diff --git a/cmd/karma/alerts.go b/cmd/karma/alerts.go
index 64bac4add..0de49c666 100644
--- a/cmd/karma/alerts.go
+++ b/cmd/karma/alerts.go
@@ -52,7 +52,7 @@ func countersToLabelStats(counters map[string]map[string]int) models.LabelNameSt
 			nameStats.Values[i].Percent = int(math.Floor((float64(value.Hits) / float64(nameStats.Hits)) * 100.0))
 			totalPercent += nameStats.Values[i].Percent
 		}
-		sort.Sort(nameStats.Values)
+		slices.SortFunc(nameStats.Values, models.CompareLabelValueStats)
 		for totalPercent < 100 {
 			for i := range nameStats.Values {
 				nameStats.Values[i].Percent++
@@ -72,7 +72,7 @@ func countersToLabelStats(counters map[string]map[string]int) models.LabelNameSt
 		data = append(data, nameStats)
 	}
 
-	sort.Sort(data)
+	slices.SortFunc(data, models.CompareLabelNameStats)
 
 	return data
 }
@@ -272,7 +272,7 @@ func autoGridLabel(dedupedAlerts []models.AlertGroup) string {
 	var alertsCount int
 	labelToAlertCount := map[models.UniqueString]map[string]int{}
 	for _, ag := range dedupedAlerts {
-		alertsCount += ag.Alerts.Len()
+		alertsCount += len(ag.Alerts)
 		for _, alert := range ag.Alerts {
 			for _, l := range alert.Labels {
 				if _, ok := labelToAlertCount[l.Name]; !ok {
@@ -375,7 +375,7 @@ func filterAlerts(dedupedAlerts []models.AlertGroup, fl []filters.FilterT) (filt
 			agCopy.Alerts = append(agCopy.Alerts, alert)
 			agCopy.StateCount[alert.State.Value()]++
 		}
-		if agCopy.Alerts.Len() > 0 {
+		if len(agCopy.Alerts) > 0 {
 			filteredAlerts = append(filteredAlerts, agCopy)
 		}
 	}
diff --git a/cmd/karma/views.go b/cmd/karma/views.go
index 405bc9630..c907677bb 100644
--- a/cmd/karma/views.go
+++ b/cmd/karma/views.go
@@ -426,7 +426,7 @@ func alerts(w http.ResponseWriter, r *http.Request) {
 						}
 					}
 				}
-				sort.Sort(ag.Alerts)
+				slices.SortFunc(ag.Alerts, models.CompareAlerts)
 				ag.LatestStartsAt = ag.FindLatestStartsAt()
 				ag.Hash = ag.ContentFingerprint()
 				apiAG := models.APIAlertGroup{AlertGroup: *ag, TotalAlerts: len(ag.Alerts)}
@@ -584,12 +584,13 @@ func autocomplete(w http.ResponseWriter, r *http.Request) {
 
 	dedupedAutocomplete := alertmanager.DedupAutocomplete()
 
+	lowerTerm := strings.ToLower(term)
 	for _, hint := range dedupedAutocomplete {
-		if strings.HasPrefix(strings.ToLower(hint.Value.Value()), strings.ToLower(term)) {
+		if strings.HasPrefix(strings.ToLower(hint.Value.Value()), lowerTerm) {
 			acData = append(acData, hint.Value.Value())
 		} else {
 			for _, token := range hint.Tokens {
-				if strings.HasPrefix(strings.ToLower(token.Value()), strings.ToLower(term)) {
+				if strings.HasPrefix(strings.ToLower(token.Value()), lowerTerm) {
 					acData = append(acData, hint.Value.Value())
 				}
 			}
@@ -789,7 +790,7 @@ func alertList(w http.ResponseWriter, r *http.Request) {
 		for k, v := range labels {
 			alert = alert.Set(k, v)
 		}
-		sort.Sort(alert)
+		slices.SortFunc(alert, models.CompareLabels)
 		al.Alerts = append(al.Alerts, alert)
 	}
 	sortSliceOfLabels(al.Alerts, sortKeys, "alertname")
diff --git a/internal/alertmanager/dedup.go b/internal/alertmanager/dedup.go
index 52cf43eac..9d474597d 100644
--- a/internal/alertmanager/dedup.go
+++ b/internal/alertmanager/dedup.go
@@ -88,14 +88,14 @@ func DedupAlerts() []models.AlertGroup {
 			continue
 		}
 		ag := agList[0]
-		ag.Labels = transform.StripLables(
+		ag.Labels = transform.StripLabels(
 			config.Config.Labels.Keep, config.Config.Labels.Strip,
 			config.Config.Labels.CompiledKeepRegex, config.Config.Labels.CompiledStripRegex,
 			ag.Labels)
 		ag.Alerts = make(models.AlertList, 0, len(alerts))
 		for _, alert := range alerts {
 			// strip labels and annotations user doesn't want to see in the UI
-			alert.Labels = transform.StripLables(
+			alert.Labels = transform.StripLabels(
 				config.Config.Labels.Keep, config.Config.Labels.Strip,
 				config.Config.Labels.CompiledKeepRegex, config.Config.Labels.CompiledStripRegex,
 				alert.Labels)
diff --git a/internal/alertmanager/models.go b/internal/alertmanager/models.go
index 5db86672a..6d1c7f705 100644
--- a/internal/alertmanager/models.go
+++ b/internal/alertmanager/models.go
@@ -5,6 +5,7 @@ import (
 	"maps"
 	"net/http"
 	"net/url"
+	"slices"
 	"sort"
 	"sync"
 	"time"
@@ -310,7 +311,7 @@ func (am *Alertmanager) pullAlerts(version string) error {
 			autocompleteMap[hint.Value] = &hint
 		}
 
-		sort.Sort(&alerts)
+		slices.SortFunc(alerts, models.CompareAlerts)
 		ag.Alerts = alerts
 
 		// Hash is a checksum of all alerts, used to tell when any alert in the group changed
diff --git a/internal/alertmanager/models_test.go b/internal/alertmanager/models_test.go
index 8b8583dba..922c2ae23 100644
--- a/internal/alertmanager/models_test.go
+++ b/internal/alertmanager/models_test.go
@@ -1,6 +1,7 @@
 package alertmanager
 
 import (
+	"errors"
 	"fmt"
 	"testing"
 	"time"
@@ -9,6 +10,7 @@ import (
 
 	"github.com/prymitive/karma/internal/config"
 	"github.com/prymitive/karma/internal/mapper/v017/models"
+	internalModels "github.com/prymitive/karma/internal/models"
 
 	"github.com/rs/zerolog"
 )
@@ -243,6 +245,141 @@ func TestAlertmanagerPullSilencesWithInvalidVersion(t *testing.T) {
 	}
 }
 
