diff --git a/frontend/src/plugins/builtin/core-drawing/index.ts b/frontend/src/plugins/builtin/core-drawing/index.ts
index 84b6691..65cd217 100644
--- a/frontend/src/plugins/builtin/core-drawing/index.ts
+++ b/frontend/src/plugins/builtin/core-drawing/index.ts
@@ -414,6 +414,150 @@ function buildRevCloud(pts: Pt[], ctx: FullToolContext): CADElement {
 }
 
 /** V2-Plugin: Kern-Zeichenwerkzeuge (A4.x schrittweise migriert). */
+// ─────────────────────────────────────────────────────────────
+// Task D1: Ellipse (3-Klick: Zentrum→RadiusX→RadiusY) +
+// Ellipsenbogen via startAngle/endAngle-Options.
+// ─────────────────────────────────────────────────────────────
+
+/** Ellipsen-Sitzung: Phase 0=nichts, 1=Zentrum, 2=RadiusX fixiert. */
+let ellipsePhase = 0;
+let ellipseCenter: Pt | null = null;
+let ellipseRadiusX = 0;
+/** Rotation aus der Klick2-Zugrichtung (Grad, 0°=+x, CW-positiv). */
+let ellipseRotationDeg = 0;
+
+/**
+ * Ellipse als Polyline-Approximation (F5-Parser-Konvention):
+ * Voll-Ellipse → 64 Punkte geschlossen (polygon), Bogen → proportional
+ * offene Polyline. rotation aus der Klick2-Zugrichtung (Grad, 0°=+x).
+ */
+function buildEllipse(
+  cx: number,
+  cy: number,
+  rx: number,
+  ry: number,
+  rotationDeg: number,
+  ctx: FullToolContext,
+  startAngle = 0,
+  endAngle = 360,
+): CADElement {
+  const stroke = (ctx.options.strokeColor as string | undefined) ?? '#e0e0f0';
+  const layerId = (ctx.options.layerId as string | undefined) ?? 'layer-0';
+  const phi = (rotationDeg * Math.PI) / 180;
+  const cosP = Math.cos(phi), sinP = Math.sin(phi);
+  const FULL = 360;
+  const span = Math.min(endAngle, FULL) - Math.min(startAngle, FULL);
+  const isFull = span >= FULL - 0.001 || span <= 0.001;
+  const n = Math.max(2, Math.round(64 * (Math.max(span, 1) / FULL)));
+  const pts: Pt[] = [];
+  for (let i = 0; i < n; i++) {
+    const t = ((startAngle + (span * i) / (isFull ? n : (n - 1))) * Math.PI) / 180;
+    const x = rx * Math.cos(t);
+    const y = ry * Math.sin(t);
+    pts.push({
+      x: cx + x * cosP - y * sinP,
+      y: cy + x * sinP + y * cosP,
+    });
+  }
+  const xs = pts.map((p) => p.x), ys = pts.map((p) => p.y);
+  const minX = Math.min(...xs), minY = Math.min(...ys);
+  const type = isFull ? 'polygon' : 'polyline';
+  return {
+    id: uid('ellipse'),
+    type,
+    layerId,
+    x: minX + (Math.max(...xs) - minX) / 2,
+    y: minY + (Math.max(...ys) - minY) / 2,
+    width: Math.max(...xs) - minX,
+    height: Math.max(...ys) - minY,
+    properties: {
+      points: pts,
+      stroke,
+      strokeWidth: 1,
+      cx, cy, rx, ry,
+      rotation: rotationDeg,
+      ...(isFull ? {} : { startAngle, endAngle }),
+    },
+  } as unknown as CADElement;
+}
+
+export const ellipseTool: ToolExtensionV2 = {
+  manifest: {
+    id: 'ellipse',
+    label: 'Ellipse',
+    icon: '\u2b2d',
+    ribbonTab: 'canvas',
+    tags: ['basic'],
+    description: 'Ellipse zeichnen: Zentrum klicken, RadiusX, RadiusY (Bogen via Optionen)',
+  },
+  optionsSchema: [
+    { key: 'strokeColor', label: 'Farbe', type: 'color' },
+    { key: 'startAngle', label: 'Bogen-Start (°)', type: 'number', min: 0, max: 360 },
+    { key: 'endAngle', label: 'Bogen-Ende (°)', type: 'number', min: 0, max: 360 },
+  ],
+  handlers: {
+    down(e, ctx) {
+      const c = ctx as FullToolContext;
+      if (ellipsePhase === 0) {
+        ellipseCenter = e.world;
