diff --git a/docs/project-memory/shared-memory/decision-log.md b/docs/project-memory/shared-memory/decision-log.md
index 00f604710..51656f104 100644
--- a/docs/project-memory/shared-memory/decision-log.md
+++ b/docs/project-memory/shared-memory/decision-log.md
@@ -30,6 +30,7 @@
 - 2026-06-18 宿主 runtime 回读：主 App 启动时会通过真实 `host.getRuntime` 回读 Expo / Tauri runtime 并缓存过滤后的能力清单，能力来源为 URL `hostCapabilities` 与宿主真实回包的并集；裁剪壳或旧入口 URL 缺少 `hostCapabilities` 时也能启用真实声明能力，但仍不会仅凭 `native_app` 或 transport 存在推断能力可用。
 - 2026-06-18 壳能力防漂移：`npm run mobile-shell:typecheck` 与 `npm run desktop-shell:typecheck` 会校验 Expo / Tauri 壳声明的 capability 均来自共享 HostBridge 白名单，并校验壳 runtime 回包、H5 URL `hostCapabilities` 和实现分支保持一致；微信小程序 `WECHAT_HOST_CAPABILITIES` 由 `miniprogram/host-bridge/protocol.test.js` 和根级 `npm run check:native-shells` 反查共享 `HOST_BRIDGE_WECHAT_MINI_PROGRAM_CAPABILITIES`。新增能力必须先更新契约和真实壳实现，再通过这些检查。
 - 2026-06-19 宿主上下文 query 契约收口：`packages/shared/src/contracts/hostBridge.ts` 是宿主上下文 query 字段和值的唯一 TypeScript 来源；`HOST_BRIDGE_RUNTIME_CONTEXT_QUERY_KEY` 覆盖 H5 runtime parser 字段，`HOST_BRIDGE_NATIVE_APP_QUERY_KEY` / `HOST_BRIDGE_NATIVE_APP_QUERY_KEYS` / `HOST_BRIDGE_NATIVE_APP_QUERY` 固定 Expo / Tauri 原生壳入口 query，`HOST_BRIDGE_WECHAT_MINI_PROGRAM_SOURCE_QUERY` 固定微信 WebView 来源标记，`HOST_BRIDGE_PRESERVED_RUNTIME_CONTEXT_QUERY_KEYS` 固定 H5 页面内导航需要保留的宿主字段。Expo 壳直接引用共享常量，Tauri Rust 和微信 CommonJS 镜像由 `npm run check:native-shells` / 单壳配置检查反查；微信请求头必须从 `WEB_VIEW_SOURCE_QUERY` 读取 `clientType` / `clientRuntime`，不得另起常量。
+- 2026-06-19 H5 HostBridge 载荷边界收口：`src/services/host-bridge/hostBridge.ts` 作为 H5 facade 也必须直接导入 `HOST_BRIDGE_TEXT_MIME_TYPES`、`HOST_BRIDGE_DOCUMENT_MIME_TYPES`、`HOST_BRIDGE_IMAGE_MIME_TYPES` 和 `HOST_BRIDGE_AUDIO_MIME_TYPES`，只能从共享契约派生本地 Set 用于归一化，不得重新写 MIME 字面量清单；`npm run check:native-shells` 会拒绝 H5 facade 重新复制文本、图片或音频 MIME 边界。
 - 2026-06-18 原生壳统一验收门禁：根级 `npm run check:native-shells` 统一执行 H5 HostBridge 关键测试、Expo 壳 typecheck / test / config smoke / Metro export smoke、Tauri 壳 typecheck / cargo test、桌面 release `--no-bundle` 构建烟测，以及可分发壳与 H5 HostBridge 真实调用链的临时替身词扫描；根级 `npm run check` 会在 lint、主站测试、构建和内容检查后继续执行该门禁，避免 HostBridge、三端壳、Expo managed config、移动端 production bundle、桌面 release 入口和 H5 HostBridge 真实调用链禁替身验收散落成容易漏跑的单项命令。
 - 2026-06-19 原生壳临时替身扫描范围：`npm run check:native-shells` 的生产替身词扫描必须覆盖微信小程序壳生产 `.js`、Expo / Tauri 壳源码与配置、共享 HostBridge 契约、H5 native transport，并自动覆盖已接入真实宿主能力 facade 的 H5 生产调用链文件；新增 H5 调用点接入 HostBridge 时，必须让自动扫描覆盖对应文件或在同等门禁中证明生产代码没有 mock / fake / stub / TODO / FIXME / 模拟 / 伪造。
 - 2026-06-18 微信壳桥接层纳入统一验收：`npm run check:native-shells` 还会运行 `miniprogram/host-bridge/`、`miniprogram/shell/`、`pages/web-view` 样式和 `scripts/miniprogram-web-view-auth.test.ts` 的微信壳测试，覆盖 WebView 入口、登录触发、分享目标、支付结果、订阅消息结果和九宫切图行为；三端桥接层文件结构检查只证明目录边界，行为回归必须由同一门禁中的微信壳测试证明。
diff --git a/scripts/check-native-shells.mjs b/scripts/check-native-shells.mjs
index 20ebfa987..b6aa2b585 100644
--- a/scripts/check-native-shells.mjs
+++ b/scripts/check-native-shells.mjs
@@ -965,6 +965,52 @@ function assertH5HostBridgeEventSubscriptionGates() {
   }
 }
 
