diff --git a/mock/e2e/phy.spec.ts b/mock/e2e/phy.spec.ts
index a543506..e935bac 100644
--- a/mock/e2e/phy.spec.ts
+++ b/mock/e2e/phy.spec.ts
@@ -115,6 +115,23 @@ test("ドラッグ中に右端で自動スクロールし、Undo 1回で戻る",
   await expect(key).toHaveAttribute("transform", before!);
 });
 
+test("選択中のクラスターにだけ原点の丸を出す", async ({ page }) => {
+  const keys = page.locator('[data-node-type="key"]');
+  const corner = (await keys.nth(0).locator(".key-face").boundingBox())!;
+  const cluster = await makeCluster(page);
+  const clusterId = await cluster.getAttribute("data-node-id");
+  await keys.nth(5).click();
+  await expect(page.locator(".origin")).toHaveCount(0);
+  await page.locator(`[data-tree-id="${clusterId}"]`).first().click();
+  const origin = page.locator(`[data-origin-id="${clusterId}"]`);
+  await expect(origin).toHaveCount(1);
+  const box = (await origin.boundingBox())!;
+  expect(Math.abs(box.x + box.width / 2 - corner.x)).toBeLessThan(2);
+  expect(Math.abs(box.y + box.height / 2 - corner.y)).toBeLessThan(2);
+  await keys.nth(5).click();
+  await expect(page.locator(".origin")).toHaveCount(0);
+});
+
 test("クラスター化で画面位置を保つ", async ({ page }) => {
   const keys = page.locator('[data-node-type="key"]');
   const centers = async () =>
diff --git a/mock/src/ui/phy/PhyEditor.vue b/mock/src/ui/phy/PhyEditor.vue
index d94e75e..7d1e7de 100644
--- a/mock/src/ui/phy/PhyEditor.vue
+++ b/mock/src/ui/phy/PhyEditor.vue
@@ -399,6 +399,7 @@ function onFocus(_id: string) {
             :nodes="focus ? [node(focus)!] : project.phy.root"
             :selected="selected"
             :variants="variants"
+            :zoom="zoom"
             :candidate="longLabel ? (holdCandidates[holdIndex] ?? null) : null"
             :parent="focus ? focusParentMatrix(focus) : undefined"
           />
diff --git a/mock/src/ui/phy/PhySelectionLayer.vue b/mock/src/ui/phy/PhySelectionLayer.vue
index 6186cfc..2dc5e49 100644
--- a/mock/src/ui/phy/PhySelectionLayer.vue
+++ b/mock/src/ui/phy/PhySelectionLayer.vue
@@ -8,6 +8,7 @@ const props = withDefaults(
     nodes: Node[];
     selected: string[];
     variants: Record<string, string>;
+    zoom: number;
     candidate?: string | null;
     parent?: Affine;
   }>(),
@@ -16,6 +17,8 @@ const props = withDefaults(
 const frames = computed(() =>
   selectionFrames(props.nodes, props.selected, props.variants, props.candidate, props.parent),
 );
+// 原点の丸は選択中のクラスター(VariantGroupを含む)にだけ出す。T-30。
+const origins = computed(() => frames.value.filter((frame) => frame.selected && frame.type !== "key"));
 const affineText = (m: Affine) => `matrix(${m.a} ${m.b} ${m.c} ${m.d} ${m.e} ${m.f})`;
 </script>
 <template>
@@ -31,6 +34,15 @@ const affineText = (m: Affine) => `matrix(${m.a} ${m.b} ${m.c} ${m.d} ${m.e} ${m
       :width="frame.box.width"
       :height="frame.box.height"
     />
+    <circle
+      v-for="frame in origins"
+      :key="`origin-${frame.id}`"
+      :data-origin-id="frame.id"
+      class="origin"
+      :cx="frame.transform.e"
+      :cy="frame.transform.f"
+      :r="5 / zoom"
+    />
   </g>
 </template>
 <style scoped>
@@ -48,4 +60,10 @@ const affineText = (m: Affine) => `matrix(${m.a} ${m.b} ${m.c} ${m.d} ${m.e} ${m
   stroke: #e87912;
   stroke-width: 3.5px;
 }
+.origin {
+  fill: #fff;
+  stroke: #1769d2;
+  stroke-width: 2px;
+  vector-effect: non-scaling-stroke;
+}
 </style>
diff --git a/mock/src/ui/phy/logic.ts b/mock/src/ui/phy/logic.ts
index 1872223..df5e9a6 100644
--- a/mock/src/ui/phy/logic.ts
+++ b/mock/src/ui/phy/logic.ts
@@ -235,6 +235,7 @@ export type SelectionFrame = {
   type: Node["type"];
   transform: Affine;
   box: Box;
+  selected: boolean;
   candidate: boolean;
 };
 /** 可視ノードの選択枠をワールド行列とローカル矩形で返す。 */
@@ -255,6 +256,7 @@ export function selectionFrames(
           type: node.type,
           transform,
           box: { x: 0, y: 0, width: node.size.w, height: node.size.h },
+          selected: selected.includes(node.id),
           candidate: candidate === node.id,
         });
       } else if (node.type === "cluster") {
@@ -264,6 +266,7 @@ export function selectionFrames(
             type: node.type,
             transform,
             box: localBounds(node.children, variants),
+            selected: selected.includes(node.id),
             candidate: candidate === node.id,
           });
         visit(node.children, transform);
@@ -275,6 +278,7 @@ export function selectionFrames(
             type: node.type,
             transform,
             box: localBounds(variant?.children ?? [], variants),
+            selected: selected.includes(node.id),
             candidate: candidate === node.id,
           });
         if (variant) visit(variant.children, transform);
diff --git a/mock/tests/phyLogic.test.ts b/mock/tests/phyLogic.test.ts
index a59f1eb..b4c24bb 100644
--- a/mock/tests/phyLogic.test.ts
+++ b/mock/tests/phyLogic.test.ts
@@ -65,6 +65,9 @@ describe("PHY pure interaction rules", () => {
     expect(frame.transform.f).toBeCloseTo(27);
     expect(frame.transform.a).toBeCloseTo(Math.cos(Math.PI / 6));
     expect(frame.transform.b).toBeCloseTo(Math.sin(Math.PI / 6));
+    expect(frame.selected).toBe(true);
+    const candidateOnly = selectionFrames(roots, [], {}, "target")[0]!;
+    expect([candidateOnly.selected, candidateOnly.candidate]).toEqual([false, true]);
   });
   it("removes ancestors and descendants from mixed selections", () => {
     expect(normalizeSelection(phy, ["c", "k"])).toEqual(["k"]);