Merge pull request #6700 from qiu121/codex/fix/deepseek-account-cost-peak

fix(billing): 修复 DeepSeek 高峰账号成本少计

backend/internal/service/account_stats_pricing.go

@@ -3,6 +3,7 @@ package service
 import (
 	"context"
 	"strings"
+	"time"
 )
 
 // resolveAccountStatsCost 计算账号统计定价费用。
@@ -17,6 +18,7 @@ import (
 // upstreamModel 是最终发往上游的模型 ID。
 // totalCost 是本次请求的客户计费（倍率前），用于优先级 2。
 // serviceTier 是最终参与用户计费的 OpenAI 服务层级，用于优先级 3。
+// pricingAt 与本次客户计费使用同一时刻，避免跨峰谷请求的成本与售价错位。
 // reasoningEffort 是最终转发等级；Fable 5.1 max 默认按 3 倍额度消耗。
 func resolveAccountStatsCost(
 	ctx context.Context,
@@ -29,6 +31,7 @@ func resolveAccountStatsCost(
 	requestCount int,
 	totalCost float64,
 	serviceTier string,
+	pricingAt time.Time,
 	reasoningEfforts ...string,
 ) *float64 {
 	reasoningEffort := ""
@@ -61,7 +64,7 @@ func resolveAccountStatsCost(
 
 	// 优先级 3：模型定价文件（LiteLLM）默认价格
 	if billingService != nil {
-		return tryModelFilePricing(billingService, upstreamModel, tokens, serviceTier, reasoningEffort)
+		return tryModelFilePricing(billingService, upstreamModel, tokens, serviceTier, pricingAt, reasoningEffort)
 	}
 
 	return nil
@@ -69,20 +72,26 @@ func resolveAccountStatsCost(
 
 // tryModelFilePricing 使用模型定价文件（LiteLLM/fallback）中的价格计算费用。
 // 与用户计费共用同一条定价管线，避免这里维护第二份"单价 × token 数"实现后，
-// 每加一个定价特性都要手工镜像一次。channelPricing 为 nil，保持优先级 3 的
-// 语义：只取模型定价文件，不引入渠道自定义定价。
-func tryModelFilePricing(billingService *BillingService, model string, tokens UsageTokens, serviceTier string, reasoningEfforts ...string) *float64 {
+// 每加一个定价特性都要手工镜像一次。解析器不配置渠道或分组，保持优先级 3 的
+// 语义：只取模型定价文件，不引入自定义售价。
+func tryModelFilePricing(billingService *BillingService, model string, tokens UsageTokens, serviceTier string, pricingAt time.Time, reasoningEfforts ...string) *float64 {
 	reasoningEffort := ""
 	if len(reasoningEfforts) > 0 {
 		reasoningEffort = reasoningEfforts[0]
 	}
-	breakdown, err := billingService.CalculateCostWithServiceTier(
-		model, tokens, 1, normalizeBillingServiceTier(serviceTier),
-	)
+	breakdown, err := billingService.CalculateCostUnified(CostInput{
+		Ctx:             context.Background(),
+		Model:           model,
+		Tokens:          tokens,
+		RateMultiplier:  1,
+		ServiceTier:     normalizeBillingServiceTier(serviceTier),
+		ReasoningEffort: reasoningEffort,
+		PricingAt:       pricingAt,
+		Resolver:        NewModelPricingResolver(nil, billingService),
+	})
 	if err != nil || breakdown == nil || breakdown.TotalCost <= 0 {
 		return nil
 	}
-	applyCostBreakdownMultiplier(breakdown, maxReasoningEffortBillingMultiplier(model, reasoningEffort, nil))
 	return &breakdown.TotalCost
 }
 
