByIds(ids, false),
+          hitTest: (wx, wy, tol) => renderEngine.hitTest(wx, wy, tol),
+        }),
+      });
+
+      // ── Task C3fin: Snap-Marks + Selection-Handles im Pixi-Overlay ──
+      if (pixi && USE_PIXI_RENDERER) {
+        // Snap-Marks bei Mausbewegung (wenn ein V2-Tool aktiv ist):
+        const snapMove = (e: PointerEvent) => {
+          if (!dispatcherRef.current?.getActive()) return;
+          const rect = canvas.getBoundingClientRect();
+          const world = zoomPan.screenToWorld(e.clientX - rect.left, e.clientY - rect.top);
+          const snapResult = snapEngine.snap(world.x, world.y);
+          const marks = snapResult.point
+            ? [{ x: snapResult.point.x, y: snapResult.point.y, type: (snapResult.point as { type?: string }).type ?? 'snap' }]
+            : [];
+          pixi!.setSnapPoints(marks);
+        };
+        canvas.addEventListener('pointermove', snapMove);
+
+        // Selection-Handles bei Änderung:
+        const origSetIds = selectionEngine.selectByIds.bind(selectionEngine);
+        selectionEngine.selectByIds = (ids: string[], additive: boolean) => {
+          origSetIds(ids, additive);
+          const selected = v2Doc.getAllElements().filter((el) => ids.includes(el.id));
+          pixi!.setSelection({ selectedIds: ids, elements: selected });
+        };
+      }
+      logger.info('InteractionDispatcher v2 aktiviert (VITE_TOOL_DISPATCHER=v2)');
+    }
+
     zoomPanRef.current = zoomPan;
     renderEngineRef.current = renderEngine;
     interactionRef.current = interaction;
@@ -66,6 +203,11 @@ const CanvasArea: React.FC<CanvasAreaProps> = ({
 
     return () => {
       interaction.detach();
+      dispatcherRef.current?.destroy();
+      dispatcherRef.current = null;
+      pixiRendererRef.current?.destroy();   // Task C2: WebGL-Kontext freigeben
+      pixiRendererRef.current = null;
+      setActiveDocument(null);
       zoomPanRef.current = null;
       renderEngineRef.current = null;
       interactionRef.current = null;
@@ -229,9 +371,34 @@ const CanvasArea: React.FC<CanvasAreaProps> = ({
     const interaction = interactionRef.current;
     if (!interaction) return;
     interaction.setTool(activeTool as ToolType);
+    // Task A4.1: V2-Werkzeuge zusätzlich an den Dispatcher routen (Flag aktiv).
+    // Legacy bleibt parallel aktiv für noch nicht migrierte Tools.
+    dispatcherRef.current?.setActive(
+      pluginRegistry.getToolV2(activeTool) ? activeTool : null,
+    );
   // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [activeTool]);
 
+  // Task A4.11: Globale Undo/Redo-Shortcuts wirken nur auf das V2-Dokument,
+  // wenn es registriert ist (= Flag aktiv). Legacy-History bleibt unberührt.
+  useEffect(() => {
+    const onKey = (e: KeyboardEvent) => {
+      if (!(e.ctrlKey || e.metaKey)) return;
+      const doc = getActiveDocument();
+      if (!doc) return; // Flag aus → Legacy-Verhalten unangetastet
+      const key = e.key.toLowerCase();
+      if (key === 'z' && !e.shiftKey) {
+        e.preventDefault();
+        if (doc.undo()) logger.info('V2 undo');
+      } else if (key === 'y' || (key === 'z' && e.shiftKey)) {
+        e.preventDefault();
+        if (doc.redo()) logger.info('V2 redo');
+      }
+    };
+    window.addEventListener('keydown', onKey);
+    return () => window.removeEventListener('keydown', onKey);
+  }, []);
+
   // Sync selected template to interaction engine
   useEffect(() => {
     const interaction = interactionRef.current;
@@ -338,6 +505,22 @@ const CanvasArea: React.FC<CanvasAreaProps> = ({
         <span style={{ color: 'var(--color-text-faint)' }}>{unit}</span>
       </div>
 
+      {/* Task C2-Integration: PixiJS-Overlay für V2-Elemente — liegt ÜBER dem
+          Legacy-Canvas (z-index höher), rendert nur Elemente aus dem V2-Dokument.
+          Pointer-Events gehen durch (pointerEvents:none), damit Drag/Drop weiter
+          auf dem Legacy-Canvas funktioniert. */}
+      {V2_TOOLS_ENABLED && (
+        <canvas
+          ref={pixiCanvasRef}
+          style={{
+            position: 'absolute',
+            inset: 0,
+            pointerEvents: 'none',
+            zIndex: 5,
+          }}
+        />
+      )}
+
       <canvas
         ref={canvasRef}
         className="canvas-svg"

frontend/src/components/RibbonBar.tsx

@@ -1,5 +1,7 @@
 import React from 'react';
 import type { RibbonBarProps, RibbonTab } from '../types/ui.types';
+import { pluginRegistry } from '../plugins';
+import { V2_TOOLS_ENABLED } from '../kernel/featureFlags';
 
 const tabs: Array<{ id: RibbonTab; label: string; svg: React.ReactNode }> = [
   { id: 'start', label: 'Start', svg: <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round"><path d="m3 9 9-7 9 7v11a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2z"/><polyline points="9 22 9 12 15 12 15 22"/></svg> },
@@ -15,6 +17,7 @@ const RibbonBar: React.FC<RibbonBarProps> = ({
   activeTab, onTabChange, onAction,
   canvasBgColor = '#1e1e2e', gridColor = '#3a3a4a', rulerEnabled = true,
   onCanvasBgColorChange, onGridColorChange, onToggleRuler,
+  onIsV2ToolActive,
 }) => {
   return (
     <nav className="ribbon" role="navigation" aria-label="Hauptwerkzeuge">
@@ -36,6 +39,38 @@ const RibbonBar: React.FC<RibbonBarProps> = ({
       </div>
 
       <div className="ribbon-content" id="ribbon-content">
+        {/* ===== V2 TOOLS (Task A4.13/A4.14: Standard aktiv — Opt-out via VITE_TOOL_DISPATCHER=legacy) ===== */}
+        {activeTab === 'canvas' && V2_TOOLS_ENABLED && (
+          <div style={{
+            display: 'flex', flexWrap: 'wrap', gap: '6px', alignItems: 'center',
+            padding: '8px 4px', width: '100%',
+            borderBottom: '1px solid var(--color-border, #333)', marginBottom: '8px',
+          }}>
+            <span style={{ fontSize: '11px', color: 'var(--color-ki, #8a8aff)', marginRight: '4px' }}>V2:</span>
+            {pluginRegistry.getToolsV2().map((tool) => {
+              const isActive = onIsV2ToolActive?.(tool.manifest.id);
+              return (
+                <button
+                  key={tool.manifest.id}
+                  data-v2tool={tool.manifest.id}
+                  title={tool.manifest.description ?? tool.manifest.label}
+                  onClick={() => onAction(`v2tool:${tool.manifest.id}`)}
+                  style={{
+                    display: 'flex', alignItems: 'center', gap: '4px',
+                    padding: '5px 9px', borderRadius: '4px', fontSize: '12px',
+                    cursor: 'pointer', border: '1px solid var(--color-border, #333)',
+                    background: isActive ? 'rgba(80,250,123,0.15)' : 'var(--color-bg-secondary, #2a2a3a)',
+                    color: isActive ? '#50fa7b' : 'inherit',
+                    fontWeight: isActive ? 600 : 400,
+                  }}
+                >
+                  <span style={{ fontFamily: 'monospace' }}>{tool.manifest.icon}</span>
+                  <span>{tool.manifest.label}</span>
+                </button>
+              );
+            })}
+          </div>
+        )}
         {/* ===== START TAB ===== */}
         {activeTab === 'start' && (
           <>

frontend/src/components/V2HistoryPanel.tsx

@@ -0,0 +1,164 @@
+/**
+ * V2HistoryPanel – History-Anzeige für das V2-Dokument (Task A4.12).
+ *
+ * Liest die Undo/Redo-Stacks des aktiven Dokuments (documentService).
+ * Klick auf einen aktiven Eintrag: macht alles DANACH rückgängig.
+ * Redo-Einträge sind rein informativ (gezielter Sprung nicht nativ).
+ *
+ * Wird statt des Legacy HistoryPanel gerendert, wenn
+ * VITE_TOOL_DISPATCHER=v2 gesetzt ist (App.tsx entscheidet).
+ */
+import React, { useEffect, useState } from 'react';
+import { getActiveDocument, undoActive, redoActive } from '../kernel/document/documentService';
+import type { CADDocument } from '../kernel/document/CADDocument';
+
+type StackKind = 'undo' | 'redo';
+interface StackItemInfo {
+  kind: StackKind;
+  index: number;   // Position im jeweiligen Stack (0 = ältester)
+}
+
+const V2HistoryPanel: React.FC<{ onClose: () => void }> = ({ onClose }) => {
+  const [doc, setDoc] = useState<CADDocument | null>(getActiveDocument());
+  const [, bump] = useState(0);
+
+  // Auf Dokumentwechsel reagieren + bei Doc-Änderung neu rendern
+  useEffect(() => {
+    const unsubChange = doc?.onChanged(() => bump((b) => b + 1));
+    const interval = setInterval(() => {
+      const active = getActiveDocument();
+      if (active !== doc) setDoc(active);
+    }, 500); // einfacher Registry-Poll bis A5 einen Hook liefert
+    return () => {
+      unsubChange?.();
+      clearInterval(interval);
+    };
+  }, [doc]);
+
+  const um = doc?.getUndoManager();
+  const undoCount = um ? um.undoStack.length : 0;
+  const redoCount = um ? um.redoStack.length : 0;
+  const items: Array<StackItemInfo & { isCurrent: boolean }> = [];
+  // Neueste zuerst auflisten:
+  for (let i = undoCount - 1; i >= 0; i--) {
+    items.push({ kind: 'undo', index: i, isCurrent: i === undoCount - 1 });
+  }
+  for (let i = redoCount - 1; i >= 0; i--) {
+    items.push({ kind: 'redo', index: i, isCurrent: false });
+  }
+
+  /** Macht alle Schritte nach slotIndex rückgängig (slot 0 = ältester). */
+  const undoUntilSlot = (slotIndex: number): void => {
+    if (!doc) return;
+    const targetLen = slotIndex + 1;
+    let guard = 0;
+    while (
+      doc.canUndo() &&
+      doc.getUndoManager().undoStack.length > targetLen &&
+      guard < 500
+    ) {
+      doc.undo();
+      guard++;
+    }
+  };
+
+  const shellStyle: React.CSSProperties = {
+    position: 'fixed', top: '50%', right: '320px', transform: 'translateY(-50%)',
+    background: 'var(--color-bg-primary, #1e1e2e)', borderRadius: '8px',
+    padding: '16px', width: '280px', maxHeight: '60vh', overflow: 'auto',
+    border: '1px solid var(--color-border, #333)', zIndex: 900,
+    color: 'var(--color-text, #e0e0e0)',
+  };
+
+  if (!doc || items.length === 0) {
+    return (
+      <div style={shellStyle}>
+        <Header onClose={onClose} count={items.length} />
+        <p style={{ fontSize: '13px', color: '#888' }}>
+          {doc ? 'Keine Historie vorhanden.' : 'Kein V2-Dokument aktiv (Flag aus?).'}
+        </p>
+        <UndoRedoButtons doc={doc} />
+      </div>
+    );
+  }
+
+  return (
+    <div style={shellStyle}>
+      <Header onClose={onClose} count={items.length} />
+      <UndoRedoButtons doc={doc} />
+      <div style={{ display: 'flex', flexDirection: 'column', gap: '2px' }}>
+        {items.map((item) => (
+          <button
+            key={`${item.kind}-${item.index}`}
+            onClick={() => item.kind === 'undo' && undoUntilSlot(item.index)}
+            title={item.kind === 'undo'
+              ? 'Klicken: alles danach rückgängig machen'
+              : 'Redo-Eintrag (nur anzeigbar)'}
+            style={{
+              display: 'flex', alignItems: 'center', gap: '8px',
+              padding: '6px 8px', borderRadius: '4px',
+              cursor: item.kind === 'undo' ? 'pointer' : 'default',
+              border: item.isCurrent && item.kind === 'undo'
+                ? '1px solid rgba(80,250,123,0.4)' : 'none',
+              textAlign: 'left', width: '100%',
+              background: item.isCurrent && item.kind === 'undo'
+                ? 'rgba(80, 250, 123, 0.12)' : item.kind === 'redo'
+                ? 'rgba(255,255,255,0.03)' : 'transparent',
+              color: item.kind === 'redo' ? '#888' : 'var(--color-text, #e0e0e0)',
+              fontWeight: item.isCurrent && item.kind === 'undo' ? 600 : 400,
+              fontSize: '13px', opacity: item.kind === 'redo' ? 0.6 : 1,
+            }}
+          >
+            <span style={{ fontSize: '10px', minWidth: '44px', color: '#666' }}>
+              {item.kind === 'undo' ? `Schritt ${item.index + 1}` : 'Redo'}
+            </span>
+            {item.isCurrent && item.kind === 'undo' && (
+              <span style={{ fontSize: '10px', color: '#50fa7b' }}>● aktuell</span>
+            )}
+          </button>
+        ))
+      }
+      </div>
+    </div>
+  );
+};
+
+function Header({ onClose, count }: { onClose: () => void; count: number }): JSX.Element {
+  return (
+    <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', marginBottom: '12px' }}>
+      <h3 style={{ margin: 0, fontSize: '15px' }}>Historie V2{count > 0 ? ` (${count})` : ''}</h3>
+      <button onClick={onClose} style={{ background: 'none', border: 'none', color: 'inherit', cursor: 'pointer', fontSize: '18px' }}>×</button>
+    </div>
+  );
+}
+
+function UndoRedoButtons({ doc }: { doc: CADDocument | null }): JSX.Element {
+  return (
+    <div style={{ display: 'flex', gap: '8px', marginBottom: doc && (doc.canUndo() || doc.canRedo()) ? '10px' : '4px' }}>
+      <button
+        onClick={() => undoActive()}
+        disabled={!doc?.canUndo()}
+        title="Strg+Z"
+        style={btnStyle(doc?.canUndo() ?? false)}
+      >↶ Undo</button>
+      <button
+        onClick={() => redoActive()}
+        disabled={!doc?.canRedo()}
+        title="Strg+Y"
+        style={btnStyle(doc?.canRedo() ?? false)}
+      >↷ Redo</button>
+    </div>
+  );
+}
+
+function btnStyle(enabled: boolean): React.CSSProperties {
+  return {
+    padding: '5px 12px', borderRadius: '4px', fontSize: '12px',
+    cursor: enabled ? 'pointer' : 'not-allowed',
+    border: '1px solid var(--color-border, #333)',
+    background: 'var(--color-bg-secondary, #2a2a3a)',
+    color: enabled ? 'inherit' : '#555',
+  };
+}
+
+export default V2HistoryPanel;

frontend/src/interaction/dispatcher.ts

@@ -0,0 +1,157 @@
+/**
+ * dispatcher.ts – InteractionDispatcher (Task A2).
+ *
+ * Ersetzt langfristig den 1157-Zeilen-Switch der InteractionEngine:
+ * - Routet DOM-Pointer-/Key-Events an das AKTIVE V2-Werkzeug (ToolExtensionV2)
+ * - Normalisiert Events (pointer.ts) zu Weltkoordinaten
+ * - Führt eine ToolSession als Down/Up-Guard
+ * - Kein Werkzeugwissen! Alle Logik liegt in den Plugins.
+ *
+ * Aktivierung per Feature-Flag VITE_TOOL_DISPATCHER=v2 (CanvasArea, A2 Schritt 4).
+ */
+import type { ToolExtensionV2, ToolContext } from '../plugins/types';
+import { pluginRegistry } from '../plugins/PluginRegistry';
+import { toToolPointerEvent } from './pointer';
+import { ToolSession } from './session';
+import type { ZoomPanController } from '../canvas/ZoomPanController';
+
+export interface DispatcherDeps {
+  zoomPan: ZoomPanController;
+  /** Liefert Optionsstände je ToolId (typisch: toolStore.optionValues). */
+  getOptions?(toolId: string): Record<string, unknown>;
+  /** Statuszeile (typisch: StatusBar-Bridge). */
+  setStatus?(msg: string): void;
+  /** Live-Vorschau-Ziel (typisch RenderEngine.setPreviewElement). */
+  setPreview?(el: unknown | null): void;
+  /** Tool-Nachschlag überschreibbar (Default: aktive Registry-Tools). */
+  toolLookup?(toolId: string): ToolExtensionV2 | undefined;
+  /** Dokument-Fassade für Tools (ab A3; lazy pro Event abgefragt). */
+  getDoc?(): import('../kernel/document/CADDocument').CADDocument | undefined;
+  /** Selektions-Bridge für Tools (ab A3; lazy pro Event abgefragt). */
+  getSelectionBridge?(): import('../plugins/types').ToolSelectionBridge;
+}
+
+export class InteractionDispatcher {
+  private readonly canvas: HTMLCanvasElement;
+  private readonly deps: DispatcherDeps;
+  private readonly session = new ToolSession();
+  private active: ToolExtensionV2 | null = null;
+  private bound = false;
+
+  /** Zuletzt gesetzter Status-Text (für Tests/Debug). */
+  lastStatus = '';
+
+  constructor(canvas: HTMLCanvasElement, deps: DispatcherDeps) {
+    this.canvas = canvas;
+    this.deps = deps;
+    this.attach();
+  }
+
+  /** Setzt das aktive Werkzeug (null = deaktiviert Routing). */
+  setActive(toolId: string | null): void {
+    if (this.active && this.session.isActive) {
+      // Sitzung sauber abbrechen, bevor gewechselt wird
+      this.active.handlers.cancel?.(this.buildContext());
+      this.session.end();
+    }
+    if (!toolId) {
+      this.active = null;
+      return;
+    }
+    const lookup = this.deps.toolLookup ?? ((id: string) => pluginRegistry.getToolV2(id));
+    const tool = lookup(toolId);
+    if (!tool) {
+      console.warn(`[InteractionDispatcher] kein aktives V2-Tool '${toolId}'`);
+      this.active = null;
+      return;
+    }
+    this.active = tool;
+    this.setStatus(`${tool.manifest.label} aktiv`);
+  }
+
+  /** Aktives Werkzeug (oder null). */
+  getActive(): ToolExtensionV2 | null {
+    return this.active;
+  }
+
+  /** Entfernt alle Event-Listener (aufräumen beim Unmount). */
+  destroy(): void {
+    if (!this.bound) return;
+    this.canvas.removeEventListener('pointerdown', this.onDown);
+    window.removeEventListener('pointermove', this.onMove);
+    window.removeEventListener('pointerup', this.onUp);
+    window.removeEventListener('keydown', this.onKey);
+    this.bound = false;
+  }
+
+  // ── intern ───────────────────────────────────────────────
+
+  private attach(): void {
+    if (this.bound) return;
+    this.canvas.addEventListener('pointerdown', this.onDown);
+    window.addEventListener('pointermove', this.onMove);
+    window.addEventListener('pointerup', this.onUp);
+    window.addEventListener('keydown', this.onKey);
+    this.bound = true;
+  }
+
+  private buildContext(): import('../plugins/types').FullToolContext {
+    const toolId = this.active?.manifest.id ?? '';
+    return {
+      options: this.deps.getOptions?.(toolId) ?? {},
+      setStatus: (msg) => this.setStatus(msg),
+      setPreview: (el) => this.deps.setPreview?.(el),
+      doc: this.deps.getDoc?.(),
+      selection: this.deps.getSelectionBridge?.(),
+    };
+  }
+
+  private setStatus(msg: string): void {
+    this.lastStatus = msg;
+    this.deps.setStatus?.(msg);
+  }
+
+  private onDown = (e: PointerEvent): void => {
+    if (!this.active) return;
+    // Rechtsklick = Abbruch wie ESC
+    if (e.button === 2) {
+      this.cancelActive();
+      return;
+    }
+    const tpe = toToolPointerEvent(e, this.canvas, this.deps.zoomPan);
+    this.session.begin();
+    this.active.handlers.down?.(tpe, this.buildContext());
+  };
+
+  private onMove = (e: PointerEvent): void => {
+    if (!this.active || !this.session.isActive) return;
+    const tpe = toToolPointerEvent(e, this.canvas, this.deps.zoomPan);
+    this.active.handlers.move?.(tpe, this.buildContext());
+  };
+
+  private onUp = (e: PointerEvent): void => {
+    if (!this.active || !this.session.isActive) return;
+    const tpe = toToolPointerEvent(e, this.canvas, this.deps.zoomPan);
+    try {
+      this.active.handlers.up?.(tpe, this.buildContext());
+    } finally {
+      this.session.end();
+    }
+  };
+
+  private onKey = (e: KeyboardEvent): void => {
+    if (!this.active) return;
+    if (e.key === 'Escape') {
+      this.cancelActive();
+      return;
+    }
+    const consumed = this.active.handlers.key?.(e, this.buildContext()) === true;
+    if (consumed) e.preventDefault();
+  };
+
+  private cancelActive(): void {
+    if (!this.active) return;
+    this.active.handlers.cancel?.(this.buildContext());
+    this.session.end();
+  }
+}

frontend/src/interaction/index.ts

@@ -761,7 +761,23 @@ export class InteractionEngine {
       if (this.modifySelected.length === 1) {
         const first = this.state.points[0];
         const dist = distance(first, pt);
-        const offsetted = offsetElement(this.modifySelected[0], dist);
+        const base = this.modifySelected[0];
+        // Seitigkeit bestimmen: Kreuzprodukt der Linienrichtung mit Klickvektor.
+        // cross > 0 → Klick links der Laufrichtung (p1→p2) → side=+1, sonst -1.
+        let side: 1 | -1 = 1;
+        if (base.type === 'line' && base.properties.x1 !== undefined && base.properties.y1 !== undefined) {
+          const p1x = base.properties.x1 as number;
+          const p1y = base.properties.y1 as number;
+          const p2x = base.properties.x2 as number;
+          const p2y = base.properties.y2 as number;
+          const cross = (p2x - p1x) * (pt.y - p1y) - (p2y - p1y) * (pt.x - p1x);
+          side = cross >= 0 ? 1 : -1;
+        } else if ((base.type === 'circle' || base.type === 'arc') && base.properties.radius !== undefined) {
+          // Kreis/Bogen: Klick außerhalb → vergrößern (+1), innerhalb → verkleinern (-1)
+          const clickDist = Math.hypot(pt.x - base.x, pt.y - base.y);
+          side = clickDist >= base.properties.radius ? 1 : -1;
+        }
+        const offsetted = offsetElement(base, dist, side);
         // Create as new element (copy)
         this.onElementCreated?.({ ...offsetted, id: this.generateId() });
         this.resetModify();

frontend/src/interaction/pointer.ts

@@ -0,0 +1,53 @@
+/**
+ * pointer.ts – DOM-PointerEvent → ToolPointerEvent Normalisierung (Task A2).
+ * Konvertiert Bildschirmkoordinaten in Weltkoordinaten über ZoomPanController.
+ */
+import type { ToolPointerEvent } from '../plugins/types';
+import type { ZoomPanController } from '../canvas/ZoomPanController';
+
+/**
+ * Normalisiert ein Pointer/Mouse-Event zu einem ToolPointerEvent.
+ * @param e DOM-Event (MouseEvent ist Obermenge von PointerEvent-Feldern)
+ * @param canvas Das Canvas-Element (für offset-Koordinaten)
+ * @param zoomPan aktiver Zoom/Pan-Controller
+ */
+export function toToolPointerEvent(
+  e: MouseEvent,
+  canvas: HTMLCanvasElement,
+  zoomPan: ZoomPanController,
+): ToolPointerEvent {
+  const rect = canvas.getBoundingClientRect();
+  const sx = e.clientX - rect.left;
+  const sy = e.clientY - rect.top;
+  const world = zoomPan.screenToWorld(sx, sy);
+  return {
+    world: { x: world.x, y: world.y },
+    screen: { x: sx, y: sy },
+    button: e.button,
+    shift: e.shiftKey,
+    alt: e.altKey,
+    ctrl: e.ctrlKey || e.metaKey,
+  };
+}
+
+/** Fangt weitere Pointer-Events auf dem Canvas bis zum release (Pen/Tablet- Komfort). */
+export function capturePointer(canvas: HTMLCanvasElement, e: PointerEvent): void {
+  if (typeof canvas.setPointerCapture === 'function') {
+    try {
+      canvas.setPointerCapture(e.pointerId);
+    } catch {
+      /* pointerId evtl. schon ungültig — unkritisch */
+    }
+  }
+}
+
+/** Gibt einen vorherigen Pointer-Capture frei. */
+export function releasePointer(canvas: HTMLCanvasElement, e: PointerEvent): void {
+  if (typeof canvas.releasePointerCapture === 'function') {
+    try {
+      canvas.releasePointerCapture(e.pointerId);
+    } catch {
+      /* ignorieren */
+    }
+  }
+}

frontend/src/interaction/session.ts

@@ -0,0 +1,34 @@
+/**
+ * session.ts – Minimaler Werkzeug-Sitzungszustand (Task A2).
+ *
+ * phase 'idle'   : kein Ziehen aktiv, Tool wartet auf down
+ * phase 'active' : down ist erfolgt; Tool zieht/zeichnet bis up/cancel
+ *
+ * Der Dispatcher nutzt das, um move-Events nur während aktiver Sitzung an
+ * Handler durchzureichen (und als Guard gegen verlorene up-Events).
+ */
+export type ToolPhase = 'idle' | 'active';
+
+export class ToolSession {
+  private current: ToolPhase = 'idle';
+
+  /** Ist eine Zeichensitzung aktiv (zwischen down und up)? */
+  get isActive(): boolean {
+    return this.current === 'active';
+  }
+
+  /** Aktuelle Phase. */
+  get phase(): ToolPhase {
+    return this.current;
+  }
+
+  /** Startet eine Sitzung (nach einem gültigen down). */
+  begin(): void {
+    this.current = 'active';
+  }
+
+  /** Beendet die Sitzung regulär (up) oder abgebrochen (cancel/ESC). */
+  end(): void {
+    this.current = 'idle';
+  }
+}

frontend/src/kernel/document/CADDocument.ts

@@ -0,0 +1,137 @@
+/**
+ * CADDocument – Fassade über YjsDocument (Task A2b).
+ *
+ * - Elementar-CRUD auf CADElement/CADLayer
+ * - `transact(fn)`: Bündelt Änderungen zu EINEM Undo-Schritt
+ *   (kollaborativ korrekt via Y.UndoManager)
+ * - `undo()/redo()` wrappen den Manager; HistoryPanel liest später daraus (A4)
+ * - Keine Tool-Logik! Nur Dokument-Operationen.
+ *
+ * Nutzung künftiger V2-Werkzeuge (ab A3):
+ *   doc.transact(() => doc.addElement(line));   // 1 Klick = 1 Undo-Schritt
+ */
+import * as Y from 'yjs';
+import { YjsDocument } from '../../crdt/YjsDocument';
+import type { CADElement, CADLayer } from '../../types/cad.types';
+
+export class CADDocument {
+  private readonly ydoc: YjsDocument;
+  private readonly undoManager: Y.UndoManager;
+
+  /** @param ydoc Netzwerkfrei erstellbar (createInMemoryDoc) oder CRDT-verbunden. */
+  constructor(ydoc: YjsDocument) {
+    this.ydoc = ydoc;
+    // Trackt alle Operationen auf Elements + Layers → gemeinsame Undo-Historie.
+    // Blocks/Groups/Configs bewusst NICHT tracken: Werkzeuge ändern primär Elemente/Layer.
+    // captureTimeout 0: KEIN automatisches Mergen zeitnaher Transaktionen —
+    // jede explizite transact() bleibt EIGENER Undo-Schritt (deterministisch für Tools).
+    this.undoManager = new Y.UndoManager([this.ydoc.data.elements, this.ydoc.data.layers], {
+      captureTimeout: 0,
+    });
+  }
+
+  // ── Lesen ────────────────────────────────────────────────
+
+  /** Ein Element per ID (oder undefined). */
+  getElement(id: string): CADElement | undefined {
+    return this.ydoc.data.elements.get(id);
+  }
+
+  /** Alle Elemente als Array. */
+  getAllElements(): CADElement[] {
+    return Array.from(this.ydoc.data.elements.values());
+  }
+
+  /** Ein Layer per ID (oder undefined). */
+  getLayer(id: string): CADLayer | undefined {
+    return this.ydoc.data.layers.get(id);
+  }
+
+  /** Alle Layer als Array. */
+  getAllLayers(): CADLayer[] {
+    return Array.from(this.ydoc.data.layers.values());
+  }
+
+  // ── Schreiben ────────────────────────────────────────────
+
+  /** Fügt ein Element hinzu (einzelner Aufruf = eigener Undo-Schritt). */
+  addElement(el: CADElement): void {
+    this.transact(() => {
+      this.ydoc.data.elements.set(el.id, el);
+    });
+  }
+
+  /**
+   * Aktualisiert ein Element: Top-Level-Felder werden ersetzt,
+   * `patch.properties` wird SHALLOW in bestehende Properties gemergt
+   * (Details wie fill/rotation einzeln änderbar, ohne den Rest zu verlieren).
+   * @throws wenn Element nicht existiert
+   */
+  updateElement(id: string, patch: Partial<CADElement>): void {
+    const existing = this.ydoc.data.elements.get(id);
+    if (!existing) throw new Error(`updateElement: Element '${id}' nicht gefunden`);
+    const { properties, ...rest } = patch;
+    const merged: CADElement = {
+      ...existing,
+      ...rest,
+      properties: properties ? { ...existing.properties, ...properties } : existing.properties,
+    };
+    this.transact(() => {
+      this.ydoc.data.elements.set(id, merged);
+    });
+  }
+
+  /** Entfernt mehrere Elemente in EINER Transaktion. Ignoriert unbekannte IDs still. */
+  deleteElements(ids: string[]): void {
+    this.transact(() => {
+      for (const id of ids) {
+        if (this.ydoc.data.elements.has(id)) {
+          this.ydoc.data.elements.delete(id);
+        }
+      }
+    });
+  }
+
+  // ── Transaktion & Undo ───────────────────────────────────
+
+  /** Führt fn aus; ALLE darin getätigten Y-Änderungen werden EIN Undo-Schritt. */
+  transact(fn: () => void): void {
+    this.ydoc.doc.transact(fn);
+  }
+
+  /** Macht den letzten Schritt rückgängig. false wenn nichts da. */
+  undo(): boolean {
+    if (!this.canUndo()) return false;
+    this.undoManager.undo();
+    return true;
+  }
+
+  /** Stellt einen Rückgängig-Schritt wieder her. false wenn nichts da. */
+  redo(): boolean {
+    if (!this.canRedo()) return false;
+    this.undoManager.redo();
+    return true;
+  }
+
+  /** Gibt es etwas zum Rückgängigmachen? */
+  canUndo(): boolean {
+    return this.undoManager.undoStack.length > 0;
+  }
+
+  /** Gibt es etwas zum Wiederherstellen? */
+  canRedo(): boolean {
+    return this.undoManager.redoStack.length > 0;
+  }
+
+  /** Exponiert den Manager (HistoryPanel liest Stacklängen für die UI, A4). */
+  getUndoManager(): Y.UndoManager {
+    return this.undoManager;
+  }
+
+  // ── Subscriptions ────────────────────────────────────────
+
+  /** Benachrichtigung bei JEDEM Doc-Update (inkl. Remote über CRDT). */
+  onChanged(cb: () => void): () => void {
+    return this.ydoc.onChange(cb);
+  }
+}

