test(backend): add tests for upstream model tracking and model source filtering

Cover IsValidModelSource/NormalizeModelSource, resolveModelDimensionExpression SQL expressions, invalid model_source 400 responses on both GetModelStats and GetUserBreakdown, upstream_model in scan/insert SQL mock expectations, and updated passthrough/billing test signatures.

backend/internal/handler/admin/dashboard_handler_request_type_test.go

@@ -149,6 +149,28 @@ func TestDashboardModelStatsInvalidStream(t *testing.T) {
 	require.Equal(t, http.StatusBadRequest, rec.Code)
 }
 
+func TestDashboardModelStatsInvalidModelSource(t *testing.T) {
+	repo := &dashboardUsageRepoCapture{}
+	router := newDashboardRequestTypeTestRouter(repo)
+
+	req := httptest.NewRequest(http.MethodGet, "/admin/dashboard/models?model_source=invalid", nil)
+	rec := httptest.NewRecorder()
+	router.ServeHTTP(rec, req)
+
+	require.Equal(t, http.StatusBadRequest, rec.Code)
+}
+
+func TestDashboardModelStatsValidModelSource(t *testing.T) {
+	repo := &dashboardUsageRepoCapture{}
+	router := newDashboardRequestTypeTestRouter(repo)
+
+	req := httptest.NewRequest(http.MethodGet, "/admin/dashboard/models?model_source=upstream", nil)
+	rec := httptest.NewRecorder()
+	router.ServeHTTP(rec, req)
+
+	require.Equal(t, http.StatusOK, rec.Code)
+}
+
 func TestDashboardUsersRankingLimitAndCache(t *testing.T) {
 	dashboardUsersRankingCache = newSnapshotCache(5 * time.Minute)
 	repo := &dashboardUsageRepoCapture{

backend/internal/handler/admin/dashboard_handler_user_breakdown_test.go

@@ -73,9 +73,35 @@ func TestGetUserBreakdown_ModelFilter(t *testing.T) {
 
 	require.Equal(t, http.StatusOK, w.Code)
 	require.Equal(t, "claude-opus-4-6", repo.capturedDim.Model)
+	require.Equal(t, usagestats.ModelSourceRequested, repo.capturedDim.ModelType)
 	require.Equal(t, int64(0), repo.capturedDim.GroupID)
 }
 
+func TestGetUserBreakdown_ModelSourceFilter(t *testing.T) {
+	repo := &userBreakdownRepoCapture{}
+	router := newUserBreakdownRouter(repo)
+
+	req := httptest.NewRequest(http.MethodGet,
+		"/admin/dashboard/user-breakdown?start_date=2026-03-01&end_date=2026-03-16&model=claude-opus-4-6&model_source=upstream", nil)
+	w := httptest.NewRecorder()
+	router.ServeHTTP(w, req)
+
+	require.Equal(t, http.StatusOK, w.Code)
+	require.Equal(t, usagestats.ModelSourceUpstream, repo.capturedDim.ModelType)
+}
+
+func TestGetUserBreakdown_InvalidModelSource(t *testing.T) {
+	repo := &userBreakdownRepoCapture{}
+	router := newUserBreakdownRouter(repo)
+
+	req := httptest.NewRequest(http.MethodGet,
+		"/admin/dashboard/user-breakdown?start_date=2026-03-01&end_date=2026-03-16&model_source=foobar", nil)
+	w := httptest.NewRecorder()
+	router.ServeHTTP(w, req)
+
+	require.Equal(t, http.StatusBadRequest, w.Code)
+}
+
 func TestGetUserBreakdown_EndpointFilter(t *testing.T) {
 	repo := &userBreakdownRepoCapture{}
 	router := newUserBreakdownRouter(repo)

backend/internal/pkg/usagestats/usage_log_types_test.go

@@ -0,0 +1,47 @@
+package usagestats
+
+import "testing"
+
+func TestIsValidModelSource(t *testing.T) {
+	tests := []struct {
+		name   string
+		source string
+		want   bool
+	}{
+		{name: "requested", source: ModelSourceRequested, want: true},
+		{name: "upstream", source: ModelSourceUpstream, want: true},
+		{name: "mapping", source: ModelSourceMapping, want: true},
+		{name: "invalid", source: "foobar", want: false},
+		{name: "empty", source: "", want: false},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := IsValidModelSource(tc.source); got != tc.want {
+				t.Fatalf("IsValidModelSource(%q)=%v want %v", tc.source, got, tc.want)
+			}
+		})
+	}
+}
+
+func TestNormalizeModelSource(t *testing.T) {
+	tests := []struct {
+		name   string
+		source string
+		want   string
+	}{
+		{name: "requested", source: ModelSourceRequested, want: ModelSourceRequested},
+		{name: "upstream", source: ModelSourceUpstream, want: ModelSourceUpstream},
+		{name: "mapping", source: ModelSourceMapping, want: ModelSourceMapping},
+		{name: "invalid falls back", source: "foobar", want: ModelSourceRequested},
+		{name: "empty falls back", source: "", want: ModelSourceRequested},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := NormalizeModelSource(tc.source); got != tc.want {
+				t.Fatalf("NormalizeModelSource(%q)=%q want %q", tc.source, got, tc.want)
+			}
+		})
+	}
+}

backend/internal/repository/usage_log_repo_breakdown_test.go

@@ -5,6 +5,7 @@ package repository
 import (
 	"testing"
 
