diff --git a/apps/ai-game-creator-shell/src/services/clientHttp.ts b/apps/ai-game-creator-shell/src/services/clientHttp.ts
index d8f2a9902..5bc5740b9 100644
--- a/apps/ai-game-creator-shell/src/services/clientHttp.ts
+++ b/apps/ai-game-creator-shell/src/services/clientHttp.ts
@@ -2,6 +2,8 @@ import { fetch as tauriHttpFetch } from '@tauri-apps/plugin-http';
 
 export const AGC_DEVELOPMENT_API_BASE_URL = 'https://dev.genarrative.world';
 export const AGC_RELEASE_API_BASE_URL = 'https://www.genarrative.world';
+export const AGC_CLIENT_MARKER_HEADER = 'X-Genarrative-Client';
+export const AGC_CLIENT_MARKER_VALUE = 'agc';
 
 export type ClientServerPreset = 'release' | 'dev' | 'custom';
 
@@ -125,6 +127,12 @@ type ClientHttpTarget = {
   url: string;
 };
 
+function withAgcClientMarker(init: RequestInit): RequestInit {
+  const headers = new Headers(init.headers);
+  headers.set(AGC_CLIENT_MARKER_HEADER, AGC_CLIENT_MARKER_VALUE);
+  return { ...init, headers };
+}
+
 function currentClientHttpContext(): ClientHttpContext {
   return {
     isDevelopment: import.meta.env.DEV,
@@ -177,8 +185,9 @@ export async function fetchClientHttp(
       ? currentContext
       : { ...currentContext, serverBaseUrl },
   );
+  const markedInit = withAgcClientMarker(init);
   if (target.transport === 'tauri-http') {
-    return tauriHttpFetch(target.url, init);
+    return tauriHttpFetch(target.url, markedInit);
   }
-  return fetch(target.url, init);
+  return fetch(target.url, markedInit);
 }
diff --git a/apps/ai-game-creator-shell/tests/clientHttp.test.ts b/apps/ai-game-creator-shell/tests/clientHttp.test.ts
index 8b6114d3a..5c0f8d235 100644
--- a/apps/ai-game-creator-shell/tests/clientHttp.test.ts
+++ b/apps/ai-game-creator-shell/tests/clientHttp.test.ts
@@ -1,8 +1,16 @@
-import { afterEach, describe, expect, it } from 'vitest';
+import { fetch as tauriHttpFetch } from '@tauri-apps/plugin-http';
+import { afterEach, describe, expect, it, vi } from 'vitest';
 
 import {
+  API_RESPONSE_ENVELOPE_HEADER,
+  API_RESPONSE_ENVELOPE_VERSION,
+} from '../../../packages/shared/src/http';
+import {
+  AGC_CLIENT_MARKER_HEADER,
+  AGC_CLIENT_MARKER_VALUE,
   AGC_DEVELOPMENT_API_BASE_URL,
   AGC_RELEASE_API_BASE_URL,
+  fetchClientHttp,
   getClientServerBaseUrl,
   getClientServerSelection,
   normalizeClientServerBaseUrl,
@@ -11,8 +19,106 @@ import {
   setClientServerSelection,
 } from '../src/services/clientHttp';
 
+vi.mock('@tauri-apps/plugin-http', () => ({
+  fetch: vi.fn(),
+}));
+
 describe('AGC client HTTP transport', () => {
-  afterEach(() => resetClientServerSelectionForTests());
+  afterEach(() => {
+    vi.clearAllMocks();
+    vi.unstubAllEnvs();
+    vi.unstubAllGlobals();
+    resetClientServerSelectionForTests();
+  });
+
+  it('adds the AGC marker while preserving and overriding request headers', async () => {
+    const fetchMock = vi
+      .fn()
+      .mockResolvedValue(new Response(null, { status: 204 }));
+    vi.stubGlobal('fetch', fetchMock);
+    const inputHeaders = new Headers({
+      Authorization: 'Bearer fixture-token',
+      'X-Request-ID': 'request-123',
+      [API_RESPONSE_ENVELOPE_HEADER]: API_RESPONSE_ENVELOPE_VERSION,
+      [AGC_CLIENT_MARKER_HEADER]: 'caller-value',
+    });
+    const init: RequestInit = {
+      method: 'POST',
+      headers: inputHeaders,
+      body: '{}',
+      credentials: 'same-origin',
+    };
+
+    await fetchClientHttp('/api/auth/me', init);
+
+    expect(fetchMock).toHaveBeenCalledTimes(1);
+    const [target, forwardedInit] = fetchMock.mock.calls[0] as [
+      string,
+      RequestInit,
+    ];
+    const forwardedHeaders = new Headers(forwardedInit.headers);
+    expect(target).toBe('/api/auth/me');
+    expect(forwardedHeaders.get(AGC_CLIENT_MARKER_HEADER)).toBe(
+      AGC_CLIENT_MARKER_VALUE,
+    );
+    expect(forwardedHeaders.get('Authorization')).toBe('Bearer fixture-token');
+    expect(forwardedHeaders.get('X-Request-ID')).toBe('request-123');
+    expect(forwardedHeaders.get(API_RESPONSE_ENVELOPE_HEADER)).toBe(
+      API_RESPONSE_ENVELOPE_VERSION,
+    );
+    expect(forwardedInit.method).toBe('POST');
+    expect(forwardedInit.body).toBe('{}');
+    expect(forwardedInit.credentials).toBe('same-origin');
+    expect(inputHeaders.get(AGC_CLIENT_MARKER_HEADER)).toBe('caller-value');
+  });
+
+  it.each([
+    '/api/auth/me',
+    '/api/profile/dashboard',
+    '/api/editor/projects',
+    '/api/assets/read-bytes?objectKey=fixture',
+  ])('marks %s through the shared Web transport', async (url) => {
+    const fetchMock = vi
+      .fn()
+      .mockResolvedValue(new Response(null, { status: 204 }));
+    vi.stubGlobal('fetch', fetchMock);
+
+    await fetchClientHttp(url, {});
+
+    const [, forwardedInit] = fetchMock.mock.calls[0] as [string, RequestInit];
+    expect(
+      new Headers(forwardedInit.headers).get(AGC_CLIENT_MARKER_HEADER),
+    ).toBe(AGC_CLIENT_MARKER_VALUE);
+  });
+
+  it('adds the AGC marker to the Tauri HTTP transport', async () => {
+    const tauriFetchMock = vi.mocked(tauriHttpFetch);
+    tauriFetchMock.mockResolvedValue(new Response(null, { status: 204 }));
+    vi.stubEnv('MODE', 'production');
+    vi.stubEnv('DEV', false);
+    vi.stubGlobal('window', {
+      __TAURI__: {},
+      location: { protocol: 'tauri:' },
+    });
+
+    await fetchClientHttp(
+      '/api/auth/me',
+      { headers: { Authorization: 'Bearer fixture-token' } },
+      { serverBaseUrl: AGC_DEVELOPMENT_API_BASE_URL },
+    );
+
+    expect(tauriFetchMock).toHaveBeenCalledTimes(1);
+    const [target, forwardedInit] = tauriFetchMock.mock.calls[0] as [
+      string,
+      RequestInit,
+    ];
+    const forwardedHeaders = new Headers(forwardedInit.headers);
+    expect(target).toBe(`${AGC_DEVELOPMENT_API_BASE_URL}/api/auth/me`);
+    expect(forwardedHeaders.get(AGC_CLIENT_MARKER_HEADER)).toBe(
+      AGC_CLIENT_MARKER_VALUE,
+    );
+    expect(forwardedHeaders.get('Authorization')).toBe('Bearer fixture-token');
+  });
 