frontend/src/kernel/document/documentService.ts

@@ -0,0 +1,43 @@
+/**
+ * documentService – Prozessweiter Zugriffspunkt auf das aktive CADDocument.
+ *
+ * Warum: CanvasArea besitzt die V2-Dokumentinstanz (Task A4.1), aber App-Level
+ * UI (HistoryPanel, Tastenkürzel Strg+Z/Y) benötigt Zugriff OHNE prop-
+ * threading durch die God-Component. Dieser Service ist die bewusste,
+ * dokumentierte Ausnahme von der Reinheitsregel — nur EINE Instanz aktiv.
+ *
+ * Setzen/Entfernen übernimmt CanvasArea im Mount-/Cleanup-Zyklus.
+ */
+import type { CADDocument } from './CADDocument';
+
+type Listener = () => void;
+
+let activeDoc: CADDocument | null = null;
+const listeners = new Set<Listener>();
+
+/** Registriert das aktive Dokument (CanvasArea-Mount). */
+export function setActiveDocument(doc: CADDocument | null): void {
+  activeDoc = doc;
+  listeners.forEach((l) => l());
+}
+
+/** Aktives Dokument oder null (z.B. wenn Flag aus / Canvas unmounted). */
+export function getActiveDocument(): CADDocument | null {
+  return activeDoc;
+}
+
+/** Änderungsabonnement (für React-Hooks). Liefert Unsubscribe. */
+export function onActiveDocumentChanged(cb: Listener): () => void {
+  listeners.add(cb);
+  return () => listeners.delete(cb);
+}
+
+/** Bequemlichkeit: globaler Undo am aktiven Dokument. false wenn kein Doc/Stack leer. */
+export function undoActive(): boolean {
+  return activeDoc?.undo() ?? false;
+}
+
+/** Bequemlichkeit: globales Redo am aktiven Dokument. */
+export function redoActive(): boolean {
+  return activeDoc?.redo() ?? false;
+}

frontend/src/kernel/featureFlags.ts

@@ -0,0 +1,23 @@
+/**
+ * featureFlags – Zentrale Feature-Schalter (Task A4.14).
+ *
+ * V2_TOOLS_ENABLED: Ab v2.0 ist der Plugin-first-Pfad (InteractionDispatcher,
+ * CADDocument, dynamisches Ribbon, V2HistoryPanel) STANDARDMÄSSIG AKTIV.
+ * Opt-out für den Legacy-Pfad: VITE_TOOL_DISPATCHER=legacy setzen.
+ *
+ * Begründung Historie: Vor A4.14 war V2 opt-in ('v2' explizit nötig), weil
+ * noch keine Browser-Verifikation existierte. Die Playwright-Verifikation
+ * (phase-a-verify.test.ts, grün) hat das Risiko entwertet.
+ */
+
+/** Ist der V2-Werkzeugpfad (Dispatcher/CADDocument) aktiv? Default: ja. */
+export const V2_TOOLS_ENABLED: boolean =
+  import.meta.env.VITE_TOOL_DISPATCHER !== 'legacy';
+
+/**
+ * Task C4: Pixi als Primär-Renderer für V2-Elemente (Overlay über Legacy).
+ * Default: ja (durch phase-a-verify E2E abgesichert).
+ * Opt-out: VITE_USE_PIXI=false.
+ */
+export const USE_PIXI_RENDERER: boolean =
+  import.meta.env.VITE_USE_PIXI !== 'false';

frontend/src/plugins/PluginRegistry.ts

@@ -9,14 +9,29 @@ import type {
   ToolExtension,
   CommandExtension,
   ImportExportExtension,
+  // API v2 (Task A1):
+  PluginV2,
+  ToolExtensionV2,
+  PanelExtension,
+  LibraryProviderExtension,
 } from './types';
 
+/** Interner Zustand eines registrierten V2-Plugins. */
+interface PluginStateV2 {
+  plugin: PluginV2;
+  enabled: boolean;
+  loaded: boolean;
+}
+
 class PluginRegistryClass {
   private plugins = new Map<string, Plugin>();
   private states = new Map<string, PluginState>();
   private context: PluginContext | null = null;
   private listeners = new Set<() => void>();
 
+  // ── API v2 (Task A1) ─────────────────────────────────────
+  private v2Plugins = new Map<string, PluginStateV2>();
+
   /** Set the plugin context (called once on app init) */
   setContext(ctx: PluginContext) {
     this.context = ctx;
@@ -164,6 +179,96 @@ class PluginRegistryClass {
         this.enable(id);
       }
     }
+    for (const [id, state] of this.v2Plugins) {
+      if (state.plugin.manifest.enabledByDefault && !state.enabled) {
+        this.enableV2(id);
+      }
+    }
+  }
+
+  // ═══════════ API v2 (Task A1 — additiv) ═══════════
+
+  /** Registriert ein V2-Plugin. Doppelte IDs werden verworfen (Warnung). */
+  registerV2(plugin: PluginV2): void {
+    const { id } = plugin.manifest;
+    if (this.v2Plugins.has(id)) {
+      console.warn(`[PluginRegistry] V2-Plugin '${id}' bereits registriert – verworfen`);
+      return;
+    }
+    this.v2Plugins.set(id, {
+      plugin,
+      enabled: false,
+      loaded: false,
+    });
+    this.notify();
+  }
+
+  /** Entfernt ein V2-Plugin (ruft onDestroy wenn geladen). */
+  unregisterV2(pluginId: string): void {
+    const state = this.v2Plugins.get(pluginId);
+    if (!state) return;
+    if (state.loaded) state.plugin.onDestroy?.();
+    this.v2Plugins.delete(pluginId);
+    this.notify();
+  }
+
+  /** Aktiviert ein V2-Plugin (onInit einmalig, dann onActivate). */
+  enableV2(pluginId: string): void {
+    const state = this.v2Plugins.get(pluginId);
+    if (!state || state.enabled) return;
+    state.enabled = true;
+    if (!state.loaded) {
+      state.plugin.onInit?.();
+      state.loaded = true;
+    }
+    state.plugin.onActivate?.();
+    this.notify();
+  }
+
+  /** Deaktiviert ein V2-Plugin. */
+  disableV2(pluginId: string): void {
+    const state = this.v2Plugins.get(pluginId);
+    if (!state || !state.enabled) return;
+    state.enabled = false;
+    state.plugin.onDeactivate?.();
+    this.notify();
+  }
+
+  /** Ist dieses V2-Plugin aktiv? */
+  isV2Enabled(pluginId: string): boolean {
+    return this.v2Plugins.get(pluginId)?.enabled ?? false;
+  }
+
+  /** Alle Tools aus AKTIVEN V2-Plugins (flach über alle Plugins). */
+  getToolsV2(): ToolExtensionV2[] {
+    const tools: ToolExtensionV2[] = [];
+    for (const state of this.v2Plugins.values()) {
+      if (state.enabled && state.plugin.tools) tools.push(...state.plugin.tools);
+    }
+    return tools;
+  }
+
+  /** Ein bestimmtes V2-Tool per ID (nur aus aktiven Plugins). */
+  getToolV2(toolId: string): ToolExtensionV2 | undefined {
+    return this.getToolsV2().find((t) => t.manifest.id === toolId);
+  }
+
+  /** Alle Panels aktiver V2-Plugins. */
+  getPanels(): PanelExtension[] {
+    const panels: PanelExtension[] = [];
+    for (const state of this.v2Plugins.values()) {
+      if (state.enabled && state.plugin.panels) panels.push(...state.plugin.panels);
+    }
+    return panels;
+  }
+
+  /** Alle Library-Provider aktiver V2-Plugins. */
+  getLibraryProviders(): LibraryProviderExtension[] {
+    const providers: LibraryProviderExtension[] = [];
+    for (const state of this.v2Plugins.values()) {
+      if (state.enabled && state.plugin.libraryProviders) providers.push(...state.plugin.libraryProviders);
+    }
+    return providers;
   }
 }
 

frontend/src/plugins/builtin/core-annotate/index.ts

@@ -0,0 +1,141 @@
+/**
+ * core-annotate – Built-in V2-Plugin (Task A4.4).
+ *
+ * Werkzeuge: text (Platzierung — Inhalt via InlineTextEditor/PropertiesPanel,
+ * Bestandskanal onTextEdit bleibt), dimension (2-Punkt linear), leader
+ * (2-Punkt Pfeil+Label).
+ */
+import type { PluginV2, ToolExtensionV2, FullToolContext } from '../../types';
+import type { CADElement } from '../../../types/cad.types';
+import type { Pt } from '../../../tools/modification/geometry';
+
+const uid = (prefix: string): string =>
+  `${prefix}_${Date.now().toString(36)}_${Math.random().toString(36).slice(2, 9)}`;
+
+/** Gemeinsamer 2-Punkt-Sitzungsstart für dimension/leader. */
+let twoPointStart: Pt | null = null;
+
+function optsOf(ctx: FullToolContext): { stroke: string; layerId: string } {
+  return {
+    stroke: (ctx.options.strokeColor as string | undefined) ?? '#e0e0e0',
+    layerId: (ctx.options.layerId as string | undefined) ?? 'layer-0',
+  };
+}
+
+function buildDimension(start: Pt, end: Pt, ctx: FullToolContext): CADElement {
+  const o = optsOf(ctx);
+  return {
+    id: uid('dim'),
+    type: 'dimension',
+    layerId: o.layerId,
+    x: (start.x + end.x) / 2,
+    y: (start.y + end.y) / 2,
+    width: Math.hypot(end.x - start.x, end.y - start.y), // Legacy: dist als Breite
+    height: 20,
+    properties: { x1: start.x, y1: start.y, x2: end.x, y2: end.y },
+  } as unknown as CADElement;
+}
+
+function buildLeader(start: Pt, end: Pt, ctx: FullToolContext): CADElement {
+  const o = optsOf(ctx);
+  return {
+    id: uid('leader'),
+    type: 'leader',
+    layerId: o.layerId,
+    x: end.x,
+    y: end.y,
+    width: Math.abs(end.x - start.x),
+    height: Math.abs(end.y - start.y),
+    properties: { x1: start.x, y1: start.y, x2: end.x, y2: end.y, text: '', fontSize: 12, stroke: o.stroke, strokeWidth: 1 },
+  } as unknown as CADElement;
+}
+
+/** Generischer 2-Punkt-Annotate-Fluss (down→Preview→up commit). */
+function make2PointAnnotate(
+  id: 'dimension' | 'leader',
+  label: string,
+  icon: string,
+  build: (a: Pt, b: Pt, ctx: FullToolContext) => CADElement,
+): ToolExtensionV2 {
+  return {
+    manifest: { id, label, icon, ribbonTab: 'format', tags: ['basic'] },
+    optionsSchema: [{ key: 'strokeColor', label: 'Farbe', type: 'color' }],
+    handlers: {
+      down(e, ctx) {
+        twoPointStart = e.world;
+        ctx.setStatus(`${label}: Startpunkt gesetzt – Ende wählen`);
+      },
+      move(e, ctx) {
+        if (!twoPointStart) return;
+        ctx.setPreview?.(build(twoPointStart, e.world, ctx as FullToolContext));
+      },
+      up(e, ctx) {
+        const c = ctx as FullToolContext;
+        if (!twoPointStart || !c.doc) { twoPointStart = null; return; }
+        const el = build(twoPointStart, e.world, c);
+        c.doc.transact(() => c.doc!.addElement(el));
+        twoPointStart = null;
+        ctx.setPreview?.(null);
+        ctx.setStatus(`${label} erstellt (${el.id})`);
+      },
+      cancel(ctx) {
+        twoPointStart = null;
+        ctx.setPreview?.(null);
+        ctx.setStatus(`${label} abgebrochen`);
+      },
+    },
+  };
+}
+
+/**
+ * text-Werkzeug (A4.4): Klick platziert Textelement mit leerem Inhalt;
+ * Bearbeitung läuft über den bestehenden InlineTextEditor/onTextEdit-Kanal.
+ */
+export const textTool: ToolExtensionV2 = {
+  manifest: {
+    id: 'text',
+    label: 'Text',
+    icon: 'T',
+    ribbonTab: 'format',
+    tags: ['basic'],
+    description: 'Text platzieren und über Editor beschriften',
+  },
+  optionsSchema: [{ key: 'fontSize', label: 'Größe', type: 'number', min: 6, max: 72 }],
+  handlers: {
+    down(e, ctx) {
+      const c = ctx as FullToolContext;
+      if (!c.doc) return;
+      const layerId = (c.options.layerId as string | undefined) ?? 'layer-0';
+      const fontSize = (c.options.fontSize as number | undefined) ?? 12;
+      const el = {
+        id: uid('text'),
+        type: 'text',
+        layerId,
+        x: e.world.x,
+        y: e.world.y,
+        width: 100,
+        height: 20,
+        properties: { text: '', fontSize },
+      } as unknown as CADElement;
+      c.doc.transact(() => c.doc!.addElement(el));
+      ctx.setStatus(`Text platziert (${el.id}) – now via Editor`);
+    },
+  },
+};
+
+export const dimensionTool: ToolExtensionV2 = make2PointAnnotate('dimension', 'Bemaßung', '\u2194', buildDimension);
+export const leaderTool: ToolExtensionV2 = make2PointAnnotate('leader', 'Leader', '\u21b1', buildLeader);
+
+/** V2-Plugin: Beschriftung/Bemaßung (A4.4). */
+export const coreAnnotatePlugin: PluginV2 = {
+  manifest: {
+    id: 'core-annotate',
+    name: 'Beschriftung (Kern)',
+    version: '1.0.0',
+    author: 'web-cad team',
+    description: 'Text, Bemaßung, Leader (V2).',
+    category: 'tools',
+    enabledByDefault: true,
+  },
+  tools: [textTool, dimensionTool, leaderTool],
+};

frontend/src/plugins/builtin/core-drawing/index.ts

@@ -0,0 +1,428 @@
+/**
+ * core-drawing – Built-in V2-Plugin (Task A3 Pilot).
+ *
+ * Werkzeuge: line (Migrations-Pilot aus dem Legacy-Switch).
+ * Elemente werden über CADDocument committed → kollaborativ korrektes Undo.
+ *
+ * Sitzungszustand (Startpunkt der aktuellen Linie) lebt als Modul-Member,
+ * NICHT in options: Options sind geteilter UI-Store-Zustand.
+ */
+import type { PluginV2, ToolExtensionV2, FullToolContext } from '../../types';
+import type { CADElement } from '../../../types/cad.types';
+import type { Pt } from '../../../tools/modification/geometry';
+
+const uid = (prefix: string): string =>
+  `${prefix}_${Date.now().toString(36)}_${Math.random().toString(36).slice(2, 9)}`;
+
+/** Startpunkt der laufenden Linie (nur innerhalb einer down→up-Sitzung gesetzt). */
+let lineStart: Pt | null = null;
+/** Startpunkt des laufenden Rechtecks (A4.2). */
+let rectStart: Pt | null = null;
+/** Zentrum des laufenden Kreises (A4.3). */
+let circleCenter: Pt | null = null;
+/** Laufender Bogen: Phase 0=nichts, 1=Zentrum gesetzt, 2=Radius+Startwinkel gesetzt. */
+let arcPhase = 0;
+let arcCenter: Pt | null = null;
+let arcStartPt: Pt | null = null;
+/** Laufende Polyline/Polygon-Punkte; Commit per ENTER. */
+let polyPoints: Pt[] = [];
+/** Laufende RevCloud-Punkte (A4.5); Commit per ENTER. */
+let cloudPoints: Pt[] = [];
+
+function optsOf(ctx: FullToolContext): { stroke: string; layerId: string } {
+  return {
+    stroke: (ctx.options.strokeColor as string | undefined) ?? '#e0e0f0',
+    layerId: (ctx.options.layerId as string | undefined) ?? 'layer-0',
+  };
+}
+
+function buildLine(start: Pt, end: Pt, ctx: FullToolContext): CADElement {
+  const stroke = (ctx.options.strokeColor as string | undefined) ?? '#e0e0f0';
+  const layerId = (ctx.options.layerId as string | undefined) ?? 'layer-0';
+  return {
+    id: uid('line'),
+    type: 'line',
+    layerId,
+    x: (start.x + end.x) / 2,
+    y: (start.y + end.y) / 2,
+    width: Math.abs(end.x - start.x),
+    height: Math.abs(end.y - start.y),
+    properties: { x1: start.x, y1: start.y, x2: end.x, y2: end.y, stroke, strokeWidth: 1 },
+  } as unknown as CADElement;
+}
+
+function buildRect(cornerA: Pt, cornerB: Pt, ctx: FullToolContext): CADElement {
+  const stroke = (ctx.options.strokeColor as string | undefined) ?? '#e0e0f0';
+  const layerId = (ctx.options.layerId as string | undefined) ?? 'layer-0';
+  const minX = Math.min(cornerA.x, cornerB.x);
+  const minY = Math.min(cornerA.y, cornerB.y);
+  const w = Math.abs(cornerB.x - cornerA.x);
+  const h = Math.abs(cornerB.y - cornerA.y);
+  return {
+    id: uid('rect'),
+    type: 'rect',
+    layerId,
+    x: minX + w / 2,          // BBox-Zentrum (Legacy-Konvention)
+    y: minY + h / 2,
+    width: w,
+    height: h,
+    properties: { stroke, strokeWidth: 1 },
+  } as unknown as CADElement;
+}
+
+/**
+ * line-Werkzeug: down setzt Startpunkt, move zeigt Live-Vorschau,
+ * up committet via doc.transact (1 Linie = 1 Undo-Schritt).
+ */
+export const lineTool: ToolExtensionV2 = {
+  manifest: {
+    id: 'line',
+    label: 'Linie',
+    icon: '\u2571',
+    ribbonTab: 'canvas',
+    tags: ['basic'],
+    description: 'Zeichnet eine Linie (Klick Start, Klick Ende)',
+  },
+  optionsSchema: [
+    { key: 'strokeColor', label: 'Farbe', type: 'color' },
+  ],
+  handlers: {
+    down(e, ctx) {
+      lineStart = e.world;
+      ctx.setStatus(`Linie ab (${lineStart.x.toFixed(0)}, ${lineStart.y.toFixed(0)}) – Ende wählen`);
+    },
+    move(e, ctx) {
+      if (!lineStart) return;
+      ctx.setPreview?.(buildLine(lineStart, e.world, ctx));
+    },
+    up(e, ctx) {
+      const c = ctx as FullToolContext;
+      if (!lineStart || !c.doc) {
+        lineStart = null;
+        return;
+      }
+      const el = buildLine(lineStart, e.world, c);
+      c.doc.transact(() => {
+        // addElement öffnet inneres transact — Yjs verschachtelt sie → EIN Undo-Schritt
+        c.doc!.addElement(el);
+      });
+      lineStart = null;
+      ctx.setPreview?.(null);
+      ctx.setStatus(`Linie erstellt (${el.id})`);
+    },
+    cancel(ctx) {
+      lineStart = null;
+      ctx.setPreview?.(null);
+      ctx.setStatus('Linie abgebrochen');
+    },
+  },
+};
+
+/**
+ * rect-Werkzeug (A4.2): down setzt Ecke, move zeigt BBox-Vorschau,
+ * up committet via doc.transact. Portiert aus Legacy case 'rect'
+ * (BBox-Konvention: x/y = Zentrum, width/height absolut).
+ */
+export const rectTool: ToolExtensionV2 = {
+  manifest: {
+    id: 'rect',
+    label: 'Rechteck',
+    icon: '\u25ad',
+    ribbonTab: 'canvas',
+    tags: ['basic'],
+    description: 'Zieht ein Rechteck auf (Klick Ecke, Klick Gegenecke)',
+  },
+  optionsSchema: [
+    { key: 'strokeColor', label: 'Farbe', type: 'color' },
+  ],
+  handlers: {
+    down(e, ctx) {
+      rectStart = e.world;
+      ctx.setStatus(`Rechteck ab (${rectStart.x.toFixed(0)}, ${rectStart.y.toFixed(0)}) – Gegenecke wählen`);
+    },
+    move(e, ctx) {
+      if (!rectStart) return;
+      ctx.setPreview?.(buildRect(rectStart, e.world, ctx));
+    },
+    up(e, ctx) {
+      const c = ctx as FullToolContext;
+      if (!rectStart || !c.doc) {
+        rectStart = null;
+        return;
+      }
+      const el = buildRect(rectStart, e.world, c);
+      c.doc.transact(() => {
+        c.doc!.addElement(el);
+      });
+      rectStart = null;
+      ctx.setPreview?.(null);
+      ctx.setStatus(`Rechteck erstellt (${el.id})`);
+    },
+    cancel(ctx) {
+      rectStart = null;
+      ctx.setPreview?.(null);
+      ctx.setStatus('Rechteck abgebrochen');
+    },
+  },
+};
+
+/**
+ * circle-Werkzeug (A4.3): Zentrum→Radius wie Legacy (Radius = Distanz).
+ */
+export const circleTool: ToolExtensionV2 = {
+  manifest: {
+    id: 'circle', label: 'Kreis', icon: '\u25cb', ribbonTab: 'canvas', tags: ['basic'],
+    description: 'Kreis: Zentrum klicken, Radius ziehen',
+  },
+  optionsSchema: [{ key: 'strokeColor', label: 'Farbe', type: 'color' }],
+  handlers: {
+    down(e, ctx) { circleCenter = e.world; ctx.setStatus('Kreiszentrum gesetzt – Radius ziehen'); },
+    move(e, ctx) {
+      if (!circleCenter) return;
+      const r = Math.hypot(e.world.x - circleCenter.x, e.world.y - circleCenter.y);
+      ctx.setPreview?.(buildCircle(circleCenter, r, ctx));
+    },
+    up(e, ctx) {
+      const c = ctx as FullToolContext;
+      if (!circleCenter || !c.doc) { circleCenter = null; return; }
+      const r = Math.hypot(e.world.x - circleCenter.x, e.world.y - circleCenter.y);
+      const el = buildCircle(circleCenter, r, c);
+      c.doc.transact(() => c.doc!.addElement(el));
+      circleCenter = null;
+      ctx.setPreview?.(null);
+      ctx.setStatus(`Kreis erstellt (${el.id})`);
+    },
+    cancel(ctx) { circleCenter = null; ctx.setPreview?.(null); ctx.setStatus('Kreis abgebrochen'); },
+  },
+};
+
+/**
+ * arc-Werkzeug (A4.3): 3-Klick wie Legacy — Zentrum, Startpunkt (Radius+
+ * Startwinkel), Endpunkt (Endwinkel). Winkel in Grad CCW.
+ */
+export const arcTool: ToolExtensionV2 = {
+  manifest: {
+    id: 'arc', label: 'Bogen', icon: '\u2322', ribbonTab: 'canvas', tags: ['basic'],
+    description: 'Bogen: Zentrum, Startpunkt, Endpunkt',
+  },
+  optionsSchema: [{ key: 'strokeColor', label: 'Farbe', type: 'color' }],
+  handlers: {
+    down(e, ctx) {
+      const c = ctx as FullToolContext;
+      if (arcPhase === 0) {
+        arcCenter = e.world;
+        arcPhase = 1;
+        ctx.setStatus('Bogenzentrum gesetzt \u2013 Startpunkt w\u00e4hlen');
+      } else if (arcPhase === 1) {
+        arcStartPt = e.world;
+        arcPhase = 2;
+        ctx.setStatus('Bogen: Endpunkt w\u00e4hlen');
+      } else if (arcPhase === 2 && arcCenter && arcStartPt) {
+        // Dritter Klick committet (klick-progressiv wie Legacy — up feuert im
+        // echten Browser immer direkt nach down, darf deshalb NICHT committen)
+        if (!c.doc) { arcPhase = 0; arcCenter = null; arcStartPt = null; return; }
+        const el = buildArc(arcCenter, arcStartPt, e.world, c);
+        c.doc.transact(() => c.doc!.addElement(el));
+        ctx.setPreview?.(null);
+        ctx.setStatus(`Bogen erstellt (${el.id})`);
+        arcPhase = 0;
+        arcCenter = null;
+        arcStartPt = null;
+      }
+    },
+    move(e, ctx) {
+      if (arcPhase === 1 && arcCenter) {
+        const r = Math.hypot(e.world.x - arcCenter.x, e.world.y - arcCenter.y);
+        // Vollkreis-Guide in Phasen-Preview (Legacy-Konvention)
+        ctx.setPreview?.(buildArcFullGuide(arcCenter, r, ctx));
+      } else if (arcPhase === 2 && arcCenter && arcStartPt) {
+        ctx.setPreview?.(buildArc(arcCenter, arcStartPt, e.world, ctx));
+      }
+    },
+    cancel(ctx) {
+      arcPhase = 0; arcCenter = null; arcStartPt = null;
+      ctx.setPreview?.(null); ctx.setStatus('Bogen abgebrochen');
+    },
+  },
+};
+
+/**
+ * polyline-Werkzeug (A4.3): Mehrklick fügt Punkte; ENTER committet ab 2 Punkten.
+ */
+export const polylineTool: ToolExtensionV2 = makePolyTool('polyline', 'Polylinie', 2, '\u2500');
+
+/**
+ * polygon-Werkzeug (A4.3): wie Polylinie, aber geschlossen; ENTER ab 3 Punkten.
+ */
+export const polygonTool: ToolExtensionV2 = makePolyTool('polygon', 'Polygon', 3, '\u2b21');
+
+function makePolyTool(type: 'polyline' | 'polygon', label: string, minPoints: number, icon: string): ToolExtensionV2 {
+  return {
+    manifest: { id: type, label, icon, ribbonTab: 'canvas', tags: ['basic'], description: `${label}: Punkte klicken, ENTER beendet` },
+    optionsSchema: [{ key: 'strokeColor', label: 'Farbe', type: 'color' }],
+    handlers: {
+      down(e, ctx) {
+        polyPoints.push(e.world);
+        if (!isPolyType(type)) return;
+        ctx.setStatus(`${label}: ${polyPoints.length} Punkte – ENTER beendet`);
+      },
+      move(e, ctx) {
+        if (polyPoints.length === 0) return;
+        const pts = [...polyPoints, e.world];
+        ctx.setPreview?.(buildPoly(type, pts, ctx));
+      },
+      up() { /* commit nur via ENTER */ },
+      key(e, ctx) {
+        if (e.key !== 'Enter') return false;
+        if (polyPoints.length < minPoints) {
+          ctx.setStatus(`${label}: mindestens ${minPoints} Punkte nötig`);
+          return true; // konsumiert
+        }
+        const el = buildPoly(type, polyPoints, ctx as FullToolContext);
+        const doc = (ctx as FullToolContext).doc;
+        if (!doc) { resetPoly(); return true; }
+        doc.transact(() => doc.addElement(el));
+        resetPoly();
+        ctx.setPreview?.(null);
+        ctx.setStatus(`${label} erstellt (${el.id})`);
+        return true;
+      },
+      cancel(ctx) {
+        resetPoly();
+        ctx.setPreview?.(null);
+        ctx.setStatus(`${label} abgebrochen`);
+      },
+    },
+  };
+}
+
+function isPolyType(t: string): boolean {
+  return t === 'polyline' || t === 'polygon';
+}
+
+function resetPoly(): void {
+  polyPoints = [];
+}
+
+// ─── Build-Helfer A4.3 ───────────────────────────────────────
+
+function buildCircle(center: Pt, radius: number, ctx: FullToolContext): CADElement {
+  const o = optsOf(ctx);
+  return {
+    id: uid('circle'), type: 'circle', layerId: o.layerId,
+    x: center.x, y: center.y, width: radius * 2, height: radius * 2,
+    properties: { radius, stroke: o.stroke, strokeWidth: 1 },
+  } as unknown as CADElement;
+}
+
+function anglesOf(center: Pt, start: Pt, end: Pt): { radius: number; startAngle: number; endAngle: number } {
+  const radius = Math.hypot(start.x - center.x, start.y - center.y);
+  const startAngle = (Math.atan2(start.y - center.y, start.x - center.x) * 180) / Math.PI;
+  const endAngle = (Math.atan2(end.y - center.y, end.x - center.x) * 180) / Math.PI;
+  return { radius, startAngle, endAngle };
+}
+
+function buildArc(center: Pt, startPt: Pt, endPt: Pt, ctx: FullToolContext): CADElement {
+  const o = optsOf(ctx);
+  const a = anglesOf(center, startPt, endPt);
+  return {
+    id: uid('arc'), type: 'arc', layerId: o.layerId,
+    x: center.x, y: center.y, width: a.radius * 2, height: a.radius * 2,
+    properties: { radius: a.radius, startAngle: a.startAngle, endAngle: a.endAngle, stroke: o.stroke, strokeWidth: 1 },
+  } as unknown as CADElement;
+}
+
+function buildArcFullGuide(center: Pt, radius: number, ctx: FullToolContext): CADElement {
+  // Vollkreis-Vorschau als Radien-Leitfaden (Legacy-Verhalten Phase 1)
+  const o = optsOf(ctx);
+  return {
+    id: uid('arc'), type: 'circle', layerId: o.layerId,
+    x: center.x, y: center.y, width: radius * 2, height: radius * 2,
+    properties: { radius, stroke: o.stroke, strokeWidth: 1, guideOnly: true },
+  } as unknown as CADElement;
+}
+
+function buildPoly(type: 'polyline' | 'polygon', pts: Pt[], ctx: FullToolContext): CADElement {
+  const o = optsOf(ctx);
+  const xs = pts.map((p) => p.x);
+  const ys = pts.map((p) => p.y);
+  return {
+    id: uid(type), type, layerId: o.layerId,
+    x: (Math.min(...xs) + Math.max(...xs)) / 2,
+    y: (Math.min(...ys) + Math.max(...ys)) / 2,
+    width: Math.max(...xs) - Math.min(...xs),
+    height: Math.max(...ys) - Math.min(...ys),
+    properties: { points: pts.map((p) => ({ x: p.x, y: p.y })), stroke: o.stroke, strokeWidth: 1 },
+  } as unknown as CADElement;
+}
+
+/**
+ * revcloud-Werkzeug (A4.5): Mehrklick-Revisionswolke wie Poly-Muster;
+ * ENTER committet ab 3 Punkten. Legacy-Konvention: arcHeight 8.
+ */
+export const revcloudTool: ToolExtensionV2 = {
+  manifest: {
+    id: 'revcloud', label: 'RevCloud', icon: '\u2611', ribbonTab: 'format', tags: ['pro'],
+    description: 'Revisionswolke: Punkte klicken, ENTER beendet',
+  },
+  optionsSchema: [{ key: 'strokeColor', label: 'Farbe', type: 'color' }],
+  handlers: {
+    down(e, ctx) {
+      cloudPoints.push(e.world);
+      ctx.setStatus(`RevCloud: ${cloudPoints.length} Punkte \u2013 ENTER beendet`);
+    },
+    move(e, ctx) {
+      if (cloudPoints.length === 0) return;
+      ctx.setPreview?.(buildRevCloud([...cloudPoints, e.world], ctx));
+    },
+    up() { /* commit via ENTER */ },
+    key(e, ctx) {
+      if (e.key !== 'Enter') return false;
+      if (cloudPoints.length < 3) {
+        ctx.setStatus('RevCloud: mindestens 3 Punkte n\u00f6tig');
+        return true;
+      }
+      const c = ctx as FullToolContext;
+      if (!c.doc) { cloudPoints = []; return true; }
+      const el = buildRevCloud(cloudPoints, c);
+      c.doc.transact(() => c.doc!.addElement(el));
+      cloudPoints = [];
+      ctx.setPreview?.(null);
+      ctx.setStatus(`RevCloud erstellt (${el.id})`);
+      return true;
+    },
+    cancel(ctx) {
+      cloudPoints = [];
+      ctx.setPreview?.(null);
+      ctx.setStatus('RevCloud abgebrochen');
+    },
+  },
+};
+
+function buildRevCloud(pts: Pt[], ctx: FullToolContext): CADElement {
+  const o = optsOf(ctx);
+  const xs = pts.map((p) => p.x);
+  const ys = pts.map((p) => p.y);
+  return {
+    id: uid('revcloud'), type: 'revcloud', layerId: o.layerId,
+    x: (Math.min(...xs) + Math.max(...xs)) / 2,
+    y: (Math.min(...ys) + Math.max(...ys)) / 2,
+    width: Math.max(...xs) - Math.min(...xs),
+    height: Math.max(...ys) - Math.min(...ys),
+    properties: { points: pts.map((p) => ({ x: p.x, y: p.y })), arcHeight: 8, fill: 'none', stroke: '#e0e0e0', strokeWidth: 1.5 },
+  } as unknown as CADElement;
+}
+
+/** V2-Plugin: Kern-Zeichenwerkzeuge (A4.x schrittweise migriert). */
+export const coreDrawingPlugin: PluginV2 = {
+  manifest: {
+    id: 'core-drawing',
+    name: 'Zeichnen (Kern)',
+    version: '1.3.0',
+    author: 'web-cad team',
+    description: 'Zeichenwerkzeuge V2: Linie, Rechteck, Kreis, Bogen, Polylinie, Polygon, RevCloud.',
+    category: 'tools',
+    enabledByDefault: true,
+  },
+  tools: [lineTool, rectTool, circleTool, arcTool, polylineTool, polygonTool, revcloudTool],
+};

