diff --git a/B07_DesignDetail/openwebcad/src/App.css b/B07_DesignDetail/openwebcad/src/App.css
index 7c36bfacc..21519acc1 100644
--- a/B07_DesignDetail/openwebcad/src/App.css
+++ b/B07_DesignDetail/openwebcad/src/App.css
@@ -334,6 +334,8 @@ body > canvas[data-id="canvas"] {
 	border-radius: 3px;
 	cursor: pointer;
 }
+/* 고른 것들 색이 다름(488) — 빈 견본(투명 · 점선 테두리) */
+input[type="color"][data-mixed="true"]::-webkit-color-swatch { background: transparent !important; border: 1px dashed var(--cad-text-muted); }
 /* 위젯 패널 안의 작은 명령 버튼은 한 줄 높이에 맞춘다 */
 .cad-ribbon-props .cad-tool[data-size="small"] {
 	height: 22px;
diff --git a/B07_DesignDetail/openwebcad/src/components/PropertiesEditor.tsx b/B07_DesignDetail/openwebcad/src/components/PropertiesEditor.tsx
index 2512617f9..ae9191758 100644
--- a/B07_DesignDetail/openwebcad/src/components/PropertiesEditor.tsx
+++ b/B07_DesignDetail/openwebcad/src/components/PropertiesEditor.tsx
@@ -2,25 +2,31 @@
 import type { FC } from 'react';
 import type { Entity } from '../entities/Entity';
 import { polylineLength, sampleEntityPoints } from '../helpers/geometry/sample-entity';
-import { getEntities, getLayers, getSelectedEntities, setEntities } from '../state';
-import { dashToLineType, LINE_TYPES, LINE_WIDTHS } from './RibbonWidgets';
+import {
+	commonValue,
+	LINE_TYPES,
+	LINE_WIDTHS,
+	restyle,
+	selectionLineStyle,
+	styleTargets,
+} from '../helpers/selection-style';
+import { getLayers, getSelectedEntities } from '../state';
 
 interface PropertiesEditorProps {
 	compact?: boolean;
 }
 
-function applyToSelection(mutate: (entity: Entity) => void): void {
-	const selected = getSelectedEntities();
-	if (!selected.length) return;
-	for (const entity of selected) mutate(entity);
-	setEntities([...getEntities()], true);
-}
+/** 고른 것을 사본으로 바꿈 — 되돌리기 한 칸(488) · 선 특성은 글 뺌 */
+const applyToSelection = (mutate: (entity: Entity) => void) => restyle(getSelectedEntities(), mutate);
+const applyToLines = (mutate: (entity: Entity) => void) =>
+	restyle(styleTargets(getSelectedEntities()), mutate);
 
-/** 여러 객체가 값이 다르면 '*가지각색' 대신 첫 객체 값을 보여 준다 (AutoCAD와 같은 관행) */
+/** 여러 객체가 값이 다르면 빈 칸(488 · 리본과 같은 규칙 · 고르면 모두에 적용) */
 export const PropertiesEditor: FC<PropertiesEditorProps> = ({ compact = false }) => {
 	const selected = getSelectedEntities();
 	const layers = getLayers();
 	const first = selected[0];
+	const view = selectionLineStyle();
 
 	if (!first) {
 		return <p className="cad-properties__empty">선택된 객체가 없습니다.</p>;
@@ -39,9 +45,10 @@ export const PropertiesEditor: FC<PropertiesEditorProps> = ({ compact = false })
 				<span>색상</span>
 				<input
 					type="color"
-					value={first.lineColor}
+					value={view.color || '#000000'}
+					data-mixed={view.color ? undefined : 'true'}
 					onChange={(event) =>
-						applyToSelection((entity) => {
+						applyToLines((entity) => {
 							entity.lineColor = event.target.value;
 						})
 					}
@@ -51,13 +58,14 @@ export const PropertiesEditor: FC<PropertiesEditorProps> = ({ compact = false })
 			<label>
 				<span>선 두께</span>
 				<select
-					value={first.lineWidth}
+					value={view.width}
 					onChange={(event) =>
-						applyToSelection((entity) => {
+						applyToLines((entity) => {
 							entity.lineWidth = Number(event.target.value);
 						})
 					}
