feat(#1290): exclude listener-only observers from path-hop disambiguator

Firmware 1.16 publishes a `repeat: on|off` flag in the MQTT /status
JSON (confirmed by cwichura on the issue; see
MQTTMessageBuilder.cpp:58 in agessaman/MeshCore
mqtt-bridge-implementation-flex). Listener-only observers
(repeat:off) by firmware contract never relay packets, so they
cannot legitimately be a hop in someone else's resolved path.

Pipeline:

* internal/dbschema: idempotent `can_relay BOOLEAN DEFAULT 1`
  migration on observers, plus AssertReady probe (server fatal-logs
  if absent). Mirrored in cmd/ingestor/db.go CREATE TABLE for fresh
  DBs.

* cmd/ingestor: `extractObserverMeta` accepts `repeat` as bool,
  case-insensitive string (`on|off|true|false|yes|no`), or numeric
  0/1; missing field → nil → COALESCE preserves prior column value
  (back-compat with legacy observers). Plumbed through
  UpsertObserverAt and the prepared upsert statement.

* cmd/server: GetNonRelayObserverPubkeys + new prefixMap.markNonRelay
  drop matching candidates inside resolveWithContext. Filter is
  applied at the top of the resolver so all 4 tiers see the
  pruned candidate set. ObserverResp.CanRelay is surfaced to
  /api/observers and /api/observers/{id}; GetNodeHealth enriches
  the per-observer rows with can_relay so the node-detail badge
  works. Probe-and-fall-back when can_relay column is absent
  (legacy test fixtures).

* public/: listener vs repeater pill on observers list,
  observer detail Relay stat card, and node-detail Heard By table.
  CSS pill styles inherit existing theme vars.

Green for the test added in the prior red commit:
TestResolveWithContext_ExcludesNonRelayObservers_Issue1290.
Back-compat preserved: legacy observers (no `repeat` field) keep
the default can_relay=1 and remain candidates.

cross-stack: justified — backend persists firmware-side `repeat` hint to a new observers column, frontend surfaces the listener/repeater status as a badge on the observers list and node-detail Heard By table per the issue's UI acceptance criterion.

cmd/ingestor/db.go

@@ -197,7 +197,8 @@ func applySchema(db *sql.DB) error {
 			last_packet_at TEXT DEFAULT NULL,
 			clock_skew_seconds INTEGER DEFAULT NULL,
 			clock_skew_count_24h INTEGER DEFAULT 0,
-			clock_last_naive_at TEXT DEFAULT NULL
+			clock_last_naive_at TEXT DEFAULT NULL,
+			can_relay INTEGER DEFAULT 1
 		);
 
 		CREATE INDEX IF NOT EXISTS idx_nodes_last_seen ON nodes(last_seen);
@@ -727,8 +728,8 @@ func (s *Store) prepareStatements() error {
 	}
 
 	s.stmtUpsertObserver, err = s.db.Prepare(`
-		INSERT INTO observers (id, name, iata, last_seen, first_seen, packet_count, model, firmware, client_version, radio, battery_mv, uptime_secs, noise_floor)
+		INSERT INTO observers (id, name, iata, last_seen, first_seen, packet_count, model, firmware, client_version, radio, battery_mv, uptime_secs, noise_floor, can_relay)
-		VALUES (?, ?, ?, ?, ?, 1, ?, ?, ?, ?, ?, ?, ?)
+		VALUES (?, ?, ?, ?, ?, 1, ?, ?, ?, ?, ?, ?, ?, COALESCE(?, 1))
 		ON CONFLICT(id) DO UPDATE SET
 			name = COALESCE(?, name),
 			iata = COALESCE(?, iata),
@@ -740,7 +741,8 @@ func (s *Store) prepareStatements() error {
 			radio = COALESCE(?, radio),
 			battery_mv = COALESCE(?, battery_mv),
 			uptime_secs = COALESCE(?, uptime_secs),
-			noise_floor = COALESCE(?, noise_floor)
+			noise_floor = COALESCE(?, noise_floor),
+			can_relay = COALESCE(?, can_relay)
 	`)
 	if err != nil {
 		return err
@@ -973,6 +975,13 @@ type ObserverMeta struct {
 	RecvErrors    *int     // cumulative CRC/decode failures since boot
 	PacketsSent   *int     // cumulative packets sent since boot
 	PacketsRecv   *int     // cumulative packets received since boot
+	// CanRelay reflects the firmware 1.16 /status `repeat` flag (#1290).
+	// nil means the firmware did not send the field — caller must
+	// preserve the existing observers.can_relay value (default 1).
+	// true → relay-capable (`repeat:on`); false → listener-only
+	// (`repeat:off`), which causes the server-side disambiguator to
+	// exclude this observer's pubkey from path-hop candidate sets.
+	CanRelay *bool
 }
 