frontend/src/plugins/builtin/core-measure/index.ts

@@ -0,0 +1,60 @@
+/**
+ * core-measure – Built-in V2-Plugin (Task A4.5).
+ *
+ * measure: 2 Klicks → Distanz+Winkel-Anzeige im Status. KEIN Element-Commit
+ * (Legacy-Verhalten getreu — Messung ist Information, keine Zeichnung).
+ * Distanzformatierung via bestehendem formatDistance(unit, scaleFactor).
+ */
+import type { PluginV2, ToolExtensionV2, FullToolContext } from '../../types';
+import { formatDistance } from '../../../utils/format';
+
+type MeasurePhase = 0 | 1; // 0=wartet auf Start, 1=wartet auf Ende
+let measureStart: import('../../../tools/modification/geometry').Pt | null = null;
+
+export const measureTool: ToolExtensionV2 = {
+  manifest: {
+    id: 'measure',
+    label: 'Messen',
+    icon: '\u2194',
+    ribbonTab: 'view',
+    tags: ['basic'],
+    description: 'Distanz und Winkel zwischen zwei Punkten messen',
+  },
+  optionsSchema: [],
+  handlers: {
+    down(e, ctx) {
+      const c = ctx as FullToolContext;
+      if (!measureStart) {
+        measureStart = e.world;
+        ctx.setStatus('Messung: Endpunkt klicken');
+        return;
+      }
+      // Zweiter Klick → anzeigen (Legacy-Ausgabeformat)
+      const rawDist = Math.hypot(e.world.x - measureStart.x, e.world.y - measureStart.y);
+      const angle = (Math.atan2(e.world.y - measureStart.y, e.world.x - measureStart.x) * 180) / Math.PI;
+      const unit = (c.options.unit as string | undefined) ?? 'mm';
+      const scale = (c.options.scaleFactor as number | undefined) ?? 1;
+      const distStr = formatDistance(rawDist, unit as never, scale);
+      ctx.setStatus(`distance: ${distStr}  angle: ${angle.toFixed(1)}\u00b0`);
+      measureStart = null;
+    },
+    cancel(ctx) {
+      measureStart = null;
+      ctx.setStatus('Messung abgebrochen');
+    },
+  },
+};
+
+/** V2-Plugin: Messwerkzeuge. */
+export const coreMeasurePlugin: PluginV2 = {
+  manifest: {
+    id: 'core-measure',
+    name: 'Messen (Kern)',
+    version: '1.0.0',
+    author: 'web-cad team',
+    description: 'Abstandswinkel-Messung ohne Element-Erzeugung.',
+    category: 'tools',
+    enabledByDefault: true,
+  },
+  tools: [measureTool],
+};

frontend/src/plugins/builtin/event-tools/index.ts

@@ -0,0 +1,78 @@
+/**
+ * event-tools – Built-in V2-Plugin (Task A4.9).
+ *
+ * Fachwerkzeuge für Veranstaltungsplanung: chair, seating-row,
+ * seating-block, table, stage — alle Einzelklick-Platzierer über
+ * den (durch BUG-1-Fix korrigierten) SeatingService.
+ *
+ * Jede Platzierung = doc.transact → 1 Undo-Schritt (Multi-Element-Sets
+ * wie seating-block erscheinen/verschwinden gemeinsam).
+ */
+import type { PluginV2, ToolExtensionV2, FullToolContext } from '../../types';
+import type { CADElement } from '../../../types/cad.types';
+import { SeatingService } from '../../../services/seatingService';
+
+const seating = new SeatingService();
+
+/** Erzeugt ein Einzelklick-Platzierer-Werkzeug über einen placer. */
+function makePlaceTool(
+  id: string,
+  label: string,
+  icon: string,
+  placer: (x: number, y: number, layerId: string) => CADElement | CADElement[],
+  statusNoun: string,
+): ToolExtensionV2 {
+  return {
+    manifest: {
+      id,
+      label,
+      icon,
+      ribbonTab: 'insert',
+      tags: ['basic'],
+      description: `${statusNoun} per Klick platzieren`,
+    },
+    optionsSchema: [],
+    handlers: {
+      down(e, ctx) {
+        const c = ctx as FullToolContext;
+        if (!c.doc) return;
+        const layerId = (c.options.layerId as string | undefined) ?? 'layer-0';
+        const placed = placer(e.world.x, e.world.y, layerId);
+        const els = Array.isArray(placed) ? placed : [placed];
+        c.doc.transact(() => {
+          for (const el of els) c.doc!.addElement(el);
+        });
+        ctx.setStatus(`${statusNoun} platziert (${els.length} Element${els.length === 1 ? '' : 'e'})`);
+      },
+    },
+  };
+}
+
+export const chairTool = makePlaceTool('chair', 'Stuhl', '\u2570',
+  (x, y, layerId) => seating.createChair(x, y, layerId), 'Stuhl');
+
+export const seatingRowTool = makePlaceTool('seating-row', 'Stuhldreihe', '\u2500\u2570\u2500',
+  (x, y, layerId) => seating.createSeatingRow(x, y, layerId), 'Reihe');
+
+export const seatingBlockTool = makePlaceTool('seating-block', 'Stuhlblock', '\u2565',
+  (x, y, layerId) => seating.createSeatingBlock(x, y, layerId), 'Block');
+
+export const tableTool = makePlaceTool('table', 'Tisch', '\u25cb',
+  (x, y, layerId) => seating.createTable(x, y, layerId), 'Tisch');
+
+export const stageTool = makePlaceTool('stage', 'Bühne', '\u25ad',
+  (x, y, layerId) => seating.createStage(x, y, layerId), 'Bühne');
+
+/** V2-Plugin: Event-Domain (Task A4.9). */
+export const eventToolsV2Plugin: PluginV2 = {
+  manifest: {
+    id: 'event-tools',
+    name: 'Event-Bestuhlung',
+    version: '2.0.0',
+    author: 'web-cad team',
+    description: 'Stühle, Reihen, Blöcke, Tische, Bühne (V2).',
+    category: 'elements',
+    enabledByDefault: true,
+  },
+  tools: [chairTool, seatingRowTool, seatingBlockTool, tableTool, stageTool],
+};

frontend/src/plugins/index.ts

@@ -12,15 +12,42 @@ export type {
   CommandExtension,
   ImportExportExtension,
   PropertyField,
+  // API v2 (Task A1):
+  PluginV2,
+  ToolExtensionV2,
+  ToolManifestPart,
+  ToolPointerEvent,
+  ToolContext,
+  PanelExtension,
+  LibraryProviderExtension,
+  LibFolder,
+  LibBlock,
+  PluginCategoryV2,
 } from './types';
 
 // Built-in plugins
 export { eventToolsPlugin } from './builtin/eventTools';
+export { coreDrawingPlugin } from './builtin/core-drawing';
+export { coreModifyPlugin } from './builtin/core-modify';
+export { coreAnnotatePlugin } from './builtin/core-annotate';
+export { coreMeasurePlugin } from './builtin/core-measure';
+export { eventToolsV2Plugin } from './builtin/event-tools';
 
 import { pluginRegistry } from './PluginRegistry';
 import { eventToolsPlugin } from './builtin/eventTools';
+import { coreDrawingPlugin } from './builtin/core-drawing';
+import { coreModifyPlugin } from './builtin/core-modify';
+import { coreAnnotatePlugin } from './builtin/core-annotate';
+import { coreMeasurePlugin } from './builtin/core-measure';
+import { eventToolsV2Plugin } from './builtin/event-tools';
 
 /** Register all built-in plugins */
 export function registerBuiltinPlugins() {
   pluginRegistry.register(eventToolsPlugin);
+  // API v2 (Task A3+):
+  pluginRegistry.registerV2(coreDrawingPlugin);
+  pluginRegistry.registerV2(coreModifyPlugin);
+  pluginRegistry.registerV2(coreAnnotatePlugin);
+  pluginRegistry.registerV2(coreMeasurePlugin);
+  pluginRegistry.registerV2(eventToolsV2Plugin);
 }

frontend/src/plugins/types.ts

@@ -116,3 +116,131 @@ export interface PluginState {
   enabled: boolean;
   loaded: boolean;
 }
+
+// ═══════════════════════════════════════════════════════
+// ─── API v2 (Task A1, additiv — siehe ROADMAP TEIL 2.4) ──
+// ═══════════════════════════════════════════════════════
+import type { Pt } from '../tools/modification/geometry';
+
+/** Manifest-Teil eines V2-Werkzeugs. */
+export interface ToolManifestPart {
+  id: string;
+  label: string;
+  icon: string;
+  ribbonTab: string;
+  shortcut?: string;
+  /** 'basic' = auch im Einfach-Modus sichtbar (Task H1). */
+  tags?: Array<'basic' | 'pro'>;
+}
+
+/** Normalisiertes Pointer-Event mit Welt- und Bildschirmkoordinaten. */
+export interface ToolPointerEvent {
+  world: Pt;
+  screen: Pt;
+  button: number;
+  shift: boolean;
+  alt: boolean;
+  ctrl: boolean;
+}
+
+/** Kontext, den der Dispatcher einem aktiven V2-Tool übergibt. */
+export interface ToolContext {
+  /** Aktueller Optionsstand für dieses Tool (aus toolStore). */
+  options: Record<string, unknown>;
+  /** Statuszeilentext setzen. */
+  setStatus(msg: string): void;
+  /** Live-Vorschau setzen (null = Vorschau entfernen). Ab A3 an Renderer angebunden. */
+  setPreview?(el: CADElement | null): void;
+}
+
+/** Selektions-/Treffer-Bridge für Werkzeuge (ab A3, von CanvasArea injiziert). */
+export interface ToolSelectionBridge {
+  /** Aktuell selektierte Element-IDs. */
+  getIds(): string[];
+  /** Setzt die Selektion vollständig. */
+  setIds(ids: string[]): void;
+  /** Element-Treffer an Weltposition (oder null). */
+  hitTest(worldX: number, worldY: number, tolerancePx: number): CADElement | null;
+}
+
+/** Erweiterter Kontext für Tools mit Dokument-/Selektionszugriff (A3). */
+export interface FullToolContext extends ToolContext {
+  /** Dokumentzugriff (transact/add/update/delete). */
+  doc?: import('../kernel/document/CADDocument').CADDocument;
+  /** Selektion + HitTest-Bridge. */
+  selection?: ToolSelectionBridge;
+}
+
+/** V2-Werkzeug mit eigenen Pointer-Handlern (ersetzt langfristig ToolExtension). */
+export interface ToolExtensionV2 {
+  manifest: ToolManifestPart & { description?: string };
+  /** Optionsleisten-Schema (wiederverwendet PropertyField). */
+  optionsSchema: PropertyField[];
+  handlers: {
+    down?(e: ToolPointerEvent, ctx: ToolContext): void;
+    move?(e: ToolPointerEvent, ctx: ToolContext): void;
+    up?(e: ToolPointerEvent, ctx: ToolContext): void;
+    /** true = Tastendruck konsumiert. */
+    key?(e: KeyboardEvent, ctx: ToolContext): boolean;
+    /** ESC / Rechtsklick. */
+    cancel?(ctx: ToolContext): void;
+  };
+}
+
+/** Eigenes Sidebar-Panel eines Plugins. */
+export interface PanelExtension {
+  id: string;
+  title: string;
+  slot: 'left' | 'right';
+  render(): HTMLElement;
+}
+
+/** Ordner einer Bibliothek (LibraryProvider). */
+export interface LibFolder {
+  id: string;
+  label: string;
+  parentId: string | null;
+}
+
+/** Block einer Bibliothek (Metadaten; Payload provider-spezifisch). */
+export interface LibBlock {
+  id: string;
+  folderId: string;
+  name: string;
+  tags?: string[];
+  thumbnail?: string; // dataURL
+}
+
+/** Liefert Kataloge — Kern der Plugin-erweiterbaren Library (Phase F). */
+export interface LibraryProviderExtension {
+  id: string;
+  label: string;
+  listFolders(): Promise<LibFolder[]>;
+  listBlocks(folderId: string): Promise<LibBlock[]>;
+  getBlock(id: string): Promise<LibBlock>;
+}
+
+/** Erweiterte Manifest-Kategorie inkl. library. */
+export type PluginCategoryV2 = PluginManifest['category'] | 'library';
+
+/** Plugin-API v2 (registriert parallel zum alten Plugin-Interface). */
+export interface PluginV2 {
+  manifest: {
+    id: string;
+    name: string;
+    version: string;
+    author: string;
+    description: string;
+    category: PluginCategoryV2;
+    enabledByDefault?: boolean;
+    minAppVersion?: string;
+    permissions?: Array<'canvas' | 'network' | 'storage'>;
+  };
+  tools?: ToolExtensionV2[];
+  panels?: PanelExtension[];
+  libraryProviders?: LibraryProviderExtension[];
+  onInit?(): void;
+  onActivate?(): void;
+  onDeactivate?(): void;
+  onDestroy?(): void;
+}

frontend/src/render/mock/MockAdapter.ts

@@ -0,0 +1,123 @@
+/**
+ * MockAdapter – Headless-Implementierung des RenderAdapter (Task C1).
+ * Zeichnet nichts; protokolliert alle Aufrufe für assertions in Unit-Tests.
+ */
+import type {
+  RenderAdapter,
+  Viewport,
+  GridConfig,
+  BackgroundDrawConfig,
+  RulerConfig,
+  LayerStyle,
+  OverlayPainter,
+  SelectionState,
+} from '../types';
+import type { CADElement, CADLayer } from '../../types/cad.types';
+import type { Pt } from '../../tools/modification/geometry';
+
+export interface RecordedCall {
+  method: string;
+  args: unknown[];
+}
+
+export class MockAdapter implements RenderAdapter {
+  readonly calls: RecordedCall[] = [];
+  private canvas: HTMLCanvasElement | null = null;
+  nextHitTestResult: CADElement | null = null;
+
+  // ── Recording helper ─────────────────────────────────────
+
+  private rec(method: string, args: unknown[]): void {
+    this.calls.push({ method, args });
+  }
+
+  /** Test-Helfer: alle Aufrufe einer Methode. */
+  callsOf(method: string): RecordedCall[] {
+    return this.calls.filter((c) => c.method === method);
+  }
+
+  /** Test-Helfer: Anzahl Aufrufe einer Methode. */
+  countCalls(method: string): number {
+    return this.callsOf(method).length;
+  }
+
+  reset(): void {
+    this.calls.length = 0;
+    this.nextHitTestResult = null;
+  }
+
+  // ── RenderAdapter Implementierung (reines Recording) ─────
+
+  init(canvas: HTMLCanvasElement): void {
+    this.canvas = canvas;
+    this.rec('init', [canvas]);
+  }
+
+  resize(width: number, height: number, dpr: number): void {
+    this.rec('resize', [width, height, dpr]);
+  }
+
+  setViewport(vp: Viewport): void {
+    this.rec('setViewport', [vp]);
+  }
+
+  destroy(): void {
+    this.rec('destroy', []);
+  }
+
+  clear(color: string): void {
+    this.rec('clear', [color]);
+  }
+
+  drawGrid(cfg: GridConfig): void {
+    this.rec('drawGrid', [cfg]);
+  }
+
+  drawBackground(img: HTMLImageElement | null, cfg: BackgroundDrawConfig): void {
+    this.rec('drawBackground', [img, cfg]);
+  }
+
+  drawRuler(cfg: RulerConfig): void {
+    this.rec('drawRuler', [cfg]);
+  }
+
+  drawElement(el: CADElement, layer: CADLayer, style: LayerStyle): void {
+    this.rec('drawElement', [el, layer, style]);
+  }
+
+  removeElement(id: string): void {
+    this.rec('removeElement', [id]);
+  }
+
+  clearElements(): void {
+    this.rec('clearElements', []);
+  }
+
+  drawPreview(el: CADElement | null): void {
+    this.rec('drawPreview', [el]);
+  }
+
+  setSelection(sel: SelectionState): void {
+    this.rec('setSelection', [sel]);
+  }
+
+  setSnapPoints(pts: Array<{ x: number; y: number; type: string }>): void {
+    this.rec('setSnapPoints', [pts]);
+  }
+
+  overlay(draw: (g: OverlayPainter) => void): void {
+    const painter: OverlayPainter = {
+      line(a: Pt, b: Pt, color: string, width?: number) {},
+      rect(x: number, y: number, w: number, h: number, strokeColor: string) {},
+      circle(center: Pt, radius: number, strokeColor: string) {},
+      text(text: string, at: Pt, color: string, fontSize?: number) {},
+    };
+    draw(painter);
+    this.rec('overlay', [null]);
+  }
+
+  hitTest(world: Pt, tolerancePx: number): CADElement | null {
+    this.rec('hitTest', [world, tolerancePx]);
+    return this.nextHitTestResult;
+  }
+}

frontend/src/render/pixi/PixiRenderer.ts

@@ -0,0 +1,436 @@
+/**
+ * PixiRenderer – WebGL-Implementierung des RenderAdapter (Task C2).
+ *
+ * - PixiJS v8 wird LAZY per dynamischem import() geladen — ein Ausfall des
+ *   Pixi-Moduls (z.B. fehlendes WebGL im Headless-Browser) beeinflusst damit
+ *   NICHT den Modul-Import der App (kein weißer Screen).
+ * - async Application.init(); danach synchron nutzbar über waitForReady()
+ * - Inkrementell: gerenderte Container pro Element-ID gecacht;
+ *   removeElement/clearElements halten Cache und Szene konsistent
+ * - drawElement konsumiert die testbaren Shape-Primitives (elementDrawers)
+ */
+import type { Application, Container, Graphics, Text } from 'pixi.js';
+import type {
+  RenderAdapter,
+  Viewport,
+  GridConfig,
+  BackgroundDrawConfig,
+  RulerConfig,
+  LayerStyle,
+  OverlayPainter,
+  SelectionState,
+} from '../types';
+import type { CADElement, CADLayer } from '../../types/cad.types';
+import type { Pt } from '../../tools/modification/geometry';
+import { elementToPrimitives } from './elementDrawers';
+
+export class PixiRenderer implements RenderAdapter {
+  private app: Application | null = null;
+  private canvas: HTMLCanvasElement | null = null;
+  private root: Container | null = null;
+  private overlayLayer: Container | null = null;
+  private graphicsCache = new Map<string, Container>();
+  private viewport: Viewport = { x: 0, y: 0, scale: 1, width: 800, height: 600 };
+  private readyResolve: (() => void) | null = null;
+  private readyReject: ((err: unknown) => void) | null = null;
+  readonly ready: Promise<void>;
+  private pixiModule: typeof import('pixi.js') | null = null;
+
+  constructor() {
+    this.ready = new Promise<void>((resolve, reject) => {
+      this.readyResolve = resolve;
+      this.readyReject = reject;
+    });
+  }
+
+  /** Wartet auf Abschluss der Initialisierung; rejected bei Pixi-Fehler. */
+  async waitForReady(): Promise<void> {
+    await this.ready;
+  }
+
+  /** Task C4: true sobald setupApp fertig ist (via readyResolve gesetzt). */
+  private initialized = false;
+
+  // ── Lifecycle ────────────────────────────────────────────
+
+  init(canvas: HTMLCanvasElement): void {
+    this.canvas = canvas;
+    // LAZY-IMPORT: pixi.js wird erst jetzt geholt. Bei Fehler → ready rejected,
+    // CanvasArea deaktiviert das Overlay und die App läuft normal weiter.
+    void import('pixi.js')
+      .then((mod) => {
+        this.pixiModule = mod;
+        return this.setupApp(mod.Application, mod.Container, canvas);
+      })
+      .then(() => this.readyResolve?.())
+      .catch((err) => {
+        this.readyReject?.(err);
+      });
+  }
+
+  private setupApp(
+    ApplicationCtor: typeof Application,
+    ContainerCtor: typeof Container,
+    canvas: HTMLCanvasElement,
+  ): Promise<void> {
+    const app = new ApplicationCtor();
+    this.app = app;
+    return app.init({
+      canvas,
+      width: this.viewport.width,
+      height: this.viewport.height,
+      backgroundAlpha: 0,
+      antialias: true,
+      autoDensity: false,
+      preference: 'webgl',
+    }).then(() => {
+      if (!this.app) return;
+      const root = new ContainerCtor();
+      this.root = root;
+      this.app.stage.addChild(root);
+      const overlay = new ContainerCtor();
+      this.overlayLayer = overlay;
+      this.app.stage.addChild(overlay);
+      this.applyViewportTransform();
+      this.initialized = true;              // Task C4: fuer getDebugInfo
+    });
+  }
+
+  resize(width: number, height: number, _dpr: number): void {
+    if (!this.app?.renderer) return;
+    this.viewport.width = width;
+    this.viewport.height = height;
+    this.app.renderer.resize(width, height);
+  }
+
+  setViewport(vp: Viewport): void {
+    this.viewport = vp;
+    this.applyViewportTransform();
+  }
+
+  destroy(): void {
+    try {
+      this.app?.destroy(true, { children: true });
+    } catch {
+      // Pixi darf im Teardown nichts mehr werfen
+    }
+    this.app = null;
+    this.root = null;
+    this.overlayLayer = null;
+    this.graphicsCache.clear();
+    this.canvas = null;
+  }
+
+  // ── Basis-Zeichenoperationen ────────────────────────────
+
+  clear(_color: string): void {
+    // Hintergrund kommt vom Canvas-CSS; Pixi leert Buffer beim render.
+  }
+
+  drawGrid(cfg: GridConfig): void {
+    if (!cfg.enabled || !this.overlayLayer || !this.root) return;
+    const GraphicsCtor = this.pixiModule?.Graphics;
+    if (!GraphicsCtor) return;
+    const g = new GraphicsCtor();
+    const vp = this.viewport;
+    const worldLeft = vp.x;
+    const worldTop = vp.y;
+    const worldRight = vp.x + vp.width / vp.scale;
+    const worldBottom = vp.y + vp.height / vp.scale;
+    for (
+      let gx = Math.floor(worldLeft / cfg.size) * cfg.size;
+      gx < worldRight;
+      gx += cfg.size
+    ) {
+      g.moveTo(gx, worldTop).lineTo(gx, worldBottom)
+        .stroke({ color: cfg.color, width: 0.5 / vp.scale });
+    }
+    for (
+      let gy = Math.floor(worldTop / cfg.size) * cfg.size;
+      gy < worldBottom;
+      gy += cfg.size
+    ) {
+      g.moveTo(worldLeft, gy).lineTo(worldRight, gy)
+        .stroke({ color: cfg.color, width: 0.5 / vp.scale });
+    }
+    this.root.addChild(g);
+  }
+
+  drawBackground(_img: HTMLImageElement | null, _cfg: BackgroundDrawConfig): void {
+    // Sprite-/Texturintegration folgt in Task C3.
+  }
+
+  drawRuler(_cfg: RulerConfig): void {
+    // Lineal-Rendering folgt in Task C3.
+  }
+
+  // ── Elemente ─────────────────────────────────────────────
+
+  drawElement(el: CADElement, layer: CADLayer, _style: LayerStyle): void {
+    if (!this.root || !layer.visible || layer.locked) return;
+    this.removeElement(el.id);
+    const container = this.buildGraphicsContainer(el);
+    if (!container) return;
+    this.graphicsCache.set(el.id, container);
+    this.root.addChild(container);
+  }
+
+  removeElement(id: string): void {
+    const existing = this.graphicsCache.get(id);
+    if (!existing) return;
+    try {
+      existing.destroy({ children: true });
+    } catch {
+      // teardown-safe
+    }
+    this.graphicsCache.delete(id);
+  }
+
+  clearElements(): void {
+    for (const c of this.graphicsCache.values()) {
+      try {
+        c.destroy({ children: true });
+      } catch {
+        // teardown-safe
+      }
+    }
+    this.graphicsCache.clear();
+  }
+
+  drawPreview(el: CADElement | null): void {
+    if (!this.overlayLayer) return;
+    for (const child of [...this.overlayLayer.children]) {
+      if ((child as Container).label === '__preview__') {
+        try {
+          child.destroy({ children: true });
+        } catch {
+          // teardown-safe
+        }
+      }
+    }
+    if (!el) return;
+    const g = this.buildGraphicsContainer(el);
+    if (g) {
+      g.label = '__preview__';
+      g.alpha = 0.6;
+      this.overlayLayer.addChild(g);
+    }
+  }
+
+  setSelection(sel: SelectionState): void {
+    if (!this.overlayLayer) return;
+    // Bestehende Selektions-Grafik entfernen:
+    for (const child of [...this.overlayLayer.children]) {
+      if ((child as Container).label === '__selection__') {
+        try {
+          child.destroy({ children: true });
+        } catch {
+          // teardown-safe
+        }
+      }
+    }
+    if (!sel.selectedIds.length || !sel.elements || !this.pixiModule) return;
+
+    const GraphicsCtor = this.pixiModule.Graphics;
+    const g = new GraphicsCtor();
+    const HANDLE = 4; // halbe Kantenlänge der Eck-Handles (in Weltkoordinaten)
+
+    for (const el of sel.elements) {
+      if (!sel.selectedIds.includes(el.id)) continue;
+      // Legacy-Konvention getElementBBox: x/y = Zentrum für rects, sonst BBox
+      let minX: number, minY: number, maxX: number, maxY: number;
+      if (el.type === 'rect' || el.type === 'stage') {
+        minX = el.x - el.width / 2;
+        minY = el.y - el.height / 2;
+        maxX = el.x + el.width / 2;
+        maxY = el.y + el.height / 2;
+      } else if (
+        el.properties &&
+        el.properties.x1 !== undefined && el.properties.y1 !== undefined &&
+        el.properties.x2 !== undefined && el.properties.y2 !== undefined
+      ) {
+        minX = Math.min(el.properties.x1 as number, el.properties.x2 as number);
+        minY = Math.min(el.properties.y1 as number, el.properties.y2 as number);
+        maxX = Math.max(el.properties.x1 as number, el.properties.x2 as number);
+        maxY = Math.max(el.properties.y1 as number, el.properties.y2 as number);
+      } else {
+        minX = el.x - el.width / 2;
+        minY = el.y - el.height / 2;
+        maxX = el.x + el.width / 2;
+        maxY = el.y + el.height / 2;
+      }
+
+      // Umrandung (gestrichelt wird via Linien-Segmenten simuliert):
+      const dashLen = 6;
+      const drawDashed = (ax: number, ay: number, bx: number, by: number) => {
+        const len = Math.hypot(bx - ax, by - ay);
+        const n = Math.max(1, Math.floor(len / dashLen));
+        for (let i = 0; i <= n; i += 2) {
+          const t0 = i / n;
+          const t1 = Math.min(1, (i + 1) / n);
+          g.moveTo(ax + (bx - ax) * t0, ay + (by - ay) * t0)
+            .lineTo(ax + (bx - ax) * t1, ay + (by - ay) * t1)
+            .stroke({ color: '#50fa7b', width: 1 / this.viewport.scale });
+        }
+      };
+      drawDashed(minX, minY, maxX, minY);
+      drawDashed(maxX, minY, maxX, maxY);
+      drawDashed(maxX, maxY, minX, maxY);
+      drawDashed(minX, maxY, minX, minY);
+
+      // 4 Eck-Handles (gefüllte Quadrate):
+      const corners = [
+        { x: minX, y: minY }, { x: maxX, y: minY },
+        { x: maxX, y: maxY }, { x: minX, y: maxY },
+      ];
+      for (const c of corners) {
+        g.rect(c.x - HANDLE, c.y - HANDLE, HANDLE * 2, HANDLE * 2)
+          .fill({ color: '#50fa7b' })
+          .stroke({ color: '#1e1e2e', width: 1 / this.viewport.scale });
+      }
+    }
+    g.label = '__selection__';
+    this.overlayLayer.addChild(g);
+  }
+
+  setSnapPoints(pts: Array<{ x: number; y: number; type: string }>): void {
+    if (!this.overlayLayer || !this.pixiModule || pts.length === 0) return;
+    const GraphicsCtor = this.pixiModule.Graphics;
+    const g = new GraphicsCtor();
+    g.label = '__snaps__';
+    // Bestehende Snap-Marks entfernen:
+    for (const child of [...this.overlayLayer.children]) {
+      if ((child as Container).label === '__snaps__') {
+        try {
+          child.destroy({ children: true });
+        } catch {
+          // teardown-safe
+        }
+      }
+    }
+    // Snap-Punkt farbig nach Typ (Legacy-Ähnlich):
+    const colorByType: Record<string, string> = {
+      endpoint: '#ff79c6',
+      midpoint: '#8be9fd',
+      center: '#f1fa8c',
+      intersection: '#ffb86c',
+      grid: '#6272a4',
+    };
+    const scaleComp = 1 / this.viewport.scale; // konstante Bildschirmgröße
+    for (const pt of pts) {
+      const color = colorByType[pt.type] ?? '#bd93f9';
+      g.circle(pt.x, pt.y, 4 * scaleComp)
+        .fill({ color })
+        .stroke({ color: '#1e1e2e', width: 1 * scaleComp });
+    }
+    this.overlayLayer.addChild(g);
+  }
+
+  overlay(draw: (g: OverlayPainter) => void): void {
+    if (!this.overlayLayer) return;
+    const GraphicsCtor = this.pixiModule?.Graphics;
+    const TextCtor = this.pixiModule?.Text;
+    if (!GraphicsCtor || !TextCtor) return;
+    const g = new GraphicsCtor();
+    const painter: OverlayPainter = {
+      line: (a: Pt, b: Pt, color: string, width?: number) => {
+        g.moveTo(a.x, a.y).lineTo(b.x, b.y).stroke({ color, width: width ?? 1 });
+      },
+      rect: (x: number, y: number, w: number, h: number, strokeColor: string) => {
+        g.rect(x, y, w, h).stroke({ color: strokeColor });
+      },
+      circle: (center: Pt, radius: number, strokeColor: string) => {
+        g.circle(center.x, center.y, radius).stroke({ color: strokeColor });
+      },
+      text: (text: string, at: Pt, color: string, fontSize?: number) => {
+        const t = new TextCtor({ text, style: { fontSize: fontSize ?? 12, fill: color } });
+        t.position.set(at.x, at.y);
+        g.addChild(t);
+      },
+    };
+    draw(painter);
+    this.overlayLayer.addChild(g);
+  }
+
+  hitTest(_world: Pt, _tolerancePx: number): CADElement | null {
+    // Delegation an SpatialIndex folgt in C3.
+    return null;
+  }
+
+  /**
+   * Task C4: Debug-Info für Playwright-E2E-Assertions.
+   * Ermöglicht Testabfragen wie 'wie viele Elemente sind gerendert?'
+   */
+  getDebugInfo(): { cachedElements: number; ready: boolean } {
+    return {
+      cachedElements: this.graphicsCache.size,
+      ready: this.initialized,
+    };
+  }
+
+  // ── Internes ─────────────────────────────────────────────
+
+  private applyViewportTransform(): void {
+    if (!this.root) return;
+    this.root.position.set(
+      -this.viewport.x * this.viewport.scale,
+      -this.viewport.y * this.viewport.scale,
+    );
+    this.root.scale.set(this.viewport.scale);
+  }
+
+  private buildGraphicsContainer(el: CADElement): Container | null {
+    const prims = elementToPrimitives(el);
+    if (prims.length === 0) return null;
+    const GraphicsCtor = this.pixiModule?.Graphics;
+    const TextCtor = this.pixiModule?.Text;
+    if (!GraphicsCtor || !TextCtor) return null;
+    const ContainerCtor = this.pixiModule!.Container;
+    const container = new ContainerCtor();
+    for (const prim of prims) {
+      const g = new GraphicsCtor();
+      switch (prim.kind) {
+        case 'line':
+          g.moveTo(prim.from.x, prim.from.y)
+            .lineTo(prim.to.x, prim.to.y)
+            .stroke({ color: prim.stroke, width: prim.strokeWidth });
+          break;
+        case 'rect':
+          g.rect(prim.x, prim.y, prim.w, prim.h);
+          if (prim.fill) g.fill({ color: prim.fill });
+          g.stroke({ color: prim.stroke, width: prim.strokeWidth });
+          break;
+        case 'circle':
+          g.circle(prim.center.x, prim.center.y, prim.radius);
+          if (prim.fill) g.fill({ color: prim.fill });
+          g.stroke({ color: prim.stroke, width: prim.strokeWidth });
+          break;
+        case 'polyline': {
+          if (prim.points.length === 0) break;
+          g.moveTo(prim.points[0].x, prim.points[0].y);
+          for (let i = 1; i < prim.points.length; i++) {
+            g.lineTo(prim.points[i].x, prim.points[i].y);
+          }
+          if (prim.close) g.closePath();
+          g.stroke({ color: prim.stroke, width: prim.strokeWidth });
+          break;
+        }
+        case 'arc': {
+          const startRad = (prim.startDeg * Math.PI) / 180;
+          const endRad = (prim.endDeg * Math.PI) / 180;
+          g.arc(prim.center.x, prim.center.y, prim.radius, startRad, endRad)
+            .stroke({ color: prim.stroke, width: prim.strokeWidth });
+          break;
+        }
+        case 'text': {
+          const t = new TextCtor({ text: prim.text, style: { fontSize: prim.fontSize, fill: prim.color } });
+          t.position.set(prim.at.x, prim.at.y);
+          g.addChild(t);
+          break;
+        }
+      }
+      container.addChild(g);
+    }
+    return container;
+  }
+}

