diff --git a/internal/cluster/probe.go b/internal/cluster/probe.go
index 41828ae..93dbf66 100644
--- a/internal/cluster/probe.go
+++ b/internal/cluster/probe.go
@@ -157,7 +157,7 @@ loop:
 			results = append(results, probeResultItem{
 				SiteID:      s.ID,
 				LatencyNs:   cr.LatencyNs,
-				IsUp:        cr.Status == "UP",
+				IsUp:        cr.Status == string(models.StatusUp),
 				ErrorReason: cr.ErrorReason,
 			})
 			mu.Unlock()
diff --git a/internal/metrics/prometheus.go b/internal/metrics/prometheus.go
index 05446f4..235b152 100644
--- a/internal/metrics/prometheus.go
+++ b/internal/metrics/prometheus.go
@@ -2,11 +2,12 @@ package metrics
 
 import (
 	"fmt"
-	"gitea.lerkolabs.com/lerkolabs/uptop/internal/models"
-	"gitea.lerkolabs.com/lerkolabs/uptop/internal/monitor"
 	"net/http"
 	"sort"
 	"strings"
+
+	"gitea.lerkolabs.com/lerkolabs/uptop/internal/models"
+	"gitea.lerkolabs.com/lerkolabs/uptop/internal/monitor"
 )
 
 func Handler(eng *monitor.Engine) http.HandlerFunc {
@@ -19,7 +20,7 @@ func Handler(eng *monitor.Engine) http.HandlerFunc {
 		writeHelp(&b, "uptop_monitor_up", "gauge", "Whether the monitor is up (1) or down (0).")
 		for _, s := range sites {
 			val := 0
-			if s.Status == "UP" {
+			if s.Status == models.StatusUp {
 				val = 1
 			}
 			writeGauge(&b, "uptop_monitor_up", labels(s), float64(val))
diff --git a/internal/models/models.go b/internal/models/models.go
index 98c1be5..668b9dd 100644
--- a/internal/models/models.go
+++ b/internal/models/models.go
@@ -28,7 +28,7 @@ type Site struct {
 	Regions        string
 
 	FailureCount    int
-	Status          string
+	Status          Status
 	StatusCode      int
 	Latency         time.Duration
 	CertExpiry      time.Time
diff --git a/internal/models/status.go b/internal/models/status.go
new file mode 100644
index 0000000..50275c1
--- /dev/null
+++ b/internal/models/status.go
@@ -0,0 +1,18 @@
+package models
+
+type Status string
+
+const (
+	StatusUp      Status = "UP"
+	StatusDown    Status = "DOWN"
+	StatusPending Status = "PENDING"
+	StatusLate    Status = "LATE"
+	StatusStale   Status = "STALE"
+	StatusSSLExp  Status = "SSL EXP"
+)
+
+func (s Status) IsBroken() bool {
+	return s == StatusDown || s == StatusSSLExp
+}
+
+func (s Status) String() string { return string(s) }
diff --git a/internal/monitor/checker.go b/internal/monitor/checker.go
index 48abc97..13abce2 100644
--- a/internal/monitor/checker.go
+++ b/internal/monitor/checker.go
@@ -47,7 +47,7 @@ func RunCheck(ctx context.Context, site models.Site, strict, insecure *http.Clie
 			if ips, err := net.LookupIP(host); err == nil {
 				for _, ip := range ips {
 					if isPrivateIP(ip) {
-						return CheckResult{SiteID: site.ID, Status: "DOWN", ErrorReason: "target resolves to private IP"}
+						return CheckResult{SiteID: site.ID, Status: string(models.StatusDown), ErrorReason: "target resolves to private IP"}
 					}
 				}
 			}
@@ -64,7 +64,7 @@ func RunCheck(ctx context.Context, site models.Site, strict, insecure *http.Clie
 	case "dns":
 		return runDNSCheck(ctx, site)
 	default:
-		return CheckResult{SiteID: site.ID, Status: "DOWN", ErrorReason: "unsupported monitor type: " + site.Type}
+		return CheckResult{SiteID: site.ID, Status: string(models.StatusDown), ErrorReason: "unsupported monitor type: " + site.Type}
 	}
 }
 
@@ -80,7 +80,7 @@ func runHTTPCheck(ctx context.Context, site models.Site, strict, insecure *http.
 
 	req, err := http.NewRequestWithContext(ctx, method, site.URL, nil)
 	if err != nil {
-		return CheckResult{SiteID: site.ID, Status: "DOWN", ErrorReason: "invalid request: " + err.Error()}
+		return CheckResult{SiteID: site.ID, Status: string(models.StatusDown), ErrorReason: "invalid request: " + err.Error()}
 	}
 
 	client := strict
@@ -94,12 +94,12 @@ func runHTTPCheck(ctx context.Context, site models.Site, strict, insecure *http.
 
 	result := CheckResult{
 		SiteID:    site.ID,
-		Status:    "UP",
+		Status:    string(models.StatusUp),
 		LatencyNs: latency.Nanoseconds(),
 	}
 
 	if err != nil {
-		result.Status = "DOWN"
+		result.Status = string(models.StatusDown)
 		result.ErrorReason = truncateError(err.Error(), maxErrorLength)
 		return result
 	}
@@ -107,7 +107,7 @@ func runHTTPCheck(ctx context.Context, site models.Site, strict, insecure *http.
 
