feat(api): expose model_source filter in dashboard endpoints

Add model_source query parameter to GetModelStats and GetUserBreakdown handlers with explicit IsValidModelSource validation. Include model_source in cache key to prevent cross-source cache hits. Expose upstream_model in usage log DTO with omitempty semantics.

backend/internal/handler/admin/dashboard_handler.go

@@ -273,6 +273,7 @@ func (h *DashboardHandler) GetModelStats(c *gin.Context) {
 
 	// Parse optional filter params
 	var userID, apiKeyID, accountID, groupID int64
+	modelSource := usagestats.ModelSourceRequested
 	var requestType *int16
 	var stream *bool
 	var billingType *int8
@@ -297,6 +298,13 @@ func (h *DashboardHandler) GetModelStats(c *gin.Context) {
 			groupID = id
 		}
 	}
+	if rawModelSource := strings.TrimSpace(c.Query("model_source")); rawModelSource != "" {
+		if !usagestats.IsValidModelSource(rawModelSource) {
+			response.BadRequest(c, "Invalid model_source, use requested/upstream/mapping")
+			return
+		}
+		modelSource = rawModelSource
+	}
 	if requestTypeStr := strings.TrimSpace(c.Query("request_type")); requestTypeStr != "" {
 		parsed, err := service.ParseUsageRequestType(requestTypeStr)
 		if err != nil {
@@ -323,7 +331,7 @@ func (h *DashboardHandler) GetModelStats(c *gin.Context) {
 		}
 	}
 
-	stats, hit, err := h.getModelStatsCached(c.Request.Context(), startTime, endTime, userID, apiKeyID, accountID, groupID, requestType, stream, billingType)
+	stats, hit, err := h.getModelStatsCached(c.Request.Context(), startTime, endTime, userID, apiKeyID, accountID, groupID, modelSource, requestType, stream, billingType)
 	if err != nil {
 		response.Error(c, 500, "Failed to get model statistics")
 		return
@@ -619,6 +627,12 @@ func (h *DashboardHandler) GetUserBreakdown(c *gin.Context) {
 		}
 	}
 	dim.Model = c.Query("model")
+	rawModelSource := strings.TrimSpace(c.DefaultQuery("model_source", usagestats.ModelSourceRequested))
+	if !usagestats.IsValidModelSource(rawModelSource) {
+		response.BadRequest(c, "Invalid model_source, use requested/upstream/mapping")
+		return
+	}
+	dim.ModelType = rawModelSource
 	dim.Endpoint = c.Query("endpoint")
 	dim.EndpointType = c.DefaultQuery("endpoint_type", "inbound")
 

backend/internal/handler/admin/dashboard_query_cache.go

@@ -38,6 +38,7 @@ type dashboardModelGroupCacheKey struct {
 	APIKeyID    int64  `json:"api_key_id"`
 	AccountID   int64  `json:"account_id"`
 	GroupID     int64  `json:"group_id"`
+	ModelSource string `json:"model_source,omitempty"`
 	RequestType *int16 `json:"request_type"`
 	Stream      *bool  `json:"stream"`
 	BillingType *int8  `json:"billing_type"`
@@ -111,6 +112,7 @@ func (h *DashboardHandler) getModelStatsCached(
 	ctx context.Context,
 	startTime, endTime time.Time,
 	userID, apiKeyID, accountID, groupID int64,
+	modelSource string,
 	requestType *int16,
 	stream *bool,
 	billingType *int8,
@@ -122,12 +124,13 @@ func (h *DashboardHandler) getModelStatsCached(
 		APIKeyID:    apiKeyID,
 		AccountID:   accountID,
 		GroupID:     groupID,
+		ModelSource: usagestats.NormalizeModelSource(modelSource),
 		RequestType: requestType,
 		Stream:      stream,
 		BillingType: billingType,
 	})
 	entry, hit, err := dashboardModelStatsCache.GetOrLoad(key, func() (any, error) {
-		return h.dashboardService.GetModelStatsWithFilters(ctx, startTime, endTime, userID, apiKeyID, accountID, groupID, requestType, stream, billingType)
+		return h.dashboardService.GetModelStatsWithFiltersBySource(ctx, startTime, endTime, userID, apiKeyID, accountID, groupID, requestType, stream, billingType, modelSource)
 	})
 	if err != nil {
 		return nil, hit, err

backend/internal/handler/admin/dashboard_snapshot_v2_handler.go

@@ -200,6 +200,7 @@ func (h *DashboardHandler) buildSnapshotV2Response(
 			filters.APIKeyID,
 			filters.AccountID,
 			filters.GroupID,
+			usagestats.ModelSourceRequested,
 			filters.RequestType,
 			filters.Stream,
 			filters.BillingType,

backend/internal/handler/dto/mappers.go

@@ -521,6 +521,7 @@ func usageLogFromServiceUser(l *service.UsageLog) UsageLog {
 		AccountID:             l.AccountID,
 		RequestID:             l.RequestID,
 		Model:                 l.Model,
+		UpstreamModel:         l.UpstreamModel,
 		ServiceTier:           l.ServiceTier,
 		ReasoningEffort:       l.ReasoningEffort,
 		InboundEndpoint:       l.InboundEndpoint,

backend/internal/handler/dto/types.go

@@ -332,6 +332,9 @@ type UsageLog struct {
 	AccountID int64  `json:"account_id"`
 	RequestID string `json:"request_id"`
 	Model     string `json:"model"`
+	// UpstreamModel is the actual model sent to the upstream provider after mapping.
+	// Omitted when no mapping was applied (requested model was used as-is).
+	UpstreamModel *string `json:"upstream_model,omitempty"`
 	// ServiceTier records the OpenAI service tier used for billing, e.g. "priority" / "flex".
 	ServiceTier *string `json:"service_tier,omitempty"`
 	// ReasoningEffort is the request's reasoning effort level.