diff --git a/app.go b/app.go
index 872b1bc..2f731e7 100644
--- a/app.go
+++ b/app.go
@@ -2400,6 +2400,19 @@ func (a *App) groupDigitalSlots() bool {
 	return v == "1"
 }
 
+// clusterWorkedSameSlot reports the "consider a call already worked only if
+// worked on the SAME band+mode slot" cluster preference (Settings → DX Cluster).
+// Off (default) → a call worked on any band/mode reads as already worked. On →
+// the WORKED-call flag needs the same band and mode (digital-grouped when that
+// option is also on).
+func (a *App) clusterWorkedSameSlot() bool {
+	if a.settings == nil {
+		return false
+	}
+	v, _ := a.settings.Get(a.ctx, "ui.opslog.clusterWorkedSameSlot")
+	return v == "1"
+}
+
 func (a *App) GetUIPref(key string) (string, error) {
 	if a.settings == nil || !a.settingsScoped.Load() {
 		// Distinct from a genuinely-empty pref: the (LOCAL SQLite) settings store
@@ -15925,6 +15938,14 @@ func (a *App) ClusterSpotStatuses(spots []SpotQuery) []SpotStatus {
 	// "I've already QSO'd this exact station" even when the band/mode
 	// makes the entity check say "new-band" or "new-slot".
 	workedCalls, _ := a.qso.WorkedCallsigns(a.ctx)
+	// "Already worked only on the same slot" option (Settings → DX Cluster): the
+	// WORKED-call flag then needs the SAME band and mode (digital-grouped through
+	// the same normMode when that option is on) rather than the call anywhere.
+	sameSlot := a.clusterWorkedSameSlot()
+	var workedCallSlots map[string]struct{}
+	if sameSlot {
+		workedCallSlots, _ = a.qso.WorkedCallSlotKeys(a.ctx, normMode)
+	}
 	// Orthogonal dimensions: worked US counties (for the ULS callsign→county
 	// lookup) and worked POTA parks. Both built once per batch.
 	workedCounties, _ := a.qso.WorkedCountyKeys(a.ctx, award.USCountyKey)
@@ -15945,7 +15966,21 @@ func (a *App) ClusterSpotStatuses(spots []SpotQuery) []SpotStatus {
 			Band: strings.ToLower(q.Band),
 			Mode: strings.ToUpper(q.Mode),
 		}
-		if _, ok := workedCalls[strings.ToUpper(q.Call)]; ok {
+		if sameSlot {
+			// Already worked ONLY when this exact band+mode slot was worked. With no
+			// inferable mode, fall back to same-band (better than claiming the whole
+			// call is fresh). Digital grouping folds through the same normMode.
+			upCall := strings.ToUpper(q.Call)
+			if out[i].Mode == "" {
+				_, out[i].WorkedCall = workedCallSlots[upCall+"|"+out[i].Band]
+			} else {
+				cm := out[i].Mode
+				if normMode != nil {
+					cm = normMode(cm)
+				}
+				_, out[i].WorkedCall = workedCallSlots[upCall+"|"+out[i].Band+"|"+cm]
+			}
+		} else if _, ok := workedCalls[strings.ToUpper(q.Call)]; ok {
 			out[i].WorkedCall = true
 		}
 		// NEW PFX: the spot's CQ WPX prefix, never worked before.
diff --git a/changelog.json b/changelog.json
index f79950b..2470247 100644
--- a/changelog.json
+++ b/changelog.json
@@ -14,7 +14,8 @@
       "The Grid box no longer pops outside the QSO entry panel when the window is narrowed — it wraps to its own line instead.",
       "Selecting a QSO in the Recent QSOs list now shows that station in the Stats (F1) matrix, instead of leaving it blank.",
       "Stats (F1): click any coloured band/mode square to list the contacts behind it.",
-      "Awards: the DXCC list now shows each entity’s main prefix (XE, DL, F…) in its own sortable, searchable column."
+      "Awards: the DXCC list now shows each entity’s main prefix (XE, DL, F…) in its own sortable, searchable column.",
+      "DX Cluster: new option \"Already worked only on the same slot\" (Settings → DX Cluster). With it on, a spot reads \"worked\" only when you worked that callsign on the SAME band and mode — not just anywhere. It respects the digital-mode grouping (Settings → General): grouped, a 20m FT8 contact also marks a 20m FT4 spot as worked; ungrouped, FT8 and FT4 are separate slots."
