diff --git a/backend/internal/pkg/websearch/manager_test.go b/backend/internal/pkg/websearch/manager_test.go
index a4beef68..cbcf1b76 100644
--- a/backend/internal/pkg/websearch/manager_test.go
+++ b/backend/internal/pkg/websearch/manager_test.go
@@ -313,3 +313,11 @@ func TestNewHTTPClient_ValidSOCKS5Proxy(t *testing.T) {
 	require.NoError(t, err)
 	require.NotNil(t, c)
 }
+
+// --- ResetUsage ---
+
+func TestManager_ResetUsage_NilRedis(t *testing.T) {
+	m := NewManager(nil, nil)
+	err := m.ResetUsage(context.Background(), "brave")
+	require.NoError(t, err)
+}
diff --git a/backend/internal/service/account_stats_pricing_test.go b/backend/internal/service/account_stats_pricing_test.go
index 23409d5e..36e5eb74 100644
--- a/backend/internal/service/account_stats_pricing_test.go
+++ b/backend/internal/service/account_stats_pricing_test.go
@@ -3,7 +3,9 @@
 package service
 
 import (
+	"context"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/require"
 )
@@ -527,3 +529,243 @@ func TestTryModelFilePricing_WithCacheTokens(t *testing.T) {
 	// = 0.1 + 0.1 + 0.6 + 0.15 = 0.95
 	require.InDelta(t, 0.95, *result, 1e-12)
 }
+
+// ---------------------------------------------------------------------------
+// resolveAccountStatsCost — integration tests covering the 4-level priority chain
+// ---------------------------------------------------------------------------
+
+func TestResolveAccountStatsCost_NilChannelService(t *testing.T) {
+	result := resolveAccountStatsCost(
+		context.Background(),
+		nil, // channelService is nil
+		newTestBillingServiceWithPrices(map[string]*ModelPricing{}),
+		1, 1, "claude-sonnet-4",
+		UsageTokens{InputTokens: 100}, 1, 0.5,
+	)
+	require.Nil(t, result)
+}
+
+func TestResolveAccountStatsCost_EmptyUpstreamModel(t *testing.T) {
+	cs := newTestChannelServiceForStats(t, &Channel{
+		ID:     1,
+		Status: StatusActive,
+	}, 1, "")
+
+	result := resolveAccountStatsCost(
+		context.Background(),
+		cs,
+		newTestBillingServiceWithPrices(map[string]*ModelPricing{}),
+		1, 1, "", // empty upstream model
+		UsageTokens{InputTokens: 100}, 1, 0.5,
+	)
+	require.Nil(t, result)
+}
+
+func TestResolveAccountStatsCost_GetChannelForGroupReturnsNil(t *testing.T) {
+	// Group 99 is NOT in the cache, so GetChannelForGroup returns nil
+	cs := newTestChannelServiceForStats(t, &Channel{
+		ID:     1,
+		Status: StatusActive,
+	}, 1, "")
+
+	result := resolveAccountStatsCost(
+		context.Background(),
+		cs,
+		newTestBillingServiceWithPrices(map[string]*ModelPricing{}),
+		1, 99, "claude-sonnet-4", // groupID 99 has no channel
+		UsageTokens{InputTokens: 100}, 1, 0.5,
+	)
+	require.Nil(t, result)
+}
+
+func TestResolveAccountStatsCost_HitsCustomRule(t *testing.T) {
+	channel := &Channel{
+		ID:     1,
+		Status: StatusActive,
+		AccountStatsPricingRules: []AccountStatsPricingRule{
+			{
+				GroupIDs: []int64{10},
+				Pricing: []ChannelModelPricing{
+					{
+						ID:          100,
+						Models:      []string{"claude-sonnet-4"},
+						InputPrice:  testPtrFloat64(0.01),
+						OutputPrice: testPtrFloat64(0.02),
+					},
+				},
+			},
+		},
+	}
+	cs := newTestChannelServiceForStats(t, channel, 10, "anthropic")
+
+	tokens := UsageTokens{InputTokens: 100, OutputTokens: 50}
+
+	result := resolveAccountStatsCost(
+		context.Background(),
+		cs, nil, // billingService not needed when custom rule hits
+		1, 10, "claude-sonnet-4",
+		tokens, 1, 999.0, // totalCost ignored because custom rule hits
+	)
+	require.NotNil(t, result)
+	// 100*0.01 + 50*0.02 = 1.0 + 1.0 = 2.0
+	require.InDelta(t, 2.0, *result, 1e-12)
+}
+
+func TestResolveAccountStatsCost_ApplyPricingToAccountStats_UsesTotalCost(t *testing.T) {
+	channel := &Channel{
+		ID:                         1,
+		Status:                     StatusActive,
+		ApplyPricingToAccountStats: true,
+		// No custom rules
+	}
+	cs := newTestChannelServiceForStats(t, channel, 10, "anthropic")
+
+	tokens := UsageTokens{InputTokens: 100, OutputTokens: 50}
+
+	result := resolveAccountStatsCost(
+		context.Background(),
+		cs, nil,
+		1, 10, "claude-sonnet-4",
+		tokens, 1, 0.75, // totalCost = 0.75
+	)
+	require.NotNil(t, result)
+	require.InDelta(t, 0.75, *result, 1e-12)
+}
+
+func TestResolveAccountStatsCost_ApplyPricingToAccountStats_ZeroTotalCost_ReturnsNil(t *testing.T) {
+	channel := &Channel{
+		ID:                         1,
+		Status:                     StatusActive,
+		ApplyPricingToAccountStats: true,
+	}
+	cs := newTestChannelServiceForStats(t, channel, 10, "anthropic")
+
+	result := resolveAccountStatsCost(
+		context.Background(),
+		cs, nil,
+		1, 10, "claude-sonnet-4",
+		UsageTokens{}, 1, 0.0, // totalCost = 0
+	)
+	require.Nil(t, result)
+}
+
+func TestResolveAccountStatsCost_FallsBackToLiteLLM(t *testing.T) {
+	channel := &Channel{
+		ID:                         1,
+		Status:                     StatusActive,
+		ApplyPricingToAccountStats: false, // not enabled
+		// No custom rules
+	}
+	cs := newTestChannelServiceForStats(t, channel, 10, "anthropic")
+
+	bs := newTestBillingServiceWithPrices(map[string]*ModelPricing{
+		"claude-sonnet-4": {
+			InputPricePerToken:  0.001,
+			OutputPricePerToken: 0.002,
+		},
+	})
+
+	tokens := UsageTokens{InputTokens: 100, OutputTokens: 50}
+
+	result := resolveAccountStatsCost(
+		context.Background(),
+		cs, bs,
+		1, 10, "claude-sonnet-4",
+		tokens, 1, 999.0, // totalCost ignored
+	)
+	require.NotNil(t, result)
+	// 100*0.001 + 50*0.002 = 0.1 + 0.1 = 0.2
+	require.InDelta(t, 0.2, *result, 1e-12)
+}
+
+func TestResolveAccountStatsCost_AllMiss_ReturnsNil(t *testing.T) {
+	channel := &Channel{
+		ID:                         1,
+		Status:                     StatusActive,
+		ApplyPricingToAccountStats: false,
+		// No custom rules
+	}
+	cs := newTestChannelServiceForStats(t, channel, 10, "anthropic")
+
+	// BillingService with no pricing for the model
+	bs := newTestBillingServiceWithPrices(map[string]*ModelPricing{})
+
+	tokens := UsageTokens{InputTokens: 100, OutputTokens: 50}
+
+	result := resolveAccountStatsCost(
+		context.Background(),
+		cs, bs,
+		1, 10, "totally-unknown-model",
+		tokens, 1, 0.0,
+	)
+	require.Nil(t, result)
+}
+
+func TestResolveAccountStatsCost_NilBillingService_SkipsLiteLLM(t *testing.T) {
+	channel := &Channel{
+		ID:                         1,
+		Status:                     StatusActive,
+		ApplyPricingToAccountStats: false,
+	}
+	cs := newTestChannelServiceForStats(t, channel, 10, "anthropic")
+
+	result := resolveAccountStatsCost(
+		context.Background(),
+		cs, nil, // billingService is nil
+		1, 10, "claude-sonnet-4",
+		UsageTokens{InputTokens: 100}, 1, 0.0,
+	)
+	require.Nil(t, result)
+}
+
+func TestResolveAccountStatsCost_CustomRulePriorityOverApplyPricing(t *testing.T) {
+	// Both custom rule and ApplyPricingToAccountStats are configured;
+	// custom rule should take precedence.