+function assertH5HostBridgePayloadBoundaries() {
+  const h5HostBridgeSource = fs.readFileSync(
+    'src/services/host-bridge/hostBridge.ts',
+    'utf8',
+  );
+
+  for (const sharedBoundary of [
+    'HOST_BRIDGE_TEXT_MIME_TYPES',
+    'HOST_BRIDGE_DOCUMENT_MIME_TYPES',
+    'HOST_BRIDGE_IMAGE_MIME_TYPES',
+    'HOST_BRIDGE_AUDIO_MIME_TYPES',
+  ]) {
+    if (!h5HostBridgeSource.includes(`${sharedBoundary},`)) {
+      throw new Error(
+        `H5 HostBridge facade must import shared payload boundary ${sharedBoundary}`,
+      );
+    }
+    if (new RegExp(`const ${sharedBoundary}\\s*=\\s*new Set`).test(h5HostBridgeSource)) {
+      throw new Error(
+        `H5 HostBridge facade must not redeclare shared payload boundary ${sharedBoundary}`,
+      );
+    }
+  }
+
+  for (const mimeLiteral of [
+    "'text/plain'",
+    "'text/markdown'",
+    "'text/csv'",
+    "'application/json'",
+    "'image/png'",
+    "'image/jpeg'",
+    "'image/webp'",
+    "'audio/mpeg'",
+    "'audio/mp4'",
+    "'audio/wav'",
+    "'audio/ogg'",
+    "'audio/webm'",
+  ]) {
+    if (h5HostBridgeSource.includes(mimeLiteral)) {
+      throw new Error(
+        `H5 HostBridge facade must read MIME boundaries from shared contract instead of ${mimeLiteral}`,
+      );
+    }
+  }
+}
+
 function extractDocumentCapabilityList(source, marker) {
   const markerIndex = source.indexOf(marker);
   if (markerIndex === -1) {
@@ -1613,6 +1659,9 @@ assertWechatMiniProgramCapabilityFlows();
 console.log('[check:native-shells] h5-host-bridge-event-subscription-gates');
 assertH5HostBridgeEventSubscriptionGates();
 
+console.log('[check:native-shells] h5-host-bridge-payload-boundaries');
+assertH5HostBridgePayloadBoundaries();
+
 console.log('[check:native-shells] production-shell-dev-scaffold-scan');
 assertNoProductionShellDevScaffoldTerms();
 
diff --git a/src/services/host-bridge/hostBridge.ts b/src/services/host-bridge/hostBridge.ts
index bf6bf4b6d..23d3b9a98 100644
--- a/src/services/host-bridge/hostBridge.ts
+++ b/src/services/host-bridge/hostBridge.ts
@@ -13,13 +13,9 @@ import type {
   FileImportImageResult,
   FileImportTextResult,
   HapticsImpactPayload,
-  HostBridgeAudioMimeType,
   HostBridgeCapability,
-  HostBridgeDocumentMimeType,
-  HostBridgeImageMimeType,
   HostBridgeMethod,
   HostBridgeRuntimeResult,
-  HostBridgeTextMimeType,
   LocalNotificationPayload,
   NavigationCanGoBackEventPayload,
   NetworkStatusResult,
@@ -29,9 +25,12 @@ import type {
   ShareOpenPayload,
 } from '../../../packages/shared/src/contracts/hostBridge';
 import {
+  HOST_BRIDGE_AUDIO_MIME_TYPES,
   HOST_BRIDGE_DOCUMENT_MIME_TYPES,
+  HOST_BRIDGE_IMAGE_MIME_TYPES,
   HOST_BRIDGE_NATIVE_APP_QUERY,
   HOST_BRIDGE_RUNTIME_CONTEXT_QUERY_KEY,
+  HOST_BRIDGE_TEXT_MIME_TYPES,
   HOST_BRIDGE_WECHAT_MINI_PROGRAM_SOURCE_QUERY,
   isHostBridgeCapability,
   normalizeHostBridgeBadgeCount,
@@ -835,11 +834,7 @@ export async function exportHostAudioFile(
   }
 }
 
