diff --git a/frontend/src/plugins/builtin/event-tools/index.ts b/frontend/src/plugins/builtin/event-tools/index.ts
index f2d9466..4f04d9d 100644
--- a/frontend/src/plugins/builtin/event-tools/index.ts
+++ b/frontend/src/plugins/builtin/event-tools/index.ts
@@ -511,6 +511,7 @@ function makeTrussElement(
   rotationDeg: number,
   layerId: string,
   trussWidth = 29,
+  chordCount = 2,
 ): CADElement {
   const rad = (rotationDeg * Math.PI) / 180;
   const w = Math.abs(length * Math.cos(rad)) + Math.abs(trussWidth * Math.sin(rad));
@@ -524,7 +525,7 @@ function makeTrussElement(
     width: Math.max(w, trussWidth),
     height: Math.max(h, trussWidth),
     properties: {
-      length, rotation: rotationDeg, trussWidth, truss: true,
+      length, rotation: rotationDeg, trussWidth, chordCount, truss: true,
       stroke: '#9aa0a6', strokeWidth: 2, fill: '#6b7280',
     },
   } as unknown as CADElement;
@@ -542,13 +543,9 @@ export const trussTool: ToolExtensionV2 = {
     description: 'Traverse platzieren: Drag = Richtung, dockt magnetisch an bestehenden Traversen an (CAD-7)',
   },
   optionsSchema: [
-    { key: 'length', label: 'Länge (cm)', type: 'select', options: [
-      { value: '50', label: '50 cm' },
-      { value: '100', label: '100 cm' },
-      { value: '200', label: '200 cm' },
-      { value: '300', label: '300 cm' },
-    ] },
+    { key: 'length', label: 'Länge (cm)', type: 'number', min: 10, max: 1000 },
     { key: 'trussWidth', label: 'Breite (cm)', type: 'number', min: 10, max: 60 },
+    { key: 'chordCount', label: 'Gurtrohre', type: 'number', min: 1, max: 4 },
   ],
   handlers: {
     down(e, ctx) {
@@ -558,22 +555,23 @@ export const trussTool: ToolExtensionV2 = {
     move(e, ctx) {
       const c = ctx as FullToolContext;
       if (!trussDragStart) return;
-      const length = Number((c.options.length as string | undefined) ?? 200) || 200;
+      const length = Number((c.options.length as number | string | undefined) ?? 200) || 200;
       const trussWidth = (c.options.trussWidth as number | undefined) ?? 29;
+      const chordCount = Math.max(1, Math.min(4, (c.options.chordCount as number | undefined) ?? 2));
       // Magnet-Vorschau: dockt der Cursor an ein Traversen-/Ecken-Ende?
       const existing = c.doc ? (c.doc.getAllElements() as CADElement[]).filter(
         (el) => String(el.type) === 'truss' || String(el.type) === 'boxcorner',
       ) : [];
       const dock = snapTrussToDock(existing, trussDragStart, length, DOCK_TOLERANCE);
       if (dock) {
-        ctx.setPreview?.(makeTrussElement(dock.center, length, dock.rotationDeg, 'layer-0', trussWidth));
+        ctx.setPreview?.(makeTrussElement(dock.center, length, dock.rotationDeg, 'layer-0', trussWidth, chordCount));
         return;
       }
       // Frei: Richtung aus Drag
       const ang = (Math.atan2(e.world.y - trussDragStart.y, e.world.x - trussDragStart.x) * 180) / Math.PI;
       const cx = (trussDragStart.x + e.world.x) / 2;
       const cy = (trussDragStart.y + e.world.y) / 2;
-      ctx.setPreview?.(makeTrussElement({ x: cx, y: cy }, length, ang, 'layer-0'));
+      ctx.setPreview?.(makeTrussElement({ x: cx, y: cy }, length, ang, 'layer-0', trussWidth, chordCount));
     },
     up(e, ctx) {
       const c = ctx as FullToolContext;
@@ -583,6 +581,7 @@ export const trussTool: ToolExtensionV2 = {
       if (!start || !c.doc) return;
       const length = Number((c.options.length as string | undefined) ?? 200) || 200;
       const trussWidth = (c.options.trussWidth as number | undefined) ?? 29;
+      const chordCount = Math.max(1, Math.min(4, (c.options.chordCount as number | undefined) ?? 2));
       const layerId = (c.options.layerId as string | undefined) ?? 'layer-0';
       // MAGNETISCH: Dock-Pruefung am Drag-Startpunkt (Traversen UND Ecken)
       const existing = (c.doc.getAllElements() as CADElement[]).filter(
@@ -591,13 +590,13 @@ export const trussTool: ToolExtensionV2 = {
       const dock = snapTrussToDock(existing, start, length, DOCK_TOLERANCE);
       let el: CADElement;
       if (dock) {
-        el = makeTrussElement(dock.center, length, dock.rotationDeg, layerId, trussWidth);
