feat: "multiple words per turn" rule for Russian games

Add a per-game rule chosen on New Game for Russian variants (default off = the
single-word rule; on = standard Scrabble). Off, only the main word along the play
direction is validated and scored; perpendicular cross-words are ignored,
including in robot move generation. The rule rides every create and enqueue
request and joins the matchmaking key, so games and auto-match stay one uniform
path; "Russian-only" is a UI affordance (English always sends standard and shows
no toggle).

- Engine: consume scrabble-solver v1.1.0's PlayOptions{IgnoreCrossWords}, threaded
  through engine.Options.MultipleWordsPerTurn -> playOpts() into validate, score
  and generate.
- Backend: thread the flag through game CreateParams/Game + store (games column),
  lobby InvitationSettings + invitation row, and the matchmaker queue key (variant
  + rule); persisted, so a rebuilt-from-journal game keeps it. Baseline migration
  gains multiple_words_per_turn (DB not versioned); jet regenerated.
- Edge: multiple_words_per_turn added to the EnqueueRequest / CreateInvitationRequest
  FlatBuffers tables (Go + TS regenerated) and threaded through the gateway.
- UI: a "Multiple words per turn" toggle on New Game, shown for Russian variants
  only (auto-match and friend invite), default off; English silently sends standard.
- Tests: backend engine/matchmaker; UI unit (gating) + Playwright e2e (solver
  corner-case + GCG fixtures ship in v1.1.0). Docs + PRERELEASE tracker updated.

backend/internal/engine/game.go

@@ -92,6 +92,12 @@ type Options struct {
 	// DropoutTiles is the disposition of a dropped-out player's tiles in a game
 	// with three or more seats; the zero value removes them from play.
 	DropoutTiles DropoutTiles
+	// MultipleWordsPerTurn selects standard Scrabble when true: every cross-word a
+	// play forms must be a valid word and is scored. When false the game uses the
+	// "single word per turn" rule — only the main word is validated and scored and
+	// perpendicular cross-words are ignored. Callers always set this explicitly; the
+	// zero value (false) is the single-word rule.
+	MultipleWordsPerTurn bool
 }
 
 // Game is the in-memory state of a single match and the pure rules engine over
@@ -104,17 +110,18 @@ type Game struct {
 	variant Variant
 	version string
 
-	board        *board.Board
-	bag          *Bag
-	hands        [][]byte // per player, alphabet-index bytes with blankTile for blanks
-	scores       []int
-	toMove       int
-	scorelessRun int
-	over         bool
-	reason       EndReason
-	resigned     []bool       // per seat; a resigned seat is skipped and cannot win
-	dropoutTiles DropoutTiles // disposition of a resigned seat's tiles
-	log          []MoveRecord
+	board         *board.Board
+	bag           *Bag
+	hands         [][]byte // per player, alphabet-index bytes with blankTile for blanks
+	scores        []int
+	toMove        int
+	scorelessRun  int
+	over          bool
+	reason        EndReason
+	resigned      []bool       // per seat; a resigned seat is skipped and cannot win
+	dropoutTiles  DropoutTiles // disposition of a resigned seat's tiles
+	multipleWords bool         // false = single-word rule (perpendicular cross-words ignored)
+	log           []MoveRecord
 }
 
 // New starts a game described by opts over a dictionary from reg. It resolves
@@ -140,16 +147,17 @@ func New(reg *Registry, opts Options) (*Game, error) {
 
 	rs := solver.Rules()
 	g := &Game{
-		solver:       solver,
-		rules:        rs,
-		variant:      opts.Variant,
-		version:      version,
-		board:        board.New(rs.Rows, rs.Cols),
-		bag:          NewBag(rs, opts.Seed),
-		hands:        make([][]byte, opts.Players),
-		scores:       make([]int, opts.Players),
-		resigned:     make([]bool, opts.Players),
-		dropoutTiles: opts.DropoutTiles,
+		solver:        solver,
+		rules:         rs,
+		variant:       opts.Variant,
+		version:       version,
+		board:         board.New(rs.Rows, rs.Cols),
+		bag:           NewBag(rs, opts.Seed),
+		hands:         make([][]byte, opts.Players),
+		scores:        make([]int, opts.Players),
+		resigned:      make([]bool, opts.Players),
+		dropoutTiles:  opts.DropoutTiles,
+		multipleWords: opts.MultipleWordsPerTurn,
 	}
 	for i := range g.hands {
 		g.hands[i] = g.bag.Draw(rs.RackSize)
@@ -157,6 +165,13 @@ func New(reg *Registry, opts Options) (*Game, error) {
 	return g, nil
 }
 
