diff --git a/frontend/src/plugins/builtin/core-modify/index.ts b/frontend/src/plugins/builtin/core-modify/index.ts
index 7e98762..dfedb8e 100644
--- a/frontend/src/plugins/builtin/core-modify/index.ts
+++ b/frontend/src/plugins/builtin/core-modify/index.ts
@@ -82,6 +82,109 @@ function hitHandle(
   return null;
 }
 
+// ─────────────────────────────────────────────────────────────
+// Task D9: GripEditing — Vertex-/Center-Grips (reine Funktion).
+// ─────────────────────────────────────────────────────────────
+
+export interface GripPoint {
+  kind: 'vertex' | 'center' | 'corner';
+  point: Pt;
+  index: number;
+}
+
+/**
+ * Element-spezifische Griff-Punkte (Task D9):
+ * line = beide Endpunkte, polyline/polygon = alle Vertices,
+ * circle/arc = Zentrum, rect/default = 4 BBox-Ecken (C3fin-Skalierung).
+ */
+export function getGripPoints(el: CADElement): GripPoint[] {
+  const props = el.properties as Record<string, unknown>;
+  const type = String(el.type);
+  if (
+    type === 'line' &&
+    props.x1 !== undefined && props.y1 !== undefined &&
+    props.x2 !== undefined && props.y2 !== undefined
+  ) {
+    return [
+      { kind: 'vertex', point: { x: props.x1 as number, y: props.y1 as number }, index: 0 },
+      { kind: 'vertex', point: { x: props.x2 as number, y: props.y2 as number }, index: 1 },
+    ];
+  }
+  if (type === 'polyline' || type === 'polygon') {
+    const pts = (props.points as Pt[] | undefined) ?? [];
+    return pts.map((p, i) => ({ kind: 'vertex' as const, point: { x: p.x, y: p.y }, index: i }));
+  }
+  if (type === 'circle' || type === 'arc') {
+    return [{ kind: 'center', point: { x: el.x, y: el.y }, index: 0 }];
+  }
+  // rect und alle anderen: BBox-Ecken (Corner-Drag/Skalierung, C3fin)
+  const minX = el.x - el.width / 2;
+  const minY = el.y - el.height / 2;
+  const maxX = el.x + el.width / 2;
+  const maxY = el.y + el.height / 2;
+  return [
+    { kind: 'corner', point: { x: minX, y: minY }, index: 0 },
+    { kind: 'corner', point: { x: maxX, y: minY }, index: 1 },
+    { kind: 'corner', point: { x: maxX, y: maxY }, index: 2 },
+    { kind: 'corner', point: { x: minX, y: maxY }, index: 3 },
+  ];
+}
+
+/**
+ * Wendet eine Vertex-/Center-Drag-Position an (Task D9) und liefert
+ * das aktualisierte Element (reine Funktion — für Preview UND Commit).