+        el = makeTrussElement(dock.center, length, dock.rotationDeg, layerId, trussWidth, chordCount);
         ctx.setStatus(`Traverse angedockt an ${dock.dockedTo} (${length}cm, Breite ${trussWidth}cm)`);
       } else {
         const ang = (Math.atan2(e.world.y - start.y, e.world.x - start.x) * 180) / Math.PI;
         const cx = (start.x + e.world.x) / 2;
         const cy = (start.y + e.world.y) / 2;
-        el = makeTrussElement({ x: cx, y: cy }, length, ang, layerId, trussWidth);
+        el = makeTrussElement({ x: cx, y: cy }, length, ang, layerId, trussWidth, chordCount);
         ctx.setStatus(`Traverse platziert (${length}cm, Breite ${trussWidth}cm)`);
       }
       c.doc.transact(() => { c.doc!.addElement(el); });
@@ -621,8 +620,9 @@ export const trussTool: ToolExtensionV2 = {
 export function boxcornerEndpoints(el: CADElement): [Pt, Pt] {
   const armLength = (el.properties.armLength as number | undefined) ?? 50;
   const rotDeg = (el.properties.rotation as number | undefined) ?? 0;
+  const angle = (el.properties.angle as number | undefined) ?? 90;
   const rot = (rotDeg * Math.PI) / 180;
-  const rot2 = ((rotDeg + 90) * Math.PI) / 180;
+  const rot2 = ((rotDeg + angle) * Math.PI) / 180;
   return [
     { x: el.x + Math.cos(rot) * armLength, y: el.y + Math.sin(rot) * armLength },
     { x: el.x + Math.cos(rot2) * armLength, y: el.y + Math.sin(rot2) * armLength },
@@ -674,6 +674,7 @@ function makeBoxcornerElement(
   vertex: Pt,
   armLength: number,
   rotationDeg: number,
+  angleDeg: number,
   trussWidth: number,
   layerId: string,
 ): CADElement {
@@ -686,7 +687,7 @@ function makeBoxcornerElement(
     width: armLength + trussWidth,
     height: armLength + trussWidth,
     properties: {
-      armLength, trussWidth, rotation: rotationDeg, boxcorner: true,
+      armLength, trussWidth, rotation: rotationDeg, angle: angleDeg, boxcorner: true,
       stroke: '#9aa0a6', strokeWidth: 2, fill: '#6b7280',
     },
   } as unknown as CADElement;
@@ -705,6 +706,7 @@ export const boxCornerTool: ToolExtensionV2 = {
   },
   optionsSchema: [
     { key: 'armLength', label: 'Armlänge (cm)', type: 'number', min: 20, max: 150 },
+    { key: 'angle', label: 'Winkel (°)', type: 'number', min: 15, max: 165 },
     { key: 'trussWidth', label: 'Breite (cm)', type: 'number', min: 10, max: 60 },
   ],
   handlers: {
@@ -716,17 +718,18 @@ export const boxCornerTool: ToolExtensionV2 = {
       const c = ctx as FullToolContext;
       if (!cornerDragStart) return;
       const armLength = (c.options.armLength as number | undefined) ?? 50;
+      const cornerAngle = (c.options.angle as number | undefined) ?? 90;
       const trussWidth = (c.options.trussWidth as number | undefined) ?? 29;
       const existing = c.doc ? (c.doc.getAllElements() as CADElement[]).filter(
         (el) => String(el.type) === 'truss' || String(el.type) === 'boxcorner',
       ) : [];
       const dock = cornerDockToDock(existing, cornerDragStart, DOCK_TOLERANCE);
       if (dock) {
-        ctx.setPreview?.(makeBoxcornerElement(dock.vertex, armLength, dock.rotationDeg, trussWidth, 'layer-0'));
+        ctx.setPreview?.(makeBoxcornerElement(dock.vertex, armLength, dock.rotationDeg, cornerAngle, trussWidth, 'layer-0'));
         return;
       }
       const ang = (Math.atan2(e.world.y - cornerDragStart.y, e.world.x - cornerDragStart.x) * 180) / Math.PI;
-      ctx.setPreview?.(makeBoxcornerElement(cornerDragStart, armLength, ang, trussWidth, 'layer-0'));
+      ctx.setPreview?.(makeBoxcornerElement(cornerDragStart, armLength, ang, cornerAngle, trussWidth, 'layer-0'));
     },
     up(e, ctx) {
       const c = ctx as FullToolContext;
@@ -735,6 +738,7 @@ export const boxCornerTool: ToolExtensionV2 = {
       ctx.setPreview?.(null);
       if (!start || !c.doc) return;
       const armLength = (c.options.armLength as number | undefined) ?? 50;
+      const cornerAngle = (c.options.angle as number | undefined) ?? 90;
       const trussWidth = (c.options.trussWidth as number | undefined) ?? 29;
       const layerId = (c.options.layerId as string | undefined) ?? 'layer-0';
       const existing = (c.doc.getAllElements() as CADElement[]).filter(
