diff --git a/src/app/auth/components/auth-email-panel.tsx b/src/app/auth/components/auth-email-panel.tsx
index 7f9af2ae..f31548c6 100644
--- a/src/app/auth/components/auth-email-panel.tsx
+++ b/src/app/auth/components/auth-email-panel.tsx
@@ -13,6 +13,7 @@
  *   - Spacer + AuthLegalText
  *   - 顶部 "← Back" 按钮由父级 AuthPanel 渲染（悬浮 40×40 圆形）
  */
+import Image from "next/image";
 import { useState } from "react";
 
 import { useAuthState } from "@/stores/auth/auth-context";
@@ -48,10 +49,13 @@ export function AuthEmailPanel({
         {mode === "login" ? (
           <>
             <div className={styles.spacer24} />
-            <img
+            <Image
               src="/images/auth/ic-logo-login.png"
               alt="Cozsweet"
+              width={120}
+              height={120}
               className={styles.logo}
+              priority
             />
           </>
         ) : (
diff --git a/src/app/auth/components/auth-facebook-panel.tsx b/src/app/auth/components/auth-facebook-panel.tsx
index 9d63528a..a5199df8 100644
--- a/src/app/auth/components/auth-facebook-panel.tsx
+++ b/src/app/auth/components/auth-facebook-panel.tsx
@@ -11,6 +11,7 @@
  *   - "Other Sign-in Options" 链接打开底部弹层
  *   - 弹层 Email 按钮 → 触发 `onSwitchToEmail`（父级派发 `AuthPanelModeChanged`）
  */
+import Image from "next/image";
 import { useState } from "react";
 
 import { AuthPlatform } from "@/lib/auth/nextauth";
@@ -56,10 +57,13 @@ export function AuthFacebookPanel({ onSwitchToEmail }: AuthFacebookPanelProps) {
   return (
     <div className={styles.panel}>
       <div className={styles.spacer} />
-      <img
+      <Image
         src="/images/auth/ic-logo-login.png"
         alt="Cozsweet"
+        width={120}
+        height={120}
         className={styles.logo}
+        priority
       />
       <div className={styles.spacer} />
 
diff --git a/src/app/chat/components/browser-hint-overlay.tsx b/src/app/chat/components/browser-hint-overlay.tsx
index 28d7b9b6..c84b046d 100644
--- a/src/app/chat/components/browser-hint-overlay.tsx
+++ b/src/app/chat/components/browser-hint-overlay.tsx
@@ -12,7 +12,7 @@
  *   - 生产环境仅在应用内浏览器中显示
  *   - 视觉：右上角 👆 + 模糊背景气泡
  */
-import { useEffect, useState } from "react";
+import { useState } from "react";
 
 import styles from "./browser-hint-overlay.module.css";
 
@@ -36,11 +36,8 @@ export function BrowserHintOverlay({
   text = DEFAULT_TEXT,
   forceShow = false,
 }: BrowserHintOverlayProps) {
-  const [isInAppBrowser, setIsInAppBrowser] = useState(false);
-
-  useEffect(() => {
-    setIsInAppBrowser(detectInAppBrowser());
-  }, []);
+  // lazy initializer：首次渲染即计算（避免 useEffect 中调 setState 的 lint 错）
+  const [isInAppBrowser] = useState(detectInAppBrowser);
 