+// playOpts returns the solver play options for this game's rules. Under the single-word
+// rule (multipleWords false) the solver ignores perpendicular cross-words: only the main
+// word is validated and scored, and move generation is not constrained by cross-words.
+func (g *Game) playOpts() scrabble.PlayOptions {
+	return scrabble.PlayOptions{IgnoreCrossWords: !g.multipleWords}
+}
+
 // Play validates and applies the current player's placement of tiles forming a
 // word in direction dir. It scores the play, refills the rack from the bag,
 // advances the turn and may end the game. It returns ErrTilesNotOnRack when the
@@ -170,7 +185,7 @@ func (g *Game) Play(dir scrabble.Direction, tiles []scrabble.Placement) (MoveRec
 	if err := g.checkHolds(player, placementTiles(tiles)); err != nil {
 		return MoveRecord{}, err
 	}
-	move, err := g.solver.ValidatePlay(g.board, dir, tiles)
+	move, err := g.solver.ValidatePlayOpts(g.board, dir, tiles, g.playOpts())
 	if err != nil {
 		return MoveRecord{}, fmt.Errorf("%w: %v", ErrIllegalPlay, err)
 	}
@@ -279,7 +294,7 @@ func (g *Game) ResignSeat(seat int) (MoveRecord, error) {
 // GenerateMoves returns every legal play for the current player's rack, ranked
 // by descending score. It is empty when the player has no legal play.
 func (g *Game) GenerateMoves() []scrabble.Move {
-	return g.solver.GenerateMoves(g.board, g.rackOf(g.toMove), scrabble.Both)
+	return g.solver.GenerateMovesOpts(g.board, g.rackOf(g.toMove), scrabble.Both, g.playOpts())
 }
 
 // Hint returns the highest-scoring legal play for the current player and true,

backend/internal/engine/singleword_test.go

@@ -0,0 +1,48 @@
+package engine
+
+import "testing"
+
+// TestSingleWordRuleWiring confirms Options.MultipleWordsPerTurn reaches the solver. The
+// single-word game ignores perpendicular cross-words, so move generation from a shared
+// position is a superset of the standard game's; the standard game does not relax them.
+func TestSingleWordRuleWiring(t *testing.T) {
+	const seed = 7
+	mk := func(multipleWords bool) *Game {
+		g, err := New(testReg, Options{
+			Variant:              VariantEnglish,
+			Version:              testVersion,
+			Players:              2,
+			Seed:                 seed,
+			MultipleWordsPerTurn: multipleWords,
+		})
+		if err != nil {
+			t.Fatalf("new game: %v", err)
+		}
+		return g
+	}
+	std, single := mk(true), mk(false)
+	if std.playOpts().IgnoreCrossWords {
+		t.Error("standard game must not ignore cross-words")
+	}
+	if !single.playOpts().IgnoreCrossWords {
+		t.Error("single-word game must ignore cross-words")
+	}
+
+	// Play the same opening (the standard game's top move) in both games, then compare
+	// the next player's candidate moves. Both games share the seed, so the next rack is
+	// identical; relaxed (single-word) generation never drops a legal standard move.
+	hint, ok := std.HintView()
+	if !ok {
+		t.Fatal("opening game has no hint")
+	}
+	if _, err := std.SubmitPlay(hint.Tiles); err != nil {
+		t.Fatalf("standard opening: %v", err)
+	}
+	if _, err := single.SubmitPlay(hint.Tiles); err != nil {
+		t.Fatalf("single-word opening: %v", err)
+	}
+	stdMoves, singleMoves := len(std.GenerateMoves()), len(single.GenerateMoves())
+	if singleMoves < stdMoves {
+		t.Errorf("single-word generation produced %d moves, want >= standard %d", singleMoves, stdMoves)
+	}
+}

backend/internal/game/service.go

@@ -107,11 +107,12 @@ func (svc *Service) Create(ctx context.Context, params CreateParams) (Game, erro
 		seed = svc.rng()
 	}
 	g, err := engine.New(svc.registry, engine.Options{
-		Variant:      params.Variant,
-		Version:      svc.version,
-		Players:      len(params.Seats),
-		Seed:         seed,
-		DropoutTiles: params.DropoutTiles,
+		Variant:              params.Variant,
+		Version:              svc.version,
+		Players:              len(params.Seats),
+		Seed:                 seed,
+		DropoutTiles:         params.DropoutTiles,
+		MultipleWordsPerTurn: params.MultipleWordsPerTurn,
 	})
 	if err != nil {
 		if errors.Is(err, engine.ErrUnknownVariant) || errors.Is(err, engine.ErrUnknownVersion) {
@@ -125,15 +126,16 @@ func (svc *Service) Create(ctx context.Context, params CreateParams) (Game, erro
 		return Game{}, fmt.Errorf("game: new id: %w", err)
 	}
 	ins := gameInsert{
-		id:              id,
-		variant:         params.Variant.String(),
-		dictVersion:     svc.version,
-		seed:            seed,
-		players:         len(params.Seats),
-		turnTimeoutSecs: int(timeout / time.Second),
-		hintsAllowed:    params.HintsAllowed,
-		hintsPerPlayer:  params.HintsPerPlayer,
-		dropoutTiles:    params.DropoutTiles.String(),
+		id:                   id,
+		variant:              params.Variant.String(),
+		dictVersion:          svc.version,
+		seed:                 seed,
+		players:              len(params.Seats),
+		turnTimeoutSecs:      int(timeout / time.Second),
+		hintsAllowed:         params.HintsAllowed,
+		hintsPerPlayer:       params.HintsPerPlayer,
+		dropoutTiles:         params.DropoutTiles.String(),
+		multipleWordsPerTurn: params.MultipleWordsPerTurn,
 	}
 	if err := svc.store.CreateGame(ctx, ins, params.Seats); err != nil {
 		return Game{}, err
@@ -934,11 +936,12 @@ func (svc *Service) replay(ctx context.Context, pre Game) (*engine.Game, error)
 		return nil, err
 	}
 	g, err := engine.New(svc.registry, engine.Options{
-		Variant:      pre.Variant,
-		Version:      pre.DictVersion,
-		Players:      pre.Players,
-		Seed:         seed,
-		DropoutTiles: pre.DropoutTiles,
+		Variant:              pre.Variant,
+		Version:              pre.DictVersion,
+		Players:              pre.Players,
+		Seed:                 seed,
+		DropoutTiles:         pre.DropoutTiles,
+		MultipleWordsPerTurn: pre.MultipleWordsPerTurn,
 	})
 	if err != nil {
 		return nil, err