@@ -743,11 +747,11 @@ export const boxCornerTool: ToolExtensionV2 = {
       const dock = cornerDockToDock(existing, start, DOCK_TOLERANCE);
       let el: CADElement;
       if (dock) {
-        el = makeBoxcornerElement(dock.vertex, armLength, dock.rotationDeg, trussWidth, layerId);
+        el = makeBoxcornerElement(dock.vertex, armLength, dock.rotationDeg, cornerAngle, trussWidth, layerId);
         ctx.setStatus(`Eck-Traverse angedockt an ${dock.dockedTo}`);
       } else {
         const ang = (Math.atan2(e.world.y - start.y, e.world.x - start.x) * 180) / Math.PI;
-        el = makeBoxcornerElement(start, armLength, ang, trussWidth, layerId);
+        el = makeBoxcornerElement(start, armLength, ang, cornerAngle, trussWidth, layerId);
         ctx.setStatus(`Eck-Traverse platziert (${armLength}cm Arme, Breite ${trussWidth}cm)`);
       }
       c.doc.transact(() => { c.doc!.addElement(el); });
@@ -760,6 +764,58 @@ export const boxCornerTool: ToolExtensionV2 = {
   },
 };
 
+// Task CAD-11: Kreis-Traverse
+function makeCircleTrussElement(
+  center: Pt,
+  diameter: number,
+  trussWidth: number,
+  chordCount: number,
+  layerId: string,
+): CADElement {
+  return {
+    id: `circletruss_${Date.now().toString(36)}_${Math.random().toString(36).slice(2, 9)}`,
+    type: 'circletruss',
+    layerId,
+    x: center.x,
+    y: center.y,
+    width: diameter,
+    height: diameter,
+    properties: {
+      diameter, trussWidth, chordCount, circletruss: true,
+      stroke: '#9aa0a6', strokeWidth: 2, fill: 'none',
+    },
+  } as unknown as CADElement;
+}
+
+export const circleTrussTool: ToolExtensionV2 = {
+  manifest: {
+    id: 'circle-truss',
+    label: 'Kreis-Traverse',
+    icon: '○',
+    ribbonTab: 'insert',
+    tags: ['basic'],
+    description: 'Kreis-Traverse platzieren (CAD-11)',
+  },
+  optionsSchema: [
+    { key: 'diameter', label: 'Durchmesser (cm)', type: 'number', min: 50, max: 1500 },
+    { key: 'trussWidth', label: 'Breite (cm)', type: 'number', min: 10, max: 60 },
+    { key: 'chordCount', label: 'Gurtrohre', type: 'number', min: 1, max: 4 },
+  ],
+  handlers: {
+    down(e, ctx) {
+      const c = ctx as FullToolContext;
+      if (!c.doc) return;
+      const diameter = Math.max(50, (c.options.diameter as number | undefined) ?? 200);
+      const trussWidth = (c.options.trussWidth as number | undefined) ?? 29;
+      const chordCount = Math.max(1, Math.min(4, (c.options.chordCount as number | undefined) ?? 2));
+      const layerId = (c.options.layerId as string | undefined) ?? 'layer-0';
+      const el = makeCircleTrussElement(e.world, diameter, trussWidth, chordCount, layerId);
+      c.doc.transact(() => { c.doc!.addElement(el); });
+      ctx.setStatus('Kreis-Traverse platziert');
+    },
+  },
+};
+
 export const eventToolsV2Plugin: PluginV2 = {
   manifest: {
     id: 'event-tools',
@@ -770,5 +826,5 @@ export const eventToolsV2Plugin: PluginV2 = {
     category: 'elements',
     enabledByDefault: true,
   },
-  tools: [chairTool, seatingRowToolDrag, seatingBlockToolDrag, tableTool, stageTool, arcRowTool, kinoTemplateTool, banquetTemplateTool, standingTableTemplateTool, podiumTemplateTool, curtainTool, spotlightTool, barrierTool, trussTool, boxCornerTool],
+  tools: [chairTool, seatingRowToolDrag, seatingBlockToolDrag, tableTool, stageTool, arcRowTool, kinoTemplateTool, banquetTemplateTool, standingTableTemplateTool, podiumTemplateTool, curtainTool, spotlightTool, barrierTool, trussTool, boxCornerTool, circleTrussTool],
 };
diff --git a/frontend/src/render/pixi/elementDrawers.ts b/frontend/src/render/pixi/elementDrawers.ts
index 90e6aba..0ca4a93 100644
--- a/frontend/src/render/pixi/elementDrawers.ts
+++ b/frontend/src/render/pixi/elementDrawers.ts
@@ -400,14 +400,16 @@ export function elementToPrimitives(el: CADElement, attrDefs?: Array<{ tag: stri
     }
 
     case 'truss': {
-      // Traverse (CAD-7/8): ROTIERTES Rechteck-Polygon + Gurtlinien
-      // entlang der Richtung (Fachwerk-Profil), Breite = trussWidth.
+      // Traverse (CAD-7/8/11): ROTIERTES Rechteck-Polygon + Gurtlinien
+      // entlang der Richtung (Fachwerk-Profil), Breite = trussWidth,
+      // chordCount = Anzahl Gurtrohre (CAD-11).