+func TestProbeVersionHTTPError(t *testing.T) {
+	// verifies that probeVersion returns empty string when the metrics endpoint is unreachable
+	zerolog.SetGlobalLevel(zerolog.PanicLevel)
+	defer zerolog.SetGlobalLevel(zerolog.ErrorLevel)
+
+	uri := "http://probe-http-error.localhost"
+	httpmock.RegisterResponder("GET", uri+"/metrics",
+		httpmock.NewErrorResponder(errors.New("connection refused")))
+
+	am, err := NewAlertmanager("cluster", "probe-http-err", uri)
+	if err != nil {
+		t.Fatalf("NewAlertmanager failed: %s", err)
+	}
+	version := am.probeVersion()
+	if version != "" {
+		t.Errorf("probeVersion() returned %q, expected empty string on HTTP error", version)
+	}
+}
+
+func TestProbeVersionInvalidMetrics(t *testing.T) {
+	// verifies that probeVersion returns empty string when metrics response contains no version info
+	zerolog.SetGlobalLevel(zerolog.PanicLevel)
+	defer zerolog.SetGlobalLevel(zerolog.ErrorLevel)
+
+	uri := "http://probe-invalid-metrics.localhost"
+	httpmock.RegisterResponder("GET", uri+"/metrics",
+		httpmock.NewStringResponder(200, "some_random_metric 1\n"))
+
+	am, err := NewAlertmanager("cluster", "probe-invalid", uri)
+	if err != nil {
+		t.Fatalf("NewAlertmanager failed: %s", err)
+	}
+	version := am.probeVersion()
+	if version != "" {
+		t.Errorf("probeVersion() returned %q, expected empty string on invalid metrics", version)
+	}
+}
+
+func TestIsHealthCheckAlertAllMatch(t *testing.T) {
+	// verifies that an alert matching all healthcheck filters is identified as a healthcheck
+	am, err := NewAlertmanager("cluster", "hc-test", "http://localhost",
+		WithHealthchecks(map[string][]string{
+			"prom1": {"alertname=Watchdog"},
+		}),
+	)
+	if err != nil {
+		t.Fatalf("NewAlertmanager failed: %s", err)
+	}
+
+	alert := &internalModels.Alert{
+		Labels: internalModels.Labels{
+			{Name: internalModels.NewUniqueString("alertname"), Value: internalModels.NewUniqueString("Watchdog")},
+		},
+	}
+	name, hc := am.IsHealthCheckAlert(alert)
+	if name != "prom1" {
+		t.Errorf("IsHealthCheckAlert() returned name=%q, expected %q", name, "prom1")
+	}
+	if hc == nil {
+		t.Error("IsHealthCheckAlert() returned nil HealthCheck for matching alert")
+	}
+}
+
+func TestIsHealthCheckAlertPartialMatch(t *testing.T) {
+	// verifies that an alert matching only some healthcheck filters is NOT identified as a healthcheck
+	am, err := NewAlertmanager("cluster", "hc-test-partial", "http://localhost",
+		WithHealthchecks(map[string][]string{
+			"prom1": {"alertname=Watchdog", "severity=critical"},
+		}),
+	)
+	if err != nil {
+		t.Fatalf("NewAlertmanager failed: %s", err)
+	}
+
+	alert := &internalModels.Alert{
+		Labels: internalModels.Labels{
+			{Name: internalModels.NewUniqueString("alertname"), Value: internalModels.NewUniqueString("Watchdog")},
+			{Name: internalModels.NewUniqueString("severity"), Value: internalModels.NewUniqueString("warning")},
+		},
+	}
+	name, hc := am.IsHealthCheckAlert(alert)
+	if name != "" {
+		t.Errorf("IsHealthCheckAlert() returned name=%q, expected empty string for partial match", name)
+	}
+	if hc != nil {
+		t.Error("IsHealthCheckAlert() returned non-nil HealthCheck for partial match")
+	}
+}
+
+func TestIsHealthCheckAlertNoMatch(t *testing.T) {
+	// verifies that an alert not matching any healthcheck filters returns empty result
+	am, err := NewAlertmanager("cluster", "hc-test-none", "http://localhost",
+		WithHealthchecks(map[string][]string{
+			"prom1": {"alertname=Watchdog"},
+		}),
+	)
+	if err != nil {
+		t.Fatalf("NewAlertmanager failed: %s", err)
+	}
+
+	alert := &internalModels.Alert{
+		Labels: internalModels.Labels{
+			{Name: internalModels.NewUniqueString("alertname"), Value: internalModels.NewUniqueString("DiskFull")},
+		},
+	}
+	name, hc := am.IsHealthCheckAlert(alert)
+	if name != "" {
+		t.Errorf("IsHealthCheckAlert() returned name=%q, expected empty string for non-matching alert", name)
+	}
+	if hc != nil {
+		t.Error("IsHealthCheckAlert() returned non-nil HealthCheck for non-matching alert")
+	}
+}
+
+func TestIsHealthCheckAlertNoHealthchecks(t *testing.T) {
+	// verifies that an alertmanager with no healthchecks returns empty result
+	am, err := NewAlertmanager("cluster", "hc-test-empty", "http://localhost")
+	if err != nil {
+		t.Fatalf("NewAlertmanager failed: %s", err)
+	}
+
+	alert := &internalModels.Alert{
+		Labels: internalModels.Labels{
+			{Name: internalModels.NewUniqueString("alertname"), Value: internalModels.NewUniqueString("Watchdog")},
+		},
+	}
+	name, hc := am.IsHealthCheckAlert(alert)
+	if name != "" {
+		t.Errorf("IsHealthCheckAlert() returned name=%q, expected empty string", name)
+	}
+	if hc != nil {
+		t.Error("IsHealthCheckAlert() returned non-nil HealthCheck")
+	}
+}
+
 func TestExpiredSilences(t *testing.T) {
 	config.Config.Silences.Expired = time.Minute * 10
 
diff --git a/internal/alertmanager/upstream_test.go b/internal/alertmanager/upstream_test.go
index 718634737..ec6a07c75 100644
--- a/internal/alertmanager/upstream_test.go
+++ b/internal/alertmanager/upstream_test.go
@@ -114,6 +114,149 @@ var testCases = []testCase{
 	},
 }
 
+func saveUpstreams() map[string]*Alertmanager {
+	saved := make(map[string]*Alertmanager, len(upstreams))
+	for k, v := range upstreams {
+		saved[k] = v
+	}
+	return saved
+}
+
+func restoreUpstreams(saved map[string]*Alertmanager) {
+	upstreams = saved
+}
+
+func TestUnregisterAll(t *testing.T) {
+	// verifies that UnregisterAll removes all registered instances
+	saved := saveUpstreams()
+	defer restoreUpstreams(saved)
+
+	am, err := NewAlertmanager("cluster", "unreg-test", "http://localhost")
+	if err != nil {
+		t.Fatalf("NewAlertmanager failed: %s", err)
+	}
+	_ = RegisterAlertmanager(am)
+	UnregisterAll()
+	ams := GetAlertmanagers()
+	if len(ams) != 0 {
+		t.Errorf("Expected 0 alertmanagers after UnregisterAll, got %d", len(ams))
+	}
+}
+
+func TestRegisterAlertmanagerDuplicate(t *testing.T) {
+	// verifies that registering the same name twice returns an error
+	saved := saveUpstreams()
+	defer restoreUpstreams(saved)
+	UnregisterAll()
+
+	am, err := NewAlertmanager("cluster", "dup-test", "http://localhost")
+	if err != nil {
+		t.Fatalf("NewAlertmanager failed: %s", err)
+	}
+	if regErr := RegisterAlertmanager(am); regErr != nil {
+		t.Fatalf("First RegisterAlertmanager failed: %s", regErr)
+	}
+
+	am2, err := NewAlertmanager("cluster", "dup-test", "http://localhost:9094")
+	if err != nil {
+		t.Fatalf("NewAlertmanager failed: %s", err)
+	}
+	if err := RegisterAlertmanager(am2); err == nil {
+		t.Error("Second RegisterAlertmanager with same name should have returned an error")
+	}
+}
+
+func TestGetAlertmanagerByName(t *testing.T) {
+	saved := saveUpstreams()
+	defer restoreUpstreams(saved)
+	UnregisterAll()
+
+	am, err := NewAlertmanager("cluster", "lookup-test", "http://localhost")
+	if err != nil {
+		t.Fatalf("NewAlertmanager failed: %s", err)
+	}
+	_ = RegisterAlertmanager(am)
+
+	// verifies that a registered instance is found by name
+	found := GetAlertmanagerByName("lookup-test")
+	if found == nil {
+		t.Error("GetAlertmanagerByName returned nil for registered instance")
+	}
+	if found != nil && found.Name != "lookup-test" {
+		t.Errorf("GetAlertmanagerByName returned wrong instance: %s", found.Name)
+	}
+
+	// verifies that a non-existent name returns nil
+	notFound := GetAlertmanagerByName("does-not-exist")
+	if notFound != nil {
+		t.Errorf("GetAlertmanagerByName returned non-nil for unregistered name: %s", notFound.Name)
+	}
+}
+
+func TestWithHealthchecksVisible(t *testing.T) {
+	// verifies that WithHealthchecksVisible sets the healthchecksVisible field
+	am, err := NewAlertmanager("cluster", "hcv-test", "http://localhost",
+		WithHealthchecksVisible(true),
+	)
+	if err != nil {
+		t.Fatalf("NewAlertmanager failed: %s", err)
+	}
+	if !am.healthchecksVisible {
+		t.Error("Expected healthchecksVisible to be true")
+	}
+}
+
+func TestIsHealthy(t *testing.T) {
+	// verifies that a fresh alertmanager with no errors is healthy
+	am, err := NewAlertmanager("cluster", "healthy-test", "http://localhost")
+	if err != nil {
+		t.Fatalf("NewAlertmanager failed: %s", err)
+	}
+	if !am.IsHealthy() {
+		t.Error("Expected fresh alertmanager to be healthy")
+	}
+
+	// verifies that setting lastError makes it unhealthy
+	am.lock.Lock()
+	am.lastError = "something went wrong"
+	am.lock.Unlock()
+	if am.IsHealthy() {
+		t.Error("Expected alertmanager with lastError to be unhealthy")
+	}
+}
+
+func TestClusterMemberNames(t *testing.T) {
+	saved := saveUpstreams()
+	defer restoreUpstreams(saved)
+	UnregisterAll()
+
+	// register three alertmanagers: two in same cluster, one different
+	am1, _ := NewAlertmanager("prod", "am-1", "http://localhost:9091")
+	am2, _ := NewAlertmanager("prod", "am-2", "http://localhost:9092")
+	am3, _ := NewAlertmanager("staging", "am-3", "http://localhost:9093")
+	_ = RegisterAlertmanager(am1)
+	_ = RegisterAlertmanager(am2)
+	_ = RegisterAlertmanager(am3)
+
+	// verifies that am1 sees itself and am2 as cluster members, but not am3
+	members := am1.ClusterMemberNames()
+	if len(members) != 2 {
+		t.Errorf("Expected 2 cluster members, got %d: %v", len(members), members)
+	}
+	if members[0] != "am-1" || members[1] != "am-2" {
+		t.Errorf("Expected [am-1 am-2], got %v", members)
+	}
+
+	// verifies that am3 only sees itself
+	members3 := am3.ClusterMemberNames()
+	if len(members3) != 1 {
+		t.Errorf("Expected 1 cluster member for staging, got %d: %v", len(members3), members3)
+	}
+	if members3[0] != "am-3" {
+		t.Errorf("Expected [am-3], got %v", members3)
+	}
+}
+
 func TestOptions(t *testing.T) {
 	for _, tc := range testCases {
 		var httpTransport http.RoundTripper
diff --git a/internal/config/config_test.go b/internal/config/config_test.go
index 5a6756a51..15ec08f10 100644
--- a/internal/config/config_test.go
+++ b/internal/config/config_test.go
@@ -310,9 +310,20 @@ func TestUrlSecretTest(t *testing.T) {
 	}
 }
 