+	channel := &Channel{
+		ID:                         1,
+		Status:                     StatusActive,
+		ApplyPricingToAccountStats: true,
+		AccountStatsPricingRules: []AccountStatsPricingRule{
+			{
+				GroupIDs: []int64{10},
+				Pricing: []ChannelModelPricing{
+					{
+						ID:         100,
+						Models:     []string{"claude-sonnet-4"},
+						InputPrice: testPtrFloat64(0.05),
+					},
+				},
+			},
+		},
+	}
+	cs := newTestChannelServiceForStats(t, channel, 10, "anthropic")
+
+	tokens := UsageTokens{InputTokens: 100}
+
+	result := resolveAccountStatsCost(
+		context.Background(),
+		cs, nil,
+		1, 10, "claude-sonnet-4",
+		tokens, 1, 99.0, // totalCost = 99.0 (would be used if ApplyPricing wins)
+	)
+	require.NotNil(t, result)
+	// Custom rule: 100*0.05 = 5.0 (NOT 99.0 from totalCost)
+	require.InDelta(t, 5.0, *result, 1e-12)
+}
+
+// ---------------------------------------------------------------------------
+// helpers for resolveAccountStatsCost tests
+// ---------------------------------------------------------------------------
+
+// newTestChannelServiceForStats creates a ChannelService with a single channel
+// mapped to the given groupID, suitable for resolveAccountStatsCost tests.
+func newTestChannelServiceForStats(t *testing.T, channel *Channel, groupID int64, platform string) *ChannelService {
+	t.Helper()
+	cache := newEmptyChannelCache()
+	cache.channelByGroupID[groupID] = channel
+	cache.groupPlatform[groupID] = platform
+	cs := &ChannelService{}
+	cache.loadedAt = time.Now()
+	cs.cache.Store(cache)
+	return cs
+}
diff --git a/backend/internal/service/balance_notify_check_test.go b/backend/internal/service/balance_notify_check_test.go
index 955f3129..7bb4cf9e 100644
--- a/backend/internal/service/balance_notify_check_test.go
+++ b/backend/internal/service/balance_notify_check_test.go
@@ -178,3 +178,227 @@ func TestGetSiteName_Configured(t *testing.T) {
 	repo.data[SettingKeySiteName] = "My Site"
 	require.Equal(t, "My Site", s.getSiteName(context.Background()))
 }
+
+// ---------- crossedDownward ----------
+
+func TestCrossedDownward_CrossesBelow(t *testing.T) {
+	// oldBalance > threshold, newBalance < threshold → true
+	require.True(t, crossedDownward(100, 5, 10))
+}
+
+func TestCrossedDownward_ExactlyAtThreshold(t *testing.T) {
+	// oldBalance > threshold, newBalance == threshold → false (not below)
+	require.False(t, crossedDownward(100, 10, 10))
+}
+
+func TestCrossedDownward_OldExactlyAtThreshold_NewBelow(t *testing.T) {
+	// oldBalance == threshold, newBalance < threshold → true
+	// (at-or-above → below counts as a crossing)
+	require.True(t, crossedDownward(10, 5, 10))
+}
+
+func TestCrossedDownward_AlreadyBelow(t *testing.T) {
+	// oldBalance < threshold → false (already below, no new crossing)
+	require.False(t, crossedDownward(5, 3, 10))
+}
+
+func TestCrossedDownward_BothAbove(t *testing.T) {
+	// oldBalance > threshold, newBalance > threshold → false (no crossing)
+	require.False(t, crossedDownward(100, 50, 10))
+}
+
+func TestCrossedDownward_ZeroThreshold(t *testing.T) {
+	// threshold == 0 → oldV >= 0 is always true, but newV < 0 only for negatives
+	// Typical case: positive balances should not fire when threshold is 0.
+	require.False(t, crossedDownward(10, 5, 0))
+	require.False(t, crossedDownward(0, 0, 0))
+}
+
+func TestCrossedDownward_ZeroThreshold_NegativeNew(t *testing.T) {
+	// Edge case: newBalance goes negative with threshold=0.
+	require.True(t, crossedDownward(5, -1, 0))
+}
+
+func TestCrossedDownward_NegativeValues(t *testing.T) {
+	// Both already negative, threshold is positive → no crossing (already below).
+	require.False(t, crossedDownward(-5, -10, 10))
+}
+
+func TestCrossedDownward_LargeDecrement(t *testing.T) {
+	// A single large deduction crosses the threshold.
+	require.True(t, crossedDownward(1000, 0.5, 100))
+}
+
+func TestCrossedDownward_SmallDecrement_NoCrossing(t *testing.T) {
+	// A tiny deduction stays above threshold.
+	require.False(t, crossedDownward(100, 99.99, 10))
+}
+
+// ---------- checkQuotaDimCrossings ----------
+
+func TestCheckQuotaDimCrossings_NoDimensions(t *testing.T) {
+	s, _ := newBalanceNotifyServiceForTest()
+	account := &Account{ID: 1, Name: "test", Platform: PlatformAnthropic}
+	// Empty dims → no crossing, no panic.
+	s.checkQuotaDimCrossings(account, nil, 10, []string{"admin@example.com"}, "TestSite")
+	s.checkQuotaDimCrossings(account, []quotaDim{}, 10, []string{"admin@example.com"}, "TestSite")
+}
+
+func TestCheckQuotaDimCrossings_DisabledDimension(t *testing.T) {
+	s, _ := newBalanceNotifyServiceForTest()
+	account := &Account{ID: 1, Name: "test", Platform: PlatformAnthropic}
+	dims := []quotaDim{
+		{
+			name:          quotaDimDaily,
+			enabled:       false, // disabled
+			threshold:     100,
+			thresholdType: thresholdTypeFixed,
+			currentUsed:   950,
+			limit:         1000,
+		},
+	}
+	// Disabled dimension should be skipped even if crossing would occur.
+	s.checkQuotaDimCrossings(account, dims, 50, []string{"admin@example.com"}, "TestSite")
+}
+
+func TestCheckQuotaDimCrossings_ZeroThresholdSkipped(t *testing.T) {
+	s, _ := newBalanceNotifyServiceForTest()
+	account := &Account{ID: 1, Name: "test", Platform: PlatformAnthropic}
+	dims := []quotaDim{
+		{
+			name:          quotaDimDaily,
+			enabled:       true,
+			threshold:     0, // zero threshold
+			thresholdType: thresholdTypeFixed,
+			currentUsed:   950,
+			limit:         1000,
+		},
+	}
+	// Zero threshold → skipped.
+	s.checkQuotaDimCrossings(account, dims, 50, []string{"admin@example.com"}, "TestSite")
+}
+
+func TestCheckQuotaDimCrossings_NoCrossing_BothBelowThreshold(t *testing.T) {
+	s, _ := newBalanceNotifyServiceForTest()
+	account := &Account{ID: 1, Name: "test", Platform: PlatformAnthropic}
+	// threshold=400 remaining, limit=1000 → effectiveThreshold = 600 (usage trigger)
+	// currentUsed=300 (after), oldUsed=300-50=250 (before). Both < 600, no crossing.
