diff --git a/backend/internal/service/account_usage_service.go b/backend/internal/service/account_usage_service.go
index 959c1182..6f5dd730 100644
--- a/backend/internal/service/account_usage_service.go
+++ b/backend/internal/service/account_usage_service.go
@@ -1042,6 +1042,11 @@ func buildCodexUsageProgressFromExtra(extra map[string]any, window string, now t
 		}
 	}
 
+	// 窗口已过期（resetAt 在 now 之前）→ 额度已重置，归零
+	if progress.ResetsAt != nil && !now.Before(*progress.ResetsAt) {
+		progress.Utilization = 0
+	}
+
 	return progress
 }
 
diff --git a/backend/internal/service/account_usage_service_test.go b/backend/internal/service/account_usage_service_test.go
index a063fe26..fe255225 100644
--- a/backend/internal/service/account_usage_service_test.go
+++ b/backend/internal/service/account_usage_service_test.go
@@ -148,3 +148,54 @@ func TestAccountUsageService_PersistOpenAICodexProbeSnapshotSetsRateLimit(t *tes
 		t.Fatal("waiting for codex probe rate limit persistence timed out")
 	}
 }
+
+func TestBuildCodexUsageProgressFromExtra_ZerosExpiredWindow(t *testing.T) {
+	t.Parallel()
+	now := time.Date(2026, 3, 16, 12, 0, 0, 0, time.UTC)
+
+	t.Run("expired 5h window zeroes utilization", func(t *testing.T) {
+		extra := map[string]any{
+			"codex_5h_used_percent": 42.0,
+			"codex_5h_reset_at":     "2026-03-16T10:00:00Z", // 2h ago
+		}
+		progress := buildCodexUsageProgressFromExtra(extra, "5h", now)
+		if progress == nil {
+			t.Fatal("expected non-nil progress")
+		}
+		if progress.Utilization != 0 {
+			t.Fatalf("expected Utilization=0 for expired window, got %v", progress.Utilization)
+		}
+		if progress.RemainingSeconds != 0 {
+			t.Fatalf("expected RemainingSeconds=0, got %v", progress.RemainingSeconds)
+		}
+	})
+
+	t.Run("active 5h window keeps utilization", func(t *testing.T) {
+		resetAt := now.Add(2 * time.Hour).Format(time.RFC3339)
+		extra := map[string]any{
+			"codex_5h_used_percent": 42.0,
+			"codex_5h_reset_at":     resetAt,
+		}
+		progress := buildCodexUsageProgressFromExtra(extra, "5h", now)
+		if progress == nil {
+			t.Fatal("expected non-nil progress")
+		}
+		if progress.Utilization != 42.0 {
+			t.Fatalf("expected Utilization=42, got %v", progress.Utilization)
+		}
+	})
+
+	t.Run("expired 7d window zeroes utilization", func(t *testing.T) {
+		extra := map[string]any{
+			"codex_7d_used_percent": 88.0,
+			"codex_7d_reset_at":     "2026-03-15T00:00:00Z", // yesterday
+		}
+		progress := buildCodexUsageProgressFromExtra(extra, "7d", now)
+		if progress == nil {
+			t.Fatal("expected non-nil progress")
+		}
+		if progress.Utilization != 0 {
+			t.Fatalf("expected Utilization=0 for expired 7d window, got %v", progress.Utilization)
+		}
+	})
+}
diff --git a/frontend/src/components/account/AccountUsageCell.vue b/frontend/src/components/account/AccountUsageCell.vue
index 9c145530..e548be8c 100644
--- a/frontend/src/components/account/AccountUsageCell.vue
+++ b/frontend/src/components/account/AccountUsageCell.vue
@@ -73,7 +73,7 @@
       <div v-else class="text-xs text-gray-400">-</div>
     </template>
 