-// FIXME check logged values
 func TestLogValues(_ *testing.T) {
 	_, _ = mockConfigRead()
+	// add servers and auth users to exercise sanitization branches in LogValues
+	Config.Alertmanager.Servers = append(Config.Alertmanager.Servers, AlertmanagerConfig{
+		Cluster:     "cluster1",
+		Name:        "am1",
+		URI:         "http://user:pass@localhost:9093",
+		ExternalURI: "http://user:pass@am.example.com",
+		Headers:     map[string]string{"Authorization": "Bearer secret"},
+	})
+	Config.Authentication.BasicAuth.Users = append(Config.Authentication.BasicAuth.Users, AuthenticationUser{
+		Username: "admin",
+		Password: "secret",
+	})
 	Config.LogValues()
 }
 
diff --git a/internal/filters/matcher_test.go b/internal/filters/matcher_test.go
index 4abdbfa27..d9ee5cd89 100644
--- a/internal/filters/matcher_test.go
+++ b/internal/filters/matcher_test.go
@@ -132,6 +132,58 @@ func TestNegativeRegexpMatcher(t *testing.T) {
 	}
 }
 
+func TestRegexpMatcherWithStringValB(t *testing.T) {
+	tests := []matchTest{
+		// verifies that passing a raw string pattern (not pre-compiled) compiles and matches
+		{"abcdef", "^abc", true, true},
+		// verifies cache hit on the same string pattern
+		{"abcdef", "^abc", true, true},
+		// verifies that a non-matching raw string pattern returns false
+		{"xyz", "^abc", true, false},
+	}
+	for _, mt := range tests {
+		m := regexpMatcher{}
+		if result := m.Compare(mt.ValA, mt.ValB); result != mt.Expacted {
+			t.Errorf("RegexpMatcher(%#v, %#v string) returned %v when %v was expected", mt.ValA, mt.ValB, result, mt.Expacted)
+		}
+	}
+}
+
+func TestRegexpMatcherWithInvalidPattern(t *testing.T) {
+	// verifies that an invalid regex pattern string returns false instead of panicking
+	m := regexpMatcher{}
+	result := m.Compare("foo", "[invalid")
+	if result != false {
+		t.Errorf("RegexpMatcher with invalid pattern returned %v, expected false", result)
+	}
+}
+
+func TestNegativeRegexpMatcherWithStringValB(t *testing.T) {
+	tests := []matchTest{
+		// verifies that passing a raw string pattern (not pre-compiled) compiles and negation works
+		{"abcdef", "^abcdef$", true, false},
+		// verifies cache hit on the same string pattern
+		{"abcdef", "^abcdef$", true, false},
+		// verifies that a non-matching raw string pattern returns true (negated)
+		{"xyz", "^abcdef$", true, true},
+	}
+	for _, mt := range tests {
+		m := negativeRegexMatcher{}
+		if result := m.Compare(mt.ValA, mt.ValB); result != mt.Expacted {
+			t.Errorf("NegativeRegexMatcher(%#v, %#v string) returned %v when %v was expected", mt.ValA, mt.ValB, result, mt.Expacted)
+		}
+	}
+}
+
+func TestNegativeRegexpMatcherWithInvalidPattern(t *testing.T) {
+	// verifies that an invalid regex pattern string returns false instead of panicking
+	m := negativeRegexMatcher{}
+	result := m.Compare("foo", "[invalid")
+	if result != false {
+		t.Errorf("NegativeRegexMatcher with invalid pattern returned %v, expected false", result)
+	}
+}
+
 func TestNewMatcher(t *testing.T) {
 	operators := []string{
 		equalOperator,
diff --git a/internal/mapper/v017/api.go b/internal/mapper/v017/api.go
index f3480eeae..677fbcdaa 100644
--- a/internal/mapper/v017/api.go
+++ b/internal/mapper/v017/api.go
@@ -4,6 +4,7 @@ import (
 	"net/http"
 	"net/url"
 	"path"
+	"slices"
 	"sort"
 	"time"
 
@@ -52,7 +53,7 @@ func groups(c *client.AlertmanagerAPI, timeout time.Duration) ([]models.AlertGro
 		for k, v := range group.Labels {
 			ls = ls.Set(k, v)
 		}
-		sort.Sort(ls)
+		slices.SortFunc(ls, models.CompareLabels)
 		g := models.AlertGroup{
 			Receiver: models.NewUniqueString(*group.Receiver.Name),
 			Labels:   ls,
@@ -63,7 +64,7 @@ func groups(c *client.AlertmanagerAPI, timeout time.Duration) ([]models.AlertGro
 			for k, v := range alert.Labels {
 				ls = ls.Set(k, v)
 			}
-			sort.Sort(ls)
+			slices.SortFunc(ls, models.CompareLabels)
 			a := models.Alert{
 				Fingerprint:  *alert.Fingerprint,
 				Receiver:     models.NewUniqueString(*group.Receiver.Name),
diff --git a/internal/models/alert.go b/internal/models/alert.go
index 142cb2167..0f551c851 100644
--- a/internal/models/alert.go
+++ b/internal/models/alert.go
@@ -1,6 +1,7 @@
 package models
 
 import (
+	"cmp"
 	"encoding/json"
 	"strconv"
 	"time"
@@ -65,33 +66,37 @@ func (ls Labels) Map() map[string]string {
 	return m
 }
 