@@ -253,6 +262,7 @@ func applyAccountStatsCost(
 	upstreamModel, requestedModel string,
 	tokens UsageTokens,
 	totalCost float64,
+	pricingAt time.Time,
 ) {
 	model := upstreamModel
 	if model == "" {
@@ -271,6 +281,6 @@ func applyAccountStatsCost(
 		reasoningEffort = *usageLog.ReasoningEffort
 	}
 	usageLog.AccountStatsCost = resolveAccountStatsCost(
-		ctx, cs, bs, accountID, groupID, model, tokens, requestCount, totalCost, serviceTier, reasoningEffort,
+		ctx, cs, bs, accountID, groupID, model, tokens, requestCount, totalCost, serviceTier, pricingAt, reasoningEffort,
 	)
 }

backend/internal/service/account_stats_pricing_test.go

@@ -472,7 +472,7 @@ func TestTryModelFilePricing_Success(t *testing.T) {
 		},
 	})
 	tokens := UsageTokens{InputTokens: 100, OutputTokens: 50}
-	result := tryModelFilePricing(bs, "claude-sonnet-4", tokens, "")
+	result := tryModelFilePricing(bs, "claude-sonnet-4", tokens, "", time.Time{})
 	require.NotNil(t, result)
 	// 100*0.001 + 50*0.002 = 0.1 + 0.1 = 0.2
 	require.InDelta(t, 0.2, *result, 1e-12)
@@ -483,8 +483,8 @@ func TestTryModelFilePricing_Fable51MaxEffortUsesTripleQuota(t *testing.T) {
 		"claude-fable-5-1": {InputPricePerToken: 0.001},
 	})
 	tokens := UsageTokens{InputTokens: 100}
-	standard := tryModelFilePricing(bs, "claude-fable-5-1", tokens, "", "xhigh")
-	max := tryModelFilePricing(bs, "claude-fable-5-1", tokens, "", "max")
+	standard := tryModelFilePricing(bs, "claude-fable-5-1", tokens, "", time.Time{}, "xhigh")
+	max := tryModelFilePricing(bs, "claude-fable-5-1", tokens, "", time.Time{}, "max")
 	require.NotNil(t, standard)
 	require.NotNil(t, max)
 	require.InDelta(t, *standard*3, *max, 1e-12)
@@ -503,7 +503,7 @@ func TestTryModelFilePricing_AppliesLongContextPricing(t *testing.T) {
 	})
 	tokens := UsageTokens{InputTokens: 101, OutputTokens: 10, CacheReadTokens: 5}
 
-	result := tryModelFilePricing(bs, "gpt-5.6-sol", tokens, "")
+	result := tryModelFilePricing(bs, "gpt-5.6-sol", tokens, "", time.Time{})
 
 	require.NotNil(t, result)
 	// Input and cache-read use the 2x input tier; output uses the 1.5x tier.
@@ -542,7 +542,7 @@ func TestTryModelFilePricing_AppliesServiceTierPricing(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			result := tryModelFilePricing(bs, "gpt-5.6-sol", tokens, tt.serviceTier)
+			result := tryModelFilePricing(bs, "gpt-5.6-sol", tokens, tt.serviceTier, time.Time{})
 			require.NotNil(t, result)
 			require.InDelta(t, tt.want, *result, 1e-12)
 		})
@@ -572,7 +572,7 @@ func TestTryModelFilePricing_CombinesPriorityAndLongContextPricing(t *testing.T)
 		CacheReadTokens:     5,
 	}
 
-	result := tryModelFilePricing(bs, "gpt-5.6-sol", tokens, "priority")
+	result := tryModelFilePricing(bs, "gpt-5.6-sol", tokens, "priority", time.Time{})
 
 	require.NotNil(t, result)
 	// priority 单价先应用，再叠加长上下文输入 2x、输出 1.5x。
@@ -583,7 +583,7 @@ func TestTryModelFilePricing_PricingNotFound(t *testing.T) {
 	// "nonexistent-model" does not match any fallback pattern
 	bs := newTestBillingServiceWithPrices(map[string]*ModelPricing{})
 	tokens := UsageTokens{InputTokens: 100, OutputTokens: 50}
-	result := tryModelFilePricing(bs, "nonexistent-model", tokens, "")
+	result := tryModelFilePricing(bs, "nonexistent-model", tokens, "", time.Time{})
 	require.Nil(t, result)
 }
 