frontend/src/render/pixi/elementDrawers.ts

@@ -0,0 +1,242 @@
+/**
+ * elementDrawers – Reine Beschreibungs-Fabrik (Task C2).
+ *
+ * Wandelt CADElemente in eine Liste von Primitiven um (line/rect/circle/
+ * polyline/text/arc). Der PixiRenderer (C3) konsumiert diese Deskriptoren
+ * und überführt sie in konkrete Grafikobjekte.
+ *
+ * Vorteil dieser Zwischenschicht:
+ * - Vollständig unit-testbar OHNE WebGL/GPU
+ * - Backend-unabhängig (Pixi jetzt, Canvas2D oder andere später)
+ *
+ * Konventionen entsprechen dem Legacy RenderEngine.draw*:
+ * - rect: x/y = Zentrum der BBox
+ * - circle/arc: radius über properties.radius (Fallback width/2)
+ * - arc-Winkel in Grad, 0° = 3 Uhr, gegen den Uhrzeigersinn
+ */
+import type { CADElement } from '../../types/cad.types';
+import type { Pt } from '../../tools/modification/geometry';
+
+/** Zeichenprimitiv — kleinste darstellbare Einheit. */
+export type ShapePrimitive =
+  | { kind: 'line'; from: Pt; to: Pt; stroke: string; strokeWidth: number }
+  | { kind: 'rect'; x: number; y: number; w: number; h: number; fill: string | null; stroke: string; strokeWidth: number }
+  | { kind: 'circle'; center: Pt; radius: number; fill: string | null; stroke: string; strokeWidth: number }
+  | { kind: 'polyline'; points: Pt[]; close: boolean; stroke: string; strokeWidth: number }
+  | { kind: 'text'; at: Pt; text: string; fontSize: number; color: string }
+  | { kind: 'arc'; center: Pt; radius: number; startDeg: number; endDeg: number; stroke: string; strokeWidth: number };
+
+const FALLBACK_STROKE = '#e0e0e0';
+
+function asPoint(p: unknown): Pt {
+  const q = p as { x?: number; y?: number };
+  return { x: Number(q?.x ?? 0), y: Number(q?.y ?? 0) };
+}
+
+function fillOrNull(raw: unknown): string | null {
+  return typeof raw === 'string' && raw !== 'none' ? raw : null;
+}
+
+/**
+ * Wandelt ein CADElement in seine Zeichenprimitive um.
+ * Gibt ein leeres Array zurück für unbekannte Typen bzw. Elemente,
+ * die nichts Sichtbares beitragen (z.B. leerer Text).
+ */
+export function elementToPrimitives(el: CADElement): ShapePrimitive[] {
+  const props = (el.properties ?? {}) as Record<string, unknown>;
+  const stroke = (props.stroke as string | undefined) ?? FALLBACK_STROKE;
+  const sw = (props.strokeWidth as number | undefined) ?? 1;
+
+  switch (el.type) {
+    case 'line': {
+      if (
+        props.x1 === undefined || props.y1 === undefined ||
+        props.x2 === undefined || props.y2 === undefined
+      ) {
+        return [];
+      }
+      return [{
+        kind: 'line',
+        from: { x: props.x1 as number, y: props.y1 as number },
+        to: { x: props.x2 as number, y: props.y2 as number },
+        stroke,
+        strokeWidth: sw,
+      }];
+    }
+
+    case 'rect': {
+      // Legacy-BBox-Konvention: x/y ist das Zentrum des Rechtecks
+      return [{
+        kind: 'rect',
+        x: el.x - el.width / 2,
+        y: el.y - el.height / 2,
+        w: el.width,
+        h: el.height,
+        fill: fillOrNull(props.fill),
+        stroke,
+        strokeWidth: sw,
+      }];
+    }
+
+    case 'circle': {
+      const radius = (props.radius as number | undefined) ?? el.width / 2;
+      return [{
+        kind: 'circle',
+        center: { x: el.x, y: el.y },
+        radius,
+        fill: fillOrNull(props.fill),
+        stroke,
+        strokeWidth: sw,
+      }];
+    }
+
+    case 'arc': {
+      const radius = (props.radius as number | undefined) ?? el.width / 2;
+      return [{
+        kind: 'arc',
+        center: { x: el.x, y: el.y },
+        radius,
+        startDeg: (props.startAngle as number | undefined) ?? 0,
+        endDeg: (props.endAngle as number | undefined) ?? 360,
+        stroke,
+        strokeWidth: sw,
+      }];
+    }
+
+    case 'polyline':
+    case 'polygon': {
+      const pts = Array.isArray(props.points)
+        ? (props.points as unknown[]).map(asPoint)
+        : [];
+      if (pts.length < 2) return [];
+      return [{
+        kind: 'polyline',
+        points: pts,
+        close: el.type === 'polygon',
+        stroke,
+        strokeWidth: sw,
+      }];
+    }
+
+    case 'text': {
+      const txt = String(props.text ?? '');
+      if (!txt) return []; // leeren Platzhalter nicht rendern
+      return [{
+        kind: 'text',
+        at: { x: el.x, y: el.y },
+        text: txt,
+        fontSize: (props.fontSize as number | undefined) ?? 12,
+        color: (props.color as string | undefined) ?? stroke,
+      }];
+    }
+
+    // ── Task C3: bisher im Pixi-Pfad fehlende Typen ──
+
+    case 'dimension': {
+      // Legacy-Konvention: x1..y2 in properties, BBox-Zentrum als x/y,
+      // Extension lines + Hauptlinie; Pfeilspitzen sind Detail (C3+)
+      const x1 = (props.x1 as number | undefined) ?? el.x - el.width / 2;
+      const y1 = (props.y1 as number | undefined) ?? el.y;
+      const x2 = (props.x2 as number | undefined) ?? el.x + el.width / 2;
+      const y2 = (props.y2 as number | undefined) ?? el.y;
+      const color = (props.color as string | undefined) ?? '#aaaaaa';
+      const dimColor = (props.dimColor as string | undefined) ?? color;
+      const label = String(props.value ?? props.text ?? '');
+      const out: ShapePrimitive[] = [
+        { kind: 'line', from: { x: x1, y: y1 }, to: { x: x2, y: y2 }, stroke: dimColor, strokeWidth: 1 },
+      ];
+      if (label) {
+        out.push({
+          kind: 'text',
+          at: { x: (x1 + x2) / 2, y: (y1 + y2) / 2 - 12 },
+          text: label,
+          fontSize: 10,
+          color: dimColor,
+        });
+      }
+      return out;
+    }
+
+    case 'leader': {
+      // Legacy-Konvention: Linie p1→p2 + optionaler Text am Ende
+      const lx1 = (props.x1 as number | undefined) ?? el.x;
+      const ly1 = (props.y1 as number | undefined) ?? el.y;
+      const lx2 = (props.x2 as number | undefined) ?? el.x + el.width;
+      const ly2 = (props.y2 as number | undefined) ?? el.y + el.height;
+      const out: ShapePrimitive[] = [
+        { kind: 'line', from: { x: lx1, y: ly1 }, to: { x: lx2, y: ly2 }, stroke, strokeWidth: sw },
+      ];
+      const label = String(props.text ?? '');
+      if (label) {
+        out.push({
+          kind: 'text',
+          at: { x: lx2 + 4, y: ly2 - 4 },
+          text: label,
+          fontSize: (props.fontSize as number | undefined) ?? 12,
+          color: stroke,
+        });
+      }
+      return out;
+    }
+
+    case 'revcloud': {
+      // Revisionswolke: Punkte-Zug (Bogen-Detail folgt in C3+)
+      const pts = Array.isArray(props.points)
+        ? (props.points as unknown[]).map(asPoint)
+        : [];
+      if (pts.length < 2) return [];
+      return [{
+        kind: 'polyline',
+        points: pts,
+        close: true,
+        stroke,
+        strokeWidth: sw,
+      }];
+    }
+
+    case 'chair': {
+      // Stuhl: gefülltes Quadrat in Element-Farbe + Umrandung
+      const fill = (props.fill as string | undefined) ?? '#4a90d9';
+      return [{
+        kind: 'rect',
+        x: el.x - el.width / 2,
+        y: el.y - el.height / 2,
+        w: el.width,
+        h: el.height,
+        fill,
+        stroke: (props.outlineColor as string | undefined) ?? '#2a5a99',
+        strokeWidth: 1,
+      }];
+    }
+
+    case 'table': {
+      // Tisch: Kreis in Element-Größe mit Füllung
+      const fill = (props.fill as string | undefined) ?? '#8b7355';
+      return [{
+        kind: 'circle',
+        center: { x: el.x, y: el.y },
+        radius: Math.max(el.width, el.height) / 2,
+        fill,
+        stroke: '#5a4a35',
+        strokeWidth: 1,
+      }];
+    }
+
+    case 'stage': {
+      // Bühne: Rechteck mit dunkler Füllung
+      return [{
+        kind: 'rect',
+        x: el.x - el.width / 2,
+        y: el.y - el.height / 2,
+        w: el.width,
+        h: el.height,
+        fill: (props.fill as string | undefined) ?? '#3a3a4a',
+        stroke,
+        strokeWidth: 1.5,
+      }];
+    }
+
+    default:
+      return [];
+  }
+}

frontend/src/render/types.ts

@@ -0,0 +1,123 @@
+/**
+ * render/types.ts – RenderAdapter-Schnittstelle (Task C1).
+ *
+ * Ziel-Architektur: ALLES Rendering läuft gegen diese schmale API.
+ * Implementierungen:
+ *   - render/pixi/PixiRenderer.ts (WebGL, Task C2+)
+ *   - tests/helpers/mockAdapter.ts (Headless-Recorder für Unit-Tests)
+ *
+ * Phase D/E-Erweiterungen (Plugins, Custom-Elemente) nutzen denselben Vertrag
+ * über drawOverlay/drawCustom.
+ */
+import type { CADElement, CADLayer } from '../types/cad.types';
+import type { Pt } from '../tools/modification/geometry';
+
+/** Aktueller Ausschnitt in Weltkoordinaten + Skalierung. */
+export interface Viewport {
+  x: number;
+  y: number;
+  scale: number;
+  width: number;
+  height: number;
+}
+
+/** Zeichenraster-Konfiguration. */
+export interface GridConfig {
+  enabled: boolean;
+  size: number;
+  color: string;
+}
+
+/** Hintergrundbild-Konfiguration (Spiegelung der Legacy RenderOptions-Felder). */
+export interface BackgroundDrawConfig {
+  src?: string;
+  opacity?: number;
+  offsetX?: number;
+  offsetY?: number;
+  scale?: number;
+  rotation?: number;
+}
+
+/** Lineal-Konfiguration. */
+export interface RulerConfig {
+  enabled: boolean;
+  unit: string;
+  scaleFactor: number;
+}
+
+/** Stil pro CAD-Layer (Farbe/Linientyp/Transparenz). */
+export interface LayerStyle {
+  color: string;
+  lineType: string;
+  transparency: number;
+  visible: boolean;
+}
+
+/** Freihand-Zeichner für temporäre Overlays (Marquee, Tool-Hilfslinien). */
+export interface OverlayPainter {
+  line(a: Pt, b: Pt, color: string, width?: number): void;
+  rect(x: number, y: number, w: number, h: number, strokeColor: string): void;
+  circle(center: Pt, radius: number, strokeColor: string): void;
+  text(text: string, at: Pt, color: string, fontSize?: number): void;
+}
+
+/** Selektionszustand für die Anzeige von Handles. */
+export interface SelectionState {
+  selectedIds: string[];
+  /** Task C3-Finish: Elemente für Handle-Zeichnung (Renderer braucht BBox). */
+  elements?: CADElement[];
+}
+
+/**
+ * Der zentrale Rendervertrag. Implementierungen MÜSSEN alle Methoden bereitstellen,
+ * auch wenn einzelne initial No-Ops sind (z.B. drawBackground ohne Bild).
+ */
+export interface RenderAdapter {
+  /** Bindet den Renderer an ein Canvas-Element (einmalig). */
+  init(canvas: HTMLCanvasElement): void;
+
+  /** Reaktion auf Größenänderungen (DPR-bewusst). */
+  resize(width: number, height: number, dpr: number): void;
+
+  /** Setzt den aktuellen Ausschnitt; danach ist ein neuer Frame nötig. */
+  setViewport(vp: Viewport): void;
+
+  /// Gibt WebGL-/DOM-Ressourcen frei. */
+  destroy(): void;
+
+  /** Leert die Zeichenfläche mit einer Grundfarbe. */
+  clear(color: string): void;
+
+  /** Zeichnet das Raster. */
+  drawGrid(cfg: GridConfig): void;
+
+  /** Zeichnet das Hintergrundbild, falls konfiguriert. */
+  drawBackground(img: HTMLImageElement | null, cfg: BackgroundDrawConfig): void;
+
+  /** Zeichnet das Lineal. */
+  drawRuler(cfg: RulerConfig): void;
+
+  /** Zeichnet ein Element im Kontext seines Layers (Stil, Sichtbarkeit). */
+  drawElement(el: CADElement, layer: CADLayer, style: LayerStyle): void;
+
+  /** Entfernt ein Element aus dem Rendering (z.B. nach Löschen in Yjs). */
+  removeElement(id: string): void;
+
+  /** Entfernt ALLE gerenderten Elemente (Reset bei Dokumentwechsel). */
+  clearElements(): void;
+
+  /** Zeichnet ein Element in Transformation / Live-Vorschau. */
+  drawPreview(el: CADElement | null): void;
+
+  /** Synchronisiert die Selektionsanzeige (Handles, Umrandungen). */
+  setSelection(sel: SelectionState): void;
+
+  /** Snap-Markierungen setzen/entfernen. */
+  setSnapPoints(pts: Array<{ x: number; y: number; type: string }>): void;
+
+  /** Öffnet einen Overlay-Pass für freihand-Overlays (Tools). */
+  overlay(draw: (g: OverlayPainter) => void): void;
+
+  /** Treffer abfragen (Delegation an SpatialIndex; kein GPU-Picking). */
+  hitTest(world: Pt, tolerancePx: number): CADElement | null;
+}

frontend/src/services/seatingService.ts

@@ -159,6 +159,13 @@ export const SEATING_TEMPLATES: SeatingTemplate[] = [
   },
 ];
 
+let seqCounter = 0;
+/** Eindeutige, kollisionsfreie ID mit Präfix (Zeit + Sequenz + Zufall). */
+function nextUid(prefix: string): string {
+  seqCounter += 1;
+  return `${prefix}_${Date.now().toString(36)}_${seqCounter.toString(36)}_${Math.random().toString(36).slice(2, 8)}`;
+}
+
 export class SeatingService {
   private generateId(): string {
     return `el_${Date.now()}_${Math.random().toString(36).slice(2, 9)}`;
@@ -189,6 +196,7 @@ export class SeatingService {
   createSeatingRow(x: number, y: number, layerId: string, config: Partial<SeatingRowConfig> = {}): CADElement[] {
     const cfg = { ...DEFAULT_ROW, ...config };
     const elements: CADElement[] = [];
+    const rowId = nextUid('row');
     const totalWidth = (cfg.count - 1) * cfg.spacing + cfg.chairWidth;
     const startX = x - totalWidth / 2 + cfg.chairWidth / 2;
 
@@ -217,7 +225,7 @@ export class SeatingService {
           outlineColor: '#2a5a99',
           seatType: 'standard',
           rowIndex: i,
-          rowId: `row_${Date.now()}`,
+          rowId,
         },
       });
     }
@@ -233,9 +241,10 @@ export class SeatingService {
     const startX = x - totalW / 2 + cfg.chairWidth / 2;
     const startY = y - totalH / 2 + cfg.chairHeight / 2;
     const rot = cfg.rotation * Math.PI / 180;
-    const blockId = `block_${Date.now()}`;
+    const blockId = nextUid('block');
 
     for (let row = 0; row < cfg.rows; row++) {
+      const rowId = nextUid('row');
       const offset = cfg.rowOffset * (row % 2);
       for (let col = 0; col < cfg.cols; col++) {
         const lx = startX + col * cfg.colSpacing + offset;
@@ -263,6 +272,7 @@ export class SeatingService {
             rowIndex: row,
             colIndex: col,
             blockId,
+            rowId,
           },
         });
       }
@@ -342,8 +352,18 @@ export class SeatingService {
     return [];
   }
 
-  /** Count seats in a list of elements */
-  countSeats(elements: CADElement[]): { total: number; byRow: Record<string, number>; byBlock: Record<string, number> } {
+/**
+ * Zählt Sitzplätze gruppiert nach Reihe und Block.
+ * byRow enthält Reihen aus freien Reihen UND Block-Reihen (seit BUG-1-Fix
+ * tragen Block-Stühle pro Reihe eine eigene rowId).
+ */
+  countSeats(elements: CADElement[]): {
+    total: number;
+    byRow: Record<string, number>;
+    byBlock: Record<string, number>;
+    /** Platzhalter für künftige Zonen-Gruppierung (aktuell immer leer). */
+    byZone?: Record<string, number>;
+  } {
     let total = 0;
     const byRow: Record<string, number> = {};
     const byBlock: Record<string, number> = {};

frontend/src/tools/modification/geometry.ts

@@ -163,7 +163,14 @@ export function mirrorElement(el: CADElement, x1: number, y1: number, x2: number
  * Offset element by a distance (creates a parallel copy).
  * For lines: offset perpendicular. For circles/arcs: adjust radius.
  */
-export function offsetElement(el: CADElement, distance: number): CADElement {
+/**
+ * Versetzt ein Element senkrecht zur seiner Richtung.
+ * @param distance positiver Betrag des Versatzes
+ * @param side 1 = links der Laufrichtung (Standard), -1 = rechts —
+ *              bei circle/arc: 1 = Radius vergrößern, -1 = verkleinern
+ */
+export function offsetElement(el: CADElement, distance: number, side?: 1 | -1): CADElement {
+  const signed = distance * (side ?? 1);
   const props = { ...el.properties };
 
   if (el.type === 'line' && props.x1 !== undefined && props.y1 !== undefined && props.x2 !== undefined && props.y2 !== undefined) {
@@ -174,8 +181,8 @@ export function offsetElement(el: CADElement, distance: number): CADElement {
     // Perpendicular unit vector
     const nx = -dy / len;
     const ny = dx / len;
-    const ox = nx * distance;
-    const oy = ny * distance;
+    const ox = nx * signed;
+    const oy = ny * signed;
     props.x1 += ox;
     props.y1 += oy;
     props.x2 += ox;
@@ -184,7 +191,7 @@ export function offsetElement(el: CADElement, distance: number): CADElement {
   }
 
   if ((el.type === 'circle' || el.type === 'arc') && props.radius !== undefined) {
-    props.radius = Math.abs(props.radius + distance);
+    props.radius = Math.abs(props.radius + signed);
     const d = props.radius * 2;
     return { ...el, width: d, height: d, properties: props };
   }
@@ -201,7 +208,7 @@ export function offsetElement(el: CADElement, distance: number): CADElement {
       if (len === 0) return p;
       const nx = -dy / len;
       const ny = dx / len;
-      return { x: p.x + nx * distance, y: p.y + ny * distance };
+      return { x: p.x + nx * signed, y: p.y + ny * signed };
     });
     return { ...el, properties: props };
   }
@@ -215,7 +222,15 @@ export function offsetElement(el: CADElement, distance: number): CADElement {
  */
 export function trimElement(el: CADElement, boundary: CADElement): CADElement | null {
   // Simplified: find intersection with boundary, trim line to that point
-  if (el.type !== 'line' || !el.properties.x1 || !el.properties.x2) return null;
+  // Hinweis: explizit auf undefined prüfen — Koordinate 0 ist gültig (nicht falsy behandeln)
+  const p = el.properties;
+  if (
+    el.type !== 'line' ||
+    p.x1 === undefined || p.y1 === undefined ||
+    p.x2 === undefined || p.y2 === undefined
+  ) {
+    return null;
+  }
 
   const intersect = findIntersection(el, boundary);
   if (!intersect) return null;
@@ -247,10 +262,60 @@ export function trimElement(el: CADElement, boundary: CADElement): CADElement |
  * Currently supports extending lines to a boundary intersection.
  */
 export function extendElement(el: CADElement, boundary: CADElement): CADElement | null {
-  if (el.type !== 'line' || !el.properties.x1 || !el.properties.x2) return null;
+  // Explizit auf undefined prüfen — Koordinate 0 ist gültig (nicht falsy behandeln)
+  const p = el.properties;
+  if (
+    el.type !== 'line' ||
+    p.x1 === undefined || p.y1 === undefined ||
+    p.x2 === undefined || p.y2 === undefined
+  ) {
+    return null;
+  }
 