+        ellipsePhase = 1;
+        ctx.setStatus('Ellipse: Zentrum gesetzt – RadiusX klicken (Richtung = Rotation)');
+      } else if (ellipsePhase === 1) {
+        if (!ellipseCenter) { ellipsePhase = 0; return; }
+        const dx = e.world.x - ellipseCenter.x;
+        const dy = e.world.y - ellipseCenter.y;
+        ellipseRadiusX = Math.hypot(dx, dy);
+        ellipseRotationDeg = ((Math.atan2(dy, dx) * 180) / Math.PI + 360) % 360;
+        ellipsePhase = 2;
+        ctx.setStatus('Ellipse: RadiusX gesetzt – RadiusY klicken');
+      } else {
+        // Phase 2: Commit
+        if (!ellipseCenter || !c.doc) { ellipsePhase = 0; ellipseCenter = null; return; }
+        const dx = e.world.x - ellipseCenter.x;
+        const dy = e.world.y - ellipseCenter.y;
+        const ry = Math.hypot(dx, dy);
+        // Rotation: Winkel des Klick2-Vektors gegenüber der +x-Achse
+        const startAngle = (ctx.options.startAngle as number | undefined) ?? 0;
+        const endAngle = (ctx.options.endAngle as number | undefined) ?? 360;
+        const el = buildEllipse(
+          ellipseCenter.x, ellipseCenter.y,
+          ellipseRadiusX, ry,
+          ellipseRotationDeg,
+          c, startAngle, endAngle,
+        );
+        c.doc.transact(() => c.doc!.addElement(el));
+        ellipsePhase = 0;
+        ellipseCenter = null;
+        ctx.setPreview?.(null);
+        ctx.setStatus(`Ellipse erstellt (${el.id})`);
+      }
+    },
+    move(e, ctx) {
+      const c = ctx as FullToolContext;
+      if (ellipsePhase === 1 && ellipseCenter) {
+        // RadiusX-Linie als Preview
+        const r = Math.hypot(e.world.x - ellipseCenter.x, e.world.y - ellipseCenter.y);
+        const rotDeg = ((Math.atan2(e.world.y - ellipseCenter.y, e.world.x - ellipseCenter.x) * 180) / Math.PI + 360) % 360;
+        const startAngle = (ctx.options.startAngle as number | undefined) ?? 0;
+        const endAngle = (ctx.options.endAngle as number | undefined) ?? 360;
+        ctx.setPreview?.(buildEllipse(ellipseCenter.x, ellipseCenter.y, r, r, rotDeg, c, startAngle, endAngle));
+      } else if (ellipsePhase === 2 && ellipseCenter) {
+        const ry = Math.hypot(e.world.x - ellipseCenter.x, e.world.y - ellipseCenter.y);
+        const rotDeg = ellipseRotationDeg;
+        const startAngle = (ctx.options.startAngle as number | undefined) ?? 0;
+        const endAngle = (ctx.options.endAngle as number | undefined) ?? 360;
+        ctx.setPreview?.(buildEllipse(ellipseCenter.x, ellipseCenter.y, ellipseRadiusX, ry, rotDeg, c, startAngle, endAngle));
+      }
+    },
+    cancel(ctx) {
+      ellipsePhase = 0;
+      ellipseCenter = null;
+      ctx.setPreview?.(null);
+      ctx.setStatus('Ellipse abgebrochen');
+    },
+  },
+};
+
 export const coreDrawingPlugin: PluginV2 = {
   manifest: {
     id: 'core-drawing',
@@ -424,5 +568,5 @@ export const coreDrawingPlugin: PluginV2 = {
     category: 'tools',
     enabledByDefault: true,
   },
-  tools: [lineTool, rectTool, circleTool, arcTool, polylineTool, polygonTool, revcloudTool],
+  tools: [lineTool, rectTool, circleTool, arcTool, polylineTool, polygonTool, revcloudTool, ellipseTool],
 };
diff --git a/frontend/tests/ellipseTool.test.ts b/frontend/tests/ellipseTool.test.ts
new file mode 100644
index 0000000..3c2994b
--- /dev/null
+++ b/frontend/tests/ellipseTool.test.ts
@@ -0,0 +1,137 @@
+/**
+ * Task D1 – Ellipse+Bogen-Tool (core-drawing).
