diff --git a/src/app/_components/core/__tests__/tailwind-components.test.tsx b/src/app/_components/core/__tests__/tailwind-components.test.tsx
new file mode 100644
index 00000000..7dcdaaca
--- /dev/null
+++ b/src/app/_components/core/__tests__/tailwind-components.test.tsx
@@ -0,0 +1,21 @@
+import { renderToStaticMarkup } from "react-dom/server";
+import { describe, expect, it } from "vitest";
+
+import { LoadingIndicator } from "../loading-indicator";
+
+describe("core Tailwind components", () => {
+  it("renders LoadingIndicator with accessible status and dynamic sizing", () => {
+    const html = renderToStaticMarkup(
+      <LoadingIndicator size={24} strokeWidth={2} color="#f00" label="Loading now" />,
+    );
+
+    expect(html).toContain('role="status"');
+    expect(html).toContain('aria-label="Loading"');
+    expect(html).toContain("animate-spin");
+    expect(html).toContain("width:24px");
+    expect(html).toContain("height:24px");
+    expect(html).toContain("border-width:2px");
+    expect(html).toContain("border-color:#f00 transparent transparent transparent");
+    expect(html).toContain("Loading now");
+  });
+});
diff --git a/src/app/_components/core/loading-indicator.module.css b/src/app/_components/core/loading-indicator.module.css
deleted file mode 100644
index e9ed37a5..00000000
--- a/src/app/_components/core/loading-indicator.module.css
+++ /dev/null
@@ -1,26 +0,0 @@
-.wrapper {
-  display: inline-flex;
-  flex-direction: column;
-  align-items: center;
-  gap: var(--spacing-sm);
-}
-
-.spinner {
-  display: inline-block;
-  border-style: solid;
-  border-color: var(--color-text-secondary) transparent transparent
-    transparent;
-  border-radius: 50%;
-  animation: spin 0.8s linear infinite;
-}
-
-@keyframes spin {
-  to {
-    transform: rotate(360deg);
-  }
-}
-
-.label {
-  color: var(--color-text-secondary);
-  font-size: var(--font-size-sm);
-}
diff --git a/src/app/_components/core/loading-indicator.tsx b/src/app/_components/core/loading-indicator.tsx
index 0593f270..f6ed3dd8 100644
--- a/src/app/_components/core/loading-indicator.tsx
+++ b/src/app/_components/core/loading-indicator.tsx
@@ -7,10 +7,10 @@
  * 行为对齐 Flutter `CircularProgressIndicator`：
  *   - `size`：圆圈直径（默认 32）
  *   - `strokeWidth`：环宽（默认 3）
- *   - `color`：环颜色（默认 `--color-accent`）
+ *   - `color`：环颜色（默认 `--color-text-secondary`）
  *   - `label`：可选的可视标签（环形下方文本）
  */
-import styles from "./loading-indicator.module.css";
+import type { CSSProperties } from "react";
 