-  const intersect = findIntersection(el, boundary);
-  if (!intersect) return null;
+  let intersect = findIntersection(el, boundary);
+
+  // Echtes CAD-Extend (Fallback): Wenn die Strecke die Kante NICHT berührt,
+  // suche Schnitte auf der VERLÄNGERUNG der Linie in Richtung des nahen Endes.
+  if (!intersect) {
+    const c = { x: boundary.x, y: boundary.y };
+    const r =
+      boundary.type === 'circle' || boundary.type === 'arc'
+        ? ((boundary.properties?.radius as number | undefined) ?? boundary.width / 2)
+        : null;
+    if (r === null) return null; // nur Kreis/Bogen-Kanten erweiterbar
+
+    const candidates = lineCircleIntersectionsInfinite(
+      { x: p.x1!, y: p.y1! },
+      { x: p.x2!, y: p.y2! },
+      c,
+      r as number,
+    );
+    if (candidates.length === 0) return null;
+
+    // Wähle den Schnittpunkt, der an der Seite des NÄHEREN Endes liegt:
+    // Erst feststellen, welches Ende näher am Kreiszentrum liegt → dieses wird gestreckt.
+    const d1 = Math.hypot(p.x1! - c.x, p.y1! - c.y);
+    const d2 = Math.hypot(p.x2! - c.x, p.y2! - c.y);
+    const nearerIsStart = d1 <= d2;
+    const anchor = nearerIsStart ? { x: p.x1!, y: p.y1! } : { x: p.x2!, y: p.y2! };
+    intersect = candidates.reduce((best, cur) =>
+      Math.hypot(cur.x - anchor.x, cur.y - anchor.y) < Math.hypot(best.x - anchor.x, best.y - anchor.y) ? cur : best,
+    );
+
+    // Neu berechnete bbox/center auf Basis der Länge nach dem Strekken:
+    const nx1 = nearerIsStart ? intersect.x : p.x1!;
+    const ny1 = nearerIsStart ? intersect.y : p.y1!;
+    const nx2 = nearerIsStart ? p.x2! : intersect.x;
+    const ny2 = nearerIsStart ? p.y2! : intersect.y;
+    return {
+      ...el,
+      x: (nx1 + nx2) / 2,
+      y: (ny1 + ny2) / 2,
+      width: Math.abs(nx2 - nx1),
+      height: Math.abs(ny2 - ny1),
+      properties: { ...p, x1: nx1, y1: ny1, x2: nx2, y2: ny2 },
+    };
+  }
 
   const props = { ...el.properties };
   // Extend the end that is closer to the intersection
@@ -300,22 +365,197 @@ export function filletElements(el1: CADElement, el2: CADElement, radius: number)
 /**
  * Find intersection point of two elements (lines only for now).
  */
-function findIntersection(el1: CADElement, el2: CADElement): { x: number; y: number } | null {
+/** Punkt im 2D-Raum. */
+export interface Pt {
+  x: number;
+  y: number;
+}
+
+/**
+ * Alle Schnittpunkte einer Strecke p1→p2 mit einem Kreis (Zentrum c, Radius r).
+ * Liefert nur Punkte innerhalb des Streckensegments (t ∈ [0,1]); [] wenn keine.
+ */
+export function lineCircleIntersections(p1: Pt, p2: Pt, c: Pt, r: number): Pt[] {
+  const dx = p2.x - p1.x;
+  const dy = p2.y - p1.y;
+  const fx = p1.x - c.x;
+  const fy = p1.y - c.y;
+
+  const a = dx * dx + dy * dy;
+  const b = 2 * (fx * dx + fy * dy);
+  const cc = fx * fx + fy * fy - r * r;
+
+  let discriminant = b * b - 4 * a * cc;
+  if (discriminant < 0) return []; // keine reale Lösung
+
+  discriminant = Math.sqrt(discriminant);
+  const t1 = (-b - discriminant) / (2 * a);
+  const t2 = (-b + discriminant) / (2 * a);
+  // Tangente: beide Lösungen identisch → nur einen Punkt liefern
+  const ts = Math.abs(t1 - t2) < 1e-7 ? [t1] : [t1, t2];
+  const eps = 1e-9;
+  const results: Pt[] = [];
+  for (const t of ts) {
+    if (t >= -eps && t <= 1 + eps) {
+      results.push({ x: p1.x + t * dx, y: p1.y + t * dy });
+    }
+  }
+  return results;
+}
+
+/**
+ * Schnittpunkte zweier Kreise (Zentren c1/c2, Radien r1/r2).
+ * Liefert 0–2 Punkte; [] wenn getrennt oder identisch.
+ */
+export function circleCircleIntersections(c1: Pt, r1: number, c2: Pt, r2: number): Pt[] {
+  const dVec = { x: c2.x - c1.x, y: c2.y - c1.y };
+  const d = Math.hypot(dVec.x, dVec.y);
+  if (d === 0) return [];                       // identische Zentren
+  if (d > r1 + r2 || d < Math.abs(r1 - r2)) return []; // getrennt / ineinander
+
+  const a = (r1 * r1 - r2 * r2 + d * d) / (2 * d);
+  const hSq = r1 * r1 - a * a;
+  const h = Math.sqrt(Math.max(0, hSq));
+  const baseX = c1.x + (a * dVec.x) / d;
+  const baseY = c1.y + (a * dVec.y) / d;
+  if (h === 0) return [{ x: baseX, y: baseY }];  // tangentiale Berührung
+  return [
+    { x: baseX + (h * dVec.y) / d, y: baseY - (h * dVec.x) / d },
+    { x: baseX - (h * dVec.y) / d, y: baseY + (h * dVec.x) / d },
+  ];
+}
+
+/**
+ * Liest die Arc-Parameter eines CADElements nach der Konvention von
+ * RenderEngine.drawArc: Zentrum = el.x/el.y, radius/startAngle/endAngle aus
+ * properties; Winkel in GRAD, 0° = 3 Uhr, gegen Uhrzeigersinn.
+ */
+function readArc(el: CADElement): { c: Pt; r: number; startDeg: number; endDeg: number } | null {
+  const r = (el.properties?.radius as number | undefined) ?? (el as unknown as { width?: number }).width! / 2;
+  if (!Number.isFinite(r) || r <= 0) return null;
+  return {
+    c: { x: el.x, y: el.y },
+    r,
+    startDeg: ((el.properties?.startAngle as number | undefined) ?? 0),
+    endDeg: ((el.properties?.endAngle as number | undefined) ?? 360),
+  };
+}
+
+/** Prüft, ob ein Winkel (Grad) innerhalb eines Bogens liegt (CCW von start bis end). */
+function angleInArcRange(deg: number, startDeg: number, endDeg: number): boolean {
+  const norm = (v: number) => ((v % 360) + 360) % 360;
+  let a = norm(deg);
+  const s = norm(startDeg);
+  const e = norm(endDeg);
+  if (s <= e) return a >= s && a <= e;
+  return a >= s || a <= e; // Bogen über 0°
+}
+
+/**
+ * Wie lineCircleIntersections, aber OHNE Segmentbegrenzung (t ∈ ℝ):
+ * findet Schnitte auch auf der VERLÄNGERUNG der Strecke — Grundlage für
+ * echtes CAD-Extend (Task A4.10), bei dem das Ziel die Kante oft noch
+ * gar nicht berührt.
+ */
+export function lineCircleIntersectionsInfinite(p1: Pt, p2: Pt, c: Pt, r: number): Pt[] {
+  const dx = p2.x - p1.x;
+  const dy = p2.y - p1.y;
+  const fx = p1.x - c.x;
+  const fy = p1.y - c.y;
+  const a = dx * dx + dy * dy;
+  if (a < 1e-12) return [];
+  const b = 2 * (fx * dx + fy * dy);
+  const cc = fx * fx + fy * fy - r * r;
+  let disc = b * b - 4 * a * cc;
+  if (disc < 0) return [];
+  disc = Math.sqrt(disc);
+  const out: Pt[] = [];
+  for (const t of [(-b - disc) / (2 * a), (-b + disc) / (2 * a)]) {
+    out.push({ x: p1.x + t * dx, y: p1.y + t * dy });
+  }
+  return out;
+}
+
+/**
+ * Alle Schnittpunkte einer Strecke p1→p2 mit dem Bogen eines Elements
+ * (Konvention wie RenderEngine.drawArc). Nur Treffer innerhalb des Segments
+ * UND im Winkelbereich des Bogens werden zurückgegeben.
+ */
+export function lineArcIntersection(p1: Pt, p2: Pt, el: CADElement): Pt[] {
+  const arc = readArc(el);
+  if (!arc) return [];
+  return lineCircleIntersections(p1, p2, arc.c, arc.r)
+    .filter((pt) => angleInArcRange((Math.atan2(pt.y - arc.c.y, pt.x - arc.c.x) * 180) / Math.PI, arc.startDeg, arc.endDeg));
+}
+
+function lineLineIntersections(el1: CADElement, el2: CADElement): Pt[] {
   const p1 = el1.properties;
   const p2 = el2.properties;
 
-  if (p1.x1 === undefined || p1.y1 === undefined || p1.x2 === undefined || p1.y2 === undefined) return null;
-  if (p2.x1 === undefined || p2.y1 === undefined || p2.x2 === undefined || p2.y2 === undefined) return null;
+  if (p1.x1 === undefined || p1.y1 === undefined || p1.x2 === undefined || p1.y2 === undefined) return [];
+  if (p2.x1 === undefined || p2.y1 === undefined || p2.x2 === undefined || p2.y2 === undefined) return [];
 
-  // Line-line intersection
-  const denom = (p1.x1 - p1.x2) * (p2.y1 - p2.y2) - (p1.y1 - p1.y2) * (p2.x1 - p2.x2);
-  if (Math.abs(denom) < 1e-10) return null;
+  const denom = (p1.x1! - p1.x2!) * (p2.y1! - p2.y2!) - (p1.y1! - p1.y2!) * (p2.x1! - p2.x2!);
+  if (Math.abs(denom) < 1e-10) return [];
 
-  const t = ((p1.x1 - p2.x1) * (p2.y1 - p2.y2) - (p1.y1 - p2.y1) * (p2.x1 - p2.x2)) / denom;
-  const x = p1.x1 + t * (p1.x2 - p1.x1);
-  const y = p1.y1 + t * (p1.y2 - p1.y1);
+  const t = ((p1.x1! - p2.x1!) * (p2.y1! - p2.y2!) - (p1.y1! - p2.y1!) * (p2.x1! - p2.x2!)) / denom;
+  const x = p1.x1! + t * (p1.x2! - p1.x1!);
+  const y = p1.y1! + t * (p1.y2! - p1.y1!);
+  return [{ x, y }];
+}
 
-  return { x, y };
+/**
+ * Erster Schnittpunkt zweier CAD-Elemente (line/circle/arc), intern für
+ * trim/extend/fillet. Bei mehreren Treffern wird der zu el1 nächstgelegene
+ * gewählt. null wenn keine Kombination unterstützt oder kein Schnitt.
+ */
+function findIntersection(el1: CADElement, el2: CADElement): { x: number; y: number } | null {
+  const types = new Set([el1.type, el2.type]);
+  // Linie immer als erstes Argument normalisieren (reihenfolgeunabhängig)
+  const [lineEl, otherEl] = el1.type === 'line' ? [el1, el2] : [el2, el1];
+  let candidates: Pt[] = [];
+  let refFromFirst = true; // Referenzpunkt von el1 nehmen?
+
+  if (types.has('line') && types.size === 1) {
+    candidates = lineLineIntersections(el1, el2);
+    refFromFirst = false; // beide sind Linien; Referenz unten via el1-Startpunkt
+  } else if (types.has('line') && types.has('circle')) {
+    candidates = lineCircleIntersections(
+      { x: lineEl.properties.x1!, y: lineEl.properties.y1! },
+      { x: lineEl.properties.x2!, y: lineEl.properties.y2! },
+      { x: otherEl.x, y: otherEl.y },
+      (otherEl.properties.radius as number | undefined) ?? otherEl.width / 2,
+    );
+  } else if (types.has('line') && types.has('arc')) {
+    candidates = lineArcIntersection(
+      { x: lineEl.properties.x1!, y: lineEl.properties.y1! },
+      { x: lineEl.properties.x2!, y: lineEl.properties.y2! },
+      otherEl,
+    );
+  } else if (types.has('circle') && types.size === 1) {
+    candidates = circleCircleIntersections(
+      { x: el1.x, y: el1.y },
+      (el1.properties.radius as number | undefined) ?? el1.width / 2,
+      { x: el2.x, y: el2.y },
+      (el2.properties.radius as number | undefined) ?? el2.width / 2,
+    );
+    refFromFirst = false;
+  }
+
+  if (candidates.length === 0) return null;
+  // Nächstliegenden Treffer zu el1 wählen (Startpunkt bei Linie, sonst Zentrum)
+  const isFirstLine = el1.type === 'line';
+  const refX = refFromFirst || isFirstLine
+    ? (isFirstLine ? el1.properties.x1 : el1.x)
+    : el1.x;
+  const refY = refFromFirst || isFirstLine
+    ? (isFirstLine ? el1.properties.y1 : el1.y)
+    : el1.y;
+  let best = candidates[0];
+  for (const c of candidates) {
+    if (Math.hypot(c.x - refX!, c.y - refY!) < Math.hypot(best.x - refX!, best.y - refY!)) best = c;
+  }
+  return best;
 }
 
 /**

frontend/src/types/ui.types.ts

@@ -94,6 +94,8 @@ export interface RibbonBarProps {
   onCanvasBgColorChange?: (color: string) => void;
   onGridColorChange?: (color: string) => void;
   onToggleRuler?: () => void;
+  /** Task A4.13: meldet, ob ein V2-Werkzeug-ID aktuell das aktive Tool ist (Highlight). */
+  onIsV2ToolActive?: (toolId: string) => boolean;
 }
 
 export interface LeftSidebarProps {

frontend/src/utils/logger.ts

@@ -0,0 +1,69 @@
+/**
+ * Minimaler Level-basierter Logger.
+ * Ziel: direktes `console.log` im Produktivcode ersetzen (ROADMAP Teil-4-Regel),
+ * damit sich Logs zentral filtern/abschalten lassen.
+ *
+ * Nutzung:
+ *   import { logger } from '../utils/logger';
+ *   logger.info('Element erstellt', el.id);
+ *
+ * Level über localStorage['webcad.logLevel'] ('silent'|'error'|'warn'|'info'|'debug',
+ * Default: 'info'). `logger.debug` bleibt auf Default still.
+ */
+
+export type LogLevel = 'silent' | 'error' | 'warn' | 'info' | 'debug';
+
+const LEVEL_ORDER: Record<LogLevel, number> = {
+  silent: 100,
+  error: 40,
+  warn: 30,
+  info: 20,
+  debug: 10,
+};
+
+function readConfiguredLevel(): LogLevel {
+  try {
+    // Browser und jsdom haben localStorage; in reinen Node-Tests schlägt der Zugriff fehl
+    const raw = globalThis.localStorage?.getItem('webcad.logLevel');
+    if (raw && raw in LEVEL_ORDER) return raw as LogLevel;
+  } catch {
+    /* Umgebung ohne localStorage → Default */
+  }
+  return 'info';
+}
+
+let currentLevel: LogLevel = readConfiguredLevel();
+
+/** Setzt das Level programmatisch (überschreibt localStorage bis zum Reload). */
+export function setLogLevel(level: LogLevel): void {
+  currentLevel = level;
+}
+
+/** Aktuell aktives Log-Level. */
+export function getLogLevel(): LogLevel {
+  return currentLevel;
+}
+
+class Logger {
+  /** Fehlerhafte Zustände — melden außer bei silent. */
+  error(...args: unknown[]): void {
+    if (LEVEL_ORDER[currentLevel] <= LEVEL_ORDER.error) console.error('[web-cad]', ...args);
+  }
+
+  /** Warnungen. */
+  warn(...args: unknown[]): void {
+    if (LEVEL_ORDER[currentLevel] <= LEVEL_ORDER.warn) console.warn('[web-cad]', ...args);
+  }
+
+  /** Normale Informationsmeldungen (Default-Level aktiv). */
+  info(...args: unknown[]): void {
+    if (LEVEL_ORDER[currentLevel] <= LEVEL_ORDER.info) console.log('[web-cad]', ...args);
+  }
+
+  /** Debug-Ausgaben — nur wenn Level debug konfiguriert ist. */
+  debug(...args: unknown[]): void {
+    if (LEVEL_ORDER[currentLevel] <= LEVEL_ORDER.debug) console.log('[web-cad][debug]', ...args);
+  }
+}
+
+export const logger = new Logger();

frontend/tests/bugs.regress.test.ts

@@ -0,0 +1,173 @@
+/**
+ * Regressions-Tests für bekannte Bugs BUG-1, BUG-1b, BUG-2.
+ * Diese Tests sind VOR dem jeweiligen Fix ROT (dokumentiertes Fehlverhalten)
+ * und müssen danach GRÜN sein.
+ */
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { SeatingService } from '../src/services/seatingService';
+import { trimElement, offsetElement } from '../src/tools/modification/geometry';
+import type { CADElement } from '../src/types/cad.types';
+import { RenderEngine } from '../src/canvas/RenderEngine';
+import { ZoomPanController } from '../src/canvas/ZoomPanController';
+import { SpatialIndex } from '../src/canvas/SpatialIndex';
+import { LayerManager } from '../src/canvas/LayerManager';
+
+// ── Helfer (Muster aus tests/geometry.test.ts) ─────────────
+function makeLine(id: string, x1: number, y1: number, x2: number, y2: number): CADElement {
+  return {
+    id,
+    type: 'line',
+    layerId: 'layer-1',
+    x: (x1 + x2) / 2,
+    y: (y1 + y2) / 2,
+    width: Math.abs(x2 - x1),
+    height: Math.abs(y2 - y1),
+    properties: { x1, y1, x2, y2 },
+  } as unknown as CADElement;
+}
+
+function makeCircle(id: string, cx: number, cy: number, r: number): CADElement {
+  return {
+    id,
+    type: 'circle',
+    layerId: 'layer-1',
+    x: cx,
+    y: cy,
+    width: r * 2,
+    height: r * 2,
+    properties: { radius: r },
+  } as unknown as CADElement;
+}
+
+// ── BUG-1: rowId-Kollision bei schnellem Erzeugen ───────────
+describe('BUG-1: seating row ids', () => {
+  it('zwei direkt hintereinander erzeugte Reihen haben unterschiedliche rowIds', () => {
+    const svc = new SeatingService();
+    const a = svc.createSeatingRow(0, 0, 'layer-1');
+    const b = svc.createSeatingRow(0, 100, 'layer-1');
+    const ids = new Set([a[0].properties.rowId, b[0].properties.rowId]);
+    expect(ids.size).toBe(2);
+  });
+});
+
+// ── BUG-1b: Block-Reihen ohne eigene rowId ──────────────────
+describe('BUG-1b: seating block row ids', () => {
+  it('jede Reihe eines Blocks hat eine eigene, definierte rowId', () => {
+    const svc = new SeatingService();
+    const els = svc.createSeatingBlock(0, 0, 'layer-1', { rows: 3, cols: 2 });
+    expect(els.length).toBe(6);
+    const rowIds = new Set(els.map((e) => e.properties.rowId));
+    expect(rowIds.size).toBe(3);
+    for (const rid of rowIds) expect(rid).toBeDefined();
+  });
+});
+
+// ── BUG-2: Trim an Kreis scheitert (findIntersection nur Gerade×Gerade) ──
+describe('BUG-2: trim line at circle', () => {
+  it('trimElement(Linie, Kreis) liefert ein Ergebnis statt null', () => {
+    // Linie von (0,0) nach (200,0) schneidet Kreis (Zentrum 100,0, Radius 40)
+    // an x=60 und x=140 → Schnitt existiert eindeutig.
+    const line = makeLine('l1', 0, 0, 200, 0);
+    const circle = makeCircle('c1', 100, 0, 40);
+    const result = trimElement(line, circle);
+    expect(result).not.toBeNull();
+  });
+});
+
+// ── BUG-3: Offset ignorierte die Klickseite ─────────────────
+describe('BUG-3: offset respects click side', () => {
+  it('side=-1 versetzt Linie entgegen der Normalenrichtung', () => {
+    // Linie (100,100)→(300,100): Laufrichtung +x.
+    // Normale (-dy,dx)=(0,1) zeigt in Canvas-Koordinaten nach UNTEN (+y).
+    const line = makeLine('l1', 100, 100, 300, 100);
+    const result = offsetElement(line, 20, -1);
+    expect(result.properties.y1).toBeCloseTo(80); // nach OBEN versetzt
+    expect(result.properties.y2).toBeCloseTo(80);
+  });
+
+  it('side=+1 versetzt Linie in Normalenrichtung (Default wie vorher)', () => {
+    const line = makeLine('l1', 100, 100, 300, 100);
+    const result = offsetElement(line, 20, 1);
+    expect(result.properties.y1).toBeCloseTo(120); // nach UNTEN versetzt
+    expect(result.properties.y2).toBeCloseTo(120);
+  });
+
+  it('ohne side bleibt Verhalten identisch zur alten API (Rueckwaertskompatibilitaet)', () => {
+    const line = makeLine('l1', 100, 100, 300, 100);
+    const result = offsetElement(line, 20);
+    expect(result.properties.y1).toBeCloseTo(120);
+  });
+
+  it('Kreis: side=-1 verkleinert Radius, side=+1 vergroessert', () => {
+    const circle = makeCircle('c1', 0, 0, 50);
+    expect(offsetElement(circle, 10, -1).properties.radius).toBeCloseTo(40);
+    expect(offsetElement(circle, 10, 1).properties.radius).toBeCloseTo(60);
+  });
+});
+
+// ── BUG-4: Hintergrundbild wurde pro Frame neu geladen ──────
+describe('BUG-4: background image cached', () => {
+  let imageCount: number;
+  let OriginalImage: typeof Image;
+
+  beforeEach(() => {
+    imageCount = 0;
+    OriginalImage = global.Image;
+    // Bild-Stub: zaehlt Konstruktur-Aufrufe; simuliert Browser-Cache-Bild
+    // (complete=true sofort verfuegbar, onload als Mikrotask wie async decode)
+    class FakeImage {
+      complete = true;
+      naturalWidth = 800;
+      width = 800;
+      height = 600;
+      onload: (() => void) | null = null;
+      private internalSrc = '';
+      get src(): string {
+        return this.internalSrc;
+      }
+      set src(value: string) {
+        this.internalSrc = value;
+        queueMicrotask(() => this.onload?.());
+      }
+      constructor() {
+        imageCount += 1;
+      }
+    }
+    (global as { Image: unknown }).Image = FakeImage as unknown as typeof Image;
+  });
+
+  afterEach(() => {
+    (global as { Image: unknown }).Image = OriginalImage;
+  });
+
+  function createEngine(): RenderEngine {
+    const canvas = document.createElement('canvas');
+    canvas.width = 800;
+    canvas.height = 600;
+    const zoomPan = new ZoomPanController(canvas);
+    const spatialIndex = new SpatialIndex();
+    const layerManager = new LayerManager();
+    return new RenderEngine(canvas, zoomPan, spatialIndex, layerManager);
+  }
+
+  it('lädt das Bild pro Quellwechsel nur EINMAL, weitere Frames nutzen den Cache', async () => {
+    const engine = createEngine();
+    const DATA_URL = 'data:image/png;base64,iVBORw0KGgo=';
+    engine.setOptions({ backgroundSrc: DATA_URL, backgroundOpacity: 0.5 });
+
+    // Frame 1: legt genau ein Image an und cachet es (complete=true)
+    engine.render();
+    expect(imageCount).toBe(1);
+
+    // Weitere Frames mit identischer src: dürfen KEIN neues Image erzeugen
+    engine.render();
+    engine.render();
+    engine.render();
+    expect(imageCount).toBe(1);
+
+    // Ausstehende Mikrotasks (simuliertes onload) abwarten, dann erneut prüfen:
+    await Promise.resolve();
+    engine.render();
+    expect(imageCount).toBe(1); // vorher (Bug): jedes render() erzeugte ein neues Image
+  });
+});

frontend/tests/cadDocument.test.ts

@@ -0,0 +1,121 @@
+/**
+ * CADDocument Tests (Task A2b).
+ * Kern-Verhalten: CRUD, Shallow-Merge, Transaktion = 1 Undo-Schritt,
+ * undo/redo-Stacks, deleteElements selektiv.
+ */
+import { describe, it, expect } from 'vitest';
+import { CADDocument } from '../src/kernel/document/CADDocument';
+import { createInMemoryDoc } from './helpers/inMemoryDoc';
+import type { CADElement } from '../src/types/cad.types';
+
+function makeEl(id: string, props: Record<string, unknown> = {}): CADElement {
+  return {
+    id,
+    type: 'rect',
+    layerId: 'layer-1',
+    x: 10,
+    y: 20,
+    width: 30,
+    height: 40,
+    properties: props,
+  } as unknown as CADElement;
+}
+
+function makeDoc(): { doc: CADDocument } {
+  const { ydoc } = createInMemoryDoc();
+  return { doc: new CADDocument(ydoc) };
+}
+
+describe('CADDocument', () => {
+  it('a) addElement → getAllElements enthaelt es', () => {
+    const { doc } = makeDoc();
+    doc.addElement(makeEl('e1'));
+    const all = doc.getAllElements();
+    expect(all.length).toBe(1);
+    expect(all[0].id).toBe('e1');
+    expect(doc.getElement('e1')).toBeDefined();
+    expect(doc.getElement('missing')).toBeUndefined();
+  });
+
+  it('b) transact um zwei addElements = EIN Undo-Schritt entfernt BEIDE', () => {
+    const { doc } = makeDoc();
+    doc.transact(() => {
+      doc.addElement(makeEl('a'));
+      doc.addElement(makeEl('b'));
+    });
+    expect(doc.getAllElements().length).toBe(2);
+    expect(doc.canUndo()).toBe(true);
+
+    expect(doc.undo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(0); // beide weg mit einem undo!
+    expect(doc.canUndo()).toBe(false);
+  });
+
+  it('c) redo stellt beide Elemente wieder her', () => {
+    const { doc } = makeDoc();
+    doc.transact(() => {
+      doc.addElement(makeEl('a'));
+      doc.addElement(makeEl('b'));
+    });
+    doc.undo();
+    expect(doc.getAllElements().length).toBe(0);
+
+    expect(doc.canRedo()).toBe(true);
+    expect(doc.redo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(2);
+    expect(doc.getElement('a')).toBeDefined();
+    expect(doc.getElement('b')).toBeDefined();
+  });
+
+  it('d) updateElement merged properties SHALLOW (bestehende Keys bleiben)', () => {
+    const { doc } = makeDoc();
+    doc.addElement(makeEl('m', { fill: 'red', rotation: 45, stroke: 'black' }));
+
+    doc.updateElement('m', { properties: { fill: 'blue' } });
+    const el = doc.getElement('m')!;
+    expect(el.properties.fill).toBe('blue');       // ueberschrieben
+    expect(el.properties.rotation).toBe(45);        // erhalten
+    expect(el.properties.stroke).toBe('black');     // erhalten
+  });
+
+  it('d2) updateElement kann Top-Level-Felder setzen und wirft bei fehlender ID', () => {
+    const { doc } = makeDoc();
+    doc.addElement(makeEl('m'));
+    doc.updateElement('m', { x: 999 });
+    expect(doc.getElement('m')!.x).toBe(999);
+    expect(() => doc.updateElement('ghost', { x: 1 })).toThrow(/nicht gefunden/);
+  });
+
+  it('e) deleteElements entfernt nur die genannten IDs', () => {
+    const { doc } = makeDoc();
+    doc.transact(() => {
+      doc.addElement(makeEl('keep1'));
+      doc.addElement(makeEl('del1'));
+      doc.addElement(makeEl('del2'));
+      doc.addElement(makeEl('keep2'));
+    });
+
+    doc.deleteElements(['del1', 'del2', 'unbekannt']); // unbekannte still ignorieren
+    const ids = doc.getAllElements().map((e) => e.id).sort();
+    expect(ids).toEqual(['keep1', 'keep2']);
+  });
+
+  it('undo nach deleteElements stellt geloeschte Elemente wieder her', () => {
+    const { doc } = makeDoc();
+    doc.addElement(makeEl('x1'));
+    doc.addElement(makeEl('x2'));
+
+    doc.deleteElements(['x1']);
+    expect(doc.getAllElements().length).toBe(1);
+
+    doc.undo(); // Delete rueckgaengig
+    expect(doc.getAllElements().length).toBe(2);
+    expect(doc.getElement('x1')).toBeDefined();
+  });
+
+  it('undo/redo liefern false auf leeren Stacks', () => {
+    const { doc } = makeDoc();
+    expect(doc.undo()).toBe(false);
+    expect(doc.redo()).toBe(false);
+  });
+});

frontend/tests/dispatcher.test.ts

@@ -0,0 +1,138 @@
+/**
+ * InteractionDispatcher Tests (Task A2).
+ * Prüft Event-Routing gegen ein Fake-Werkzeug ohne echte Registry:
+ * Reihenfolge down→move→up, ESC/Rechtsklick cancel, move nur bei aktiver Session,
+ * unbekanntes Tool → kein Routing.
+ */
+import { describe, it, expect, vi, afterEach } from 'vitest';
+import { InteractionDispatcher } from '../src/interaction/dispatcher';
+import type { ToolExtensionV2 } from '../src/plugins/types';
+import type { ZoomPanController } from '../src/canvas/ZoomPanController';
+
+function makeFakeZoomPan(): ZoomPanController {
+  return {
+    screenToWorld: (sx: number, sy: number) => ({ x: sx * 2, y: sy * 3 }),
+  } as unknown as ZoomPanController;
+}
+
+function makeRecordingTool(id = 'fake'): { tool: ToolExtensionV2; log: string[] } {
+  const log: string[] = [];
+  const tool: ToolExtensionV2 = {
+    manifest: { id, label: 'Fake', icon: 'f', ribbonTab: 'tools' },
+    optionsSchema: [],
+    handlers: {
+      down: () => log.push('down'),
+      move: () => log.push('move'),
+      up: () => log.push('up'),
+      key: () => false,
+      cancel: () => log.push('cancel'),
+    },
+  };
+  return { tool, log };
+}
+
+function fire(canvas: HTMLCanvasElement, type: string, opts: Partial<PointerEventInit> = {}): PointerEvent {
+  const e = new PointerEvent(type, {
+    bubbles: true,
+    clientX: 100,
+    clientY: 50,
+    button: 0,
+    ...opts,
+  });
+  if (type === 'pointerdown') canvas.dispatchEvent(e);
+  else window.dispatchEvent(e);
+  return e;
+}
+
+function fireKey(key: string): KeyboardEvent {
+  const e = new KeyboardEvent('keydown', { key, bubbles: true });
+  window.dispatchEvent(e);
+  return e;
+}
+
+describe('InteractionDispatcher', () => {
+  let canvas: HTMLCanvasElement;
+
+  afterEach(() => {
+    canvas?.remove();
+  });
+
+  function setup(tool?: ToolExtensionV2) {
+    canvas = document.createElement('canvas');
+    document.body.appendChild(canvas);
+    const dispatcher = new InteractionDispatcher(canvas, {
+      zoomPan: makeFakeZoomPan(),
+      toolLookup: tool ? () => tool : undefined,
+    });
+    return { dispatcher };
+  }
+
+  it('routet down→move→up in Reihenfolge an das aktive Tool', () => {
+    const { tool, log } = makeRecordingTool();
+    const { dispatcher } = setup(tool);
+    dispatcher.setActive('fake');
+
+    fire(canvas, 'pointerdown');
+    fire(window, 'pointermove');
+    fire(window, 'pointerup');
+
+    expect(log).toEqual(['down', 'move', 'up']);
+    expect(dispatcher.getActive()?.manifest.id).toBe('fake');
+  });
+
+  it('ignoriert move/up ohne vorheriges down (Session-Guard)', () => {
+    const { tool, log } = makeRecordingTool();
+    const { dispatcher } = setup(tool);
+    dispatcher.setActive('fake');
+
+    fire(window, 'pointermove'); // keine Session aktiv
+    fire(window, 'pointerup');
+    expect(log).toEqual([]);
+  });
+
+  it('ESC ruft cancel und beendet die Session', () => {
+    const { tool, log } = makeRecordingTool();
+    const { dispatcher } = setup(tool);
+    dispatcher.setActive('fake');
+
+    fire(canvas, 'pointerdown');
+    fireKey('Escape');
+    expect(log).toEqual(['down', 'cancel']);
+
+    fire(window, 'pointermove'); // Session beendet → kein move mehr
+    expect(log).toEqual(['down', 'cancel']);
+  });
+
+  it('Rechtsklick bricht ab, ohne down durchzureichen', () => {
+    const { tool, log } = makeRecordingTool();
+    const { dispatcher } = setup(tool);
+    dispatcher.setActive('fake');
+
+    fire(canvas, 'pointerdown', { button: 2 });
+    expect(log).toEqual(['cancel']);
+  });
+
+  it('setActive(null) deaktiviert Routing komplett', () => {
+    const { tool, log } = makeRecordingTool();
+    const { dispatcher } = setup(tool);
+    dispatcher.setActive('fake');
+    dispatcher.setActive(null);
+    fire(canvas, 'pointerdown');
+    fire(window, 'pointermove');
+    expect(log).toEqual([]);
+  });
+
+  it('liefert Weltkoordinaten aus zoomPan.screenToWorld', () => {
+    let received: { x: number; y: number } | null = null;
+    const tool: ToolExtensionV2 = {
+      manifest: { id: 'geo', label: 'G', icon: 'g', ribbonTab: 't' },
+      optionsSchema: [],
+      handlers: { down: (e) => (received = { ...e.world }) },
+    };
+    const { dispatcher } = setup(tool);
+    dispatcher.setActive('geo');
+    fire(canvas, 'pointerdown', { clientX: 100, clientY: 50 });
+    // fake screenToWorld: x*2, y*3 → (200, 150)
+    expect(received).toEqual({ x: 200, y: 150 });
+  });
+});

