diff --git a/internal/gateway/methods/agents_create.go b/internal/gateway/methods/agents_create.go
index b5c054f9..3bbd3378 100644
--- a/internal/gateway/methods/agents_create.go
+++ b/internal/gateway/methods/agents_create.go
@@ -84,19 +84,19 @@ func (m *AgentsMethods) handleCreate(ctx context.Context, client *gateway.Client
 			ownerID = params.OwnerIDs[0]
 		}
 
-		// Resolve tenant_id: cross-tenant callers must provide it; others inherit their own tenant.
+		// Resolve tenant_id: explicit param for cross-tenant; otherwise inherit from connection scope.
 		var tenantID uuid.UUID
 		if client.IsOwner() {
-			if params.TenantID == "" {
-				client.SendResponse(protocol.NewErrorResponse(req.ID, protocol.ErrInvalidRequest, i18n.T(locale, i18n.MsgRequired, "tenant_id")))
-				return
+			if params.TenantID != "" {
+				tid, err := uuid.Parse(params.TenantID)
+				if err != nil {
+					client.SendResponse(protocol.NewErrorResponse(req.ID, protocol.ErrInvalidRequest, i18n.T(locale, i18n.MsgInvalidID, "tenant_id")))
+					return
+				}
+				tenantID = tid
+			} else {
+				tenantID = client.TenantID()
 			}
-			tid, err := uuid.Parse(params.TenantID)
-			if err != nil {
-				client.SendResponse(protocol.NewErrorResponse(req.ID, protocol.ErrInvalidRequest, i18n.T(locale, i18n.MsgInvalidID, "tenant_id")))
-				return
-			}
-			tenantID = tid
 		} else {
 			tenantID = client.TenantID()
 		}
diff --git a/internal/http/agents.go b/internal/http/agents.go
index 6421cec0..65ff17e8 100644
--- a/internal/http/agents.go
+++ b/internal/http/agents.go
@@ -120,11 +120,10 @@ func (h *AgentsHandler) handleCreate(w http.ResponseWriter, r *http.Request) {
 
 	req.OwnerID = userID
 
-	// Resolve tenant_id: cross-tenant callers must provide it; others inherit their own tenant.
+	// Resolve tenant_id: explicit body field for cross-tenant; otherwise inherit from auth context.
 	if store.IsOwnerRole(r.Context()) {
 		if req.TenantID == uuid.Nil {
-			writeJSON(w, http.StatusBadRequest, map[string]string{"error": i18n.T(locale, i18n.MsgRequired, "tenant_id")})
-			return
+			req.TenantID = store.TenantIDFromContext(r.Context())
 		}
 	} else {
 		req.TenantID = store.TenantIDFromContext(r.Context())