diff --git a/README.md b/README.md
index 969d64e..9a7c920 100644
--- a/README.md
+++ b/README.md
@@ -71,6 +71,7 @@ Edit `config.yaml` (autosave goes to `config.autosave.yaml`).
 - `refinement.max_concurrent` — refinement budget hint
 - `refinement.min_candidate_snr_db` — floor for future scheduling decisions
 - `refinement.min_span_hz` / `refinement.max_span_hz` — clamp refinement window span (0 = no clamp)
+- `refinement.auto_span` — use mod-type heuristics when candidate bandwidth is missing/odd
 - `resources.prefer_gpu` — GPU preference hint
 - `resources.max_refinement_jobs` — processing budget hint
 - `resources.max_recording_streams` — recording/streaming budget hint
diff --git a/cmd/sdrd/pipeline_runtime.go b/cmd/sdrd/pipeline_runtime.go
index 961c02e..f38a0d3 100644
--- a/cmd/sdrd/pipeline_runtime.go
+++ b/cmd/sdrd/pipeline_runtime.go
@@ -239,16 +239,27 @@ func (rt *dspRuntime) buildRefinementInput(surv pipeline.SurveillanceResult) pip
 	windows := make([]pipeline.RefinementWindow, 0, len(scheduled))
 	for _, sc := range scheduled {
 		span := sc.Candidate.BandwidthHz
+		windowSource := "candidate"
+		if policy.RefinementAutoSpan && (span <= 0 || span < 2000 || span > 400000) {
+			autoSpan, autoSource := pipeline.AutoSpanForHint(sc.Candidate.Hint)
+			if autoSpan > 0 {
+				span = autoSpan
+				windowSource = autoSource
+			}
+		}
 		if policy.RefinementMinSpanHz > 0 && span < policy.RefinementMinSpanHz {
 			span = policy.RefinementMinSpanHz
 		}
 		if policy.RefinementMaxSpanHz > 0 && span > policy.RefinementMaxSpanHz {
 			span = policy.RefinementMaxSpanHz
 		}
+		if span <= 0 {
+			span = 12000
+		}
 		windows = append(windows, pipeline.RefinementWindow{
 			CenterHz: sc.Candidate.CenterHz,
 			SpanHz:   span,
-			Source:   "candidate",
+			Source:   windowSource,
 		})
 	}
 	input := pipeline.RefinementInput{
diff --git a/config.yaml b/config.yaml
index e560eb8..7915e24 100644
--- a/config.yaml
+++ b/config.yaml
@@ -33,6 +33,7 @@ refinement:
   min_candidate_snr_db: 0
   min_span_hz: 0
   max_span_hz: 0
+  auto_span: true
 resources:
   prefer_gpu: true
   max_refinement_jobs: 8
diff --git a/internal/config/config.go b/internal/config/config.go
index c77e25f..fd9d785 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -99,6 +99,7 @@ type RefinementConfig struct {
 	MinCandidateSNRDb float64 `yaml:"min_candidate_snr_db" json:"min_candidate_snr_db"`
 	MinSpanHz         float64 `yaml:"min_span_hz" json:"min_span_hz"`
 	MaxSpanHz         float64 `yaml:"max_span_hz" json:"max_span_hz"`
+	AutoSpan          bool    `yaml:"auto_span" json:"auto_span"`
 }
 
 type ResourceConfig struct {
@@ -177,6 +178,7 @@ func Default() Config {
 			MinCandidateSNRDb: 0,
 			MinSpanHz:         0,
 			MaxSpanHz:         0,
+			AutoSpan:          true,
 		},
 		Resources: ResourceConfig{
 			PreferGPU:           true,
diff --git a/internal/pipeline/policy.go b/internal/pipeline/policy.go
index dc16400..cabf6d0 100644
--- a/internal/pipeline/policy.go
+++ b/internal/pipeline/policy.go
@@ -20,6 +20,7 @@ type Policy struct {
 	MinCandidateSNRDb   float64  `json:"min_candidate_snr_db"`
 	RefinementMinSpanHz float64  `json:"refinement_min_span_hz"`
 	RefinementMaxSpanHz float64  `json:"refinement_max_span_hz"`
+	RefinementAutoSpan  bool     `json:"refinement_auto_span"`
 	PreferGPU           bool     `json:"prefer_gpu"`
 }
 
@@ -42,6 +43,7 @@ func PolicyFromConfig(cfg config.Config) Policy {
 		MinCandidateSNRDb:   cfg.Refinement.MinCandidateSNRDb,
 		RefinementMinSpanHz: cfg.Refinement.MinSpanHz,
 		RefinementMaxSpanHz: cfg.Refinement.MaxSpanHz,
+		RefinementAutoSpan:  cfg.Refinement.AutoSpan,
 		PreferGPU:           cfg.Resources.PreferGPU,
 	}
 }
diff --git a/internal/pipeline/scheduler_test.go b/internal/pipeline/scheduler_test.go
index 5fdef5a..b0c5565 100644
--- a/internal/pipeline/scheduler_test.go
+++ b/internal/pipeline/scheduler_test.go
@@ -44,6 +44,21 @@ func TestBuildRefinementPlanTracksDrops(t *testing.T) {
 	}
 }
 
+func TestAutoSpanForHint(t *testing.T) {
+	span, source := AutoSpanForHint("WFM_STEREO")
+	if span < 150000 || source == "" {
+		t.Fatalf("expected WFM span, got %.0f (%s)", span, source)
+	}
+	span, source = AutoSpanForHint("CW")
+	if span != 500 || source == "" {
+		t.Fatalf("expected CW span, got %.0f (%s)", span, source)
+	}
+	span, source = AutoSpanForHint("")
+	if span != 0 || source != "" {
+		t.Fatalf("expected empty span for unknown hint, got %.0f (%s)", span, source)
+	}
+}
+
 func TestScheduleCandidatesPriorityBoost(t *testing.T) {
 	policy := Policy{MaxRefinementJobs: 1, MinCandidateSNRDb: 0, SignalPriorities: []string{"digital"}}
 	got := ScheduleCandidates([]Candidate{
diff --git a/internal/pipeline/window_rules.go b/internal/pipeline/window_rules.go
new file mode 100644
index 0000000..f7a261f
--- /dev/null
+++ b/internal/pipeline/window_rules.go
@@ -0,0 +1,30 @@
+package pipeline
+
+import "strings"
+
+// AutoSpanForHint returns a suggested refinement span based on the candidate hint.
+// It is intentionally conservative: spans are wide enough for robust demod/classify,
+// but not so wide that refinement becomes wasteful.
+func AutoSpanForHint(hint string) (float64, string) {
+	h := strings.ToLower(hint)
+	switch {
+	case strings.Contains(h, "wfm"):
+		return 200000, "auto:wfm"
+	case strings.Contains(h, "nfm"):
+		return 18000, "auto:nfm"
+	case strings.Contains(h, "usb") || strings.Contains(h, "lsb") || strings.Contains(h, "ssb"):
+		return 6000, "auto:ssb"
+	case strings.Contains(h, "cw"):
+		return 500, "auto:cw"
+	case strings.Contains(h, "dmr") || strings.Contains(h, "d-star") || strings.Contains(h, "dstar"):
+		return 15000, "auto:dig_voice"
+	case strings.Contains(h, "ft8") || strings.Contains(h, "wspr"):
+		return 4000, "auto:dig_weak"
+	case strings.Contains(h, "fsk") || strings.Contains(h, "psk"):
+		return 6000, "auto:dig"
+	case strings.Contains(h, "am"):
+		return 12000, "auto:am"
+	default:
+		return 0, ""
+	}
+}