diff --git a/A00_Common/main.ts b/A00_Common/main.ts
index 192dc84f..3ffa2037 100644
--- a/A00_Common/main.ts
+++ b/A00_Common/main.ts
@@ -8,6 +8,7 @@
  * - hashchange 1회 구독: 셸 chrome 갱신 + 현재 라우트 렌더
  * ========================================================================== */
 
+import "./random_uuid_polyfill";
 import "@ui/ui_template_theme.css";
 import { injectBaseStyles } from "@ui/ui_template_elements";
 import { ROUTES, type RoutePath } from "@config/config_frontend";
diff --git a/A00_Common/random_uuid_polyfill.ts b/A00_Common/random_uuid_polyfill.ts
new file mode 100644
index 00000000..edc40154
--- /dev/null
+++ b/A00_Common/random_uuid_polyfill.ts
@@ -0,0 +1,16 @@
+/**
+ * http + IP 주소(예: Tailscale)는 보안 문맥이 아니라 `crypto.randomUUID` 가 없음.
+ * getRandomValues(보안 문맥 아니어도 됨)로 v4 UUID 를 채움 · 이미 있으면 그대로.
+ * `main.ts` 가 맨 먼저 부름. CAD 짝 = `B07_DesignDetail/openwebcad/src/random-uuid-polyfill.ts`.
+ */
+if (typeof crypto !== "undefined" && typeof crypto.randomUUID !== "function") {
+  crypto.randomUUID = () => {
+    const bytes = crypto.getRandomValues(new Uint8Array(16));
+    bytes[6] = (bytes[6] & 0x0f) | 0x40;
+    bytes[8] = (bytes[8] & 0x3f) | 0x80;
+    const hex = Array.from(bytes, (byte) => byte.toString(16).padStart(2, "0")).join("");
+    return `${hex.slice(0, 8)}-${hex.slice(8, 12)}-${hex.slice(12, 16)}-${hex.slice(16, 20)}-${hex.slice(20)}` as `${string}-${string}-${string}-${string}-${string}`;
+  };
+}
+
+export {};
diff --git a/B07_DesignDetail/openwebcad/src/main.tsx b/B07_DesignDetail/openwebcad/src/main.tsx
index bc8f2dab..795a65e8 100644
--- a/B07_DesignDetail/openwebcad/src/main.tsx
+++ b/B07_DesignDetail/openwebcad/src/main.tsx
@@ -1,3 +1,4 @@
+import './random-uuid-polyfill';
 import { Point } from '@flatten-js/core';
 import React from 'react';
 import ReactDOM from 'react-dom/client';
diff --git a/B07_DesignDetail/openwebcad/src/random-uuid-polyfill.ts b/B07_DesignDetail/openwebcad/src/random-uuid-polyfill.ts
new file mode 100644
index 00000000..ea537f5c
--- /dev/null
+++ b/B07_DesignDetail/openwebcad/src/random-uuid-polyfill.ts
@@ -0,0 +1,16 @@
+/**
+ * http + IP 주소(예: Tailscale)는 보안 문맥이 아니라 `crypto.randomUUID` 가 없음 — 개체 만들기에서 죽음.
+ * getRandomValues(보안 문맥 아니어도 됨)로 v4 UUID 를 채움 · 이미 있으면 그대로.
+ * `main.tsx` 가 맨 먼저 부름. 앱 본체 짝 = `A00_Common/random_uuid_polyfill.ts`.
+ */
+if (typeof crypto !== 'undefined' && typeof crypto.randomUUID !== 'function') {
+	crypto.randomUUID = () => {
+		const bytes = crypto.getRandomValues(new Uint8Array(16));
+		bytes[6] = (bytes[6] & 0x0f) | 0x40;
+		bytes[8] = (bytes[8] & 0x3f) | 0x80;
+		const hex = Array.from(bytes, (byte) => byte.toString(16).padStart(2, '0')).join('');
+		return `${hex.slice(0, 8)}-${hex.slice(8, 12)}-${hex.slice(12, 16)}-${hex.slice(16, 20)}-${hex.slice(20)}` as `${string}-${string}-${string}-${string}-${string}`;
+	};
+}
+
+export {};
diff --git a/resources/tester/cad/random-uuid-polyfill.test.ts b/resources/tester/cad/random-uuid-polyfill.test.ts
new file mode 100644
index 00000000..9c35a3da
--- /dev/null
+++ b/resources/tester/cad/random-uuid-polyfill.test.ts
@@ -0,0 +1,26 @@
+/**
+ * http + IP(보안 문맥 아님)에서 비는 crypto.randomUUID 대체 검증 — CAD · 앱 본체 두 벌.
+ * 실행: node --experimental-strip-types resources/tester/cad/random-uuid-polyfill.test.ts
+ */
+import assert from 'node:assert/strict';
+
+const V4 = /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/;
+const native = crypto.randomUUID;
+
+for (const path of [
+	'../../../B07_DesignDetail/openwebcad/src/random-uuid-polyfill.ts',
+	'../../../A00_Common/random_uuid_polyfill.ts',
+]) {
+	// biome-ignore lint: 시험 — 보안 문맥 아닌 브라우저처럼 비움
+	(crypto as any).randomUUID = undefined;
+	await import(`${path}?${Math.random()}`);
+	const ids = Array.from({ length: 200 }, () => crypto.randomUUID());
+	assert.ok(ids.every((id) => V4.test(id)), `${path}: v4 모양`);
+	assert.equal(new Set(ids).size, ids.length, `${path}: 안 겹침`);
+}
+
+// 이미 있으면 그대로
+crypto.randomUUID = native;
+await import(`../../../A00_Common/random_uuid_polyfill.ts?${Math.random()}`);
+assert.equal(crypto.randomUUID, native, '원래 것 유지');
+console.log('random-uuid 대체 시험 통과');