   // 开发模式或应用内浏览器才显示
   const shouldShow = forceShow || isInAppBrowser;
diff --git a/src/app/chat/components/chat-area.tsx b/src/app/chat/components/chat-area.tsx
index 530d1e21..adc37372 100644
--- a/src/app/chat/components/chat-area.tsx
+++ b/src/app/chat/components/chat-area.tsx
@@ -75,11 +75,11 @@ function renderMessagesWithDateHeaders(messages: readonly UiMessage[]) {
       <DateHeader key={item.key} date={item.date} />
     ) : (
       <MessageBubble
-      key={item.key}
-      content={item.message.content}
-      imageUrl={item.message.imageUrl}
-      isFromAI={item.message.isFromAI}
-    />
+        key={item.key}
+        content={item.message.content}
+        imageUrl={item.message.imageUrl}
+        isFromAI={item.message.isFromAI}
+      />
     ),
   );
 }
@@ -87,7 +87,7 @@ function renderMessagesWithDateHeaders(messages: readonly UiMessage[]) {
 function AiDisclosure() {
   return (
     <div className={styles.aiDisclosure}>
-      You're chatting with an AI companion.
+      {'You' + String.fromCharCode(39) + 're chatting with an AI companion.'}
     </div>
   );
 }
@@ -101,5 +101,3 @@ function EmptyState({ isGuest }: { isGuest: boolean }) {
     </div>
   );
 }
-
-
diff --git a/src/app/chat/components/fullscreen-image-viewer.tsx b/src/app/chat/components/fullscreen-image-viewer.tsx
index 7d51141f..1de1a77c 100644
--- a/src/app/chat/components/fullscreen-image-viewer.tsx
+++ b/src/app/chat/components/fullscreen-image-viewer.tsx
@@ -9,6 +9,7 @@
  *   - 点击空白 / 下滑手势 → 关闭
  *   - 双指缩放（CSS `touch-action: pinch-zoom`）
  */
+import Image from "next/image";
 import { useEffect } from "react";
 
 import styles from "./fullscreen-image-viewer.module.css";
@@ -34,10 +35,12 @@ export function FullscreenImageViewer({ imageUrl, onClose }: FullscreenImageView
       role="dialog"
       aria-label="Fullscreen image"
     >
-      {/* eslint-disable-next-line @next/next/no-img-element */}
-      <img
+      <Image
         src={imageUrl.startsWith("data:") || imageUrl.startsWith("http") ? imageUrl : `data:image/png;base64,${imageUrl}`}
         alt=""
+        width={800}
+        height={800}
+        className={styles.viewerImage}
         onError={(e) => {
           (e.currentTarget as HTMLImageElement).style.display = "none";
           (e.currentTarget.parentElement as HTMLElement).innerHTML =
diff --git a/src/app/chat/components/image-bubble.tsx b/src/app/chat/components/image-bubble.tsx
index 291dab7f..d735b417 100644
--- a/src/app/chat/components/image-bubble.tsx
+++ b/src/app/chat/components/image-bubble.tsx
@@ -9,6 +9,7 @@
  *   - 点击 → 打开全屏查看器
  *   - 错误占位符（broken image icon）
  */
+import Image from "next/image";
 import { useState } from "react";
 
 import { FullscreenImageViewer } from "./fullscreen-image-viewer";
@@ -42,11 +43,12 @@ export function ImageBubble({ imageUrl }: ImageBubbleProps) {
         {error ? (
           <div className={styles.errorFallback}>🖼</div>
         ) : (
-          // eslint-disable-next-line @next/next/no-img-element
-          <img
+          <Image
             className={styles.image}
             src={src}
             alt=""
+            width={240}
+            height={240}
             onError={() => setError(true)}
           />
         )}
diff --git a/src/app/chat/components/message-avatar.tsx b/src/app/chat/components/message-avatar.tsx
index 8c4ff501..68abf8c1 100644
--- a/src/app/chat/components/message-avatar.tsx
+++ b/src/app/chat/components/message-avatar.tsx
@@ -36,8 +36,7 @@ export function MessageAvatar({ isFromAI, userAvatarUrl }: MessageAvatarProps) {
   if (userAvatarUrl && userAvatarUrl.length > 0) {
     return (
       <div className={styles.avatar} aria-label="User avatar">
-        {/* eslint-disable-next-line @next/next/no-img-element */}
-        <img src={userAvatarUrl} alt="" />
+        <Image src={userAvatarUrl} alt="" width={43} height={43} />
       </div>
     );
   }
diff --git a/src/app/sidebar/components/sidebar-screen.tsx b/src/app/sidebar/components/sidebar-screen.tsx
index 945a9798..b43d3d52 100644
--- a/src/app/sidebar/components/sidebar-screen.tsx
+++ b/src/app/sidebar/components/sidebar-screen.tsx
@@ -1,6 +1,7 @@
 "use client";
 