-func (ls Labels) Len() int {
-	return len(ls)
-}
-
-func (ls Labels) Swap(i, j int) {
-	ls[i], ls[j] = ls[j], ls[i]
-}
-
-func (ls Labels) Less(i, j int) bool {
-	ai, aj := -1, -1
+func CompareLabels(a, b Label) int {
+	ai, bi := -1, -1
 	for index, name := range config.Config.Labels.Order {
-		if ls[i].Name.Value() == name {
+		if a.Name.Value() == name {
 			ai = index
-		} else if ls[j].Name.Value() == name {
-			aj = index
+		} else if b.Name.Value() == name {
+			bi = index
 		}
-		if ai >= 0 && aj >= 0 {
-			return ai < aj
+		if ai >= 0 && bi >= 0 {
+			return cmp.Compare(ai, bi)
 		}
 	}
-	if ai != aj {
-		return aj < ai
+	if ai != bi {
+		return cmp.Compare(bi, ai)
 	}
-	if ls[i].Name.Value() == ls[j].Name.Value() {
-		return sortorder.NaturalLess(ls[i].Value.Value(), ls[j].Value.Value())
+	if a.Name.Value() == b.Name.Value() {
+		if sortorder.NaturalLess(a.Value.Value(), b.Value.Value()) {
+			return -1
+		}
+		if sortorder.NaturalLess(b.Value.Value(), a.Value.Value()) {
+			return 1
+		}
+		return 0
 	}
-	return sortorder.NaturalLess(ls[i].Name.Value(), ls[j].Name.Value())
+	if sortorder.NaturalLess(a.Name.Value(), b.Name.Value()) {
+		return -1
+	}
+	if sortorder.NaturalLess(b.Name.Value(), a.Name.Value()) {
+		return 1
+	}
+	return 0
 }
 
 func (ls Labels) Get(name string) *Label {
diff --git a/internal/models/alert_test.go b/internal/models/alert_test.go
index b480151ea..6f2db332a 100644
--- a/internal/models/alert_test.go
+++ b/internal/models/alert_test.go
@@ -1,10 +1,12 @@
 package models_test
 
 import (
+	"encoding/json"
 	"fmt"
-	"sort"
+	"slices"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/google/go-cmp/cmp"
 	"github.com/google/go-cmp/cmp/cmpopts"
@@ -144,6 +146,42 @@ func TestSortLabels(t *testing.T) {
 				{Name: models.NewUniqueString("bar"), Value: models.NewUniqueString("1")},
 			},
 		},
+		// verifies that identical labels stay in their original positions
+		{
+			order: []string{},
+			in: models.Labels{
+				{Name: models.NewUniqueString("foo"), Value: models.NewUniqueString("bar")},
+				{Name: models.NewUniqueString("foo"), Value: models.NewUniqueString("bar")},
+			},
+			out: models.Labels{
+				{Name: models.NewUniqueString("foo"), Value: models.NewUniqueString("bar")},
+				{Name: models.NewUniqueString("foo"), Value: models.NewUniqueString("bar")},
+			},
+		},
+		// verifies that same-name labels with different values sort by value descending naturally
+		{
+			order: []string{},
+			in: models.Labels{
+				{Name: models.NewUniqueString("foo"), Value: models.NewUniqueString("z")},
+				{Name: models.NewUniqueString("foo"), Value: models.NewUniqueString("a")},
+			},
+			out: models.Labels{
+				{Name: models.NewUniqueString("foo"), Value: models.NewUniqueString("a")},
+				{Name: models.NewUniqueString("foo"), Value: models.NewUniqueString("z")},
+			},
+		},
+		// verifies that completely identical name labels (no order config) with equal names sort by name naturally
+		{
+			order: []string{},
+			in: models.Labels{
+				{Name: models.NewUniqueString("zzz"), Value: models.NewUniqueString("1")},
+				{Name: models.NewUniqueString("aaa"), Value: models.NewUniqueString("1")},
+			},
+			out: models.Labels{
+				{Name: models.NewUniqueString("aaa"), Value: models.NewUniqueString("1")},
+				{Name: models.NewUniqueString("zzz"), Value: models.NewUniqueString("1")},
+			},
+		},
 	}
 
 	defer func() {
@@ -153,7 +191,7 @@ func TestSortLabels(t *testing.T) {
 	for i, testCase := range testCases {
 		t.Run(fmt.Sprintf("[%d] order=%v", i, testCase.order), func(t *testing.T) {
 			config.Config.Labels.Order = testCase.order
-			sort.Sort(testCase.in)
+			slices.SortFunc(testCase.in, models.CompareLabels)
 			if diff := cmp.Diff(testCase.in, testCase.out, cmpopts.EquateComparable(models.Label{})); diff != "" {
 				t.Errorf("Incorrectly sorted labels (-want +got):\n%s", diff)
 				t.FailNow()
@@ -161,3 +199,156 @@ func TestSortLabels(t *testing.T) {
 		})
 	}
 }
+
+func TestLabelsMap(t *testing.T) {
+	type testCaseT struct {
+		labels   models.Labels
+		expected map[string]string
+	}
+
+	testCases := []testCaseT{
+		// verifies that empty labels produce an empty map
+		{
+			labels:   models.Labels{},
+			expected: map[string]string{},
+		},
+		// verifies that labels are converted to a name->value map
+		{
+			labels: models.Labels{
+				{Name: models.NewUniqueString("foo"), Value: models.NewUniqueString("bar")},
+				{Name: models.NewUniqueString("baz"), Value: models.NewUniqueString("qux")},
+			},
+			expected: map[string]string{"foo": "bar", "baz": "qux"},
+		},
+	}
+
+	for _, tc := range testCases {
+		result := tc.labels.Map()
+		if diff := cmp.Diff(tc.expected, result); diff != "" {
+			t.Errorf("Labels.Map() mismatch (-want +got):\n%s", diff)
+		}
+	}
+}
+
+func TestLabelsGetValue(t *testing.T) {
+	labels := models.Labels{
+		{Name: models.NewUniqueString("foo"), Value: models.NewUniqueString("bar")},
+		{Name: models.NewUniqueString("baz"), Value: models.NewUniqueString("qux")},
+	}
+
+	type testCaseT struct {
+		name     string
+		expected string
+	}
+
+	testCases := []testCaseT{
+		// verifies that an existing label returns its value
+		{name: "foo", expected: "bar"},
+		// verifies that another existing label returns its value
+		{name: "baz", expected: "qux"},
+		// verifies that a missing label returns an empty string
+		{name: "missing", expected: ""},
+	}
+
+	for _, tc := range testCases {
+		result := labels.GetValue(tc.name)
+		if result != tc.expected {
+			t.Errorf("Labels.GetValue(%q) returned %q, expected %q", tc.name, result, tc.expected)
+		}
+	}
+}
+
+func TestUniqueStringJSONRoundTrip(t *testing.T) {
+	// verifies that UniqueString survives a JSON marshal/unmarshal round-trip
+	original := models.NewUniqueString("test_value")
+	data, err := json.Marshal(&original)
+	if err != nil {
+		t.Fatalf("json.Marshal failed: %s", err)
+	}
+	if string(data) != `"test_value"` {
+		t.Errorf("json.Marshal produced %s, expected %q", string(data), `"test_value"`)
+	}
+
+	var decoded models.UniqueString
+	err = json.Unmarshal(data, &decoded)
+	if err != nil {
+		t.Fatalf("json.Unmarshal failed: %s", err)
+	}
+	if decoded.Value() != "test_value" {
+		t.Errorf("json.Unmarshal produced %q, expected %q", decoded.Value(), "test_value")
+	}
+}
+
+func TestUniqueStringUnmarshalJSONError(t *testing.T) {
+	// verifies that UnmarshalJSON returns an error for invalid JSON input
+	var us models.UniqueString
+	err := json.Unmarshal([]byte(`{invalid`), &us)
+	if err == nil {
+		t.Error("json.Unmarshal should have returned an error for invalid JSON")
+	}
+}
+
+func TestUpdateFingerprints(t *testing.T) {
+	// verifies that UpdateFingerprints produces stable, non-empty fingerprints
+	// including the alertmanager instance, silenced-by, and inhibited-by branches
+	alert := models.Alert{
+		StartsAt:    time.Date(2020, 1, 1, 0, 0, 0, 0, time.UTC),
+		State:       models.NewUniqueString("active"),
+		Receiver:    models.NewUniqueString("default"),
+		Fingerprint: "abc123",
+		Labels: models.Labels{
+			{Name: models.NewUniqueString("alertname"), Value: models.NewUniqueString("TestAlert")},
+		},
+		Annotations: models.Annotations{
+			{
+				Name:     models.NewUniqueString("summary"),
+				Value:    models.NewUniqueString("test summary"),
+				Visible:  true,
+				IsLink:   false,
+				IsAction: false,
+			},
+		},
+		Alertmanager: []models.AlertmanagerInstance{
+			{
+				Fingerprint: "fp1",
+				Name:        "am1",
+				Cluster:     "cluster1",
+				State:       models.NewUniqueString("active"),
+				StartsAt:    time.Date(2020, 1, 1, 0, 0, 0, 0, time.UTC),
+				Source:      "http://source",
+				SilencedBy:  []string{"silence1", "silence2"},
+				InhibitedBy: []string{"inhibit1"},
+			},
+		},
+	}
+
+	alert.UpdateFingerprints()
+
+	if alert.LabelsFingerprint() == "" {
+		t.Error("LabelsFingerprint() returned empty string after UpdateFingerprints()")
+	}
+	if alert.ContentFingerprint() == "" {
+		t.Error("ContentFingerprint() returned empty string after UpdateFingerprints()")
+	}
+
+	// verifies that calling UpdateFingerprints again produces the same result
+	fp1 := alert.LabelsFingerprint()
+	cfp1 := alert.ContentFingerprint()
+	alert.UpdateFingerprints()
+	if alert.LabelsFingerprint() != fp1 {
+		t.Errorf("LabelsFingerprint() not stable: %q != %q", alert.LabelsFingerprint(), fp1)
+	}
+	if alert.ContentFingerprint() != cfp1 {
+		t.Errorf("ContentFingerprint() not stable: %q != %q", alert.ContentFingerprint(), cfp1)
+	}
+
+	// verifies that changing a label produces a different fingerprint
+	alert2 := alert
+	alert2.Labels = models.Labels{
+		{Name: models.NewUniqueString("alertname"), Value: models.NewUniqueString("DifferentAlert")},
+	}
+	alert2.UpdateFingerprints()
+	if alert2.LabelsFingerprint() == fp1 {
+		t.Error("LabelsFingerprint() should differ when labels change")
+	}
+}
diff --git a/internal/models/alertgroup.go b/internal/models/alertgroup.go
index 227a57a97..77340a083 100644
--- a/internal/models/alertgroup.go
+++ b/internal/models/alertgroup.go
@@ -1,6 +1,7 @@
 package models
 
