diff --git a/main.go b/main.go
index 0d69d91..7826ebb 100644
--- a/main.go
+++ b/main.go
@@ -23,21 +23,21 @@ var (
 			Foreground(lipgloss.Color("#00d4ff")).
 			Padding(0, 1)
 
-	statusRunning   = lipgloss.NewStyle().Foreground(lipgloss.Color("#00ff88")).SetString("● running")
-	statusIdle      = lipgloss.NewStyle().Foreground(lipgloss.Color("#888888")).SetString("○ idle")
-	statusBlocked   = lipgloss.NewStyle().Foreground(lipgloss.Color("#ffaa00")).SetString("⚠ blocked")
-	statusError     = lipgloss.NewStyle().Foreground(lipgloss.Color("#ff4444")).SetString("✕ error")
-	statusClosed    = lipgloss.NewStyle().Foreground(lipgloss.Color("#555555")).SetString("✗ closed")
-	statusLost      = lipgloss.NewStyle().Foreground(lipgloss.Color("#773333")).SetString("✗ lost")
-	subagentMark    = lipgloss.NewStyle().Foreground(lipgloss.Color("#55aaff")).SetString("◇")
+	statusRunning = lipgloss.NewStyle().Foreground(lipgloss.Color("#00ff88")).SetString("● running")
+	statusIdle    = lipgloss.NewStyle().Foreground(lipgloss.Color("#888888")).SetString("○ idle")
+	statusBlocked = lipgloss.NewStyle().Foreground(lipgloss.Color("#ffaa00")).SetString("⚠ blocked")
+	statusError   = lipgloss.NewStyle().Foreground(lipgloss.Color("#ff4444")).SetString("✕ error")
+	statusClosed  = lipgloss.NewStyle().Foreground(lipgloss.Color("#555555")).SetString("✗ closed")
+	statusLost    = lipgloss.NewStyle().Foreground(lipgloss.Color("#773333")).SetString("✗ lost")
+	subagentMark  = lipgloss.NewStyle().Foreground(lipgloss.Color("#55aaff")).SetString("◇")
 
 	detailKeyStyle   = lipgloss.NewStyle().Foreground(lipgloss.Color("#00d4ff")).Bold(true)
 	detailLabelStyle = lipgloss.NewStyle().Foreground(lipgloss.Color("#aaaaaa"))
 	detailValStyle   = lipgloss.NewStyle().Foreground(lipgloss.Color("#dddddd"))
 	detailBoxStyle   = lipgloss.NewStyle().
-			Border(lipgloss.RoundedBorder()).
-			BorderForeground(lipgloss.Color("240")).
-			Padding(0, 1)
+				Border(lipgloss.RoundedBorder()).
+				BorderForeground(lipgloss.Color("240")).
+				Padding(0, 1)
 
 	infoStyle = lipgloss.NewStyle().
 			Foreground(lipgloss.Color("#aaaaaa")).
@@ -50,10 +50,10 @@ var (
 
 // Sort modes
 const (
-	sortSmart = iota // live first, running first, then last activity
-	sortActivity     // most recent activity first
-	sortStarted      // most recently started first
-	sortFolder       // folder name A-Z
+	sortSmart    = iota // live first, running first, then last activity
+	sortActivity        // most recent activity first
+	sortStarted         // most recently started first
+	sortFolder          // folder name A-Z
 )
 