+	dims := []quotaDim{
+		{
+			name:          quotaDimDaily,
+			enabled:       true,
+			threshold:     400,
+			thresholdType: thresholdTypeFixed,
+			currentUsed:   300,
+			limit:         1000,
+		},
+	}
+	s.checkQuotaDimCrossings(account, dims, 50, []string{"admin@example.com"}, "TestSite")
+}
+
+func TestCheckQuotaDimCrossings_NoCrossing_BothAboveThreshold(t *testing.T) {
+	s, _ := newBalanceNotifyServiceForTest()
+	account := &Account{ID: 1, Name: "test", Platform: PlatformAnthropic}
+	// threshold=400 remaining, limit=1000 → effectiveThreshold = 600 (usage trigger)
+	// currentUsed=800 (after), oldUsed=800-50=750 (before). Both >= 600, no crossing.
+	dims := []quotaDim{
+		{
+			name:          quotaDimDaily,
+			enabled:       true,
+			threshold:     400,
+			thresholdType: thresholdTypeFixed,
+			currentUsed:   800,
+			limit:         1000,
+		},
+	}
+	s.checkQuotaDimCrossings(account, dims, 50, []string{"admin@example.com"}, "TestSite")
+}
+
+func TestCheckQuotaDimCrossings_NegativeResolvedThreshold_Skipped(t *testing.T) {
+	s, _ := newBalanceNotifyServiceForTest()
+	account := &Account{ID: 1, Name: "test", Platform: PlatformAnthropic}
+	// threshold=1200 remaining, limit=1000 → effectiveThreshold = 1000-1200 = -200
+	// Negative resolved threshold → skipped.
+	dims := []quotaDim{
+		{
+			name:          quotaDimDaily,
+			enabled:       true,
+			threshold:     1200,
+			thresholdType: thresholdTypeFixed,
+			currentUsed:   950,
+			limit:         1000,
+		},
+	}
+	s.checkQuotaDimCrossings(account, dims, 50, []string{"admin@example.com"}, "TestSite")
+}
+
+func TestCheckQuotaDimCrossings_PercentageThreshold_NoCrossing(t *testing.T) {
+	s, _ := newBalanceNotifyServiceForTest()
+	account := &Account{ID: 1, Name: "test", Platform: PlatformAnthropic}
+	// threshold=30%, limit=1000 → effectiveThreshold = 1000 * (1 - 0.30) = 700
+	// currentUsed=500, oldUsed=500-50=450. Both < 700, no crossing.
+	dims := []quotaDim{
+		{
+			name:          quotaDimWeekly,
+			enabled:       true,
+			threshold:     30,
+			thresholdType: thresholdTypePercentage,
+			currentUsed:   500,
+			limit:         1000,
+		},
+	}
+	s.checkQuotaDimCrossings(account, dims, 50, []string{"admin@example.com"}, "TestSite")
+}
+
+func TestCheckQuotaDimCrossings_ZeroLimit_Skipped(t *testing.T) {
+	s, _ := newBalanceNotifyServiceForTest()
+	account := &Account{ID: 1, Name: "test", Platform: PlatformAnthropic}
+	// limit=0 → resolvedThreshold returns 0 → skipped.
+	dims := []quotaDim{
+		{
+			name:          quotaDimTotal,
+			enabled:       true,
+			threshold:     100,
+			thresholdType: thresholdTypeFixed,
+			currentUsed:   50,
+			limit:         0,
+		},
+	}
+	s.checkQuotaDimCrossings(account, dims, 50, []string{"admin@example.com"}, "TestSite")
+}
+
+func TestCheckQuotaDimCrossings_MultipleDims_MixedResults(t *testing.T) {
+	s, _ := newBalanceNotifyServiceForTest()
+	account := &Account{ID: 1, Name: "test", Platform: PlatformAnthropic}
+	// dim1: no crossing (both below effective threshold)
+	// dim2: disabled (skipped)
+	// dim3: zero threshold (skipped)
+	dims := []quotaDim{
+		{
+			name:          quotaDimDaily,
+			enabled:       true,
+			threshold:     400,
+			thresholdType: thresholdTypeFixed,
+			currentUsed:   300, // oldUsed=250, effectiveThreshold=600, both below
+			limit:         1000,
+		},
+		{
+			name:          quotaDimWeekly,
+			enabled:       false,
+			threshold:     100,
+			thresholdType: thresholdTypeFixed,
+			currentUsed:   900,
+			limit:         1000,
+		},
+		{
+			name:          quotaDimTotal,
+			enabled:       true,
+			threshold:     0,
+			thresholdType: thresholdTypeFixed,
+			currentUsed:   500,
+			limit:         1000,
+		},
+	}
+	// None should trigger. No panic expected.
+	s.checkQuotaDimCrossings(account, dims, 50, []string{"admin@example.com"}, "TestSite")
+}
diff --git a/backend/internal/service/billing_service_test.go b/backend/internal/service/billing_service_test.go
index 6f6c41ce..2cf134e2 100644
--- a/backend/internal/service/billing_service_test.go
+++ b/backend/internal/service/billing_service_test.go
@@ -718,3 +718,123 @@ func TestGetModelPricing_MapsDynamicPriorityFieldsIntoBillingPricing(t *testing.
 	require.InDelta(t, 1.5, pricing.LongContextInputMultiplier, 1e-12)
 	require.InDelta(t, 1.25, pricing.LongContextOutputMultiplier, 1e-12)
 }
+
+// ---------------------------------------------------------------------------
+// GetModelPricingWithChannel
+// ---------------------------------------------------------------------------
+
+func TestGetModelPricingWithChannel_NilChannelPricing_ReturnsOriginal(t *testing.T) {
+	svc := newTestBillingService()
+
+	pricing, err := svc.GetModelPricingWithChannel("claude-sonnet-4", nil)
+	require.NoError(t, err)
+	require.NotNil(t, pricing)
+
+	// Should be identical to GetModelPricing
+	original, err := svc.GetModelPricing("claude-sonnet-4")
+	require.NoError(t, err)
+	require.InDelta(t, original.InputPricePerToken, pricing.InputPricePerToken, 1e-12)
+	require.InDelta(t, original.OutputPricePerToken, pricing.OutputPricePerToken, 1e-12)
+	require.InDelta(t, original.CacheCreationPricePerToken, pricing.CacheCreationPricePerToken, 1e-12)
+	require.InDelta(t, original.CacheReadPricePerToken, pricing.CacheReadPricePerToken, 1e-12)
+}
+
+func TestGetModelPricingWithChannel_OverrideInputPriceOnly(t *testing.T) {
+	svc := newTestBillingService()
+
+	chPricing := &ChannelModelPricing{
+		InputPrice: testPtrFloat64(99e-6),
+	}
+	pricing, err := svc.GetModelPricingWithChannel("claude-sonnet-4", chPricing)
+	require.NoError(t, err)
+
+	// InputPrice overridden (both normal and priority)
+	require.InDelta(t, 99e-6, pricing.InputPricePerToken, 1e-12)
+	require.InDelta(t, 99e-6, pricing.InputPricePerTokenPriority, 1e-12)
+
+	// OutputPrice unchanged (claude-sonnet-4 fallback = 15e-6)
+	require.InDelta(t, 15e-6, pricing.OutputPricePerToken, 1e-12)
+}
+
+func TestGetModelPricingWithChannel_OverrideOutputPriceOnly(t *testing.T) {
+	svc := newTestBillingService()
+
+	chPricing := &ChannelModelPricing{
+		OutputPrice: testPtrFloat64(88e-6),
+	}
+	pricing, err := svc.GetModelPricingWithChannel("claude-sonnet-4", chPricing)
+	require.NoError(t, err)
+
+	// OutputPrice overridden
+	require.InDelta(t, 88e-6, pricing.OutputPricePerToken, 1e-12)