+ */
+function applyVertexDrag(
+  el: CADElement,
+  drag: { el: CADElement; gripKind: 'vertex' | 'center'; index: number },
+  wx: number,
+  wy: number,
+): CADElement {
+  const props = { ...(el.properties as Record<string, unknown>) };
+  const type = String(el.type);
+  if (drag.gripKind === 'center') {
+    return { ...el, x: wx, y: wy, properties: props as CADElement['properties'] } as CADElement;
+  }
+  if (type === 'line') {
+    if (drag.index === 0) { props.x1 = wx; props.y1 = wy; }
+    else { props.x2 = wx; props.y2 = wy; }
+    // BBox aktualisieren
+    const x1 = props.x1 as number, y1 = props.y1 as number, x2 = props.x2 as number, y2 = props.y2 as number;
+    return {
+      ...el,
+      x: (x1 + x2) / 2,
+      y: (y1 + y2) / 2,
+      width: Math.abs(x2 - x1),
+      height: Math.abs(y2 - y1),
+      properties: props as CADElement['properties'],
+    } as CADElement;
+  }
+  if (type === 'polyline' || type === 'polygon') {
+    const pts = [...((props.points as Pt[] | undefined) ?? [])];
+    if (drag.index < pts.length) pts[drag.index] = { x: wx, y: wy };
+    props.points = pts;
+    const xs = pts.map((p) => p.x), ys = pts.map((p) => p.y);
+    const minX = Math.min(...xs), minY = Math.min(...ys);
+    const maxX = Math.max(...xs), maxY = Math.max(...ys);
+    return {
+      ...el,
+      x: minX + (maxX - minX) / 2,
+      y: minY + (maxY - minY) / 2,
+      width: maxX - minX,
+      height: maxY - minY,
+      properties: props as CADElement['properties'],
+    } as CADElement;
+  }
+  return el;
+}
+
+/** Vertex-/Center-Drag-Sitzung (Task D9). */
+let vertexDrag: {
+  el: CADElement;
+  gripKind: 'vertex' | 'center';
+  index: number;
+} | null = null;
+
 export const selectTool: ToolExtensionV2 = {
   manifest: {
     id: 'select',
@@ -101,6 +204,28 @@ export const selectTool: ToolExtensionV2 = {
       const subtractive = e.ctrl;
       const hit = bridge.hitTest(e.world.x, e.world.y, 5);
 
+      // ── Task D9: Vertex-/Center-Grip-Prüfung VOR BBox-Corners ──
+      // (spezifischere Grips gewinnen gegenüber Corner-Skalierung)
+      if (!additive && !subtractive && c.doc) {
+        const GRIP_TOL = 8;
+        for (const id of bridge.getIds()) {
+          const el = c.doc.getElement(id);
+          if (!el) continue;
+          for (const g of getGripPoints(el)) {
+            if (g.kind === 'corner') continue; // Corner unten (C3fin)
+            if (
+              Math.abs(e.world.x - g.point.x) <= GRIP_TOL &&
+              Math.abs(e.world.y - g.point.y) <= GRIP_TOL
+            ) {
+              vertexDrag = { el, gripKind: g.kind, index: g.index };
+              const what = g.kind === 'center' ? 'Zentrum' : `Punkt ${g.index + 1}`;
+              ctx.setStatus(`${what} gegriffen — ziehen zum Verschieben`);
+              return;
+            }
+          }
+        }
+      }
+
       // ── Handle-Drag-Start (Task C3fin interaktiv) ──
       // Wenn bereits Elemente selektiert sind und der Klick auf eine Ecke
       // eines davon trifft → Handle-Drag starten statt neu zu wählen.
@@ -133,6 +258,15 @@ export const selectTool: ToolExtensionV2 = {
     },
 
     move(e, ctx) {
+      // ── Task D9: Vertex-Drag-Preview (nur der Punkt aktualisiert) ──
+      if (vertexDrag) {
+        const c = ctx as FullToolContext;
+        const el = c.doc?.getElement(vertexDrag.el.id);
+        if (!el) return;
+        const updated = applyVertexDrag(el, vertexDrag, e.world.x, e.world.y);
+        c.setPreview?.(updated);
+        return;
+      }
       // Live-Skalierung während Handle-Drag:
       if (!handleDrag) return;
       const c = ctx as FullToolContext;
@@ -174,6 +308,26 @@ export const selectTool: ToolExtensionV2 = {
     },
 
     up(e, ctx) {
+      // ── Task D9: Vertex-Commit (nur der Punkt, 1 Undo-Schritt) ──
+      if (vertexDrag) {
+        const c = ctx as FullToolContext;
+        const el = c.doc?.getElement(vertexDrag.el.id);
+        if (el && c.doc) {
+          const updated = applyVertexDrag(el, vertexDrag, e.world.x, e.world.y);
+          c.doc.transact(() => {
+            c.doc!.updateElement(el.id, {
+              x: updated.x,
+              y: updated.y,
+              properties: updated.properties as CADElement['properties'],
+            });
+          });
+          const what = vertexDrag.gripKind === 'center' ? 'Zentrum' : `Punkt ${vertexDrag.index + 1}`;
+          ctx.setStatus(`${what} verschoben`);
+        }
+        vertexDrag = null;
+        ctx.setPreview?.(null);
+        return;
+      }
       if (!handleDrag) return;
       const c = ctx as FullToolContext;
       if (!c.doc) { handleDrag = null; return; }
@@ -224,6 +378,7 @@ export const selectTool: ToolExtensionV2 = {
 
     cancel(ctx) {
       handleDrag = null;
+      vertexDrag = null;
       ctx.setPreview?.(null);
     },
   },
diff --git a/frontend/tests/gripEditing.test.ts b/frontend/tests/gripEditing.test.ts
new file mode 100644
index 0000000..9692ccd
--- /dev/null
+++ b/frontend/tests/gripEditing.test.ts
@@ -0,0 +1,244 @@
+/**
+ * Task D9 – GripEditing: Vertex-/Center-Grips im select-Tool.