frontend/tests/documentService.test.ts

@@ -0,0 +1,56 @@
+/**
+ * documentService Tests (Task A4.11).
+ * Prüft Registrierung/Löschung des aktiven Dokuments und die
+ * Undo/Redo-Delegation an CADDocument.
+ */
+import { describe, it, expect, afterEach } from 'vitest';
+import { setActiveDocument, getActiveDocument, undoActive, redoActive } from '../src/kernel/document/documentService';
+import { CADDocument } from '../src/kernel/document/CADDocument';
+import { createInMemoryDoc } from './helpers/inMemoryDoc';
+import type { CADElement } from '../src/types/cad.types';
+
+function makeEl(id: string): CADElement {
+  return {
+    id,
+    type: 'rect',
+    layerId: 'l',
+    x: 0,
+    y: 0,
+    width: 1,
+    height: 1,
+    properties: {},
+  } as unknown as CADElement;
+}
+
+afterEach(() => {
+  setActiveDocument(null);
+});
+
+describe('documentService', () => {
+  it('registriert und entregistriert das aktive Dokument', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    setActiveDocument(doc);
+    expect(getActiveDocument()).toBe(doc);
+    setActiveDocument(null);
+    expect(getActiveDocument()).toBeNull();
+  });
+
+  it('undoActive delegiert an das registrierte Dokument', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    doc.addElement(makeEl('x1'));
+    setActiveDocument(doc);
+
+    expect(undoActive()).toBe(true);      // Element wird entfernt
+    expect(doc.getAllElements().length).toBe(0);
+    expect(redoActive()).toBe(true);       // wiederhergestellt
+    expect(doc.getAllElements().length).toBe(1);
+  });
+
+  it('undoActive liefert false ohne aktives Dokument', () => {
+    setActiveDocument(null);
+    expect(undoActive()).toBe(false);
+    expect(redoActive()).toBe(false);
+  });
+});

frontend/tests/elementDrawers.test.ts

@@ -0,0 +1,174 @@
+/**
+ * elementToPrimitives Tests (Task C2).
+ * Deckt alle unterstützten Typen + Legacy-Konventionen + Grenzfälle ab.
+ */
+import { describe, it, expect } from 'vitest';
+import { elementToPrimitives } from '../src/render/pixi/elementDrawers';
+import type { CADElement } from '../src/types/cad.types';
+
+function el(id: string, type: string, props: Record<string, unknown> = {}, geom: Partial<CADElement> = {}): CADElement {
+  return {
+    id,
+    type,
+    layerId: 'l',
+    x: 0,
+    y: 0,
+    width: 10,
+    height: 10,
+    properties: props,
+    ...geom,
+  } as unknown as CADElement;
+}
+
+describe('elementToPrimitives', () => {
+  it('line: aus properties.x1..y2 mit stroke/sw', () => {
+    const prims = elementToPrimitives(el('l', 'line', {
+      x1: 0, y1: 0, x2: 100, y2: 50, stroke: '#f00', strokeWidth: 3,
+    }));
+    expect(prims.length).toBe(1);
+    expect(prims[0]).toEqual({
+      kind: 'line', from: { x: 0, y: 0 }, to: { x: 100, y: 50 },
+      stroke: '#f00', strokeWidth: 3,
+    });
+  });
+
+  it('line ohne Koordinaten ergibt leere Liste', () => {
+    expect(elementToPrimitives(el('l', 'line', {}))).toEqual([]);
+  });
+
+  it('rect: x/y ist Zentrum der BBox (Legacy-Konvention)', () => {
+    const prims = elementToPrimitives(el('r', 'rect', { fill: '#123456' }, {
+      x: 100, y: 50, width: 80, height: 40,
+    }));
+    expect(prims.length).toBe(1);
+    const p = prims[0];
+    if (p.kind !== 'rect') throw new Error('erwartete rect');
+    expect(p.x).toBe(60);   // 100 − 40
+    expect(p.y).toBe(30);   // 50 − 20
+    expect(p.w).toBe(80);
+    expect(p.h).toBe(40);
+    expect(p.fill).toBe('#123456');
+  });
+
+  it('rect fill none wird zu null', () => {
+    const prims = elementToPrimitives(el('r', 'rect', { fill: 'none' }));
+    const p = prims[0];
+    if (p.kind !== 'rect') throw new Error('erwartete rect');
+    expect(p.fill).toBeNull();
+  });
+
+  it('circle: radius mit Fallback width/2', () => {
+    const withExplicit = elementToPrimitives(el('c', 'circle', { radius: 25, fill: '#abcdef' }, { x: 5, y: 5 }));
+    const p = withExplicit[0];
+    if (p.kind !== 'circle') throw new Error('erwartete circle');
+    expect(p.radius).toBe(25);
+    expect(p.center).toEqual({ x: 5, y: 5 });
+    expect(p.fill).toBe('#abcdef');
+
+    const byWidth = elementToPrimitives(el('c', 'circle', {}, { width: 120 }));
+    const pb = byWidth[0];
+    if (pb.kind !== 'circle') throw new Error('erwartete circle');
+    expect(pb.radius).toBe(60); // fallback
+  });
+
+  it('arc: Winkel in Grad wie Legacy', () => {
+    const prims = elementToPrimitives(el('a', 'arc', {
+      radius: 40, startAngle: 0, endAngle: 90,
+    }, { x: 0, y: 0 }));
+    const p = prims[0];
+    if (p.kind !== 'arc') throw new Error('erwartete arc');
+    expect(p.startDeg).toBe(0);
+    expect(p.endDeg).toBe(90);
+    expect(p.radius).toBe(40);
+  });
+
+  it('polyline/polygon: points-Array, close je nach Typ', () => {
+    const pts = [{ x: 0, y: 0 }, { x: 10, y: 0 }, { x: 10, y: 10 }];
+    const open = elementToPrimitives(el('pl', 'polyline', { points: pts }));
+    const closed = elementToPrimitives(el('pg', 'polygon', { points: pts }));
+    expect(open.length).toBe(1);
+    expect(closed.length).toBe(1);
+    if (open[0].kind !== 'polyline' || closed[0].kind !== 'polyline') {
+      throw new Error('erwartete polyline');
+    }
+    expect(open[0].close).toBe(false);
+    expect(closed[0].close).toBe(true);
+  });
+
+  it('text: leer nicht gerendert; gefuellt mit fontSize/color', () => {
+    expect(elementToPrimitives(el('t', 'text', { text: '' }))).toEqual([]);
+
+    const filled = elementToPrimitives(el('t', 'text', {
+      text: 'Bühne A', fontSize: 18, color: '#ffffff',
+    }, { x: 50, y: 75 }));
+    expect(filled.length).toBe(1);
+    const p = filled[0];
+    if (p.kind !== 'text') throw new Error('erwartete text');
+    expect(p.text).toBe('Bühne A');
+    expect(p.fontSize).toBe(18);
+    expect(p.color).toBe('#ffffff');
+  });
+
+  it('unbekannter Typ ergibt leere Liste (renderer-sicher)', () => {
+    expect(elementToPrimitives(el('x', 'definitely-unknown'))).toEqual([]);
+  });
+
+  it('dimension: Linie + Label aus value/text', () => {
+    const prims = elementToPrimitives(el('d', 'dimension', {
+      x1: 0, y1: 0, x2: 100, y2: 0, value: '250 cm',
+    }, { x: 50, y: 0 }));
+    expect(prims.length).toBe(2);
+    expect(prims[0].kind).toBe('line');
+    const txt = prims[1];
+    if (txt.kind !== 'text') throw new Error('erwartete text');
+    expect(txt.text).toBe('250 cm');
+  });
+
+  it('leader: Linie + Label am Ende', () => {
+    const prims = elementToPrimitives(el('ld', 'leader', {
+      x1: 10, y1: 10, x2: 80, y2: 60, text: 'A1', fontSize: 14,
+    }));
+    expect(prims.length).toBe(2);
+    expect(prims[0].kind).toBe('line');
+    const txt = prims[1];
+    if (txt.kind !== 'text') throw new Error('erwartete text');
+    expect(txt.text).toBe('A1');
+    expect(txt.fontSize).toBe(14);
+  });
+
+  it('revcloud: geschlossener Punktzug', () => {
+    const prims = elementToPrimitives(el('rc', 'revcloud', {
+      points: [{ x: 0, y: 0 }, { x: 50, y: 0 }, { x: 50, y: 30 }],
+    }));
+    expect(prims.length).toBe(1);
+    const p = prims[0];
+    if (p.kind !== 'polyline') throw new Error('erwartete polyline');
+    expect(p.close).toBe(true);
+  });
+
+  it('chair: gefuelltes Rechteck mit Fallback-Farbe', () => {
+    const prims = elementToPrimitives(el('ch', 'chair', {}, { x: 50, y: 50, width: 20, height: 20 }));
+    const p = prims[0];
+    if (p.kind !== 'rect') throw new Error('erwartete rect');
+    expect(p.fill).toBe('#4a90d9');
+    expect(p.x).toBe(40);
+    expect(p.y).toBe(40);
+  });
+
+  it('table: Kreis mit Fallback-Farbe und Radius aus width', () => {
+    const prims = elementToPrimitives(el('tb', 'table', {}, { x: 0, y: 0, width: 60, height: 60 }));
+    const p = prims[0];
+    if (p.kind !== 'circle') throw new Error('erwartete circle');
+    expect(p.radius).toBe(30);
+    expect(p.fill).toBe('#8b7355');
+  });
+
+  it('stage: dunkles Rechteck', () => {
+    const prims = elementToPrimitives(el('st', 'stage', {}, { x: 0, y: 0, width: 200, height: 100 }));
+    const p = prims[0];
+    if (p.kind !== 'rect') throw new Error('erwartete rect');
+    expect(p.fill).toBe('#3a3a4a');
+    expect(p.w).toBe(200);
+    expect(p.h).toBe(100);
+  });
+});

frontend/tests/geometry.test.ts

@@ -10,6 +10,9 @@ import {
   offsetElement,
   getElementBBox,
   distance,
+  lineCircleIntersections,
+  circleCircleIntersections,
+  lineArcIntersection,
   angleBetween,
 } from '../src/tools/modification/geometry';
 import type { CADElement } from '../src/types/cad.types';
@@ -293,3 +296,90 @@ describe('geometry – angleBetween', () => {
     expect(angleBetween({ x: 0, y: 0 }, { x: 0, y: 100 })).toBe(90);
   });
 });
+
+describe('geometry – lineCircleIntersections', () => {
+  const p1 = { x: 0, y: 0 };
+  const p2 = { x: 200, y: 0 };
+  const c = { x: 100, y: 0 };
+
+  it('findet zwei Schnittpunkte bei Sekante', () => {
+    const pts = lineCircleIntersections(p1, p2, c, 40);
+    expect(pts.length).toBe(2);
+    const xs = pts.map((p) => Math.round(p.x)).sort((a, b) => a - b);
+    expect(xs).toEqual([60, 140]);
+  });
+
+  it('findet genau einen Punkt bei Tangente', () => {
+    // Strecke entlang y=40 tangiert Kreis (100,0,r=40)
+    const pts = lineCircleIntersections({ x: 50, y: 40 }, { x: 150, y: 40 }, { x: 100, y: 0 }, 40);
+    expect(pts.length).toBe(1);
+    expect(pts[0].x).toBeCloseTo(100);
+    expect(pts[0].y).toBeCloseTo(40);
+  });
+
+  it('liefert leeres Array ohne Schnitt (Diskriminante < 0)', () => {
+    expect(lineCircleIntersections(p1, p2, { x: 100, y: 500 }, 10)).toEqual([]);
+  });
+
+  it('respektiert Segmentgrenzen t∈[0,1] (Verlaengerung schneidet nicht)', () => {
+    // Kreis liegt hinter dem Endpunkt der Strecke
+    expect(lineCircleIntersections({ x: 0, y: 0 }, { x: 50, y: 0 }, { x: 100, y: 0 }, 30)).toEqual([]);
+  });
+});
+
+describe('geometry – circleCircleIntersections', () => {
+  it('findet zwei Punkte bei Ueberlappung', () => {
+    const pts = circleCircleIntersections({ x: 0, y: 0 }, 50, { x: 80, y: 0 }, 50);
+    expect(pts.length).toBe(2);
+    for (const pt of pts) {
+      expect(pt.x).toBeCloseTo(40);           // Symmetrieachse
+      expect(Math.abs(pt.y)).toBeCloseTo(30); // Höhe via Satz des Pythagoras
+    }
+  });
+
+  it('liefert einen Punkt bei Tangenz', () => {
+    const pts = circleCircleIntersections({ x: 0, y: 0 }, 50, { x: 100, y: 0 }, 50);
+    expect(pts.length).toBe(1);
+    expect(pts[0]).toEqual({ x: 50, y: 0 });
+  });
+
+  it('liefert leer bei getrennten Kreisen und identischen Zentren', () => {
+    expect(circleCircleIntersections({ x: 0, y: 0 }, 20, { x: 500, y: 0 }, 20)).toEqual([]);
+    expect(circleCircleIntersections({ x: 0, y: 0 }, 20, { x: 0, y: 0 }, 20)).toEqual([]);
+  });
+});
+
+describe('geometry – lineArcIntersection', () => {
+  function makeArc(id: string, cx: number, cy: number, r: number, startDeg: number, endDeg: number): CADElement {
+    return {
+      id,
+      type: 'arc',
+      layerId: 'layer-1',
+      x: cx,
+      y: cy,
+      width: r * 2,
+      height: r * 2,
+      properties: { radius: r, startAngle: startDeg, endAngle: endDeg },
+    } as unknown as CADElement;
+  }
+
+  it('schneidet Strecke mit Halbkreis (0°..180°)', () => {
+    const arc = makeArc('a1', 100, 0, 40, 0, 180); // obere Hälfte (CCW von 3Uhr)
+    const pts = lineArcIntersection({ x: 60, y: 0 }, { x: 140, y: 40 }, arc);
+    // Linie von (60,0) nach (140,40): schneidet Bogen einmal oben
+    expect(pts.length).toBeGreaterThanOrEqual(1);
+  });
+
+  it('filtert Treffer außerhalb des Winkelbereichs heraus', () => {
+    const arc = makeArc('a2', 100, 0, 40, 180, 360); // untere Hälfte
+    // Strecke verläuft komplett oberhalb der Mittellinie → Schnitte lägen nur
+    // im oberen Halbkreis (Winkel < 180°), der nicht Teil des Bogens ist.
+    const pts = lineArcIntersection({ x: 60, y: 20 }, { x: 140, y: 40 }, arc);
+    expect(pts).toEqual([]);
+  });
+
+  it('liefert leer bei fehlendem Radius (ungueltiges Element)', () => {
+    const bad = { id: 'x', type: 'arc', layerId: 'l', x: 0, y: 0, width: 0, height: 0, properties: {} } as unknown as CADElement;
+    expect(lineArcIntersection({ x: -10, y: -10 }, { x: 10, y: 10 }, bad)).toEqual([]);
+  });
+});

frontend/tests/helpers.smoke.test.ts

@@ -0,0 +1,74 @@
+/**
+ * Smoke-Tests für die Test-Helfer aus Task A0.
+ * Stellt sicher, dass Logger, MockRenderEngine und InMemoryDoc funktionieren,
+ * BEVOR spätere Tasks auf ihnen aufbauen.
+ */
+import { describe, it, expect, vi } from 'vitest';
+import { logger, setLogLevel } from '../src/utils/logger';
+import { MockRenderEngine } from './helpers/mockAdapter';
+import { createInMemoryDoc, makeTestLayer } from './helpers/inMemoryDoc';
+import type { CADElement } from '../src/types/cad.types';
+
+describe('A0 helpers – logger', () => {
+  it('schreibt info im Default-Level in die Testumgebung', () => {
+    const spy = vi.spyOn(console, 'log').mockImplementation(() => {});
+    setLogLevel('info');
+    logger.info('smoke test message');
+    expect(spy).toHaveBeenCalledWith('[web-cad]', 'smoke test message');
+    spy.mockRestore();
+  });
+
+  it('debug bleibt bei Level info still und erscheint bei debug', () => {
+    const spy = vi.spyOn(console, 'log').mockImplementation(() => {});
+    setLogLevel('info');
+    logger.debug('hidden');
+    expect(spy).not.toHaveBeenCalled();
+    setLogLevel('debug');
+    logger.debug('visible');
+    expect(spy).toHaveBeenCalledWith('[web-cad][debug]', 'visible');
+    spy.mockRestore();
+  });
+});
+
+describe('A0 helpers – MockRenderEngine', () => {
+  it('protokolliert Aufrufe mit Reihenfolge und Argumenten', () => {
+    const mock = new MockRenderEngine();
+    mock.render();
+    mock.hitTest(10, 20, 5);
+    mock.setPreviewElement(null);
+
+    expect(mock.countCalls('render')).toBe(1);
+    expect(mock.countCalls('hitTest')).toBe(1);
+    expect(mock.lastArgsOf('hitTest')).toEqual([10, 20, 5]);
+    expect(mock.calls.map((c) => c.method)).toEqual(['render', 'hitTest', 'setPreviewElement']);
+  });
+
+  it('liefert konfigurierbare hitTest-Ergebnisse', () => {
+    const mock = new MockRenderEngine();
+    const el = { id: 'e1', type: 'line' } as unknown as CADElement;
+    mock.nextHitTestResult = el;
+    expect(mock.hitTest(0, 0)).toBe(el);
+    mock.reset();
+    expect(mock.hitTest(0, 0)).toBeNull();
+  });
+});
+
+describe('A0 helpers – createInMemoryDoc', () => {
+  it('erstellt netzwerkfreies Dokument mit Seeding', () => {
+    const { ydoc, addAll } = createInMemoryDoc();
+    ydoc.data.layers.set('layer-1', makeTestLayer() as never);
+    const el = { id: 'el1', type: 'rect', layerId: 'layer-1', x: 0, y: 0, width: 1, height: 1, properties: {} } as unknown as CADElement;
+    addAll([el]);
+    expect(ydoc.getElements().length).toBe(1);
+    expect(ydoc.getLayers().length).toBe(1);
+  });
+
+  it('clear entfernt alle Elemente', () => {
+    const { ydoc, addAll, clear } = createInMemoryDoc();
+    const el = { id: 'el1', type: 'rect', layerId: 'layer-1', x: 0, y: 0, width: 1, height: 1, properties: {} } as unknown as CADElement;
+    addAll([el]);
+    expect(ydoc.getElements().length).toBe(1);
+    clear();
+    expect(ydoc.getElements().length).toBe(0);
+  });
+});

frontend/tests/helpers/inMemoryDoc.ts

@@ -0,0 +1,52 @@
+/**
+ * InMemoryDoc-Helper – Netzwerkfreie YjsDocument-Fabrik für Tests.
+ *
+ * YjsDocument läuft bereits komplett In-Memory (Y.Doc ohne Provider);
+ * dieser Wrapper bietet bequemes Seeding und Reset für isolierte Tests.
+ * Genutzt ab A3 (Tool-Workflow-Tests) und A2b (CADDocument-Tests).
+ */
+import { YjsDocument } from '../../src/crdt/YjsDocument';
+import type { CADElement } from '../../src/types/cad.types';
+
+export interface SeededDoc {
+  ydoc: YjsDocument;
+  /** Fügt Elemente in EINER Transaktion hinzu (1 Undo-Schritt). */
+  addAll(elements: CADElement[]): void;
+  /** Entfernt alle Elemente/Layer-Inhalte (Dokument bleibt verwendbar). */
+  clear(): void;
+}
+
+/** Erzeugt ein frisches, leeres Test-Dokument. */
+export function createInMemoryDoc(): SeededDoc {
+  const ydoc = new YjsDocument();
+  return {
+    ydoc,
+    addAll(elements) {
+      ydoc.doc.transact(() => {
+        for (const el of elements) ydoc.data.elements.set(el.id, el);
+      });
+    },
+    clear() {
+      ydoc.doc.transact(() => {
+        for (const id of Array.from(ydoc.data.elements.keys())) {
+          ydoc.data.elements.delete(id);
+        }
+      });
+    },
+  };
+}
+
+/** Basis-CADLayer für Tests. */
+export function makeTestLayer(id = 'layer-1', name = 'Test-Layer') {
+  return {
+    id,
+    name,
+    visible: true,
+    locked: false,
+    color: '#ffffff',
+    lineType: 'solid',
+    transparency: 0,
+    sortOrder: 0,
+    parentId: null,
+  };
+}

frontend/tests/helpers/mockAdapter.ts

@@ -0,0 +1,69 @@
+/**
+ * MockAdapter – Headless-Doppel der RenderEngine für Workflow-Tests.
+ * Zeichnet nichts; protokolliert alle Aufrufe in `calls` (Reihenfolge getreu).
+ *
+ * Methodenumfang = genau das, was InteractionEngine derzeit an RenderEngine
+ * ruft (verifiziert in Task A0): hitTest, render, setActiveSnapPoint,
+ * setOptions, setPreviewElement, setSnapPoints.
+ * Wird in C1 (RenderAdapter-Interface) um die vollen Adapter-Methoden erweitert.
+ */
+import type { CADElement } from '../../src/types/cad.types';
+
+export interface RecordedCall {
+  method: string;
+  args: unknown[];
+}
+
+export class MockRenderEngine {
+  /** Alle Aufrufe in Reihenfolge. */
+  readonly calls: RecordedCall[] = [];
+
+  /** Von Tests konfigurierbare hitTest-Rückgabe. */
+  nextHitTestResult: CADElement | null = null;
+
+  // ── Von InteractionEngine genutzte Fläche ────────────────
+
+  hitTest(x: number, y: number, tolerance?: number): CADElement | null {
+    this.calls.push({ method: 'hitTest', args: [x, y, tolerance] });
+    return this.nextHitTestResult;
+  }
+
+  render(): void {
+    this.calls.push({ method: 'render', args: [] });
+  }
+
+  setActiveSnapPoint(pt: unknown): void {
+    this.calls.push({ method: 'setActiveSnapPoint', args: [pt] });
+  }
+
+  setOptions(opts: Record<string, unknown>): void {
+    this.calls.push({ method: 'setOptions', args: [opts] });
+  }
+
+  setPreviewElement(el: CADElement | null): void {
+    this.calls.push({ method: 'setPreviewElement', args: [el] });
+  }
+
+  setSnapPoints(pts: unknown[]): void {
+    this.calls.push({ method: 'setSnapPoints', args: [pts] });
+  }
+
+  // ── Test-Helfer ──────────────────────────────────────────
+
+  /** Anzahl Aufrufe einer Methode. */
+  countCalls(method: string): number {
+    return this.calls.filter((c) => c.method === method).length;
+  }
+
+  /** Letzte aufgezeichnete Argumentliste einer Methode (oder undefined). */
+  lastArgsOf(method: string): unknown[] | undefined {
+    const found = this.calls.filter((c) => c.method === method);
+    return found.length ? found[found.length - 1].args : undefined;
+  }
+
+  /** Protokoll leeren. */
+  reset(): void {
+    this.calls.length = 0;
+    this.nextHitTestResult = null;
+  }
+}

frontend/tests/mockAdapter.test.ts

@@ -0,0 +1,82 @@
+/**
+ * MockAdapter Smoke-Tests (Task C1).
+ * Headless-Mock erfüllt RenderAdapter-Vertrag und protokolliert Aufrufe —
+ * Grundlage für zukünftige Renderer-/Tool-Unit-Tests.
+ */
+import { describe, it, expect } from 'vitest';
+import { MockAdapter } from '../src/render/mock/MockAdapter';
+import type { RenderAdapter, Viewport } from '../src/render/types';
+import type { CADElement, CADLayer } from '../src/types/cad.types';
+import type { Pt } from '../src/tools/modification/geometry';
+
+function makeLayer(): CADLayer {
+  return {
+    id: 'layer-1', name: 'L1', visible: true, locked: false,
+    color: '#ffffff', lineType: 'solid', transparency: 0,
+    sortOrder: 0,
+    parentId: null,
+  } as unknown as CADLayer;
+}
+
+function makeEl(id = 'e1'): CADElement {
+  return {
+    id,
+    type: 'line',
+    layerId: 'layer-1',
+    x: 10,
+    y: 10,
+    width: 20,
+    height: 20,
+    properties: {},
+  } as unknown as CADElement;
+}
+
+describe('MockAdapter implements RenderAdapter', () => {
+  it('ist einem RenderAdapter zuweisbar (Compile-proof)', () => {
+    const adapter = new MockAdapter();
+    const asAdapter: RenderAdapter = adapter;
+    expect(asAdapter).toBeDefined();
+  });
+
+  it('protokolliert init/resize/clear/drawElement in Reihenfolge', () => {
+    const adapter = new MockAdapter();
+    const canvas = document.createElement('canvas');
+    adapter.init(canvas);
+    adapter.resize(800, 600, 2);
+    const vp: Viewport = { x: 0, y: 0, scale: 1, width: 800, height: 600 };
+    adapter.setViewport(vp);
+    adapter.clear('#101018');
+    adapter.drawElement(makeEl(), makeLayer(), {
+      color: '#fff', lineType: 'solid', transparency: 0, visible: true,
+    });
+
+    expect(adapter.calls.map((c) => c.method)).toEqual([
+      'init', 'resize', 'setViewport', 'clear', 'drawElement',
+    ]);
+    expect(adapter.countCalls('drawElement')).toBe(1);
+  });
+
+  it('hitTest liefert konfigurierbaren Treffer; overlay-Callback wird ausgefuehrt', () => {
+    const adapter = new MockAdapter();
+    const el = makeEl('target');
+    adapter.nextHitTestResult = el;
+    let drewRect = false;
+    adapter.overlay(() => {
+      drewRect = true;
+    });
+    const pt: Pt = { x: 5, y: 5 };
+    const hit = adapter.hitTest(pt, 3);
+    expect(hit?.id).toBe('target');
+    expect(drewRect).toBe(true);
+  });
+
+  it('reset leert Protokoll und Treffer-Konfiguration', () => {
+    const adapter = new MockAdapter();
+    adapter.nextHitTestResult = makeEl('tmp');
+    adapter.overlay(() => {});
+    adapter.reset();
+    expect(adapter.calls.length).toBe(0);
+    const pt: Pt = { x: 0, y: 0 };
+    expect(adapter.hitTest(pt, 1)).toBeNull();
+  });
+});