 	result.StatusCode = resp.StatusCode
 	if !isCodeAccepted(resp.StatusCode, site.AcceptedCodes) {
-		result.Status = "DOWN"
+		result.Status = string(models.StatusDown)
 		expected := site.AcceptedCodes
 		if expected == "" {
 			expected = defaultAcceptedCodes
@@ -120,7 +120,7 @@ func runHTTPCheck(ctx context.Context, site models.Site, strict, insecure *http.
 		cert := resp.TLS.PeerCertificates[0]
 		result.CertExpiry = cert.NotAfter
 		if time.Now().After(cert.NotAfter) {
-			result.Status = "SSL EXP"
+			result.Status = string(models.StatusSSLExp)
 			result.ErrorReason = "SSL certificate expired"
 		}
 	}
@@ -136,7 +136,7 @@ func runPingCheck(_ context.Context, site models.Site) CheckResult {
 
 	pinger, err := probing.NewPinger(host)
 	if err != nil {
-		return CheckResult{SiteID: site.ID, Status: "DOWN", ErrorReason: "ping setup: " + err.Error()}
+		return CheckResult{SiteID: site.ID, Status: string(models.StatusDown), ErrorReason: "ping setup: " + err.Error()}
 	}
 	pinger.Count = 1
 	pinger.Timeout = siteTimeout(site)
@@ -147,14 +147,14 @@ func runPingCheck(_ context.Context, site models.Site) CheckResult {
 	latency := time.Since(start)
 
 	if err != nil {
-		return CheckResult{SiteID: site.ID, Status: "DOWN", LatencyNs: latency.Nanoseconds(), ErrorReason: "ping failed: " + err.Error()}
+		return CheckResult{SiteID: site.ID, Status: string(models.StatusDown), LatencyNs: latency.Nanoseconds(), ErrorReason: "ping failed: " + err.Error()}
 	}
 	if pinger.Statistics().PacketsRecv == 0 {
-		return CheckResult{SiteID: site.ID, Status: "DOWN", LatencyNs: latency.Nanoseconds(), ErrorReason: "no ICMP response"}
+		return CheckResult{SiteID: site.ID, Status: string(models.StatusDown), LatencyNs: latency.Nanoseconds(), ErrorReason: "no ICMP response"}
 	}
 
 	stats := pinger.Statistics()
-	return CheckResult{SiteID: site.ID, Status: "UP", LatencyNs: stats.AvgRtt.Nanoseconds()}
+	return CheckResult{SiteID: site.ID, Status: string(models.StatusUp), LatencyNs: stats.AvgRtt.Nanoseconds()}
 }
 
 func runPortCheck(_ context.Context, site models.Site) CheckResult {
@@ -170,10 +170,10 @@ func runPortCheck(_ context.Context, site models.Site) CheckResult {
 	latency := time.Since(start)
 
 	if err != nil {
-		return CheckResult{SiteID: site.ID, Status: "DOWN", LatencyNs: latency.Nanoseconds(), ErrorReason: truncateError(err.Error(), maxErrorLength)}
+		return CheckResult{SiteID: site.ID, Status: string(models.StatusDown), LatencyNs: latency.Nanoseconds(), ErrorReason: truncateError(err.Error(), maxErrorLength)}
 	}
 	_ = conn.Close()
-	return CheckResult{SiteID: site.ID, Status: "UP", LatencyNs: latency.Nanoseconds()}
+	return CheckResult{SiteID: site.ID, Status: string(models.StatusUp), LatencyNs: latency.Nanoseconds()}
 }
 
 func runDNSCheck(_ context.Context, site models.Site) CheckResult {
@@ -221,12 +221,12 @@ func runDNSCheck(_ context.Context, site models.Site) CheckResult {
 	latency := time.Since(start)
 
 	if err != nil {
-		return CheckResult{SiteID: site.ID, Status: "DOWN", LatencyNs: latency.Nanoseconds(), ErrorReason: "DNS query failed: " + err.Error()}
+		return CheckResult{SiteID: site.ID, Status: string(models.StatusDown), LatencyNs: latency.Nanoseconds(), ErrorReason: "DNS query failed: " + err.Error()}
 	}
 	if r.Rcode != dns.RcodeSuccess {
-		return CheckResult{SiteID: site.ID, Status: "DOWN", StatusCode: r.Rcode, LatencyNs: latency.Nanoseconds(), ErrorReason: "DNS RCODE: " + dns.RcodeToString[r.Rcode]}
+		return CheckResult{SiteID: site.ID, Status: string(models.StatusDown), StatusCode: r.Rcode, LatencyNs: latency.Nanoseconds(), ErrorReason: "DNS RCODE: " + dns.RcodeToString[r.Rcode]}
 	}
-	return CheckResult{SiteID: site.ID, Status: "UP", LatencyNs: latency.Nanoseconds()}
+	return CheckResult{SiteID: site.ID, Status: string(models.StatusUp), LatencyNs: latency.Nanoseconds()}
 }
 
