diff --git a/pkg/common/helpers.go b/pkg/common/helpers.go
index fb03580..cb15945 100644
--- a/pkg/common/helpers.go
+++ b/pkg/common/helpers.go
@@ -11,6 +11,8 @@ import (
 	"time"
 
 	"github.com/go-playground/validator"
+	"github.com/truvami/decoder/internal/logger"
+	"go.uber.org/zap"
 )
 
 func HexStringToBytes(hexString string) ([]byte, error) {
@@ -154,21 +156,28 @@ func Decode(payloadHex *string, config *PayloadConfig) (any, error) {
 	errs := []error{}
 
 	if len(config.Tags) != 0 {
-		var index uint8 = 3
-		var payloadLength = uint8(len(payloadBytes))
-		for index+2 < payloadLength {
-			var found = false
+		var index = 3
+		var payloadLength = len(payloadBytes)
+		for index < payloadLength {
+			if payloadLength-index < 2 {
+				return nil, fmt.Errorf("incomplete TLV header at offset %d: need 2 bytes but only %d remain", index, payloadLength-index)
+			}
+
 			var tag = payloadBytes[index]
-			index++
-			var length = payloadBytes[index]
-			index++
+			var length = int(payloadBytes[index+1])
+			index += 2
 
+			if index+length > payloadLength {
+				return nil, fmt.Errorf("TLV tag 0x%02x at offset %d declares length %d, but only %d bytes remain", tag, index-2, length, payloadLength-index)
+			}
+
+			var found bool
 			for _, tagConfig := range config.Tags {
 				if tagConfig.Tag == tag {
 					found = true
 					config.Features = append(config.Features, tagConfig.Feature)
 
-					value, err := extractFieldValue(payloadBytes, int(index), int(length), false, tagConfig.Hex)
+					value, err := extractFieldValue(payloadBytes, index, length, false, tagConfig.Hex)
 					if err != nil {
 						return nil, err
 					}
@@ -198,11 +207,14 @@ func Decode(payloadHex *string, config *PayloadConfig) (any, error) {
 					}
 				}
 			}
-			if found {
-				index += length
-			} else {
-				return nil, fmt.Errorf("unknown tag %x", tag)
+			if !found {
+				tagHex := fmt.Sprintf("0x%02x", tag)
+				unknownTLVTagsTotal.WithLabelValues(tagHex).Inc()
+				if logger.Logger != nil {
+					logger.Logger.Warn("skipping unknown tag", zap.String("tag", tagHex), zap.Int("length", length))
+				}
 			}
+			index += length
 		}
 