frontend/tests/pilotTools.test.ts

@@ -0,0 +1,924 @@
+/**
+ * Pilot V2-Tools Tests (Task A3): line + select.
+ * line: Handler-Sequenz gegen echtes CADDocument (In-Memory), Undo-Verhalten.
+ * select: Bridge-basierte Auswahl mit Shift/Ctrl.
+ */
+import { describe, it, expect, vi } from 'vitest';
+import { lineTool, coreDrawingPlugin } from '../src/plugins/builtin/core-drawing';
+import { selectTool, coreModifyPlugin } from '../src/plugins/builtin/core-modify';
+import { coreAnnotatePlugin } from '../src/plugins/builtin/core-annotate';
+import { coreMeasurePlugin } from '../src/plugins/builtin/core-measure';
+import { eventToolsV2Plugin } from '../src/plugins/builtin/event-tools';
+import { CADDocument } from '../src/kernel/document/CADDocument';
+import { createInMemoryDoc } from './helpers/inMemoryDoc';
+import type { ToolPointerEvent, FullToolContext } from '../src/plugins/types';
+import type { CADElement } from '../src/types/cad.types';
+
+function pe(x: number, y: number, mods: Partial<Pick<ToolPointerEvent, 'shift' | 'ctrl'>> = {}): ToolPointerEvent {
+  return {
+    world: { x, y },
+    screen: { x: x / 2, y: y / 2 },
+    button: 0,
+    shift: mods.shift ?? false,
+    alt: false,
+    ctrl: mods.ctrl ?? false,
+  };
+}
+
+function makeCtx(overrides: Partial<FullToolContext> = {}): FullToolContext & { previews: (CADElement | null)[]; statuses: string[] } {
+  const previews: (CADElement | null)[] = [];
+  const statuses: string[] = [];
+  return {
+    options: {},
+    setStatus: (m) => statuses.push(m),
+    setPreview: (el) => previews.push(el),
+    previews,
+    statuses,
+    ...overrides,
+  } as FullToolContext & { previews: (CADElement | null)[]; statuses: string[] };
+}
+
+function makeEl(id: string): CADElement {
+  return { id, type: 'rect', layerId: 'l', x: 0, y: 0, width: 1, height: 1, properties: {} } as unknown as CADElement;
+}
+
+describe('A3 pilot: line tool', () => {
+  it('erzeugt EINE Linie per down→up; ein undo entfernt sie', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const ctx = makeCtx({ doc });
+
+    lineTool.handlers.down!(pe(0, 0), ctx);
+    lineTool.handlers.move!(pe(100, 50), ctx);
+    expect(ctx.previews.length).toBe(1);       // Live-Vorschau war da
+    lineTool.handlers.up!(pe(100, 50), ctx);
+
+    const all = doc.getAllElements();
+    expect(all.length).toBe(1);
+    expect(all[0].type).toBe('line');
+    expect(all[0].properties.x1).toBe(0);
+    expect(all[0].properties.y2).toBe(50);
+
+    // Kern-Akzeptanz aus ROADMAP: Ein Werkzeug-Klick = ein Undo-Schritt
+    expect(doc.undo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(0);
+  });
+
+  it('cancel verwirft die laufende Linie ohne Element', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const ctx = makeCtx({ doc });
+
+    lineTool.handlers.down!(pe(5, 5), ctx);
+    lineTool.handlers.cancel!(ctx);
+    lineTool.handlers.up!(pe(9, 9), ctx);      // up nach cancel: kein Start mehr
+
+    expect(doc.getAllElements().length).toBe(0);
+  });
+
+  it('Plugin-Manifest ist registrierbar und tagged basic', () => {
+    expect(coreDrawingPlugin.manifest.enabledByDefault).toBe(true);
+    const line = coreDrawingPlugin.tools?.find((t) => t.manifest.id === 'line');
+    expect(line?.manifest.tags).toContain('basic');
+  });
+});
+
+describe('A4.3 pilot: circle tool', () => {
+  it('erzeugt Kreis Zentrum+Radius; ein undo entfernt ihn', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const ctx = makeCtx({ doc });
+    const circle = coreDrawingPlugin.tools!.find((t) => t.manifest.id === 'circle')!;
+
+    circle.handlers.down!(pe(100, 100), ctx);
+    circle.handlers.move!(pe(200, 100), ctx);
+    expect(ctx.previews.length).toBe(1);
+    circle.handlers.up!(pe(200, 100), ctx);
+
+    const all = doc.getAllElements();
+    expect(all.length).toBe(1);
+    expect(all[0].type).toBe('circle');
+    expect(all[0].x).toBe(100);
+    expect(all[0].properties.radius).toBe(100); // Distanz wie Legacy
+
+    expect(doc.undo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(0);
+  });
+});
+
+describe('A4.3 pilot: arc tool', () => {
+  it('klick-progressiv: Zentrum→Start→Ende committet beim 3. Klick mit Grad-Winkeln', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const ctx = makeCtx({ doc });
+    const arc = coreDrawingPlugin.tools!.find((t) => t.manifest.id === 'arc')!;
+
+    // Klick 1: Zentrum (up gehört zum Klick, committet NICHT — klick-progressiv)
+    arc.handlers.down!(pe(0, 0), ctx);
+    expect(doc.getAllElements().length).toBe(0); // Phase 1/2 committet nie
+
+    // Klick 2: Startpunkt auf Radius 50 nach Osten (0°)
+    arc.handlers.down!(pe(50, 0), ctx);
+    expect(doc.getAllElements().length).toBe(0);
+
+    // Klick 3: Endpunkt oben (90°) → JETZT committet der dritte down
+    arc.handlers.down!(pe(0, 50), ctx);
+
+    const all = doc.getAllElements();
+    expect(all.length).toBe(1);
+    expect(all[0].type).toBe('arc');
+    expect(all[0].x).toBe(0);
+    expect(all[0].y).toBe(0);
+    expect(all[0].properties.radius).toBe(50);
+    expect(all[0].properties.startAngle).toBeCloseTo(0);
+    expect(all[0].properties.endAngle).toBeCloseTo(90);
+
+    expect(doc.undo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(0);
+  });
+
+  it('cancel bricht mehrphasige Sitzung vollstaendig ab', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const ctx = makeCtx({ doc });
+    const arc = coreDrawingPlugin.tools!.find((t) => t.manifest.id === 'arc')!;
+
+    arc.handlers.down!(pe(0, 0), ctx);      // phase 1
+    arc.handlers.down!(pe(30, 0), ctx);     // phase 2
+    arc.handlers.cancel!(ctx);              // reset
+    arc.handlers.down!(pe(99, 99), ctx);    // startet neu bei phase 1
+
+    // Kein Commit erfolgt (nur phase 1), nichts im Doc:
+    expect(doc.getAllElements().length).toBe(0);
+  });
+});
+
+describe('A4.3 pilot: polyline/polygon tools', () => {
+  it('polyline sammelt Punkte und committet per ENTER ab 2', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const ctx = makeCtx({ doc });
+    const pl = coreDrawingPlugin.tools!.find((t) => t.manifest.id === 'polyline')!;
+
+    pl.handlers.down!(pe(0, 0), ctx);
+    pl.handlers.move!(pe(10, 10), ctx);
+    expect(ctx.previews.length).toBeGreaterThan(0);
+    pl.handlers.down!(pe(20, 0), ctx);
+    pl.handlers.down!(pe(30, 30), ctx);
+
+    const kev = { key: 'Enter', preventDefault: () => {} } as unknown as KeyboardEvent;
+    const consumed = pl.handlers.key!(kev, ctx);
+    expect(consumed).toBe(true);
+
+    const all = doc.getAllElements();
+    expect(all.length).toBe(1);
+    expect(all[0].type).toBe('polyline');
+    expect((all[0].properties.points as Pt[]).length).toBe(3);
+    expect(all[0].x).toBe(15); // BBox-Zentrum min0 max30
+
+    expect(doc.undo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(0);
+  });
+
+  it('polygon braucht mind. 3 Punkte; ENTER davor meldet Hinweis', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const pg = coreDrawingPlugin.tools!.find((t) => t.manifest.id === 'polygon')!;
+    const ctx = makeCtx({ doc });
+
+    pg.handlers.down!(pe(0, 0), ctx);
+    pg.handlers.down!(pe(10, 10), ctx);
+    const kev = { key: 'Enter', preventDefault: () => {} } as unknown as KeyboardEvent;
+    pg.handlers.key!(kev, ctx);   // nur 2 Punkte → abgelehnt
+    expect(doc.getAllElements().length).toBe(0);
+    expect(ctx.statuses.some((s) => s.includes('mindestens 3'))).toBe(true);
+
+    pg.handlers.down!(pe(20, -5), ctx);
+    pg.handlers.key!(kev, ctx);   // jetzt 3 Punkte → ok
+    const all = doc.getAllElements();
+    expect(all.length).toBe(1);
+    expect(all[0].type).toBe('polygon');
+    expect((all[0].properties.points as Pt[]).length).toBe(3);
+  });
+});
+
+describe('A4.4 pilot: annotate tools', () => {
+  it('dimension: down→up committet mit x1..y2-Properties; undo entfernt', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const ctx = makeCtx({ doc });
+    const dim = coreAnnotatePlugin.tools!.find((t) => t.manifest.id === 'dimension')!;
+
+    dim.handlers.down!(pe(0, 0), ctx);
+    dim.handlers.move!(pe(60, 0), ctx);   // Preview war da
+    expect(ctx.previews.length).toBe(1);
+    dim.handlers.up!(pe(60, 0), ctx);
+
+    const all = doc.getAllElements();
+    expect(all.length).toBe(1);
+    expect(all[0].type).toBe('dimension');
+    expect(all[0].x).toBe(30);                     // Mitte
+    expect(all[0].properties.x2).toBe(60);
+    expect(all[0].width).toBeCloseTo(60);          // dist als Breite wie Legacy
+
+    expect(doc.undo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(0);
+  });
+
+  it('leader: übernimmt Text/fontSize-Konvention aus Legacy', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const ctx = makeCtx({ doc });
+    const leader = coreAnnotatePlugin.tools!.find((t) => t.manifest.id === 'leader')!;
+
+    leader.handlers.down!(pe(10, 20), ctx);
+    leader.handlers.up!(pe(80, 90), ctx);
+
+    const all = doc.getAllElements();
+    expect(all.length).toBe(1);
+    expect(all[0].type).toBe('leader');
+    expect(all[0].properties.x1).toBe(10);
+    expect(all[0].properties.y2).toBe(90);
+    expect(all[0].properties.text).toBe('');
+    expect(all[0].properties.fontSize).toBe(12);
+  });
+
+  it('text: Einzelklick platziert leeres Textelement mit fontSize-Option', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const ctx = makeCtx({ doc, options: { fontSize: 18 } });
+    const txt = coreAnnotatePlugin.tools!.find((t) => t.manifest.id === 'text')!;
+
+    txt.handlers.down!(pe(40, 70), ctx);   // kein up nötig — single-point tool
+
+    const all = doc.getAllElements();
+    expect(all.length).toBe(1);
+    expect(all[0].type).toBe('text');
+    expect(all[0].x).toBe(40);
+    expect(all[0].y).toBe(70);
+    expect(all[0].width).toBe(100);        // Legacy-Default-BBox
+    expect(all[0].properties.fontSize).toBe(18); // aus options statt Default 12
+    expect(all[0].properties.text).toBe('');
+  });
+});
+
+describe('A4.5 pilot: revcloud tool', () => {
+  it('committet per ENTER ab 3 Punkten mit Legacy-Konvention arcHeight=8', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const ctx = makeCtx({ doc });
+    const cloud = coreDrawingPlugin.tools!.find((t) => t.manifest.id === 'revcloud')!;
+
+    cloud.handlers.down!(pe(0, 0), ctx);
+    cloud.handlers.down!(pe(100, 0), ctx);
+    cloud.handlers.down!(pe(100, 50), ctx);
+    const kev = { key: 'Enter', preventDefault: () => {} } as unknown as KeyboardEvent;
+    const consumed = cloud.handlers.key!(kev, ctx);
+    expect(consumed).toBe(true);
+
+    const all = doc.getAllElements();
+    expect(all.length).toBe(1);
+    expect(all[0].type).toBe('revcloud');
+    expect((all[0].properties.points as Pt[]).length).toBe(3);
+    expect(all[0].properties.arcHeight).toBe(8);   // Legacy-Konvention
+    expect(all[0].properties.fill).toBe('none');
+
+    expect(doc.undo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(0);
+  });
+});
+
+describe('A4.5 pilot: measure tool', () => {
+  it('2 Klicks zeigen Distanz+Winkel im Status; erzeugt KEIN Element', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const ctx = makeCtx({ doc });
+    const meas = coreMeasurePlugin.tools!.find((t) => t.manifest.id === 'measure')!;
+
+    meas.handlers.down!(pe(0, 0), ctx);
+    expect(ctx.statuses.some((s) => s.includes('Endpunkt'))).toBe(true);
+
+    meas.handlers.down!(pe(30, 40), ctx);   // dist=50, angle≈53.13°
+    const last = ctx.statuses[ctx.statuses.length - 1];
+    expect(last).toContain('distance:');
+    expect(last).toContain('angle:');
+    expect(last).toContain('53.1');          // atan2(40,30)≈53.13°
+    // KernLegacy-Verhalten: Messung erzeugt kein Element
+    expect(doc.getAllElements().length).toBe(0);
+  });
+});
+
+describe('A4.5 pilot: hatch tool', () => {
+  it('setzt hatch-Properties via updateElement; undo macht rückgängig', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    // Seed-Rect im Doc, das beim hitTest zurückkommt:
+    const rectEl = { id: 'r1', type: 'rect', layerId: 'l', x: 50, y: 50, width: 10, height: 10, properties: {} } as unknown as CADElement;
+    doc.addElement(rectEl);
+    const bridge = {
+      getIds: () => [],
+      setIds: () => {},
+      hitTest: () => rectEl,
+    };
+    const ctx = makeCtx({ doc, selection: bridge, options: { hatchPattern: 'cross', hatchSpacing: 12 } });
+    const hatch = coreModifyPlugin.tools!.find((t) => t.manifest.id === 'hatch')!;
+
+    hatch.handlers.down!(pe(50, 50), ctx);
+
+    const updated = doc.getElement('r1')!;
+    expect(updated.properties.hatch).toBe(true);
+    expect(updated.properties.hatchPattern).toBe('cross');   // aus Options
+    expect(updated.properties.hatchSpacing).toBe(12);
+
+    expect(doc.undo()).toBe(true);  // A2b-Update ist selbst Undo-Schritt
+    expect(doc.getElement('r1')!.properties.hatch).toBeUndefined();
+  });
+
+  it('lehnt offene Elementtypen (line) mit Hinweis ab', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const lineEl = { id: 'l1', type: 'line', layerId: 'l', x: 0, y: 0, width: 5, height: 5, properties: { x1: 0, y1: 0, x2: 5, y2: 5 } } as unknown as CADElement;
+    doc.addElement(lineEl);
+    const bridge = { getIds: () => [], setIds: () => {}, hitTest: () => lineEl };
+    const ctx = makeCtx({ doc, selection: bridge });
+    const hatch = coreModifyPlugin.tools!.find((t) => t.manifest.id === 'hatch')!;
+
+    hatch.handlers.down!(pe(2, 2), ctx);
+    expect(doc.getElement('l1')!.properties.hatch).toBeUndefined(); // nichts geändert
+    expect(ctx.statuses.some((s) => s.includes('rect/circle/polygon'))).toBe(true);
+  });
+});
+
+describe('A4.9 pilot: event tools', () => {
+  it('chair platziert Einzel-Element per Klick', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const ctx = makeCtx({ doc });
+    const chair = eventToolsV2Plugin.tools!.find((t) => t.manifest.id === 'chair')!;
+
+    chair.handlers.down!(pe(100, 200), ctx);
+    const all = doc.getAllElements();
+    expect(all.length).toBe(1);
+    expect(all[0].type).toBe('chair');
+    expect(all[0].x).toBe(100);
+    expect(all[0].y).toBe(200);
+  });
+
+  it('seating-block erzeugt rows×cols Elemente in EINER Transaktion (ein undo = ganzer Block weg)', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const ctx = makeCtx({ doc });
+    const block = eventToolsV2Plugin.tools!.find((t) => t.manifest.id === 'seating-block')!;
+
+    block.handlers.down!(pe(0, 0), ctx);   // Legacy-Default: rows=3, cols=8
+    const all = doc.getAllElements();
+    expect(all.length).toBeGreaterThan(1);  // Multi-Element-Satz
+    expect(all.every((e) => e.type === 'chair')).toBe(true);
+
+    // BUG-1-Regressionsschutz: alle Reihen im Block haben eigene rowIds
+    const rowIds = new Set(all.map((e) => e.properties.rowId));
+    expect(rowIds.size).toBeGreaterThanOrEqual(3);
+
+    // Kern-Akzeptanz: EIN undo entfernt den GANZEN Block
+    expect(doc.undo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(0);
+  });
+
+  it('seating-row platziert mehrere Stühle mit gemeinsamer rowId; undo entfernt Reihe', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const ctx = makeCtx({ doc });
+    const row = eventToolsV2Plugin.tools!.find((t) => t.manifest.id === 'seating-row')!;
+
+    row.handlers.down!(pe(0, 0), ctx);
+    const all = doc.getAllElements();
+    expect(all.length).toBeGreaterThanOrEqual(2);
+    const rowIds = new Set(all.map((e) => e.properties.rowId));
+    expect(rowIds.size).toBe(1);            // eine Reihe → EINE rowId
+
+    expect(doc.undo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(0);
+  });
+});
+
+describe('A4.6 pilot: move/copy tools', () => {
+  it('move verschiebt selektierte Elemente in EINER Transaktion (undo entfernt Versatz)', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    doc.addElement(makeEl('m1'));
+    doc.addElement(makeEl('m2'));
+    let selIds = ['m1', 'm2'];
+    const bridge = {
+      getIds: () => selIds,
+      setIds: (ids: string[]) => {
+        selIds = ids;
+      },
+      hitTest: () => null,
+    };
+    const ctx = makeCtx({ doc, selection: bridge });
+    const move = coreModifyPlugin.tools!.find((t) => t.manifest.id === 'move')!;
+    const origM1x = doc.getElement('m1')!.x;
+    const origY = doc.getElement('m1')!.y;
+
+    move.handlers.down!(pe(0, 0), ctx);   // Basispunkt
+    move.handlers.down!(pe(50, -20), ctx); // Zielklick → Commit
+
+    expect(doc.getElement('m1')!.x).toBe(origM1x + 50);
+    expect(doc.getElement('m2')!.y).toBe(origY - 20);
+    // EINE Transaktion für beide → ein undo stellt beide wieder her:
+    expect(doc.undo()).toBe(true);
+    expect(doc.getElement('m1')!.x).toBe(origM1x);
+    expect(doc.getElement('m2')!.y).toBe(origY);
+  });
+
+  it('copy erzeugt neue Elemente (IDs neu) ohne Original zu veraendern', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    doc.addElement(makeEl('o1'));
+    let selIds = ['o1'];
+    const bridge = {
+      getIds: () => selIds,
+      setIds: (ids: string[]) => {
+        selIds = ids;
+      },
+      hitTest: () => null,
+    };
+    const ctx = makeCtx({ doc, selection: bridge });
+    const copy = coreModifyPlugin.tools!.find((t) => t.manifest.id === 'copy')!;
+
+    copy.handlers.down!(pe(0, 0), ctx);
+    copy.handlers.down!(pe(100, 100), ctx);
+
+    const all = doc.getAllElements();
+    expect(all.length).toBe(2);              // Original + Kopie
+    expect(all[0].id).toBe('o1');            // Original unberührt
+    expect(all[0].x).not.toBe(all[1].x);     // Kopie versetzt
+    expect(all[1].id).not.toBe('o1');        // neue ID
+    expect(all[1].type).toBe(all[0].type);   // gleicher Typ
+
+    expect(doc.undo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(1); // nur Original bleibt
+  });
+
+  it('Komfort: bei leerer Selektion wird Element unter Klick auto-gewählt', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const target = makeEl('auto');
+    target.x = 10;
+    target.y = 10;
+    doc.addElement(target);
+    let selIds2: string[] = [];
+    const bridge = {
+      getIds: () => selIds2,
+      setIds: (ids: string[]) => {
+        selIds2 = ids;
+      },
+      hitTest: () => target,
+    };
+    const ctx = makeCtx({ doc, selection: bridge });
+    const move = coreModifyPlugin.tools!.find((t) => t.manifest.id === 'move')!;
+
+    move.handlers.down!(pe(10, 10), ctx);   // Basis + Auto-Select
+    expect(selIds2).toEqual(['auto']);
+    move.handlers.down!(pe(30, 30), ctx);   // Zielklick (Δ=+20)
+
+    expect(doc.undo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(1);
+  });
+});
+
+describe('A4.10 pilot: geometry tools', () => {
+  function makeLineEl(id: string): CADElement {
+    return {
+      id,
+      type: 'line',
+      layerId: 'l',
+      x: 100,
+      y: 0,
+      width: 200,
+      height: 0,
+      properties: { x1: 0, y1: 0, x2: 200, y2: 0 },
+    } as unknown as CADElement;
+  }
+
+  function makeCircleEl(id: string): CADElement {
+    return {
+      id,
+      type: 'circle',
+      layerId: 'l',
+      x: 100,
+      y: 0,
+      width: 80,
+      height: 80,
+      properties: { radius: 40 },
+    } as unknown as CADElement;
+  }
+
+  it('trim: Kante+Ziel kürzt die Linie am Schnittpunkt; undo stellt her', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const boundary = makeCircleEl('bnd');
+    const target = makeLineEl('tgt');
+    doc.addElement(boundary);
+    doc.addElement(target);
+
+    // Sequenzieller Brücken-HitTest: 1. Klick → boundary, 2. Klick → target
+    const pickQueue = [boundary, target];
+    let pickIdx = 0;
+    const bridge = {
+      getIds: () => [] as string[],
+      setIds: () => {},
+      hitTest: () => pickQueue[Math.min(pickIdx++, pickQueue.length - 1)],
+    };
+    const ctx = makeCtx({ doc, selection: bridge });
+    const trim = coreModifyPlugin.tools!.find((t) => t.manifest.id === 'trim')!;
+
+    trim.handlers.down!(pe(140, 0), ctx);  // Kante
+    trim.handlers.down!(pe(180, 0), ctx);  // Ziel-Linie rechts vom Kreis
+
+    const trimmed = doc.getElement('tgt')!;
+    expect(trimmed.properties.x2).toBeLessThan(200);       // gekürzt
+    // Legacy-Semantik: das NÄHERE Ende wird auf den ERSTEN Schnittpunkt
+    // gesetzt (findIntersection wählt den nächsten zu p1 → x=60):
+    expect(Math.abs(trimmed.properties.x2 as number)).toBeCloseTo(60); // Schnitt bei x=140
+
+    expect(doc.undo()).toBe(true);
+    expect(doc.getElement('tgt')!.properties.x2).toBe(200);
+  });
+
+  it('extend: Linie wird zur Kante hin verlängert', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    // kurze Linie (10→50); Kreis (100,0,r=40) hat Schnitte bei x=60/140
+    // → Extend muss das nahe Ende x2 auf 60 strecken
+    const boundary = makeCircleEl('bnd');
+    const shortLine = {
+      id: 'sl', type: 'line', layerId: 'l', x: 30, y: 0,
+      width: 40, height: 0,
+      properties: { x1: 10, y1: 0, x2: 50, y2: 0 },
+    } as unknown as CADElement;
+    doc.addElement(boundary);
+    doc.addElement(shortLine);
+
+    const pickQueue = [boundary, shortLine];
+    let pickIdx = 0;
+    const bridge = {
+      getIds: () => [] as string[],
+      setIds: () => {},
+      hitTest: () => pickQueue[Math.min(pickIdx++, pickQueue.length - 1)],
+    };
+    const ctx = makeCtx({ doc, selection: bridge });
+    const extend = coreModifyPlugin.tools!.find((t) => t.manifest.id === 'extend')!;
+
+    extend.handlers.down!(pe(100, 40), ctx);
+    extend.handlers.down!(pe(45, 0), ctx);
+
+    const ext = doc.getElement('sl')!;
+    // Extend richtet das nahe Ende exakt auf den Schnittpunkt aus:
+    expect(ext.properties.x2).toBeCloseTo(60);
+
+    expect(doc.undo()).toBe(true);
+    expect(doc.getElement('sl')!.properties.x2).toBe(50); // Original-Länge
+  });
+});
+
+describe('A4.7 pilot: transform tools', () => {
+  it('rotate dreht um Pivot des ersten Elements; ein undo stellt zurück', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const rotEl = makeEl('r1');
+    doc.addElement(rotEl);
+    let selIds: string[] = ['r1'];
+    const bridge = {
+      getIds: () => selIds,
+      setIds: (ids: string[]) => { selIds = ids; },
+      hitTest: () => null,
+    };
+    const ctx = makeCtx({ doc, selection: bridge });
+    const rotate = coreModifyPlugin.tools!.find((t) => t.manifest.id === 'rotate')!;
+
+    // Basispunkt rechts vom Zentrum (0°-Richtung), Element x=10
+    rotate.handlers.down!(pe(60, 10), ctx);
+    // Referenzklick oben → Δwinkel ≈ +90° (CCW)
+    rotate.handlers.down!(pe(10, 60), ctx);
+
+    expect(doc.undo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(1);
+  });
+
+  it('scale vergrößert width/height um Faktor dist(pivot,zweiteKlick)/dist(pivot,basis)', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const sq = makeEl('s1');
+    sq.width = 40;
+    sq.height = 40;
+    sq.x = 0;
+    sq.y = 0;
+    doc.addElement(sq);
+    let selIds: string[] = ['s1'];
+    const bridge = {
+      getIds: () => selIds,
+      setIds: (ids: string[]) => { selIds = ids; },
+      hitTest: () => null,
+    };
+    const ctx = makeCtx({ doc, selection: bridge });
+    const scale = coreModifyPlugin.tools!.find((t) => t.manifest.id === 'scale')!;
+
+    // Basis bei Distanz 50 vom Pivot, Ziel bei 100 → Faktor 2
+    scale.handlers.down!(pe(50, 0), ctx);
+    scale.handlers.down!(pe(100, 0), ctx);
+
+    expect(doc.getElement('s1')!.width).toBeCloseTo(80);   // 40×2
+    expect(doc.getElement('s1')!.height).toBeCloseTo(80);
+
+    expect(doc.undo()).toBe(true);
+    expect(doc.getElement('s1')!.width).toBeCloseTo(40);
+  });
+
+  it('mirror spiegelt Element an Achse basis→referenz', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const el = makeEl('mi');
+    el.x = 30;
+    el.y = 0;
+    doc.addElement(el);
+    let selIds: string[] = ['mi'];
+    const bridge = {
+      getIds: () => selIds,
+      setIds: (ids: string[]) => { selIds = ids; },
+      hitTest: () => null,
+    };
+    const ctx = makeCtx({ doc, selection: bridge });
+    const mirror = coreModifyPlugin.tools!.find((t) => t.manifest.id === 'mirror')!;
+
+    // Spiegelachse = Y-Achse (basis (0,0)→ref (0,100)): Punkt (30,0)→(−30,0)
+    mirror.handlers.down!(pe(0, 0), ctx);
+    mirror.handlers.down!(pe(0, 100), ctx);
+
+    const mirrored = doc.getElement('mi')!;
+    expect(mirrored.x).toBeLessThan(0);        // jenseits der Achse
+    expect(Math.abs(mirrored.x)).toBeGreaterThanOrEqual(29); // ~spiegelsymmetrisch
+    expect(doc.undo()).toBe(true);
+  });
+});
+
+describe('A4.8 pilot: delete tool', () => {
+  it('löscht alle selektierten Elemente in EINER Transaktion; undo stellt her', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    doc.addElement(makeEl('d1'));
+    doc.addElement(makeEl('d2'));
+    doc.addElement(makeEl('keep'));
+    let selIds: string[] = ['d1', 'd2'];
+    const bridge = {
+      getIds: () => selIds,
+      setIds: (ids: string[]) => { selIds = ids; },
+      hitTest: () => null,
+    };
+    const ctx = makeCtx({ doc, selection: bridge });
+    const del = coreModifyPlugin.tools!.find((t) => t.manifest.id === 'delete')!;
+
+    del.handlers.down!(pe(0, 0), ctx);
+    const remaining = doc.getAllElements().map((e) => e.id);
+    expect(remaining).toEqual(['keep']);
+
+    expect(doc.undo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(3);
+  });
+
+  it('Direktklick ohne Selektion löscht getroffenes Element', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const el = makeEl('hitme');
+    el.x = 20;
+    el.y = 20;
+    doc.addElement(el);
+    const bridge = {
+      getIds: () => [] as string[],
+      setIds: () => {},
+      hitTest: () => el,
+    };
+    const ctx = makeCtx({ doc, selection: bridge });
+    const del = coreModifyPlugin.tools!.find((t) => t.manifest.id === 'delete')!;
+
+    del.handlers.down!(pe(20, 20), ctx);
+    expect(doc.getAllElements().length).toBe(0);
+  });
+});
+
+describe('A4.8 pilot: offset tool', () => {
+  it('erzeugt Versatz-Kopie mit Seitenparameter; Original bleibt', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const line = {
+      id: 'src1', type: 'line', layerId: 'l', x: 50, y: 0,
+      width: 100, height: 0,
+      properties: { x1: 0, y1: 0, x2: 100, y2: 0 },
+    } as unknown as CADElement;
+    doc.addElement(line);
+    let selIds: string[] = [];
+    const bridge = {
+      getIds: () => selIds,
+      setIds: (ids: string[]) => { selIds = ids; },
+      hitTest: () => line,
+    };
+    const ctx = makeCtx({ doc, selection: bridge });
+    const off = coreModifyPlugin.tools!.find((t) => t.manifest.id === 'offset')!;
+
+    off.handlers.down!(pe(50, 0), ctx);   // Klick1: Quelle wählen (Basis)
+    off.handlers.down!(pe(50, -30), ctx); // Klick2: Versatz nach oben (side=-1)
+
+    const all = doc.getAllElements();
+    expect(all.length).toBe(2);            // Original + Kopie
+    expect(all[0].id).toBe('src1');        // Original unberührt
+    expect(all[1].id.startsWith('off_')).toBe(true);
+    // side=-1 bei Rechtslaufender Linie → nach OBEN (y kleiner):
+    expect(all[1].properties.y1).toBe(-30);
+    expect(all[1].properties.y2).toBe(-30);
+    expect(all[1].properties.x1).toBe(0);  // x bleibt
+
+    expect(doc.undo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(1);
+  });
+});
+
+describe('A3 pilot: select tool', () => {
+  function makeBridge(elements: CADElement[]) {
+    let ids: string[] = [];
+    return {
+      bridge: {
+        getIds: () => ids,
+        setIds: (next: string[]) => {
+          ids = next;
+        },
+        hitTest: (wx: number, wy: number, tol: number): CADElement | null =>
+          elements.find((el) => Math.abs(el.x - wx) <= tol && Math.abs(el.y - wy) <= tol) ?? null,
+      },
+      getIds: () => ids,
+    };
+  }
+
+  it('wählt getroffenes Element ohne Modifier exklusiv', () => {
+    const els = [makeEl('a'), makeEl('b')];
+    els[0].x = 10; els[0].y = 10;
+    els[1].x = 500; els[1].y = 500;
+    const { bridge, getIds } = makeBridge(els);
+    const ctx = makeCtx({ selection: bridge });
+
+    selectTool.handlers.down!(pe(10, 10), ctx);
+    expect(getIds()).toEqual(['a']);
+
+    // Klick auf b ohne Shift ersetzt Selektion
+    selectTool.handlers.down!(pe(500, 500), ctx);
+    expect(getIds()).toEqual(['b']);
+  });
+
+  it('Shift addiert, Ctrl subtrahiert', () => {
+    const els = [makeEl('a'), makeEl('b'), makeEl('c')];
+    els[0].x = 10; els[0].y = 10;
+    els[1].x = 50; els[1].y = 50;
+    els[2].x = 90; els[2].y = 90;
+    const { bridge, getIds } = makeBridge(els);
+    const ctx = makeCtx({ selection: bridge });
+
+    selectTool.handlers.down!(pe(10, 10), ctx);
+    expect(getIds()).toEqual(['a']);
+
+    selectTool.handlers.down!(pe(50, 50, { shift: true }), ctx);
+    expect(getIds().sort()).toEqual(['a', 'b']);
+
+    selectTool.handlers.down!(pe(90, 90, { shift: true }), ctx);
+    expect(getIds().sort()).toEqual(['a', 'b', 'c']);
+
+    selectTool.handlers.down!(pe(50, 50, { ctrl: true }), ctx);
+    expect(getIds().sort()).toEqual(['a', 'c']);
+  });
+
+  it('Leerklick ohne Modifier leert die Selektion; Plugin tagged basic', () => {
+    const els = [makeEl('a')];
+    els[0].x = 10; els[0].y = 10;
+    const { bridge, getIds } = makeBridge(els);
+    const ctx = makeCtx({ selection: bridge });
+
+    selectTool.handlers.down!(pe(10, 10), ctx);
+    expect(getIds()).toEqual(['a']);
+    selectTool.handlers.down!(pe(999, 999), ctx);
+    expect(getIds()).toEqual([]);
+
+    expect(coreModifyPlugin.manifest.enabledByDefault).toBe(true);
+    const sel = coreModifyPlugin.tools?.find((t) => t.manifest.id === 'select');
+    expect(sel?.manifest.tags).toContain('basic');
+  });
+});
+
+describe('D-Ext: array-rect tool', () => {
+  it('vervielfaeltigt Selektion rows×cols in EINER Transaktion', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    doc.addElement(makeEl('a1'));
+    let selIds: string[] = ['a1'];
+    const bridge = {
+      getIds: () => selIds,
+      setIds: (ids: string[]) => { selIds = ids; },
+      hitTest: () => null,
+    };
+    const ctx = makeCtx({ doc, selection: bridge, options: { rows: 2, cols: 2, dx: 60, dy: 60 } });
+    const arr = coreModifyPlugin.tools!.find((t) => t.manifest.id === 'array-rect')!;
+
+    arr.handlers.down!(pe(0, 0), ctx);
+    arr.handlers.down!(pe(0, 0), ctx);
+
+    expect(doc.getAllElements().length).toBe(4);
+    expect(doc.undo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(1);
+  });
+});
+
+describe('D-Ext: array-polar tool', () => {
+  it('verteilt count Kopien gleichmaessig um das Zentrum', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    const elem = makeEl('p1');
+    elem.x = 100;
+    elem.y = 0;
+    doc.addElement(elem);
+    let selIds: string[] = ['p1'];
+    const bridge = {
+      getIds: () => selIds,
+      setIds: (ids: string[]) => { selIds = ids; },
+      hitTest: () => null,
+    };
+    const ctx = makeCtx({ doc, selection: bridge, options: { count: 4 } });
+    const polar = coreModifyPlugin.tools!.find((t) => t.manifest.id === 'array-polar')!;
+
+    polar.handlers.down!(pe(0, 0), ctx);
+    polar.handlers.down!(pe(0, 0), ctx);
+
+    const all = doc.getAllElements();
+    expect(all.length).toBe(4);
+    expect(doc.undo()).toBe(true);
+    expect(doc.getAllElements().length).toBe(1);
+  });
+});
+
+describe('C3fin interaktiv: handle-drag on select tool', () => {
+  function makeRect(id: string, x: number, y: number, w: number, h: number): CADElement {
+    return {
+      id, type: 'rect', layerId: 'l',
+      x: x + w / 2, y: y + h / 2,
+      width: w, height: h,
+      properties: { fill: '#abc' },
+    } as unknown as CADElement;
+  }
+
+  it('down auf Handle startet Drag, move skaliert, up committet', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    // Rect: (0,0) bis (50,50)
+    doc.addElement(makeRect('r1', 0, 0, 50, 50));
+    let selIds: string[] = ['r1'];
+    const bridge = {
+      getIds: () => selIds,
+      setIds: (ids: string[]) => { selIds = ids; },
+      hitTest: () => null,
+    };
+    const ctx = makeCtx({ doc, selection: bridge });
+    const select = coreModifyPlugin.tools!.find((t) => t.manifest.id === 'select')!;
+
+    // down auf Handle der oberen linken Ecke (0,0):
+    select.handlers.down!(pe(0, 0), ctx);
+    // move zu neuem Punkt (-20, -20):
+    select.handlers.move!(pe(-20, -20), ctx);
+    // up → Commit (Skalierung auf neue BBox von (-20,-20) bis (50,50)):
+    select.handlers.up!(pe(-20, -20), ctx);
+
+    const updated = doc.getElement('r1')!;
+    // Neue BBox: 70×70 statt 50×50:
+    expect(updated.width).toBe(70);
+    expect(updated.height).toBe(70);
+    expect(doc.undo()).toBe(true); // Skalierung ist undo-bar
+    expect(doc.getElement('r1')!.width).toBe(50);
+  });
+
+  it('down auf NICHT-Handle startet normale Selektion (kein Drag)', () => {
+    const { ydoc } = createInMemoryDoc();
+    const doc = new CADDocument(ydoc);
+    doc.addElement(makeRect('r2', 0, 0, 50, 50));
+    doc.addElement(makeRect('r3', 200, 200, 30, 30));
+    let selIds: string[] = ['r2'];
+    const bridge = {
+      getIds: () => selIds,
+      setIds: (ids: string[]) => { selIds = ids; },
+      // Klick bei (210,210) trifft r3:
+      hitTest: () => doc.getElement('r3')!,
+    };
+    const ctx = makeCtx({ doc, selection: bridge });
+    const select = coreModifyPlugin.tools!.find((t) => t.manifest.id === 'select')!;
+
+    // Klick weit weg von Handles von r2 (r2-Ecken sind 0/50):
+    select.handlers.down!(pe(210, 210), ctx);
+
+    // Normal-Selektion: r3 ist jetzt alleine selektiert (kein Drag gestartet):
+    expect(selIds).toEqual(['r3']);
+  });
+});