 				>
+					<option value="" hidden />
 					{LINE_WIDTHS.map((width) => (
 						<option key={width} value={width}>
 							{width}px
@@ -69,14 +77,15 @@ export const PropertiesEditor: FC<PropertiesEditorProps> = ({ compact = false })
 			<label>
 				<span>선종류</span>
 				<select
-					value={dashToLineType(first.lineDash)}
+					value={view.lineType}
 					onChange={(event) => {
 						const dash = LINE_TYPES.find((type) => type.value === event.target.value)?.dash;
-						applyToSelection((entity) => {
+						applyToLines((entity) => {
 							entity.lineDash = dash ? [...dash] : undefined;
 						});
 					}}
 				>
+					<option value="" hidden />
 					{LINE_TYPES.map((type) => (
 						<option key={type.value} value={type.value}>
 							{type.label}
@@ -88,13 +97,14 @@ export const PropertiesEditor: FC<PropertiesEditorProps> = ({ compact = false })
 			<label>
 				<span>레이어</span>
 				<select
-					value={first.layerId}
+					value={commonValue(selected, (entity) => entity.layerId)}
 					onChange={(event) =>
 						applyToSelection((entity) => {
 							entity.layerId = event.target.value;
 						})
 					}
 				>
+					<option value="" hidden />
 					{layers.map((layer) => (
 						<option key={layer.id} value={layer.id}>
 							{layer.name}
diff --git a/B07_DesignDetail/openwebcad/src/components/RibbonWidgets.tsx b/B07_DesignDetail/openwebcad/src/components/RibbonWidgets.tsx
index 14b870c3b..4b77e6555 100644
--- a/B07_DesignDetail/openwebcad/src/components/RibbonWidgets.tsx
+++ b/B07_DesignDetail/openwebcad/src/components/RibbonWidgets.tsx
@@ -4,11 +4,16 @@ import { runCommandInput } from '../commands/run-command';
 import type { Entity } from '../entities/Entity';
 import { EntityName } from '../entities/Entity';
 import type { TextEntity } from '../entities/TextEntity';
+import {
+	LINE_TYPES,
+	LINE_WIDTHS,
+	repaint,
+	restyle,
+	selectionLineStyle,
+	styleTargets,
+} from '../helpers/selection-style';
 import {
 	getActiveLayerId,
-	getActiveLineColor,
-	getActiveLineDash,
-	getActiveLineWidth,
 	getActiveTextStyle,
 	getEntities,
 	getLayers,
@@ -21,50 +26,31 @@ import {
 	setEntities,
 } from '../state';
 
-export const LINE_TYPES: { value: string; label: string; dash: number[] | undefined }[] = [
-	{ value: 'solid', label: '실선', dash: undefined },
-	{ value: 'dashed', label: '파선', dash: [10, 5] },
-	{ value: 'dashdot', label: '1점쇄선', dash: [12, 4, 2, 4] },
-	{ value: 'dotted', label: '점선', dash: [2, 4] },
-];
-
-export const LINE_WIDTHS = [1, 2, 3, 4, 5];
-
 const FONT_FAMILIES = ['Noto Sans KR', 'Malgun Gothic', 'Pretendard', 'Arial', 'monospace'];
 
-export const dashToLineType = (dash: number[] | undefined): string =>
-	LINE_TYPES.find((type) => JSON.stringify(type.dash) === JSON.stringify(dash))?.value ?? 'solid';
-
-/** 선택 객체가 있으면 즉시 적용하고, 없으면 이후 그리기 기본값만 바꾼다. */
-function applyToSelection(mutate: (entity: Entity) => void, trackInUndoStack = true): boolean {
-	const selected = getSelectedEntities();
-	if (!selected.length) return false;
-	for (const entity of selected) {
-		mutate(entity);
-	}
-	setEntities([...getEntities()], trackInUndoStack);
-	return true;
-}
-
 /**
  * 색 선택기는 드래그하는 내내 값 변경을 쏜다. 그 하나하나를 되돌리기·변경통지에 실으면
- * 색 한 번 고르는 동안 수십 건이 나간다(2026-09-01 지적). 끄는 동안에는 화면만 칠하고,
- * 멎은 뒤 한 번만 되돌리기·통지에 싣는다.