-    <!-- OpenAI OAuth accounts: prefer fresh usage query for active rate-limited rows -->
+    <!-- OpenAI OAuth accounts: single source from /usage API -->
     <template v-else-if="account.platform === 'openai' && account.type === 'oauth'">
       <div v-if="hasOpenAIUsageFallback" class="space-y-1">
         <UsageProgressBar
@@ -93,37 +93,6 @@
           color="emerald"
         />
       </div>
-      <div v-else-if="isActiveOpenAIRateLimited && loading" class="space-y-1.5">
-        <div class="flex items-center gap-1">
-          <div class="h-3 w-[32px] animate-pulse rounded bg-gray-200 dark:bg-gray-700"></div>
-          <div class="h-1.5 w-8 animate-pulse rounded-full bg-gray-200 dark:bg-gray-700"></div>
-          <div class="h-3 w-[32px] animate-pulse rounded bg-gray-200 dark:bg-gray-700"></div>
-        </div>
-        <div class="flex items-center gap-1">
-          <div class="h-3 w-[32px] animate-pulse rounded bg-gray-200 dark:bg-gray-700"></div>
-          <div class="h-1.5 w-8 animate-pulse rounded-full bg-gray-200 dark:bg-gray-700"></div>
-          <div class="h-3 w-[32px] animate-pulse rounded bg-gray-200 dark:bg-gray-700"></div>
-        </div>
-      </div>
-      <div v-else-if="hasCodexUsage" class="space-y-1">
-        <!-- 5h Window -->
-        <UsageProgressBar
-          v-if="codex5hUsedPercent !== null"
-          label="5h"
-          :utilization="codex5hUsedPercent"
-          :resets-at="codex5hResetAt"
-          color="indigo"
-        />
-
-        <!-- 7d Window -->
-        <UsageProgressBar
-          v-if="codex7dUsedPercent !== null"
-          label="7d"
-          :utilization="codex7dUsedPercent"
-          :resets-at="codex7dResetAt"
-          color="emerald"
-        />
-      </div>
       <div v-else-if="loading" class="space-y-1.5">
         <div class="flex items-center gap-1">
           <div class="h-3 w-[32px] animate-pulse rounded bg-gray-200 dark:bg-gray-700"></div>
@@ -441,7 +410,6 @@ import { useI18n } from 'vue-i18n'
 import { adminAPI } from '@/api/admin'
 import type { Account, AccountUsageInfo, GeminiCredentials, WindowStats } from '@/types'
 import { buildOpenAIUsageRefreshKey } from '@/utils/accountUsageRefresh'
-import { resolveCodexUsageWindow } from '@/utils/codexUsage'
 import { formatCompactNumber } from '@/utils/format'
 import UsageProgressBar from './UsageProgressBar.vue'
 import AccountQuotaInfo from './AccountQuotaInfo.vue'
@@ -500,37 +468,17 @@ const geminiUsageAvailable = computed(() => {
   )
 })
 
-const codex5hWindow = computed(() => resolveCodexUsageWindow(props.account.extra, '5h'))
-const codex7dWindow = computed(() => resolveCodexUsageWindow(props.account.extra, '7d'))
-
-// OpenAI Codex usage computed properties
-const hasCodexUsage = computed(() => {
-  return codex5hWindow.value.usedPercent !== null || codex7dWindow.value.usedPercent !== null
-})
-
 const hasOpenAIUsageFallback = computed(() => {
   if (props.account.platform !== 'openai' || props.account.type !== 'oauth') return false
   return !!usageInfo.value?.five_hour || !!usageInfo.value?.seven_day
 })
 
-const isActiveOpenAIRateLimited = computed(() => {
-  if (props.account.platform !== 'openai' || props.account.type !== 'oauth') return false
-  if (!props.account.rate_limit_reset_at) return false
-  const resetAt = Date.parse(props.account.rate_limit_reset_at)
-  return !Number.isNaN(resetAt) && resetAt > Date.now()
-})
-
 const openAIUsageRefreshKey = computed(() => buildOpenAIUsageRefreshKey(props.account))
 
 const shouldAutoLoadUsageOnMount = computed(() => {
   return shouldFetchUsage.value
 })
 
-const codex5hUsedPercent = computed(() => codex5hWindow.value.usedPercent)
-const codex5hResetAt = computed(() => codex5hWindow.value.resetAt)
-const codex7dUsedPercent = computed(() => codex7dWindow.value.usedPercent)
-const codex7dResetAt = computed(() => codex7dWindow.value.resetAt)
-
 // Antigravity quota types (用于 API 返回的数据)
 interface AntigravityUsageResult {
   utilization: number
diff --git a/frontend/src/components/account/__tests__/AccountUsageCell.spec.ts b/frontend/src/components/account/__tests__/AccountUsageCell.spec.ts
index e8fc5346..9158da64 100644
--- a/frontend/src/components/account/__tests__/AccountUsageCell.spec.ts
+++ b/frontend/src/components/account/__tests__/AccountUsageCell.spec.ts
@@ -198,7 +198,7 @@ describe('AccountUsageCell', () => {
     expect(wrapper.text()).toContain('7d|77|300')
   })
 