-const HOST_BRIDGE_IMAGE_MIME_TYPES = new Set<HostBridgeImageMimeType>([
-  'image/png',
-  'image/jpeg',
-  'image/webp',
-]);
+const HOST_BRIDGE_IMAGE_MIME_TYPE_SET = new Set(HOST_BRIDGE_IMAGE_MIME_TYPES);
 
 function normalizeHostImageImportResult(
   payload: FileImportImageResult | null | undefined,
@@ -850,7 +845,7 @@ function normalizeHostImageImportResult(
     payload.action !== 'selected' &&
     payload.action !== 'dropped' &&
     payload.action !== 'captured' ||
-    !HOST_BRIDGE_IMAGE_MIME_TYPES.has(payload.mimeType) ||
+    !HOST_BRIDGE_IMAGE_MIME_TYPE_SET.has(payload.mimeType) ||
     typeof payload.fileName !== 'string' ||
     !payload.fileName.trim() ||
     typeof payload.base64Data !== 'string' ||
@@ -950,15 +945,8 @@ export async function scanHostQrCode() {
   }
 }
 
-const HOST_BRIDGE_TEXT_MIME_TYPES = new Set<HostBridgeTextMimeType>([
-  'text/plain',
-  'text/markdown',
-  'text/csv',
-  'application/json',
-]);
-const HOST_BRIDGE_DOCUMENT_MIME_TYPE_SET = new Set<HostBridgeDocumentMimeType>(
-  HOST_BRIDGE_DOCUMENT_MIME_TYPES,
-);
+const HOST_BRIDGE_TEXT_MIME_TYPE_SET = new Set(HOST_BRIDGE_TEXT_MIME_TYPES);
+const HOST_BRIDGE_DOCUMENT_MIME_TYPE_SET = new Set(HOST_BRIDGE_DOCUMENT_MIME_TYPES);
 
 function normalizeHostTextImportResult(
   payload: FileImportTextResult | null | undefined,
@@ -967,7 +955,7 @@ function normalizeHostTextImportResult(
     !payload ||
     typeof payload !== 'object' ||
     payload.action !== 'selected' ||
-    !HOST_BRIDGE_TEXT_MIME_TYPES.has(payload.mimeType) ||
+    !HOST_BRIDGE_TEXT_MIME_TYPE_SET.has(payload.mimeType) ||
     typeof payload.fileName !== 'string' ||
     !payload.fileName.trim() ||
     typeof payload.content !== 'string' ||
@@ -1057,13 +1045,7 @@ export async function importHostDocumentFile() {
   }
 }
 
-const HOST_BRIDGE_AUDIO_MIME_TYPES = new Set<HostBridgeAudioMimeType>([
-  'audio/mpeg',
-  'audio/mp4',
-  'audio/wav',
-  'audio/ogg',
-  'audio/webm',
-]);
+const HOST_BRIDGE_AUDIO_MIME_TYPE_SET = new Set(HOST_BRIDGE_AUDIO_MIME_TYPES);
 
 function normalizeHostAudioImportResult(
   payload: FileImportAudioResult | null | undefined,
@@ -1072,7 +1054,7 @@ function normalizeHostAudioImportResult(
     !payload ||
     typeof payload !== 'object' ||
     payload.action !== 'selected' ||
-    !HOST_BRIDGE_AUDIO_MIME_TYPES.has(payload.mimeType) ||
+    !HOST_BRIDGE_AUDIO_MIME_TYPE_SET.has(payload.mimeType) ||
     typeof payload.fileName !== 'string' ||
     !payload.fileName.trim() ||
     typeof payload.base64Data !== 'string' ||