+ * 색 한 번 고르는 동안 수십 건이 나간다(2026-09-01 지적). 첫 변경에 사본을 끼우고 끄는 동안에는
+ * 그 사본만 칠하고, 멎은 뒤 한 번만 되돌리기·통지에 싣는다(488 — Ctrl+Z 한 번에 옛 색).
  */
 const COLOR_COMMIT_DELAY_MS = 350;
 let colorCommitTimer: ReturnType<typeof setTimeout> | undefined;
-function paintNowCommitLater(mutate: (entity: Entity) => void): void {
-	applyToSelection(mutate, false); // 화면만 — 되돌리기·미저장 표시는 아직
+let painting: Entity[] | null = null;
+function paintNowCommitLater(targets: Entity[], change: (entity: Entity) => void): void {
+	if (painting) repaint(painting, change);
+	else painting = restyle(targets, change, false); // 화면만
 	clearTimeout(colorCommitTimer);
 	colorCommitTimer = setTimeout(() => {
-		applyToSelection(() => {}, true); // 멎었다 — 이번 한 번만 실어 보낸다
+		painting = null;
+		setEntities([...getEntities()], true); // 멎었다 — 이번 한 번만 실어 보낸다
 	}, COLOR_COMMIT_DELAY_MS);
 }
 
+/** 고른 선 있으면 그것만 바꿈(488 — 그리기 기본값 그대로) · 없으면 그리기 기본값만 */
+const selectedLines = () => styleTargets(getSelectedEntities());
+
 export const PropertiesWidget: FC = () => {
-	const lineColor = getActiveLineColor();
-	const lineWidth = getActiveLineWidth();
-	const lineType = dashToLineType(getActiveLineDash());
+	const view = selectionLineStyle();
 
 	return (
 		<div className="cad-ribbon-props">
@@ -72,11 +58,13 @@ export const PropertiesWidget: FC = () => {
 				<span>색상</span>
 				<input
 					type="color"
-					value={lineColor}
+					value={view.color || '#000000'}
+					data-mixed={view.color ? undefined : 'true'}
 					onChange={(event) => {
 						const color = event.target.value;
-						setActiveLineColor(color);
-						paintNowCommitLater((entity) => {
+						const lines = selectedLines();
+						if (!lines.length) return setActiveLineColor(color);
+						paintNowCommitLater(lines, (entity) => {
 							entity.lineColor = color;
 						});
 					}}
@@ -85,15 +73,17 @@ export const PropertiesWidget: FC = () => {
 			<label className="cad-prop" title="선 두께 (LWEIGHT)">
 				<span>선 두께</span>
 				<select
-					value={lineWidth}
+					value={view.width}
 					onChange={(event) => {
 						const width = Number(event.target.value);
-						setActiveLineWidth(width);
-						applyToSelection((entity) => {
+						const lines = selectedLines();
+						if (!lines.length) return setActiveLineWidth(width);
+						restyle(lines, (entity) => {
 							entity.lineWidth = width;
 						});
 					}}
 				>
+					<option value="" hidden />
 					{LINE_WIDTHS.map((width) => (
 						<option key={width} value={width}>
 							{width}px
@@ -104,15 +94,17 @@ export const PropertiesWidget: FC = () => {
 			<label className="cad-prop" title="선종류 (LINETYPE)">
 				<span>선종류</span>
 				<select
-					value={lineType}
+					value={view.lineType}
 					onChange={(event) => {
 						const dash = LINE_TYPES.find((type) => type.value === event.target.value)?.dash;
-						setActiveLineDash(dash ? [...dash] : undefined);
-						applyToSelection((entity) => {
+						const lines = selectedLines();
+						if (!lines.length) return setActiveLineDash(dash ? [...dash] : undefined);
+						restyle(lines, (entity) => {
 							entity.lineDash = dash ? [...dash] : undefined;
 						});
 					}}
 				>
+					<option value="" hidden />
 					{LINE_TYPES.map((type) => (
 						<option key={type.value} value={type.value}>
 							{type.label}
@@ -163,14 +155,11 @@ export const TextStyleWidget: FC = () => {
 
 	const handle = (patch: Partial<typeof textStyle>, live = false) => {
 		setActiveTextStyle(patch);
-		const mutate = (entity: Entity) => {
-			if (entity.getType() === EntityName.Text) {
-				(entity as TextEntity).setTextOptions(patch);
-			}
-		};
+		const texts = getSelectedEntities().filter((entity) => entity.getType() === EntityName.Text);
+		const mutate = (entity: Entity) => (entity as TextEntity).setTextOptions(patch);
 		// 색만 드래그 중 연발한다 — 나머지 항목은 한 번 고르면 끝이라 바로 싣는다.