+ *
+ * 3-Klick-Interaktion: Klick1=Zentrum, Klick2=RadiusX (Richtung
+ * definiert die Rotation), Klick3=RadiusY. Commit als geschlossene
+ * Polyline (64 Punkte, F5-Parser-Konvention) mit cx/cy/rx/ry/rotation
+ * Metadaten. Ellipsenbogen via startAngle/endAngle-Options → offene
+ * Polyline mit proportionalen Punkten.
+ */
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { ellipseTool } from '../src/plugins/builtin/core-drawing';
+import { CADDocument } from '../src/kernel/document/CADDocument';
+import { createInMemoryDoc } from './helpers/inMemoryDoc';
+import type { CADElement, Pt } from '../src/types/cad.types';
+
+function mkCtx(options: Record<string, unknown> = {}) {
+  const { ydoc } = createInMemoryDoc();
+  const doc = new CADDocument(ydoc);
+  const previews: (CADElement | null)[] = [];
+  const statuses: string[] = [];
+  const ctx: any = {
+    doc,
+    options,
+    setStatus: (m: string) => statuses.push(m),
+    setPreview: (el: CADElement | null) => previews.push(el),
+  };
+  return { ctx, doc, previews, statuses };
+}
+
+function pe(x: number, y: number): { world: Pt } {
+  return { world: { x, y } } as never;
+}
+
+beforeEach(() => {
+  ellipseTool.handlers.cancel?.({ setStatus: () => {}, setPreview: () => {} } as never);
+});
+
+describe('D1: ellipseTool', () => {
+  it('3 Klicks: Zentrum→RadiusX→RadiusY erzeugt geschlossene Ellipse (64 Punkte)', () => {
+    const { ctx, doc } = mkCtx();
+    ellipseTool.handlers.down!(pe(0, 0), ctx);
+    ellipseTool.handlers.down!(pe(100, 0), ctx);   // RadiusX=100, Rotation=0
+    ellipseTool.handlers.down!(pe(0, 50), ctx);     // RadiusY=50
+    const els = doc.getAllElements();
+    expect(els).toHaveLength(1);
+    const el = els[0];
+    expect(el.type).toBe('polygon');
+    const pts = el.properties.points as Pt[];
+    expect(pts.length).toBe(64);
+    // BBox: rx=100, ry=50
+    const xs = pts.map((p) => p.x);
+    const ys = pts.map((p) => p.y);
+    expect(Math.max(...xs)).toBeCloseTo(100, 0);
+    expect(Math.min(...xs)).toBeCloseTo(-100, 0);
+    expect(Math.max(...ys)).toBeCloseTo(50, 0);
+    expect(Math.min(...ys)).toBeCloseTo(-50, 0);
+    // Metadaten
+    expect(el.properties.cx).toBe(0);
+    expect(el.properties.cy).toBe(0);
+    expect(el.properties.rx).toBe(100);
+    expect(el.properties.ry).toBe(50);
+    expect(el.properties.rotation).toBe(0);
+  });
+
+  it('Zugrichtung definiert Rotation: Klick2 nach (0,100) → rotation=90°', () => {
+    const { ctx, doc } = mkCtx();
+    ellipseTool.handlers.down!(pe(0, 0), ctx);
+    ellipseTool.handlers.down!(pe(0, 100), ctx);   // RadiusX zeigt nach unten
+    ellipseTool.handlers.down!(pe(50, 0), ctx);     // RadiusY
+    const el = doc.getAllElements()[0];