 		return targetValue.Interface(), errors.Join(errs...)
diff --git a/pkg/common/helpers_test.go b/pkg/common/helpers_test.go
index 73aa45e..fd086be 100644
--- a/pkg/common/helpers_test.go
+++ b/pkg/common/helpers_test.go
@@ -125,10 +125,11 @@ func TestDecode(t *testing.T) {
 			payload: "ffffff0000",
 			config:  tagConfig,
 			expected: Port2Payload{
-				Time:   nil,
+				Time:   Uint32Ptr(0),
 				Power:  nil,
 				Sensor: nil,
 			},
+			expectedErr: "validation failed for Time",
 		},
 		{
 			payload: "ffffff000400000000",
@@ -141,16 +142,19 @@ func TestDecode(t *testing.T) {
 			expectedErr: "validation failed for Time",
 		},
 		{
-			payload:     "ffffff040100",
-			config:      tagConfig,
-			expected:    nil,
-			expectedErr: "unknown tag 4",
+			payload: "ffffff040100",
+			config:  tagConfig,
+			expected: Port2Payload{
+				Time:   nil,
+				Power:  nil,
+				Sensor: nil,
+			},
 		},
 		{
 			payload:     "ffffff010200",
 			config:      tagConfig,
 			expected:    nil,
-			expectedErr: "field out of bounds",
+			expectedErr: "TLV tag",
 		},
 		{
 			payload:     "ffffff030100",
@@ -163,8 +167,15 @@ func TestDecode(t *testing.T) {
 	for _, test := range tests {
 		t.Run(test.payload, func(t *testing.T) {
 			decodedData, err := Decode(StringPtr(test.payload), &test.config)
-			if err != nil && !strings.Contains(err.Error(), test.expectedErr) {
-				t.Fatalf("expected %s received %s", test.expectedErr, err)
+			if test.expectedErr != "" {
+				if err == nil {
+					t.Fatalf("expected error containing %q but got nil", test.expectedErr)
+				}
+				if !strings.Contains(err.Error(), test.expectedErr) {
+					t.Fatalf("expected error containing %q received %s", test.expectedErr, err)
+				}
+			} else if err != nil {
+				t.Fatalf("unexpected error: %s", err)
 			}
 			if !reflect.DeepEqual(decodedData, test.expected) {
 				t.Fatalf("expected: %+v received: %+v", test.expected, decodedData)
@@ -239,8 +250,15 @@ func TestExtractFieldValue(t *testing.T) {
 	for _, test := range tests {
 		t.Run(fmt.Sprintf("%v_%v_%v", test.payload, test.start, test.length), func(t *testing.T) {
 			result, err := extractFieldValue(test.payload, test.start, test.length, test.optional, test.hexadecimal)
-			if err != nil && err.Error() != test.expectedErr {
-				t.Fatalf("expected: %s received: %s", test.expectedErr, err.Error())
+			if test.expectedErr != "" {
+				if err == nil {
+					t.Fatalf("expected error %q but got nil", test.expectedErr)
+				}
+				if err.Error() != test.expectedErr {
+					t.Fatalf("expected: %s received: %s", test.expectedErr, err.Error())
+				}
+			} else if err != nil {
+				t.Fatalf("unexpected error: %s", err)
 			}
 			if !reflect.DeepEqual(result, test.expected) {
 				t.Fatalf("expected: %v received: %v", test.expected, result)
@@ -373,8 +391,15 @@ func TestConvertFieldValue(t *testing.T) {
 	for _, test := range tests {
 		t.Run(fmt.Sprintf("%v_%v", test.value, test.fieldType), func(t *testing.T) {
 			result, err := convertFieldValue(test.value, test.fieldType, nil)
-			if err != nil && err.Error() != test.expectedErr {
-				t.Fatalf("expected: %s received: %s", test.expectedErr, err.Error())
+			if test.expectedErr != "" {
+				if err == nil {
+					t.Fatalf("expected error %q but got nil", test.expectedErr)
+				}
+				if err.Error() != test.expectedErr {
+					t.Fatalf("expected: %s received: %s", test.expectedErr, err.Error())
+				}
+			} else if err != nil {
+				t.Fatalf("unexpected error: %s", err)
 			}
 			if !reflect.DeepEqual(result, test.expected) {
 				t.Fatalf("expected: %v received: %v", test.expected, result)
@@ -450,8 +475,15 @@ func TestInsertFieldBytes(t *testing.T) {
 
 	for _, test := range tests {
 		set, bytes, err := insertFieldBytes(test.value, test.length, test.transform)
-		if err != nil && err.Error() != test.expectedErr {
-			t.Fatalf("expected: %s received: %s", test.expectedErr, err.Error())
+		if test.expectedErr != "" {
+			if err == nil {
+				t.Fatalf("expected error %q but got nil", test.expectedErr)
+			}
+			if err.Error() != test.expectedErr {
+				t.Fatalf("expected: %s received: %s", test.expectedErr, err.Error())
+			}
+		} else if err != nil {
+			t.Fatalf("unexpected error: %s", err)
 		}
 		if !set && err == nil {
 			t.Fatalf("expected set to be true when error is nil")
diff --git a/pkg/common/metrics.go b/pkg/common/metrics.go
new file mode 100644
index 0000000..fee4425
--- /dev/null
+++ b/pkg/common/metrics.go
@@ -0,0 +1,13 @@
+package common
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+var (
+	unknownTLVTagsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
+		Name: "truvami_common_unknown_tlv_tags_total",
+		Help: "The total number of unknown TLV tags encountered during decoding",
+	}, []string{"tag"})
+)
diff --git a/pkg/decoder/tagxl/v1/decoder_test.go b/pkg/decoder/tagxl/v1/decoder_test.go
index e659531..e3f8750 100644
--- a/pkg/decoder/tagxl/v1/decoder_test.go
+++ b/pkg/decoder/tagxl/v1/decoder_test.go
@@ -117,10 +117,17 @@ func TestDecode(t *testing.T) {
 			expectedErr: "port not supported: port 151 tag ff",
 		},
 		{
-			port:        151,
-			payload:     "4c0501ff020000",
-			expected:    Port151Payload{},
-			expectedErr: "unknown tag ff",
+			port:     151,
+			payload:  "4c0501ff020000",
+			expected: Port151Payload{},
+		},
+		{
+			port:    151,
+			payload: "4c0d0345020a92ff03aabbcc4e0107",
+			expected: Port151Payload{
+				Battery:  helpers.Float32Ptr(2.706),
+				DataRate: helpers.DataRatePtr(decoder.DataRateTagXLADR),
+			},
 		},
 		{
 			port:    151,