diff --git a/Makefile b/Makefile
index 29eec06..d0a3786 100644
--- a/Makefile
+++ b/Makefile
@@ -27,7 +27,7 @@ doc:
 .PHONY: test
 ## Run tests
 test:
-	@go test -coverprofile=coverage.out -race -json ./... | gotestfmt
+	@GO_TEST_TAGS=-skip go test -coverprofile=coverage.out -race -json ./... | gotestfmt
 
 .PHONY: lint
 ## Run linter
diff --git a/integration/watermill/gtag/errors.go b/integration/watermill/gtag/errors.go
new file mode 100644
index 0000000..755bb14
--- /dev/null
+++ b/integration/watermill/gtag/errors.go
@@ -0,0 +1,12 @@
+package gtag
+
+import (
+	"errors"
+)
+
+var (
+	ErrMissingEventName = errors.New("missing event name")
+	ErrContextCanceled  = errors.New("request stopped without ACK received")
+	ErrMessageNacked    = errors.New("message nacked")
+	ErrClosed           = errors.New("subscriber already closed")
+)
diff --git a/integration/watermill/gtag/subscriber.go b/integration/watermill/gtag/subscriber.go
index 181971c..2129c66 100644
--- a/integration/watermill/gtag/subscriber.go
+++ b/integration/watermill/gtag/subscriber.go
@@ -16,13 +16,6 @@ import (
 	"go.uber.org/zap"
 )
 
-var (
-	ErrMissingEventName = errors.New("missing event name")
-	ErrContextCanceled  = errors.New("request stopped without ACK received")
-	ErrMessageNacked    = errors.New("message nacked")
-	ErrClosed           = errors.New("subscriber already closed")
-)
-
 type (
 	Subscriber struct {
 		l           *zap.Logger
@@ -52,33 +45,6 @@ func SubscriberWithMiddlewares(v ...SubscriberMiddleware) SubscriberOption {
 	}
 }
 
-func SubscriberWithLogger(fields ...zap.Field) SubscriberOption {
-	return func(o *Subscriber) {
-		o.middlewares = append(o.middlewares, func(next SubscriberHandler) SubscriberHandler {
-			return func(l *zap.Logger, r *http.Request, event *gtag.Payload) error {
-				fields := append(fields, zap.String("event_name", gtag.GetDefault(event.EventName, "-").String()))
-				// if labeler, ok := keellog.LabelerFromRequest(r); ok {
-				// 	labeler.Add(fields...)
-				// }
-				return next(l.With(fields...), r, event)
-			}
-		})
-	}
-}
-
-func SubscriberWithRequireEventName() SubscriberOption {
-	return func(o *Subscriber) {
-		o.middlewares = append(o.middlewares, func(next SubscriberHandler) SubscriberHandler {
-			return func(l *zap.Logger, r *http.Request, event *gtag.Payload) error {
-				if event.EventName == nil {
-					return ErrMissingEventName
-				}
-				return next(l, r, event)
-			}
-		})
-	}
-}
-
 // ------------------------------------------------------------------------------------------------
 // ~ Constructor
 // ------------------------------------------------------------------------------------------------
@@ -137,6 +103,12 @@ func (s *Subscriber) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// validate
+	if payload.EventName.String() == "" {
+		http.Error(w, "missing event name", http.StatusBadRequest)
+		return
+	}
+
 	// compose middlewares
 	next := s.handle
 	for _, middleware := range s.middlewares {
diff --git a/integration/watermill/gtag/subscribermiddleware.go b/integration/watermill/gtag/subscribermiddleware.go
new file mode 100644
index 0000000..866840e
--- /dev/null
+++ b/integration/watermill/gtag/subscribermiddleware.go
@@ -0,0 +1,36 @@
+package gtag
+
+import (
+	"net/http"
+
+	"github.com/foomo/sesamy-go/pkg/encoding/gtag"
+	"go.uber.org/zap"
+)
+
+func SubscriberMiddlewareUserID(cookieName string) SubscriberMiddleware {
+	return func(next SubscriberHandler) SubscriberHandler {
+		return func(l *zap.Logger, r *http.Request, payload *gtag.Payload) error {
+			if cookie, err := r.Cookie(cookieName); err == nil {
+				payload.UserID = gtag.Set(cookie.Value)
+			}
+			return next(l, r, payload)
+		}
+	}
+}
+
+func SubscriberMiddlewareLogger(next SubscriberHandler) SubscriberHandler {
+	return func(l *zap.Logger, r *http.Request, payload *gtag.Payload) error {
+		l = l.With(
+			zap.String("event_name", gtag.GetDefault(payload.EventName, "-").String()),
+			zap.String("event_user_id", gtag.GetDefault(payload.UserID, "-")),
+			zap.String("event_session_id", gtag.GetDefault(payload.SessionID, "-")),
+		)
+		err := next(l, r, payload)
+		if err != nil {
+			l.Error("handled event", zap.Error(err))
+		} else {
+			l.Info("handled event")
+		}
+		return err
+	}
+}
diff --git a/integration/watermill/mpv2/errors.go b/integration/watermill/mpv2/errors.go
new file mode 100644
index 0000000..c919c4d
--- /dev/null
+++ b/integration/watermill/mpv2/errors.go
@@ -0,0 +1,14 @@
+package mpv2
+
+import (
+	"errors"
+)
+
+var (
+	ErrMissingEventName = errors.New("missing event name")
+	ErrErrorResponse    = errors.New("server responded with error status")
+	ErrPublisherClosed  = errors.New("publisher is closed")
+	ErrContextCanceled  = errors.New("request stopped without ACK received")
+	ErrMessageNacked    = errors.New("message nacked")
+	ErrClosed           = errors.New("subscriber already closed")
+)
diff --git a/integration/watermill/mpv2/publisher.go b/integration/watermill/mpv2/publisher.go
index 9979158..adfb406 100644
--- a/integration/watermill/mpv2/publisher.go
+++ b/integration/watermill/mpv2/publisher.go
@@ -12,11 +12,6 @@ import (
 	"go.uber.org/zap"
 )
 