       const length = (props.length as number | undefined) ?? el.width;
       const tWidth = (props.trussWidth as number | undefined) ?? el.height ?? 29;
+      const chordCount = Math.max(1, Math.min(4, (props.chordCount as number | undefined) ?? 2));
       const rotDeg = (props.rotation as number | undefined) ?? 0;
       const rad = (rotDeg * Math.PI) / 180;
-      const ux = Math.cos(rad), uy = Math.sin(rad);          // Laengsrichtung
-      const nx = -Math.sin(rad), ny = Math.cos(rad);         // Normalenrichtung
+      const ux = Math.cos(rad), uy = Math.sin(rad);
+      const nx = -Math.sin(rad), ny = Math.cos(rad);
       const hl = length / 2, hw = tWidth / 2;
       const c = { x: el.x, y: el.y };
       const corner = (su: number, sv: number): { x: number; y: number } => ({
@@ -424,45 +426,58 @@ export function elementToPrimitives(el: CADElement, attrDefs?: Array<{ tag: stri
           stroke: strokeCol,
           strokeWidth: 2,
         },
-        // Gurtlinien oben/unten
-        {
-          kind: 'line',
-          from: corner(-1, -1),
-          to: corner(1, -1),
-          stroke: '#4b5563', strokeWidth: 1,
-        },
-        {
-          kind: 'line',
-          from: corner(-1, 1),
-          to: corner(1, 1),
-          stroke: '#4b5563', strokeWidth: 1,
-        },
       ];
+      // Gurtrohre: chordCount Linien gleichmaessig ueber die Breite verteilt
+      // chordCount=1: Mittellinie, chordCount=2: bei ±hw/2, chordCount=4: bei ±hw/2 und ±hw/6
+      for (let ci = 0; ci < chordCount; ci++) {
+        let sv: number;
+        if (chordCount === 1) sv = 0;
+        else if (chordCount === 2) sv = ci === 0 ? -0.5 : 0.5;
+        else if (chordCount === 3) sv = ci === 0 ? -0.67 : ci === 1 ? 0 : 0.67;
+        else sv = -0.75 + ci * 0.5; // chordCount=4: -0.75, -0.25, 0.25, 0.75
+        const chordPt = (su: number): { x: number; y: number } => ({
+          x: c.x + ux * (hl * su) + nx * (hw * sv),
+          y: c.y + uy * (hl * su) + ny * (hw * sv),
+        });
+        const from = chordPt(-1);
+        const to = chordPt(1);
+        out.push({ kind: 'line', from, to, stroke: '#4b5563', strokeWidth: 1 });
+      }
       return out;
     }
 
     case 'boxcorner': {
-      // Eck-Traverse (CAD-8): L-foermiges Polygon (6 Punkte) aus zwei
-      // Armen (rot und rot+90) um den Eckpunkt, Breite = trussWidth.
+      // Eck-Traverse (CAD-8/11): L-foermiges Polygon (6 Punkte) aus zwei
+      // Armen (rot und rot+angle) um den Eckpunkt, Breite = trussWidth,
+      // Winkel = angle (variabel, CAD-11, Default 90).
       const armLength = (props.armLength as number | undefined) ?? 50;
       const bWidth = (props.trussWidth as number | undefined) ?? 29;
       const rotDeg = (props.rotation as number | undefined) ?? 0;
+      const angleDeg = (props.angle as number | undefined) ?? 90;
       const rad = (rotDeg * Math.PI) / 180;
+      const rad2 = ((rotDeg + angleDeg) * Math.PI) / 180;
       const ux = Math.cos(rad), uy = Math.sin(rad);
       const nx = -Math.sin(rad), ny = Math.cos(rad);
-      const v = { x: el.x, y: el.y };
+      const vx = { x: el.x, y: el.y };
       const px = (a: number, b: number): { x: number; y: number } => ({
-        x: v.x + ux * a + nx * b,
-        y: v.y + uy * a + ny * b,
+        x: vx.x + ux * a + nx * b,
+        y: vx.y + uy * a + ny * b,
       });
-      // L-Geometrie: Arm1 entlang +u, Arm2 entlang +n (rot+90)
+      const ax2 = Math.cos(rad2), ay2 = Math.sin(rad2);
+      const pxa = (a: number, b: number): { x: number; y: number } => ({
+        x: vx.x + ax2 * a - ay2 * b,
+        y: vx.y + ay2 * a + ax2 * b,
+      });
+      // L-Geometrie: Arm1 entlang +u (rot), Arm2 entlang rot+angle
       const pts = [
         px(0, 0),
         px(armLength, 0),
         px(armLength, bWidth),
         px(bWidth, bWidth),
-        px(bWidth, armLength),
-        px(0, armLength),
+        pxa(bWidth, 0),
+        pxa(armLength, 0),
+        pxa(0, 0),
+        px(0, bWidth),
       ];
       const strokeCol = (props.stroke as string | undefined) ?? '#9aa0a6';
       return [{
@@ -474,6 +489,35 @@ export function elementToPrimitives(el: CADElement, attrDefs?: Array<{ tag: stri
       }];
     }
 
+    case 'circletruss': {
+      // Kreis-Traverse (CAD-11): Aussenkreis + Innenkreis +
+      // chordCount Gurtrohr-Kreise gleichmaessig verteilt.
+      const diameter = (props.diameter as number | undefined) ?? el.width;
+      const tWidth = (props.trussWidth as number | undefined) ?? 29;
+      const chordCount = Math.max(1, Math.min(4, (props.chordCount as number | undefined) ?? 2));
+      const rOuter = diameter / 2;
+      const rInner = rOuter - tWidth;
+      const strokeCol = (props.stroke as string | undefined) ?? '#9aa0a6';
+      const out: ShapePrimitive[] = [
+        { kind: 'circle', center: { x: el.x, y: el.y }, radius: rOuter, fill: null, stroke: strokeCol, strokeWidth: 2 },
+        { kind: 'circle', center: { x: el.x, y: el.y }, radius: rInner, fill: null, stroke: strokeCol, strokeWidth: 1 },
+      ];
+      // Gurtrohr-Kreise: gleichmaessig zwischen Aussen- und Innenkreis
+      const rMid = (rOuter + rInner) / 2;
+      for (let ci = 0; ci < chordCount; ci++) {
+        const ang = (2 * Math.PI * ci) / chordCount;
+        out.push({
+          kind: 'circle',
+          center: { x: el.x + Math.cos(ang) * rMid, y: el.y + Math.sin(ang) * rMid },
+          radius: tWidth * 0.15,
+          fill: null,
+          stroke: '#4b5563',
+          strokeWidth: 1,
+        });
+      }
+      return out;
+    }
+
     case 'barrier': {
       // Absperrung (Task E7): Kette aus Kreis-Paaren (properties.circles).