-		if (live) paintNowCommitLater(mutate);
-		else applyToSelection(mutate);
+		if (live) paintNowCommitLater(texts, mutate);
+		else restyle(texts, mutate);
 	};
 
 	return (
diff --git a/B07_DesignDetail/openwebcad/src/helpers/selection-style.ts b/B07_DesignDetail/openwebcad/src/helpers/selection-style.ts
new file mode 100644
index 000000000..4ee9b4c82
--- /dev/null
+++ b/B07_DesignDetail/openwebcad/src/helpers/selection-style.ts
@@ -0,0 +1,107 @@
+/**
+ * 고른 것의 선 특성(색 · 선 두께 · 선종류) 읽기 · 바꾸기 한 벌 (488 · 리본 특성 · 특성 판 · 특성 명령).
+ *
+ * 읽기 = 고른 것의 선 잎(폴리선 → 자식 선 · 글 뺌)이 모두 같으면 그 값 · 다르거나 목록 밖이면 빈 값 ·
+ * 고른 선이 없으면 그리기 기본값.
+ * 바꾸기 = id 그대로 사본으로 갈아 끼움(폴리선 자식까지) — 되돌리기 한 칸 · Ctrl+Z 한 번에 옛 값.
+ */
+import { type Entity, EntityName } from '../entities/Entity';
+import type { PolyLineEntity } from '../entities/PolyLineEntity';
+import {
+	getActiveLineColor,
+	getActiveLineDash,
+	getActiveLineWidth,
+	getEntities,
+	getSelectedEntities,
+	notifyWindow,
+	setEntities,
+} from '../state';
+import { HtmlEvent } from '../App.types';
+import { cloneKeepingLook } from '../tools/move-tool.helpers';
+
+export const LINE_TYPES: { value: string; label: string; dash: number[] | undefined }[] = [
+	{ value: 'solid', label: '실선', dash: undefined },
+	{ value: 'dashed', label: '파선', dash: [10, 5] },
+	{ value: 'dashdot', label: '1점쇄선', dash: [12, 4, 2, 4] },
+	{ value: 'dotted', label: '점선', dash: [2, 4] },
+];
+
+export const LINE_WIDTHS = [1, 2, 3, 4, 5];
+
+/** 점선 → 목록 값 · `[]` · 없음 = 실선 · 목록 밖 = 빈 값 */
+export const dashToLineType = (dash: number[] | undefined): string =>
+	dash?.length
+		? (LINE_TYPES.find((type) => JSON.stringify(type.dash) === JSON.stringify(dash))?.value ?? '')
+		: 'solid';
+
+/** 선 메뉴가 보는 것 — 글 뺌(글 색은 문자 스타일 칸) */
+export const styleTargets = (entities: Entity[]): Entity[] =>
+	entities.filter((entity) => entity.getType() !== EntityName.Text);
+
+/** 그림에 쓰는 잎 — 폴리선은 자식 선이 제 색 · 두께로 그림 */
+const leaves = (entity: Entity): Entity[] =>
+	entity.getType() === EntityName.PolyLine ? (entity as PolyLineEntity).getEntities() : [entity];
+
+/** 모두 같으면 그 값 · 다르거나 없으면 `''`(빈 칸) */
+export function commonValue(entities: Entity[], read: (entity: Entity) => string): string {
+	const values = new Set(entities.flatMap(leaves).map(read));
+	return values.size === 1 ? [...values][0] : '';
+}
+
+export interface LineStyleView {
+	color: string;
+	width: string;
+	lineType: string;
+}
+
+/** 리본 · 특성 판이 보일 값 — 고른 선 있으면 그 값(다르면 `''`) · 없으면 그리기 기본값 */
+export function selectionLineStyle(): LineStyleView {
+	const targets = styleTargets(getSelectedEntities());
+	if (!targets.length) {
+		return {
+			color: getActiveLineColor(),
+			width: String(getActiveLineWidth()),
+			lineType: dashToLineType(getActiveLineDash()),
+		};
+	}
+	const width = commonValue(targets, (entity) => String(entity.lineWidth));
+	return {
+		color: commonValue(targets, (entity) => entity.lineColor.toLowerCase()),
+		width: LINE_WIDTHS.map(String).includes(width) ? width : '',