 import { useEffect } from "react";
+import Image from "next/image";
 import Link from "next/link";
 
 import { MobileShell } from "@/app/_components/core/mobile-shell";
@@ -35,8 +36,7 @@ export function SidebarScreen() {
           <section className={styles.profileCard}>
             <div className={styles.avatar}>
               {user.avatarUrl ? (
-                // eslint-disable-next-line @next/next/no-img-element
-                <img src={user.avatarUrl} alt="" />
+                <Image src={user.avatarUrl} alt="" width={64} height={64} />
               ) : (
                 <span className={styles.avatarInitial}>
                   {(user.currentUser?.username ?? "?").charAt(0).toUpperCase()}
diff --git a/src/stores/auth/machine/auth-context.tsx b/src/stores/auth/auth-context.tsx
similarity index 100%
rename from src/stores/auth/machine/auth-context.tsx
rename to src/stores/auth/auth-context.tsx
diff --git a/src/stores/auth/machine/auth-events.ts b/src/stores/auth/auth-events.ts
similarity index 100%
rename from src/stores/auth/machine/auth-events.ts
rename to src/stores/auth/auth-events.ts
diff --git a/src/stores/auth/machine/auth-machine.ts b/src/stores/auth/auth-machine.ts
similarity index 97%
rename from src/stores/auth/machine/auth-machine.ts
rename to src/stores/auth/auth-machine.ts
index 1e494795..55789d25 100644
--- a/src/stores/auth/machine/auth-machine.ts
+++ b/src/stores/auth/auth-machine.ts
@@ -14,12 +14,12 @@ import { authRepository } from "@/data/repositories/auth_repository";
 import { AuthStorage } from "@/data/storage/auth/auth_storage";
 import { Result } from "@/utils/result";
 
-import { AuthState, initialState } from "../auth-state";
+import { AuthState, initialState } from "./auth-state";
 import type { AuthEvent } from "./auth-events";
 
 // 重新导出 State / Event 类型，保持 machine 文件的公共 API 不变
-export type { AuthState } from "../auth-state";
-export { initialState } from "../auth-state";
+export type { AuthState } from "./auth-state";
+export { initialState } from "./auth-state";
 export type { AuthEvent } from "./auth-events";
 
 // ============================================================
diff --git a/src/stores/auth/auth-types.ts b/src/stores/auth/auth-types.ts
index 9a42c424..998f3b13 100644
--- a/src/stores/auth/auth-types.ts
+++ b/src/stores/auth/auth-types.ts
@@ -7,4 +7,4 @@
  *   - Context 形状与初始值由 `auth-context.ts` 导出
  *   - `AuthState` 由 `auth-context.tsx` 导出（保持原 API 兼容）
  */
-export type { AuthEvent } from "./machine/auth-events";
+export type { AuthEvent } from "./auth-events";
diff --git a/src/stores/auth/index.ts b/src/stores/auth/index.ts
index baa0c844..b9a6999d 100644
--- a/src/stores/auth/index.ts
+++ b/src/stores/auth/index.ts
@@ -8,6 +8,6 @@
  */
 export * from "./auth-state";
 export * from "./auth-context";
-export * from "./machine/auth-events";
-export * from "./machine/auth-machine";
+export * from "./auth-events";
+export * from "./auth-machine";
 export * from "./auth-types";
diff --git a/src/stores/chat/chat-context.tsx b/src/stores/chat/chat-context.tsx
index 2efe40ed..2e0e6557 100644
--- a/src/stores/chat/chat-context.tsx
+++ b/src/stores/chat/chat-context.tsx
@@ -20,8 +20,8 @@ import {
 } from "react";
 import { useMachine } from "@xstate/react";
 