     ],
     "fr": [
       "Visionneuse de log : la fenêtre conserve deux fois plus d'historique (512 Ko au lieu de 256 Ko, ~3200 lignes). Lors d'une trace chargée, les plus vieilles lignes défilaient hors du buffer pendant qu'on les lisait encore ; la fenêtre agrandie les garde.",
@@ -28,7 +29,8 @@
       "Le champ Locator ne déborde plus du panneau de saisie quand la fenêtre est rétrécie — il passe à la ligne.",
       "Sélectionner un QSO dans la liste des QSO récents affiche désormais cette station dans la matrice Stats (F1), au lieu de la laisser vide.",
       "Stats (F1) : cliquer sur une case bande/mode colorée liste les contacts correspondants.",
-      "Diplômes : la liste DXCC affiche le préfixe principal de chaque entité (XE, DL, F…) dans une colonne triable et cherchable."
+      "Diplômes : la liste DXCC affiche le préfixe principal de chaque entité (XE, DL, F…) dans une colonne triable et cherchable.",
+      "DX Cluster : nouvelle option « Déjà contacté seulement sur le même slot » (Réglages → DX Cluster). Activée, un spot n'affiche « contacté » que si vous avez contacté cet indicatif sur la MÊME bande et le MÊME mode — pas juste n'importe où. Elle respecte le groupage des modes numériques (Réglages → Général) : groupé, un contact 20m FT8 marque aussi un spot 20m FT4 comme contacté ; dégroupé, FT8 et FT4 sont des slots distincts."
     ]
   },
   {
diff --git a/frontend/src/components/SettingsModal.tsx b/frontend/src/components/SettingsModal.tsx
index 5656913..3b12066 100644
--- a/frontend/src/components/SettingsModal.tsx
+++ b/frontend/src/components/SettingsModal.tsx
@@ -1246,6 +1246,7 @@ export function SettingsModal({ onClose, onSaved, initialSection, onMainPaneChan
   const [startEqEnd, setStartEqEnd] = useState(() => localStorage.getItem('opslog.startEqualsEnd') === '1');
   const [lookupOnBlur, setLookupOnBlur] = useState(() => localStorage.getItem('opslog.lookupOnBlur') === '1');
   const [groupDigital, setGroupDigital] = useState(() => localStorage.getItem('opslog.groupDigitalSlots') === '1');
+  const [clusterWorkedSameSlot, setClusterWorkedSameSlot] = useState(() => localStorage.getItem('opslog.clusterWorkedSameSlot') === '1');
   const [showQsoRate, setShowQsoRate] = useState(() => localStorage.getItem('opslog.showQsoRate') === '1');
   const [catModeBeforeFreq, setCatModeBeforeFreq] = useState(() => localStorage.getItem('opslog.catModeBeforeFreq') === '1');
   // Password-encryption (secret vault) state.
@@ -4000,6 +4001,11 @@ export function SettingsModal({ onClose, onSaved, initialSection, onMainPaneChan
             <span className="font-mono">dx.maritimecontestclub.net:7300</span>,{' '}
             <span className="font-mono">w8avi.net:7300</span>.
           </p>
+          <label className="flex items-start gap-2 text-sm cursor-pointer border-t border-border/60 pt-3">
+            <Checkbox checked={clusterWorkedSameSlot} className="mt-0.5"
+              onCheckedChange={(c) => { const v = !!c; setClusterWorkedSameSlot(v); writeUiPref('opslog.clusterWorkedSameSlot', v ? '1' : '0'); }} />
+            <span>{t('clu.workedSameSlot')} <span className="text-xs text-muted-foreground">{t('clu.workedSameSlotHint')}</span></span>
+          </label>
         </div>
 
         {editingServer && (
diff --git a/frontend/src/lib/i18n.tsx b/frontend/src/lib/i18n.tsx
index 6d87527..8fcb319 100644
--- a/frontend/src/lib/i18n.tsx
+++ b/frontend/src/lib/i18n.tsx
@@ -262,6 +262,8 @@ const en: Dict = {
   'clu.moveUp': 'Move up', 'clu.moveDown': 'Move down', 'clu.edit': 'Edit', 'clu.delete': 'Delete', 'clu.none': 'No cluster nodes saved yet.', 'clu.connect': 'Connect', 'clu.disconnect': 'Disconnect',
   'clu.add': 'Add cluster', 'clu.connectAll': 'Connect all', 'clu.disconnectAll': 'Disconnect all', 'clu.autoConnect': 'Auto-connect all enabled on app start',
   'clu.freeNodes': 'Free public nodes:',
+  'clu.workedSameSlot': 'Already worked only on the same slot',