+		lineType: commonValue(targets, (entity) => dashToLineType(entity.lineDash)),
+	};
+}
+
+/** 사본에 바꿈 — 폴리선은 자식까지 */
+function applyDeep(entity: Entity, change: (entity: Entity) => void): void {
+	change(entity);
+	if (entity.getType() === EntityName.PolyLine) {
+		for (const child of (entity as PolyLineEntity).getEntities()) change(child);
+	}
+}
+
+/**
+ * 바꾼 사본(id 그대로)을 제자리에 끼움 · `track` = 되돌리기 한 칸.
+ * 돌려준 사본은 이어서 칠할 수 있음(`repaint` · 색 끌기).
+ */
+export function restyle(targets: Entity[], change: (entity: Entity) => void, track = true): Entity[] {
+	if (!targets.length) return [];
+	const copies = targets.map((entity) => {
+		const copy = cloneKeepingLook(entity, true);
+		applyDeep(copy, change);
+		return copy;
+	});
+	const byId = new Map(copies.map((copy) => [copy.id, copy]));
+	setEntities(
+		getEntities().map((entity) => byId.get(entity.id) ?? entity),
+		track
+	);
+	notifyWindow(HtmlEvent.UPDATE_STATE);
+	return copies;
+}
+
+/** 이미 끼운 사본을 다시 칠함(화면만 · 되돌리기 없음) */
+export function repaint(copies: Entity[], change: (entity: Entity) => void): void {
+	for (const copy of copies) applyDeep(copy, change);
+	setEntities([...getEntities()], false);
+}
diff --git a/B07_DesignDetail/openwebcad/src/tools/modify/property-tools.ts b/B07_DesignDetail/openwebcad/src/tools/modify/property-tools.ts
index 304299cbf..433764edc 100644
--- a/B07_DesignDetail/openwebcad/src/tools/modify/property-tools.ts
+++ b/B07_DesignDetail/openwebcad/src/tools/modify/property-tools.ts
@@ -15,6 +15,7 @@ import {
 import { Tool } from '../../tools';
 import { createSequenceTool } from '../factories/sequence-tool';
 import { findDuplicateEntities, reverseEntity } from './modify.helpers';
+import { restyle } from '../../helpers/selection-style';
 
 export const matchPropToolStateMachine = createSequenceTool({
 	tool: Tool.MATCHPROP,
@@ -25,12 +26,12 @@ export const matchPropToolStateMachine = createSequenceTool({
 	],
 	commit: (input) => {
 		const source = input.entity(0);
-		const target = input.entity(1);
-		target.lineColor = source.lineColor;
-		target.lineWidth = source.lineWidth;
-		target.lineDash = source.lineDash;
-		target.layerId = source.layerId;
-		setEntities([...getEntities()], true);
+		restyle([input.entity(1)], (target) => {
+			target.lineColor = source.lineColor;
+			target.lineWidth = source.lineWidth;
+			target.lineDash = source.lineDash ? [...source.lineDash] : undefined;
+			target.layerId = source.layerId;
+		});
 	},
 });
 
@@ -67,16 +68,15 @@ export const setByLayerToolStateMachine = createSequenceTool({
 	helpers: false,
 	steps: [{ kind: 'selection', instructions: 'ByLayer로 되돌릴 객체를 선택한 뒤 ENTER.' }],
 	commit: (input) => {
-		let applied = 0;
-		for (const entity of input.entities(0)) {
+		const targets = input.entities(0).filter((entity) => getLayerById(entity.layerId));
+		restyle(targets, (entity) => {
 			const layer = getLayerById(entity.layerId);
-			if (!layer) continue;
+			if (!layer) return;
 			if (layer.color) entity.lineColor = layer.color;