       const circles = Array.isArray(props.circles)
diff --git a/frontend/src/services/bomService.ts b/frontend/src/services/bomService.ts
index 703a9ba..a2a5234 100644
--- a/frontend/src/services/bomService.ts
+++ b/frontend/src/services/bomService.ts
@@ -10,16 +10,20 @@ import type { CADElement } from '../types/cad.types';
 
 export interface BOMRow {
   pos: number;
-  type: 'Traverse' | 'Eck-Traverse';
-  /** Laenge in cm (Traverse: length; Eck-Traverse: armLength). */
+  type: 'Traverse' | 'Eck-Traverse' | 'Kreis-Traverse';
+  /** Laenge in cm (Traverse: length; Eck-Traverse: armLength; Kreis: Durchmesser). */
   length: number;
   /** Breite in cm (trussWidth). */
   width: number;
   count: number;
-  /** Gesamtlaenge dieser Position in cm (count * length, Ecken * 2). */
+  /** Gesamtlaenge dieser Position in cm. */
   totalCm: number;
-  /** Bezeichnung, z.B. "Traverse 200 x 29". */
+  /** Bezeichnung. */
   label: string;
+  /** Gurtrohr-Anzahl (optional, CAD-11). */
+  chordCount?: number;
+  /** Eck-Winkel in Grad (optional, CAD-11). */
+  angle?: number;
 }
 
 export interface BOMResult {
@@ -29,9 +33,11 @@ export interface BOMResult {
 }
 
 interface GroupKey {
-  type: 'Traverse' | 'Eck-Traverse';
+  type: 'Traverse' | 'Eck-Traverse' | 'Kreis-Traverse';
   length: number;
   width: number;
+  chordCount?: number;
+  angle?: number;
 }
 
 /**
@@ -46,16 +52,27 @@ export function buildBOM(elements: CADElement[]): BOMResult {
     if (String(el.type) === 'truss' && el.properties.truss === true) {
       const length = (el.properties.length as number | undefined) ?? el.width ?? 0;
       const width = (el.properties.trussWidth as number | undefined) ?? el.height ?? 29;
-      const key: GroupKey = { type: 'Traverse', length, width };
-      const id = `T|${length}|${width}`;
+      const chordCount = (el.properties.chordCount as number | undefined) ?? 2;
+      const key: GroupKey = { type: 'Traverse', length, width, chordCount };
+      const id = `T|${length}|${width}|${chordCount}`;
       const g = groups.get(id) ?? { key, count: 0 };
       g.count++;
       groups.set(id, g);
     } else if (String(el.type) === 'boxcorner' && el.properties.boxcorner === true) {
       const length = (el.properties.armLength as number | undefined) ?? 50;
       const width = (el.properties.trussWidth as number | undefined) ?? 29;
-      const key: GroupKey = { type: 'Eck-Traverse', length, width };
-      const id = `C|${length}|${width}`;
+      const angle = (el.properties.angle as number | undefined) ?? 90;
+      const key: GroupKey = { type: 'Eck-Traverse', length, width, angle };
+      const id = `C|${length}|${width}|${angle}`;
+      const g = groups.get(id) ?? { key, count: 0 };
+      g.count++;
+      groups.set(id, g);
+    } else if (String(el.type) === 'circletruss' && el.properties.circletruss === true) {
+      const diameter = (el.properties.diameter as number | undefined) ?? el.width;
+      const width = (el.properties.trussWidth as number | undefined) ?? 29;
+      const chordCount = (el.properties.chordCount as number | undefined) ?? 2;
+      const key: GroupKey = { type: 'Kreis-Traverse', length: diameter, width, chordCount };
+      const id = `K|${diameter}|${width}|${chordCount}`;
       const g = groups.get(id) ?? { key, count: 0 };
       g.count++;
       groups.set(id, g);
@@ -73,8 +90,15 @@ export function buildBOM(elements: CADElement[]): BOMResult {
 
   const rows: BOMRow[] = entries.map((g, i) => {
     // Ecken haben 2 Arme: Gesamtlaenge = count * length * 2
+    // Kreis-Traversen: Umfang = Pi * Durchmesser
+    const isCircle = g.key.type === 'Kreis-Traverse';
     const armFactor = g.key.type === 'Eck-Traverse' ? 2 : 1;
-    const totalCm = g.count * g.key.length * armFactor;
+    const perPieceCm = isCircle ? Math.PI * g.key.length : g.key.length * armFactor;
+    const totalCm = g.count * perPieceCm;
+    const detailParts: string[] = [];
+    if (g.key.chordCount !== undefined && g.key.chordCount > 0) detailParts.push(`${g.key.chordCount}-rohr`);
+    if (g.key.angle !== undefined && g.key.angle !== 90) detailParts.push(`${g.key.angle}°`);
+    const detailSuffix = detailParts.length > 0 ? ` (${detailParts.join(', ')})` : '';
     return {
       pos: i + 1,
       type: g.key.type,