+	"github.com/Wei-Shaw/sub2api/internal/pkg/usagestats"
 	"github.com/stretchr/testify/require"
 )
 
@@ -16,8 +17,8 @@ func TestResolveEndpointColumn(t *testing.T) {
 		{"inbound", "ul.inbound_endpoint"},
 		{"upstream", "ul.upstream_endpoint"},
 		{"path", "ul.inbound_endpoint || ' -> ' || ul.upstream_endpoint"},
-		{"", "ul.inbound_endpoint"},           // default
-		{"unknown", "ul.inbound_endpoint"},     // fallback
+		{"", "ul.inbound_endpoint"},        // default
+		{"unknown", "ul.inbound_endpoint"}, // fallback
 	}
 
 	for _, tc := range tests {
@@ -27,3 +28,23 @@ func TestResolveEndpointColumn(t *testing.T) {
 		})
 	}
 }
+
+func TestResolveModelDimensionExpression(t *testing.T) {
+	tests := []struct {
+		modelType string
+		want      string
+	}{
+		{usagestats.ModelSourceRequested, "model"},
+		{usagestats.ModelSourceUpstream, "COALESCE(NULLIF(TRIM(upstream_model), ''), model)"},
+		{usagestats.ModelSourceMapping, "(model || ' -> ' || COALESCE(NULLIF(TRIM(upstream_model), ''), model))"},
+		{"", "model"},
+		{"invalid", "model"},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.modelType, func(t *testing.T) {
+			got := resolveModelDimensionExpression(tc.modelType)
+			require.Equal(t, tc.want, got)
+		})
+	}
+}

backend/internal/repository/usage_log_repo_request_type_test.go

@@ -44,6 +44,7 @@ func TestUsageLogRepositoryCreateSyncRequestTypeAndLegacyFields(t *testing.T) {
 			log.AccountID,
 			log.RequestID,
 			log.Model,
+			sqlmock.AnyArg(), // upstream_model
 			sqlmock.AnyArg(), // group_id
 			sqlmock.AnyArg(), // subscription_id
 			log.InputTokens,
@@ -116,6 +117,7 @@ func TestUsageLogRepositoryCreate_PersistsServiceTier(t *testing.T) {
 			log.Model,
 			sqlmock.AnyArg(),
 			sqlmock.AnyArg(),
+			sqlmock.AnyArg(),
 			log.InputTokens,
 			log.OutputTokens,
 			log.CacheCreationTokens,
@@ -353,6 +355,7 @@ func TestScanUsageLogRequestTypeAndLegacyFallback(t *testing.T) {
 			int64(30), // account_id
 			sql.NullString{Valid: true, String: "req-1"},
 			"gpt-5",           // model
+			sql.NullString{},  // upstream_model
 			sql.NullInt64{},   // group_id
 			sql.NullInt64{},   // subscription_id
 			1,                 // input_tokens
@@ -404,6 +407,7 @@ func TestScanUsageLogRequestTypeAndLegacyFallback(t *testing.T) {
 			int64(31),
 			sql.NullString{Valid: true, String: "req-2"},
 			"gpt-5",
+			sql.NullString{},
 			sql.NullInt64{},
 			sql.NullInt64{},
 			1, 2, 3, 4, 5, 6,
@@ -445,6 +449,7 @@ func TestScanUsageLogRequestTypeAndLegacyFallback(t *testing.T) {
 			int64(32),
 			sql.NullString{Valid: true, String: "req-3"},
 			"gpt-5.4",
+			sql.NullString{},
 			sql.NullInt64{},
 			sql.NullInt64{},
 			1, 2, 3, 4, 5, 6,

backend/internal/service/gateway_anthropic_apikey_passthrough_test.go

@@ -788,7 +788,7 @@ func TestGatewayService_AnthropicAPIKeyPassthrough_ForwardDirect_NonStreamingSuc
 		rateLimitService: &RateLimitService{},
 	}
 