 			if (layer.lineWidth) entity.lineWidth = layer.lineWidth;
 			entity.lineDash = layer.lineDash ? [...layer.lineDash] : undefined;
-			applied += 1;
-		}
-		setEntities([...getEntities()], true);
+		});
+		const applied = targets.length;
 		setSelectedEntityIds([]);
 		toast.success(`${applied}개 객체를 레이어 특성으로 되돌렸습니다.`);
 	},
diff --git a/B07_DesignDetail/openwebcad/src/tools/utility/layer-tools.ts b/B07_DesignDetail/openwebcad/src/tools/utility/layer-tools.ts
index 2e5c35bf4..9d54f5c6c 100644
--- a/B07_DesignDetail/openwebcad/src/tools/utility/layer-tools.ts
+++ b/B07_DesignDetail/openwebcad/src/tools/utility/layer-tools.ts
@@ -1,5 +1,6 @@
 /** 도면층 명령 (조사표 3절 도면층 패널) */
 import { toast } from 'react-toastify';
+import { restyle } from '../../helpers/selection-style';
 import type { Layer } from '../../App.types';
 import { openInspector } from '../../components/ui-state';
 import type { Entity } from '../../entities/Entity';
@@ -186,10 +187,9 @@ export const layerMatchToolStateMachine = createSequenceTool({
 	],
 	commit: (input) => {
 		const layerId = input.entity(1).layerId;
-		for (const entity of input.entities(0)) {
+		restyle(input.entities(0), (entity) => {
 			entity.layerId = layerId;
-		}
-		setEntities([...getEntities()], true);
+		});
 		setSelectedEntityIds([]);
 		toast.success(`${input.entities(0).length}개 객체를 ${layerNameOf(layerId)}(으)로 옮겼습니다.`);
 	},
@@ -201,10 +201,9 @@ export const layerToCurrentToolStateMachine = createSequenceTool({
 	steps: [{ kind: 'selection', instructions: '현재 레이어로 옮길 객체를 선택한 뒤 ENTER.' }],
 	commit: (input) => {
 		const layerId = getActiveLayerId();
-		for (const entity of input.entities(0)) {
+		restyle(input.entities(0), (entity) => {
 			entity.layerId = layerId;
-		}
-		setEntities([...getEntities()], true);
+		});
 		setSelectedEntityIds([]);
 		toast.success(`${input.entities(0).length}개 객체를 현재 레이어로 옮겼습니다.`);
 	},
diff --git a/B07_DesignDetail/openwebcad/src/tools/utility/property-tools.ts b/B07_DesignDetail/openwebcad/src/tools/utility/property-tools.ts
index 9b4101eda..3466e7a10 100644
--- a/B07_DesignDetail/openwebcad/src/tools/utility/property-tools.ts
+++ b/B07_DesignDetail/openwebcad/src/tools/utility/property-tools.ts
@@ -5,7 +5,8 @@ import {
 	setQuickPropertiesVisible,
 	isQuickPropertiesVisible,
 } from '../../components/ui-state';
-import { getEntities, setEntities, setSelectedEntityIds } from '../../state';
+import { restyle } from '../../helpers/selection-style';
+import { setSelectedEntityIds } from '../../state';
 import { Tool } from '../../tools';
 import { createSequenceTool } from '../factories/sequence-tool';
 
@@ -60,10 +61,9 @@ export const colorToolStateMachine = createSequenceTool({
 			toast.warn('#rrggbb 형식이나 색 이름을 입력하십시오.');
 			return;
 		}
-		for (const entity of input.entities(0)) {
+		restyle(input.entities(0), (entity) => {
 			entity.lineColor = color;
-		}
-		setEntities([...getEntities()], true);
+		});
 		setSelectedEntityIds([]);
 		toast.success(`색상 ${color}`);