+ *
+ * getGripPoints: element-spezifische Griff-Punkte (line=Endpunkte,
+ * polyline=Vertices, circle/arc=Zentrum, rect=BBox-Ecken).
+ * Drag eines Vertex-Grips verschiebt NUR diesen Punkt in einer
+ * Transaktion (undo-fähig); BBox-Skalierung (C3fin) bleibt parallel
+ * für Elemente ohne Vertex-Grips (rect u.a.).
+ */
+import { describe, it, expect, beforeEach } from 'vitest';
+import { selectTool, getGripPoints } from '../src/plugins/builtin/core-modify';
+import { CADDocument } from '../src/kernel/document/CADDocument';
+import { createInMemoryDoc } from './helpers/inMemoryDoc';
+import type { CADElement, Pt } from '../src/types/cad.types';
+
+function mkCtx() {
+  const { ydoc } = createInMemoryDoc();
+  const doc = new CADDocument(ydoc);
+  const selectedIds = new Set<string>();
+  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),
+    selection: {
+      getIds: () => Array.from(selectedIds),
+      setIds: (ids: string[]) => {
+        selectedIds.clear();
+        for (const id of ids) selectedIds.add(id);
+      },
+      hitTest: (x: number, y: number, tol: number) => {
+        // Einfacher Hit-Test: trifft wenn ein Element-BBox den Punkt enthaelt
+        for (const el of doc.getAllElements()) {
+          const p = el.properties as Record<string, unknown>;
+          if (p.x1 !== undefined) {
+            const minX = Math.min(p.x1 as number, p.x2 as number);
+            const maxX = Math.max(p.x1 as number, p.x2 as number);
+            const minY = Math.min(p.y1 as number, p.y2 as number);
+            const maxY = Math.max(p.y1 as number, p.y2 as number);
+            if (x >= minX - tol && x <= maxX + tol && y >= minY - tol && y <= maxY + tol) return el;
+          }
+          if (x >= el.x - el.width / 2 - tol && x <= el.x + el.width / 2 + tol &&
+              y >= el.y - el.height / 2 - tol && y <= el.y + el.height / 2 + tol) return el;
+        }
+        return null;
+      },
+    },
+  };
+  return { ctx, doc, selectedIds, previews, statuses };
+}
+
+function pe(x: number, y: number, mods: { shift?: boolean; ctrl?: boolean } = {}): { world: Pt; shift: boolean; ctrl: boolean } {
+  return { world: { x, y }, shift: mods.shift ?? false, ctrl: mods.ctrl ?? false } as never;
+}
+
+beforeEach(() => {
+  selectTool.handlers.cancel?.({ setStatus: () => {}, setPreview: () => {} } as never);
+});
+
+// ─── getGripPoints (reine Funktion) ────────────────────────
+
+describe('D9: getGripPoints', () => {
+  it('line: beide Endpunkte als Grips', () => {
+    const el = {
+      id: 'l1', type: 'line', layerId: 'l', x: 50, y: 50, width: 100, height: 0,
+      properties: { x1: 0, y1: 50, x2: 100, y2: 50 },
+    } as unknown as CADElement;
+    const grips = getGripPoints(el);
+    expect(grips.map((g) => g.kind)).toEqual(['vertex', 'vertex']);
+    expect(grips[0].point).toEqual({ x: 0, y: 50 });
+    expect(grips[1].point).toEqual({ x: 100, y: 50 });
+  });
+
+  it('polyline: alle Vertices als Grips', () => {
+    const el = {