 func siteTimeout(site models.Site) time.Duration {
diff --git a/internal/monitor/monitor.go b/internal/monitor/monitor.go
index c9ae786..ff7cca3 100644
--- a/internal/monitor/monitor.go
+++ b/internal/monitor/monitor.go
@@ -334,7 +334,7 @@ func (e *Engine) RecordHeartbeat(token string) bool {
 	}
 
 	var (
-		prevStatus string
+		prevStatus models.Status
 		name       string
 		alertID    int
 		downSince  time.Time
@@ -346,12 +346,12 @@ func (e *Engine) RecordHeartbeat(token string) bool {
 		downSince = s.StatusChangedAt // captured before mutation = when it went down
 
 		s.LastCheck = time.Now()
-		s.Status = "UP"
+		s.Status = models.StatusUp
 		s.FailureCount = 0
 		s.Latency = 0
 		s.LastError = ""
 		s.LastSuccessAt = time.Now()
-		if prevStatus != "UP" {
+		if prevStatus != models.StatusUp {
 			s.StatusChangedAt = time.Now()
 		}
 	})
@@ -360,13 +360,13 @@ func (e *Engine) RecordHeartbeat(token string) bool {
 	}
 
 	switch prevStatus {
-	case "PENDING":
+	case models.StatusPending:
 		e.AddLog(fmt.Sprintf("Push Monitor '%s' received first heartbeat", name))
-	case "LATE":
+	case models.StatusLate:
 		e.AddLog(fmt.Sprintf("Push Monitor '%s' heartbeat arrived (was late)", name))
-	case "STALE":
+	case models.StatusStale:
 		e.AddLog(fmt.Sprintf("Push Monitor '%s' heartbeat arrived (was stale)", name))
-	case "DOWN":
+	case models.StatusDown:
 		downDur := ""
 		if !downSince.IsZero() {
 			downDur = fmt.Sprintf(" (was down %s)", fmtDurationShort(time.Since(downSince)))
@@ -375,8 +375,8 @@ func (e *Engine) RecordHeartbeat(token string) bool {
 		go e.triggerAlert(alertID, "✅ RECOVERY", fmt.Sprintf("Push Monitor '%s' is receiving heartbeats.%s", name, downDur))
 	}
 
-	if prevStatus != "UP" && prevStatus != "PENDING" {
-		e.enqueueWrite(writeStateChange{siteID: targetID, fromStatus: prevStatus, toStatus: "UP"})
+	if prevStatus != models.StatusUp && prevStatus != models.StatusPending {
+		e.enqueueWrite(writeStateChange{siteID: targetID, fromStatus: string(prevStatus), toStatus: string(models.StatusUp)})
 	}
 
 	return true
@@ -434,12 +434,12 @@ func (e *Engine) Start(ctx context.Context) {
 				e.mu.RUnlock()
 				if !exists {
 					e.mu.Lock()
-					s.Status = "PENDING"
+					s.Status = models.StatusPending
 					if h, ok := e.GetHistory(s.ID); ok && len(h.Statuses) > 0 {
 						if h.Statuses[len(h.Statuses)-1] {
-							s.Status = "UP"
+							s.Status = models.StatusUp
 						} else {
-							s.Status = "DOWN"
+							s.Status = models.StatusDown
 						}
 						if len(h.Latencies) > 0 {
 							s.Latency = h.Latencies[len(h.Latencies)-1]
@@ -686,7 +686,7 @@ func (e *Engine) checkByID(ctx context.Context, id int) {
 }
 
 func (e *Engine) checkPush(_ context.Context, site models.Site) {
-	if site.Status == "PENDING" {
+	if site.Status == models.StatusPending {
 		return
 	}
 
@@ -702,16 +702,16 @@ func (e *Engine) checkPush(_ context.Context, site models.Site) {
 	now := time.Now()
 
 	if now.After(graceEnd) {
-		if site.Status != "DOWN" {
-			e.handleStatusChange(site, "DOWN", 0, 0, "heartbeat missed")
+		if site.Status != models.StatusDown {
+			e.handleStatusChange(site, string(models.StatusDown), 0, 0, "heartbeat missed")
 		}
 	} else if now.After(staleMark) {
-		if site.Status != "STALE" {
-			e.handleStatusChange(site, "STALE", 0, 0, "heartbeat stale")
+		if site.Status != models.StatusStale {
+			e.handleStatusChange(site, string(models.StatusStale), 0, 0, "heartbeat stale")
 		}
 	} else if now.After(overdue) {
-		if site.Status != "LATE" {
-			e.handleStatusChange(site, "LATE", 0, 0, "heartbeat overdue")
+		if site.Status != models.StatusLate {
+			e.handleStatusChange(site, string(models.StatusLate), 0, 0, "heartbeat overdue")
 		}
 	}
 }
@@ -727,9 +727,10 @@ func (e *Engine) handleStatusChange(snap models.Site, rawStatus string, code int
 	}
 
 	inMaint := e.isInMaintenance(snap.ID)
+	status := models.Status(rawStatus)
 