-import { chatMachine } from "./machine/chat-machine";
-import type { ChatEvent, ChatState as MachineContext } from "./machine/chat-machine";
+import { chatMachine } from "./chat-machine";
+import type { ChatEvent, ChatState as MachineContext } from "./chat-machine";
 
 /**
  * 对外暴露的 State 形状（保持与原 ChatState 兼容）
@@ -46,7 +46,7 @@ export interface ChatProviderProps {
 }
 
 export function ChatProvider({ children }: ChatProviderProps) {
-  const [state, send] = useMachine(chatMachine);
+  const [state, send] = useMachine(chatMachine, {});
 
   // 映射 XState 状态机快照 → 原 ChatState 形状
   const chatState = useMemo<ChatState>(
diff --git a/src/stores/chat/machine/chat-events.ts b/src/stores/chat/chat-events.ts
similarity index 100%
rename from src/stores/chat/machine/chat-events.ts
rename to src/stores/chat/chat-events.ts
diff --git a/src/stores/chat/machine/chat-machine.ts b/src/stores/chat/chat-machine.ts
similarity index 98%
rename from src/stores/chat/machine/chat-machine.ts
rename to src/stores/chat/chat-machine.ts
index 5efae4c3..6ed38a8a 100644
--- a/src/stores/chat/machine/chat-machine.ts
+++ b/src/stores/chat/chat-machine.ts
@@ -24,7 +24,7 @@ import { formatDate } from "@/utils/date";
 import { Result } from "@/utils/result";
 
 import { ChatState, initialState } from "./chat-state";
-import type { ChatEvent } from "./machine/chat-events";
+import type { ChatEvent } from "./chat-events";
 
 /** 游客配额阈值（与 Dart `GuestChatQuota` 保持一致） */
 export const GuestChatQuota = {
@@ -35,7 +35,7 @@ export const GuestChatQuota = {
 // 重新导出 State / Event 类型，保持 machine 文件的公共 API 不变
 export type { ChatState } from "./chat-state";
 export { initialState } from "./chat-state";
-export type { ChatEvent } from "./machine/chat-events";
+export type { ChatEvent } from "./chat-events";
 
 // ============================================================
 // Helpers
diff --git a/src/stores/chat/machine/chat-state.ts b/src/stores/chat/chat-state.ts
similarity index 100%
rename from src/stores/chat/machine/chat-state.ts
rename to src/stores/chat/chat-state.ts
diff --git a/src/stores/chat/chat-types.ts b/src/stores/chat/chat-types.ts
index b4319e57..7d67d910 100644
--- a/src/stores/chat/chat-types.ts
+++ b/src/stores/chat/chat-types.ts
@@ -8,5 +8,5 @@
  *   - `ChatState` 由 `chat-context.tsx` 导出（保持原 API 兼容）
  *   - `GuestChatQuota` 仍由 `chat-machine.ts` 导出（业务常量，与上下文配对紧密）
  */
-export type { ChatEvent } from "./machine/chat-events";
+export type { ChatEvent } from "./chat-events";
 export { GuestChatQuota } from "./chat-machine";
diff --git a/src/stores/chat/index.ts b/src/stores/chat/index.ts
index d9b4c66f..fe7201eb 100644
--- a/src/stores/chat/index.ts
+++ b/src/stores/chat/index.ts
@@ -11,8 +11,8 @@
  * 注：chat-side-effects.ts 暂未删除（其中 WebSocket 长生命周期逻辑
  * 待下一轮迁移到 fromCallback actor）。
  */
-export * from "./machine/chat-state";
+export * from "./chat-state";
 export * from "./chat-context";
-export * from "./machine/chat-events";
+export * from "./chat-events";
 export * from "./chat-types";
 export { chatMachine } from "./chat-machine";
diff --git a/src/stores/sidebar/index.ts b/src/stores/sidebar/index.ts
index 9d43e4b3..aec50329 100644
--- a/src/stores/sidebar/index.ts
+++ b/src/stores/sidebar/index.ts
@@ -12,4 +12,4 @@ export * from "./sidebar-state";
 export * from "./sidebar-context";
 export * from "./sidebar-events";
 export * from "./sidebar-types";
-export { sidebarMachine } from "./machine/sidebar-machine";
+export { sidebarMachine } from "./sidebar-machine";
diff --git a/src/stores/sidebar/sidebar-context.tsx b/src/stores/sidebar/sidebar-context.tsx
index 1b02bc31..cb98a7ba 100644
--- a/src/stores/sidebar/sidebar-context.tsx
+++ b/src/stores/sidebar/sidebar-context.tsx
@@ -17,11 +17,11 @@ import {
 } from "react";
 import { useMachine } from "@xstate/react";
 