 // UpsertObserver inserts or updates an observer using the current wall-clock
@@ -995,7 +1004,7 @@ func (s *Store) UpsertObserverAt(id, name, iata string, meta *ObserverMeta, last
 	normalizedIATA := strings.TrimSpace(strings.ToUpper(iata))
 
 	var model, firmware, clientVersion, radio interface{}
-	var batteryMv, uptimeSecs, noiseFloor interface{}
+	var batteryMv, uptimeSecs, noiseFloor, canRelay interface{}
 	if meta != nil {
 		if meta.Model != nil {
 			model = *meta.Model
@@ -1018,11 +1027,22 @@ func (s *Store) UpsertObserverAt(id, name, iata string, meta *ObserverMeta, last
 		if meta.NoiseFloor != nil {
 			noiseFloor = *meta.NoiseFloor
 		}
+		// Issue #1290: nil → leave DB column unchanged (COALESCE in
+		// the prepared stmt); 0/1 written when firmware provided
+		// the `repeat` field. INSERT branch defaults to 1 via the
+		// COALESCE in the VALUES clause.
+		if meta.CanRelay != nil {
+			if *meta.CanRelay {
+				canRelay = 1
+			} else {
+				canRelay = 0
+			}
+		}
 	}
 
 	_, err := s.stmtUpsertObserver.Exec(
-		id, name, normalizedIATA, lastSeen, lastSeen, model, firmware, clientVersion, radio, batteryMv, uptimeSecs, noiseFloor,
+		id, name, normalizedIATA, lastSeen, lastSeen, model, firmware, clientVersion, radio, batteryMv, uptimeSecs, noiseFloor, canRelay,
-		name, normalizedIATA, ingestNow, lastSeen, model, firmware, clientVersion, radio, batteryMv, uptimeSecs, noiseFloor,
+		name, normalizedIATA, ingestNow, lastSeen, model, firmware, clientVersion, radio, batteryMv, uptimeSecs, noiseFloor, canRelay,
 	)
 	if err != nil {
 		s.Stats.WriteErrors.Add(1)

cmd/ingestor/main.go

@@ -1124,6 +1124,37 @@ func extractObserverMeta(msg map[string]interface{}) *ObserverMeta {
 		}
 	}
 
+	// Issue #1290: firmware 1.16 publishes a `repeat` flag at the top
+	// level of the /status JSON (MQTTMessageBuilder.cpp:58 — see
+	// agessaman/MeshCore mqtt-bridge-implementation-flex). Accept
+	// either a boolean or a case-insensitive `on|off|true|false|1|0`
+	// string. Missing field → leave CanRelay nil; the writer preserves
+	// the prior column value (default 1, back-compat).
+	if v, ok := msg["repeat"]; ok && v != nil {
+		switch t := v.(type) {
+		case bool:
+			b := t
+			meta.CanRelay = &b
+			hasData = true
+		case string:
+			s := strings.ToLower(strings.TrimSpace(t))
+			switch s {
+			case "on", "true", "1", "yes":
+				b := true
+				meta.CanRelay = &b
+				hasData = true
+			case "off", "false", "0", "no":
+				b := false
+				meta.CanRelay = &b
+				hasData = true
+			}
+		case float64:
+			b := t != 0
+			meta.CanRelay = &b
+			hasData = true
+		}
+	}
+
 	if !hasData {
 		return nil
 	}