+      id: 'p1', type: 'polyline', layerId: 'l', x: 50, y: 0, width: 100, height: 100,
+      properties: { points: [{ x: 0, y: 0 }, { x: 100, y: 0 }, { x: 100, y: 100 }] },
+    } as unknown as CADElement;
+    const grips = getGripPoints(el);
+    expect(grips.length).toBe(3);
+    expect(grips.every((g) => g.kind === 'vertex')).toBe(true);
+    expect(grips[2].point).toEqual({ x: 100, y: 100 });
+  });
+
+  it('circle: Zentrum als Center-Grip', () => {
+    const el = {
+      id: 'c1', type: 'circle', layerId: 'l', x: 30, y: 40, width: 20, height: 20,
+      properties: { radius: 10 },
+    } as unknown as CADElement;
+    const grips = getGripPoints(el);
+    expect(grips).toHaveLength(1);
+    expect(grips[0].kind).toBe('center');
+    expect(grips[0].point).toEqual({ x: 30, y: 40 });
+  });
+
+  it('rect: BBox-Ecken als Corner-Grips (C3fin bleibt)', () => {
+    const el = {
+      id: 'r1', type: 'rect', layerId: 'l', x: 50, y: 25, width: 100, height: 50,
+      properties: {},
+    } as unknown as CADElement;
+    const grips = getGripPoints(el);
+    expect(grips.length).toBe(4);
+    expect(grips.every((g) => g.kind === 'corner')).toBe(true);
+    expect(grips[0].point).toEqual({ x: 0, y: 0 });
+    expect(grips[2].point).toEqual({ x: 100, y: 50 });
+  });
+
+  it('Grips tragen index fuer Drag-Zuordnung', () => {
+    const el = {
+      id: 'p1', type: 'polyline', layerId: 'l', x: 0, y: 0, width: 10, height: 10,
+      properties: { points: [{ x: 0, y: 0 }, { x: 10, y: 10 }] },
+    } as unknown as CADElement;
+    const grips = getGripPoints(el);
+    expect(grips[0].index).toBe(0);
+    expect(grips[1].index).toBe(1);
+  });
+});
+
+// ─── Drag-Interaktion: Vertex-Zug (undo-faehig) ─────────────
+
+describe('D9: Vertex-Drag im selectTool', () => {
+  it('Linien-Endpunkt ziehen verschiebt NUR diesen Punkt (1 Undo)', () => {
+    const { ctx, doc, selectedIds } = mkCtx();
+    const line = {
+      id: 'l1', 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);
+    selectedIds.add('l1');
+
+    // Klick auf Endpunkt (100,0) startet Vertex-Drag
+    selectTool.handlers.down!(pe(100, 0), ctx);
+    selectTool.handlers.up!(pe(120, 30), ctx);
+
+    const updated = doc.getElement('l1')!;
+    expect(updated.properties.x2).toBe(120);
+    expect(updated.properties.y2).toBe(30);
+    // Anderer Endpunkt unveraendert
+    expect(updated.properties.x1).toBe(0);
+    expect(updated.properties.y1).toBe(0);
+    // Undo stellt her
+    doc.undo();
+    const restored = doc.getElement('l1')!;
+    expect(restored.properties.x2).toBe(100);
+    expect(restored.properties.y2).toBe(0);
+  });
+
+  it('Polyline-Vertex ziehen aktualisiert nur diesen Vertex', () => {
+    const { ctx, doc, selectedIds } = mkCtx();
+    const poly = {
+      id: 'p1', type: 'polyline', layerId: 'l', x: 50, y: 50, width: 100, height: 100,
+      properties: { points: [{ x: 0, y: 0 }, { x: 100, y: 0 }, { x: 100, y: 100 }] },
+    } as unknown as CADElement;
+    doc.addElement(poly);
+    selectedIds.add('p1');
+