 	},
@@ -87,10 +87,9 @@ export const lineTypeToolStateMachine = createSequenceTool({
 			return;
 		}
 		const dash = LINE_DASHES[key] ?? LINE_DASHES[key.toUpperCase()];
-		for (const entity of input.entities(0)) {
+		restyle(input.entities(0), (entity) => {
 			entity.lineDash = dash ? [...dash] : undefined;
-		}
-		setEntities([...getEntities()], true);
+		});
 		setSelectedEntityIds([]);
 		toast.success(`선종류 ${key}`);
 	},
@@ -105,10 +104,9 @@ export const lineWeightToolStateMachine = createSequenceTool({
 	],
 	commit: (input) => {
 		const width = Math.max(1, Math.round(input.number(1)));
-		for (const entity of input.entities(0)) {
+		restyle(input.entities(0), (entity) => {
 			entity.lineWidth = width;
-		}
-		setEntities([...getEntities()], true);
+		});
 		setSelectedEntityIds([]);
 		toast.success(`선 두께 ${width}px`);
 	},
@@ -123,10 +121,9 @@ export const transparencyToolStateMachine = createSequenceTool({
 	],
 	commit: (input) => {
 		const percent = Math.min(90, Math.max(0, input.number(1)));
-		for (const entity of input.entities(0)) {
+		restyle(input.entities(0), (entity) => {
 			entity.opacity = 1 - percent / 100;
-		}
-		setEntities([...getEntities()], true);
+		});
 		setSelectedEntityIds([]);
 		toast.success(`투명도 ${percent}%를 적용했습니다.`);
 	},
diff --git a/resources/tester/cad/selection-style.test.ts b/resources/tester/cad/selection-style.test.ts
new file mode 100644
index 000000000..577cc6d65
--- /dev/null
+++ b/resources/tester/cad/selection-style.test.ts
@@ -0,0 +1,121 @@
+/**
+ * 488-2 — 선 특성 메뉴 = 고른 것의 값(다르면 빈 칸) · 바꾸면 고른 것만 · 폴리선 자식까지 · Ctrl+Z 한 번에 옛 값.
+ * 짝: `src/helpers/selection-style.ts`(리본 특성 · 특성 판 · COLOR · LWEIGHT 등 명령 같이 씀).
+ * 실행: cd B07_DesignDetail/openwebcad && npx vitest run --dir ../../resources/tester/cad selection-style
+ */
+// 앱과 같은 flatten 사본(시험 쪽 사본 점은 앱 Segment 가 못 받음)
+import { Point } from "../../../B07_DesignDetail/openwebcad/node_modules/@flatten-js/core";
+import { beforeEach, describe, expect, it } from "vitest";
+import type { Entity } from "../../../B07_DesignDetail/openwebcad/src/entities/Entity";
+import { LineEntity } from "../../../B07_DesignDetail/openwebcad/src/entities/LineEntity";
+import { PolyLineEntity } from "../../../B07_DesignDetail/openwebcad/src/entities/PolyLineEntity";
+import { TextEntity } from "../../../B07_DesignDetail/openwebcad/src/entities/TextEntity";
+import {
+  dashToLineType,
+  restyle,
+  selectionLineStyle,
+  styleTargets,
+} from "../../../B07_DesignDetail/openwebcad/src/helpers/selection-style";
+import {
+  getActiveLineWidth,
+  getEntities,
+  getSelectedEntities,
+  resetUndoBaseline,
+  setActiveLineWidth,
+  setEntities,
+  setLayers,
+  setSelectedEntityIds,
+  undo,
+} from "../../../B07_DesignDetail/openwebcad/src/state";
+
+const line = (color: string, width = 1, dash?: number[]) => {
+  const entity = new LineEntity("L", new Point(0, 0), new Point(10, 0));
+  entity.lineColor = color;
+  entity.lineWidth = width;
+  entity.lineDash = dash;