 var sortNames = map[int]string{
@@ -795,8 +795,7 @@ Config: ~/.config/pi-dashboard.yaml
   remote:
     - host: 192.168.20.13
       user: sam
-      path: /home/sam/.pi/agent/dashboard/
-`)
+      path: /home/sam/.pi/agent/dashboard/`)
 			return
 		case "--list":
 			cfg := defaultConfig()
diff --git a/main_test.go b/main_test.go
new file mode 100644
index 0000000..136f766
--- /dev/null
+++ b/main_test.go
@@ -0,0 +1,120 @@
+package main
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+)
+
+// Simulates the remote `cat *.json` output: several pretty-printed,
+// multi-line JSON objects concatenated together.
+func TestReadRemoteStream(t *testing.T) {
+	var sb strings.Builder
+	for _, name := range []string{"alpha", "beta"} {
+		s := AgentState{
+			Session:      name,
+			Machine:      "test",
+			Cwd:          "/home/sam/proj/" + name,
+			AgentStatus:  "idle",
+			SessionState: "open",
+			LastSeenAt:   strptr(time.Now().UTC().Format(time.RFC3339)),
+		}
+		b, _ := json.MarshalIndent(s, "", "  ")
+		sb.Write(b)
+		sb.WriteString("\n")
+	}
+
+	dec := json.NewDecoder(strings.NewReader(sb.String()))
+	var states []AgentState
+	for {
+		var s AgentState
+		if err := dec.Decode(&s); err != nil {
+			break
+		}
+		states = append(states, s)
+	}
+	if len(states) != 2 {
+		t.Fatalf("expected 2 states, got %d", len(states))
+	}
+	if states[1].Session != "beta" {
+		t.Fatalf("expected beta second, got %s", states[1].Session)
+	}
+}
+
+// A legacy state file (no heartbeat) should use file mtime as liveness.
+func TestLegacyMtimeFallback(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "legacy.json")
+	legacy := `{"session":"legacy","status":"running"}`
+	os.WriteFile(path, []byte(legacy), 0644)
+
+	s, err := readStateFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if s.LastSeenAt == nil || *s.LastSeenAt == "" {
+		t.Fatal("expected mtime fallback to fill LastSeenAt")
+	}
+	if s.IsClosed(time.Hour) {
+		t.Fatal("fresh file should not be closed")
+	}
+}
+
+// Stale heartbeat => closed, regardless of graceful state.
+func TestStaleness(t *testing.T) {
+	old := time.Now().UTC().Add(-10 * time.Minute).Format(time.RFC3339)
+	fresh := time.Now().UTC().Format(time.RFC3339)
+
+	stale := AgentState{SessionState: "open", LastSeenAt: &old}
+	if !stale.IsClosed(45 * time.Second) {
+		t.Fatal("old heartbeat should be closed")
+	}
+	if !stale.WasKilled(45 * time.Second) {
+		t.Fatal("no closed_at + stale => killed")
+	}
+
+	graceful := AgentState{SessionState: "closed", ClosedAt: &old}
+	if !graceful.IsClosed(45 * time.Second) {
+		t.Fatal("closed state should be closed")
+	}
+	if graceful.WasKilled(45 * time.Second) {
+		t.Fatal("graceful close should not be killed")
+	}
+
+	alive := AgentState{SessionState: "open", LastSeenAt: &fresh}
+	if alive.IsClosed(45 * time.Second) {
+		t.Fatal("fresh heartbeat should be live")
+	}
+}
+
+// Sorting: live first, running before idle, then by activity.
+func TestSortSmart(t *testing.T) {
+	now := time.Now().UTC()
+	mk := func(name, status string, age time.Duration) AgentState {
+		t := now.Add(-age).Format(time.RFC3339)
+		return AgentState{Session: name, AgentStatus: status, SessionState: "open", LastSeenAt: &t}
+	}
+	agents := []AgentState{
+		mk("old-idle", "idle", 30*time.Minute),
+		mk("fresh-running", "running", time.Minute),
+		mk("old-closed", "idle", 10*time.Hour),
+		mk("fresh-idle", "idle", 2*time.Minute),
+	}
+	sortAgents(agents, sortSmart, 45*time.Second)
+
+	got := []string{}
+	for _, a := range agents {
+		got = append(got, a.Session)
+	}
+	want := []string{"fresh-running", "fresh-idle", "old-idle", "old-closed"}
+	for i := range want {
+		if got[i] != want[i] {
+			t.Fatalf("sort mismatch at %d: got %v want %v", i, got, want)
+		}
+	}
+}
+
+func strptr(s string) *string { return &s }