fix: skip zero-hop adverts when checking node hash size (#493)

Fixes issue router IDs flapping between 1byte and multi-byte as
described in https://github.com/Kpa-clawbot/CoreScope/issues/303 with a
minimal patch + test coverage.

This fix is critical for regions using multi-byte IDs.

Closes https://github.com/Kpa-clawbot/CoreScope/issues/303

---------

Co-authored-by: you <you@example.com>

cmd/server/routes_test.go

@@ -2178,6 +2178,124 @@ func TestGetNodeHashSizeInfoLatestWins(t *testing.T) {
 	}
 }
 
+func TestGetNodeHashSizeInfoIgnoreDirectZeroHop(t *testing.T) {
+	db := setupTestDB(t)
+	seedTestData(t, db)
+	store := NewPacketStore(db, nil)
+	if err := store.Load(); err != nil {
+		t.Fatalf("store.Load failed: %v", err)
+	}
+
+	pk := "dddd111122223333444455556666777788889999aaaabbbbccccddddeeee3333"
+	db.conn.Exec("INSERT OR IGNORE INTO nodes (public_key, name, role) VALUES (?, 'DirIgnore', 'repeater')", pk)
+
+	decoded := `{"name":"DirIgnore","pubKey":"` + pk + `"}`
+	rawFlood2B := "11" + "40" + "aabb" // FLOOD advert, hashSize=2
+	rawDirect0 := "12" + "00" + "aabb" // DIRECT advert, zero-hop (should be ignored)
+
+	payloadType := 4
+	raws := []string{rawFlood2B, rawDirect0, rawFlood2B, rawDirect0, rawFlood2B}
+	for i, raw := range raws {
+		tx := &StoreTx{
+			ID:          9150 + i,
+			RawHex:      raw,
+			Hash:        "dirignore" + strconv.Itoa(i),
+			FirstSeen:   "2024-01-01T0" + strconv.Itoa(i) + ":00:00Z",
+			PayloadType: &payloadType,
+			DecodedJSON: decoded,
+		}
+		store.packets = append(store.packets, tx)
+		store.byPayloadType[4] = append(store.byPayloadType[4], tx)
+	}
+
+	info := store.GetNodeHashSizeInfo()
+	ni := info[pk]
+	if ni == nil {
+		t.Fatal("expected hash info for test node")
+	}
+	if ni.HashSize != 2 {
+		t.Errorf("HashSize=%d, want 2 (direct zero-hop adverts should be ignored)", ni.HashSize)
+	}
+	if ni.Inconsistent {
+		t.Error("expected hash_size_inconsistent=false when direct zero-hop adverts are ignored")
+	}
+	if len(ni.AllSizes) != 1 || !ni.AllSizes[2] {
+		t.Errorf("expected only 2-byte size in AllSizes, got %#v", ni.AllSizes)
+	}
+}
+
+func TestGetNodeHashSizeInfoOnlyDirectZeroHopIgnored(t *testing.T) {
+	db := setupTestDB(t)
+	seedTestData(t, db)
+	store := NewPacketStore(db, nil)
+	if err := store.Load(); err != nil {
+		t.Fatalf("store.Load failed: %v", err)
+	}
+
+	pk := "eeee111122223333444455556666777788889999aaaabbbbccccddddeeee4444"
+	db.conn.Exec("INSERT OR IGNORE INTO nodes (public_key, name, role) VALUES (?, 'OnlyDirect', 'repeater')", pk)
+
+	decoded := `{"name":"OnlyDirect","pubKey":"` + pk + `"}`
+	rawDirect0 := "12" + "00" + "aabb"
+	payloadType := 4
+
+	tx := &StoreTx{
+		ID:          9160,
+		RawHex:      rawDirect0,
+		Hash:        "onlydirect0",
+		FirstSeen:   "2024-01-01T00:00:00Z",
+		PayloadType: &payloadType,
+		DecodedJSON: decoded,
+	}
+	store.packets = append(store.packets, tx)
+	store.byPayloadType[4] = append(store.byPayloadType[4], tx)
+
+	info := store.GetNodeHashSizeInfo()
+	if ni := info[pk]; ni != nil {
+		t.Errorf("expected nil hash info for direct zero-hop only node, got HashSize=%d", ni.HashSize)
+	}
+}
+
+func TestGetNodeHashSizeInfoDirectNonZeroHopCounted(t *testing.T) {
+	// A DIRECT advert with non-zero hop count should NOT be skipped —
+	// only zero-hop DIRECT adverts misreport hash size.
+	db := setupTestDB(t)
+	seedTestData(t, db)
+	store := NewPacketStore(db, nil)
+	if err := store.Load(); err != nil {
+		t.Fatalf("store.Load failed: %v", err)
+	}
+
+	pk := "ffff111122223333444455556666777788889999aaaabbbbccccddddeeee5555"
+	db.conn.Exec("INSERT OR IGNORE INTO nodes (public_key, name, role) VALUES (?, 'DirNonZero', 'repeater')", pk)
+
+	decoded := `{"name":"DirNonZero","pubKey":"` + pk + `"}`
+	// DIRECT advert (route type 2 = 0x02 in bits 0-1), path byte 0x41:
+	//   upper 2 bits = 01 → hash_size = 2, lower 6 bits = 0x01 → hop count 1 (non-zero)
+	rawDirectNonZero := "12" + "41" + "aabb" // header=0x12 (ADVERT|DIRECT), path=0x41
+	payloadType := 4
+
+	tx := &StoreTx{
+		ID:          9170,
+		RawHex:      rawDirectNonZero,
+		Hash:        "dirnonzero0",
+		FirstSeen:   "2024-01-01T00:00:00Z",
+		PayloadType: &payloadType,
+		DecodedJSON: decoded,
+	}
+	store.packets = append(store.packets, tx)
+	store.byPayloadType[4] = append(store.byPayloadType[4], tx)
+
+	info := store.GetNodeHashSizeInfo()
+	ni := info[pk]
+	if ni == nil {
+		t.Fatal("expected hash info for DIRECT non-zero-hop node — it should NOT be skipped")
+	}
+	if ni.HashSize != 2 {
+		t.Errorf("HashSize=%d, want 2 (DIRECT with hop count > 0 should be counted)", ni.HashSize)
+	}
+}
+
 func TestGetNodeHashSizeInfoNoAdverts(t *testing.T) {
 	// A node with no ADVERT packets should not appear in hash size info.
 	db := setupTestDB(t)

cmd/server/store.go

@@ -4537,10 +4537,20 @@ func (s *PacketStore) computeNodeHashSizeInfo() map[string]*hashSizeNodeInfo {
 		if len(tx.RawHex) < 4 {
 			continue
 		}
+		header, err := strconv.ParseUint(tx.RawHex[:2], 16, 8)
+		if err != nil {
+			continue
+		}
+		routeType := int(header & 0x03)
 		pathByte, err := strconv.ParseUint(tx.RawHex[2:4], 16, 8)
 		if err != nil {
 			continue
 		}
+		// DIRECT zero-hop adverts use path byte 0x00 locally and can misreport
+		// multibyte repeater hash mode as 1-byte.
+		if routeType == RouteDirect && (pathByte&0x3F) == 0 {
+			continue
+		}
 		hs := int((pathByte>>6)&0x3) + 1
 
 		var d map[string]interface{}