-	result, err := svc.forwardAnthropicAPIKeyPassthrough(context.Background(), c, newAnthropicAPIKeyAccountForTest(), body, "claude-3-5-sonnet-latest", false, time.Now())
+	result, err := svc.forwardAnthropicAPIKeyPassthrough(context.Background(), c, newAnthropicAPIKeyAccountForTest(), body, "claude-3-5-sonnet-latest", "claude-3-5-sonnet-latest", false, time.Now())
 	require.NoError(t, err)
 	require.NotNil(t, result)
 	require.Equal(t, 12, result.Usage.InputTokens)
@@ -815,7 +815,7 @@ func TestGatewayService_AnthropicAPIKeyPassthrough_ForwardDirect_InvalidTokenTyp
 	}
 	svc := &GatewayService{}
 
-	result, err := svc.forwardAnthropicAPIKeyPassthrough(context.Background(), c, account, []byte(`{}`), "claude-3-5-sonnet-latest", false, time.Now())
+	result, err := svc.forwardAnthropicAPIKeyPassthrough(context.Background(), c, account, []byte(`{}`), "claude-3-5-sonnet-latest", "claude-3-5-sonnet-latest", false, time.Now())
 	require.Nil(t, result)
 	require.Error(t, err)
 	require.Contains(t, err.Error(), "requires apikey token")
@@ -840,7 +840,7 @@ func TestGatewayService_AnthropicAPIKeyPassthrough_ForwardDirect_UpstreamRequest
 	}
 	account := newAnthropicAPIKeyAccountForTest()
 
-	result, err := svc.forwardAnthropicAPIKeyPassthrough(context.Background(), c, account, []byte(`{"model":"x"}`), "x", false, time.Now())
+	result, err := svc.forwardAnthropicAPIKeyPassthrough(context.Background(), c, account, []byte(`{"model":"x"}`), "x", "x", false, time.Now())
 	require.Nil(t, result)
 	require.Error(t, err)
 	require.Contains(t, err.Error(), "upstream request failed")
@@ -873,7 +873,7 @@ func TestGatewayService_AnthropicAPIKeyPassthrough_ForwardDirect_EmptyResponseBo
 		httpUpstream: upstream,
 	}
 
-	result, err := svc.forwardAnthropicAPIKeyPassthrough(context.Background(), c, newAnthropicAPIKeyAccountForTest(), []byte(`{"model":"x"}`), "x", false, time.Now())
+	result, err := svc.forwardAnthropicAPIKeyPassthrough(context.Background(), c, newAnthropicAPIKeyAccountForTest(), []byte(`{"model":"x"}`), "x", "x", false, time.Now())
 	require.Nil(t, result)
 	require.Error(t, err)
 	require.Contains(t, err.Error(), "empty response")

backend/internal/service/openai_gateway_record_usage_test.go

@@ -846,7 +846,7 @@ func TestExtractOpenAIServiceTierFromBody(t *testing.T) {
 	require.Nil(t, extractOpenAIServiceTierFromBody(nil))
 }
 
-func TestOpenAIGatewayServiceRecordUsage_UsesBillingModelAndMetadataFields(t *testing.T) {
+func TestOpenAIGatewayServiceRecordUsage_UsesRequestedModelAndUpstreamModelMetadataFields(t *testing.T) {
 	usageRepo := &openAIRecordUsageLogRepoStub{inserted: true}
 	userRepo := &openAIRecordUsageUserRepoStub{}
 	subRepo := &openAIRecordUsageSubRepoStub{}
@@ -859,6 +859,7 @@ func TestOpenAIGatewayServiceRecordUsage_UsesBillingModelAndMetadataFields(t *te
 			RequestID:       "resp_billing_model_override",
 			BillingModel:    "gpt-5.1-codex",
 			Model:           "gpt-5.1",
+			UpstreamModel:   "gpt-5.1-codex",
 			ServiceTier:     &serviceTier,
 			ReasoningEffort: &reasoning,
 			Usage: OpenAIUsage{
@@ -877,7 +878,9 @@ func TestOpenAIGatewayServiceRecordUsage_UsesBillingModelAndMetadataFields(t *te
 
 	require.NoError(t, err)
 	require.NotNil(t, usageRepo.lastLog)
-	require.Equal(t, "gpt-5.1-codex", usageRepo.lastLog.Model)
+	require.Equal(t, "gpt-5.1", usageRepo.lastLog.Model)
+	require.NotNil(t, usageRepo.lastLog.UpstreamModel)
+	require.Equal(t, "gpt-5.1-codex", *usageRepo.lastLog.UpstreamModel)
 	require.NotNil(t, usageRepo.lastLog.ServiceTier)
 	require.Equal(t, serviceTier, *usageRepo.lastLog.ServiceTier)
 	require.NotNil(t, usageRepo.lastLog.ReasoningEffort)