 	var (
-		prev, next            string
+		prev, next            models.Status
 		name, typ             string
 		alertID               int
 		failCount, maxRetries int
@@ -745,7 +746,7 @@ func (e *Engine) handleStatusChange(snap models.Site, rawStatus string, code int
 	_, exists := e.applyState(snap.ID, func(s *models.Site) {
 		// A non-UP result computed from a stale snapshot must not override a
 		// heartbeat (or newer check) that landed while we were evaluating.
-		if rawStatus != "UP" && s.LastCheck.After(snap.LastCheck) {
+		if status != models.StatusUp && s.LastCheck.After(snap.LastCheck) {
 			skipped = true
 			return
 		}
@@ -764,24 +765,24 @@ func (e *Engine) handleStatusChange(snap models.Site, rawStatus string, code int
 		s.HasSSL = snap.HasSSL
 		s.CertExpiry = snap.CertExpiry
 		s.LastError = errorReason
-		if rawStatus == "UP" {
+		if status == models.StatusUp {
 			s.LastSuccessAt = time.Now()
 			s.LastError = ""
 		}
 
 		// Status + failure-count transition, based on the CURRENT live status.
-		if rawStatus == "UP" {
+		if status == models.StatusUp {
 			s.FailureCount = 0
-			s.Status = "UP"
+			s.Status = models.StatusUp
 		} else {
 			if s.FailureCount <= s.MaxRetries {
 				s.FailureCount++
 			}
 			if s.FailureCount > s.MaxRetries {
-				if s.Status != rawStatus {
+				if s.Status != status {
 					confirmedDown = true
 				}
-				s.Status = rawStatus
+				s.Status = status
 				s.FailureCount = s.MaxRetries + 1
 			} else {
 				failedCheck = true
@@ -789,16 +790,16 @@ func (e *Engine) handleStatusChange(snap models.Site, rawStatus string, code int
 		}
 		failCount = s.FailureCount
 
-		if s.Status != prev && prev != "PENDING" {
+		if s.Status != prev && prev != models.StatusPending {
 			s.StatusChangedAt = time.Now()
-		} else if s.StatusChangedAt.IsZero() && s.Status != "PENDING" {
+		} else if s.StatusChangedAt.IsZero() && s.Status != models.StatusPending {
 			s.StatusChangedAt = time.Now()
 		}
 
 		// SSL expiry warning (fresh HasSSL/CertExpiry + config threshold).
 		if typ == "http" && s.CheckSSL && s.HasSSL {
 			days := int(time.Until(s.CertExpiry).Hours() / 24)
-			if days <= s.ExpiryThreshold && !s.SentSSLWarning && rawStatus != "SSL EXP" {
+			if days <= s.ExpiryThreshold && !s.SentSSLWarning && status != models.StatusSSLExp {
 				sslWarnFire = true
 				sslDays = days
 				s.SentSSLWarning = true
@@ -815,7 +816,7 @@ func (e *Engine) handleStatusChange(snap models.Site, rawStatus string, code int
 		return
 	}
 
-	e.recordCheck(snap.ID, latency, rawStatus == "UP")
+	e.recordCheck(snap.ID, latency, status == models.StatusUp)
 
 	if confirmedDown {
 		if errorReason != "" {
@@ -827,8 +828,8 @@ func (e *Engine) handleStatusChange(snap models.Site, rawStatus string, code int
 		e.AddLog(fmt.Sprintf("Monitor '%s' failed check %d/%d", name, failCount, maxRetries))
 	}
 
-	if changed && prev != "PENDING" {
-		e.enqueueWrite(writeStateChange{siteID: snap.ID, fromStatus: prev, toStatus: next, reason: errorReason})
+	if changed && prev != models.StatusPending {
+		e.enqueueWrite(writeStateChange{siteID: snap.ID, fromStatus: string(prev), toStatus: string(next), reason: errorReason})
 	}
 
 	if sslWarnFire {
@@ -839,13 +840,11 @@ func (e *Engine) handleStatusChange(snap models.Site, rawStatus string, code int
 		}
 	}
 
-	isBroken := func(s string) bool { return s == "DOWN" || s == "SSL EXP" }
-
-	if prev == "UP" && next == "LATE" {
+	if prev == models.StatusUp && next == models.StatusLate {
 		e.AddLog(fmt.Sprintf("Monitor '%s' heartbeat overdue", name))
 	}
 
-	if !isBroken(prev) && isBroken(next) && next != "PENDING" {
+	if !prev.IsBroken() && next.IsBroken() && next != models.StatusPending {
 		if inMaint {
 			e.AddLog(fmt.Sprintf("Monitor '%s' is DOWN (alerts suppressed — maintenance)", name))
 		} else {
@@ -859,7 +858,7 @@ func (e *Engine) handleStatusChange(snap models.Site, rawStatus string, code int
 			e.triggerAlert(alertID, "🚨 ALERT", msg)
 		}
 	}
-	if isBroken(prev) && next == "UP" {
+	if prev.IsBroken() && next == models.StatusUp {
 		downDur := ""
 		if !downSince.IsZero() {
 			downDur = fmt.Sprintf(" (was down %s)", fmtDurationShort(time.Since(downSince)))
@@ -869,7 +868,7 @@ func (e *Engine) handleStatusChange(snap models.Site, rawStatus string, code int
 			e.triggerAlert(alertID, "✅ RECOVERY", fmt.Sprintf("Monitor '%s' is UP%s", name, downDur))
 		}
 	}
-	if prev == "LATE" && next == "UP" && !isBroken(prev) {
+	if prev == models.StatusLate && next == models.StatusUp && !prev.IsBroken() {
 		e.AddLog(fmt.Sprintf("Monitor '%s' heartbeat arrived (was late)", name))
 	}
 }
@@ -991,12 +990,12 @@ func (e *Engine) GetDisplayStatus(site models.Site) string {
 	if e.isInMaintenance(site.ID) {
 		return "MAINT"
 	}
-	return site.Status
+	return string(site.Status)
 }
 
