diff --git a/src/data/storage/__tests__/storage_migration.test.ts b/src/data/storage/__tests__/storage_migration.test.ts
new file mode 100644
index 00000000..fcc357cc
--- /dev/null
+++ b/src/data/storage/__tests__/storage_migration.test.ts
@@ -0,0 +1,73 @@
+import { beforeEach, describe, expect, it } from "vitest";
+import { createStorage } from "unstorage";
+import memoryDriver from "unstorage/drivers/memory";
+
+import { StorageKeys } from "@/data/storage/storage_keys";
+import { runStorageMigrations } from "@/data/storage/storage_migration";
+import { SpAsyncUtil } from "@/utils";
+
+describe("runStorageMigrations", () => {
+  beforeEach(() => {
+    SpAsyncUtil.setStorage(createStorage({ driver: memoryDriver() }));
+  });
+
+  it("moves legacy facebook id into asid", async () => {
+    await SpAsyncUtil.setString("facebook_id", "asid-legacy");
+
+    const result = await runStorageMigrations();
+
+    expect(result.success).toBe(true);
+    await expectString(StorageKeys.asid, "asid-legacy");
+    await expectString("facebook_id", null);
+  });
+
+  it("does not overwrite existing asid", async () => {
+    await SpAsyncUtil.setString(StorageKeys.asid, "asid-current");
+    await SpAsyncUtil.setString("facebook_id", "asid-legacy");
+
+    const result = await runStorageMigrations();
+
+    expect(result.success).toBe(true);
+    await expectString(StorageKeys.asid, "asid-current");
+    await expectString("facebook_id", null);
+  });
+
+  it("migrates legacy pwa dialog markers and removes old keys", async () => {
+    await SpAsyncUtil.setString("last_pwa_dialog_shown", "2026-01-01");
+
+    const result = await runStorageMigrations();
+
+    expect(result.success).toBe(true);
+    const shown = await SpAsyncUtil.getBool(StorageKeys.pwaDialogShown);
+    expect(shown).toEqual({ success: true, data: true });
+    await expectString("last_pwa_dialog_shown", null);
+  });
+
+  it("records migration version and skips repeated migrations", async () => {
+    await SpAsyncUtil.setString("facebook_id", "asid-legacy");
+    await expectSuccess(runStorageMigrations());
+    await SpAsyncUtil.setString("facebook_id", "asid-new-legacy");
+
+    await expectSuccess(runStorageMigrations());
+
+    await expectString(StorageKeys.asid, "asid-legacy");
+    await expectString("facebook_id", "asid-new-legacy");
+    const version = await SpAsyncUtil.getInt(StorageKeys.storageMigrationVersion);
+    expect(version).toEqual({ success: true, data: 1 });
+  });
+});
+
+async function expectString(
+  key: string,
+  expected: string | null,
+): Promise<void> {
+  const value = await SpAsyncUtil.getString(key);
+  expect(value).toEqual({ success: true, data: expected });
+}
+
+async function expectSuccess(
+  resultPromise: Promise<{ success: boolean }>,
+): Promise<void> {
+  const result = await resultPromise;
+  expect(result.success).toBe(true);
+}
diff --git a/src/data/storage/app/app_storage.ts b/src/data/storage/app/app_storage.ts
index d953e41d..6bbea25c 100644
--- a/src/data/storage/app/app_storage.ts
+++ b/src/data/storage/app/app_storage.ts
@@ -15,11 +15,6 @@
 import { Result, type Result as ResultT, SpAsyncUtil } from "@/utils";
 import { StorageKeys } from "../storage_keys";
 
-const LEGACY_PWA_DIALOG_SHOWN_KEYS = [
-  "cozsweet:lastPwaDialogShown",
-  "last_pwa_dialog_shown",
-];
-
 export class AppStorage {
   // ---- PWA install dialog ----
 
@@ -27,13 +22,6 @@ export class AppStorage {
     const shownResult = await SpAsyncUtil.getBool(StorageKeys.pwaDialogShown);
     if (!shownResult.success) return shownResult;
     if (shownResult.data === true) return Result.ok(false);
-
-    for (const key of LEGACY_PWA_DIALOG_SHOWN_KEYS) {
-      const legacyResult = await SpAsyncUtil.getString(key);
-      if (!legacyResult.success) return legacyResult;
-      if (legacyResult.data !== null) return Result.ok(false);
-    }
-
     return Result.ok(true);
   }
 
diff --git a/src/data/storage/auth/auth_storage.ts b/src/data/storage/auth/auth_storage.ts
index 4549efa8..e9fc724b 100644
--- a/src/data/storage/auth/auth_storage.ts
+++ b/src/data/storage/auth/auth_storage.ts
@@ -92,29 +92,23 @@ export class AuthStorage implements IAuthStorage {
   // ---- ASID / PSID ----
 