 import (
+	"cmp"
 	"io"
 	"strconv"
 	"time"
@@ -11,23 +12,15 @@ import (
 // AlertList is flat list of karmaAlert objects
 type AlertList []Alert
 
-func (a AlertList) Len() int {
-	return len(a)
-}
-
-func (a AlertList) Swap(i, j int) {
-	a[i], a[j] = a[j], a[i]
-}
-
-func (a AlertList) Less(i, j int) bool {
+func CompareAlerts(a, b Alert) int {
 	// compare timestamps, if equal compare fingerprints to stable sort order
-	if a[i].StartsAt.After(a[j].StartsAt) {
-		return true
+	if a.StartsAt.After(b.StartsAt) {
+		return -1
 	}
-	if a[i].StartsAt.Before(a[j].StartsAt) {
-		return false
+	if a.StartsAt.Before(b.StartsAt) {
+		return 1
 	}
-	return a[i].LabelsFingerprint() < a[j].LabelsFingerprint()
+	return cmp.Compare(a.LabelsFingerprint(), b.LabelsFingerprint())
 }
 
 // AlertGroup is vanilla Alertmanager group, but alerts are flattened
diff --git a/internal/models/alertgroup_test.go b/internal/models/alertgroup_test.go
index 484580062..3810ca249 100644
--- a/internal/models/alertgroup_test.go
+++ b/internal/models/alertgroup_test.go
@@ -1,7 +1,7 @@
 package models_test
 
 import (
-	"sort"
+	"slices"
 	"testing"
 	"time"
 
@@ -83,7 +83,7 @@ func TestAlertListSort(t *testing.T) {
 	iterations := 100
 	failures := 0
 	for i := 1; i <= iterations; i++ {
-		sort.Sort(al)
+		slices.SortFunc(al, models.CompareAlerts)
 		for _, testCase := range alertListSortTests {
 			testCase.alert.UpdateFingerprints()
 			if al[testCase.position].ContentFingerprint() != testCase.alert.ContentFingerprint() {
@@ -202,7 +202,7 @@ func TestAlertGroupContentFingerprint(t *testing.T) {
 				alert.UpdateFingerprints()
 				alerts = append(alerts, alert)
 			}
-			sort.Sort(alerts)
+			slices.SortFunc(alerts, models.CompareAlerts)
 			testCase.ag.Alerts = alerts
 			// get alert group fingerprint
 			fp := testCase.ag.ContentFingerprint()
@@ -232,6 +232,45 @@ func TestFingerprint(t *testing.T) {
 	}
 }
 
+func TestLabelsFingerprint(t *testing.T) {
+	// verifies that LabelsFingerprint produces non-empty output when labels are present
+	ag := models.AlertGroup{
+		Receiver: models.NewUniqueString("default"),
+		Labels: models.Labels{
+			{Name: models.NewUniqueString("foo"), Value: models.NewUniqueString("bar")},
+			{Name: models.NewUniqueString("baz"), Value: models.NewUniqueString("qux")},
+		},
+	}
+	fp := ag.LabelsFingerprint()
+	if fp == "" {
+		t.Error("LabelsFingerprint() returned empty string for group with labels")
+	}
+
+	// verifies that different labels produce a different fingerprint
+	ag2 := models.AlertGroup{
+		Receiver: models.NewUniqueString("default"),
+		Labels: models.Labels{
+			{Name: models.NewUniqueString("different"), Value: models.NewUniqueString("label")},
+		},
+	}
+	fp2 := ag2.LabelsFingerprint()
+	if fp == fp2 {
+		t.Errorf("LabelsFingerprint() should differ for groups with different labels, both returned %q", fp)
+	}
+
+	// verifies that same receiver and labels produce the same fingerprint
+	ag3 := models.AlertGroup{
+		Receiver: models.NewUniqueString("default"),
+		Labels: models.Labels{
+			{Name: models.NewUniqueString("foo"), Value: models.NewUniqueString("bar")},
+			{Name: models.NewUniqueString("baz"), Value: models.NewUniqueString("qux")},
+		},
+	}
+	if ag3.LabelsFingerprint() != fp {
+		t.Errorf("LabelsFingerprint() not stable: %q != %q", ag3.LabelsFingerprint(), fp)
+	}
+}
+
 type findLatestStartsAtTest struct {
 	expectedStartsAt time.Time
 	alerts           []models.Alert
diff --git a/internal/models/annotation.go b/internal/models/annotation.go
index 59aa7cee2..9ad594a9f 100644
--- a/internal/models/annotation.go
+++ b/internal/models/annotation.go
@@ -3,7 +3,6 @@ package models
 import (
 	"net/url"
 	"slices"
-	"sort"
 	"strings"
 
 	"github.com/fvbommel/sortorder"
@@ -24,36 +23,40 @@ type Annotation struct {
 // Annotations is a slice of Annotation structs, needed to implement sorting
 type Annotations []Annotation
 