 func (e *Engine) checkGroup(_ context.Context, site models.Site) {
 	e.mu.RLock()
-	status := "UP"
+	status := models.StatusUp
 	hasChildren := false
 	for _, child := range e.liveState {
 		if child.ParentID != site.ID || child.Type == "group" {
@@ -1006,20 +1005,20 @@ func (e *Engine) checkGroup(_ context.Context, site models.Site) {
 		if child.Paused || e.isInMaintenance(child.ID) {
 			continue
 		}
-		if child.Status == "DOWN" || child.Status == "SSL EXP" {
-			status = "DOWN"
-		} else if child.Status == "STALE" && status != "DOWN" {
-			status = "STALE"
-		} else if child.Status == "LATE" && status != "DOWN" && status != "STALE" {
-			status = "LATE"
-		} else if child.Status == "PENDING" && status != "DOWN" && status != "STALE" && status != "LATE" {
-			status = "PENDING"
+		if child.Status == models.StatusDown || child.Status == models.StatusSSLExp {
+			status = models.StatusDown
+		} else if child.Status == models.StatusStale && status != models.StatusDown {
+			status = models.StatusStale
+		} else if child.Status == models.StatusLate && status != models.StatusDown && status != models.StatusStale {
+			status = models.StatusLate
+		} else if child.Status == models.StatusPending && status != models.StatusDown && status != models.StatusStale && status != models.StatusLate {
+			status = models.StatusPending
 		}
 	}
 	e.mu.RUnlock()
 
 	if !hasChildren {
-		status = "PENDING"
+		status = models.StatusPending
 	}
 
 	e.applyState(site.ID, func(s *models.Site) {
@@ -1072,15 +1071,15 @@ func (e *Engine) IngestProbeResult(nodeID string, siteID int, latencyNs int64, i
 
 	aggUp, avgLatency := AggregateStatus(results, e.aggStrategy)
 
-	rawStatus := "UP"
+	probeStatus := models.StatusUp
 	if !aggUp {
-		rawStatus = "DOWN"
+		probeStatus = models.StatusDown
 	}
 
 	updatedSite := site
 	updatedSite.Latency = time.Duration(avgLatency)
 	updatedSite.LastCheck = time.Now()
-	e.handleStatusChange(updatedSite, rawStatus, 0, time.Duration(avgLatency), errorReason)
+	e.handleStatusChange(updatedSite, string(probeStatus), 0, time.Duration(avgLatency), errorReason)
 }
 
 func (e *Engine) GetProbeResults(siteID int) map[string]NodeResult {
diff --git a/internal/monitor/sla.go b/internal/monitor/sla.go
index 90656cf..cfa815a 100644
--- a/internal/monitor/sla.go
+++ b/internal/monitor/sla.go
@@ -16,14 +16,14 @@ type SLAReport struct {
 	MTBF        time.Duration
 }
 
-func ComputeSLA(changes []models.StateChange, currentStatus string, window time.Duration) SLAReport {
+func ComputeSLA(changes []models.StateChange, currentStatus models.Status, window time.Duration) SLAReport {
 	now := time.Now()
 	windowStart := now.Add(-window)
 
 	report := SLAReport{Window: window}
 
 	if len(changes) == 0 {
-		if isDown(currentStatus) {
+		if models.Status(currentStatus).IsBroken() {
 			report.UptimePct = 0
 			report.Downtime = window
 		} else {
@@ -40,7 +40,7 @@ func ComputeSLA(changes []models.StateChange, currentStatus string, window time.
 	}
 
 	// Determine status at window start: last transition before or at windowStart.
-	statusAtStart := "UP"
+	statusAtStart := string(models.StatusUp)
 	for i := len(sorted) - 1; i >= 0; i-- {
 		if !sorted[i].ChangedAt.After(windowStart) {
 			statusAtStart = sorted[i].ToStatus
@@ -51,7 +51,7 @@ func ComputeSLA(changes []models.StateChange, currentStatus string, window time.
 	var upTime, downTime time.Duration
 	var outages []time.Duration
 	cursor := windowStart
-	wasDown := isDown(statusAtStart)
+	wasDown := models.Status(statusAtStart).IsBroken()
 
 	if wasDown {
 		report.OutageCount = 1
@@ -77,7 +77,7 @@ func ComputeSLA(changes []models.StateChange, currentStatus string, window time.
 			upTime += seg
 		}
 
-		newDown := isDown(sc.ToStatus)
+		newDown := models.Status(sc.ToStatus).IsBroken()
 		if !wasDown && newDown {
 			report.OutageCount++
 			outageStart = sc.ChangedAt
@@ -127,7 +127,7 @@ func ComputeSLA(changes []models.StateChange, currentStatus string, window time.
 	return report
 }
 