@@ -593,7 +593,7 @@ func TestTryModelFilePricing_NilFallback(t *testing.T) {
 		"claude-sonnet-4": nil,
 	})
 	tokens := UsageTokens{InputTokens: 100}
-	result := tryModelFilePricing(bs, "claude-sonnet-4", tokens, "")
+	result := tryModelFilePricing(bs, "claude-sonnet-4", tokens, "", time.Time{})
 	require.Nil(t, result)
 }
 
@@ -605,7 +605,7 @@ func TestTryModelFilePricing_ZeroCost(t *testing.T) {
 		},
 	})
 	tokens := UsageTokens{} // all zero tokens → cost = 0 → nil
-	result := tryModelFilePricing(bs, "claude-sonnet-4", tokens, "")
+	result := tryModelFilePricing(bs, "claude-sonnet-4", tokens, "", time.Time{})
 	require.Nil(t, result)
 }
 
@@ -622,7 +622,7 @@ func TestTryModelFilePricing_WithImageOutput(t *testing.T) {
 		OutputTokens:      50,
 		ImageOutputTokens: 10,
 	}
-	result := tryModelFilePricing(bs, "claude-sonnet-4", tokens, "")
+	result := tryModelFilePricing(bs, "claude-sonnet-4", tokens, "", time.Time{})
 	require.NotNil(t, result)
 	// ImageOutputTokens 是 OutputTokens 的子集，先扣除再按图片单价计。
 	// 100*0.001 + (50-10)*0.002 + 10*0.01 = 0.1 + 0.08 + 0.1 = 0.28
@@ -644,13 +644,111 @@ func TestTryModelFilePricing_WithCacheTokens(t *testing.T) {
 		CacheCreationTokens: 200,
 		CacheReadTokens:     300,
 	}
-	result := tryModelFilePricing(bs, "claude-sonnet-4", tokens, "")
+	result := tryModelFilePricing(bs, "claude-sonnet-4", tokens, "", time.Time{})
 	require.NotNil(t, result)
 	// 100*0.001 + 50*0.002 + 200*0.003 + 300*0.0005
 	// = 0.1 + 0.1 + 0.6 + 0.15 = 0.95
 	require.InDelta(t, 0.95, *result, 1e-12)
 }
 
