diff --git a/apps/ai-game-creator-shell/src/styles.css b/apps/ai-game-creator-shell/src/styles.css
index 10bd15886..96fca92e0 100644
--- a/apps/ai-game-creator-shell/src/styles.css
+++ b/apps/ai-game-creator-shell/src/styles.css
@@ -9897,6 +9897,14 @@ iframe.preview-frame {
   margin-left: auto;
 }
 
+/* 模型选择钮在控制排里按流式排布，但它同时是**弹层锚点**：`.conversation-model-menu`
+   （`bottom: calc(100% + 8px)`）与模型提示（`[role='alert'] / [role='status']`，
+   `bottom: 36px`）都是 `position: absolute`，包含块必须是这颗容器。这里原来写的是
+   `position: static !important`（当初为抵消上面那条遗留的「模型选择钮绝对定位」规则），
+   锚点于是回落到最近的有定位祖先——也就是 `position: absolute` 的 composer 盒子：
+   菜单跑到**整个 composer 上方**、和触发钮之间隔着整个输入区，输入区一变高（多行、
+   引用 chip、AI 润色）菜单与提示就跟着往上飘，看起来就是"编辑框把弹层挤开了"。
+   `relative` 不会把它移出控制排（`right/bottom: auto` 仍在原位），只补回锚点。 */
 .game-workbench-chat
   .project-supervisor-surface.is-direct-codex
   .project-supervisor-composer.is-direct-codex
@@ -9904,7 +9912,7 @@ iframe.preview-frame {
   .conversation-model-select {
   flex: 0 1 auto;
   min-width: 0;
-  position: static !important;
+  position: relative !important;
   right: auto !important;
   bottom: auto !important;
   max-width: 180px;
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 3ab9fa620..5eac03e00 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
@@ -5763,6 +5763,66 @@ export function registerProjectSupervisorSurfaceTests() {
     await waitFor(() => expect(trigger.textContent).toContain('快速'));
   });
 
