Expose local scheduling failures in usage UI

frontend/src/features/usage/components/__tests__/HorizontalRequestTimeline.spec.ts

@@ -350,6 +350,40 @@ describe('HorizontalRequestTimeline', () => {
     expect(nodeDot?.classList.contains('status-success')).toBe(false)
   })
 
+  it('shows scheduling failure context instead of an empty trace state when no candidates exist', async () => {
+    const trace = buildTrace([])
+    trace.final_status = 'failed'
+
+    const root = mountTimeline(trace, {
+      requestStatus: 'failed',
+      overrideStatusCode: 503,
+      schedulingFailure: {
+        source: 'local_execution_runtime_miss',
+        reason: 'all_candidates_skipped',
+        reason_label: '所有候选均被跳过',
+        title: '本地调度失败：所有候选均被跳过',
+        message: '没有可用提供商支持模型 gemma-4-31b-it 的同步请求',
+        status_code: 503,
+        no_upstream_attempt: true,
+        provider_hint: {
+          id: 'provider-google-api',
+          name: 'Google API',
+        },
+        endpoint_hint: {
+          id: 'endpoint-gemini',
+          api_format: 'gemini:generate_content',
+        },
+      },
+    })
+    await nextTick()
+
+    expect(root.textContent).toContain('本地调度失败：所有候选均被跳过')
+    expect(root.textContent).toContain('没有可用提供商支持模型 gemma-4-31b-it 的同步请求')
+    expect(root.textContent).toContain('Google API')
+    expect(root.textContent).toContain('gemini:generate_content')
+    expect(root.textContent).not.toContain('暂无追踪数据')
+  })
+
   it('keeps emitted trace state active while the request lifecycle is still streaming', async () => {
     const onTraceState = vi.fn()
     const trace = buildTrace([

frontend/src/features/usage/components/__tests__/UsageRecordsTable.spec.ts

@@ -247,6 +247,31 @@ describe('UsageRecordsTable', () => {
     expect(root.textContent).not.toContain('等待中')
   })
 
+  it('uses scheduling failure provider hints instead of rendering unknown provider', () => {
+    const root = mountUsageRecordsTable([buildRecord({
+      provider: 'unknown',
+      status: 'failed',
+      status_code: 503,
+      scheduling_failure: {
+        source: 'local_execution_runtime_miss',
+        reason: 'all_candidates_skipped',
+        reason_label: '所有候选均被跳过',
+        title: '本地调度失败：所有候选均被跳过',
+        message: '没有可用提供商支持模型 gemma-4-31b-it 的同步请求',
+        status_code: 503,
+        no_upstream_attempt: true,
+        provider_hint: {
+          id: 'provider-google-api',
+          name: 'Google API',
+        },
+      },
+    } as Partial<UsageRecord>)])
+
+    expect(root.textContent).toContain('Google API')
+    expect(root.textContent).toContain('所有候选均被跳过')
+    expect(root.textContent).not.toContain('unknown')
+  })
+
   it('renders output TPS in the non-admin usage table', () => {
     const root = mountUsageRecordsTable([buildRecord()], { isAdmin: false })