@@ -82,7 +106,9 @@ export function buildBOM(elements: CADElement[]): BOMResult {
       width: g.key.width,
       count: g.count,
       totalCm,
-      label: `${g.key.type} ${g.key.length} \u00d7 ${g.key.width}`,
+      label: `${g.key.type} ${isCircle ? '⌀' : ''}${g.key.length} × ${g.key.width}${detailSuffix}`,
+      chordCount: g.key.chordCount,
+      angle: g.key.angle,
     };
   });
 
diff --git a/frontend/src/types/cad.types.ts b/frontend/src/types/cad.types.ts
index 6731afb..1277cbf 100644
--- a/frontend/src/types/cad.types.ts
+++ b/frontend/src/types/cad.types.ts
@@ -7,7 +7,7 @@ export type ElementType =
   | 'polyline' | 'text' | 'dimension' | 'block_instance' | 'chair'
   | 'seating-row' | 'seating-block' | 'table' | 'stage'
   | 'leader' | 'revcloud' | 'image'
-  | 'curtain' | 'spotlight' | 'barrier' | 'truss' | 'boxcorner';
+  | 'curtain' | 'spotlight' | 'barrier' | 'truss' | 'boxcorner' | 'circletruss';
 
 export type LineType = 'solid' | 'dashed' | 'dotted';
 
diff --git a/frontend/tests/trussPro.test.ts b/frontend/tests/trussPro.test.ts
new file mode 100644
index 0000000..0e2c750
--- /dev/null
+++ b/frontend/tests/trussPro.test.ts
@@ -0,0 +1,254 @@
+/**
+ * Task CAD-11 - Truss Professional Upgrade:
+ * 1. chordCount (Anzahl Gurtrohre, 1-4) einstellbar
+ * 2. Laenge als freier Zahleneintrag (nicht nur Presets)
+ * 3. Corner mit variablem Winkel (nicht nur 90 Grad)
+ * 4. Kreis-Traverse als eigenes Tool
+ * 5. BOM beruecksichtigt chordCount und Kreistraversen
+ */
+import { describe, it, expect, beforeEach } from 'vitest';
+import {
+  trussTool,
+  boxCornerTool,
+  circleTrussTool,
+  trussEndpoints,
+  boxcornerEndpoints,
+} from '../src/plugins/builtin/event-tools';
+import { buildBOM } from '../src/services/bomService';
+import { elementToPrimitives } from '../src/render/pixi/elementDrawers';
+import { CADDocument } from '../src/kernel/document/CADDocument';
+import { createInMemoryDoc } from './helpers/inMemoryDoc';
+import type { CADElement, Pt } from '../src/types/cad.types';
+
+function mkCtx(elements: CADElement[] = [], options: Record<string, unknown> = {}) {
+  const { ydoc } = createInMemoryDoc();
+  const doc = new CADDocument(ydoc);
+  for (const el of elements) doc.addElement(el);
+  const statuses: string[] = [];
+  const previews: (CADElement | null)[] = [];
+  const ctx: any = {
+    doc,
+    options,
+    setStatus: (m: string) => statuses.push(m),
+    setPreview: (el: CADElement | null) => previews.push(el),
+  };
+  return { ctx, doc, statuses, previews };
+}
+
+function pe(x: number, y: number): { world: Pt } {
+  return { world: { x, y } } as never;
+}
+
+function makeTruss(id: string, x: number, y: number, length: number, rotation: number, width = 29, chordCount = 2): CADElement {
+  return {
+    id, type: 'truss', layerId: 'l', x, y, width: length, height: width,
+    properties: { length, rotation, trussWidth: width, chordCount, truss: true },
+  } as unknown as CADElement;
+}
+
+function makeCorner(id: string, x: number, y: number, armLength = 50, rotation = 0, angle = 90, width = 29): CADElement {
+  return {
+    id, type: 'boxcorner', layerId: 'l', x, y, width: 80, height: 80,
+    properties: { armLength, rotation, angle, trussWidth: width, boxcorner: true },
+  } as unknown as CADElement;
+}
+
+function makeCircleTruss(id: string, x: number, y: number, diameter: number, width = 29, chordCount = 2): CADElement {
+  return {
+    id, type: 'circletruss', layerId: 'l', x, y, width: diameter, height: diameter,
+    properties: { diameter, trussWidth: width, chordCount, circletruss: true },
+  } as unknown as CADElement;
+}
+
+beforeEach(() => {
+  for (const t of [trussTool, boxCornerTool, circleTrussTool]) {
+    t.handlers.cancel?.({ setStatus: () => {}, setPreview: () => {} } as never);
+  }
+});
+
+// ─── 1: chordCount (Gurtrohre) ──────────────────────────────
+
+describe('CAD-11: chordCount', () => {
+  it('trussTool hat chordCount-Option (number, 1-4, Default 2)', () => {
+    const field = trussTool.optionsSchema?.find((f) => f.key === 'chordCount');
+    expect(field).toBeDefined();
+    expect(field!.type).toBe('number');
+  });
+
+  it('platzierte Traverse: chordCount=2 Standard', () => {
+    const { ctx, doc } = mkCtx();
+    trussTool.handlers.down!(pe(100, 100), ctx);
+    trussTool.handlers.up!(pe(300, 100), ctx);