+  'clu.workedSameSlotHint': '— a spot shows "worked" only if you worked that call on the SAME band and mode, not just anywhere. Combines with digital-mode grouping (Settings → General): with it on, a call worked on 20m FT8 also counts as worked for a 20m FT4 spot; with it off, FT8 and FT4 are separate slots.',
   // Backup panel
   'bk.hintMysql': 'On close (once/day) OpsLog snapshots the local SQLite (config) AND exports the shared MySQL log to ADIF — opslog-log-<date>.adi — so your contacts are protected even though they live on the server. Rotation keeps the last N of each.',
   'bk.hint': 'OpsLog can copy the SQLite database to a folder of your choice when you close it, once per day. Rotation keeps the last N copies and deletes older ones.',
@@ -672,6 +674,8 @@ const fr: Dict = {
   'clu.moveUp': 'Monter', 'clu.moveDown': 'Descendre', 'clu.edit': 'Éditer', 'clu.delete': 'Supprimer', 'clu.none': 'Aucun nœud cluster enregistré.', 'clu.connect': 'Connecter', 'clu.disconnect': 'Déconnecter',
   'clu.add': 'Ajouter cluster', 'clu.connectAll': 'Tout connecter', 'clu.disconnectAll': 'Tout déconnecter', 'clu.autoConnect': 'Connexion auto de tous les activés au démarrage',
   'clu.freeNodes': 'Nœuds publics gratuits :',
+  'clu.workedSameSlot': 'Déjà contacté seulement sur le même slot',
+  'clu.workedSameSlotHint': '— un spot n\'affiche « contacté » que si vous avez contacté cet indicatif sur la MÊME bande et le MÊME mode, pas juste n\'importe où. Se combine avec le groupage des modes numériques (Réglages → Général) : activé, un indicatif contacté en 20m FT8 compte aussi comme contacté pour un spot 20m FT4 ; désactivé, FT8 et FT4 sont des slots distincts.',
   'bk.hintMysql': "À la fermeture (1×/jour) OpsLog sauvegarde le SQLite local (config) ET exporte le log MySQL partagé en ADIF — opslog-log-<date>.adi — pour protéger tes contacts même s'ils sont sur le serveur. La rotation garde les N derniers de chaque.",
   'bk.hint': "OpsLog peut copier la base SQLite dans un dossier de ton choix à la fermeture, une fois par jour. La rotation garde les N dernières copies et supprime les plus anciennes.",
   'bk.auto': 'Sauvegarde auto à la fermeture d\'OpsLog (max 1×/jour)', 'bk.folder': 'Dossier de sauvegarde', 'bk.folderPh': 'vide = dossier par défaut', 'bk.browse': 'Parcourir…',
diff --git a/internal/qso/qso.go b/internal/qso/qso.go
index b20d2a9..722ebe0 100644
--- a/internal/qso/qso.go
+++ b/internal/qso/qso.go
@@ -2163,6 +2163,36 @@ func (r *Repo) WorkedCallBandModeKeys(ctx context.Context) (map[string]struct{},
 	return out, rows.Err()
 }
 
+// WorkedCallSlotKeys backs the cluster "already worked only on the same slot"
+// option. It returns each worked slot keyed BOTH as "CALL|band" (mode-agnostic,
+// for a spot whose mode couldn't be inferred) and "CALL|band|MODE" with the mode
+// run through normMode — so when digital grouping is on, FT8/FT4/RTTY fold into
+// one "DIG" and a call worked on 20m FT8 also matches a 20m FT4 spot. Call is
+// upper-cased and band lower-cased to match the spot keys ClusterSpotStatuses
+// builds. normMode may be nil (no grouping).
+func (r *Repo) WorkedCallSlotKeys(ctx context.Context, normMode func(string) string) (map[string]struct{}, error) {
+	rows, err := r.db.QueryContext(ctx,
+		`SELECT upper(callsign), lower(band), upper(mode) FROM qso
+		 WHERE callsign != '' AND band IS NOT NULL AND band != '' AND mode IS NOT NULL AND mode != ''`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	out := make(map[string]struct{}, 4096)
+	for rows.Next() {
+		var c, b, m string
+		if err := rows.Scan(&c, &b, &m); err != nil {
+			return nil, err
+		}
+		if normMode != nil {
+			m = normMode(m)
+		}
+		out[c+"|"+b] = struct{}{}
+		out[c+"|"+b+"|"+m] = struct{}{}
+	}
+	return out, rows.Err()
+}
+
 // WorkedPOTARefs returns the set of POTA park references already worked
 // (upper-cased). A QSO's pota_ref may hold several comma-separated parks
 // (an n-fer); each is added separately.