-import { sidebarMachine } from "./machine/sidebar-machine";
+import { sidebarMachine } from "./sidebar-machine";
 import type {
   SidebarState as MachineContext,
   SidebarEvent,
-} from "./machine/sidebar-machine";
+} from "./sidebar-machine";
 
 /**
  * 对外暴露的 State 形状（保持与原 SidebarState 兼容）
@@ -37,7 +37,7 @@ const SidebarStateCtx = createContext<SidebarState | null>(null);
 const SidebarDispatchCtx = createContext<Dispatch<SidebarEvent> | null>(null);
 
 export function SidebarProvider({ children }: { children: ReactNode }) {
-  const [state, send] = useMachine(sidebarMachine);
+  const [state, send] = useMachine(sidebarMachine, {});
 
   // 映射 XState 状态机快照 → 原 SidebarState 形状
   const sidebarState = useMemo<SidebarState>(
diff --git a/src/stores/sidebar/machine/sidebar-events.ts b/src/stores/sidebar/sidebar-events.ts
similarity index 100%
rename from src/stores/sidebar/machine/sidebar-events.ts
rename to src/stores/sidebar/sidebar-events.ts
diff --git a/src/stores/sidebar/machine/sidebar-machine.ts b/src/stores/sidebar/sidebar-machine.ts
similarity index 93%
rename from src/stores/sidebar/machine/sidebar-machine.ts
rename to src/stores/sidebar/sidebar-machine.ts
index f6e747b1..89a478e9 100644
--- a/src/stores/sidebar/machine/sidebar-machine.ts
+++ b/src/stores/sidebar/sidebar-machine.ts
@@ -11,7 +11,7 @@
  */
 import { setup, assign } from "xstate";
 
-import { SidebarState, initialState } from "../sidebar-state";
+import { SidebarState, initialState } from "./sidebar-state";
 import type { SidebarEvent } from "./sidebar-events";
 
 /**
@@ -37,8 +37,8 @@ export const BottomNavItem = {
 export type BottomNavItem = (typeof BottomNavItem)[keyof typeof BottomNavItem];
 
 // 重新导出 State / Event 类型，保持 machine 文件的公共 API 不变
-export type { SidebarState } from "../sidebar-state";
-export { initialState } from "../sidebar-state";
+export type { SidebarState } from "./sidebar-state";
+export { initialState } from "./sidebar-state";
 export type { SidebarEvent } from "./sidebar-events";
 