+  return entity;
+};
+/** 엔진 꼴 — 부모 값과 자식 선 값이 따로 */
+const poly = (childColor: string) => {
+  const kids = [line(childColor), line(childColor)];
+  const entity = new PolyLineEntity("L", kids);
+  entity.lineColor = "#ffffff";
+  return entity;
+};
+const leafWidths = (entity: Entity) =>
+  entity instanceof PolyLineEntity ? entity.getEntities().map((kid) => kid.lineWidth) : [entity.lineWidth];
+const byId = (id: string) => getEntities().find((entity) => entity.id === id) as Entity;
+
+/** 실은 도면 = 선 a(빨강) · 폴리선 b(자식 파랑) · 글 · 방금 그린 선 d */
+let a: LineEntity;
+let b: PolyLineEntity;
+let d: LineEntity;
+beforeEach(() => {
+  setLayers([{ id: "L", name: "L", isVisible: true, isLocked: false }]);
+  a = line("#ff0000");
+  b = poly("#0000ff");
+  const text = new TextEntity("L", "글", new Point(0, 0));
+  setEntities([a, b, text], false);
+  resetUndoBaseline();
+  d = line("#00ff00");
+  setEntities([...getEntities(), d], true); // 방금 그린 선
+  setSelectedEntityIds([a.id, b.id, text.id]);
+  setActiveLineWidth(1);
+});
+
+describe("selectionLineStyle", () => {
+  it("다른 색 = 빈 칸 · 같은 두께 · 선종류 = 그 값 · 글은 안 봄", () => {
+    expect(styleTargets(getSelectedEntities())).toHaveLength(2);
+    expect(selectionLineStyle()).toEqual({ color: "", width: "1", lineType: "solid" });
+  });
+
+  it("폴리선은 자식 값을 봄 · 목록 밖 두께 · 점선 = 빈 칸", () => {
+    setSelectedEntityIds([b.id]);
+    expect(selectionLineStyle().color).toBe("#0000ff");
+    a.lineWidth = 0.5;
+    a.lineDash = [6, 4]; // 엔진 점선(목록 밖)
+    setSelectedEntityIds([a.id]);
+    expect(selectionLineStyle()).toEqual({ color: "#ff0000", width: "", lineType: "" });
+    expect([dashToLineType([]), dashToLineType(undefined), dashToLineType([10, 5])]).toEqual([
+      "solid",
+      "solid",
+      "dashed",
+    ]);
+  });
+
+  it("고른 선 없으면 그리기 기본값", () => {
+    setSelectedEntityIds([]);
+    setActiveLineWidth(4);
+    expect(selectionLineStyle().width).toBe("4");
+  });
+});
+
+describe("restyle", () => {
+  it("고른 것만 · 폴리선 자식까지 · 고름 · id 그대로 · 기본값 그대로", () => {
+    restyle(styleTargets(getSelectedEntities()), (entity) => {
+      entity.lineWidth = 3;
+    });
+    expect(leafWidths(byId(a.id))).toEqual([3]);
+    expect(leafWidths(byId(b.id))).toEqual([3, 3]);
+    expect(byId(d.id).lineWidth).toBe(1);
+    expect(getSelectedEntities()).toHaveLength(3);
+    expect(selectionLineStyle().width).toBe("3");
+    expect(getActiveLineWidth()).toBe(1);
+  });
+
+  it("Ctrl+Z 한 번 = 옛 값 · 방금 그린 선 남음", () => {
+    restyle(styleTargets(getSelectedEntities()), (entity) => {
+      entity.lineWidth = 3;
+    });
+    undo();
+    expect(leafWidths(byId(a.id))).toEqual([1]);
+    expect(leafWidths(byId(b.id))).toEqual([1, 1]);
+    expect(getEntities().map((entity) => entity.id)).toContain(d.id);
+  });
+
+  it("고른 것 없으면 아무것도 안 바뀜 · 되돌리기 칸 안 쌓임", () => {
+    expect(restyle([], () => {})).toEqual([]);
+    undo();
+    expect(getEntities().map((entity) => entity.id)).not.toContain(d.id); // 한 칸 전 = 그리기 전
+  });
+});