-  it('OpenAI OAuth 有现成快照时首屏先显示快照再加载 usage 覆盖', async () => {
+  it('OpenAI OAuth 有 codex 快照时仍然使用 /usage API 数据渲染', async () => {
     getUsage.mockResolvedValue({
       five_hour: {
         utilization: 18,
@@ -254,8 +254,8 @@ describe('AccountUsageCell', () => {
 
     await flushPromises()
 
-    // 始终拉 usage，fetched data 优先显示（包含 window_stats）
     expect(getUsage).toHaveBeenCalledWith(2001)
+    // 单一数据源：始终使用 /usage API 返回值，忽略 codex 快照
     expect(wrapper.text()).toContain('5h|18|900')
     expect(wrapper.text()).toContain('7d|36|900')
   })
@@ -326,7 +326,7 @@ describe('AccountUsageCell', () => {
     // 手动刷新再拉一次
     expect(getUsage).toHaveBeenCalledTimes(2)
     expect(getUsage).toHaveBeenCalledWith(2010)
-    // fetched data 优先显示，包含 window_stats
+    // 单一数据源：始终使用 /usage API 值
     expect(wrapper.text()).toContain('5h|18|900')
   })
 
@@ -458,7 +458,7 @@ describe('AccountUsageCell', () => {
 	expect(wrapper.text()).toContain('5h|0|200')
   })
 
-  it('OpenAI OAuth 已限额时首屏优先展示重新查询后的 usage，而不是旧 codex 快照', async () => {
+  it('OpenAI OAuth 已限额时显示 /usage API 返回的限额数据', async () => {
 	getUsage.mockResolvedValue({
 	  five_hour: {
 	    utilization: 100,
@@ -515,7 +515,6 @@ describe('AccountUsageCell', () => {
   expect(getUsage).toHaveBeenCalledWith(2004)
   expect(wrapper.text()).toContain('5h|100|106540000')
   expect(wrapper.text()).toContain('7d|100|106540000')
-  expect(wrapper.text()).not.toContain('5h|0|')
   })
 
