diff --git a/apps/ai-game-creator-shell/src/styles.css b/apps/ai-game-creator-shell/src/styles.css
index 96fca92e0..756394e86 100644
--- a/apps/ai-game-creator-shell/src/styles.css
+++ b/apps/ai-game-creator-shell/src/styles.css
@@ -9607,6 +9607,12 @@ iframe.preview-frame {
   display: grid;
   min-width: 150px;
   max-width: 190px;
+  /* 条目多时菜单不能无限长：240px 与视口 40vh 取小者，超出部分在菜单内滚动
+     （窄屏 / 移动端优先下 40vh 更稳）。滚动不外溢给背后的消息列表，与
+     `.resource-reference-menu` 同一口径。 */
+  max-height: min(240px, 40vh);
+  overflow: auto;
+  overscroll-behavior: contain;
   padding: 5px;
   border: 1px solid var(--platform-surface-border, #e5e7eb);
   border-radius: 10px;
diff --git a/apps/ai-game-creator-shell/tests/appSurface/project-development.suite.ts b/apps/ai-game-creator-shell/tests/appSurface/project-development.suite.ts
index 5eac03e00..d8477f256 100644
--- a/apps/ai-game-creator-shell/tests/appSurface/project-development.suite.ts
+++ b/apps/ai-game-creator-shell/tests/appSurface/project-development.suite.ts
@@ -5823,6 +5823,22 @@ export function registerProjectSupervisorSurfaceTests() {
     expect(controlsButtons).toMatch(/flex:\s*0 0 30px/u);
   });
 
+  it('bounds the model dropdown height so a long catalog cannot cover the composer', () => {
+    const styles = readFileSync(
+      resolve(process.cwd(), 'apps/ai-game-creator-shell/src/styles.css'),
+      'utf8',
+    );
+    const menu = styleRuleBody(styles, '\\.conversation-model-menu');
+    // 条目多时菜单不能无限长：240px 与视口 40vh 取小者，超出部分在菜单内滚动
+    // （窄屏 / 移动端优先下 40vh 更稳）。高度有界不改锚点与流式归属，见上一条用例。
+    expect(menu).toMatch(/max-height:\s*min\(\s*240px\s*,\s*40vh\s*\)/u);
+    expect(menu).toMatch(/overflow:\s*auto/u);
+    // 菜单内滚动不传染给背后的消息列表，与 `.resource-reference-menu` 同一口径。
+    expect(menu).toMatch(/overscroll-behavior:\s*contain/u);
+    // 依旧不参与父容器流式布局。
+    expect(menu).toMatch(/position:\s*absolute/u);
+  });
+
   it('runs a top workbench play request without a second confirmation', async () => {
     const projectPath = '/tmp/top-play-request';
     const supervisorHarness = createProjectSupervisorRuntimeHarness({