diff --git a/internal/pipeline/monitor_rules.go b/internal/pipeline/monitor_rules.go
new file mode 100644
index 0000000..da708ae
--- /dev/null
+++ b/internal/pipeline/monitor_rules.go
@@ -0,0 +1,16 @@
+package pipeline
+
+func candidateInMonitor(policy Policy, candidate Candidate) bool {
+	start := policy.MonitorStartHz
+	end := policy.MonitorEndHz
+	if start == 0 || end == 0 || end <= start {
+		return true
+	}
+	left := candidate.CenterHz
+	right := candidate.CenterHz
+	if candidate.BandwidthHz > 0 {
+		left = candidate.CenterHz - candidate.BandwidthHz/2
+		right = candidate.CenterHz + candidate.BandwidthHz/2
+	}
+	return right >= start && left <= end
+}
diff --git a/internal/pipeline/phases.go b/internal/pipeline/phases.go
index b9a2f0a..5da17b2 100644
--- a/internal/pipeline/phases.go
+++ b/internal/pipeline/phases.go
@@ -27,6 +27,7 @@ type RefinementPlan struct {
 	TotalCandidates   int                  `json:"total_candidates"`
 	MinCandidateSNRDb float64              `json:"min_candidate_snr_db"`
 	Budget            int                  `json:"budget"`
+	DroppedByMonitor  int                  `json:"dropped_by_monitor"`
 	DroppedBySNR      int                  `json:"dropped_by_snr"`
 	DroppedByBudget   int                  `json:"dropped_by_budget"`
 	Selected          []ScheduledCandidate `json:"selected,omitempty"`
diff --git a/internal/pipeline/scheduler.go b/internal/pipeline/scheduler.go
index 9fbee14..4b5c7aa 100644
--- a/internal/pipeline/scheduler.go
+++ b/internal/pipeline/scheduler.go
@@ -26,6 +26,10 @@ func BuildRefinementPlan(candidates []Candidate, policy Policy) RefinementPlan {
 	snrWeight, bwWeight, peakWeight := refinementIntentWeights(policy.Intent)
 	scored := make([]ScheduledCandidate, 0, len(candidates))
 	for _, c := range candidates {
+		if !candidateInMonitor(policy, c) {
+			plan.DroppedByMonitor++
+			continue
+		}
 		if c.SNRDb < policy.MinCandidateSNRDb {
 			plan.DroppedBySNR++
 			continue
diff --git a/internal/pipeline/scheduler_test.go b/internal/pipeline/scheduler_test.go
index f98095b..497ad74 100644
--- a/internal/pipeline/scheduler_test.go
+++ b/internal/pipeline/scheduler_test.go
@@ -60,6 +60,23 @@ func TestBuildRefinementPlanRespectsMaxConcurrent(t *testing.T) {
 	}
 }
 
+func TestBuildRefinementPlanAppliesMonitorSpan(t *testing.T) {
+	policy := Policy{MaxRefinementJobs: 5, MinCandidateSNRDb: 0, MonitorStartHz: 150, MonitorEndHz: 350}
+	cands := []Candidate{
+		{ID: 1, CenterHz: 100, BandwidthHz: 20},
+		{ID: 2, CenterHz: 200, BandwidthHz: 50},
+		{ID: 3, CenterHz: 300, BandwidthHz: 100},
+		{ID: 4, CenterHz: 500, BandwidthHz: 50},
+	}
+	plan := BuildRefinementPlan(cands, policy)
+	if plan.DroppedByMonitor != 2 {
+		t.Fatalf("expected 2 dropped by monitor, got %d", plan.DroppedByMonitor)
+	}
+	if len(plan.Selected) != 2 {
+		t.Fatalf("expected 2 selected within monitor, got %d", len(plan.Selected))
+	}
+}
+
 func TestAutoSpanForHint(t *testing.T) {
 	span, source := AutoSpanForHint("WFM_STEREO")
 	if span < 150000 || source == "" {