+    // Mittleren Vertex (100,0) greifen und auf (100,50) ziehen
+    selectTool.handlers.down!(pe(100, 0), ctx);
+    selectTool.handlers.up!(pe(100, 50), ctx);
+
+    const pts = doc.getElement('p1')!.properties.points as Pt[];
+    expect(pts[1]).toEqual({ x: 100, y: 50 });
+    expect(pts[0]).toEqual({ x: 0, y: 0 });
+    expect(pts[2]).toEqual({ x: 100, y: 100 });
+  });
+
+  it('Kreis-Zentrum ziehen verschiebt x/y (Radius bleibt)', () => {
+    const { ctx, doc, selectedIds } = mkCtx();
+    const circle = {
+      id: 'c1', type: 'circle', layerId: 'l', x: 30, y: 40, width: 20, height: 20,
+      properties: { radius: 10 },
+    } as unknown as CADElement;
+    doc.addElement(circle);
+    selectedIds.add('c1');
+
+    selectTool.handlers.down!(pe(30, 40), ctx);
+    selectTool.handlers.up!(pe(60, 80), ctx);
+
+    const updated = doc.getElement('c1')!;
+    expect(updated.x).toBe(60);
+    expect(updated.y).toBe(80);
+    expect(updated.properties.radius).toBe(10);
+  });
+
+  it('BBox-Corner-Drag bei rect funktioniert weiterhin (Skalierung)', () => {
+    const { ctx, doc, selectedIds } = mkCtx();
+    const rect = {
+      id: 'r1', type: 'rect', layerId: 'l', x: 50, y: 25, width: 100, height: 50,
+      properties: {},
+    } as unknown as CADElement;
+    doc.addElement(rect);
+    selectedIds.add('r1');
+
+    // Ecke unten-rechts (100,50) greifen und auf (150,75) ziehen
+    selectTool.handlers.down!(pe(100, 50), ctx);
+    selectTool.handlers.up!(pe(150, 75), ctx);
+
+    const updated = doc.getElement('r1')!;
+    expect(updated.width).toBeCloseTo(150, 0);
+    expect(updated.height).toBeCloseTo(75, 0);
+  });
+
+  it('Vertex-Grip gewinnt gegen BBox-Corner bei Ueberlappung (line-Endpunkt am BBox-Rand)', () => {
+    // line (0,0)-(100,0): Endpunkt (0,0) ist AUCH BBox-Ecke.
+    // Der Drag muss als Vertex (Punkt verschieben) wirken, nicht als Scale.
+    const { ctx, doc, selectedIds } = mkCtx();
+    const line = {
+      id: 'l1', 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);
+    selectedIds.add('l1');
+
+    selectTool.handlers.down!(pe(0, 0), ctx);
+    selectTool.handlers.up!(pe(-30, -20), ctx);
+
+    const updated = doc.getElement('l1')!;
+    // x1/y1 verschoben, x2 unveraendert → Vertex-Drag, kein Scale
+    expect(updated.properties.x1).toBe(-30);
+    expect(updated.properties.y1).toBe(-20);
+    expect(updated.properties.x2).toBe(100);
+  });
+
+  it('Preview bei Vertex-Drag zeigt aktualisiertes Element', () => {
+    const { ctx, doc, selectedIds, previews } = mkCtx();
+    const line = {
+      id: 'l1', 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);
+    selectedIds.add('l1');
+
+    selectTool.handlers.down!(pe(100, 0), ctx);
+    selectTool.handlers.move!(pe(90, 40), ctx);
+    expect(previews.length).toBeGreaterThanOrEqual(1);
+    const last = previews[previews.length - 1];
+    expect(last).not.toBeNull();
+    const lastProps = last!.properties as Record<string, unknown>;
+    expect(lastProps.x2).toBe(90);
+    expect(lastProps.y2).toBe(40);
+  });
+});