diff --git a/apps/web/tests/plan-control-row.e2e.ts b/apps/web/tests/plan-control-row.e2e.ts
index 99146362a1..c32960a14e 100644
--- a/apps/web/tests/plan-control-row.e2e.ts
+++ b/apps/web/tests/plan-control-row.e2e.ts
@@ -256,6 +256,27 @@ describe('web e2e: plan chip click area at the narrow viewport', () => {
     expect(tripwire.warnings).toEqual([])
   }, 200_000)
 
+  // The suite above only reaches the icon through the Plan chip's width. This
+  // case keeps the row otherwise empty: a long model name must still exceed
+  // the row above the mobile minimum, so a row-relative width cap cannot hide
+  // the demand behind a shrunken, ellipsized name.
+  it('collapses the model text on a narrow composer without another control', async () => {
+    onTestFailed(() => saveFailureShot(page, 'web-e2e-model-collapse-no-plan'))
+    await page.locator('[data-composer-input]').first().waitFor({ timeout: 10_000 })
+    await resizeControls(page, 1680)
+    await selectModel(page, LONG_MODEL)
+    await expectControlLayout(page, false)
+
+    await resizeControls(page, 440)
+    await expectControlLayout(page, true)
+    const trigger = page.getByRole('button', { name: /Select model/ })
+    expect(await trigger.getAttribute('title')).toContain(LONG_MODEL)
+    expect(await trigger.getAttribute('aria-label')).toContain(LONG_MODEL)
+
+    await resizeControls(page, 1680)
+    await expectControlLayout(page, false)
+  }, 120_000)
+
   it('keeps the snapshot inventory closed', async () => {
     await assertFixtureInventory(SNAPSHOT_DIR, ['session.v3.jsonl'])
   })
diff --git a/packages/client/ui-conversation/README.i18n.yaml b/packages/client/ui-conversation/README.i18n.yaml
index 9fab887a2d..dac053ef6d 100644
--- a/packages/client/ui-conversation/README.i18n.yaml
+++ b/packages/client/ui-conversation/README.i18n.yaml
@@ -21,8 +21,8 @@
   en: 7871f9fe6bcc4459
   zh: 0d51565c600b3958
 /deepseek-ai-dsh-client-ui-conversation/shell-and-standard-props:
-  en: 5a9264158ebf0033
-  zh: b74e5807ed883ef6
+  en: d0ff0a313e92df44
+  zh: 5a2a44347348dc6b
 /deepseek-ai-dsh-client-ui-conversation/temporary-composer-entries:
   en: bb1244310f5c0382
   zh: 824b84077432b559
diff --git a/packages/client/ui-conversation/README.md b/packages/client/ui-conversation/README.md
index fa5cefcb5d..c9dd773287 100644
--- a/packages/client/ui-conversation/README.md
+++ b/packages/client/ui-conversation/README.md
@@ -72,7 +72,7 @@ The shared image slot props keep display choices separate from durable reference
 
 The composer uses a minimum 16px draft font on coarse-pointer devices to avoid focus-triggered browser zoom; larger font preferences still apply.
 
-The composer measures its expanded control groups after size, content, visibility, or font-loading changes. If they cannot share a line, the row sets `--dsh-composer-model-text-display: none` and `--dsh-composer-model-icon-display: block` for the model seat; their defaults are `block` and `none`. Wrapping remains available if even the icon cannot fit.
+The composer measures its expanded control groups after size, content, visibility, or font-loading changes. If they cannot share a line, the row sets `--dsh-composer-model-text-display: none` and `--dsh-composer-model-icon-display: block` for the model seat; their defaults are `block` and `none`. The model seat is measured at its content width, capped at 360px, rather than at a share of the row, so a long name stays visible in the measurement. Wrapping remains available if even the icon cannot fit.
 
 The context meter follows the [statistics-control radius](../../../docs/ui-radius.md#radius-scale).
 
diff --git a/packages/client/ui-conversation/README.zh.md b/packages/client/ui-conversation/README.zh.md
index ddb05c8654..b7dd399079 100644
--- a/packages/client/ui-conversation/README.zh.md
+++ b/packages/client/ui-conversation/README.zh.md
@@ -72,7 +72,7 @@ Queue 预览启用空白折叠和文档边缘 trim，保留 emoji，并使用 CS
 
 在粗指针设备上，composer 的草稿字号至少为 16px，以避免获得焦点时浏览器自动放大；更大的字号偏好仍然生效。
 
-控件组的尺寸、内容、可见性或字体加载状态变化后，composer 测量展开状态下的控件组。若无法排在同一行，控制栏为模型位设置 `--dsh-composer-model-text-display: none` 和 `--dsh-composer-model-icon-display: block`；两者默认值分别为 `block` 和 `none`。若连图标也放不下，仍允许换行。
+控件组的尺寸、内容、可见性或字体加载状态变化后，composer 测量展开状态下的控件组。若无法排在同一行，控制栏为模型位设置 `--dsh-composer-model-text-display: none` 和 `--dsh-composer-model-icon-display: block`；两者默认值分别为 `block` 和 `none`。模型位按内容宽度（最多 360px）参与测量，而不是按行宽比例，因此长模型名在测量中保持可见。若连图标也放不下，仍允许换行。
 
 上下文占用率入口遵循[统计控件圆角规则](../../../docs/ui-radius.zh.md#radius-scale)。
 
diff --git a/packages/client/ui-model-selection/src/client/ModelSelect.module.css b/packages/client/ui-model-selection/src/client/ModelSelect.module.css
index 76532308c9..a4fbb31611 100644
--- a/packages/client/ui-model-selection/src/client/ModelSelect.module.css
+++ b/packages/client/ui-model-selection/src/client/ModelSelect.module.css
@@ -11,10 +11,11 @@
   align-items: center;
   gap: 4px;
   min-width: 0;
-  /* Legacy fallback, then a row-relative cap that grants long names more
-     room without letting this trailing control consume the composer. */
-  max-width: 220px;
-  max-width: min(360px, 45cqw);
+  /* Preferred width: the composer measures this expanded seat against the
+     space the other controls leave, so the cap must not shrink with the row.
+     A row-relative cap would let the measured demand fall with the available
+     width, and the expanded text would then always fit. */
+  max-width: 360px;
   height: 28px;
   padding: 0 4px 0 8px;
   border: none;