+	require.InDelta(t, 88e-6, pricing.OutputPricePerTokenPriority, 1e-12)
+
+	// InputPrice unchanged (claude-sonnet-4 fallback = 3e-6)
+	require.InDelta(t, 3e-6, pricing.InputPricePerToken, 1e-12)
+}
+
+func TestGetModelPricingWithChannel_OverrideAllFields(t *testing.T) {
+	svc := newTestBillingService()
+
+	chPricing := &ChannelModelPricing{
+		InputPrice:       testPtrFloat64(10e-6),
+		OutputPrice:      testPtrFloat64(20e-6),
+		CacheWritePrice:  testPtrFloat64(5e-6),
+		CacheReadPrice:   testPtrFloat64(1e-6),
+		ImageOutputPrice: testPtrFloat64(50e-6),
+	}
+	pricing, err := svc.GetModelPricingWithChannel("claude-sonnet-4", chPricing)
+	require.NoError(t, err)
+
+	require.InDelta(t, 10e-6, pricing.InputPricePerToken, 1e-12)
+	require.InDelta(t, 10e-6, pricing.InputPricePerTokenPriority, 1e-12)
+	require.InDelta(t, 20e-6, pricing.OutputPricePerToken, 1e-12)
+	require.InDelta(t, 20e-6, pricing.OutputPricePerTokenPriority, 1e-12)
+	require.InDelta(t, 5e-6, pricing.CacheCreationPricePerToken, 1e-12)
+	require.InDelta(t, 5e-6, pricing.CacheCreation5mPrice, 1e-12)
+	require.InDelta(t, 5e-6, pricing.CacheCreation1hPrice, 1e-12)
+	require.InDelta(t, 1e-6, pricing.CacheReadPricePerToken, 1e-12)
+	require.InDelta(t, 1e-6, pricing.CacheReadPricePerTokenPriority, 1e-12)
+	require.InDelta(t, 50e-6, pricing.ImageOutputPricePerToken, 1e-12)
+}
+
+func TestGetModelPricingWithChannel_CacheWritePriceAffects5mAnd1h(t *testing.T) {
+	svc := newTestBillingService()
+
+	chPricing := &ChannelModelPricing{
+		CacheWritePrice: testPtrFloat64(7e-6),
+	}
+	pricing, err := svc.GetModelPricingWithChannel("claude-sonnet-4", chPricing)
+	require.NoError(t, err)
+
+	// CacheWritePrice should set all three: CacheCreationPricePerToken, 5m, and 1h
+	require.InDelta(t, 7e-6, pricing.CacheCreationPricePerToken, 1e-12)
+	require.InDelta(t, 7e-6, pricing.CacheCreation5mPrice, 1e-12)
+	require.InDelta(t, 7e-6, pricing.CacheCreation1hPrice, 1e-12)
+}
+
+func TestGetModelPricingWithChannel_CacheReadPriceAffectsPriority(t *testing.T) {
+	svc := newTestBillingService()
+
+	chPricing := &ChannelModelPricing{
+		CacheReadPrice: testPtrFloat64(2e-6),
+	}
+	pricing, err := svc.GetModelPricingWithChannel("claude-sonnet-4", chPricing)
+	require.NoError(t, err)
+
+	// CacheReadPrice should set both normal and priority
+	require.InDelta(t, 2e-6, pricing.CacheReadPricePerToken, 1e-12)
+	require.InDelta(t, 2e-6, pricing.CacheReadPricePerTokenPriority, 1e-12)
+}
+
+func TestGetModelPricingWithChannel_UnknownModelReturnsError(t *testing.T) {
+	svc := newTestBillingService()
+
+	chPricing := &ChannelModelPricing{
+		InputPrice: testPtrFloat64(1e-6),
+	}
+	pricing, err := svc.GetModelPricingWithChannel("totally-unknown-model", chPricing)
+	require.Error(t, err)
+	require.Nil(t, pricing)
+	require.Contains(t, err.Error(), "pricing not found")
+}
diff --git a/backend/internal/service/billing_service_unified_test.go b/backend/internal/service/billing_service_unified_test.go
new file mode 100644
index 00000000..694c3384
--- /dev/null
+++ b/backend/internal/service/billing_service_unified_test.go
@@ -0,0 +1,258 @@
+//go:build unit
+
+package service
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/Wei-Shaw/sub2api/internal/config"
+	"github.com/stretchr/testify/require"
+)
+
+// ---------------------------------------------------------------------------
+// CalculateCostUnified
+// ---------------------------------------------------------------------------
+
+func TestCalculateCostUnified_NilResolver_FallsBackToOldPath(t *testing.T) {
+	svc := newTestBillingService()
+
+	tokens := UsageTokens{InputTokens: 1000, OutputTokens: 500}
+	input := CostInput{
+		Model:          "claude-sonnet-4",
+		Tokens:         tokens,
+		RateMultiplier: 1.0,
+		Resolver:       nil, // no resolver
+	}
+	cost, err := svc.CalculateCostUnified(input)
+	require.NoError(t, err)
+
+	// Should match the old-path result exactly
+	expected, err := svc.calculateCostInternal("claude-sonnet-4", tokens, 1.0, "", nil)
+	require.NoError(t, err)
+	require.InDelta(t, expected.TotalCost, cost.TotalCost, 1e-10)
+	require.InDelta(t, expected.ActualCost, cost.ActualCost, 1e-10)
+	// BillingMode is NOT set by old path through CalculateCostUnified (resolver == nil)
+	require.Empty(t, cost.BillingMode)
+}
+
+func TestCalculateCostUnified_TokenMode(t *testing.T) {
+	bs := newTestBillingService()
+	resolver := NewModelPricingResolver(nil, bs)
+
+	tokens := UsageTokens{InputTokens: 1000, OutputTokens: 500}
+	input := CostInput{
+		Ctx:            context.Background(),
+		Model:          "claude-sonnet-4",
+		Tokens:         tokens,
+		RateMultiplier: 1.5,
+		Resolver:       resolver,
+	}
+	cost, err := bs.CalculateCostUnified(input)
+	require.NoError(t, err)
+	require.NotNil(t, cost)
+
+	// Verify token billing: Input: 1000*3e-6=0.003, Output: 500*15e-6=0.0075
+	expectedTotal := 1000*3e-6 + 500*15e-6
+	require.InDelta(t, expectedTotal, cost.TotalCost, 1e-10)
+	require.InDelta(t, expectedTotal*1.5, cost.ActualCost, 1e-10)
+	require.Equal(t, string(BillingModeToken), cost.BillingMode)
+}
+
+func TestCalculateCostUnified_PerRequestMode(t *testing.T) {
+	// Set up a ChannelService with a per-request pricing channel
+	cs := newTestChannelServiceWithCache(t, &channelCache{
+		pricingByGroupModel: map[channelModelKey]*ChannelModelPricing{
+			{groupID: 1, model: "claude-sonnet-4"}: {
+				BillingMode:     BillingModePerRequest,
+				PerRequestPrice: testPtrFloat64(0.05),
+			},
+		},
+		channelByGroupID: map[int64]*Channel{
+			1: {ID: 1, Status: StatusActive},
+		},
+		groupPlatform:           map[int64]string{1: ""},
+		wildcardByGroupPlatform: map[channelGroupPlatformKey][]*wildcardPricingEntry{},
+		mappingByGroupModel:     map[channelModelKey]string{},
+		wildcardMappingByGP:     map[channelGroupPlatformKey][]*wildcardMappingEntry{},
+		byID:                    map[int64]*Channel{},
+	})
+
+	bs := newTestBillingService()
+	resolver := NewModelPricingResolver(cs, bs)
+	groupID := int64(1)
+
+	input := CostInput{
+		Ctx:            context.Background(),
+		Model:          "claude-sonnet-4",
+		GroupID:        &groupID,
+		Tokens:         UsageTokens{InputTokens: 100, OutputTokens: 50},
+		RequestCount:   3,
+		RateMultiplier: 2.0,
+		Resolver:       resolver,