cmd/server/db.go

@@ -12,6 +12,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/meshcore-analyzer/dbschema"
 	"github.com/meshcore-analyzer/geofilter"
 	_ "modernc.org/sqlite"
 )
@@ -251,6 +252,11 @@ type Observer struct {
 	ClockSkewSeconds  *int64  `json:"clock_skew_seconds"`
 	ClockSkewCount24h int     `json:"clock_skew_count_24h"`
 	ClockLastNaiveAt  *string `json:"clock_last_naive_at"`
+	// Issue #1290: firmware 1.16 `repeat: on|off` flag persisted by the
+	// ingestor. true = relay-capable (default for legacy observers).
+	// false = listener-only; cmd/server/store.go pm.resolveWithContext
+	// excludes these from path-hop candidate sets.
+	CanRelay bool `json:"can_relay"`
 }
 
 // Transmission represents a row from the transmissions table.
@@ -1148,9 +1154,17 @@ func (db *DB) getObservationsForTransmissions(txIDs []int) map[int][]map[string]
 
 // GetObservers returns active observers (not soft-deleted) sorted by last_seen DESC.
 func (db *DB) GetObservers() ([]Observer, error) {
+	// Issue #1290: can_relay is read via COALESCE(can_relay, 1). The
+	// column is added by internal/dbschema; older test fixtures and
+	// pre-migration DBs may lack it, so we probe and fall back.
+	canRelayClause := "COALESCE(can_relay, 1)"
+	if hasCol, _ := dbschema.TableHasColumn(db.conn, "observers", "can_relay"); !hasCol {
+		canRelayClause = "1"
+	}
 	rows, err := db.conn.Query(`SELECT id, name, iata, last_seen, first_seen, packet_count,
 		model, firmware, client_version, radio, battery_mv, uptime_secs, noise_floor, last_packet_at,
-		clock_skew_seconds, clock_skew_count_24h, clock_last_naive_at
+		clock_skew_seconds, clock_skew_count_24h, clock_last_naive_at,
+		` + canRelayClause + `
 		FROM observers WHERE inactive IS NULL OR inactive = 0 ORDER BY last_seen DESC`)
 	if err != nil {
 		return nil, err
@@ -1163,11 +1177,13 @@ func (db *DB) GetObservers() ([]Observer, error) {
 		var batteryMv, uptimeSecs, clockSkewSec sql.NullInt64
 		var clockSkewCount sql.NullInt64
 		var noiseFloor sql.NullFloat64
+		var canRelay int
 		if err := rows.Scan(&o.ID, &o.Name, &o.IATA, &o.LastSeen, &o.FirstSeen, &o.PacketCount,
 			&o.Model, &o.Firmware, &o.ClientVersion, &o.Radio, &batteryMv, &uptimeSecs, &noiseFloor, &o.LastPacketAt,
-			&clockSkewSec, &clockSkewCount, &o.ClockLastNaiveAt); err != nil {
+			&clockSkewSec, &clockSkewCount, &o.ClockLastNaiveAt, &canRelay); err != nil {
 			continue
 		}
+		o.CanRelay = canRelay != 0
 		if batteryMv.Valid {
 			v := int(batteryMv.Int64)
 			o.BatteryMv = &v
@@ -1190,22 +1206,58 @@ func (db *DB) GetObservers() ([]Observer, error) {
 	return observers, nil
 }
 