frontend/tests/pluginApiV2.test.ts

@@ -0,0 +1,106 @@
+/**
+ * Plugin-API v2 Tests (Task A1).
+ * Deckt: registerV2 / enableV2 / disableV2 / isV2Enabled,
+ * getToolsV2 (nur aktive Plugins), getPanels, getLibraryProviders,
+ * doppelte IDs verworfen, initDefaults mit V2.
+ */
+import { describe, it, expect, afterEach } from 'vitest';
+import { pluginRegistry } from '../src/plugins/PluginRegistry';
+import type {
+  PluginV2,
+  ToolExtensionV2,
+} from '../src/plugins/types';
+
+function makeTool(id: string): ToolExtensionV2 {
+  return {
+    manifest: { id, label: id, icon: '□', ribbonTab: 'tools' },
+    optionsSchema: [],
+    handlers: {},
+  };
+}
+
+function makePlugin(id: string, overrides: Partial<PluginV2> = {}): PluginV2 {
+  return {
+    manifest: {
+      id,
+      name: id,
+      version: '1.0.0',
+      author: 'test',
+      description: `Testplugin ${id}`,
+      category: 'tools',
+      enabledByDefault: false,
+    },
+    tools: [makeTool(`${id}-tool`)],
+    ...overrides,
+  };
+}
+
+describe('pluginRegistry v2', () => {
+  // Testisolierung: Singleton-Registry nach jedem Test vollständig räumen
+  const registered: string[] = [];
+  function track(plugin: PluginV2): void {
+    registered.push(plugin.manifest.id);
+    pluginRegistry.registerV2(plugin);
+  }
+  afterEach(() => {
+    while (registered.length > 0) {
+      pluginRegistry.unregisterV2(registered.pop()!);
+    }
+  });
+
+  it('registriert und aktiviert ein V2-Plugin; Tools erscheinen in getToolsV2', () => {
+    track(makePlugin('p1'));
+    expect(pluginRegistry.getToolsV2().length).toBe(0); // noch deaktiviert
+    pluginRegistry.enableV2('p1');
+    expect(pluginRegistry.isV2Enabled('p1')).toBe(true);
+    const tools = pluginRegistry.getToolsV2();
+    expect(tools.length).toBe(1);
+    expect(tools[0].manifest.id).toBe('p1-tool');
+    expect(pluginRegistry.getToolV2('p1-tool')?.manifest.id).toBe('p1-tool');
+  });
+
+  it('deaktivierte Plugins liefern keine Tools/Panels/Provider', () => {
+    track(
+      makePlugin('p2', {
+        panels: [{ id: 'panel-x', title: 'X', slot: 'left', render: () => document.createElement('div') }],
+        libraryProviders: [
+          {
+            id: 'lib-x',
+            label: 'Lib X',
+            listFolders: async () => [],
+            listBlocks: async () => [],
+            getBlock: async () => ({ id: 'b', folderId: '', name: '' }),
+          },
+        ],
+      }),
+    );
+    pluginRegistry.enableV2('p2');
+    expect(pluginRegistry.getPanels().length).toBe(1);
+    expect(pluginRegistry.getLibraryProviders().length).toBe(1);
+    pluginRegistry.disableV2('p2');
+    expect(pluginRegistry.isV2Enabled('p2')).toBe(false);
+    expect(pluginRegistry.getPanels().length).toBe(0);
+    expect(pluginRegistry.getLibraryProviders().length).toBe(0);
+    expect(pluginRegistry.getToolsV2().length).toBe(0);
+  });
+
+  it('verwirft doppelte Plugin-IDs ohne Fehler und behält das erste', () => {
+    const first = makePlugin('dup');
+    first.tools = [makeTool('first-tool')];
+    const second = makePlugin('dup');
+    second.tools = [makeTool('second-tool')];
+    track(first);
+    pluginRegistry.registerV2(second); // wird verworfen, muss nicht getrackt werden
+    pluginRegistry.enableV2('dup');
+    const ids = pluginRegistry.getToolsV2().map((t) => t.manifest.id);
+    expect(ids).toEqual(['first-tool']);
+  });
+
+  it('initDefaults aktiviert nur enabledByDefault-Plugins', () => {
+    track({ ...makePlugin('auto-on'), manifest: { ...makePlugin('auto-on').manifest, enabledByDefault: true } });
+    track(makePlugin('manual-off'));
+    pluginRegistry.initDefaults();
+    expect(pluginRegistry.isV2Enabled('auto-on')).toBe(true);
+    expect(pluginRegistry.isV2Enabled('manual-off')).toBe(false);
+  });
+});

frontend/tests/seating.count.test.ts

@@ -0,0 +1,84 @@
+/**
+ * Seating-Tests — countSeats: Zählung nach Reihe/Block/Gesamt.
+ * Ergänzt Task B5; Grundlage ist der BUG-1-Fix (rowId pro Block-Reihe).
+ */
+import { describe, it, expect } from 'vitest';
+import { SeatingService } from '../src/services/seatingService';
+import type { CADElement } from '../src/types/cad.types';
+
+function makeChair(id: string, props: Record<string, unknown> = {}): CADElement {
+  return {
+    id,
+    type: 'chair',
+    layerId: 'layer-1',
+    x: 0,
+    y: 0,
+    width: 50,
+    height: 50,
+    properties: props,
+  } as unknown as CADElement;
+}
+
+function makeNonChair(id: string): CADElement {
+  return {
+    id,
+    type: 'rect',
+    layerId: 'layer-1',
+    x: 0,
+    y: 0,
+    width: 10,
+    height: 10,
+    properties: {},
+  } as unknown as CADElement;
+}
+
+describe('countSeats', () => {
+  const svc = new SeatingService();
+
+  it('zählt eine freie Reihe korrekt (5 Stühle, 1 rowId)', () => {
+    const els = svc.createSeatingRow(0, 0, 'layer-1', { count: 5 });
+    const result = svc.countSeats(els);
+    expect(result.total).toBe(5);
+    expect(Object.keys(result.byRow).length).toBe(1);
+    expect(Object.values(result.byRow)[0]).toBe(5);
+    expect(Object.keys(result.byBlock).length).toBe(0);
+  });
+
+  it('zählt einen Block korrekt (3 Reihen × 4 Stühle = 12)', () => {
+    const els = svc.createSeatingBlock(0, 0, 'layer-1', { rows: 3, cols: 4 });
+    const result = svc.countSeats(els);
+    expect(result.total).toBe(12);
+    expect(Object.keys(result.byBlock).length).toBe(1);   // 1 Block
+    expect(Object.values(result.byBlock)[0]).toBe(12);
+    expect(Object.keys(result.byRow).length).toBe(3);     // 3 Reihen (BUG-1-Fix!)
+    for (const count of Object.values(result.byRow)) {
+      expect(count).toBe(4);                               // je Reihe 4 Stühle
+    }
+  });
+
+  it('summiert gemischte Zeichnung korrekt (Reihe + Block + Fremdelemente)', () => {
+    const rows = svc.createSeatingRow(0, 0, 'layer-1', { count: 3 });
+    const block = svc.createSeatingBlock(100, 100, 'layer-1', { rows: 2, cols: 2 });
+    const others = [makeNonChair('x1'), makeNonChair('x2')];
+    const all: CADElement[] = [...rows, ...block, ...others];
+    const result = svc.countSeats(all);
+    expect(result.total).toBe(7);          // 3 + 4, Nicht-Stühle ignorieren
+    expect(Object.keys(result.byRow).length).toBe(3); // 1 freie Reihe + 2 Block-Reihen
+    expect(Object.keys(result.byBlock).length).toBe(1);
+  });
+
+  it('liefert leere Summen bei leerer Eingabe', () => {
+    const result = svc.countSeats([]);
+    expect(result.total).toBe(0);
+    expect(result.byRow).toEqual({});
+    expect(result.byBlock).toEqual({});
+  });
+
+  it('zählt handgebaute Stühle ohne rowId nur im Gesamt', () => {
+    const els = [makeChair('h1'), makeChair('h2'), makeChair('h3', { rowId: 'row_manual' })];
+    const result = svc.countSeats(els);
+    expect(result.total).toBe(3);
+    expect(result.byRow['row_manual']).toBe(1);
+    expect(Object.keys(result.byRow).length).toBe(1);
+  });
+});

umbauplan-v2.md

@@ -0,0 +1,229 @@
+# Umbauplan web-cad v2.0 — Plugin-first, WebGL, Voll-CAD
+
+> ⚠️ **STATUS: ARCHIVIERTE PLANREFERENZ** — Die operative Umsetzung läuft über **[ROADMAP.md](./ROADMAP.md)**
+> (Tasks mit exakten Arbeitsschritten, Status, Fortschritts-Log).
+> Dieses Dokument bleibt als Begründung/Kontext stehen: Warum welche Entscheidungen getroffen wurden,
+> Marktvergleich, Risikoanalyse. Bei Abweichungen gilt immer ROADMAP.md.
+
+Stand: 2026-08-26 · Basis: Commit `126277a` (main)
+
+## Zielbild
+
+Web-CAD im Umfang einer Standard-2D-CAD-Software mit Event-Fokus:
+- **Alle Werkzeuge sind Plugins** — auch Kern-Werkzeuge (built-in Plugins haben keinen Sonderstatus mehr)
+- **WebGL-Renderer** (PixiJS) für große Pläne (50.000+ Elemente bei 60fps)
+- **Branchenneutrale Basis**: Grundrisse, Gelände, Flächen — nicht nur Veranstaltungen
+- **Library als First-Class-System**, erweiterbar durch Plugin-Kataloge
+- **Zwei Bedienmodi**: „Einfach“ für Einsteiger, „Pro“ für CAD-Anwender
+
+---
+
+## Architektur-Grundsätze
+
+1. **Core = Kernel only**: Datenmodell (CADElement/Layer), SpatialIndex, ZoomPan, History, Yjs-Sync, CommandRegistry, PluginRegistry. Kein einziges konkretes Werkzeug im Kernel.
+2. **Werkzeug = Plugin**: Jedes Werkzeug implementiert `ToolExtensionV2` mit eigenem Event-Zustand (onPointerDown/Move/Up/Key/Cancel), eigener Live-Vorschau über RenderAdapter-Overlay und Optionsleiste.
+3. **InteractionEngine wird Dispatcher**: Sie besitzt nur noch Event-Routing, aktives Tool delegieren, Undo-Transaktionen kapseln. Der aktuelle 1157-Zeilen-switch fällt weg.
+4. **RenderAdapter als Schnittstelle**: Alles Rendern läuft gegen eine schmale API (`clear/draw*/overlay/hitTest`), Implementierung PixiJS. Canvas2D entfällt (keine produktiven Nutzer → kein Legacy-Pfad).
+5. **Backend spiegelt Plugin-Lifecycle**: installierte Plugins, Versionen, Aktivierung pro Mandant/User in SQLite; Plugin-Bundles als ZIP mit Frontend-Code + optionalen Backend-Routen (sandboxed, manifest-signiert).
+6. **Datenmodell offen für Branchen**: `element.type` bleibt string; unbekannte Typen werden vom registrierenden Plugin gerendert (bereits vorhanden, wird zur Pflicht).
+
+---
+
+## Phase A — Plugin-first Refactoring (Kernel) · ca. 2 Wochen
+
+### A1 Plugin-API v2 (`frontend/src/plugins/types.ts`)
+- `ToolExtensionV2`: id, label, icon, ribbonTab, shortcut, cursor, optionsSchema (PropertyFields für Optionsleiste), `handlers: { onPointerDown/Move/Up/KeyDown/Cancel }`, `preview(adapter, state)`, `commit() -> Operation[]` (für Undo als eine Transaktion)
+- `PanelExtension`: eigene Sidebar-Panels (z.B. Bestuhlungsplaner, Gästeliste)
+- `LibraryProviderExtension`: liefert Kataloge (siehe Phase F)
+- `SnapProviderExtension`: zusätzliche Fangpunkte (z.B. Tangente eines Plugin-Elements)
+- `ImportExportExtension` behalten, um `formatId`, `mime`, `export(doc)`, `import(data)` erweitern
+- Manifest: `category` erweitert um `'library'`; neue Felder `minAppVersion`, `permissions[]` (canvas, network, storage)
+
+### A2 InteractionEngine zum Dispatcher umbauen
+- Neuer Vertrag: `setTool(toolId)` holt Tool aus PluginRegistry statt internem Switch
+- Undo/Redo: jedes Tool-commit wird eine HistoryManager-Transaktion (heute inkonsistent)
+- CommandRegistry bleibt; Commands aus Plugins bereits vorhanden
+- RibbonBar rendert dynamisch aus Registry (`getToolExtensions()` gruppiert nach ribbonTab) — Tabs bleiben konfigurierbar
+
+### A3 Kern-Tools als built-in Plugins migrieren
+| Plugin-Paket | Inhalt |
+|---|---|
+| `core-drawing` | line, polyline, rect, circle, arc, polygon, point, xline, ray, ellipse, spline |
+| `core-modify` | select, move, copy, rotate, scale, mirror, trim, extend, fillet, chamfer, offset, stretch, break, join, explode, align, array-rect, array-polar, array-path |
+| `core-annotate` | text, mtext, dimension-linear/-angular/-radial, leader, revcloud, hatch |
+| `core-measure` | measure, distance-info, area-info |
+| `event-tools` | chair, seating-row, seating-block, table, stage, templates (bestehend, erweitert) |
+
+Akzeptanz: `interaction/index.ts` < 300 LOC (nur Routing); alle 380 bestehenden Tests grün; Ribbon zeigt identische Werkzeuge wie zuvor.
+
+### A4 Backend: Plugin-Registrierung
+- SQLite-Tabelle `plugins(id, version, enabled_default, installed_at)` + `plugin_settings(plugin_id, scope, scope_id, json)`
+- REST `/api/plugins` (list), `/api/plugins/:id/settings` (GET/PUT), Admin-Upload `/api/plugins/install` (ZIP)
+- Websocket-Event `pluginStateChanged` → Clients aktivieren/deaktivieren live
+
+---
+
+## Phase B — Bugfixes (sofort, unabhängig) · 2–3 Tage
+
+1. `seatingService.ts`: `rowId`/`blockId` via UUID-Counter statt `Date.now()`; Block-Reihen erhalten eigene `rowId`
+2. `geometry.ts findIntersection`: Line–Circle, Circle–Circle, Line–Arc ergänzen (trim/extend/fillet funktionieren dann auf Kreisen/Bögen)
+3. Offset-Tool: Richtungssinn aus zweitem Klick (Vorzeichen der Seitigkeit per Kreuzprodukt)
+4. `RenderEngine.drawBackground`: Bild cachen (einmal laden), kein `img.onload → render()` pro Frame
+5. `countSeats`: byRow auch für Blöcke korrekt
+
+Jeder Fix mit Unit-Test. Diese Phase läuft parallel zu A und ändert Dateien, die B später ohnehin anfasst (Konflikt klein halten durch Reihenfolge: erst B, dann A-Migration je Tool).
+
+---
+
+## Phase C — WebGL-Renderer (PixiJS) · 3–5 Wochen
+
+### C1 RenderAdapter-Schnittstelle (`frontend/src/render/types.ts`)
+```
+interface RenderAdapter {
+  init(canvas), resize(w,h,dpr), setViewport(vp), destroy()
+  beginFrame(), endFrame()
+  drawGrid(cfg), drawBackground(img,cfg), drawRuler(cfg)
+  drawElement(el, layerStyle, scale)
+  drawPreview(el), drawSelection(el, handles), drawSnapPoints(pts)
+  drawOverlay(fn)   // Freihand-Overlays von Tools (Gummibänder, Arc-Row-Vorschau)
+}
+```
+
+### C2 PixiJS-Implementierung
+- Layer-Konzept: Graphics pro CAD-Layer, statische Elemente in Container mit Cache-as-Texture, dynamisches (Selection/Snap/Preview) in Overlay-Layer
+- Text: PIXI.Text/BitmapText; Dimensionen als Graphics + Label
+- Chair/Table/Stage: Texture-Atlas (einmal generiert, tausendfach instanziert) — der große Performance-Hebel für Bestuhlung
+- Grid/Ruler als getrennte Ticker-Layer, DPR-korrekt
+- Hintergrundbild als Sprite (löst gleichzeitig Bug #4 endgültig)
+
+### C3 Kompatibilität Plugin-Element-Renderer
+- `ElementTypeExtension.render(ctx)` erhält Adapter-Wrapper: zeichnet in Offscreen-Canvas → `Texture.from(canvas)` → Sprite. Bestehende Event-Elemente (curtain, spotlight, barrier) laufen unverändert weiter; später können Plugins nativen Pixi-Renderer liefern (`renderPixi?`).
+
+### C4 Tests & Benchmarks
+- 29 RenderEngine-Tests auf Adapter-Mock umschreiben (ca. 1 Tag Aufwand)
+- PerformanceBenchmark neu: 10k / 25k / 50k Chairs, Zielschwelle 60fps (Playwright + trace)
+- Feature-Flag `renderer=webgl` während Migration, danach Flag entfernen
+
+Akzeptanz: visuelle Parität zu Canvas2D (Screenshot-Vergleichstests), 50k Chairs @60fps auf Referenz-Hardware, alle Tests grün.
+
+---
+
+## Phase D — CAD-Werkzeuge komplettieren (alles Plugins) · 3–4 Wochen
+
+### D1 core-drawing Ergänzungen
+- Ellipse + Ellipsenbogen (Achsen-, Rotations-Eingabe)
+- Spline: Bézier (CV-Kontrolle) + Glättungs-Polyline-Interpolation; Speicherung als Kontrollpunkte
+- Punkt, Konstruktionslinien (XLine/Ray, eigene Layer-Klasse „construction“)
+- MTEXT: mehrzeilig, Inline-Formatierung (fett/kursiv/Größe), Autowrap-Box
+
+### D2 core-modify Ergänzungen
+- Stretch (Fenster über Polygonecken, Endpunkte verschieben)
+- Break (Element am Punkt teilen), Join (kollineare Segmente/Polylines fusionieren)
+- Chamfer (wie Fillet, gerade Kante), Explode (Block→Einzelelemente, Polyline→Segmente)
+- Align (2-Punkt-Ausrichtung inkl. Skalierung optional)
+- Lengthen (DElta/Total/Dynamisch)
+- Polyline-Editor: Segment hinzufügen/löschen, Kurven glätten, Breite
+- Grip-Editing: Ankerpunkte (Endpunkte/Mitte/Centre) direkt ziehen — großer Bedienkomfort-Gewinn
+
+### D3 Arrays
+- Rechteckig (Zeilen×Spalten×Abstände), Polar (Zentrum, Anzahl, Winkel, rotieren ja/nein), Pfad (entlang Polyline/Arc) — für Bestuhlung kritisch
+
+### D4 Snaps erweitern (SnapEngine + SnapProviderExtension)
+- Tangente, Senkrecht, Parallel, Quadrant, Center, Knoten, From-Offset (Basispunkt+Versatz)
+
+### D5 Block-Attribute
+- Datenmodell: Blockdefinition mit `attrDefs[]`, Instanz mit `attrValues[]`
+- Editor-UI (Attribut-Formular beim Einfügen), Anzeige im RenderAdapter
+- DXF-Interop: ATTDEF/ATTR lesen/schreiben (Phase F nutzt es)
+
+---
+
+## Phase E — Event-Domain ausbauen · 2 Wochen
+
+1. Interaktives Bestuhlungs-Werkzeug (im `event-tools` Plugin): Klick-Drag definiert Reihe/Block, Live-Vorschau via Overlay, Parameter (Anzahl, Abstand, Kurvenradius) in Optionsleiste
+2. **Arc-Rows**: Reihen entlang Kreisbogen um Bühnenpunkt (Radius, Winkelspread, Versatz)
+3. Sitzplatzzählung robust: byRow/byBlock/byZone, Summen in StatusBar, Klick auf Zahl highlightet Reihe
+4. Vorlagenkatalog: Kino, Bankett-Rundtische, Stehtische, Podeste, Parlamentarisch, U-Form
+5. Sitzplatzliste export (CSV/XLSX: Reihe, Platz, Zone, Gast optional)
+6. Optional (Backend): `guests`-Tabelle + Zuordnung seatId↔guest, CSV-Import — Vorbereitung Social-Tables-ähnlicher Funktion
+7. Event-Elemente veredeln: Bühne (mit Höhen-Angabe), Vorhang, Scheinwerfer (Farbe/Winkel), Barrieren (Kettenstücke), Fluchtweg-Signaturen
+
+---
+
+## Phase F — Library-System & Import/Export · 2–3 Wochen
+
+### F1 Library-Kern
+- Backend-Schema erweitern: `library_folders` (Baum, Mandant-scope), `library_blocks` (+ tags, thumbnail, attrDefs, source: builtin/user/plugin)
+- Suche (Name/Tags), Favoriten pro User, Drag-Drop ins Canvas, „Als Block speichern“ aus Auswahl
+- Thumbnail-Generierung client-seitig beim Speichern (kleines PNG dataURL)
+
+### F2 Library-Plugins
+- `LibraryProviderExtension`: `id`, `label`, `listFolders()`, `listBlocks(folder)`, `getBlock(id)`
+- Built-in Provider: `builtin-catalog` (mitgelieferte Kataloge: event, architecture, landscape), `user-library`, `global-library`
+- Plugin-Katalog-Pakete liefern Provider + Blöcke (Beispiel: „messe-plugin“ mit Standwand-Katalog)
+
+### F3 Import
+- DXF: Parser erweitern um ELLIPSE, SPLINE, MTEXT, POINT, HATCH (Basis), ATTDEF/ATTR; INSERT→Blockdefinition + Instanz; Layer-Mapping
+- SVG→Block (Vektor in Elemente konvertieren oder als referenzierter Render-Typ)
+- Bibliotheks-Pakete `.wcadlib` (ZIP: manifest.json + blocks.json + thumbnails) importieren
+- PNG/JPG als Hintergrund (vorhanden) + PDF-Unterlage beibehalten
+
+### F4 Export
+- `.wcadlib` Paket-Export (eigene Bibliothek teilen)
+- DXF-Export mit BLOCKS/INSERTS (Austausch mit AutoCAD/LibreCAD)
+- Bestehende Formate behalten: SVG, PDF, JSON
+
+---
+
+## Phase G — Layouts & Plot (Standard-CAD-Niveau) · 2 Wochen
+
+1. Paperspace/Layouts: mehrere Layouts pro Zeichnung, Viewports mit Maßstab 1:1…1:500, Rahmen/Titelblock als Block mit Attributen (Projekt, Datum, Maßstab, Bearbeiter)
+2. PDF-Export pro Layout in echtem Ausgabemaßstab (pdf-lib vorhanden)
+3. Plot-Stil: Linienstärken nach Farbe/Layer, monochrom-Option
+4. Drucken über Browser-Print (CSS @page) zusätzlich
+
+---
+
+## Phase H — Branchenneutralität & Einfachheit · 1–2 Wochen
+
+1. **Modus „Einfach/Pro“**: User-Setting; Simple-Mode blendet Ribbon nach `tool.tags:['basic']` (Auswahl, Stühle, Vorlagen, Text, Maß), versteckt CommandLine/Layer-Tiefe; Pro zeigt alles. Gleiche Engine, gleiche Daten.
+2. **Projekt-Templates**: Halle, Open Air, Saal, Messehalle, Bürogrundriss, Garten/Gelände — Template aktiviert passende Bibliotheks-Ordner + Plugin-Set + Rastermaßstab (m/cm/ft)
+3. **Rollen**: Library-Admin (global bearbeiten) vs. Nutzer (lesen, eigene Ordner) — an bestehendes 4-Rollen-Auth andocken
+4. i18n-Vorbereitung: Strings zentral (de/en), UI-Texte aus Bundle
+5. Gelände-Tauglichkeit: Polygon-Flächen mit Flächenberechnung (m²), Hang-/Höhen-Annotation als Text/Leader reicht v1; GIS-Anbindung bewusst out-of-scope
+
+---
+
+## Phase I — Qualität, CI, Release · 1 Woche
+
+- CI (Forgejo Actions): lint + tsc + vitest (FE 400+/BE 255+) + Playwright-Smoke + Performance-Gate (50k@60fps)
+- Test-Deckung Tools: jede ToolExtension braucht Workflow-Test (ziehen, snappen, committen, undo)
+- Docker/Coolify unverändert; Migrations-Scripte für SQLite-Schema (plugins, library, guests, layouts)
+- Docs: Plugin-Entwickler-Guide (API v2), Library-Paket-Spec, Changelog 2.0
+
+---
+
+## Meilensteine & Timeline
+
+| Milestone | Inhalt | ca. Woche |
+|---|---|---|
+| M1 | Phase B Bugfixes + A Plugin-first Kernel, Ribbon dynamisch | 2 |
+| M2 | C WebGL live hinter Flag, Parität + Benchmarks grün | 6 |
+| M3 | D volle Werkzeugpalette (Ellipse/Spline/Array/Grip/Attribute) | 10 |
+| M4 | E Event-Domain + F Library/Import-Export fertig | 13 |
+| M5 | G Layouts/PDF + H Modi/Templates + I Release 2.0 | 16–17 |
+
+Einzelarbeit ~4 Monate. Parallelisierung (z.B. B+C ein Track, D+F zweiter Track) verkürzt auf ~3 Monate.
+
+## Risiken
+
+1. **PixiJS-Textqualität bei Dimensionen** → früh Screenshot-Paritätstest, ggf. DOM-Overlay für Labels
+2. **Plugin-Sandboxing** (fremder Code im Browser) → v2 nur Admin-installierte, signierte Bundles; CSP; später Worker-Isolation
+3. **DXF-Sonderfälle** (SPLINE-Grad, HATCH-Grenzen) → Grenzen dokumentieren, Fehlertoleranz-Importer mit Report
+4. **Yjs + Layouts** → Layouts als Yjs-Map pro Projekt, Konfliktfreiheit gegeben
+
+## Offene Entscheidungen
+
+- PixiJS vs. Three.js-2D-Mode → Empfehlung PixiJS (Szene-Graph, Texture-Atlasten, kleiner)
+- Fremd-Plugins sofort erlaubt? → Empfehlung nein (nur first-party bis M5)
+- Gästemodul (E6) in 2.0 oder 2.1? → Empfehlung 2.1