+	}
+	cost, err := bs.CalculateCostUnified(input)
+	require.NoError(t, err)
+	require.NotNil(t, cost)
+
+	// 3 requests * $0.05 = $0.15
+	require.InDelta(t, 0.15, cost.TotalCost, 1e-10)
+	// ActualCost = 0.15 * 2.0 = 0.30
+	require.InDelta(t, 0.30, cost.ActualCost, 1e-10)
+	require.Equal(t, string(BillingModePerRequest), cost.BillingMode)
+}
+
+func TestCalculateCostUnified_ImageMode(t *testing.T) {
+	cs := newTestChannelServiceWithCache(t, &channelCache{
+		pricingByGroupModel: map[channelModelKey]*ChannelModelPricing{
+			{groupID: 2, model: "gemini-image"}: {
+				BillingMode:     BillingModeImage,
+				PerRequestPrice: testPtrFloat64(0.10),
+			},
+		},
+		channelByGroupID: map[int64]*Channel{
+			2: {ID: 2, Status: StatusActive},
+		},
+		groupPlatform:           map[int64]string{2: ""},
+		wildcardByGroupPlatform: map[channelGroupPlatformKey][]*wildcardPricingEntry{},
+		mappingByGroupModel:     map[channelModelKey]string{},
+		wildcardMappingByGP:     map[channelGroupPlatformKey][]*wildcardMappingEntry{},
+		byID:                    map[int64]*Channel{},
+	})
+
+	bs := &BillingService{
+		cfg:            &config.Config{},
+		fallbackPrices: map[string]*ModelPricing{},
+	}
+	resolver := NewModelPricingResolver(cs, bs)
+	groupID := int64(2)
+
+	input := CostInput{
+		Ctx:            context.Background(),
+		Model:          "gemini-image",
+		GroupID:        &groupID,
+		Tokens:         UsageTokens{},
+		RequestCount:   2,
+		RateMultiplier: 1.0,
+		Resolver:       resolver,
+	}
+	cost, err := bs.CalculateCostUnified(input)
+	require.NoError(t, err)
+	require.NotNil(t, cost)
+
+	// 2 * $0.10 = $0.20
+	require.InDelta(t, 0.20, cost.TotalCost, 1e-10)
+	require.InDelta(t, 0.20, cost.ActualCost, 1e-10)
+	require.Equal(t, string(BillingModeImage), cost.BillingMode)
+}
+
+func TestCalculateCostUnified_RateMultiplierZeroDefaultsToOne(t *testing.T) {
+	bs := newTestBillingService()
+	resolver := NewModelPricingResolver(nil, bs)
+
+	tokens := UsageTokens{InputTokens: 1000, OutputTokens: 500}
+
+	costZero, err := bs.CalculateCostUnified(CostInput{
+		Ctx:            context.Background(),
+		Model:          "claude-sonnet-4",
+		Tokens:         tokens,
+		RateMultiplier: 0, // should default to 1.0
+		Resolver:       resolver,
+	})
+	require.NoError(t, err)
+
+	costOne, err := bs.CalculateCostUnified(CostInput{
+		Ctx:            context.Background(),
+		Model:          "claude-sonnet-4",
+		Tokens:         tokens,
+		RateMultiplier: 1.0,
+		Resolver:       resolver,
+	})
+	require.NoError(t, err)
+
+	require.InDelta(t, costOne.ActualCost, costZero.ActualCost, 1e-10)
+}
+
+func TestCalculateCostUnified_NegativeRateMultiplierDefaultsToOne(t *testing.T) {
+	bs := newTestBillingService()
+	resolver := NewModelPricingResolver(nil, bs)
+
+	tokens := UsageTokens{InputTokens: 1000}
+
+	costNeg, err := bs.CalculateCostUnified(CostInput{
+		Ctx:            context.Background(),
+		Model:          "claude-sonnet-4",
+		Tokens:         tokens,
+		RateMultiplier: -5.0,
+		Resolver:       resolver,
+	})
+	require.NoError(t, err)
+
+	costOne, err := bs.CalculateCostUnified(CostInput{
+		Ctx:            context.Background(),
+		Model:          "claude-sonnet-4",
+		Tokens:         tokens,
+		RateMultiplier: 1.0,
+		Resolver:       resolver,
+	})
+	require.NoError(t, err)
+
+	require.InDelta(t, costOne.ActualCost, costNeg.ActualCost, 1e-10)
+}
+
+func TestCalculateCostUnified_BillingModeFieldFilled(t *testing.T) {
+	bs := newTestBillingService()
+	resolver := NewModelPricingResolver(nil, bs)
+
+	cost, err := bs.CalculateCostUnified(CostInput{
+		Ctx:            context.Background(),
+		Model:          "claude-sonnet-4",
+		Tokens:         UsageTokens{InputTokens: 100},
+		RateMultiplier: 1.0,
+		Resolver:       resolver,
+	})
+	require.NoError(t, err)
+	require.Equal(t, "token", cost.BillingMode)
+}
+
+func TestCalculateCostUnified_UsesPreResolvedPricing(t *testing.T) {
+	bs := newTestBillingService()
+	resolver := NewModelPricingResolver(nil, bs)
+
+	// Pre-resolve with per_request mode to verify it's used instead of re-resolving
+	preResolved := &ResolvedPricing{
+		Mode:                   BillingModePerRequest,
+		DefaultPerRequestPrice: 0.07,
+	}
+
+	cost, err := bs.CalculateCostUnified(CostInput{
+		Ctx:            context.Background(),
+		Model:          "claude-sonnet-4",
+		Tokens:         UsageTokens{InputTokens: 100},
+		RequestCount:   2,
+		RateMultiplier: 1.0,
+		Resolver:       resolver,
+		Resolved:       preResolved,
+	})
+	require.NoError(t, err)
+	require.NotNil(t, cost)
+
+	// 2 * $0.07 = $0.14
+	require.InDelta(t, 0.14, cost.TotalCost, 1e-10)
+	require.Equal(t, string(BillingModePerRequest), cost.BillingMode)
+}
+
+// ---------------------------------------------------------------------------
+// helpers
+// ---------------------------------------------------------------------------
+
+// newTestChannelServiceWithCache creates a ChannelService with a pre-populated
+// cache snapshot, bypassing the repository layer entirely.
+func newTestChannelServiceWithCache(t *testing.T, cache *channelCache) *ChannelService {
+	t.Helper()
+	cs := &ChannelService{}
+	cache.loadedAt = time.Now()
+	cs.cache.Store(cache)
+	return cs
+}
diff --git a/backend/internal/service/gateway_websearch_emulation_test.go b/backend/internal/service/gateway_websearch_emulation_test.go
index b606c748..de1f0014 100644
--- a/backend/internal/service/gateway_websearch_emulation_test.go
+++ b/backend/internal/service/gateway_websearch_emulation_test.go
@@ -1,8 +1,14 @@
+//go:build unit
+
 package service
 
 import (
+	"context"
+	"encoding/json"
 	"testing"
+	"time"
 
+	"github.com/Wei-Shaw/sub2api/internal/config"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/websearch"
 	"github.com/stretchr/testify/require"
 )
@@ -140,3 +146,235 @@ func TestBuildTextSummary_NoResults(t *testing.T) {
 	summary := buildTextSummary("test", nil)
 	require.Contains(t, summary, "No search results found for: test")
 }
+
+// --- shouldEmulateWebSearch ---
+
+// webSearchToolBody is a valid request body with exactly one web_search tool.
+var webSearchToolBody = []byte(`{"tools":[{"type":"web_search"}],"messages":[{"role":"user","content":"test"}]}`)
+
+// nonWebSearchToolBody is a request body without web_search tool.