+  it('anchors the model dropdown to its own trigger instead of the composer box', () => {
+    const styles = readFileSync(
+      resolve(process.cwd(), 'apps/ai-game-creator-shell/src/styles.css'),
+      'utf8',
+    );
+
+    // 弹层自己不参与父容器流式布局：菜单与模型提示都是 absolute，打开它不会给控制排
+    // 添一个流式子节点（"弹层撑高容器 / 把同排元素挤开"这一类问题的前提）。
+    const menu = styleRuleBody(styles, '\\.conversation-model-menu');
+    expect(menu).toMatch(/position:\s*absolute/u);
+    expect(menu).toMatch(/bottom:\s*calc\(100%\s*\+\s*\d+px\)/u);
+    expect(menu).toMatch(/right:\s*0/u);
+    const actionNotice = styleRuleBody(
+      styles,
+      "\\.conversation-model-select \\[role='status'\\]",
+    );
+    expect(actionNotice).toMatch(/position:\s*absolute/u);
+
+    // 锚点：direct-codex 控制排里的模型选择钮容器必须是**有定位**的，否则上面两个
+    // absolute 弹层的包含块会回落到 `position: absolute` 的 composer 盒子——菜单就会
+    // 跑到整个 composer 上方，和触发钮之间隔着输入区，输入区一变高菜单跟着往上飘。
+    const anchor = styleRuleBody(
+      styles,
+      '\\.project-supervisor-composer-controls\\s+\\n?\\s*\\.conversation-model-select',
+    );
+    expect(anchor).toMatch(/position:\s*relative\s*!important/u);
+    expect(anchor).not.toMatch(/position:\s*static/u);
+    // 补锚点不能把它移出控制排：仍在原位（right/bottom auto）、仍可被压缩换行。
+    expect(anchor).toMatch(/right:\s*auto/u);
+    expect(anchor).toMatch(/bottom:\s*auto/u);
+    expect(anchor).toMatch(/flex:\s*0 1 auto/u);
+    expect(anchor).toMatch(/min-width:\s*0/u);
+
+    // 输入区高度变化不得推动同排操作元素：composer 是底边锚定的两行网格，输入区占第一
+    // 行、控制排占第二行；输入区从 96px 长到 140px 只把 composer 顶边抬高，控制排仍钉在
+    // composer 底边（`bottom: 12px`），发送钮与模型选择钮不动。
+    const composer = styleRuleBody(
+      styles,
+      '\\.game-workbench-chat\\s+\\.project-supervisor-surface\\.is-direct-codex\\s+\\.project-supervisor-composer\\.is-direct-codex',
+    );
+    expect(composer).toMatch(/position:\s*absolute/u);
+    expect(styleNumber(composer, 'bottom')).toBeGreaterThan(0);
+    expect(composer).toMatch(/grid-template-rows:\s*auto auto/u);
+    // 控制排是单行 flex、不换行：窄屏下靠可压缩的模型选择钮（flex 0 1 auto + min-width 0）
+    // 收窄，而不是把模型选择钮/发送钮挤到第二行。
+    const controls = styleRuleBody(
+      styles,
+      '\\.project-supervisor-composer-controls',
+    );
+    expect(controls).toMatch(/display:\s*flex/u);
+    expect(controls).not.toMatch(/flex-wrap/u);
+    // `@` 引用钮与发送钮共用一条尺寸规则（同一规则体里两个选择器），都必须不可压缩，
+    // 这样窄屏下被压的是可收缩的模型选择钮，而不是把这两个方钮挤出这一行。
+    const controlsButtons = styleRuleBody(
+      styles,
+      '\\.project-supervisor-composer-controls\\s+\\n?\\s*\\.project-supervisor-submit-button',
+    );
+    expect(controlsButtons).toMatch(/flex:\s*0 0 30px/u);
+  });
+
   it('runs a top workbench play request without a second confirmation', async () => {
     const projectPath = '/tmp/top-play-request';
     const supervisorHarness = createProjectSupervisorRuntimeHarness({
diff --git a/apps/ai-game-creator-shell/tests/conversationModelSelect.test.tsx b/apps/ai-game-creator-shell/tests/conversationModelSelect.test.tsx
index 25b1372f8..4a9c7731f 100644
--- a/apps/ai-game-creator-shell/tests/conversationModelSelect.test.tsx
+++ b/apps/ai-game-creator-shell/tests/conversationModelSelect.test.tsx
@@ -127,6 +127,32 @@ test('a failed save keeps submission unavailable', async () => {
   expect(onReady).toHaveBeenLastCalledWith(false);
 });
 
+test('keeps the open menu inside its own trigger container, not the control row', async () => {
+  const onReady = vi.fn();
+  const { container } = render(
+    <>
+      <div className="project-supervisor-composer-controls-right">
+        <ConversationModelSelect disabled={false} onReady={onReady} />
+      </div>
+    </>,
+  );
+  await screen.findByRole('button', { name: '对话模型' });
+  fireEvent.click(screen.getByRole('button', { name: '对话模型' }));
+
+  // 弹层必须留在触发钮自己那颗容器里：它是 absolute + bottom: 100% 的浮层，锚点由这颗
+  // 容器提供；一旦被挪到控制排（或其它同排容器）当流式子节点，就会参与那一排的布局。
+  const modelSelect = container.querySelector('.conversation-model-select');
+  expect(modelSelect).not.toBeNull();
+  expect(
+    modelSelect?.querySelector(':scope > .conversation-model-menu'),
+  ).not.toBeNull();
+  expect(
+    container.querySelector(
+      '.project-supervisor-composer-controls-right > .conversation-model-menu',
+    ),
+  ).toBeNull();
+});
+
 test('closes the menu when clicking outside', async () => {
   const onReady = vi.fn();
   render(<ConversationModelSelect disabled={false} onReady={onReady} />);