diff --git a/db/observer_adverts_integration_test.go b/db/observer_adverts_integration_test.go
new file mode 100644
index 00000000..2531e37d
--- /dev/null
+++ b/db/observer_adverts_integration_test.go
@@ -0,0 +1,85 @@
+// Copyright 2026 Beacon Contributors
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+package db
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"strings"
+	"testing"
+	"time"
+
+	sqlc "github.com/MeshCore-Beacon/beacon-server/db/sqlc"
+	"github.com/MeshCore-Beacon/beacon-server/internal/api"
+	"github.com/MeshCore-Beacon/beacon-server/internal/api/handlers"
+	"github.com/jackc/pgx/v5"
+)
+
+func TestObserverAdvertsPostgres(t *testing.T) {
+	dsn := os.Getenv("BEACON_TEST_POSTGRES_DSN")
+	if dsn == "" {
+		t.Skip("set BEACON_TEST_POSTGRES_DSN for PostgreSQL regression")
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+	conn, err := pgx.Connect(ctx, dsn)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer conn.Close(context.Background())
+	tx, err := conn.Begin(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer tx.Rollback(context.Background())
+	_, err = tx.Exec(ctx, `
+CREATE TEMP TABLE packets (LIKE public.packets INCLUDING ALL) ON COMMIT DROP;
+CREATE TEMP TABLE packet_observations (LIKE public.packet_observations INCLUDING ALL) ON COMMIT DROP;
+CREATE TEMP TABLE nodes (LIKE public.nodes INCLUDING ALL) ON COMMIT DROP;
+INSERT INTO nodes(public_key,node_type,name) VALUES (decode(repeat('01',32),'hex'),1,'Known fixture node');
+INSERT INTO packets(packet_hash,payload_type,payload_version,route_type,origin_pubkey,raw_payload,raw_header,first_heard_at,last_heard_at) VALUES
+ (decode(repeat('a1',32),'hex'),4,0,1,NULL,'\x00','\x00',now(),now()),
+ (decode(repeat('b2',32),'hex'),4,0,1,decode(repeat('01',32),'hex'),'\x00','\x00',now(),now());
+INSERT INTO packet_observations(id,packet_hash,observer_id,iata,heard_at,path_length_byte,hash_size,hop_count) VALUES
+ (1,decode(repeat('a1',32),'hex'),'00000000-0000-0000-0000-000000000106','YOW',now(),0,1,0),
+ (2,decode(repeat('b2',32),'hex'),'00000000-0000-0000-0000-000000000106','YOW',now(),0,1,0);`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	router := handlers.ObserversRouter(&Store{q: sqlc.New(tx)})
+	request := func(query string) api.Page[api.AdvertObservation] {
+		t.Helper()
+		response := httptest.NewRecorder()
+		router.ServeHTTP(response, httptest.NewRequest(http.MethodGet, "/00000000-0000-0000-0000-000000000106/adverts?"+query, nil).WithContext(ctx))
+		if response.Code != http.StatusOK {
+			t.Fatalf("advert page HTTP %d", response.Code)
+		}
+		var page api.Page[api.AdvertObservation]
+		if err := json.Unmarshal(response.Body.Bytes(), &page); err != nil {
+			t.Fatal(err)
+		}
+		return page
+	}
+	page := request("limit=50")
+	if len(page.Items) != 2 || page.Items[0].ID != 1 || page.Items[1].ID != 2 {
+		t.Fatal("missing-origin advert was not preserved in the ordered page")
+	}
+	if key := page.Items[0].NodePublicKey; key == nil || *key != "" {
+		t.Errorf("missing origin key = %v, want an empty string", key)
+	}
+	if key := page.Items[1].NodePublicKey; key == nil || *key != strings.Repeat("01", 32) {
+		t.Error("known origin key changed")
+	}
+	first := request("limit=1")
+	if !first.HasMore || first.NextCursor == nil || *first.NextCursor != 1 {
+		t.Fatal("missing-origin advert broke the cursor")
+	}
+	last := request("limit=1&cursor=1")
+	if len(last.Items) != 1 || last.Items[0].ID != 2 || last.HasMore {
+		t.Fatal("continuing after the missing-origin advert lost the known advert")
+	}
+}
diff --git a/db/queries/queries.sql b/db/queries/queries.sql
index 2e72472e..3bd18618 100644
--- a/db/queries/queries.sql
+++ b/db/queries/queries.sql
@@ -313,6 +313,7 @@ ORDER BY count DESC;
 -- name: ListObserverAdverts :many
 -- Returns advert packets (payload_type=4) heard by a specific observer.
 -- Pass cursor=0 to start from the beginning, or the last seen id for pagination.
+-- Keep missing-origin adverts; the generated key field expects a string, not NULL.
 SELECT 
   po.id,
   encode(po.packet_hash, 'hex') AS packet_hash_hex,
@@ -323,7 +324,7 @@ SELECT
   po.snr,
   po.hop_count,
   n.name AS node_name,
-  encode(p.origin_pubkey, 'hex') AS node_public_key
+  COALESCE(encode(p.origin_pubkey, 'hex'), '')::text AS node_public_key
 FROM packet_observations po
 JOIN packets p ON p.packet_hash = po.packet_hash
 LEFT JOIN nodes n ON n.public_key = p.origin_pubkey
diff --git a/db/sqlc/querier.go b/db/sqlc/querier.go
index 7a64432e..ec502af7 100644
--- a/db/sqlc/querier.go
+++ b/db/sqlc/querier.go
@@ -151,6 +151,7 @@ type Querier interface {
 	ListObservationsForPacket(ctx context.Context, packetHash []byte) ([]ListObservationsForPacketRow, error)
 	// Returns advert packets (payload_type=4) heard by a specific observer.
 	// Pass cursor=0 to start from the beginning, or the last seen id for pagination.
+	// Keep missing-origin adverts; the generated key field expects a string, not NULL.
 	ListObserverAdverts(ctx context.Context, arg ListObserverAdvertsParams) ([]ListObserverAdvertsRow, error)
 	// Pass cursor=0 to start from the beginning, or the last seen observer's rownum for pagination.
 	// Note: observers use UUID PKs so we order by last_seen and use a keyset on last_seen+id.
diff --git a/db/sqlc/queries.sql.go b/db/sqlc/queries.sql.go
index 998889f2..fec385d6 100644
--- a/db/sqlc/queries.sql.go
+++ b/db/sqlc/queries.sql.go
@@ -2860,7 +2860,7 @@ SELECT
   po.snr,
   po.hop_count,
   n.name AS node_name,
-  encode(p.origin_pubkey, 'hex') AS node_public_key
+  COALESCE(encode(p.origin_pubkey, 'hex'), '')::text AS node_public_key
 FROM packet_observations po
 JOIN packets p ON p.packet_hash = po.packet_hash
 LEFT JOIN nodes n ON n.public_key = p.origin_pubkey
@@ -2892,6 +2892,7 @@ type ListObserverAdvertsRow struct {
 
 // Returns advert packets (payload_type=4) heard by a specific observer.
 // Pass cursor=0 to start from the beginning, or the last seen id for pagination.
+// Keep missing-origin adverts; the generated key field expects a string, not NULL.
 func (q *Queries) ListObserverAdverts(ctx context.Context, arg ListObserverAdvertsParams) ([]ListObserverAdvertsRow, error) {
 	rows, err := q.db.Query(ctx, listObserverAdverts, arg.ObserverID, arg.Column2, arg.Limit)
 	if err != nil {