+var nonWebSearchToolBody = []byte(`{"tools":[{"type":"text_editor"}],"messages":[{"role":"user","content":"test"}]}`)
+
+// newAnthropicAPIKeyAccount creates a test Account with the given web search emulation mode.
+func newAnthropicAPIKeyAccount(mode string) *Account {
+	return &Account{
+		ID:       1,
+		Platform: PlatformAnthropic,
+		Type:     AccountTypeAPIKey,
+		Extra:    map[string]any{featureKeyWebSearchEmulation: mode},
+	}
+}
+
+// setGlobalWebSearchConfig stores a config in the global cache used by SettingService.IsWebSearchEmulationEnabled.
+func setGlobalWebSearchConfig(cfg *WebSearchEmulationConfig) {
+	webSearchEmulationCache.Store(&cachedWebSearchEmulationConfig{
+		config:    cfg,
+		expiresAt: time.Now().Add(10 * time.Minute).UnixNano(),
+	})
+}
+
+// clearGlobalWebSearchConfig resets the global cache to force re-read.
+func clearGlobalWebSearchConfig() {
+	webSearchEmulationCache.Store((*cachedWebSearchEmulationConfig)(nil))
+}
+
+// newSettingServiceForWebSearchTest creates a SettingService with a mock repo pre-loaded with config.
+func newSettingServiceForWebSearchTest(enabled bool) *SettingService {
+	repo := newMockSettingRepo()
+	cfg := &WebSearchEmulationConfig{
+		Enabled:   enabled,
+		Providers: []WebSearchProviderConfig{{Type: "brave", APIKey: "sk-test"}},
+	}
+	data, _ := json.Marshal(cfg)
+	repo.data[SettingKeyWebSearchEmulationConfig] = string(data)
+	return NewSettingService(repo, &config.Config{})
+}
+
+// newChannelServiceWithCache creates a ChannelService with a pre-built cache containing the channel.
+func newChannelServiceWithCache(groupID int64, ch *Channel) *ChannelService {
+	svc := &ChannelService{}
+	cache := &channelCache{
+		channelByGroupID: map[int64]*Channel{groupID: ch},
+		byID:             map[int64]*Channel{ch.ID: ch},
+		groupPlatform:    map[int64]string{},
+		loadedAt:         time.Now(),
+	}
+	svc.cache.Store(cache)
+	return svc
+}
+
+func TestShouldEmulateWebSearch_NilManager(t *testing.T) {
+	SetWebSearchManager(nil)
+	defer SetWebSearchManager(nil)
+
+	settingSvc := newSettingServiceForWebSearchTest(true)
+	setGlobalWebSearchConfig(&WebSearchEmulationConfig{
+		Enabled:   true,
+		Providers: []WebSearchProviderConfig{{Type: "brave", APIKey: "k"}},
+	})
+	defer clearGlobalWebSearchConfig()
+
+	svc := &GatewayService{settingService: settingSvc}
+	account := newAnthropicAPIKeyAccount(WebSearchModeEnabled)
+	require.False(t, svc.shouldEmulateWebSearch(context.Background(), account, nil, webSearchToolBody))
+}
+
+func TestShouldEmulateWebSearch_NotOnlyWebSearchTool(t *testing.T) {
+	mgr := websearch.NewManager([]websearch.ProviderConfig{{Type: "brave", APIKey: "k"}}, nil)
+	SetWebSearchManager(mgr)
+	defer SetWebSearchManager(nil)
+
+	settingSvc := newSettingServiceForWebSearchTest(true)
+	setGlobalWebSearchConfig(&WebSearchEmulationConfig{
+		Enabled:   true,
+		Providers: []WebSearchProviderConfig{{Type: "brave", APIKey: "k"}},
+	})
+	defer clearGlobalWebSearchConfig()
+
+	svc := &GatewayService{settingService: settingSvc}
+	account := newAnthropicAPIKeyAccount(WebSearchModeEnabled)
+	require.False(t, svc.shouldEmulateWebSearch(context.Background(), account, nil, nonWebSearchToolBody))
+}
+
+func TestShouldEmulateWebSearch_GlobalDisabled(t *testing.T) {
+	mgr := websearch.NewManager([]websearch.ProviderConfig{{Type: "brave", APIKey: "k"}}, nil)
+	SetWebSearchManager(mgr)
+	defer SetWebSearchManager(nil)
+
+	// Global config disabled
+	setGlobalWebSearchConfig(&WebSearchEmulationConfig{
+		Enabled:   false,
+		Providers: []WebSearchProviderConfig{{Type: "brave", APIKey: "k"}},
+	})
+	defer clearGlobalWebSearchConfig()
+
+	settingSvc := newSettingServiceForWebSearchTest(false)
+	svc := &GatewayService{settingService: settingSvc}
+	account := newAnthropicAPIKeyAccount(WebSearchModeEnabled)
+	require.False(t, svc.shouldEmulateWebSearch(context.Background(), account, nil, webSearchToolBody))
+}
+
+func TestShouldEmulateWebSearch_AccountDisabled(t *testing.T) {
+	mgr := websearch.NewManager([]websearch.ProviderConfig{{Type: "brave", APIKey: "k"}}, nil)
+	SetWebSearchManager(mgr)
+	defer SetWebSearchManager(nil)
+
+	setGlobalWebSearchConfig(&WebSearchEmulationConfig{
+		Enabled:   true,
+		Providers: []WebSearchProviderConfig{{Type: "brave", APIKey: "k"}},
+	})
+	defer clearGlobalWebSearchConfig()
+
+	settingSvc := newSettingServiceForWebSearchTest(true)
+	svc := &GatewayService{settingService: settingSvc}
+	account := newAnthropicAPIKeyAccount(WebSearchModeDisabled)
+	require.False(t, svc.shouldEmulateWebSearch(context.Background(), account, nil, webSearchToolBody))
+}
+
+func TestShouldEmulateWebSearch_AccountEnabled(t *testing.T) {
+	mgr := websearch.NewManager([]websearch.ProviderConfig{{Type: "brave", APIKey: "k"}}, nil)
+	SetWebSearchManager(mgr)
+	defer SetWebSearchManager(nil)
+
+	setGlobalWebSearchConfig(&WebSearchEmulationConfig{
+		Enabled:   true,
+		Providers: []WebSearchProviderConfig{{Type: "brave", APIKey: "k"}},
+	})
+	defer clearGlobalWebSearchConfig()
+
+	settingSvc := newSettingServiceForWebSearchTest(true)
+	svc := &GatewayService{settingService: settingSvc}
+	account := newAnthropicAPIKeyAccount(WebSearchModeEnabled)
+	require.True(t, svc.shouldEmulateWebSearch(context.Background(), account, nil, webSearchToolBody))
+}
+
+func TestShouldEmulateWebSearch_DefaultMode_ChannelEnabled(t *testing.T) {
+	mgr := websearch.NewManager([]websearch.ProviderConfig{{Type: "brave", APIKey: "k"}}, nil)
+	SetWebSearchManager(mgr)
+	defer SetWebSearchManager(nil)
+
+	setGlobalWebSearchConfig(&WebSearchEmulationConfig{
+		Enabled:   true,
+		Providers: []WebSearchProviderConfig{{Type: "brave", APIKey: "k"}},
+	})
+	defer clearGlobalWebSearchConfig()
+
+	settingSvc := newSettingServiceForWebSearchTest(true)
+	ch := &Channel{
+		ID:     10,
+		Status: StatusActive,
+		FeaturesConfig: map[string]any{
+			featureKeyWebSearchEmulation: map[string]any{PlatformAnthropic: true},
+		},
+	}
+	channelSvc := newChannelServiceWithCache(42, ch)
+	svc := &GatewayService{settingService: settingSvc, channelService: channelSvc}
+
+	account := newAnthropicAPIKeyAccount(WebSearchModeDefault)
+	groupID := int64(42)
+	require.True(t, svc.shouldEmulateWebSearch(context.Background(), account, &groupID, webSearchToolBody))
+}
+
+func TestShouldEmulateWebSearch_DefaultMode_ChannelDisabled(t *testing.T) {
+	mgr := websearch.NewManager([]websearch.ProviderConfig{{Type: "brave", APIKey: "k"}}, nil)