-func ComputeDailyBreakdown(changes []models.StateChange, currentStatus string, days int, now time.Time) []DayReport {
+func ComputeDailyBreakdown(changes []models.StateChange, currentStatus models.Status, days int, now time.Time) []DayReport {
 	reports := make([]DayReport, days)
 
 	for i := 0; i < days; i++ {
@@ -159,10 +159,6 @@ type DayReport struct {
 	UptimePct float64
 }
 
-func isDown(status string) bool {
-	return status == "DOWN" || status == "SSL EXP"
-}
-
 func filterChangesForWindow(changes []models.StateChange, start, end time.Time) []models.StateChange {
 	var filtered []models.StateChange
 	for _, sc := range changes {
@@ -180,7 +176,7 @@ func inferStatusAt(changes []models.StateChange, at time.Time) string {
 			return sc.ToStatus
 		}
 	}
-	return "UP"
+	return string(models.StatusUp)
 }
 
 func computeSLAForWindow(changes []models.StateChange, statusAtStart string, start, end time.Time) float64 {
@@ -193,7 +189,7 @@ func computeSLAForWindow(changes []models.StateChange, statusAtStart string, sta
 
 	var upTime, downTime time.Duration
 	cursor := start
-	wasDown := isDown(statusAtStart)
+	wasDown := models.Status(statusAtStart).IsBroken()
 
 	for _, sc := range sorted {
 		if sc.ChangedAt.Before(start) || !sc.ChangedAt.Before(end) {
@@ -205,7 +201,7 @@ func computeSLAForWindow(changes []models.StateChange, statusAtStart string, sta
 		} else {
 			upTime += seg
 		}
-		wasDown = isDown(sc.ToStatus)
+		wasDown = models.Status(sc.ToStatus).IsBroken()
 		cursor = sc.ChangedAt
 	}
 
diff --git a/internal/monitor/sla_test.go b/internal/monitor/sla_test.go
index 474971a..5edfe11 100644
--- a/internal/monitor/sla_test.go
+++ b/internal/monitor/sla_test.go
@@ -137,24 +137,24 @@ func TestComputeDailyBreakdown(t *testing.T) {
 	}
 }
 
-func TestIsDown(t *testing.T) {
-	if !isDown("DOWN") {
-		t.Error("DOWN should be down")
+func TestIsBroken(t *testing.T) {
+	if !models.StatusDown.IsBroken() {
+		t.Error("DOWN should be broken")
 	}
-	if !isDown("SSL EXP") {
-		t.Error("SSL EXP should be down")
+	if !models.StatusSSLExp.IsBroken() {
+		t.Error("SSL EXP should be broken")
 	}
-	if isDown("UP") {
-		t.Error("UP should not be down")
+	if models.StatusUp.IsBroken() {
+		t.Error("UP should not be broken")
 	}
-	if isDown("LATE") {
-		t.Error("LATE should not be down")
+	if models.StatusLate.IsBroken() {
+		t.Error("LATE should not be broken")
 	}
-	if isDown("STALE") {
-		t.Error("STALE should not be down")
+	if models.StatusStale.IsBroken() {
+		t.Error("STALE should not be broken")
 	}
-	if isDown("PENDING") {
-		t.Error("PENDING should not be down")
+	if models.StatusPending.IsBroken() {
+		t.Error("PENDING should not be broken")
 	}
 }
 
diff --git a/internal/server/server.go b/internal/server/server.go
index 6538e41..c8c3414 100644
--- a/internal/server/server.go
+++ b/internal/server/server.go
@@ -468,15 +468,15 @@ func Start(cfg ServerConfig, s store.Store, eng *monitor.Engine) *http.Server {
 			}
 			public := make(map[int]statusSite, len(state))
 			for id, site := range state {
-				status := site.Status
+				displayStatus := string(site.Status)
 				if allInMaint || maintSet[site.ID] || (site.ParentID > 0 && maintSet[site.ParentID]) {
-					status = "MAINT"
+					displayStatus = "MAINT"
 				}
 				public[id] = statusSite{
 					Name:      site.Name,
 					Type:      site.Type,
 					URL:       site.URL,
-					Status:    status,
+					Status:    displayStatus,
 					Paused:    site.Paused,
 					LastCheck: site.LastCheck,
 					Latency:   site.Latency,
@@ -569,10 +569,10 @@ func renderStatusPage(w http.ResponseWriter, title string, eng *monitor.Engine)
 
 	sort.Slice(sites, func(i, j int) bool {
 		if sites[i].Status != sites[j].Status {
-			if sites[i].Status == "DOWN" {
+			if sites[i].Status == models.StatusDown {
 				return true
 			}
-			if sites[j].Status == "DOWN" {
+			if sites[j].Status == models.StatusDown {
 				return false
 			}
 		}
diff --git a/internal/tui/format.go b/internal/tui/format.go
index 660ba10..591371a 100644
--- a/internal/tui/format.go
+++ b/internal/tui/format.go
@@ -143,16 +143,16 @@ func (m Model) fmtRetries(site models.Site) string {
 		dispCount = site.MaxRetries
 	}
 	s := fmt.Sprintf("%d/%d", dispCount, site.MaxRetries)
-	if site.Status == "DOWN" {
+	if site.Status == models.StatusDown {
 		return m.st.dangerStyle.Render(s)
 	}
-	if site.Status == "UP" && site.FailureCount > 0 {
+	if site.Status == models.StatusUp && site.FailureCount > 0 {
 		return m.st.warnStyle.Render(s)
 	}
 	return s
 }
 