   it('keeps local development requests on the Vite API proxy', () => {
     expect(
diff --git a/local-docs/【实施方案】Issue226-AGC客户端主站请求统一标记-2026-09-01.md b/local-docs/【实施方案】Issue226-AGC客户端主站请求统一标记-2026-09-01.md
index 14d8ef7d9..cc2327c85 100644
--- a/local-docs/【实施方案】Issue226-AGC客户端主站请求统一标记-2026-09-01.md
+++ b/local-docs/【实施方案】Issue226-AGC客户端主站请求统一标记-2026-09-01.md
@@ -6,7 +6,7 @@
 - `#226 添加客户端特殊标识`：本方案实际实施范围
 - `#225 添加客户端埋点统计`：主站接收、落库和后台统计，本文只冻结交接契约，不在本次实施
 
-状态：阶段 0 已完成，待阶段 1 实施<br>
+状态：阶段 1 已完成，待阶段 2 实施<br>
 本方案不包含代码修改
 
 ## 1. 一句话交付结果
diff --git a/local-docs/【实施计划】Issue226-AGC客户端主站请求标记分阶段验收-2026-09-01.md b/local-docs/【实施计划】Issue226-AGC客户端主站请求标记分阶段验收-2026-09-01.md
index 4b8744cb9..a8e0d9588 100644
--- a/local-docs/【实施计划】Issue226-AGC客户端主站请求标记分阶段验收-2026-09-01.md
+++ b/local-docs/【实施计划】Issue226-AGC客户端主站请求标记分阶段验收-2026-09-01.md
@@ -6,7 +6,7 @@
 - `#226 添加客户端特殊标识`：本计划全部实施范围
 - `#225 添加客户端埋点统计`：只接收交接契约，不在本计划实现
 
-当前状态：阶段 0 已完成；阶段 1 尚未开始。阶段 0 的证据与验收记录见
+当前状态：阶段 1 已完成；阶段 2 尚未开始。阶段 0 的证据与验收记录见
 [【阶段验收】Issue226阶段0现状基线与契约冻结-2026-09-01.md](C:/projects/narrative/Genarrative/local-docs/【阶段验收】Issue226阶段0现状基线与契约冻结-2026-09-01.md)。
 
 ## 1. 交付目标
@@ -125,6 +125,14 @@ TS 定向测试必须证明：
 - 没有在业务 API 文件中出现重复 Header 注入。
 - 相关 TS 定向测试通过。
 
+### 5.4 阶段 1 实施记录
+
+- `clientHttp.ts` 新增固定 Header 常量，并在 `fetchClientHttp` 内通过 `Headers` 合并并覆盖同名调用方 Header。
+- Web `fetch` 与 Tauri HTTP plugin 都接收同一份带标记的 `RequestInit`；原始 `RequestInit.headers` 不被修改。
+- `clientHttp.test.ts` 已覆盖 `/api/auth/*`、`/api/profile/*`、`/api/editor/*`、`/api/assets/*`，并分别验证 Web/Tauri transport、Authorization、envelope Header、`X-Request-ID` 和同名 Header 覆盖。
+- 阶段 1 验证命令：`npm exec vitest run apps/ai-game-creator-shell/tests/clientHttp.test.ts`（14 tests passed）；`npm run ai-game-creator-shell:typecheck` 通过。
+- `appUpdate.ts` 未接入 `fetchClientHttp`，更新下载边界保持不变。
+
 ## 6. 阶段 2：Rust 主站 Client Builder factory
 
 ### 6.1 工作内容