+	SetWebSearchManager(mgr)
+	defer SetWebSearchManager(nil)
+
+	setGlobalWebSearchConfig(&WebSearchEmulationConfig{
+		Enabled:   true,
+		Providers: []WebSearchProviderConfig{{Type: "brave", APIKey: "k"}},
+	})
+	defer clearGlobalWebSearchConfig()
+
+	settingSvc := newSettingServiceForWebSearchTest(true)
+	ch := &Channel{
+		ID:     10,
+		Status: StatusActive,
+		FeaturesConfig: map[string]any{
+			featureKeyWebSearchEmulation: map[string]any{PlatformAnthropic: false},
+		},
+	}
+	channelSvc := newChannelServiceWithCache(42, ch)
+	svc := &GatewayService{settingService: settingSvc, channelService: channelSvc}
+
+	account := newAnthropicAPIKeyAccount(WebSearchModeDefault)
+	groupID := int64(42)
+	require.False(t, svc.shouldEmulateWebSearch(context.Background(), account, &groupID, webSearchToolBody))
+}
+
+func TestShouldEmulateWebSearch_DefaultMode_NilGroupID(t *testing.T) {
+	mgr := websearch.NewManager([]websearch.ProviderConfig{{Type: "brave", APIKey: "k"}}, nil)
+	SetWebSearchManager(mgr)
+	defer SetWebSearchManager(nil)
+
+	setGlobalWebSearchConfig(&WebSearchEmulationConfig{
+		Enabled:   true,
+		Providers: []WebSearchProviderConfig{{Type: "brave", APIKey: "k"}},
+	})
+	defer clearGlobalWebSearchConfig()
+
+	settingSvc := newSettingServiceForWebSearchTest(true)
+	svc := &GatewayService{settingService: settingSvc}
+	account := newAnthropicAPIKeyAccount(WebSearchModeDefault)
+	// nil groupID + default mode → falls through to channel check → returns false
+	require.False(t, svc.shouldEmulateWebSearch(context.Background(), account, nil, webSearchToolBody))
+}
+
+func TestShouldEmulateWebSearch_DefaultMode_NilChannelService(t *testing.T) {
+	mgr := websearch.NewManager([]websearch.ProviderConfig{{Type: "brave", APIKey: "k"}}, nil)
+	SetWebSearchManager(mgr)
+	defer SetWebSearchManager(nil)
+
+	setGlobalWebSearchConfig(&WebSearchEmulationConfig{
+		Enabled:   true,
+		Providers: []WebSearchProviderConfig{{Type: "brave", APIKey: "k"}},
+	})
+	defer clearGlobalWebSearchConfig()
+
+	settingSvc := newSettingServiceForWebSearchTest(true)
+	svc := &GatewayService{settingService: settingSvc, channelService: nil}
+	account := newAnthropicAPIKeyAccount(WebSearchModeDefault)
+	groupID := int64(42)
+	// nil channelService + default mode → returns false
+	require.False(t, svc.shouldEmulateWebSearch(context.Background(), account, &groupID, webSearchToolBody))
+}
diff --git a/backend/internal/service/notify_email_entry_test.go b/backend/internal/service/notify_email_entry_test.go
new file mode 100644
index 00000000..0f4bb12e
--- /dev/null
+++ b/backend/internal/service/notify_email_entry_test.go
@@ -0,0 +1,156 @@
+//go:build unit
+
+package service
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// ---------- ParseNotifyEmails ----------
+
+func TestParseNotifyEmails_EmptyString(t *testing.T) {
+	result := ParseNotifyEmails("")
+	require.Nil(t, result)
+}
+
+func TestParseNotifyEmails_EmptyArray(t *testing.T) {
+	result := ParseNotifyEmails("[]")
+	require.Nil(t, result)
+}
+
+func TestParseNotifyEmails_Null(t *testing.T) {
+	// "null" is valid JSON that unmarshals into a nil string slice.
+	// The old-format branch then returns an empty (non-nil) slice.
+	result := ParseNotifyEmails("null")
+	require.Empty(t, result)
+}
+
+func TestParseNotifyEmails_WhitespaceOnly(t *testing.T) {
+	result := ParseNotifyEmails("   ")
+	require.Nil(t, result)
+}
+
+func TestParseNotifyEmails_OldFormat(t *testing.T) {
+	raw := `["alice@example.com", "bob@example.com"]`
+	result := ParseNotifyEmails(raw)
+	require.Len(t, result, 2)
+
+	require.Equal(t, "alice@example.com", result[0].Email)
+	require.False(t, result[0].Verified, "old format emails should default to unverified")
+	require.False(t, result[0].Disabled)
+
+	require.Equal(t, "bob@example.com", result[1].Email)
+	require.False(t, result[1].Verified)
+	require.False(t, result[1].Disabled)
+}
+
+func TestParseNotifyEmails_OldFormat_SkipsEmptyEntries(t *testing.T) {
+	raw := `["alice@example.com", "", "  ", "bob@example.com"]`
+	result := ParseNotifyEmails(raw)
+	require.Len(t, result, 2)
+	require.Equal(t, "alice@example.com", result[0].Email)
+	require.Equal(t, "bob@example.com", result[1].Email)
+}
+
+func TestParseNotifyEmails_NewFormat(t *testing.T) {
+	raw := `[{"email":"alice@example.com","verified":true,"disabled":false},{"email":"bob@example.com","verified":false,"disabled":true}]`
+	result := ParseNotifyEmails(raw)
+	require.Len(t, result, 2)
+
+	require.Equal(t, "alice@example.com", result[0].Email)
+	require.True(t, result[0].Verified)
+	require.False(t, result[0].Disabled)
+
+	require.Equal(t, "bob@example.com", result[1].Email)
+	require.False(t, result[1].Verified)
+	require.True(t, result[1].Disabled)
+}
+
+func TestParseNotifyEmails_NewFormat_SingleEntry(t *testing.T) {
+	raw := `[{"email":"solo@example.com","verified":true,"disabled":false}]`
+	result := ParseNotifyEmails(raw)
+	require.Len(t, result, 1)
+	require.Equal(t, "solo@example.com", result[0].Email)
+	require.True(t, result[0].Verified)
+}
+
+func TestParseNotifyEmails_InvalidJSON(t *testing.T) {
+	result := ParseNotifyEmails(`{not valid json`)
+	require.Nil(t, result)
+}
+
+func TestParseNotifyEmails_InvalidJSONObject(t *testing.T) {
+	// A plain JSON object (not array) should return nil.
+	result := ParseNotifyEmails(`{"email":"a@b.com"}`)
+	require.Nil(t, result)
+}
+
+func TestParseNotifyEmails_WhitespacePadding(t *testing.T) {
+	raw := `  ["padded@example.com"]  `
+	result := ParseNotifyEmails(raw)
+	require.Len(t, result, 1)
+	require.Equal(t, "padded@example.com", result[0].Email)
+}
+
+// ---------- MarshalNotifyEmails ----------
+
+func TestMarshalNotifyEmails_EmptySlice(t *testing.T) {
+	result := MarshalNotifyEmails([]NotifyEmailEntry{})
+	require.Equal(t, "[]", result)
+}
+
+func TestMarshalNotifyEmails_NilSlice(t *testing.T) {
+	result := MarshalNotifyEmails(nil)
+	require.Equal(t, "[]", result)
+}
+
+func TestMarshalNotifyEmails_SingleEntry(t *testing.T) {
+	entries := []NotifyEmailEntry{
+		{Email: "test@example.com", Verified: true, Disabled: false},
+	}
+	result := MarshalNotifyEmails(entries)
+	require.Contains(t, result, `"email":"test@example.com"`)
+	require.Contains(t, result, `"verified":true`)
+	require.Contains(t, result, `"disabled":false`)
+
+	// Round-trip: parsing the marshalled result should produce the original entries.
