feat: proper push monitor lifecycle — PENDING, LATE, DOWN states

Push monitors no longer lie about status:

- PENDING stays until first heartbeat (no auto-promote to UP)
- LATE state (amber) when overdue but within grace period
- DOWN only after grace period expires
- Grace period = interval/2, minimum 60s

RecordHeartbeat now handles all transitions:
- PENDING → UP (first heartbeat, logged)
- LATE → UP (late arrival, logged)
- DOWN → UP (recovery, alert + state change persisted)

TUI updates:
- LATE rendered in amber/warning color
- Status bar shows LATE count separately
- Tab badge shows ⚠ for late monitors
- Sort order: DOWN > LATE > UP > PENDING > PAUSED
- Detail panel shows error for LATE monitors

Inspired by Healthchecks.io state machine (new/up/grace/down).

internal/monitor/monitor.go

@@ -19,8 +19,8 @@ import (
 const (
 	maxLogEntries    = 100
 	pollInterval     = 5 * time.Second
-	pushGracePeriod  = 5 * time.Second
 	minCheckInterval = 5
+	minPushGrace     = 60 * time.Second
 )
 
 type Engine struct {
@@ -186,17 +186,34 @@ func (e *Engine) RecordHeartbeat(token string) bool {
 		return false
 	}
 
+	prevStatus := site.Status
 	site.LastCheck = time.Now()
-	wasDown := site.Status == "DOWN"
 	site.Status = "UP"
 	site.FailureCount = 0
 	site.Latency = 0
+	site.LastError = ""
+	site.LastSuccessAt = time.Now()
+
+	if prevStatus != "UP" {
+		site.StatusChangedAt = time.Now()
+	}
+
 	e.liveState[targetID] = site
 
-	if wasDown {
+	switch prevStatus {
+	case "PENDING":
+		e.AddLog(fmt.Sprintf("Push Monitor '%s' received first heartbeat", site.Name))
+	case "LATE":
+		e.AddLog(fmt.Sprintf("Push Monitor '%s' heartbeat arrived (was late)", site.Name))
+	case "DOWN":
 		e.AddLog(fmt.Sprintf("Push Monitor '%s' recovered", site.Name))
-		e.triggerAlert(site.AlertID, "✅ RECOVERY", fmt.Sprintf("Push Monitor '%s' is receiving heartbeats.", site.Name))
+		go e.triggerAlert(site.AlertID, "✅ RECOVERY", fmt.Sprintf("Push Monitor '%s' is receiving heartbeats.", site.Name))
 	}
+
+	if prevStatus != "UP" && prevStatus != "PENDING" {
+		go func() { _ = e.db.SaveStateChange(targetID, prevStatus, "UP", "") }()
+	}
+
 	return true
 }
 
@@ -241,9 +258,6 @@ func (e *Engine) Start(ctx context.Context) {
 				if !exists {
 					e.mu.Lock()
 					s.Status = "PENDING"
-					if s.Type == "push" {
-						s.LastCheck = time.Now()
-					}
 					if h, ok := e.GetHistory(s.ID); ok && len(h.Statuses) > 0 {
 						if h.Statuses[len(h.Statuses)-1] {
 							s.Status = "UP"
@@ -401,11 +415,28 @@ func (e *Engine) checkByID(id int) {
 }
 
 func (e *Engine) checkPush(site models.Site) {
-	deadline := site.LastCheck.Add(time.Duration(site.Interval) * time.Second).Add(pushGracePeriod)
+	if site.Status == "PENDING" {
-	if time.Now().After(deadline) {
+		return
-		e.handleStatusChange(site, "DOWN", 0, 0, "heartbeat missed")
+	}
-	} else if site.Status != "UP" {
+
-		e.handleStatusChange(site, "UP", 200, 0, "")
+	interval := time.Duration(site.Interval) * time.Second
+	grace := interval / 2
+	if grace < minPushGrace {
+		grace = minPushGrace
+	}
+
+	overdue := site.LastCheck.Add(interval)
+	graceEnd := overdue.Add(grace)
+	now := time.Now()
+
+	if now.After(graceEnd) {
+		if site.Status != "DOWN" {
+			e.handleStatusChange(site, "DOWN", 0, 0, "heartbeat missed")
+		}
+	} else if now.After(overdue) {
+		if site.Status != "LATE" {
+			e.handleStatusChange(site, "LATE", 0, 0, "heartbeat overdue")
+		}
 	}
 }
 

internal/monitor/monitor_test.go

@@ -537,7 +537,7 @@ func TestCheckPush_DeadlineMissed(t *testing.T) {
 	site := models.Site{
 		ID: 1, Name: "push", Type: "push", Status: "UP",
 		Interval: 10, MaxRetries: 0,
-		LastCheck: time.Now().Add(-20 * time.Second),
+		LastCheck: time.Now().Add(-120 * time.Second),
 	}
 	injectSite(e, site)
 
@@ -549,6 +549,24 @@ func TestCheckPush_DeadlineMissed(t *testing.T) {
 	}
 }
 
+func TestCheckPush_OverdueBecomesLate(t *testing.T) {
+	ms := newMockStore()
+	e := newTestEngine(ms)
+	site := models.Site{
+		ID: 1, Name: "push", Type: "push", Status: "UP",
+		Interval:  300,
+		LastCheck: time.Now().Add(-310 * time.Second),
+	}
+	injectSite(e, site)
+
+	e.checkPush(site)
+
+	s, _ := getSite(e, 1)
+	if s.Status != "LATE" {
+		t.Errorf("expected LATE when overdue but within grace, got %s", s.Status)
+	}
+}
+
 func TestCheckPush_WithinDeadline(t *testing.T) {
 	ms := newMockStore()
 	e := newTestEngine(ms)
@@ -566,20 +584,20 @@ func TestCheckPush_WithinDeadline(t *testing.T) {
 	}
 }
 