   async getAsid(): Promise<ResultT<string | null>> {
-    return getStringWithLegacyFallback(
-      StorageKeys.asid,
-      StorageKeys.legacyFacebookId,
-    );
+    return SpAsyncUtil.getString(StorageKeys.asid);
   }
   setAsid(id: string): Promise<ResultT<void>> {
     return SpAsyncUtil.setString(StorageKeys.asid, id);
   }
   clearAsid(): Promise<ResultT<void>> {
-    return removeKeys(StorageKeys.asid, StorageKeys.legacyFacebookId);
+    return SpAsyncUtil.remove(StorageKeys.asid);
   }
 
   async getPsid(): Promise<ResultT<string | null>> {
-    return getStringWithLegacyFallback(
-      StorageKeys.psid,
-      StorageKeys.legacyFacebookAppId,
-    );
+    return SpAsyncUtil.getString(StorageKeys.psid);
   }
   setPsid(id: string): Promise<ResultT<void>> {
     return SpAsyncUtil.setString(StorageKeys.psid, id);
   }
   clearPsid(): Promise<ResultT<void>> {
-    return removeKeys(StorageKeys.psid, StorageKeys.legacyFacebookAppId);
+    return SpAsyncUtil.remove(StorageKeys.psid);
   }
 
   // ---- bulk clear ----
@@ -146,24 +140,6 @@ export class AuthStorage implements IAuthStorage {
   }
 }
 
-async function getStringWithLegacyFallback(
-  key: string,
-  legacyKey: string,
-): Promise<ResultT<string | null>> {
-  const value = await SpAsyncUtil.getString(key);
-  if (!value.success) return value;
-  if (value.data !== null && value.data.length > 0) return value;
-  return SpAsyncUtil.getString(legacyKey);
-}
-
-async function removeKeys(...keys: string[]): Promise<ResultT<void>> {
-  for (const key of keys) {
-    const result = await SpAsyncUtil.remove(key);
-    if (!result.success) return result;
-  }
-  return Result.ok(undefined);
-}
-
 function isLoginStatus(value: string): value is LoginStatusT {
   return Object.values(LoginStatus).includes(value as LoginStatusT);
 }
diff --git a/src/data/storage/index.ts b/src/data/storage/index.ts
index b90d537e..d669a7b7 100644
--- a/src/data/storage/index.ts
+++ b/src/data/storage/index.ts
@@ -7,6 +7,7 @@
  */
 export * from "@/utils/result";
 export * from "./storage_keys";
+export * from "./storage_migration";
 export * from "./app/app_storage";
 // NOTE: top-level `auth_storage.ts` is intentionally not re-exported here —
 // it conflicts with `auth/auth_storage.ts` (both define `AuthStorage`).
diff --git a/src/data/storage/storage_keys.ts b/src/data/storage/storage_keys.ts
index f38566d7..0b331a20 100644
--- a/src/data/storage/storage_keys.ts
+++ b/src/data/storage/storage_keys.ts
@@ -15,8 +15,7 @@ export const StorageKeys = {
   refreshToken: "refresh_token",
   asid: "asid",
   psid: "psid",
-  legacyFacebookId: "facebook_id",
-  legacyFacebookAppId: "facebook_app_id",
+  storageMigrationVersion: "storage_migration_version",
 