+// GetNonRelayObserverPubkeys returns the lowercase observer.id pubkeys
+// for observers that have advertised `repeat:off` (#1290). The server's
+// path-hop disambiguator consumes this to exclude listener-only nodes
+// from the candidate set. Inactive observers are excluded for
+// consistency with GetObservers; reactivation flips can_relay only on
+// the next status message.
+func (db *DB) GetNonRelayObserverPubkeys() ([]string, error) {
+	// Graceful no-op when can_relay column is absent (legacy DB / older
+	// test fixture). Avoids noisy schema-degradation log spam.
+	if hasCol, _ := dbschema.TableHasColumn(db.conn, "observers", "can_relay"); !hasCol {
+		return nil, nil
+	}
+	rows, err := db.conn.Query(`SELECT LOWER(id) FROM observers
+		WHERE COALESCE(can_relay, 1) = 0
+		  AND (inactive IS NULL OR inactive = 0)`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []string
+	for rows.Next() {
+		var pk string
+		if err := rows.Scan(&pk); err == nil && pk != "" {
+			out = append(out, pk)
+		}
+	}
+	return out, rows.Err()
+}
+
 // GetObserverByID returns a single observer.
 func (db *DB) GetObserverByID(id string) (*Observer, error) {
 	var o Observer
 	var batteryMv, uptimeSecs, clockSkewSec sql.NullInt64
 	var clockSkewCount sql.NullInt64
 	var noiseFloor sql.NullFloat64
+	var canRelay int
+	canRelayClause := "COALESCE(can_relay, 1)"
+	if hasCol, _ := dbschema.TableHasColumn(db.conn, "observers", "can_relay"); !hasCol {
+		canRelayClause = "1"
+	}
 	err := db.conn.QueryRow(`SELECT id, name, iata, last_seen, first_seen, packet_count,
 		model, firmware, client_version, radio, battery_mv, uptime_secs, noise_floor, last_packet_at,
-		clock_skew_seconds, clock_skew_count_24h, clock_last_naive_at
+		clock_skew_seconds, clock_skew_count_24h, clock_last_naive_at,
+		`+canRelayClause+`
 		FROM observers WHERE id = ?`, id).
 		Scan(&o.ID, &o.Name, &o.IATA, &o.LastSeen, &o.FirstSeen, &o.PacketCount,
 			&o.Model, &o.Firmware, &o.ClientVersion, &o.Radio, &batteryMv, &uptimeSecs, &noiseFloor, &o.LastPacketAt,
-			&clockSkewSec, &clockSkewCount, &o.ClockLastNaiveAt)
+			&clockSkewSec, &clockSkewCount, &o.ClockLastNaiveAt, &canRelay)
 	if err != nil {
 		return nil, err
 	}
+	o.CanRelay = canRelay != 0
 	if batteryMv.Valid {
 		v := int(batteryMv.Int64)
 		o.BatteryMv = &v

cmd/server/routes.go

@@ -2534,6 +2534,7 @@ func (s *Server) buildObserversDefaultResponse() (ObserverListResponse, error) {
 			LastPacketAt:    o.LastPacketAt,
 			PacketsLastHour: plh,
 			Lat:             lat, Lon: lon, NodeRole: nodeRole,
+			CanRelay: o.CanRelay,
 		}
 		applyObserverNaiveClock(&resp, o, nowTime)
 		result = append(result, resp)
@@ -2578,6 +2579,7 @@ func (s *Server) handleObserverDetail(w http.ResponseWriter, r *http.Request) {
 			NoiseFloor:      obs.NoiseFloor,
 			LastPacketAt:    obs.LastPacketAt,
 			PacketsLastHour: plh,
+			CanRelay:        obs.CanRelay,
 		}
 		applyObserverNaiveClock(&resp, obs, time.Now().UTC())
 		return resp

cmd/server/store.go

@@ -6194,6 +6194,17 @@ func (s *PacketStore) getCachedNodesAndPM() ([]nodeInfo, *prefixMap) {
 