-func (m Model) fmtStatus(status string, paused bool, inMaint bool) string {
+func (m Model) fmtStatus(status models.Status, paused bool, inMaint bool) string {
 	if paused {
 		return m.st.warnStyle.Render("◇ PAUSED")
 	}
@@ -160,18 +160,18 @@ func (m Model) fmtStatus(status string, paused bool, inMaint bool) string {
 		return m.st.maintStyle.Render("◼ MAINT")
 	}
 	switch status {
-	case "DOWN":
+	case models.StatusDown:
 		return m.st.dangerStyle.Render("▼ DOWN")
-	case "SSL EXP":
+	case models.StatusSSLExp:
 		return m.st.dangerStyle.Render("▼ SSL EXP")
-	case "LATE":
+	case models.StatusLate:
 		return m.st.warnStyle.Render("◆ LATE")
-	case "STALE":
+	case models.StatusStale:
 		return m.st.staleStyle.Render("◆ STALE")
-	case "PENDING":
+	case models.StatusPending:
 		return m.st.subtleStyle.Render("○ PENDING")
 	default:
-		return m.st.specialStyle.Render("▲ " + status)
+		return m.st.specialStyle.Render("▲ " + string(status))
 	}
 }
 
diff --git a/internal/tui/format_test.go b/internal/tui/format_test.go
index 9ee8d36..7c02778 100644
--- a/internal/tui/format_test.go
+++ b/internal/tui/format_test.go
@@ -56,19 +56,19 @@ func TestSiteOrder(t *testing.T) {
 
 func TestFmtStatus(t *testing.T) {
 	tests := []struct {
-		status  string
+		status  models.Status
 		paused  bool
 		inMaint bool
 		wantSub string
 	}{
-		{"DOWN", false, false, "▼ DOWN"},
-		{"UP", false, false, "▲ UP"},
-		{"SSL EXP", false, false, "▼ SSL EXP"},
-		{"LATE", false, false, "◆ LATE"},
-		{"STALE", false, false, "◆ STALE"},
-		{"PENDING", false, false, "○ PENDING"},
-		{"DOWN", true, false, "◇ PAUSED"},
-		{"DOWN", false, true, "◼ MAINT"},
+		{models.StatusDown, false, false, "▼ DOWN"},
+		{models.StatusUp, false, false, "▲ UP"},
+		{models.StatusSSLExp, false, false, "▼ SSL EXP"},
+		{models.StatusLate, false, false, "◆ LATE"},
+		{models.StatusStale, false, false, "◆ STALE"},
+		{models.StatusPending, false, false, "○ PENDING"},
+		{models.StatusDown, true, false, "◇ PAUSED"},
+		{models.StatusDown, false, true, "◼ MAINT"},
 	}
 	for _, tt := range tests {
 		got := styledModel.fmtStatus(tt.status, tt.paused, tt.inMaint)
diff --git a/internal/tui/tab_sites.go b/internal/tui/tab_sites.go
index 6c970ee..c84a270 100644
--- a/internal/tui/tab_sites.go
+++ b/internal/tui/tab_sites.go
@@ -240,7 +240,7 @@ func (m Model) viewSitesTab() string {
 					name = limitStr(name, nameW-2)
 				}
 
-				if (site.Status == "DOWN" || site.Status == "SSL EXP" || site.Status == "LATE" || site.Status == "STALE") && site.LastError != "" {
+				if (site.Status == models.StatusDown || site.Status == models.StatusSSLExp || site.Status == models.StatusLate || site.Status == models.StatusStale) && site.LastError != "" {
 					nameLen := len([]rune(name))
 					errSpace := nameW - nameLen - 3
 					if errSpace > 10 {
diff --git a/internal/tui/update.go b/internal/tui/update.go
index b855a9f..63f019b 100644
--- a/internal/tui/update.go
+++ b/internal/tui/update.go
@@ -455,7 +455,7 @@ func (m *Model) handleSLAData(msg slaDataMsg) (tea.Model, tea.Cmd) {
 	}
 	period := slaPeriods[msg.periodIdx]
 
-	var currentStatus string
+	var currentStatus models.Status
 	for _, s := range m.sites {
 		if s.ID == msg.siteID {
 			currentStatus = s.Status
diff --git a/internal/tui/view_dashboard.go b/internal/tui/view_dashboard.go
index 18fd814..4335dad 100644
--- a/internal/tui/view_dashboard.go
+++ b/internal/tui/view_dashboard.go
@@ -6,6 +6,7 @@ import (
 	"strings"
 	"time"
 
+	"gitea.lerkolabs.com/lerkolabs/uptop/internal/models"
 	"github.com/charmbracelet/lipgloss"
 )
 