   // user
   user: "user",
diff --git a/src/data/storage/storage_migration.ts b/src/data/storage/storage_migration.ts
new file mode 100644
index 00000000..c0a19cb4
--- /dev/null
+++ b/src/data/storage/storage_migration.ts
@@ -0,0 +1,129 @@
+"use client";
+
+import { Result, type Result as ResultT, SpAsyncUtil } from "@/utils";
+
+import { StorageKeys } from "./storage_keys";
+
+const CURRENT_STORAGE_MIGRATION_VERSION = 1;
+
+const LEGACY_FACEBOOK_ID_KEY = "facebook_id";
+const LEGACY_PWA_DIALOG_SHOWN_KEYS = [
+  "last_pwa_dialog_shown",
+  "cozsweet:lastPwaDialogShown",
+];
+
+/**
+ * Runs app startup migrations for persistent key-value storage.
+ *
+ * Migrations are intentionally idempotent: copying only fills missing new keys,
+ * and legacy keys are removed after each attempt.
+ */
+export async function runStorageMigrations(): Promise<ResultT<void>> {
+  const versionResult = await SpAsyncUtil.getInt(
+    StorageKeys.storageMigrationVersion,
+  );
+  if (!versionResult.success) return versionResult;
+  if ((versionResult.data ?? 0) >= CURRENT_STORAGE_MIGRATION_VERSION) {
+    return Result.ok(undefined);
+  }
+
+  const migrationResult = await migrateToV1();
+  if (!migrationResult.success) return migrationResult;
+
+  return SpAsyncUtil.setInt(
+    StorageKeys.storageMigrationVersion,
+    CURRENT_STORAGE_MIGRATION_VERSION,
+  );
+}
+
+async function migrateToV1(): Promise<ResultT<void>> {
+  const asidResult = await migrateStringKey({
+    legacyKey: LEGACY_FACEBOOK_ID_KEY,
+    newKey: StorageKeys.asid,
+  });
+  if (!asidResult.success) return asidResult;
+
+  return migratePwaDialogShown();
+}
+
+async function migrateStringKey(input: {
+  legacyKey: string;
+  newKey: string;
+}): Promise<ResultT<void>> {
+  const current = await SpAsyncUtil.getString(input.newKey);
+  if (!current.success) return current;
+
+  const legacy = await readLegacyString(input.legacyKey);
+  if (!legacy.success) return legacy;
+
+  if (!current.data && legacy.data) {
+    const writeResult = await SpAsyncUtil.setString(input.newKey, legacy.data);
+    if (!writeResult.success) return writeResult;
+  }
+
+  return removeLegacyKey(input.legacyKey);
+}
+
+async function migratePwaDialogShown(): Promise<ResultT<void>> {
+  const current = await SpAsyncUtil.getBool(StorageKeys.pwaDialogShown);
+  if (!current.success) return current;
+
+  let wasShown = current.data === true;
+  for (const legacyKey of LEGACY_PWA_DIALOG_SHOWN_KEYS) {
+    const legacy = await readLegacyString(legacyKey);
+    if (!legacy.success) return legacy;
+    wasShown = wasShown || legacy.data !== null;
+  }
+
+  if (wasShown && current.data !== true) {
+    const writeResult = await SpAsyncUtil.setBool(
+      StorageKeys.pwaDialogShown,
+      true,
+    );
+    if (!writeResult.success) return writeResult;
+  }
+
+  for (const legacyKey of LEGACY_PWA_DIALOG_SHOWN_KEYS) {
+    const removeResult = await removeLegacyKey(legacyKey);
+    if (!removeResult.success) return removeResult;
+  }
+
+  return Result.ok(undefined);
+}
+
+async function readLegacyString(key: string): Promise<ResultT<string | null>> {
+  const storageResult = await SpAsyncUtil.getString(key);
+  if (!storageResult.success) return storageResult;
+  if (storageResult.data) return storageResult;
+
+  const browserValue = readBrowserLocalStorage(key);
+  if (browserValue !== null && browserValue.length > 0) {
+    return Result.ok(browserValue);
+  }
+  return Result.ok(null);
+}
+
+async function removeLegacyKey(key: string): Promise<ResultT<void>> {
+  const removeResult = await SpAsyncUtil.remove(key);
+  if (!removeResult.success) return removeResult;
+  removeBrowserLocalStorage(key);
+  return Result.ok(undefined);
+}
+
+function readBrowserLocalStorage(key: string): string | null {
+  if (typeof window === "undefined") return null;
+  try {
+    return window.localStorage.getItem(key);
+  } catch {
+    return null;
+  }
+}
+
+function removeBrowserLocalStorage(key: string): void {
+  if (typeof window === "undefined") return;
+  try {
+    window.localStorage.removeItem(key);
+  } catch {
+    // Best-effort cleanup only.
+  }
+}
diff --git a/src/stores/auth/auth-status-checker.tsx b/src/stores/auth/auth-status-checker.tsx
index b3bd65d6..71308e61 100644
--- a/src/stores/auth/auth-status-checker.tsx
+++ b/src/stores/auth/auth-status-checker.tsx
@@ -5,11 +5,12 @@
  * 派发时机：仅 mount 时一次（`useEffect` deps = `[dispatch]`，永远不重跑）。
  *
  * 与 <OAuthSessionSync /> 平级：
- *   - AuthStatusChecker: 启动时一次性 init，恢复登录态、绑定 ASID/PSID、尝试 PSID 直登
+ *   - AuthStatusChecker: 启动时先跑 storage migration，再恢复登录态、绑定 ASID/PSID、尝试 PSID 直登
  *   - OAuthSessionSync:   持续监听 NextAuth session（"别人在写"）
  */
 import { useEffect } from "react";
 
+import { runStorageMigrations } from "@/data/storage";
 import { useAuthDispatch } from "./auth-context";
 import { Logger } from "@/utils";
 
@@ -19,8 +20,26 @@ export function AuthStatusChecker() {
   const dispatch = useAuthDispatch();
 
   useEffect(() => {
-    log.debug("[auth-init] mount → dispatch AuthInit");
-    dispatch({ type: "AuthInit" });
+    let cancelled = false;
+
+    async function runStartupAuthInit() {
+      const migrationResult = await runStorageMigrations();
+      if (!migrationResult.success) {
+        log.warn(
+          { err: migrationResult.error.message },
+          "[auth-init] storage migration failed; continuing AuthInit",
+        );
+      }
+      if (cancelled) return;
+      log.debug("[auth-init] mount → dispatch AuthInit");
+      dispatch({ type: "AuthInit" });
+    }
+
+    void runStartupAuthInit();
+
+    return () => {
+      cancelled = true;
+    };
   }, [dispatch]);
 
   // 无 UI