+func TestTryModelFilePricing_DeepSeekPeakPricing(t *testing.T) {
+	weekday := func(hour, minute int) time.Time {
+		return time.Date(2026, time.August, 24, hour, minute, 0, 0, time.UTC)
+	}
+	for _, model := range []struct {
+		name                          string
+		input, output, cacheReadPrice float64
+	}{
+		{"deepseek-v4-flash", 2.2e-7, 6.6e-7, 7e-9},
+		{"deepseek-v4-pro", 6.6e-7, 1.98e-6, 2.2e-8},
+	} {
+		for _, usage := range []struct {
+			name   string
+			tokens UsageTokens
+		}{
+			{"input", UsageTokens{InputTokens: 1000}},
+			{"output", UsageTokens{OutputTokens: 500}},
+			{"cache_read", UsageTokens{CacheReadTokens: 1000}},
+			{"mixed", UsageTokens{InputTokens: 1000, OutputTokens: 500, CacheReadTokens: 1000}},
+		} {
+			t.Run(model.name+"/"+usage.name, func(t *testing.T) {
+				bs := newTestBillingService()
+				tokens := usage.tokens
+				baseCost := float64(tokens.InputTokens)*model.input +
+					float64(tokens.OutputTokens)*model.output + float64(tokens.CacheReadTokens)*model.cacheReadPrice
+				for _, slot := range []struct {
+					name       string
+					at         time.Time
+					multiplier float64
+				}{
+					{"before_morning_peak", weekday(0, 59), 1},
+					{"morning_peak_start", weekday(1, 0), 2},
+					{"morning_peak_last_minute", weekday(3, 59), 2},
+					{"morning_peak_end", weekday(4, 0), 1},
+					{"afternoon_peak_start", weekday(6, 0), 2},
+					{"afternoon_peak_last_minute", weekday(9, 59), 2},
+					{"afternoon_peak_end", weekday(10, 0), 1},
+					{"saturday", time.Date(2026, time.August, 22, 2, 0, 0, 0, time.UTC), 1},
+					{"sunday", time.Date(2026, time.August, 23, 7, 0, 0, 0, time.UTC), 1},
+				} {
+					t.Run(slot.name, func(t *testing.T) {
+						cost := tryModelFilePricing(bs, model.name, tokens, "", slot.at)
+						require.NotNil(t, cost)
+						require.InDelta(t, baseCost*slot.multiplier, *cost, 1e-12)
+					})
+				}
+			})
+		}
+	}
+}
+
+func TestResolveAccountStatsCost_DeepSeekPricingPriority(t *testing.T) {
+	peak := time.Date(2026, time.August, 24, 2, 0, 0, 0, time.UTC)
+	for _, tt := range []struct {
+		name         string
+		customRule   bool
+		applyPricing bool
+		noChannel    bool
+		want         float64
+	}{
+		{name: "catalog", want: 1000 * 2.2e-7 * 2},
+		{name: "custom_rule", customRule: true, want: 1},
+		{name: "custom_rule_before_customer_price", customRule: true, applyPricing: true, want: 1},
+		{name: "customer_price", applyPricing: true, want: 0.75},
+		{name: "no_channel", noChannel: true},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			channel := &Channel{
+				ID: 1, Status: StatusActive, ApplyPricingToAccountStats: tt.applyPricing,
+				ModelPricing: []ChannelModelPricing{{
+					Models: []string{"deepseek-v4-flash"}, InputPrice: testPtrFloat64(0.02),