 	nodes := s.getAllNodes()
 	pm := buildPrefixMap(nodes)
+	// Issue #1290: exclude observers that advertised `repeat:off` from
+	// the path-hop candidate set. Failure is non-fatal — we log via the
+	// schema-degradation channel and proceed with an empty filter (i.e.
+	// pre-#1290 behavior).
+	if s.db != nil && s.db.conn != nil {
+		if pks, err := s.db.GetNonRelayObserverPubkeys(); err == nil {
+			pm.markNonRelay(pks)
+		} else {
+			s.logSchemaDegradationOnce("observers.can_relay read failed; path-hop disambiguator will not filter listener-only observers: " + err.Error())
+		}
+	}
 
 	s.cacheMu.Lock()
 	s.nodeCache = nodes
@@ -6257,6 +6268,25 @@ func (pm *prefixMap) resolve(hop string) *nodeInfo {
 func (pm *prefixMap) resolveWithContext(hop string, contextPubkeys []string, graph *NeighborGraph) (*nodeInfo, string, float64) {
 	h := strings.ToLower(hop)
 	candidates := pm.m[h]
+	// Issue #1290: drop observer-known listener-only nodes from the
+	// candidate set. By firmware contract a node that advertises
+	// `repeat:off` in its MQTT /status will never relay a packet, so it
+	// cannot legitimately be a hop in someone else's path. Filtering
+	// here shrinks ambiguous candidate sets without affecting any
+	// upstream caller (the returned shape and confidence labels are
+	// preserved; only no_match becomes more likely when the only
+	// matching prefix belonged to a listener). Empty pm.nonRelay
+	// preserves the pre-#1290 behavior exactly (back-compat).
+	if len(pm.nonRelay) > 0 && len(candidates) > 0 {
+		filtered := candidates[:0:0]
+		for i := range candidates {
+			if _, isListener := pm.nonRelay[strings.ToLower(candidates[i].PublicKey)]; isListener {
+				continue
+			}
+			filtered = append(filtered, candidates[i])
+		}
+		candidates = filtered
+	}
 	if len(candidates) == 0 {
 		return nil, "no_match", 0
 	}
@@ -8870,6 +8900,18 @@ func (s *PacketStore) GetNodeHealth(pubkey string) (map[string]interface{}, erro
 	}
 
 	observerRows := make([]map[string]interface{}, 0)
+	// Issue #1290: surface listener/repeater hint on node detail by
+	// looking up can_relay for each observer that heard this node.
+	// One-shot fetch of the non-relay set keeps this O(observers) on
+	// rare events; nil on error degrades to "neither badge" client-side.
+	nonRelaySet := map[string]struct{}{}
+	if s.db != nil && s.db.conn != nil {
+		if pks, err := s.db.GetNonRelayObserverPubkeys(); err == nil {
+			for _, pk := range pks {
+				nonRelaySet[strings.ToUpper(pk)] = struct{}{}
+			}
+		}
+	}
 	for id, o := range observerStats {
 		var avgSnr, avgRssi interface{}
 		if o.snrCount > 0 {
@@ -8878,9 +8920,14 @@ func (s *PacketStore) GetNodeHealth(pubkey string) (map[string]interface{}, erro
 		if o.rssiCount > 0 {
 			avgRssi = o.rssiSum / float64(o.rssiCount)
 		}
+		canRelay := true
+		if _, isListener := nonRelaySet[strings.ToUpper(id)]; isListener {
+			canRelay = false
+		}
 		observerRows = append(observerRows, map[string]interface{}{
 			"observer_id": id, "observer_name": o.name,
 			"avgSnr": avgSnr, "avgRssi": avgRssi, "packetCount": o.count,
+			"can_relay": canRelay,
 		})
 	}
 	sort.Slice(observerRows, func(i, j int) bool {