+    expect(el.properties.rotation).toBeCloseTo(90, 1);
+    // Rotierte Ellipse: Hauptachse vertikal → maxY ≈ 100
+    const ys = (el.properties.points as Pt[]).map((p) => p.y);
+    expect(Math.max(...ys)).toBeCloseTo(100, 0);
+  });
+
+  it('Preview bei move nach Phase 2 zeigt Ellipse', () => {
+    const { ctx, previews } = mkCtx();
+    ellipseTool.handlers.down!(pe(0, 0), ctx);
+    ellipseTool.handlers.move!(pe(80, 0), ctx);     // RadiusX-Linie
+    ellipseTool.handlers.down!(pe(80, 0), ctx);     // RadiusX fixiert
+    ellipseTool.handlers.move!(pe(0, 40), ctx);    // Ellipsen-Preview mit live ry
+    expect(previews.length).toBeGreaterThanOrEqual(2);
+    const last = previews[previews.length - 1];
+    expect(last).not.toBeNull();
+    expect(last!.type).toBe('polygon');
+  });
+
+  it('Status führt durch die Phasen', () => {
+    const { ctx, statuses } = mkCtx();
+    ellipseTool.handlers.down!(pe(0, 0), ctx);
+    expect(statuses[0]).toContain('Zentrum');
+    ellipseTool.handlers.down!(pe(100, 0), ctx);
+    expect(statuses[1]).toContain('Radius');
+  });
+
+  it('cancel resettet die Messung', () => {
+    const { ctx, doc } = mkCtx();
+    ellipseTool.handlers.down!(pe(0, 0), ctx);
+    ellipseTool.handlers.down!(pe(100, 0), ctx);
+    ellipseTool.handlers.cancel?.(ctx);
+    // Nach cancel startet frisch: nächster Klick = Zentrum (kein Commit)
+    ellipseTool.handlers.down!(pe(0, 0), ctx);
+    expect(doc.getAllElements()).toHaveLength(0);
+  });
+});
+
+describe('D1: Ellipsenbogen (startAngle/endAngle)', () => {
+  it('Options startAngle=0/endAngle=180 erzeugen OFFENE Polyline (32 Punkte)', () => {
+    const { ctx, doc } = mkCtx({ startAngle: 0, endAngle: 180 });
+    ellipseTool.handlers.down!(pe(0, 0), ctx);
+    ellipseTool.handlers.down!(pe(100, 0), ctx);
+    ellipseTool.handlers.down!(pe(0, 50), ctx);
+    const el = doc.getAllElements()[0];
+    expect(el.type).toBe('polyline'); // offen
+    const pts = el.properties.points as Pt[];
+    expect(pts.length).toBe(32); // halbe Ellipse = 64/2
+  });
+
+  it('Winkel-Metadaten in properties', () => {
+    const { ctx, doc } = mkCtx({ startAngle: 45, endAngle: 225 });
+    ellipseTool.handlers.down!(pe(0, 0), ctx);
+    ellipseTool.handlers.down!(pe(100, 0), ctx);
+    ellipseTool.handlers.down!(pe(0, 50), ctx);
+    const el = doc.getAllElements()[0];
+    expect(el.properties.startAngle).toBe(45);
+    expect(el.properties.endAngle).toBe(225);
+  });
+});
+
+describe('D1: Manifest', () => {
+  it('id=ellipse, ribbonTab=canvas, tags basic, Version in tools-Array', () => {
+    expect(ellipseTool.manifest.id).toBe('ellipse');
+    expect(ellipseTool.manifest.ribbonTab).toBe('canvas');
+    expect((ellipseTool.manifest.tags ?? [])).toContain('basic');
+  });
+});