diff --git a/frontend/src/components/admin/usage/UsageTable.vue b/frontend/src/components/admin/usage/UsageTable.vue
index 3b2509129b..364a3072e6 100644
--- a/frontend/src/components/admin/usage/UsageTable.vue
+++ b/frontend/src/components/admin/usage/UsageTable.vue
@@ -410,19 +410,19 @@
             <div class="text-xs font-semibold text-gray-300 mb-1">{{ t('usage.costDetails') }}</div>
             <div v-if="tooltipData && tooltipData.input_cost > 0" class="flex items-center justify-between gap-4">
               <span class="text-gray-400">{{ t('admin.usage.inputCost') }}</span>
-              <span class="font-medium text-white">${{ tooltipData.input_cost.toFixed(6) }}</span>
+              <span class="font-medium text-white">${{ tooltipData.input_cost.toFixed(8) }}</span>
             </div>
             <div v-if="tooltipData && hasImageInputCost(tooltipData)" class="flex items-center justify-between gap-4">
               <span class="text-gray-400">{{ t('usage.imageInputCost') }}</span>
-              <span class="font-medium text-fuchsia-300">${{ tooltipData.image_input_cost.toFixed(6) }}</span>
+              <span class="font-medium text-fuchsia-300">${{ tooltipData.image_input_cost.toFixed(8) }}</span>
             </div>
             <div v-if="tooltipData && tooltipData.output_cost > 0" class="flex items-center justify-between gap-4">
               <span class="text-gray-400">{{ t('admin.usage.outputCost') }}</span>
-              <span class="font-medium text-white">${{ tooltipData.output_cost.toFixed(6) }}</span>
+              <span class="font-medium text-white">${{ tooltipData.output_cost.toFixed(8) }}</span>
             </div>
             <div v-if="tooltipData && hasImageOutputCost(tooltipData)" class="flex items-center justify-between gap-4">
               <span class="text-gray-400">{{ t('usage.imageOutputCost') }}</span>
-              <span class="font-medium text-pink-300">${{ tooltipData.image_output_cost.toFixed(6) }}</span>
+              <span class="font-medium text-pink-300">${{ tooltipData.image_output_cost.toFixed(8) }}</span>
             </div>
             <!-- Token billing: show unit prices per 1M tokens -->
             <template v-if="tooltipData && !isImageUsage(tooltipData) && (!tooltipData.billing_mode || tooltipData.billing_mode === BILLING_MODE_TOKEN)">
@@ -470,24 +470,24 @@
               </div>
               <div class="flex items-center justify-between gap-4">
                 <span class="text-gray-400">{{ t('usage.imageUnitPrice') }}</span>
-                <span class="font-medium text-sky-300">${{ imageUnitPrice(tooltipData).toFixed(6) }}</span>
+                <span class="font-medium text-sky-300">${{ imageUnitPrice(tooltipData).toFixed(8) }}</span>
               </div>
               <div class="flex items-center justify-between gap-4">
                 <span class="text-gray-400">{{ t('usage.imageTotalPrice') }}</span>
-                <span class="font-medium text-white">${{ tooltipData.total_cost?.toFixed(6) || '0.000000' }}</span>
+                <span class="font-medium text-white">${{ tooltipData.total_cost?.toFixed(8) || '0.00000000' }}</span>
               </div>
             </template>
             <div v-else class="flex items-center justify-between gap-4">
               <span class="text-gray-400">{{ t('usage.unitPrice') }}</span>
-              <span class="font-medium text-sky-300">${{ tooltipData?.total_cost?.toFixed(6) || '0.000000' }}</span>
+              <span class="font-medium text-sky-300">${{ tooltipData?.total_cost?.toFixed(8) || '0.00000000' }}</span>
             </div>
             <div v-if="tooltipData && tooltipData.cache_creation_cost > 0" class="flex items-center justify-between gap-4">
               <span class="text-gray-400">{{ t('admin.usage.cacheCreationCost') }}</span>
-              <span class="font-medium text-white">${{ tooltipData.cache_creation_cost.toFixed(6) }}</span>
+              <span class="font-medium text-white">${{ tooltipData.cache_creation_cost.toFixed(8) }}</span>
             </div>
             <div v-if="tooltipData && tooltipData.cache_read_cost > 0" class="flex items-center justify-between gap-4">
               <span class="text-gray-400">{{ t('admin.usage.cacheReadCost') }}</span>
