diff --git a/frontend/src/plugins/builtin/core-modify/index.ts b/frontend/src/plugins/builtin/core-modify/index.ts
index 19d5710..7e98762 100644
--- a/frontend/src/plugins/builtin/core-modify/index.ts
+++ b/frontend/src/plugins/builtin/core-modify/index.ts
@@ -572,6 +572,245 @@ export const joinTool: ToolExtensionV2 = makeJoinExplodeAlignTool('join');
 export const explodeTool: ToolExtensionV2 = makeJoinExplodeAlignTool('explode');
 export const alignTool: ToolExtensionV2 = makeJoinExplodeAlignTool('align');
 
+// ─────────────────────────────────────────────────────────────
+// Polyline-Editor (Task D-Finish): Vertices einer Polyline verschieben.
+// Klick 1: Polyline wählen. Klick 2+: Vertex wählen (Toleranz) und ziehen.
+// ESC beendet.
+// ─────────────────────────────────────────────────────────────
+let editPoly: CADElement | null = null;
+let editVertexIdx = -1;
+
+export const polylineEditTool: ToolExtensionV2 = {
+  manifest: {
+    id: 'polyline-edit',
+    label: 'Polyline-Editor',
+    icon: '\u2b1a',
+    ribbonTab: 'canvas',
+    tags: ['pro'],
+    description: 'Polyline wählen, dann Vertex ziehen',
+  },
+  optionsSchema: [],
+  handlers: {
+    down(e, ctx) {
+      const c = ctx as FullToolContext;
+      if (!c.doc || !c.selection) return;
+      if (!editPoly) {
+        const hit = c.selection.hitTest(e.world.x, e.world.y, 5);
+        if (!hit || hit.type !== 'polyline') {
+          ctx.setStatus('Polyline-Editor: erst eine Polyline anklicken');
+          return;
+        }
+        editPoly = hit;
+        ctx.setStatus('Polyline-Editor: Vertex ziehen, ESC beendet');
+        return;
+      }
+      // Vertex finden in der Nähe:
+      const props = editPoly.properties as Record<string, unknown>;
+      const pts = Array.isArray(props.points)
+        ? (props.points as unknown[]).map((p) => p as Pt)
+        : [];
+      for (let i = 0; i < pts.length; i++) {
+        if (Math.hypot(pts[i].x - e.world.x, pts[i].y - e.world.y) < 8) {
+          editVertexIdx = i;
+          ctx.setStatus(`Vertex ${i + 1} — ziehen`);
+          return;
+        }
+      }
+      ctx.setStatus('Kein Vertex in der Nähe');
+    },
+    move(e, ctx) {
+      if (!editPoly || editVertexIdx < 0) return;
+      const c = ctx as FullToolContext;
+      const props = editPoly.properties as Record<string, unknown>;
+      const pts = Array.isArray(props.points)
+        ? (props.points as unknown[]).map((p) => p as Pt)
+        : [];
+      pts[editVertexIdx] = e.world;
+      const preview: CADElement = {
+        ...editPoly,
+        properties: { ...props, points: pts },
+      };
+      c.setPreview?.(preview);
+    },
+    up(e, ctx) {
+      if (!editPoly || editVertexIdx < 0) return;
+      const c = ctx as FullToolContext;
+      if (!c.doc) { editVertexIdx = -1; return; }
+      const current = c.doc.getElement(editPoly.id);
+      if (!current) { editVertexIdx = -1; return; }
+      const props = current.properties as Record<string, unknown>;
+      const pts = Array.isArray(props.points)
+        ? (props.points as unknown[]).map((p) => ({ ...(p as Pt) }))
+        : [];
+      if (editVertexIdx < pts.length) {
+        pts[editVertexIdx] = e.world;
+        const xs = pts.map((p) => p.x);
+        const ys = pts.map((p) => p.y);
+        c.doc.transact(() => {
+          c.doc!.updateElement(editPoly!.id, {
+            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: { ...props, points: pts },
+          });
+        });
+        ctx.setStatus(`Vertex ${editVertexIdx + 1} verschoben`);
+      }
+      editVertexIdx = -1;
+    },
+    cancel(ctx) {
+      editPoly = null;
+      editVertexIdx = -1;
+      ctx.setStatus('Polyline-Editor beendet');
+    },
+  },
+};
+
+// ─────────────────────────────────────────────────────────────
+// Stretch (Task D-Finish): Endpunkte von Linien in einem Auswahlbereich
+// verschieben. Klick 1: Basis, Klick 2: Ziel (Delta auf alle selektierten
+// Endpunkte, die in der Nähe des Basispunkts liegen).