+	parsed := ParseNotifyEmails(result)
+	require.Len(t, parsed, 1)
+	require.Equal(t, entries[0], parsed[0])
+}
+
+func TestMarshalNotifyEmails_MultipleEntries(t *testing.T) {
+	entries := []NotifyEmailEntry{
+		{Email: "a@example.com", Verified: true, Disabled: false},
+		{Email: "b@example.com", Verified: false, Disabled: true},
+	}
+	result := MarshalNotifyEmails(entries)
+
+	// Round-trip verification.
+	parsed := ParseNotifyEmails(result)
+	require.Len(t, parsed, 2)
+	require.Equal(t, entries[0], parsed[0])
+	require.Equal(t, entries[1], parsed[1])
+}
+
+func TestMarshalNotifyEmails_RoundTrip_NewFormat(t *testing.T) {
+	original := []NotifyEmailEntry{
+		{Email: "x@example.com", Verified: true, Disabled: true},
+		{Email: "y@example.com", Verified: false, Disabled: false},
+	}
+	marshalled := MarshalNotifyEmails(original)
+	parsed := ParseNotifyEmails(marshalled)
+	require.Equal(t, original, parsed)
+}
+
+// ---------- isOldStringArrayFormat (indirectly via ParseNotifyEmails) ----------
+
+func TestParseNotifyEmails_MixedOldFormatWithWhitespace(t *testing.T) {
+	// Emails with leading/trailing whitespace in old format should be trimmed.
+	raw := `["  alice@example.com  "]`
+	result := ParseNotifyEmails(raw)
+	require.Len(t, result, 1)
+	require.Equal(t, "alice@example.com", result[0].Email)
+}
diff --git a/backend/internal/service/websearch_config_test.go b/backend/internal/service/websearch_config_test.go
index 8cd50d0d..c5b96e01 100644
--- a/backend/internal/service/websearch_config_test.go
+++ b/backend/internal/service/websearch_config_test.go
@@ -1,9 +1,12 @@
+//go:build unit
+
 package service
 
 import (
 	"context"
 	"testing"
 
+	"github.com/Wei-Shaw/sub2api/internal/pkg/websearch"
 	"github.com/stretchr/testify/require"
 )
 
@@ -141,3 +144,123 @@ func TestSanitizeWebSearchConfig_DoesNotMutateOriginal(t *testing.T) {
 	_ = SanitizeWebSearchConfig(context.Background(), cfg)
 	require.Equal(t, "secret", cfg.Providers[0].APIKey)
 }
+
+// --- PopulateWebSearchUsage ---
+
+func TestPopulateWebSearchUsage_NilInput(t *testing.T) {
+	require.Nil(t, PopulateWebSearchUsage(context.Background(), nil))
+}
+
+func TestPopulateWebSearchUsage_NoManager_QuotaUsedZero(t *testing.T) {
+	// Ensure no global manager is set
+	SetWebSearchManager(nil)
+	defer SetWebSearchManager(nil)
+
+	cfg := &WebSearchEmulationConfig{
+		Enabled: true,
+		Providers: []WebSearchProviderConfig{
+			{Type: "brave", APIKey: "sk-key", QuotaLimit: int64Ptr(1000)},
+		},
+	}
+	out := PopulateWebSearchUsage(context.Background(), cfg)
+	require.NotNil(t, out)
+	require.Len(t, out.Providers, 1)
+	require.Equal(t, int64(0), out.Providers[0].QuotaUsed)
+}
+
+func TestPopulateWebSearchUsage_APIKeyConfigured_True(t *testing.T) {
+	SetWebSearchManager(nil)
+	defer SetWebSearchManager(nil)
+
+	cfg := &WebSearchEmulationConfig{
+		Providers: []WebSearchProviderConfig{
+			{Type: "brave", APIKey: "sk-key"},
+		},
+	}
+	out := PopulateWebSearchUsage(context.Background(), cfg)
+	require.True(t, out.Providers[0].APIKeyConfigured)
+}
+
+func TestPopulateWebSearchUsage_APIKeyConfigured_False(t *testing.T) {
+	SetWebSearchManager(nil)
+	defer SetWebSearchManager(nil)
+
+	cfg := &WebSearchEmulationConfig{
+		Providers: []WebSearchProviderConfig{
+			{Type: "brave", APIKey: ""},
+		},
+	}
+	out := PopulateWebSearchUsage(context.Background(), cfg)
+	require.False(t, out.Providers[0].APIKeyConfigured)
+}
+
+func TestPopulateWebSearchUsage_NilQuotaLimit(t *testing.T) {
+	SetWebSearchManager(nil)
+	defer SetWebSearchManager(nil)
+
+	cfg := &WebSearchEmulationConfig{
+		Providers: []WebSearchProviderConfig{
+			{Type: "brave", APIKey: "sk-key", QuotaLimit: nil},
+		},
+	}
+	out := PopulateWebSearchUsage(context.Background(), cfg)
+	require.Nil(t, out.Providers[0].QuotaLimit)
+}
+
+func TestPopulateWebSearchUsage_NonNilQuotaLimit(t *testing.T) {
+	SetWebSearchManager(nil)
+	defer SetWebSearchManager(nil)
+
+	cfg := &WebSearchEmulationConfig{
+		Providers: []WebSearchProviderConfig{
+			{Type: "brave", APIKey: "sk-key", QuotaLimit: int64Ptr(500)},
+		},
+	}
+	out := PopulateWebSearchUsage(context.Background(), cfg)
+	require.NotNil(t, out.Providers[0].QuotaLimit)
+	require.Equal(t, int64(500), *out.Providers[0].QuotaLimit)
+}
+
+func TestPopulateWebSearchUsage_WithManager_NilRedis(t *testing.T) {
+	// Manager with nil Redis returns 0 usage without error
+	mgr := websearch.NewManager([]websearch.ProviderConfig{
+		{Type: "brave", APIKey: "k"},
+	}, nil)
+	SetWebSearchManager(mgr)
+	defer SetWebSearchManager(nil)
+
+	cfg := &WebSearchEmulationConfig{
+		Providers: []WebSearchProviderConfig{
+			{Type: "brave", APIKey: "sk-key", QuotaLimit: int64Ptr(1000)},
+		},
+	}
+	out := PopulateWebSearchUsage(context.Background(), cfg)
+	require.Equal(t, int64(0), out.Providers[0].QuotaUsed)
+	require.True(t, out.Providers[0].APIKeyConfigured)
+}
+
+func TestPopulateWebSearchUsage_DoesNotMutateOriginal(t *testing.T) {
+	SetWebSearchManager(nil)
+	defer SetWebSearchManager(nil)
+
+	cfg := &WebSearchEmulationConfig{
+		Providers: []WebSearchProviderConfig{
+			{Type: "brave", APIKey: "secret", QuotaLimit: int64Ptr(100)},
+		},
+	}
+	_ = PopulateWebSearchUsage(context.Background(), cfg)
+	// Original should be unchanged
+	require.Equal(t, "secret", cfg.Providers[0].APIKey)
+	require.Equal(t, int64(0), cfg.Providers[0].QuotaUsed)
+}
+
+// --- ResetWebSearchUsage ---
+
+func TestResetWebSearchUsage_NilManager(t *testing.T) {
+	SetWebSearchManager(nil)
+	defer SetWebSearchManager(nil)
+
+	err := ResetWebSearchUsage(context.Background(), "brave")
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "not initialized")
+}