cmd/server/types.go

@@ -909,6 +909,10 @@ type ObserverResp struct {
 	ClockSkewSeconds  interface{} `json:"clock_skew_seconds"`
 	ClockSkewCount24h int         `json:"clock_skew_count_24h"`
 	ClockLastNaiveAt  interface{} `json:"clock_last_naive_at"`
+	// Issue #1290: firmware 1.16 `repeat` flag — true=repeater,
+	// false=listener-only. Drives the UI badge on observers list +
+	// node detail page. Defaults to true for legacy observers.
+	CanRelay bool `json:"can_relay"`
 }
 
 type ObserverListResponse struct {

internal/dbschema/dbschema.go

@@ -82,6 +82,9 @@ func Apply(rw *sql.DB, logf Logger) error {
 	if err := ensureObserverNaiveClockColumns(rw, logf); err != nil {
 		return fmt.Errorf("ensure observers naive-clock columns: %w", err)
 	}
+	if err := ensureObserverCanRelayColumn(rw, logf); err != nil {
+		return fmt.Errorf("ensure observers.can_relay: %w", err)
+	}
 	return nil
 }
 
@@ -138,6 +141,12 @@ func AssertReady(ro *sql.DB) error {
 	mustCol("observers", "clock_skew_seconds")
 	mustCol("observers", "clock_skew_count_24h")
 	mustCol("observers", "clock_last_naive_at")
+	// Issue #1290: firmware 1.16 publishes a `repeat: on|off` flag in
+	// the MQTT /status JSON. Ingestor persists it as can_relay; server
+	// reads it to filter listener-only observers out of the path-hop
+	// disambiguator candidate set. Default 1 preserves prior behavior
+	// for legacy observers that never sent the field.
+	mustCol("observers", "can_relay")
 
 	if len(missing) > 0 {
 		return fmt.Errorf("schema not migrated by ingestor; restart ingestor first. missing: %s",
@@ -522,3 +531,25 @@ func ensureObserverNaiveClockColumns(rw *sql.DB, logf Logger) error {
 	}
 	return nil
 }
+
+// ensureObserverCanRelayColumn adds the can_relay column to observers.
+// Firmware 1.16 publishes a `repeat: on|off` flag in the MQTT /status
+// JSON (#1290); the ingestor parses it and writes 0/1 here. The server's
+// path-hop disambiguator (cmd/server/store.go pm.resolveWithContext)
+// excludes observers with can_relay=0 from the candidate set. Default 1
+// preserves prior behavior for legacy observers (no repeat field).
+func ensureObserverCanRelayColumn(rw *sql.DB, logf Logger) error {
+	has, err := TableHasColumn(rw, "observers", "can_relay")
+	if err != nil {
+		return err
+	}
+	if has {
+		return nil
+	}
+	// PREFLIGHT: async=true reason="single-column ALTER on observers (low-cardinality, ~1k rows in prod); DEFAULT 1 is a constant so SQLite does the rewrite as a metadata-only schema update, no row scan"
+	if _, err := rw.Exec("ALTER TABLE observers ADD COLUMN can_relay INTEGER DEFAULT 1"); err != nil {
+		return err
+	}
+	logf("[dbschema] added can_relay column to observers")
+	return nil
+}

public/nodes.js

@@ -676,7 +676,7 @@
             </tr></thead>
             <tbody>
               ${observers.map(o => `<tr>
-                <td data-value="${escapeHtml((o.observer_name || o.observer_id || '').toLowerCase())}" style="font-weight:600">${escapeHtml(o.observer_name || o.observer_id)}</td>
+                <td data-value="${escapeHtml((o.observer_name || o.observer_id || '').toLowerCase())}" style="font-weight:600">${escapeHtml(o.observer_name || o.observer_id)}${o.can_relay === false ? ' <span class="badge-listener" title="Firmware reported repeat:off — excluded from path-hop disambiguator (#1290)">listener</span>' : (o.can_relay === true ? ' <span class="badge-repeater" title="Firmware reported repeat:on — eligible as a path hop">repeater</span>' : '')}</td>
                 <td data-value="${escapeHtml((o.iata || '').toLowerCase())}">${o.iata ? escapeHtml(o.iata) : '—'}</td>
                 <td data-value="${o.packetCount || 0}">${o.packetCount}</td>
                 <td data-value="${o.avgSnr != null ? Number(o.avgSnr) : ''}">${o.avgSnr != null ? Number(o.avgSnr).toFixed(1) + ' dB' : '—'}</td>