-var (
-	ErrErrorResponse   = errors.New("server responded with error status")
-	ErrPublisherClosed = errors.New("publisher is closed")
-)
-
 type (
 	Publisher struct {
 		l                  *zap.Logger
diff --git a/integration/watermill/mpv2/subscriber.go b/integration/watermill/mpv2/subscriber.go
index 68825fc..518e6a3 100644
--- a/integration/watermill/mpv2/subscriber.go
+++ b/integration/watermill/mpv2/subscriber.go
@@ -5,7 +5,6 @@ import (
 	"encoding/json"
 	"net/http"
 	"strings"
-	"time"
 
 	"github.com/ThreeDotsLabs/watermill"
 	"github.com/ThreeDotsLabs/watermill/message"
@@ -14,13 +13,6 @@ import (
 	"go.uber.org/zap"
 )
 
-var (
-	ErrMissingEventName = errors.New("missing event name")
-	ErrContextCanceled  = errors.New("request stopped without ACK received")
-	ErrMessageNacked    = errors.New("message nacked")
-	ErrClosed           = errors.New("subscriber already closed")
-)
-
 type (
 	Subscriber struct {
 		l           *zap.Logger
@@ -50,37 +42,6 @@ func SubscriberWithMiddlewares(v ...SubscriberMiddleware) SubscriberOption {
 	}
 }
 