+// ─────────────────────────────────────────────────────────────
+let stretchBase: Pt | null = null;
+
+export const stretchTool: ToolExtensionV2 = {
+  manifest: {
+    id: 'stretch',
+    label: 'Stretch',
+    icon: '\u2197',
+    ribbonTab: 'canvas',
+    tags: ['pro'],
+    description: 'Linien auswählen, dann Basis→Ziel (Endpunkte in Basisnähe werden gestreckt)',
+  },
+  optionsSchema: [],
+  handlers: {
+    down(e, ctx) {
+      const c = ctx as FullToolContext;
+      if (!c.doc || !c.selection) return;
+      if (!stretchBase) {
+        if (c.selection.getIds().length === 0) {
+          const hit = c.selection.hitTest(e.world.x, e.world.y, 5);
+          if (!hit) {
+            ctx.setStatus('Stretch: zuerst Linien auswählen');
+            return;
+          }
+          c.selection.setIds([hit.id]);
+        }
+        stretchBase = e.world;
+        ctx.setStatus(`Stretch: Zielklick (${c.selection.getIds().length} Linien)`);
+        return;
+      }
+      // Commit: alle Endpunkte, die dem Basispunkt am nächsten sind, verschieben:
+      const dx = e.world.x - stretchBase.x;
+      const dy = e.world.y - stretchBase.y;
+      const ids = c.selection.getIds();
+      c.doc.transact(() => {
+        for (const id of ids) {
+          const el = c.doc!.getElement(id);
+          if (!el || el.type !== 'line') continue;
+          const props = el.properties as { x1?: number; y1?: number; x2?: number; y2?: number };
+          if (props.x1 === undefined || props.y1 === undefined || props.x2 === undefined || props.y2 === undefined) continue;
+          // Endpunkte die dem Basispunkt am nächsten sind verschieben:
+          const d1 = Math.hypot(props.x1! - stretchBase!.x, props.y1! - stretchBase!.y);
+          const d2 = Math.hypot(props.x2! - stretchBase!.x, props.y2! - stretchBase!.y);
+          if (d1 < d2) {
+            props.x1 = props.x1! + dx;
+            props.y1 = props.y1! + dy;
+          } else {
+            props.x2 = props.x2! + dx;
+            props.y2 = props.y2! + dy;
+          }
+          const nx1 = props.x1!;
+          const ny1 = props.y1!;
+          const nx2 = props.x2!;
+          const ny2 = props.y2!;
+          c.doc!.updateElement(id, {
+            x: (nx1 + nx2) / 2,
+            y: (ny1 + ny2) / 2,
+            width: Math.abs(nx2 - nx1),
+            height: Math.abs(ny2 - ny1),
+            properties: props,
+          });
+        }
+      });
+      ctx.setStatus(`Stretch: ${ids.length} Linie(n) gestreckt \u0394(${dx.toFixed(0)}, ${dy.toFixed(0)})`);
+      stretchBase = null;
+    },
+    cancel(ctx) {
+      stretchBase = null;
+      ctx.setStatus('Stretch abgebrochen');
+    },
+  },
+};
+
+// ─────────────────────────────────────────────────────────────
+// Break (Task D-Finish): Linie an einem Punkt in zwei Teile splitten.
+// Klick auf Linie → zwei neue Linien, Original wird entfernt.
