diff --git a/build/config/substation.libsonnet b/build/config/substation.libsonnet
index 76f56c9c..e2136435 100644
--- a/build/config/substation.libsonnet
+++ b/build/config/substation.libsonnet
@@ -1148,8 +1148,7 @@
             condition=$.cnd.meta.negate({ inspector: $.cnd.fmt.json() }),
             transform=$.tf.util.drop(),
           ),
-          $.tf.agg.to.arr(),
-          $.tf.arr.join({ separator: '\n' }),
+          $.tf.agg.to.string({ separator: '\n' }),
           $.tf.str.append({ suffix: '\n' }),
         ],
       },
diff --git a/transform/aggregate.go b/transform/aggregate.go
index a6ea96e3..a5af3dba 100644
--- a/transform/aggregate.go
+++ b/transform/aggregate.go
@@ -3,10 +3,10 @@ package transform
 import (
 	"bytes"
 	"fmt"
+	"slices"
 
 	iconfig "github.com/brexhq/substation/internal/config"
 	"github.com/brexhq/substation/internal/errors"
-	"github.com/brexhq/substation/message"
 )
 
 type aggregateArrayConfig struct {
@@ -18,17 +18,8 @@ func (c *aggregateArrayConfig) Decode(in interface{}) error {
 	return iconfig.Decode(in, c)
 }
 
-func aggToArray(data [][]byte) ([]byte, error) {
-	msg := message.New()
-
-	for _, d := range data {
-		if err := msg.SetValue("array.-1", d); err != nil {
-			return nil, err
-		}
-	}
-
-	b := msg.GetValue("array")
-	return b.Bytes(), nil
+func aggToArray(data [][]byte) []byte {
+	return slices.Concat([]byte("["), bytes.Join(data, []byte(",")), []byte("]"))
 }
 
 type aggregateStrConfig struct {
diff --git a/transform/aggregate_to_array.go b/transform/aggregate_to_array.go
index 15bf4e2a..4e302986 100644
--- a/transform/aggregate_to_array.go
+++ b/transform/aggregate_to_array.go
@@ -47,23 +47,19 @@ func (tf *aggregateToArray) Transform(ctx context.Context, msg *message.Message)
 	tf.mu.Lock()
 	defer tf.mu.Unlock()
 
-	//nolint: nestif // ignore nesting complexity
 	if msg.IsControl() {
 		var output []*message.Message
 
 		for _, items := range tf.agg.GetAll() {
-			agg, err := aggToArray(items.Get())
-			if err != nil {
-				return nil, fmt.Errorf("transform: aggregate_to_array: %v", err)
-			}
+			array := aggToArray(items.Get())
 
 			outMsg := message.New()
 			if tf.hasObjTrg {
-				if err := outMsg.SetValue(tf.conf.Object.TargetKey, agg); err != nil {
+				if err := outMsg.SetValue(tf.conf.Object.TargetKey, array); err != nil {
 					return nil, fmt.Errorf("transform: aggregate_to_array: %v", err)
 				}
 			} else {
-				outMsg.SetData(agg)
+				outMsg.SetData(array)
 			}
 
 			output = append(output, outMsg)
@@ -80,18 +76,15 @@ func (tf *aggregateToArray) Transform(ctx context.Context, msg *message.Message)
 		return nil, nil
 	}
 
-	agg, err := aggToArray(tf.agg.Get(key))
-	if err != nil {
-		return nil, fmt.Errorf("transform: aggregate_to_array: %v", err)
-	}
+	array := aggToArray(tf.agg.Get(key))
 
 	outMsg := message.New()
 	if tf.hasObjTrg {
-		if err := outMsg.SetValue(tf.conf.Object.TargetKey, agg); err != nil {
+		if err := outMsg.SetValue(tf.conf.Object.TargetKey, array); err != nil {
 			return nil, fmt.Errorf("transform: aggregate_to_array: %v", err)
 		}
 	} else {
-		outMsg.SetData(agg)
+		outMsg.SetData(array)
 	}
 
 	// If data cannot be added after reset, then the batch is misconfgured.