feat(session): add DisplayName field to CreateRequest

session/service.go

@@ -48,6 +48,9 @@ type CreateRequest struct {
 	SessionID string
 	// State is the initial state of the session.
 	State map[string]any
+	// DisplayName is a human-readable name for the session.
+	// Optional: only used by backends that support it (e.g. Vertex AI).
+	DisplayName string
 }
 
 // CreateResponse represents a response for newly created session.

session/session_test/service_suite.go

@@ -131,6 +131,23 @@ func RunServiceTests(t *testing.T, opts SuiteOptions, setup func(t *testing.T) s
 			}
 		})
 
+		t.Run("with_display_name", func(t *testing.T) {
+			s := setup(t)
+			req := &session.CreateRequest{
+				AppName:     testAppName,
+				UserID:      "testUserID",
+				DisplayName: "My Chat Session",
+			}
+
+			got, err := s.Create(t.Context(), req)
+			if err != nil {
+				t.Fatalf("Create() with DisplayName error = %v", err)
+			}
+			if got.Session.ID() == "" {
+				t.Errorf("Expected generated SessionID, got empty")
+			}
+		})
+
 		t.Run("when_already_exists,_it_fails", func(t *testing.T) {
 			s := setup(t)
 			req := &session.CreateRequest{

session/vertexai/vertexai_client.go

@@ -64,7 +64,8 @@ func (c *vertexAiClient) Close() error {
 
 func (c *vertexAiClient) createSession(ctx context.Context, req *session.CreateRequest) (*localSession, error) {
 	pbSession := &aiplatformpb.Session{
-		UserId: req.UserID,
+		UserId:      req.UserID,
+		DisplayName: req.DisplayName,
 	}
 	// Convert and set the initial state if provided
 	if len(req.State) > 0 {

session/vertexai/vertexai_test.go

@@ -16,8 +16,53 @@ package vertexai
 
 import (
 	"testing"
+
+	aiplatformpb "cloud.google.com/go/aiplatform/apiv1beta1/aiplatformpb"
+	"google.golang.org/adk/session"
 )
 
+func TestCreateSessionProto_DisplayName(t *testing.T) {
+	tests := []struct {
+		name        string
+		displayName string
+		wantProto   string
+	}{
+		{
+			name:        "display name is set on proto",
+			displayName: "My Chat",
+			wantProto:   "My Chat",
+		},
+		{
+			name:        "empty display name results in empty proto field",
+			displayName: "",
+			wantProto:   "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			req := &session.CreateRequest{
+				AppName:     "testApp",
+				UserID:      "user-1",
+				DisplayName: tt.displayName,
+			}
+
+			// Replicate the proto construction from createSession.
+			pbSession := &aiplatformpb.Session{
+				UserId:      req.UserID,
+				DisplayName: req.DisplayName,
+			}
+
+			if pbSession.DisplayName != tt.wantProto {
+				t.Errorf("DisplayName = %q, want %q", pbSession.DisplayName, tt.wantProto)
+			}
+			if pbSession.UserId != req.UserID {
+				t.Errorf("UserId = %q, want %q", pbSession.UserId, req.UserID)
+			}
+		})
+	}
+}
+
 func TestGetReasoningEngineID(t *testing.T) {
 	tests := []struct {
 		name             string