+    expect(doc.getAllElements()[0].properties.chordCount).toBe(2);
+  });
+
+  it('chordCount=3 wird uebernommen', () => {
+    const { ctx, doc } = mkCtx([], { chordCount: 3 });
+    trussTool.handlers.down!(pe(100, 100), ctx);
+    trussTool.handlers.up!(pe(300, 100), ctx);
+    expect(doc.getAllElements()[0].properties.chordCount).toBe(3);
+  });
+
+  it('Rendering: chordCount=2 zeigt 2 Gurtlinien, chordCount=4 zeigt 4', () => {
+    const t2 = makeTruss('t2', 100, 100, 200, 0, 29, 2);
+    const t4 = makeTruss('t4', 100, 100, 200, 0, 29, 4);
+    const prims2 = elementToPrimitives(t2).filter((p) => p.kind === 'line' && p.stroke === '#4b5563');
+    const prims4 = elementToPrimitives(t4).filter((p) => p.kind === 'line' && p.stroke === '#4b5563');
+    expect(prims2.length).toBe(2);
+    expect(prims4.length).toBe(4);
+  });
+
+  it('chordCount=1: eine Mittellinie', () => {
+    const t1 = makeTruss('t1', 100, 100, 200, 0, 29, 1);
+    const lines = elementToPrimitives(t1).filter((p) => p.kind === 'line' && p.stroke === '#4b5563');
+    expect(lines.length).toBe(1);
+    const line = lines[0] as { from: Pt; to: Pt };
+    expect(line.from.y).toBeCloseTo(100, 0); // Mittellinie auf y=100
+  });
+});
+
+// ─── 2: Freie Laengeneingabe ─────────────────────────────────
+
+describe('CAD-11: Laenge als freier Zahleneintrag', () => {
+  it('length ist number (nicht select) — Presets als separate Quick-Buttons', () => {
+    const field = trussTool.optionsSchema?.find((f) => f.key === 'length');
+    expect(field).toBeDefined();
+    expect(field!.type).toBe('number');
+  });
+
+  it('Custom-Laenge 175 wird uebernommen', () => {
+    const { ctx, doc } = mkCtx([], { length: 175 });
+    trussTool.handlers.down!(pe(100, 100), ctx);
+    trussTool.handlers.up!(pe(300, 100), ctx);
+    expect(doc.getAllElements()[0].properties.length).toBe(175);
+  });
+});
+
+// ─── 3: Corner mit variablem Winkel ─────────────────────────
+
+describe('CAD-11: Corner variablem Winkel', () => {
+  it('boxCornerTool hat angle-Option (number, Default 90)', () => {
+    const field = boxCornerTool.optionsSchema?.find((f) => f.key === 'angle');
+    expect(field).toBeDefined();
+    expect(field!.type).toBe('number');
+  });
+
+  it('boxcornerEndpoints: 90-Grad-Ecke = Arm2 bei rot+90', () => {
+    const c = makeCorner('c1', 100, 100, 50, 0, 90);
+    const [a1, a2] = boxcornerEndpoints(c);
+    expect(a1.x).toBeCloseTo(150, 0);
+    expect(a1.y).toBeCloseTo(100, 0);
+    expect(a2.x).toBeCloseTo(100, 0);
+    expect(a2.y).toBeCloseTo(150, 0);
+  });
+
+  it('boxcornerEndpoints: 45-Grad-Ecke = Arm2 bei rot+45', () => {
+    const c = makeCorner('c1', 100, 100, 50, 0, 45);
+    const [a1, a2] = boxcornerEndpoints(c);
+    expect(a1.x).toBeCloseTo(150, 0);
+    expect(a1.y).toBeCloseTo(100, 0);
+    const halfDiag = 50 * Math.cos(Math.PI / 4);
+    expect(a2.x).toBeCloseTo(100 + halfDiag, 0);
+    expect(a2.y).toBeCloseTo(100 + halfDiag, 0);
+  });
+
+  it('platzierte 30-Grad-Ecke: angle=30 in properties', () => {
+    const { ctx, doc } = mkCtx([], { angle: 30 });
+    boxCornerTool.handlers.down!(pe(100, 100), ctx);
+    boxCornerTool.handlers.up!(pe(200, 100), ctx);
+    expect(doc.getAllElements()[0].properties.angle).toBe(30);
+  });
+
+  it('Default-Winkel ist 90 (abwaertskompatibel)', () => {
+    const { ctx, doc } = mkCtx();
+    boxCornerTool.handlers.down!(pe(100, 100), ctx);
+    boxCornerTool.handlers.up!(pe(200, 100), ctx);
+    expect(doc.getAllElements()[0].properties.angle).toBe(90);
+  });
+
+  it('Rendering: 90-Grad = L-Form, 45-Grad = spitzeres V', () => {
+    const c90 = makeCorner('c90', 100, 100, 50, 0, 90, 29);
+    const c45 = makeCorner('c45', 100, 100, 50, 0, 45, 29);
+    const p90 = elementToPrimitives(c90).find((p) => p.kind === 'polyline') as { points: Pt[] };
+    const p45 = elementToPrimitives(c45).find((p) => p.kind === 'polyline') as { points: Pt[] };
+    // Beide sind Polygone mit >= 6 Punkten
+    expect(p90.points.length).toBeGreaterThanOrEqual(6);
+    expect(p45.points.length).toBeGreaterThanOrEqual(6);
+    // 45-Grad-Ecke: zweiter Arm diagonal → Y-Ausdehnung kleiner als bei 90°
+    const maxY90 = Math.max(...p90.points.map((p) => p.y));
+    const maxY45 = Math.max(...p45.points.map((p) => p.y));
+    expect(maxY45).toBeLessThan(maxY90);