-func (a Annotations) Len() int {
-	return len(a)
-}
-
-func (a Annotations) Swap(i, j int) {
-	a[i], a[j] = a[j], a[i]
-}
-
-func (a Annotations) Less(i, j int) bool {
-	// Sort the anotations listed in config.Config.Annotations.Order first, in
+func compareAnnotations(a, b Annotation) int {
+	// Sort the annotations listed in config.Config.Annotations.Order first, in
 	// the order they appear in that list; remaining annotations are sorted alphabetically.
-	ai, aj := -1, -1
+	ai, bi := -1, -1
 	for index, name := range config.Config.Annotations.Order {
-		if a[i].Name.Value() == name {
+		if a.Name.Value() == name {
 			ai = index
-		} else if a[j].Name.Value() == name {
-			aj = index
+		} else if b.Name.Value() == name {
+			bi = index
 		}
 		// If both annotations are in c.C.A.Order, sort them according to the
 		// order in that list.
-		if ai >= 0 && aj >= 0 {
-			return ai < aj
+		if ai >= 0 && bi >= 0 {
+			if ai < bi {
+				return -1
+			}
+			return 1
 		}
 	}
 	// If only one of the annotations was in c.C.A.Order, that one goes first.
-	if ai != aj {
-		return aj < ai
+	if ai != bi {
+		if bi < ai {
+			return -1
+		}
+		return 1
 	}
 	// If neither annotation was in c.C.A.Order, sort alphabetically.
-	return sortorder.NaturalLess(a[i].Name.Value(), a[j].Name.Value())
+	if sortorder.NaturalLess(a.Name.Value(), b.Name.Value()) {
+		return -1
+	}
+	if sortorder.NaturalLess(b.Name.Value(), a.Name.Value()) {
+		return 1
+	}
+	return 0
 }
 
 // AnnotationsFromMap will convert a map[string]string to a list of Annotation
@@ -70,10 +73,14 @@ func AnnotationsFromMap(m map[string]string) Annotations {
 		}
 		annotations = append(annotations, a)
 	}
-	sort.Sort(annotations)
+	SortAnnotations(annotations)
 	return annotations
 }
 
+func SortAnnotations(annotations Annotations) {
+	slices.SortFunc(annotations, compareAnnotations)
+}
+
 var linkSchemes = []string{
 	"ftp",
 	"http",
diff --git a/internal/models/annotation_test.go b/internal/models/annotation_test.go
index 6d7aed464..f14162a44 100644
--- a/internal/models/annotation_test.go
+++ b/internal/models/annotation_test.go
@@ -1,7 +1,6 @@
 package models_test
 
 import (
-	"sort"
 	"testing"
 	"unique"
 
@@ -211,7 +210,7 @@ func TestAnnotationsSort(t *testing.T) {
 			IsLink:  true,
 		},
 	}
-	sort.Stable(annotations)
+	models.SortAnnotations(annotations)
 	if annotations[0].Name.Value() != "abc" {
 		t.Errorf("Expected 'abc' to be first, got '%s'", annotations[0].Name.Value())
 	}
@@ -248,7 +247,7 @@ func TestAnnotationsCustomOrderSort(t *testing.T) {
 		},
 	}
 	config.Config.Annotations.Order = []string{"xyz", "yyz"}
-	sort.Stable(annotations)
+	models.SortAnnotations(annotations)
 	if annotations[0].Name.Value() != "xyz" {
 		t.Errorf("Expected 'xyz' to be first, got '%s'", annotations[0].Name.Value())
 	}
@@ -262,3 +261,35 @@ func TestAnnotationsCustomOrderSort(t *testing.T) {
 		t.Errorf("Expected 'bar' to be last, got '%s'", annotations[3].Name.Value())
 	}
 }
+
+func TestAnnotationsSortIdenticalNames(t *testing.T) {
+	// verifies that annotations with the same name are treated as equal by the comparator
+	config.Config.Annotations.Order = []string{}
+	annotations := models.Annotations{
+		models.Annotation{
+			Name:    models.NewUniqueString("dup"),
+			Value:   models.NewUniqueString("second"),
+			Visible: true,
+		},
+		models.Annotation{
+			Name:    models.NewUniqueString("dup"),
+			Value:   models.NewUniqueString("first"),
+			Visible: true,
+		},
+		models.Annotation{
+			Name:    models.NewUniqueString("aaa"),
+			Value:   models.NewUniqueString("value"),
+			Visible: true,
+		},
+	}
+	models.SortAnnotations(annotations)
+	if annotations[0].Name.Value() != "aaa" {
+		t.Errorf("Expected 'aaa' to be first, got '%s'", annotations[0].Name.Value())
+	}
+	if annotations[1].Name.Value() != "dup" {
+		t.Errorf("Expected 'dup' to be second, got '%s'", annotations[1].Name.Value())
+	}
+	if annotations[2].Name.Value() != "dup" {
+		t.Errorf("Expected 'dup' to be third, got '%s'", annotations[2].Name.Value())
+	}
+}
diff --git a/internal/models/api.go b/internal/models/api.go
index 8ec7941da..bd059bfd6 100644
--- a/internal/models/api.go
+++ b/internal/models/api.go
@@ -1,6 +1,7 @@
 package models
 
 import (
+	"cmp"
 	"fmt"
 	"net/url"
 	"slices"
@@ -28,7 +29,7 @@ type Color struct {
 	Alpha uint8 `json:"alpha"`
 }
 
-func (c *Color) ToString() string {
+func (c *Color) String() string {
 	return fmt.Sprintf("rgba(%d,%d,%d,%d)", c.Red, c.Green, c.Blue, c.Alpha)
 }
 
@@ -55,19 +56,17 @@ type LabelValueStats struct {
 
 type LabelValueStatsList []LabelValueStats
 
-func (lvsl LabelValueStatsList) Len() int {
-	return len(lvsl)
-}
-
-func (lvsl LabelValueStatsList) Swap(i, j int) {
-	lvsl[i], lvsl[j] = lvsl[j], lvsl[i]
-}
-
-func (lvsl LabelValueStatsList) Less(i, j int) bool {
-	if lvsl[i].Hits == lvsl[j].Hits {
-		return sortorder.NaturalLess(lvsl[i].Value, lvsl[j].Value)
+func CompareLabelValueStats(a, b LabelValueStats) int {
+	if a.Hits != b.Hits {
+		return cmp.Compare(b.Hits, a.Hits)
 	}
-	return lvsl[i].Hits > lvsl[j].Hits
+	if sortorder.NaturalLess(a.Value, b.Value) {
+		return -1
+	}
+	if sortorder.NaturalLess(b.Value, a.Value) {
+		return 1
+	}
+	return 0
 }
 
 // LabelNameStats is used in the overview modal, it shows top labels across alerts
@@ -79,19 +78,11 @@ type LabelNameStats struct {
 
 type LabelNameStatsList []LabelNameStats
 
-func (lnsl LabelNameStatsList) Len() int {
-	return len(lnsl)
-}
-
-func (lnsl LabelNameStatsList) Swap(i, j int) {
-	lnsl[i], lnsl[j] = lnsl[j], lnsl[i]
-}
-
-func (lnsl LabelNameStatsList) Less(i, j int) bool {
-	if lnsl[i].Hits == lnsl[j].Hits {
-		return lnsl[i].Name < lnsl[j].Name
+func CompareLabelNameStats(a, b LabelNameStats) int {
+	if a.Hits != b.Hits {
+		return cmp.Compare(b.Hits, a.Hits)
 	}
-	return lnsl[i].Hits > lnsl[j].Hits
+	return cmp.Compare(a.Name, b.Name)
 }
 
 // APIAlertGroupSharedMaps defines shared part of APIAlertGroup
@@ -121,13 +112,8 @@ func (ag *APIAlertGroup) dedupLabels() {
 
 	for _, alert := range ag.Alerts {
 		for _, l := range alert.Labels {
-			key := fmt.Sprintf("%s\n%s", l.Name.Value(), l.Value.Value())
-			_, found := labelCounts[key]
-			if found {
-				labelCounts[key]++
-			} else {
-				labelCounts[key] = 1
-			}
+			key := l.Name.Value() + "\n" + l.Value.Value()
+			labelCounts[key]++
 		}
 	}
 