+				}},
+			}
+			if tt.customRule {
+				channel.AccountStatsPricingRules = []AccountStatsPricingRule{{
+					AccountIDs: []int64{1},
+					Pricing: []ChannelModelPricing{{
+						Models: []string{"deepseek-v4-flash"}, InputPrice: testPtrFloat64(0.001),
+					}},
+				}}
+			}
+			cs := newTestChannelServiceForStats(t, channel, 10, PlatformDeepseek)
+			groupID := int64(10)
+			if tt.noChannel {
+				groupID = 99
+			}
+			cost := resolveAccountStatsCost(context.Background(), cs, newTestBillingService(),
+				1, groupID, "deepseek-v4-flash", UsageTokens{InputTokens: 1000}, 1, 0.75, "", peak)
+			if tt.noChannel {
+				require.Nil(t, cost)
+				return
+			}
+			require.NotNil(t, cost)
+			require.InDelta(t, tt.want, *cost, 1e-12)
+		})
+	}
+}
+
 // ---------------------------------------------------------------------------
 // resolveAccountStatsCost — integration tests covering the 4-level priority chain
 // ---------------------------------------------------------------------------
@@ -661,7 +759,7 @@ func TestResolveAccountStatsCost_NilChannelService(t *testing.T) {
 		nil, // channelService is nil
 		newTestBillingServiceWithPrices(map[string]*ModelPricing{}),
 		1, 1, "claude-sonnet-4",
-		UsageTokens{InputTokens: 100}, 1, 0.5, "",
+		UsageTokens{InputTokens: 100}, 1, 0.5, "", time.Time{},
 	)
 	require.Nil(t, result)
 }
@@ -677,7 +775,7 @@ func TestResolveAccountStatsCost_EmptyUpstreamModel(t *testing.T) {
 		cs,
 		newTestBillingServiceWithPrices(map[string]*ModelPricing{}),
 		1, 1, "", // empty upstream model
-		UsageTokens{InputTokens: 100}, 1, 0.5, "",
+		UsageTokens{InputTokens: 100}, 1, 0.5, "", time.Time{},
 	)
 	require.Nil(t, result)
 }
@@ -694,7 +792,7 @@ func TestResolveAccountStatsCost_GetChannelForGroupReturnsNil(t *testing.T) {
 		cs,
 		newTestBillingServiceWithPrices(map[string]*ModelPricing{}),
 		1, 99, "claude-sonnet-4", // groupID 99 has no channel
-		UsageTokens{InputTokens: 100}, 1, 0.5, "",
+		UsageTokens{InputTokens: 100}, 1, 0.5, "", time.Time{},
 	)
 	require.Nil(t, result)
 }
@@ -725,7 +823,7 @@ func TestResolveAccountStatsCost_HitsCustomRule(t *testing.T) {
 		context.Background(),
 		cs, nil, // billingService not needed when custom rule hits
 		1, 10, "claude-sonnet-4",
-		tokens, 1, 999.0, "priority", // 自定义账号价格不叠加服务层级倍率
+		tokens, 1, 999.0, "priority", time.Time{}, // 自定义账号价格不叠加服务层级倍率
 	)
 	require.NotNil(t, result)
 	// 100*0.01 + 50*0.02 = 1.0 + 1.0 = 2.0
@@ -747,7 +845,7 @@ func TestResolveAccountStatsCost_ApplyPricingToAccountStats_UsesTotalCost(t *tes
 		context.Background(),
 		cs, nil,
 		1, 10, "claude-sonnet-4",
-		tokens, 1, 0.75, "priority", // 已完成用户计费，不再重复应用服务层级倍率
+		tokens, 1, 0.75, "priority", time.Time{}, // 已完成用户计费，不再重复应用服务层级倍率
 	)