-              <span class="font-medium text-white">${{ tooltipData.cache_read_cost.toFixed(6) }}</span>
+              <span class="font-medium text-white">${{ tooltipData.cache_read_cost.toFixed(8) }}</span>
             </div>
           </div>
           <!-- Rate and Summary -->
@@ -501,11 +501,11 @@
           </div>
           <div class="flex items-center justify-between gap-6">
             <span class="text-gray-400">{{ t('usage.original') }}</span>
-            <span class="font-medium text-white">${{ tooltipData?.total_cost?.toFixed(6) || '0.000000' }}</span>
+            <span class="font-medium text-white">${{ tooltipData?.total_cost?.toFixed(8) || '0.00000000' }}</span>
           </div>
           <div class="flex items-center justify-between gap-6">
             <span class="text-gray-400">{{ t('usage.userBilled') }}</span>
-            <span class="font-semibold text-green-400">${{ tooltipData?.actual_cost?.toFixed(6) || '0.000000' }}</span>
+            <span class="font-semibold text-green-400">${{ tooltipData?.actual_cost?.toFixed(8) || '0.00000000' }}</span>
           </div>
           <!-- Account billing (separated from user billing) -->
           <template v-if="showAccountBilling">
@@ -520,7 +520,7 @@
                   total_cost: tooltipData?.total_cost,
                   account_stats_cost: tooltipData?.account_stats_cost,
                   account_rate_multiplier: tooltipData?.account_rate_multiplier,
-                }).toFixed(6) }}
+                }).toFixed(8) }}
               </span>
             </div>
           </template>
diff --git a/frontend/src/components/admin/usage/__tests__/UsageTable.spec.ts b/frontend/src/components/admin/usage/__tests__/UsageTable.spec.ts
index 3262fa0408..d915fa4c42 100644
--- a/frontend/src/components/admin/usage/__tests__/UsageTable.spec.ts
+++ b/frontend/src/components/admin/usage/__tests__/UsageTable.spec.ts
@@ -275,6 +275,53 @@ describe('admin UsageTable tooltip', () => {
     expect(text).toContain('$0.069568')
   })
 
+  it.each(['token', 'image', 'per_request'])('keeps eight decimal places in %s cost details', async (billingMode) => {
+    const row = {
+      ...baseImageRow,
+      billing_mode: billingMode,
+      image_count: billingMode === 'image' ? 2 : 0,
+      input_cost: 0.00000001,
+      image_input_cost: 0.00000002,
+      output_cost: 0.00000003,
+      image_output_cost: 0.00000004,
+      cache_creation_cost: 0.00000005,
+      cache_read_cost: 0.00000006,
+      total_cost: 0.00000022,
+      actual_cost: 0.00000042,
+      account_stats_cost: 0.00000012,
+      account_rate_multiplier: 1.5,
+    }
+    const wrapper = mount(UsageTable, {
+      props: { data: [row], loading: false, columns: [] },
+      global: { stubs: { DataTable: DataTableStub, EmptyState: true, Icon: true, Teleport: true } },
+    })
+    const triggers = wrapper.findAll('.group.relative')
+    await triggers[triggers.length - 1].trigger('mouseenter')
+    const amounts = wrapper.get('.fixed').findAll('span').map(span => span.text())
+    expect(amounts).toEqual(expect.arrayContaining([
+      '$0.00000001', '$0.00000002', '$0.00000003', '$0.00000004',
+      '$0.00000005', '$0.00000006', '$0.00000022', '$0.00000042', '$0.00000018',
+    ]))
+    if (billingMode === 'image') expect(amounts).toContain('$0.00000011')
+    wrapper.unmount()
+  })
+
+  it('uses eight decimal places for missing cost values', async () => {
+    const wrapper = mount(UsageTable, {
+      props: {
+        data: [{ ...baseImageRow, billing_mode: 'per_request', image_count: 0, total_cost: undefined, actual_cost: undefined }],
+        loading: false,
+        columns: [],
+      },
+      global: { stubs: { DataTable: DataTableStub, EmptyState: true, Icon: true, Teleport: true } },
+    })
+    const triggers = wrapper.findAll('.group.relative')
+    await triggers[triggers.length - 1].trigger('mouseenter')
+    const amounts = wrapper.get('.fixed').findAll('span').map(span => span.text()).filter(text => text.startsWith('$'))
+    expect(amounts).toEqual(['$0.00000000', '$0.00000000', '$0.00000000', '$0.00000000'])
+    wrapper.unmount()
+  })
+
   it('shows requested and upstream models separately for admin rows', () => {
     const row = {
       request_id: 'req-admin-model-1',