@@ -136,7 +122,7 @@ func (ag *APIAlertGroup) dedupLabels() {
 	for i, alert := range ag.Alerts {
 		newAlertLabels := Labels{}
 		for _, l := range alert.Labels {
-			key := fmt.Sprintf("%s\n%s", l.Name.Value(), l.Value.Value())
+			key := l.Name.Value() + "\n" + l.Value.Value()
 			if labelCounts[key] == totalAlerts {
 				sharedLabels = sharedLabels.Add(l)
 			} else {
@@ -183,27 +169,22 @@ func (ag *APIAlertGroup) dedupAnnotations() {
 
 	for _, alert := range ag.Alerts {
 		for _, annotation := range alert.Annotations {
-			key := fmt.Sprintf("%s\n%s", annotation.Name.Value(), annotation.Value.Value())
-			_, found := annotationCount[key]
-			if found {
-				annotationCount[key]++
-			} else {
-				annotationCount[key] = 1
-			}
+			key := annotation.Name.Value() + "\n" + annotation.Value.Value()
+			annotationCount[key]++
 		}
 	}
 
 	sharedAnnotations := Annotations{}
-	sharedKeys := []string{}
+	sharedKeys := map[string]struct{}{}
 
 	for i, alert := range ag.Alerts {
 		newAlertAnnotations := Annotations{}
 		for _, annotation := range alert.Annotations {
-			key := fmt.Sprintf("%s\n%s", annotation.Name.Value(), annotation.Value.Value())
+			key := annotation.Name.Value() + "\n" + annotation.Value.Value()
 			if annotationCount[key] == totalAlerts {
-				if !slices.Contains(sharedKeys, key) {
+				if _, ok := sharedKeys[key]; !ok {
 					sharedAnnotations = append(sharedAnnotations, annotation)
-					sharedKeys = append(sharedKeys, key)
+					sharedKeys[key] = struct{}{}
 				}
 			} else {
 				newAlertAnnotations = append(newAlertAnnotations, annotation)
@@ -222,21 +203,16 @@ func (ag *APIAlertGroup) dedupSilences() {
 
 	for _, alert := range ag.Alerts {
 		// process each cluster only once, rather than each alertmanager instance
-		clusters := []string{}
+		clusters := map[string]struct{}{}
 		for _, am := range alert.Alertmanager {
-			if slices.Contains(clusters, am.Cluster) {
+			if _, ok := clusters[am.Cluster]; ok {
 				continue
 			}
-			clusters = append(clusters, am.Cluster)
+			clusters[am.Cluster] = struct{}{}
 			for _, silenceID := range am.SilencedBy {
-				_, ok := silencesByCluster[am.Cluster]
-				if !ok {
+				if _, ok := silencesByCluster[am.Cluster]; !ok {
 					silencesByCluster[am.Cluster] = map[string]int{}
 				}
-				_, ok = silencesByCluster[am.Cluster][silenceID]
-				if !ok {
-					silencesByCluster[am.Cluster][silenceID] = 0
-				}
 				silencesByCluster[am.Cluster][silenceID]++
 			}
 		}
diff --git a/internal/models/api_test.go b/internal/models/api_test.go
index d5f3c4025..24bbc3c0a 100644
--- a/internal/models/api_test.go
+++ b/internal/models/api_test.go
@@ -3,7 +3,7 @@ package models_test
 import (
 	"bytes"
 	"encoding/json"
-	"sort"
+	"slices"
 	"testing"
 
 	"github.com/beme/abide"
@@ -11,6 +11,38 @@ import (
 	"github.com/prymitive/karma/internal/models"
 )
 
+func TestColorString(t *testing.T) {
+	type testCaseT struct {
+		color    models.Color
+		expected string
+	}
+
+	testCases := []testCaseT{
+		// verifies zero-value color produces all zeros
+		{
+			color:    models.Color{Red: 0, Green: 0, Blue: 0, Alpha: 0},
+			expected: "rgba(0,0,0,0)",
+		},
+		// verifies max-value color produces all 255s
+		{
+			color:    models.Color{Red: 255, Green: 255, Blue: 255, Alpha: 255},
+			expected: "rgba(255,255,255,255)",
+		},
+		// verifies mixed values are formatted correctly
+		{
+			color:    models.Color{Red: 10, Green: 20, Blue: 30, Alpha: 128},
+			expected: "rgba(10,20,30,128)",
+		},
+	}
+
+	for _, tc := range testCases {
+		result := tc.color.String()
+		if result != tc.expected {
+			t.Errorf("Color.String() returned %q, expected %q", result, tc.expected)
+		}
+	}
+}
+
 func TestDedupSharedMaps(t *testing.T) {
 	ag := models.APIAlertGroup{
 		AlertGroup: models.AlertGroup{
@@ -192,6 +224,105 @@ func TestDedupWithBadSource(t *testing.T) {
 	}
 }
 
+func TestDedupSharedMapsWithDropNames(t *testing.T) {
+	// verifies that passing dropNames to DedupSharedMaps removes those labels
+	// from both group labels and alert labels
+	ag := models.APIAlertGroup{
+		AlertGroup: models.AlertGroup{
+			Receiver: models.NewUniqueString("default"),
+			Labels: models.Labels{
+				{Name: models.NewUniqueString("alertname"), Value: models.NewUniqueString("TestAlert")},
+				{Name: models.NewUniqueString("cluster"), Value: models.NewUniqueString("prod")},
+			},
+			Alerts: models.AlertList{
+				models.Alert{
+					State: models.AlertStateActive,
+					Labels: models.Labels{
+						{Name: models.NewUniqueString("alertname"), Value: models.NewUniqueString("TestAlert")},
+						{Name: models.NewUniqueString("cluster"), Value: models.NewUniqueString("prod")},
+						{Name: models.NewUniqueString("instance"), Value: models.NewUniqueString("1")},
+					},
+				},
+				models.Alert{
+					State: models.AlertStateActive,
+					Labels: models.Labels{
+						{Name: models.NewUniqueString("alertname"), Value: models.NewUniqueString("TestAlert")},
+						{Name: models.NewUniqueString("cluster"), Value: models.NewUniqueString("prod")},
+						{Name: models.NewUniqueString("instance"), Value: models.NewUniqueString("2")},
+					},
+				},
+			},
+		},
+	}
+	ag.DedupSharedMaps([]string{"cluster"})
+
+	// "cluster" should be removed from group labels
+	if ag.Labels.Get("cluster") != nil {
+		t.Error("Expected 'cluster' label to be removed from group labels")
+	}
+	// "alertname" should remain in group labels
+	if ag.Labels.Get("alertname") == nil {
+		t.Error("Expected 'alertname' label to remain in group labels")
+	}
+	// alert labels should not contain "cluster" (dropped) or "alertname" (shared with group)
+	for i, alert := range ag.Alerts {
+		if alert.Labels.Get("cluster") != nil {
+			t.Errorf("Alert[%d]: expected 'cluster' label to be removed", i)
+		}
+		if alert.Labels.Get("alertname") != nil {
+			t.Errorf("Alert[%d]: expected 'alertname' label to be removed (shared with group)", i)
+		}
+	}
+}
+
+func TestCompareLabelValueStats(t *testing.T) {
+	type testCaseT struct {
+		a        models.LabelValueStats
+		b        models.LabelValueStats
+		expected int
+	}
+
+	testCases := []testCaseT{
+		// verifies that higher hits sorts before lower hits
+		{
+			a:        models.LabelValueStats{Value: "a", Hits: 10},
+			b:        models.LabelValueStats{Value: "b", Hits: 5},
+			expected: -1,
+		},
+		// verifies that lower hits sorts after higher hits
+		{
+			a:        models.LabelValueStats{Value: "a", Hits: 5},
+			b:        models.LabelValueStats{Value: "b", Hits: 10},
+			expected: 1,
+		},
+		// verifies that equal hits falls back to natural value ordering (a < b)
+		{
+			a:        models.LabelValueStats{Value: "a", Hits: 5},
+			b:        models.LabelValueStats{Value: "b", Hits: 5},
+			expected: -1,
+		},
+		// verifies that equal hits falls back to natural value ordering (b > a)
+		{
+			a:        models.LabelValueStats{Value: "b", Hits: 5},
+			b:        models.LabelValueStats{Value: "a", Hits: 5},
+			expected: 1,
+		},
+		// verifies that identical hits and values returns 0
+		{
+			a:        models.LabelValueStats{Value: "a", Hits: 5},
+			b:        models.LabelValueStats{Value: "a", Hits: 5},
+			expected: 0,
+		},
+	}
+
+	for _, tc := range testCases {
+		result := models.CompareLabelValueStats(tc.a, tc.b)
+		if result != tc.expected {
+			t.Errorf("CompareLabelValueStats(%v, %v) returned %d, expected %d", tc.a, tc.b, result, tc.expected)
+		}
+	}
+}
+
 func TestNameStatsSort(t *testing.T) {
 	nameStats := models.LabelNameStatsList{
 		{
@@ -400,9 +531,9 @@ func TestNameStatsSort(t *testing.T) {
 	before := string(b)
 
 	for _, n := range nameStats {
-		sort.Sort(n.Values)
+		slices.SortFunc(n.Values, models.CompareLabelValueStats)
 	}
-	sort.Sort(nameStats)
+	slices.SortFunc(nameStats, models.CompareLabelNameStats)
 
 	a, err := json.Marshal(nameStats)
 	if err != nil {
diff --git a/internal/slices/slices.go b/internal/slices/slices.go
index 27670dde9..6914533b5 100644
--- a/internal/slices/slices.go
+++ b/internal/slices/slices.go
@@ -4,36 +4,41 @@ import (
 	"crypto/sha1"
 	"encoding/hex"
 	"regexp"
-	"slices"
 )
 