 	require.NotNil(t, result)
 	require.InDelta(t, 0.75, *result, 1e-12)
@@ -765,7 +863,7 @@ func TestResolveAccountStatsCost_ApplyPricingToAccountStats_ZeroTotalCost_Return
 		context.Background(),
 		cs, nil,
 		1, 10, "claude-sonnet-4",
-		UsageTokens{}, 1, 0.0, "", // totalCost = 0
+		UsageTokens{}, 1, 0.0, "", time.Time{}, // totalCost = 0
 	)
 	require.Nil(t, result)
 }
@@ -792,7 +890,7 @@ func TestResolveAccountStatsCost_FallsBackToLiteLLM(t *testing.T) {
 		context.Background(),
 		cs, bs,
 		1, 10, "claude-sonnet-4",
-		tokens, 1, 999.0, "", // totalCost ignored
+		tokens, 1, 999.0, "", time.Time{}, // totalCost ignored
 	)
 	require.NotNil(t, result)
 	// 100*0.001 + 50*0.002 = 0.1 + 0.1 = 0.2
@@ -813,7 +911,7 @@ func TestResolveAccountStatsCost_FallbackHonorsAnthropicFast(t *testing.T) {
 		context.Background(), cs, bs,
 		1, 10, "claude-opus-5",
 		UsageTokens{InputTokens: 1_000_000, OutputTokens: 1_000_000},
-		1, 0, "fast",
+		1, 0, "fast", time.Time{},
 	)
 	require.NotNil(t, result)
 	require.InDelta(t, 60, *result, 1e-12)
@@ -832,7 +930,7 @@ func TestResolveAccountStatsCost_Gemini36FlashTierUsesFallbackPricing(t *testing
 		context.Background(),
 		cs, bs,
 		1, 10, "gemini-3.6-flash-low",
-		UsageTokens{InputTokens: 1_000_000, OutputTokens: 1_000_000, CacheReadTokens: 1_000_000}, 1, 0, "",
+		UsageTokens{InputTokens: 1_000_000, OutputTokens: 1_000_000, CacheReadTokens: 1_000_000}, 1, 0, "", time.Time{},
 	)
 	require.NotNil(t, result)
 	require.InDelta(t, 9.15, *result, 1e-12)
@@ -856,7 +954,7 @@ func TestResolveAccountStatsCost_AllMiss_ReturnsNil(t *testing.T) {
 		context.Background(),
 		cs, bs,
 		1, 10, "totally-unknown-model",
-		tokens, 1, 0.0, "",
+		tokens, 1, 0.0, "", time.Time{},
 	)
 	require.Nil(t, result)
 }
@@ -873,7 +971,7 @@ func TestResolveAccountStatsCost_NilBillingService_SkipsLiteLLM(t *testing.T) {
 		context.Background(),
 		cs, nil, // billingService is nil
 		1, 10, "claude-sonnet-4",
-		UsageTokens{InputTokens: 100}, 1, 0.0, "",
+		UsageTokens{InputTokens: 100}, 1, 0.0, "", time.Time{},
 	)
 	require.Nil(t, result)
 }
@@ -906,7 +1004,7 @@ func TestResolveAccountStatsCost_CustomRulePriorityOverApplyPricing(t *testing.T
 		context.Background(),
 		cs, nil,
 		1, 10, "claude-sonnet-4",
-		tokens, 1, 99.0, "", // totalCost = 99.0 (would be used if ApplyPricing wins)
+		tokens, 1, 99.0, "", time.Time{}, // 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)
@@ -934,7 +1032,7 @@ func TestApplyAccountStatsCost_UsesUsageLogServiceTier(t *testing.T) {
 	applyAccountStatsCost(
 		context.Background(), usageLog, cs, bs,
 		1, 10, "gpt-5.6-sol", "gpt-5.6-sol",
-		UsageTokens{InputTokens: 100, OutputTokens: 50}, 999,
+		UsageTokens{InputTokens: 100, OutputTokens: 50}, 999, time.Time{},
 	)
 