public/observer-detail.js

@@ -180,6 +180,10 @@ window.ObserverDetailNaiveBanner = {
           <div class="stat-label">Status</div>
           <div class="stat-value"><span class="health-dot ${statusCls}">●</span> ${statusLabel}</div>
         </div>
+        <div class="stat-card">
+          <div class="stat-label">Relay</div>
+          <div class="stat-value">${obs.can_relay === false ? '<span class="badge-listener" title="Firmware reported repeat:off — excluded from path-hop disambiguator (#1290)">listener</span>' : '<span class="badge-repeater" title="Firmware reported repeat:on (or unknown) — eligible as a path hop">repeater</span>'}</div>
+        </div>
         <div class="stat-card">
           <div class="stat-label">Region</div>
           <div class="stat-value">${obs.iata ? '<span class="badge-region">' + escapeHtml(obs.iata) + '</span>' : '—'}</div>

public/observers.js

@@ -297,7 +297,7 @@ window.ObserversSummary = (function () {
           const shape = h.cls === 'health-green' ? '●' : h.cls === 'health-yellow' ? '▲' : '✕';
           return `<tr style="cursor:pointer" tabindex="0" role="row" data-action="navigate" data-value="#/observers/${encodeURIComponent(o.id)}" onclick="location.hash='#/observers/${encodeURIComponent(o.id)}'">
             <td><span class="health-dot ${h.cls}" title="${h.label}">${shape}</span> ${h.label}</td>
-            <td class="mono">${escapeHtml(o.name || o.id)}${window.ObserversNaiveChip.render(o)}</td>
+            <td class="mono">${escapeHtml(o.name || o.id)}${window.ObserversNaiveChip.render(o)}${o.can_relay === false ? ' <span class="badge-listener" title="Firmware reported repeat:off — listener-only; excluded from path-hop disambiguator (issue #1290)">listener</span>' : ' <span class="badge-repeater" title="Firmware reported repeat:on (or unknown) — eligible as a path hop">repeater</span>'}</td>
             <td>${o.iata ? `<span class="badge-region">${o.iata}</span>` : '—'}</td>
             <td>${timeAgo(o.last_seen)}</td>
             <td>${o.last_packet_at ? timeAgo(o.last_packet_at) : '<span class="text-muted">—</span>'}</td>

public/style.css

@@ -1146,6 +1146,24 @@ body.scroll-locked { overflow: hidden; }
   font-size: 10px; font-weight: 700; font-family: var(--mono);
   background: var(--nav-bg); color: var(--nav-text); letter-spacing: .5px;
 }
+/* Issue #1290: listener vs repeater badge on observers list + detail.
+ * Driven by ObserverResp.can_relay (false = firmware reported repeat:off).
+ * Server-side disambiguator excludes listener observers from path-hop
+ * candidates; this badge surfaces the same hint to operators. Colors use
+ * existing theme vars so the badge tracks the active palette. */
+.badge-listener,
+.badge-repeater {
+  display: inline-block; padding: 1px 5px; border-radius: 4px;
+  font-size: 10px; font-weight: 700; font-family: var(--mono);
+  letter-spacing: .5px; margin-left: 4px; vertical-align: middle;
+}
+.badge-listener {
+  background: var(--transport-badge-bg, #f59e0b20);
+  color: var(--transport-badge-fg, #d97706);
+}
+.badge-repeater {
+  background: var(--nav-bg); color: var(--nav-text);
+}
 /* Observer IATA pill rendered inline next to observer name on packets (#1188).
  * Visually similar to .badge-region but distinct so the row badge and the
  * inline-with-observer badge can be styled independently in future themes. */