   it('Key 账号会展示 today stats 徽章并带 A/U 提示', async () => {
diff --git a/frontend/src/utils/__tests__/codexUsage.spec.ts b/frontend/src/utils/__tests__/codexUsage.spec.ts
deleted file mode 100644
index cea8abe2..00000000
--- a/frontend/src/utils/__tests__/codexUsage.spec.ts
+++ /dev/null
@@ -1,206 +0,0 @@
-import { describe, expect, it } from 'vitest'
-import { resolveCodexUsageWindow } from '@/utils/codexUsage'
-
-describe('resolveCodexUsageWindow', () => {
-  it('快照为空时返回空窗口', () => {
-    const result = resolveCodexUsageWindow(null, '5h', new Date('2026-02-20T08:00:00Z'))
-    expect(result).toEqual({ usedPercent: null, resetAt: null })
-  })
-
-  it('优先使用后端提供的绝对重置时间', () => {
-    const now = new Date('2026-02-20T08:00:00Z')
-    const result = resolveCodexUsageWindow(
-      {
-        codex_5h_used_percent: 55,
-        codex_5h_reset_at: '2026-02-20T10:00:00Z',
-        codex_5h_reset_after_seconds: 1
-      },
-      '5h',
-      now
-    )
-
-    expect(result.usedPercent).toBe(55)
-    expect(result.resetAt).toBe('2026-02-20T10:00:00.000Z')
-  })
-
-  it('窗口已过期时自动归零', () => {
-    const now = new Date('2026-02-20T08:00:00Z')
-    const result = resolveCodexUsageWindow(
-      {
-        codex_7d_used_percent: 100,
-        codex_7d_reset_at: '2026-02-20T07:00:00Z'
-      },
-      '7d',
-      now
-    )
-
-    expect(result.usedPercent).toBe(0)
-    expect(result.resetAt).toBe('2026-02-20T07:00:00.000Z')
-  })
-
-  it('无绝对时间时使用 updated_at + seconds 回退计算', () => {
-    const now = new Date('2026-02-20T07:00:00Z')
-    const result = resolveCodexUsageWindow(
-      {
-        codex_5h_used_percent: 20,
-        codex_5h_reset_after_seconds: 3600,
-        codex_usage_updated_at: '2026-02-20T06:30:00Z'
-      },
-      '5h',
-      now
-    )
-
-    expect(result.usedPercent).toBe(20)
-    expect(result.resetAt).toBe('2026-02-20T07:30:00.000Z')
-  })
-
-  it('支持 legacy primary/secondary 字段映射', () => {
-    const now = new Date('2026-02-20T07:05:00Z')
-    const result5h = resolveCodexUsageWindow(
-      {
-        codex_primary_window_minutes: 10080,
-        codex_primary_used_percent: 70,
-        codex_primary_reset_after_seconds: 86400,
-        codex_secondary_window_minutes: 300,
-        codex_secondary_used_percent: 15,
-        codex_secondary_reset_after_seconds: 1200,
-        codex_usage_updated_at: '2026-02-20T07:00:00Z'
-      },
-      '5h',
-      now
-    )
-    const result7d = resolveCodexUsageWindow(
-      {
-        codex_primary_window_minutes: 10080,
-        codex_primary_used_percent: 70,
-        codex_primary_reset_after_seconds: 86400,
-        codex_secondary_window_minutes: 300,
-        codex_secondary_used_percent: 15,
-        codex_secondary_reset_after_seconds: 1200,
-        codex_usage_updated_at: '2026-02-20T07:00:00Z'
-      },
-      '7d',
-      now
-    )
-
-    expect(result5h.usedPercent).toBe(15)
-    expect(result5h.resetAt).toBe('2026-02-20T07:20:00.000Z')
-    expect(result7d.usedPercent).toBe(70)
-    expect(result7d.resetAt).toBe('2026-02-21T07:00:00.000Z')
-  })
-
-  it('legacy 5h 在 primary<=360 时优先 primary 并支持字符串数字', () => {
-    const result = resolveCodexUsageWindow(
-      {
-        codex_primary_window_minutes: '300',
-        codex_primary_used_percent: '21',
-        codex_primary_reset_after_seconds: '1800',
-        codex_secondary_window_minutes: '10080',
-        codex_secondary_used_percent: '99',
-        codex_secondary_reset_after_seconds: '99999',
-        codex_usage_updated_at: '2026-02-20T08:00:00Z'
-      },
-      '5h',
-      new Date('2026-02-20T08:10:00Z')
-    )
-
-    expect(result.usedPercent).toBe(21)
-    expect(result.resetAt).toBe('2026-02-20T08:30:00.000Z')
-  })
-
-  it('legacy 5h 在无窗口信息时回退 secondary', () => {
-    const result = resolveCodexUsageWindow(
-      {
-        codex_secondary_used_percent: 19,
-        codex_secondary_reset_after_seconds: 120,
-        codex_usage_updated_at: '2026-02-20T08:00:00Z'
