diff --git a/internal/unifiedresources/pbs_target_continuity_test.go b/internal/unifiedresources/pbs_target_continuity_test.go
new file mode 100644
index 0000000000..b7b20ff840
--- /dev/null
+++ b/internal/unifiedresources/pbs_target_continuity_test.go
@@ -0,0 +1,146 @@
+package unifiedresources
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+	"time"
+
+	"github.com/rcourtman/pulse-go-rewrite/internal/models"
+)
+
+// Exercise the producer side of PBS History (#1723): monitor generation
+// replacement, uncached/cached target lookup, and API-style unified reseeding.
+// Display labels, datastore order and source freshness are not metric IDs.
+func TestPBSTargetContinuityAcrossSnapshotGenerations(t *testing.T) {
+	for _, shape := range []string{"pbs-only", "pbs-agent", "side-by-side"} {
+		t.Run(shape, func(t *testing.T) {
+			adapter := NewMonitorAdapter(NewRegistry(nil))
+			var baseline map[string]MetricsTarget
+			for generation := 0; generation < 8; generation++ {
+				snapshot := pbsTargetSnapshot(shape)
+				if generation%2 != 0 {
+					ds := snapshot.PBSInstances[0].Datastores
+					ds[0], ds[1] = ds[1], ds[0]
+					if len(snapshot.Hosts) > 0 {
+						snapshot.Hosts[0].DisplayName = "Backup host label"
+					}
+				}
+				if generation%3 == 2 {
+					snapshot.PBSInstances[0].Status = "offline"
+					snapshot.PBSInstances[0].LastSeen = time.Now().Add(-time.Hour)
+					for i := range snapshot.Hosts {
+						snapshot.Hosts[i].LastSeen = time.Now().Add(-time.Hour)
+					}
+				}
+				adapter.replaceRegistry(snapshot, nil)
+				registry := adapter.currentRegistry()
+				targets := pbsTargetCoordinates(t, registry)
+				if baseline == nil {
+					baseline = targets
+				} else if !reflect.DeepEqual(targets, baseline) {
+					t.Fatalf("generation %d changed IDs/targets: got %v, want %v", generation, targets, baseline)
+				}
+				// Typed views build the inverse source index used by subsequent
+				// metrics-target lookups. It must agree with the uncached scan.
+				registry.Hosts()
+				if got := pbsTargetCoordinates(t, registry); !reflect.DeepEqual(got, targets) {
+					t.Fatalf("cached targets differ: got %v, want %v", got, targets)
+				}
+				rehydrated := NewRegistry(nil)
+				rehydrated.IngestResources(registry.List())
+				if got := pbsTargetCoordinates(t, rehydrated); !reflect.DeepEqual(got, targets) {
+					t.Fatalf("reseeded targets differ: got %v, want %v", got, targets)
+				}
+			}
+			t.Logf("8 generations retain %d canonical IDs and exact targets", len(baseline))
+		})
+	}
+}
+
+// A missing or replaced agent must not keep advertising its old target. The
+// independently observed PBS service retains its own history coordinates.
+func TestPBSTargetContinuityAgentRemovalAndReplacement(t *testing.T) {
+	adapter := NewMonitorAdapter(NewRegistry(nil))
+	for _, agentID := range []string{"agent-uuid-a", "", "agent-uuid-b", "agent-uuid-a"} {
+		snapshot := pbsTargetSnapshot("pbs-agent")
+		if agentID == "" {
+			snapshot.Hosts = nil
+		} else {
+			snapshot.Hosts[0].ID = agentID
+		}
+		adapter.replaceRegistry(snapshot, nil)
+		registry := adapter.currentRegistry()
+		pbsTargetCoordinates(t, registry)
+		var agents int
+		for _, resource := range registry.List() {
+			if resource.Type == ResourceTypeAgent {
+				agents++
+				target := registry.MetricsTarget(resource.ID)
+				if target == nil || target.ResourceID != agentID {
+					t.Fatalf("agent %q advertises stale/missing target: %+v", agentID, target)
+				}
+			}
+		}
+		want := 1
+		if agentID == "" {
+			want = 0
+		}
+		if agents != want {
+			t.Fatalf("agent %q: got %d host resources, want %d", agentID, agents, want)
+		}
+	}
+}
+
+func pbsTargetSnapshot(shape string) models.StateSnapshot {
+	now := time.Now().UTC()
+	snapshot := models.StateSnapshot{
+		PBSInstances: []models.PBSInstance{{
+			ID: "pbs-backup", Name: "backup", Host: "https://backup.example.invalid:8007",
+			Status: "online", LastSeen: now,
+			Datastores: []models.PBSDatastore{{Name: "fast", Total: 1000, Used: 200}, {Name: "archive", Total: 2000, Used: 300}},
+		}},
+	}
+	if shape != "pbs-only" {
+		snapshot.Hosts = []models.Host{{ID: "agent-uuid-a", Hostname: "backup", MachineID: "machine-a", LastSeen: now}}
+	}
+	if shape == "side-by-side" {
+		snapshot.Nodes = []models.Node{{ID: "pve/backup", Name: "backup", Instance: "pve", LinkedAgentID: "agent-uuid-a", LastSeen: now}}
+		snapshot.Hosts[0].LinkedNodeID = "pve/backup"
+	}
+	return snapshot
+}
+
+func pbsTargetCoordinates(t *testing.T, registry *ResourceRegistry) map[string]MetricsTarget {
+	t.Helper()
+	targets := make(map[string]MetricsTarget)
+	var services, datastores int
+	for _, resource := range registry.List() {
+		target := registry.MetricsTarget(resource.ID)
+		if target == nil {
+			t.Fatalf("resource %s (%s) lost its metrics target", resource.ID, resource.Type)
+		}
+		targets[resource.ID] = *target
+		switch resource.Type {
+		case ResourceTypePBS:
+			services++
+			if *target != (MetricsTarget{ResourceType: "agent", ResourceID: "pbs-backup"}) {
+				t.Fatalf("PBS target = %+v", target)
+			}
+		case ResourceTypeStorage:
+			datastores++
+			want := MetricsTarget{ResourceType: "storage", ResourceID: fmt.Sprintf("pbs-backup/%s", resource.Name)}
+			if *target != want {
+				t.Fatalf("datastore target = %+v, want %+v", target, want)
+			}
+		case ResourceTypeAgent:
+			if resource.Agent == nil || *target != (MetricsTarget{ResourceType: "agent", ResourceID: resource.Agent.AgentID}) {
+				t.Fatalf("host target disagrees with agent identity: %+v", target)
+			}
+		}
+	}
+	if services != 1 || datastores != 2 {
+		t.Fatalf("got %d PBS services, %d datastores", services, datastores)
+	}
+	return targets
+}