diff --git a/src/common/abtesting.ts b/src/common/abtesting.ts
index 0999b70a..589f6f84 100644
--- a/src/common/abtesting.ts
+++ b/src/common/abtesting.ts
@@ -15,8 +15,8 @@ export const validateABTestingVariant = (
 		: null;
 };
 
-export const getAorBRandom = (): AB_TETSTING_VARIANT => {
-	return Math.random() < 0.5
+export const getAorBRandom = (rate: number): AB_TETSTING_VARIANT => {
+	return Math.random() < rate
 		? AB_TESTING_VARIANTS.ONLY_SONNET
 		: AB_TESTING_VARIANTS.WITH_HAIKU;
 };
diff --git a/src/pages/_app.tsx b/src/pages/_app.tsx
index af7be636..43ca5864 100644
--- a/src/pages/_app.tsx
+++ b/src/pages/_app.tsx
@@ -16,7 +16,11 @@ import { gtagEvent } from "@/common/util/gtag";
 import { keysOverride } from "@/components/headMeta";
 import { ConfirmModal } from "@/components/confirmModal";
 import { Toast } from "@/components/toast";
-import { AB_TESTING_COOKIE_NAME, getAorBRandom } from "@/common/abtesting";
+import {
+	AB_TESTING_COOKIE_NAME,
+	getAorBRandom,
+	validateABTestingVariant,
+} from "@/common/abtesting";
 
 export default function App({ Component, pageProps }: AppProps) {
 	const queryClient = useMemo(() => new QueryClient(), []);
@@ -46,13 +50,21 @@ export default function App({ Component, pageProps }: AppProps) {
 	}, [router]);
 
 	useEffect(() => {
+		if (!process.env.NEXT_PUBLIC_AB_TEST_RATE) {
+			return;
+		}
+		const rate = Number(process.env.NEXT_PUBLIC_AB_TEST_RATE);
+		if (rate < 0 || rate > 1 || isNaN(rate)) {
+			console.error("NEXT_PUBLIC_AB_TEST_RATE must be between 0 and 1.");
+			return;
+		}
 		//ABテストのためのクッキーを付与
-		process.env.NEXT_PUBLIC_ENABLE_AB_TEST &&
-			import("js-cookie").then((jsCookie) => {
-				if (!jsCookie.default.get(AB_TESTING_COOKIE_NAME)) {
-					jsCookie.default.set(AB_TESTING_COOKIE_NAME, getAorBRandom());
-				}
-			});
+		import("js-cookie").then((jsCookie) => {
+			const cookieValue = jsCookie.default.get(AB_TESTING_COOKIE_NAME);
+			if (!cookieValue || !validateABTestingVariant(cookieValue)) {
+				jsCookie.default.set(AB_TESTING_COOKIE_NAME, getAorBRandom(rate));
+			}
+		});
 	}, []);
 
 	return (