-      },
-      '5h',
-      new Date('2026-02-20T08:00:01Z')
-    )
-
-    expect(result.usedPercent).toBe(19)
-    expect(result.resetAt).toBe('2026-02-20T08:02:00.000Z')
-  })
-
-  it('legacy 场景下 secondary 为 7d 时能正确识别', () => {
-    const now = new Date('2026-02-20T07:30:00Z')
-    const result = resolveCodexUsageWindow(
-      {
-        codex_primary_window_minutes: 300,
-        codex_primary_used_percent: 5,
-        codex_primary_reset_after_seconds: 600,
-        codex_secondary_window_minutes: 10080,
-        codex_secondary_used_percent: 66,
-        codex_secondary_reset_after_seconds: 7200,
-        codex_usage_updated_at: '2026-02-20T07:00:00Z'
-      },
-      '7d',
-      now
-    )
-
-    expect(result.usedPercent).toBe(66)
-    expect(result.resetAt).toBe('2026-02-20T09:00:00.000Z')
-  })
-
-  it('绝对时间非法时回退到 updated_at + seconds', () => {
-    const now = new Date('2026-02-20T07:40:00Z')
-    const result = resolveCodexUsageWindow(
-      {
-        codex_5h_used_percent: 33,
-        codex_5h_reset_at: 'not-a-date',
-        codex_5h_reset_after_seconds: 900,
-        codex_usage_updated_at: '2026-02-20T07:30:00Z'
-      },
-      '5h',
-      now
-    )
-
-    expect(result.usedPercent).toBe(33)
-    expect(result.resetAt).toBe('2026-02-20T07:45:00.000Z')
-  })
-
-  it('updated_at 非法且无绝对时间时 resetAt 返回 null', () => {
-    const result = resolveCodexUsageWindow(
-      {
-        codex_5h_used_percent: 10,
-        codex_5h_reset_after_seconds: 123,
-        codex_usage_updated_at: 'invalid-time'
-      },
-      '5h',
-      new Date('2026-02-20T08:00:00Z')
-    )
-
-    expect(result.usedPercent).toBe(10)
-    expect(result.resetAt).toBeNull()
-  })
-
-  it('reset_after_seconds 为负数时按 0 秒处理', () => {
-    const result = resolveCodexUsageWindow(
-      {
-        codex_5h_used_percent: 80,
-        codex_5h_reset_after_seconds: -30,
-        codex_usage_updated_at: '2026-02-20T08:00:00Z'
-      },
-      '5h',
-      new Date('2026-02-20T07:59:00Z')
-    )
-
-    expect(result.usedPercent).toBe(80)
-    expect(result.resetAt).toBe('2026-02-20T08:00:00.000Z')
-  })
-
-  it('百分比缺失时仍可计算 resetAt 供倒计时展示', () => {
-    const result = resolveCodexUsageWindow(
-      {
-        codex_7d_reset_after_seconds: 60,
-        codex_usage_updated_at: '2026-02-20T08:00:00Z'
-      },
-      '7d',
-      new Date('2026-02-20T08:00:01Z')
-    )
-
-    expect(result.usedPercent).toBeNull()
-    expect(result.resetAt).toBe('2026-02-20T08:01:00.000Z')
-  })
-})
diff --git a/frontend/src/utils/codexUsage.ts b/frontend/src/utils/codexUsage.ts
deleted file mode 100644
index abe09d74..00000000
--- a/frontend/src/utils/codexUsage.ts
+++ /dev/null
@@ -1,130 +0,0 @@
-import type { CodexUsageSnapshot } from '@/types'
-
-export interface ResolvedCodexUsageWindow {
-  usedPercent: number | null
-  resetAt: string | null
-}
-
-type WindowKind = '5h' | '7d'
-
-function asNumber(value: unknown): number | null {
-  if (typeof value === 'number' && Number.isFinite(value)) return value
-  if (typeof value === 'string' && value.trim() !== '') {
-    const n = Number(value)
-    if (Number.isFinite(n)) return n
-  }
-  return null
-}
-
-function asString(value: unknown): string | null {
-  if (typeof value !== 'string') return null
-  const trimmed = value.trim()
-  return trimmed === '' ? null : trimmed
-}
-
-function asISOTime(value: unknown): string | null {
-  const raw = asString(value)
-  if (!raw) return null
-  const date = new Date(raw)
-  if (Number.isNaN(date.getTime())) return null
-  return date.toISOString()
-}
-
-function resolveLegacy5h(snapshot: Record<string, unknown>): { used: number | null; resetAfterSeconds: number | null } {
-  const primaryWindow = asNumber(snapshot.codex_primary_window_minutes)
-  const secondaryWindow = asNumber(snapshot.codex_secondary_window_minutes)
-  const primaryUsed = asNumber(snapshot.codex_primary_used_percent)