 	require.NotNil(t, usageLog.AccountStatsCost)

backend/internal/service/gateway_record_usage_test.go

@@ -460,6 +460,69 @@ func TestGatewayServiceRecordUsage_UsesExplicitPricingAtForPeakRate(t *testing.T
 	}
 }
 
+func TestGatewayServiceRecordUsage_DeepSeekAccountStatsUsesRequestPricingAtAndUpstreamModel(t *testing.T) {
+	for _, model := range []struct {
+		name        string
+		offPeakCost float64
+	}{
+		{"deepseek-v4-flash", 1000*2.2e-7 + 500*6.6e-7 + 1000*7e-9},
+		{"deepseek-v4-pro", 1000*6.6e-7 + 500*1.98e-6 + 1000*2.2e-8},
+	} {
+		for _, slot := range []struct {
+			name       string
+			pricingAt  time.Time
+			multiplier float64
+		}{
+			{"peak", time.Date(2026, time.August, 24, 2, 0, 0, 0, time.UTC), 2},
+			{"off_peak", time.Date(2026, time.August, 24, 12, 0, 0, 0, time.UTC), 1},
+		} {
+			t.Run(model.name+"/"+slot.name, func(t *testing.T) {
+				usageRepo := &openAIRecordUsageLogRepoStub{inserted: true}
+				userRepo := &openAIRecordUsageUserRepoStub{}
+				svc := newGatewayRecordUsageServiceForTest(usageRepo, userRepo, &openAIRecordUsageSubRepoStub{})
+				groupID := int64(905)
+				svc.channelService = newTestChannelServiceForStats(t, &Channel{ID: 1, Status: StatusActive}, groupID, PlatformDeepseek)
+				svc.resolver = NewModelPricingResolver(svc.channelService, svc.billingService)
+				alias := "customer-chat"
+				inputPrice, outputPrice, cachePrice := 1e-6, 2e-6, 1e-7
+				group := &Group{ID: groupID, Platform: PlatformDeepseek, RateMultiplier: 0.8,
+					ModelPricing: []ChannelModelPricing{{
+						Models: []string{alias}, BillingMode: BillingModeToken,
+						InputPrice: &inputPrice, OutputPrice: &outputPrice, CacheReadPrice: &cachePrice,
+					}},
+				}
+				err := svc.RecordUsage(context.Background(), &RecordUsageInput{
+					Result: &ForwardResult{
+						RequestID: "gateway_deepseek_account_stats_" + model.name + "_" + slot.name,
+						Model:     alias, UpstreamModel: model.name,
+						Usage: ClaudeUsage{InputTokens: 1000, OutputTokens: 500, CacheReadInputTokens: 1000},
+					},
+					APIKey: &APIKey{ID: 805, GroupID: &groupID, Group: group},
+					User:   &User{ID: 605}, Account: &Account{ID: 705, Platform: PlatformDeepseek},
+					PricingAt:          slot.pricingAt,
+					ChannelUsageFields: ChannelUsageFields{OriginalModel: alias, BillingModelSource: BillingModelSourceRequested},
+				})
+				require.NoError(t, err)
+				require.NotNil(t, usageRepo.lastLog)
+				log := usageRepo.lastLog
+				require.Equal(t, alias, log.RequestedModel)
+				require.NotNil(t, log.UpstreamModel)
+				require.Equal(t, model.name, *log.UpstreamModel)
+				require.WithinDuration(t, time.Now(), log.CreatedAt, time.Minute)
+				require.False(t, log.CreatedAt.Equal(slot.pricingAt), "request pricing time must differ from record creation")
+				customerTotal := 1000*inputPrice + 500*outputPrice + 1000*cachePrice
+				require.InDelta(t, customerTotal, log.TotalCost, 1e-12)
+				require.InDelta(t, customerTotal*0.8, log.ActualCost, 1e-12)
+				require.Equal(t, 1, userRepo.deductCalls)
+				require.InDelta(t, customerTotal*0.8, userRepo.lastAmount, 1e-12)
+				require.NotNil(t, log.AccountStatsCost)
+				require.InDelta(t, model.offPeakCost*slot.multiplier, *log.AccountStatsCost, 1e-12,
+					"account cost must use the upstream model and historical PricingAt")
+			})
+		}
+	}
+}
+
 func TestGatewayServiceRecordUsage_UsageLogWriteErrorDoesNotSkipBilling(t *testing.T) {
 	usageRepo := &openAIRecordUsageLogRepoStub{inserted: false, err: MarkUsageLogCreateNotPersisted(context.Canceled)}
 	userRepo := &openAIRecordUsageUserRepoStub{}