@@ -16,7 +17,7 @@ func sinApprox(x float64) float64 {
 func (m Model) pulseIndicator() string {
 	hasDown := false
 	for _, s := range m.sites {
-		if !s.Paused && !m.isMonitorInMaintenance(s.ID) && (s.Status == "DOWN" || s.Status == "SSL EXP") {
+		if !s.Paused && !m.isMonitorInMaintenance(s.ID) && (s.Status == models.StatusDown || s.Status == models.StatusSSLExp) {
 			hasDown = true
 			break
 		}
@@ -127,9 +128,9 @@ func (m Model) computeStats() dashboardStats {
 			continue
 		}
 		switch site.Status {
-		case "DOWN", "SSL EXP":
+		case models.StatusDown, models.StatusSSLExp:
 			s.downCount++
-		case "LATE":
+		case models.StatusLate:
 			s.lateCount++
 		}
 	}
diff --git a/internal/tui/view_detail.go b/internal/tui/view_detail.go
index 44c9abf..081fd40 100644
--- a/internal/tui/view_detail.go
+++ b/internal/tui/view_detail.go
@@ -45,7 +45,7 @@ func (m Model) viewDetailPanel() string {
 
 	row("Status", m.fmtStatus(site.Status, site.Paused, m.isMonitorInMaintenance(site.ID)))
 
-	if (site.Status == "DOWN" || site.Status == "SSL EXP" || site.Status == "LATE" || site.Status == "STALE") && site.LastError != "" {
+	if (site.Status == models.StatusDown || site.Status == models.StatusSSLExp || site.Status == models.StatusLate || site.Status == models.StatusStale) && site.LastError != "" {
 		errWidth := m.termWidth - chromePadH - 19
 		if errWidth < 30 {
 			errWidth = 30
@@ -58,7 +58,7 @@ func (m Model) viewDetailPanel() string {
 		row("HTTP Code", strconv.Itoa(site.StatusCode))
 	}
 
-	if (site.Status == "DOWN" || site.Status == "SSL EXP") && site.LastError != "" {
+	if (site.Status == models.StatusDown || site.Status == models.StatusSSLExp) && site.LastError != "" {
 		chain := connectionChain(site.LastError, site.Type, site.StatusCode, strings.HasPrefix(site.URL, "https"))
 		if len(chain) > 0 {
 			b.WriteString("\n")
@@ -189,7 +189,7 @@ func (m Model) viewDetailPanel() string {
 		for i, sc := range stateChanges {
 			ago := fmtDuration(time.Since(sc.ChangedAt))
 			arrow := m.st.subtleStyle.Render(sc.FromStatus) + " → "
-			if sc.ToStatus == "UP" {
+			if sc.ToStatus == string(models.StatusUp) {
 				arrow += m.st.specialStyle.Render(sc.ToStatus)
 			} else {
 				arrow += m.st.dangerStyle.Render(sc.ToStatus)
@@ -198,7 +198,7 @@ func (m Model) viewDetailPanel() string {
 			if dur := computeOutageDuration(stateChanges, i); dur > 0 {
 				line += "  " + m.st.warnStyle.Render("outage "+fmtDuration(dur))
 			}
-			if sc.ErrorReason != "" && sc.ToStatus != "UP" {
+			if sc.ErrorReason != "" && sc.ToStatus != string(models.StatusUp) {
 				line += "  " + m.st.dangerStyle.Render(sc.ErrorReason)
 			}
 			b.WriteString(line + "\n")
diff --git a/internal/tui/view_history.go b/internal/tui/view_history.go
index f61d7d6..9efddcb 100644
--- a/internal/tui/view_history.go
+++ b/internal/tui/view_history.go
@@ -17,14 +17,14 @@ type historyStats struct {
 
 func computeOutageDuration(changes []models.StateChange, idx int) time.Duration {
 	sc := changes[idx]
-	if sc.ToStatus != "UP" {
+	if sc.ToStatus != string(models.StatusUp) {
 		return 0
 	}
 	if idx+1 >= len(changes) {
 		return 0
 	}
 	prev := changes[idx+1]
-	if prev.ToStatus == "UP" {
+	if prev.ToStatus == string(models.StatusUp) {
 		return 0
 	}
 	dur := sc.ChangedAt.Sub(prev.ChangedAt)
@@ -122,11 +122,11 @@ func (m Model) buildHistoryContent() string {
 
 		arrow := m.st.subtleStyle.Render(sc.FromStatus) + " → "
 		switch sc.ToStatus {
-		case "UP":
+		case string(models.StatusUp):
 			arrow += m.st.specialStyle.Render(sc.ToStatus)
-		case "LATE":
+		case string(models.StatusLate):
 			arrow += m.st.warnStyle.Render(sc.ToStatus)
-		case "STALE":
+		case string(models.StatusStale):
 			arrow += m.st.staleStyle.Render(sc.ToStatus)
 		default:
 			arrow += m.st.dangerStyle.Render(sc.ToStatus)
@@ -138,7 +138,7 @@ func (m Model) buildHistoryContent() string {
 		}
 
 		reason := ""
-		if sc.ErrorReason != "" && sc.ToStatus != "UP" {
+		if sc.ErrorReason != "" && sc.ToStatus != string(models.StatusUp) {
 			reason = m.st.dangerStyle.Render(limitStr(sc.ErrorReason, reasonWidth))
 		}