-  const secondaryUsed = asNumber(snapshot.codex_secondary_used_percent)
-  const primaryReset = asNumber(snapshot.codex_primary_reset_after_seconds)
-  const secondaryReset = asNumber(snapshot.codex_secondary_reset_after_seconds)
-
-  if (primaryWindow != null && primaryWindow <= 360) {
-    return { used: primaryUsed, resetAfterSeconds: primaryReset }
-  }
-  if (secondaryWindow != null && secondaryWindow <= 360) {
-    return { used: secondaryUsed, resetAfterSeconds: secondaryReset }
-  }
-  return { used: secondaryUsed, resetAfterSeconds: secondaryReset }
-}
-
-function resolveLegacy7d(snapshot: Record<string, unknown>): { used: number | null; resetAfterSeconds: number | null } {
-  const primaryWindow = asNumber(snapshot.codex_primary_window_minutes)
-  const secondaryWindow = asNumber(snapshot.codex_secondary_window_minutes)
-  const primaryUsed = asNumber(snapshot.codex_primary_used_percent)
-  const secondaryUsed = asNumber(snapshot.codex_secondary_used_percent)
-  const primaryReset = asNumber(snapshot.codex_primary_reset_after_seconds)
-  const secondaryReset = asNumber(snapshot.codex_secondary_reset_after_seconds)
-
-  if (primaryWindow != null && primaryWindow >= 10000) {
-    return { used: primaryUsed, resetAfterSeconds: primaryReset }
-  }
-  if (secondaryWindow != null && secondaryWindow >= 10000) {
-    return { used: secondaryUsed, resetAfterSeconds: secondaryReset }
-  }
-  return { used: primaryUsed, resetAfterSeconds: primaryReset }
-}
-
-function resolveFromSeconds(snapshot: Record<string, unknown>, resetAfterSeconds: number | null): string | null {
-  if (resetAfterSeconds == null) return null
-
-  const baseRaw = asString(snapshot.codex_usage_updated_at)
-  const base = baseRaw ? new Date(baseRaw) : new Date()
-  if (Number.isNaN(base.getTime())) {
-    return null
-  }
-
-  const sec = Math.max(0, resetAfterSeconds)
-  const resetAt = new Date(base.getTime() + sec * 1000)
-  return resetAt.toISOString()
-}
-
-function applyExpiredRule(window: ResolvedCodexUsageWindow, now: Date): ResolvedCodexUsageWindow {
-  if (window.usedPercent == null || !window.resetAt) return window
-  const resetDate = new Date(window.resetAt)
-  if (Number.isNaN(resetDate.getTime())) return window
-  if (resetDate.getTime() <= now.getTime()) {
-    return { usedPercent: 0, resetAt: resetDate.toISOString() }
-  }
-  return window
-}
-
-export function resolveCodexUsageWindow(
-  snapshot: (CodexUsageSnapshot & Record<string, unknown>) | null | undefined,
-  window: WindowKind,
-  now: Date = new Date()
-): ResolvedCodexUsageWindow {
-  if (!snapshot) {
-    return { usedPercent: null, resetAt: null }
-  }
-
-  const typedSnapshot = snapshot as Record<string, unknown>
-  let usedPercent: number | null
-  let resetAfterSeconds: number | null
-  let resetAt: string | null
-
-  if (window === '5h') {
-    usedPercent = asNumber(typedSnapshot.codex_5h_used_percent)
-    resetAfterSeconds = asNumber(typedSnapshot.codex_5h_reset_after_seconds)
-    resetAt = asISOTime(typedSnapshot.codex_5h_reset_at)
-    if (usedPercent == null || (resetAfterSeconds == null && !resetAt)) {
-      const legacy = resolveLegacy5h(typedSnapshot)
-      if (usedPercent == null) usedPercent = legacy.used
-      if (resetAfterSeconds == null) resetAfterSeconds = legacy.resetAfterSeconds
-    }
-  } else {
-    usedPercent = asNumber(typedSnapshot.codex_7d_used_percent)
-    resetAfterSeconds = asNumber(typedSnapshot.codex_7d_reset_after_seconds)
-    resetAt = asISOTime(typedSnapshot.codex_7d_reset_at)
-    if (usedPercent == null || (resetAfterSeconds == null && !resetAt)) {
-      const legacy = resolveLegacy7d(typedSnapshot)
-      if (usedPercent == null) usedPercent = legacy.used
-      if (resetAfterSeconds == null) resetAfterSeconds = legacy.resetAfterSeconds
-    }
-  }
-
-  if (!resetAt) {
-    resetAt = resolveFromSeconds(typedSnapshot, resetAfterSeconds)
-  }
-
-  return applyExpiredRule({ usedPercent, resetAt }, now)
-}