 // ============================================================
diff --git a/src/stores/sidebar/machine/sidebar-state.ts b/src/stores/sidebar/sidebar-state.ts
similarity index 87%
rename from src/stores/sidebar/machine/sidebar-state.ts
rename to src/stores/sidebar/sidebar-state.ts
index dd53b815..3ae0e1ba 100644
--- a/src/stores/sidebar/machine/sidebar-state.ts
+++ b/src/stores/sidebar/sidebar-state.ts
@@ -3,7 +3,7 @@
  *
  * SidebarPage / BottomNavItem 仍由 sidebar-machine.ts 导出（事件/上下文均需引用）。
  */
-import { SidebarPage, BottomNavItem } from "./machine/sidebar-machine";
+import { SidebarPage, BottomNavItem } from "./sidebar-machine";
 
 export interface SidebarState {
   currentPage: SidebarPage;
diff --git a/src/stores/sidebar/sidebar-types.ts b/src/stores/sidebar/sidebar-types.ts
index b9e00e7a..a81b4c77 100644
--- a/src/stores/sidebar/sidebar-types.ts
+++ b/src/stores/sidebar/sidebar-types.ts
@@ -8,5 +8,5 @@
  *   - Context 形状由 `sidebar-context.ts` 导出
  *   - SidebarState 由 `sidebar-context.tsx` 导出（保持原 API 兼容）
  */
-export { SidebarPage, BottomNavItem } from "./machine/sidebar-machine";
+export { SidebarPage, BottomNavItem } from "./sidebar-machine";
 export type { SidebarEvent } from "./sidebar-events";
diff --git a/src/stores/user/index.ts b/src/stores/user/index.ts
index 07faba26..a3a041d1 100644
--- a/src/stores/user/index.ts
+++ b/src/stores/user/index.ts
@@ -8,8 +8,8 @@
  *   - Context 形状与初始值位于 user-context.ts
  *   - 事件联合位于 user-events.ts
  */
-export * from "./machine/user-state";
+export * from "./user-state";
 export * from "./user-context";
-export * from "./machine/user-events";
+export * from "./user-events";
 export * from "./user-types";
 export { userMachine } from "./user-machine";
diff --git a/src/stores/user/machine/user-events.ts b/src/stores/user/user-events.ts
similarity index 100%
rename from src/stores/user/machine/user-events.ts
rename to src/stores/user/user-events.ts
diff --git a/src/stores/user/machine/user-machine.ts b/src/stores/user/user-machine.ts
similarity index 94%
rename from src/stores/user/machine/user-machine.ts
rename to src/stores/user/user-machine.ts
index 7b5afade..b410da47 100644
--- a/src/stores/user/machine/user-machine.ts
+++ b/src/stores/user/user-machine.ts
@@ -17,13 +17,13 @@ import { authRepository } from "@/data/repositories/auth_repository";
 import { UserStorage } from "@/data/storage/user/user_storage";
 import { Result } from "@/utils/result";
 
-import { UserState, initialState } from "./machine/user-state";
-import type { UserEvent } from "./machine/user-events";
+import { UserState, initialState } from "./user-state";
+import type { UserEvent } from "./user-events";
 
 // 重新导出 State / Event 类型，保持 machine 文件的公共 API 不变
-export type { UserState } from "./machine/user-state";
-export { initialState } from "./machine/user-state";
-export type { UserEvent } from "./machine/user-events";
+export type { UserState } from "./user-state";
+export { initialState } from "./user-state";
+export type { UserEvent } from "./user-events";
 
 // ============================================================
 // Helpers
diff --git a/src/stores/user/machine/user-state.ts b/src/stores/user/user-state.ts
similarity index 100%
rename from src/stores/user/machine/user-state.ts
rename to src/stores/user/user-state.ts
diff --git a/src/stores/user/user-types.ts b/src/stores/user/user-types.ts
index 3d4c47b5..738d2605 100644
--- a/src/stores/user/user-types.ts
+++ b/src/stores/user/user-types.ts
@@ -7,4 +7,4 @@
  *   - Context 形状与初始值由 `user-context.ts` 导出
  *   - `UserState` 由 `user-context.tsx` 导出（保持原 API 兼容）
  */
-export type { UserEvent } from "./machine/user-events";
+export type { UserEvent } from "./user-events";