diff --git a/server/agentengine/internal/helper/encode.go b/server/agentengine/internal/helper/encode.go
index 8e9eb905d..6dd5f0a0f 100644
--- a/server/agentengine/internal/helper/encode.go
+++ b/server/agentengine/internal/helper/encode.go
@@ -15,6 +15,7 @@
 package helper
 
 import (
+	"encoding/base64"
 	"fmt"
 	"log"
 	"reflect"
@@ -120,6 +121,9 @@ func convertSnake(path, indent string, o any) (any, error) {
 		}
 		return m, nil
 	case reflect.Slice:
+		if v.Type().Elem().Kind() == reflect.Uint8 {
+			return base64.StdEncoding.EncodeToString(v.Bytes()), nil
+		}
 		res := []any{}
 		for i := 0; i < v.Len(); i++ {
 			elem, err := convertSnake(path+".[]", indent+"    ", v.Index(i).Interface())
diff --git a/server/agentengine/internal/helper/encode_test.go b/server/agentengine/internal/helper/encode_test.go
index d84bfe62b..bab4470fa 100644
--- a/server/agentengine/internal/helper/encode_test.go
+++ b/server/agentengine/internal/helper/encode_test.go
@@ -163,6 +163,62 @@ func TestEventLogProbs(t *testing.T) {
 	}
 }
 
+func TestByteSlice(t *testing.T) {
+	event := session.Event{
+		ID: "1",
+		LLMResponse: model.LLMResponse{
+			Content: &genai.Content{
+				Parts: []*genai.Part{
+					{
+						Text:             "hi",
+						ThoughtSignature: []byte{0xDE, 0xAD, 0xBE, 0xEF},
+					},
+				},
+			},
+		},
+	}
+	o, err := convertSnake("", "", event)
+	if err != nil {
+		t.Fatalf("convertSnake() failed: %v", err)
+	}
+	m, ok := o.(map[string]any)
+	if !ok {
+		t.Fatalf("o is not a map: %T", o)
+	}
+	content, ok := m["content"].(map[string]any)
+	if !ok {
+		t.Fatalf("content is not a map: %T", m["content"])
+	}
+	parts, ok := content["parts"].([]any)
+	if !ok || len(parts) != 1 {
+		t.Fatalf("parts is not a 1-element slice: %v", content["parts"])
+	}
+	part, ok := parts[0].(map[string]any)
+	if !ok {
+		t.Fatalf("part is not a map: %T", parts[0])
+	}
+	want := "3q2+7w=="
+	if got, _ := part["thought_signature"].(string); got != want {
+		t.Errorf("thought_signature = %q, want %q", got, want)
+	}
+}
+
+func TestByteSliceOmitEmpty(t *testing.T) {
+	type A struct {
+		Sig []byte `json:"sig,omitempty"`
+	}
+	got, err := convertSnake("", "", A{})
+	if err != nil {
+		t.Fatalf("convertSnake() failed: %v", err)
+	}
+	m, ok := got.(map[string]any)
+	if !ok {
+		t.Fatalf("got is not a map: %T", got)
+	}
+	if _, present := m["sig"]; present {
+		t.Errorf("sig should be omitted for an empty []byte, got: %v", m["sig"])
+	}
+}
 func TestEmbedded(t *testing.T) {
 	type A struct {
 		anInteger int