 export interface LoadingIndicatorProps {
   size?: number;
@@ -25,16 +25,28 @@ export function LoadingIndicator({
   color,
   label,
 }: LoadingIndicatorProps) {
-  const style: React.CSSProperties = {
+  const spinnerColor = color ?? "var(--color-text-secondary)";
+  const style: CSSProperties = {
     width: size,
     height: size,
     borderWidth: strokeWidth,
-    ...(color ? { borderTopColor: color } : {}),
+    borderColor: `${spinnerColor} transparent transparent transparent`,
   };
   return (
-    <div className={styles.wrapper} role="status" aria-label="Loading">
-      <div className={styles.spinner} style={style} />
-      {label ? <span className={styles.label}>{label}</span> : null}
+    <div
+      className="inline-flex flex-col items-center gap-sm"
+      role="status"
+      aria-label="Loading"
+    >
+      <div
+        className="inline-block animate-spin rounded-full border-solid"
+        style={style}
+      />
+      {label ? (
+        <span className="text-[var(--font-size-sm)] text-text-secondary">
+          {label}
+        </span>
+      ) : null}
     </div>
   );
 }
diff --git a/src/app/auth/components/__tests__/tailwind-components.test.tsx b/src/app/auth/components/__tests__/tailwind-components.test.tsx
new file mode 100644
index 00000000..91fede1a
--- /dev/null
+++ b/src/app/auth/components/__tests__/tailwind-components.test.tsx
@@ -0,0 +1,15 @@
+import { renderToStaticMarkup } from "react-dom/server";
+import { describe, expect, it } from "vitest";
+
+import { AuthErrorMessage } from "../auth-error-message";
+
+describe("auth Tailwind components", () => {
+  it("renders AuthErrorMessage only when a message is present", () => {
+    expect(renderToStaticMarkup(<AuthErrorMessage message={null} />)).toBe("");
+
+    const html = renderToStaticMarkup(<AuthErrorMessage message="Invalid email" />);
+    expect(html).toContain('role="alert"');
+    expect(html).toContain("text-error");
+    expect(html).toContain("Invalid email");
+  });
+});
diff --git a/src/app/auth/components/auth-error-message.module.css b/src/app/auth/components/auth-error-message.module.css
deleted file mode 100644
index 24854701..00000000
--- a/src/app/auth/components/auth-error-message.module.css
+++ /dev/null
@@ -1,16 +0,0 @@
-/* 
- *
- * 视觉规格（与 Dart 对齐）：
- *   - 细小红字，无背景，无圆角，无边框
- *   - 12px 居中
- */
-.banner {
-  width: 100%;
-  padding: 0;
-  background: transparent;
-  border: none;
-  color: var(--color-error);
-  font-size: var(--responsive-caption, var(--font-size-sm));
-  line-height: 1.4;
-  text-align: center;
-}
diff --git a/src/app/auth/components/auth-error-message.tsx b/src/app/auth/components/auth-error-message.tsx
index 8930edb0..824d4a2f 100644
--- a/src/app/auth/components/auth-error-message.tsx
+++ b/src/app/auth/components/auth-error-message.tsx
@@ -4,12 +4,13 @@
  *
  * 
  */
-import styles from "./auth-error-message.module.css";
-
 export function AuthErrorMessage({ message }: { message: string | null }) {
   if (!message) return null;
   return (
-    <div className={styles.banner} role="alert">
+    <div
+      className="w-full bg-transparent p-0 text-center text-[var(--responsive-caption)] leading-[1.4] text-error"
+      role="alert"
+    >
       {message}
     </div>
   );
diff --git a/src/app/chat/components/__tests__/pwa-install-overlay.test.tsx b/src/app/chat/components/__tests__/pwa-install-overlay.test.tsx
new file mode 100644
index 00000000..d2e24cca
--- /dev/null
+++ b/src/app/chat/components/__tests__/pwa-install-overlay.test.tsx
@@ -0,0 +1,10 @@
+import { renderToStaticMarkup } from "react-dom/server";
+import { describe, expect, it } from "vitest";
+
+import { PwaInstallOverlay } from "../pwa-install-overlay";
+
+describe("PwaInstallOverlay", () => {
+  it("does not render visible markup", () => {
+    expect(renderToStaticMarkup(<PwaInstallOverlay enabled />)).toBe("");
+  });
+});
diff --git a/src/app/chat/components/pwa-install-overlay.module.css b/src/app/chat/components/pwa-install-overlay.module.css
deleted file mode 100644
index 85554c11..00000000
--- a/src/app/chat/components/pwa-install-overlay.module.css
+++ /dev/null
@@ -1,5 +0,0 @@
-/* PwaInstallOverlay PWA 安装弹窗触发器样式（无可见 UI，逻辑触发用） */
-
-.hidden {
-  display: none;
-}
diff --git a/src/app/chat/components/pwa-install-overlay.tsx b/src/app/chat/components/pwa-install-overlay.tsx
index 1bc551d9..911ad1b5 100644
--- a/src/app/chat/components/pwa-install-overlay.tsx
+++ b/src/app/chat/components/pwa-install-overlay.tsx
@@ -22,7 +22,6 @@ import {
 import { pwaUtil } from "@/utils";
 
 import { PwaInstallDialog } from "./pwa-install-dialog";
-import styles from "./pwa-install-overlay.module.css";
 
 const DEVELOPMENT_DIALOG_DELAY_MS = 1000;
 const PRODUCTION_DIALOG_DELAY_MS = 1500;
@@ -74,7 +73,7 @@ export function PwaInstallOverlay({ enabled }: PwaInstallOverlayProps) {
     };
   }, [enabled]);
 
-  return <div className={styles.hidden} aria-hidden="true" />;
+  return null;
 }
 
 async function shouldShowPwaInstallDialog(isDevelopment: boolean) {