backend/internal/service/gateway_usage_billing.go

@@ -831,7 +831,7 @@ func (s *GatewayService) recordUsageCore(ctx context.Context, input *recordUsage
 				CacheReadTokens:     result.Usage.CacheReadInputTokens,
 				ImageOutputTokens:   result.Usage.ImageOutputTokens,
 			},
-			cost.TotalCost,
+			cost.TotalCost, pricingAt,
 		)
 	}
 

backend/internal/service/openai_gateway_record_usage_test.go

@@ -569,6 +569,75 @@ func TestOpenAIGatewayServiceRecordUsage_TimePricingUsesExplicitPricingAt(t *tes
 	require.InDelta(t, baseCost*0.8, usageRepo.lastLog.ActualCost, 1e-12)
 	require.InDelta(t, 0.8, usageRepo.lastLog.RateMultiplier, 1e-12)
 }
+
+func TestOpenAIGatewayServiceRecordUsage_DeepSeekAccountStatsUsesRequestPricingAtAndUpstreamModel(t *testing.T) {
+	for _, model := range []struct {
+		name        string
+		offPeakCost float64
+	}{
+		{"deepseek-v4-flash", 1000*2.2e-7 + 500*6.6e-7 + 1000*7e-9},
+		{"deepseek-v4-pro", 1000*6.6e-7 + 500*1.98e-6 + 1000*2.2e-8},
+	} {
+		for _, slot := range []struct {
+			name       string
+			pricingAt  time.Time
+			multiplier float64
+		}{
+			{"peak", time.Date(2026, time.August, 24, 2, 0, 0, 0, time.UTC), 2},
+			{"off_peak", time.Date(2026, time.August, 24, 12, 0, 0, 0, time.UTC), 1},
+		} {
+			t.Run(model.name+"/"+slot.name, func(t *testing.T) {
+				usageRepo := &openAIRecordUsageLogRepoStub{inserted: true}
+				userRepo := &openAIRecordUsageUserRepoStub{}
+				svc := newOpenAIRecordUsageServiceForTest(usageRepo, userRepo, &openAIRecordUsageSubRepoStub{}, nil)
+				groupID := int64(18)
+				cache := newEmptyChannelCache()
+				cache.channelByGroupID[groupID] = &Channel{ID: 1, Status: StatusActive}
+				cache.groupPlatform[groupID] = PlatformDeepseek
+				cache.loadedAt = time.Now()
+				svc.channelService = &ChannelService{}
+				svc.channelService.cache.Store(cache)
+				svc.resolver = NewModelPricingResolver(svc.channelService, svc.billingService)
+				alias := "customer-chat"
+				inputPrice, outputPrice, cachePrice := 1e-6, 2e-6, 1e-7
+				group := &Group{ID: groupID, Platform: PlatformDeepseek, RateMultiplier: 0.8,
+					ModelPricing: []ChannelModelPricing{{
+						Models: []string{alias}, BillingMode: BillingModeToken,
+						InputPrice: &inputPrice, OutputPrice: &outputPrice, CacheReadPrice: &cachePrice,
+					}},
+				}
+				err := svc.RecordUsage(context.Background(), &OpenAIRecordUsageInput{
+					Result: &OpenAIForwardResult{
+						RequestID: "openai_deepseek_account_stats_" + model.name + "_" + slot.name,
+						Model:     alias, BillingModel: alias, UpstreamModel: model.name,
+						Usage: OpenAIUsage{InputTokens: 2000, OutputTokens: 500, CacheReadInputTokens: 1000},
+					},
+					APIKey: &APIKey{ID: 1008, GroupID: &groupID, Group: group},
+					User:   &User{ID: 2008}, Account: &Account{ID: 3008, Platform: PlatformDeepseek},
+					PricingAt:          slot.pricingAt,
+					ChannelUsageFields: ChannelUsageFields{OriginalModel: alias, BillingModelSource: BillingModelSourceRequested},
+				})
+				require.NoError(t, err)
+				require.NotNil(t, usageRepo.lastLog)
+				log := usageRepo.lastLog
+				require.Equal(t, alias, log.RequestedModel)
+				require.NotNil(t, log.UpstreamModel)
+				require.Equal(t, model.name, *log.UpstreamModel)
+				require.WithinDuration(t, time.Now(), log.CreatedAt, time.Minute)
+				require.False(t, log.CreatedAt.Equal(slot.pricingAt), "request pricing time must differ from record creation")
+				customerTotal := 1000*inputPrice + 500*outputPrice + 1000*cachePrice
+				require.InDelta(t, customerTotal, log.TotalCost, 1e-12)
+				require.InDelta(t, customerTotal*0.8, log.ActualCost, 1e-12)
+				require.Equal(t, 1, userRepo.deductCalls)
+				require.InDelta(t, customerTotal*0.8, userRepo.lastAmount, 1e-12)
+				require.NotNil(t, log.AccountStatsCost)
+				require.InDelta(t, model.offPeakCost*slot.multiplier, *log.AccountStatsCost, 1e-12,
+					"account cost must use the upstream model and historical PricingAt")
+			})
+		}
+	}
+}
+
 func TestOpenAIGatewayServiceRecordUsage_IncludesEndpointMetadata(t *testing.T) {
 	usageRepo := &openAIRecordUsageLogRepoStub{inserted: true}
 	userRepo := &openAIRecordUsageUserRepoStub{}

backend/internal/service/openai_gateway_usage.go

@@ -472,7 +472,7 @@ func (s *OpenAIGatewayService) RecordUsage(ctx context.Context, input *OpenAIRec
 	if apiKey.GroupID != nil {
 		applyAccountStatsCost(ctx, usageLog, s.channelService, s.billingService,
 			account.ID, *apiKey.GroupID, result.UpstreamModel, result.Model,
-			tokens, cost.TotalCost,
+			tokens, cost.TotalCost, pricingAt,
 		)
 	}