+  });
+});
+
+// ─── 4: Kreis-Traverse ──────────────────────────────────────
+
+describe('CAD-11: Kreis-Traverse', () => {
+  it('circleTrussTool existiert mit Manifest', () => {
+    expect(circleTrussTool.manifest.id).toBe('circle-truss');
+    const keys = (circleTrussTool.optionsSchema ?? []).map((f) => f.key);
+    expect(keys).toContain('diameter');
+    expect(keys).toContain('trussWidth');
+  });
+
+  it('Klick platziert Kreistraverse mit diameter/trussWidth/chordCount', () => {
+    const { ctx, doc } = mkCtx([], { diameter: 300, trussWidth: 29, chordCount: 2 });
+    circleTrussTool.handlers.down!(pe(200, 200), ctx);
+    const els = doc.getAllElements();
+    expect(els).toHaveLength(1);
+    expect(els[0].type).toBe('circletruss');
+    expect(els[0].properties.diameter).toBe(300);
+    expect(els[0].properties.trussWidth).toBe(29);
+    expect(els[0].properties.chordCount).toBe(2);
+  });
+
+  it('Kreis-Traverse: Rendering zeigt Aussen- und Innenkreis + Gurtrohr-Kreise', () => {
+    const ct = makeCircleTruss('ct1', 200, 200, 300, 29, 2);
+    const prims = elementToPrimitives(ct);
+    const circles = prims.filter((p) => p.kind === 'circle');
+    // Aussen + Innen + chordCount-Kreise = mindestens 4
+    expect(circles.length).toBeGreaterThanOrEqual(4);
+  });
+
+  it('1 Undo entfernt die Kreistraverse', () => {
+    const { ctx, doc } = mkCtx();
+    circleTrussTool.handlers.down!(pe(200, 200), ctx);
+    expect(doc.getAllElements()).toHaveLength(1);
+    doc.undo();
+    expect(doc.getAllElements()).toHaveLength(0);
+  });
+
+  it('diameter-Default ist 200', () => {
+    const { ctx, doc } = mkCtx();
+    circleTrussTool.handlers.down!(pe(200, 200), ctx);
+    expect(doc.getAllElements()[0].properties.diameter).toBe(200);
+  });
+});
+
+// ─── 5: BOM-Integration ─────────────────────────────────────
+
+describe('CAD-11: BOM mit chordCount + Kreistraversen', () => {
+  it('BOM gruppiert nach chordCount (2-rohr vs 4-rohr getrennt)', () => {
+    const els = [
+      makeTruss('t1', 0, 0, 200, 0, 29, 2),
+      makeTruss('t2', 0, 0, 200, 0, 29, 4),
+    ];
+    const bom = buildBOM(els);
+    expect(bom.rows.filter((r) => r.type === 'Traverse')).toHaveLength(2);
+  });
+
+  it('BOM enthaelt Kreistraversen mit Durchmesser', () => {
+    const els = [makeCircleTruss('ct1', 200, 200, 300, 29, 2)];
+    const bom = buildBOM(els);
+    expect(bom.rows).toHaveLength(1);
+    expect(bom.rows[0].label).toContain('Kreis');
+    expect(bom.rows[0].label).toContain('300');
+  });
+
+  it('Kreistraverse-Umfang zaehlt in Gesamtlaenge (Pi * d)', () => {
+    const els = [makeCircleTruss('ct1', 200, 200, 300, 29, 2)];
+    const bom = buildBOM(els);
+    const expected = (Math.PI * 300) / 100; // ~9.42m
+    expect(bom.totalLengthM).toBeCloseTo(expected, 1);
+  });
+});
diff --git a/frontend/tests/trussUpgrade.test.ts b/frontend/tests/trussUpgrade.test.ts
index 1475992..65625f2 100644
--- a/frontend/tests/trussUpgrade.test.ts
+++ b/frontend/tests/trussUpgrade.test.ts
@@ -67,11 +67,12 @@ beforeEach(() => {
 // ─── 1: Laengen-Presets + Breite ──────────────────────────────
 
 describe('CAD-8: Laengen-Presets + Breite', () => {
-  it('Laengen-Select: genau 50/100/200/300 cm', () => {
+  it('Laengen-Select: freie Eingabe mit 50-300 Bereich (CAD-11: number)', () => {
     const lenField = trussTool.optionsSchema?.find((f) => f.key === 'length');
     expect(lenField).toBeDefined();
-    expect(lenField!.type).toBe('select');
-    expect((lenField!.options ?? []).map((o) => o.value)).toEqual(['50', '100', '200', '300']);
+    expect(lenField!.type).toBe('number');
+    expect(lenField!.min).toBe(10);
+    expect(lenField!.max).toBe(1000);
   });
 
   it('Breiten-Option trussWidth (number) vorhanden', () => {
@@ -296,7 +297,7 @@ describe('CAD-8: Boxcorner-Rendering (L-Form)', () => {
     const poly = prims.find((p) => p.kind === 'polyline') as { points: Pt[]; close: boolean };
     expect(poly).toBeDefined();
     expect(poly.close).toBe(true);
-    expect(poly.points).toHaveLength(6); // L-Geometrie: 6 Punkte
+    expect(poly.points).toHaveLength(8); // CAD-11: variable-angle Geometrie hat 8 Punkte
     const minDist = Math.min(...poly.points.map((p) => Math.hypot(p.x - 100, p.y - 100)));
     expect(minDist).toBeLessThanOrEqual(29);
   });