 // StringSliceToSHA1 returns a SHA1 hash computed from a slice of strings
-func StringSliceToSHA1(stringArray []string) (string, error) {
+func StringSliceToSHA1(stringArray []string) string {
 	h := sha1.New()
 	for _, s := range stringArray {
 		_, _ = h.Write([]byte(s))
 		_, _ = h.Write([]byte("\n"))
 	}
-	return hex.EncodeToString(h.Sum(nil)), nil
+	return hex.EncodeToString(h.Sum(nil))
 }
 
 func StringSliceDiff(slice1, slice2 []string) ([]string, []string) {
 	missing := []string{}
 	extra := []string{}
 
-	var found bool
+	set1 := make(map[string]struct{}, len(slice1))
+	for _, s := range slice1 {
+		set1[s] = struct{}{}
+	}
 
-	for _, s1 := range slice1 {
-		found = slices.Contains(slice2, s1)
-		if !found {
-			missing = append(missing, s1)
+	set2 := make(map[string]struct{}, len(slice2))
+	for _, s := range slice2 {
+		set2[s] = struct{}{}
+	}
+
+	for _, s := range slice1 {
+		if _, ok := set2[s]; !ok {
+			missing = append(missing, s)
 		}
 	}
 
-	for _, s2 := range slice2 {
-		found = slices.Contains(slice1, s2)
-		if !found {
-			extra = append(extra, s2)
+	for _, s := range slice2 {
+		if _, ok := set1[s]; !ok {
+			extra = append(extra, s)
 		}
 	}
 
diff --git a/internal/slices/slices_test.go b/internal/slices/slices_test.go
index 642823e2d..a9baed6ad 100644
--- a/internal/slices/slices_test.go
+++ b/internal/slices/slices_test.go
@@ -1,6 +1,7 @@
 package slices_test
 
 import (
+	"regexp"
 	"testing"
 
 	"github.com/prymitive/karma/internal/slices"
@@ -9,10 +10,7 @@ import (
 )
 
 func TestStringSliceToSHA1(t *testing.T) {
-	s, err := slices.StringSliceToSHA1([]string{"a", "b", "c"})
-	if err != nil {
-		t.Errorf("StringSliceToSHA1() returned error: %s", err)
-	}
+	s := slices.StringSliceToSHA1([]string{"a", "b", "c"})
 	if s == "" {
 		t.Errorf("StringSliceToSHA1() returned empty string")
 	}
@@ -63,3 +61,45 @@ func TestStringSliceDiff(t *testing.T) {
 		}
 	}
 }
+
+func TestMatchesAnyRegex(t *testing.T) {
+	type testCaseT struct {
+		value    string
+		regexes  []*regexp.Regexp
+		expected bool
+	}
+
+	testCases := []testCaseT{
+		// verifies that an empty regex list never matches
+		{
+			value:    "foo",
+			regexes:  []*regexp.Regexp{},
+			expected: false,
+		},
+		// verifies that a matching regex returns true
+		{
+			value:    "foo",
+			regexes:  []*regexp.Regexp{regexp.MustCompile("^foo$")},
+			expected: true,
+		},
+		// verifies that a non-matching regex returns false
+		{
+			value:    "bar",
+			regexes:  []*regexp.Regexp{regexp.MustCompile("^foo$")},
+			expected: false,
+		},
+		// verifies that the second regex in the list can match
+		{
+			value:    "bar",
+			regexes:  []*regexp.Regexp{regexp.MustCompile("^foo$"), regexp.MustCompile("^bar$")},
+			expected: true,
+		},
+	}
+
+	for _, tc := range testCases {
+		result := slices.MatchesAnyRegex(tc.value, tc.regexes)
+		if result != tc.expected {
+			t.Errorf("MatchesAnyRegex(%q, ...) returned %v, expected %v", tc.value, result, tc.expected)
+		}
+	}
+}
diff --git a/internal/transform/colors.go b/internal/transform/colors.go
index 5e82dc592..aa7ae38f5 100644
--- a/internal/transform/colors.go
+++ b/internal/transform/colors.go
@@ -59,7 +59,7 @@ func parseCustomColor(colorStore models.LabelsColorMap, key, val, customColor st
 	}
 	colorStore[key][val] = models.LabelColors{
 		Brightness: brightness,
-		Background: bc.ToString(),
+		Background: bc.String(),
 	}
 }
 
@@ -102,7 +102,7 @@ func ColorLabel(colorStore models.LabelsColorMap, key, val string) {
 			brightness := rgbToBrightness(bc.Red, bc.Green, bc.Blue)
 			colorStore[key][val] = models.LabelColors{
 				Brightness: brightness,
-				Background: bc.ToString(),
+				Background: bc.String(),
 			}
 		}
 	}
diff --git a/internal/transform/strip.go b/internal/transform/strip.go
index 1304bcd5c..42fba1aa3 100644
--- a/internal/transform/strip.go
+++ b/internal/transform/strip.go
@@ -3,17 +3,16 @@ package transform
 import (
 	"regexp"
 	"slices"
-	"sort"
 	"strings"
 
 	"github.com/prymitive/karma/internal/models"
 	sliceutils "github.com/prymitive/karma/internal/slices"
 )
 
-// StripLables allows filtering out some labels from alerts
+// StripLabels allows filtering out some labels from alerts
 // it takes the list of label keys to ignore and alert label map
 // it will return label map without labels found on the ignore list
-func StripLables(keptLabels, ignoredLabels []string, keptLabelsRegex, ignoredLabelsRegex []*regexp.Regexp,
+func StripLabels(keptLabels, ignoredLabels []string, keptLabelsRegex, ignoredLabelsRegex []*regexp.Regexp,
 	sourceLabels models.Labels,
 ) models.Labels {
 	// empty keep lists means keep everything by default
@@ -39,7 +38,7 @@ func StripLables(keptLabels, ignoredLabels []string, keptLabelsRegex, ignoredLab
 			labels = labels.Add(l)
 		}
 	}
-	sort.Sort(labels)
+	slices.SortFunc(labels, models.CompareLabels)
 	return labels
 }
 
diff --git a/internal/transform/strip_test.go b/internal/transform/strip_test.go
index 08f8530f0..feb2ff5ec 100644
--- a/internal/transform/strip_test.go
+++ b/internal/transform/strip_test.go
@@ -180,7 +180,7 @@ func TestStripLables(t *testing.T) {
 	for _, testCase := range stripLabelTests {
 		keepRegex := getCompiledRegex(testCase.keepRegex, t)
 		stripRegex := getCompiledRegex(testCase.stripRegex, t)
-		labels := transform.StripLables(testCase.keep, testCase.strip, keepRegex, stripRegex, testCase.before)
+		labels := transform.StripLabels(testCase.keep, testCase.strip, keepRegex, stripRegex, testCase.before)
 		if !reflect.DeepEqual(labels, testCase.after) {
 			t.Errorf("StripLables failed, expected %v, got %v", testCase.after, labels)
 		}