+// ─────────────────────────────────────────────────────────────
+export const breakTool: ToolExtensionV2 = {
+  manifest: {
+    id: 'break',
+    label: 'Break',
+    icon: '\u2702',
+    ribbonTab: 'canvas',
+    tags: ['pro'],
+    description: 'Linie anklicken — wird am Klickpunkt geteilt',
+  },
+  optionsSchema: [],
+  handlers: {
+    down(e, ctx) {
+      const c = ctx as FullToolContext;
+      if (!c.doc || !c.selection) return;
+      const hit = c.selection.hitTest(e.world.x, e.world.y, 5);
+      if (!hit || hit.type !== 'line') {
+        ctx.setStatus('Break: Linie anklicken');
+        return;
+      }
+      const props = hit.properties as { x1?: number; y1?: number; x2?: number; y2?: number };
+      if (props.x1 === undefined || props.y1 === undefined || props.x2 === undefined || props.y2 === undefined) return;
+
+      // Klick auf die Linie projizieren (nächster Punkt auf der Linie):
+      const x1 = props.x1 as number;
+      const y1 = props.y1 as number;
+      const x2 = props.x2 as number;
+      const y2 = props.y2 as number;
+      const dx = x2 - x1;
+      const dy = y2 - y1;
+      const lenSq = dx * dx + dy * dy;
+      if (lenSq === 0) return;
+      const t = Math.max(0, Math.min(1, ((e.world.x - x1) * dx + (e.world.y - y1) * dy) / lenSq));
+      const breakX = x1 + t * dx;
+      const breakY = y1 + t * dy;
+
+      c.doc.transact(() => {
+        // Original entfernen:
+        c.doc!.deleteElements([hit.id]);
+        // Zwei neue Linien hinzufügen:
+        c.doc!.addElement({
+          ...hit,
+          id: uid('brk'),
+          x: (x1 + breakX) / 2,
+          y: (y1 + breakY) / 2,
+          width: Math.abs(breakX - x1),
+          height: Math.abs(breakY - y1),
+          properties: { ...props, x2: breakX, y2: breakY },
+        });
+        c.doc!.addElement({
+          ...hit,
+          id: uid('brk'),
+          x: (breakX + x2) / 2,
+          y: (breakY + y2) / 2,
+          width: Math.abs(x2 - breakX),
+          height: Math.abs(y2 - breakY),
+          properties: { ...props, x1: breakX, y1: breakY },
+        });
+      });
+      ctx.setStatus(`Break: Linie bei (${breakX.toFixed(0)}, ${breakY.toFixed(0)}) geteilt`);
+    },
+  },
+};
+
 // ─────────────────────────────────────────────────────────────
 // Array rect / polar (Task D-Extensions):
 // Vervielfältigt die aktuelle Selektion in einem Raster bzw. im Kreis.
@@ -1083,11 +1322,11 @@ export const coreModifyPlugin: PluginV2 = {
   manifest: {
     id: 'core-modify',
     name: 'Bearbeiten (Kern)',
-    version: '1.8.0',
+    version: '1.9.0',
     author: 'web-cad team',
-    description: 'Auswahl, Schraffur, Move/Copy/Rotate/Scale/Mirror/Delete/Offset/Trim/Extend/Fillet/Arrays/Chamfer/Lengthen/Join/Explode/Align (V2).',
+    description: 'Auswahl, Schraffur, Move/Copy/Rotate/Scale/Mirror/Delete/Offset/Trim/Extend/Fillet/Arrays/Chamfer/Lengthen/Join/Explode/Align/Polyline-Edit/Stretch/Break (V2).',
     category: 'tools',
     enabledByDefault: true,
   },
-  tools: [selectTool, hatchTool, moveTool, copyTool, rotateTool, scaleTool, mirrorTool, deleteTool, offsetTool, trimTool, extendTool, filletTool, arrayRectTool, arrayPolarTool, chamferTool, lengthenTool, joinTool, explodeTool, alignTool],
+  tools: [selectTool, hatchTool, moveTool, copyTool, rotateTool, scaleTool, mirrorTool, deleteTool, offsetTool, trimTool, extendTool, filletTool, arrayRectTool, arrayPolarTool, chamferTool, lengthenTool, joinTool, explodeTool, alignTool, polylineEditTool, stretchTool, breakTool],
 };