-func TestCheckPush_PendingToUp(t *testing.T) {
+func TestCheckPush_PendingStaysPending(t *testing.T) {
 	ms := newMockStore()
 	e := newTestEngine(ms)
 	site := models.Site{
 		ID: 1, Name: "push", Type: "push", Status: "PENDING",
-		Interval: 60, LastCheck: time.Now(),
+		Interval: 60,
 	}
 	injectSite(e, site)
 
 	e.checkPush(site)
 
 	s, _ := getSite(e, 1)
-	if s.Status != "UP" {
+	if s.Status != "PENDING" {
-		t.Errorf("expected UP, got %s", s.Status)
+		t.Errorf("expected PENDING to stay until first heartbeat, got %s", s.Status)
 	}
 }
 

internal/server/server.go

@@ -67,6 +67,7 @@ var statusTpl = template.Must(template.New("status").Parse(`
 		.UP { background: #9ece6a; color: #1a1b26; }
 		.DOWN { background: #f7768e; color: #1a1b26; }
 		.PENDING { background: #e0af68; color: #1a1b26; }
+		.LATE { background: #e0af68; color: #1a1b26; }
 		.SSL-EXP { background: #e0af68; color: #1a1b26; }
 		.PAUSED { background: #565f89; color: #c0caf5; }
 		.MAINT { background: #bb9af7; color: #1a1b26; }

internal/tui/tab_sites.go

@@ -302,6 +302,8 @@ func fmtStatus(status string, paused bool, inMaint bool) string {
 	switch status {
 	case "DOWN", "SSL EXP":
 		return dangerStyle.Render(status)
+	case "LATE":
+		return warnStyle.Render(status)
 	case "PENDING":
 		return subtleStyle.Render(status)
 	default:
@@ -412,7 +414,7 @@ func (m Model) viewSitesTab() string {
 					name = limitStr(name, nameW)
 				}
 
-				if (site.Status == "DOWN" || site.Status == "SSL EXP") && site.LastError != "" {
+				if (site.Status == "DOWN" || site.Status == "SSL EXP" || site.Status == "LATE") && site.LastError != "" {
 					nameLen := len([]rune(name))
 					errSpace := nameW - nameLen - 1
 					if errSpace > 10 {
@@ -764,7 +766,7 @@ func (m Model) viewDetailPanel() string {
 
 	row("Status", fmtStatus(site.Status, site.Paused, m.isMonitorInMaintenance(site.ID)))
 
-	if (site.Status == "DOWN" || site.Status == "SSL EXP") && site.LastError != "" {
+	if (site.Status == "DOWN" || site.Status == "SSL EXP" || site.Status == "LATE") && site.LastError != "" {
 		row("Error", dangerStyle.Render(limitStr(site.LastError, 60)))
 	}
 

internal/tui/tui.go

@@ -811,13 +811,20 @@ func (m Model) viewDashboard() string {
 	allSites := m.engine.GetAllSites()
 	totalMonitors := 0
 	downCount := 0
+	lateCount := 0
 	for _, s := range allSites {
 		if s.Type == "group" {
 			continue
 		}
 		totalMonitors++
-		if !s.Paused && !m.isMonitorInMaintenance(s.ID) && (s.Status == "DOWN" || s.Status == "SSL EXP") {
+		if s.Paused || m.isMonitorInMaintenance(s.ID) {
+			continue
+		}
+		switch s.Status {
+		case "DOWN", "SSL EXP":
 			downCount++
+		case "LATE":
+			lateCount++
 		}
 	}
 	offlineNodes := 0
@@ -830,6 +837,8 @@ func (m Model) viewDashboard() string {
 	var sitesLabel string
 	if downCount > 0 {
 		sitesLabel = fmt.Sprintf("Sites (%d↓)", downCount)
+	} else if lateCount > 0 {
+		sitesLabel = fmt.Sprintf("Sites (%d⚠)", lateCount)
 	} else if totalMonitors > 0 {
 		sitesLabel = fmt.Sprintf("Sites (%d)", totalMonitors)
 	} else {
@@ -895,14 +904,19 @@ func (m Model) viewDashboard() string {
 		}
 	}
 
-	upCount := totalMonitors - downCount
+	upCount := totalMonitors - downCount - lateCount
 	var upStr string
 	if downCount > 0 {
 		upStr = dangerStyle.Render(fmt.Sprintf("%d/%d UP", upCount, totalMonitors))
+	} else if lateCount > 0 {
+		upStr = warnStyle.Render(fmt.Sprintf("%d/%d UP", upCount, totalMonitors))
 	} else {
 		upStr = specialStyle.Render(fmt.Sprintf("%d/%d UP", upCount, totalMonitors))
 	}
 	statusParts := []string{upStr}
+	if lateCount > 0 {
+		statusParts = append(statusParts, warnStyle.Render(fmt.Sprintf("%d LATE", lateCount)))
+	}
 	if len(m.nodes) > 0 {
 		online := 0
 		for _, n := range m.nodes {
@@ -949,10 +963,12 @@ func siteOrder(s models.Site) int {
 	switch s.Status {
 	case "DOWN", "SSL EXP":
 		return 0
-	case "PENDING":
+	case "LATE":
-		return 2
-	default:
 		return 1
+	case "PENDING":
+		return 3
+	default:
+		return 2
 	}
 }