-func SubscriberWithLogger(fields ...zap.Field) SubscriberOption {
-	return func(o *Subscriber) {
-		o.middlewares = append(o.middlewares, func(next SubscriberHandler) SubscriberHandler {
-			return func(l *zap.Logger, r *http.Request, payload *mpv2.Payload[any]) error {
-				fields := append(fields,
-					zap.String("user_id", payload.UserID),
-					zap.String("client_id", payload.ClientID),
-					zap.Time("timestamp", time.UnixMicro(payload.TimestampMicros)),
-				)
-				// if labeler, ok := keellog.LabelerFromRequest(r); ok {
-				// 	labeler.Add(fields...)
-				// }
-				return next(l.With(fields...), r, payload)
-			}
-		})
-	}
-}
-
-// func SubscriberWithRequireEventName() SubscriberOption {
-// 	return func(o *Subscriber) {
-// 		o.middlewares = append(o.middlewares, func(next SubscriberHandler) SubscriberHandler {
-// 			return func(l *zap.Logger, r *http.Request, event *mpv2.Payload[any]) error {
-// 				if event.EventName == nil {
-// 					return ErrMissingEventName
-// 				}
-// 				return next(l, r, event)
-// 			}
-// 		})
-// 	}
-// }
-
 // ------------------------------------------------------------------------------------------------
 // ~ Constructor
 // ------------------------------------------------------------------------------------------------
@@ -111,6 +72,18 @@ func (s *Subscriber) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// validate required fields
+	if len(payload.Events) == 0 {
+		http.Error(w, "missing events", http.StatusBadRequest)
+		return
+	}
+	for _, event := range payload.Events {
+		if event.Name == "" {
+			http.Error(w, "missing event name", http.StatusBadRequest)
+			return
+		}
+	}
+
 	// compose middlewares
 	next := s.handle
 	for _, middleware := range s.middlewares {
diff --git a/integration/watermill/mpv2/subscribermiddleware.go b/integration/watermill/mpv2/subscribermiddleware.go
new file mode 100644
index 0000000..bc51b0d
--- /dev/null
+++ b/integration/watermill/mpv2/subscribermiddleware.go
@@ -0,0 +1,64 @@
+package mpv2
+
+import (
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/foomo/sesamy-go/pkg/encoding/mpv2"
+	"github.com/foomo/sesamy-go/pkg/session"
+	"go.uber.org/zap"
+)
+
+func SubscriberMiddlewareClientID(next SubscriberHandler) SubscriberHandler {
+	return func(l *zap.Logger, r *http.Request, payload *mpv2.Payload[any]) error {
+		if payload.ClientID == "" {
+			clientID, err := session.ParseGAClientID(r)
+			if err != nil {
+				return err
+			}
+			payload.ClientID = clientID
+		}
+		return next(l, r, payload)
+	}
+}
+
+func SubscriberMiddlewareUserID(cookieName string) SubscriberMiddleware {
+	return func(next SubscriberHandler) SubscriberHandler {
+		return func(l *zap.Logger, r *http.Request, payload *mpv2.Payload[any]) error {
+			if cookie, err := r.Cookie(cookieName); err == nil {
+				payload.UserID = cookie.Value
+			}
+			return next(l, r, payload)
+		}
+	}
+}
+
+func SubscriberMiddlewareTimestamp(next SubscriberHandler) SubscriberHandler {
+	return func(l *zap.Logger, r *http.Request, payload *mpv2.Payload[any]) error {
+		payload.TimestampMicros = time.Now().UnixMicro()
+		return next(l, r, payload)
+	}
+}
+
+func SubscriberMiddlewareLogger(next SubscriberHandler) SubscriberHandler {
+	return func(l *zap.Logger, r *http.Request, payload *mpv2.Payload[any]) error {
+		eventNames := make([]string, len(payload.Events))
+		for i, event := range payload.Events {
+			eventNames[i] = event.Name.String()
+		}
+
+		l = l.With(
+			zap.String("event_names", strings.Join(eventNames, ",")),
+			zap.String("event_user_id", payload.UserID),
+		)
+
+		err := next(l, r, payload)
+		if err != nil {
+			l.Error("handled event", zap.Error(err))
+		} else {
+			l.Info("handled event")
+		}
+		return err
+	}
+}
diff --git a/pkg/session/ga.go b/pkg/session/ga.go
new file mode 100644
index 0000000..bf51b7f
--- /dev/null
+++ b/pkg/session/ga.go
@@ -0,0 +1,40 @@
+package session
+
+import (
+	"net/http"
+	"strings"
+
+	"github.com/pkg/errors"
+)
+
+func ParseGAClientID(r *http.Request) (string, error) {
+	cookie, err := r.Cookie("_ga")
+	if err != nil {
+		return "", errors.Wrap(err, "failed to retrieve _ga cookie")
+	}
+
+	parts := strings.Split(cookie.Value, ".")
+
+	// validate
+	if !strings.HasPrefix(cookie.Value, "GA1.1") || len(parts) < 4 {
+		return "", errors.New("invalid _ga cookie value")
+	}
+
+	return parts[2] + "." + parts[3], nil
+}
+
+func ParseGASessionID(r *http.Request, id string) (string, error) {
+	cookie, err := r.Cookie("_ga_" + id)
+	if err != nil {
+		return "", errors.Wrap(err, "failed to retrieve _ga cookie")
+	}
+
+	parts := strings.Split(cookie.Value, ".")
+
+	// validate
+	if !strings.HasPrefix(cookie.Value, "GS1.1") || len(parts) < 3 {
+		return "", errors.New("invalid _ga cookie value")
+	}
+
+	return parts[2], nil
+}
diff --git a/pkg/session/gtm.go b/pkg/session/gtm.go
new file mode 100644
index 0000000..5ef9507
--- /dev/null
+++ b/pkg/session/gtm.go
@@ -0,0 +1,15 @@
+package session
+
+import (
+	"net/http"
+)
+
+func IsGTMDebug(r *http.Request) bool {
+	_, err := r.Cookie("gtm_debug")
+	return err == nil
+}
+
+func IsGTMPreview(r *http.Request) bool {
+	_, err := r.Cookie("gtm_preview")
+	return err == nil
+}