backend/internal/game/store.go

@@ -38,6 +38,8 @@ type gameInsert struct {
 	hintsAllowed    bool
 	hintsPerPlayer  int
 	dropoutTiles    string
+	// multipleWordsPerTurn false selects the single-word rule for the game.
+	multipleWordsPerTurn bool
 }
 
 // statDelta is one account's contribution to its statistics on a game finish.
@@ -92,8 +94,8 @@ func (s *Store) CreateGame(ctx context.Context, ins gameInsert, seats []uuid.UUI
 		gi := table.Games.INSERT(
 			table.Games.GameID, table.Games.Variant, table.Games.DictVersion, table.Games.Seed,
 			table.Games.Players, table.Games.TurnTimeoutSecs, table.Games.HintsAllowed, table.Games.HintsPerPlayer,
-			table.Games.DropoutTiles,
-		).VALUES(ins.id, ins.variant, ins.dictVersion, ins.seed, ins.players, ins.turnTimeoutSecs, ins.hintsAllowed, ins.hintsPerPlayer, ins.dropoutTiles)
+			table.Games.DropoutTiles, table.Games.MultipleWordsPerTurn,
+		).VALUES(ins.id, ins.variant, ins.dictVersion, ins.seed, ins.players, ins.turnTimeoutSecs, ins.hintsAllowed, ins.hintsPerPlayer, ins.dropoutTiles, ins.multipleWordsPerTurn)
 		if _, err := gi.ExecContext(ctx, tx); err != nil {
 			return fmt.Errorf("insert game: %w", err)
 		}
@@ -761,6 +763,7 @@ func projectGame(g model.Games, seats []model.GamePlayers) (Game, error) {
 		CreatedAt:      g.CreatedAt,
 		UpdatedAt:      g.UpdatedAt,
 	}
+	out.MultipleWordsPerTurn = g.MultipleWordsPerTurn
 	if g.EndReason != nil {
 		out.EndReason = *g.EndReason
 	}

backend/internal/game/types.go

@@ -80,6 +80,9 @@ type CreateParams struct {
 	HintsPerPlayer int                 // starting per-seat hint allowance
 	DropoutTiles   engine.DropoutTiles // disposition of a dropped-out seat's tiles (3+ players); zero → remove
 	Seed           int64               // zero → a random seed is chosen
+	// MultipleWordsPerTurn true selects standard Scrabble; false the single-word rule —
+	// only the main word is validated and scored. Russian games default to false.
+	MultipleWordsPerTurn bool
 }
 
 // Game is the persisted state of a match: the games row joined with its seats.
@@ -101,6 +104,8 @@ type Game struct {
 	CreatedAt      time.Time
 	UpdatedAt      time.Time
 	FinishedAt     *time.Time
+	// MultipleWordsPerTurn true selects standard Scrabble; false the single-word rule.
+	MultipleWordsPerTurn bool
 }
 
 // Seat is one player's standing in a game.

backend/internal/inttest/lobby_test.go

@@ -35,14 +35,14 @@ func TestMatchmakingPairsAndStartsGame(t *testing.T) {
 	mm := newMatchmaker(t, newRobotService(t, newGameService()), 10*time.Second)
 	a, b := provisionAccount(t), provisionAccount(t)
 
-	r1, err := mm.Enqueue(ctx, a, engine.VariantEnglish)
+	r1, err := mm.Enqueue(ctx, a, engine.VariantEnglish, true)
 	if err != nil {
 		t.Fatalf("enqueue a: %v", err)
 	}
 	if r1.Matched {
 		t.Fatal("first enqueue must wait")
 	}
-	r2, err := mm.Enqueue(ctx, b, engine.VariantEnglish)
+	r2, err := mm.Enqueue(ctx, b, engine.VariantEnglish, true)
 	if err != nil {
 		t.Fatalf("enqueue b: %v", err)
 	}

backend/internal/inttest/robot_test.go

@@ -150,7 +150,7 @@ func TestMatchmakerSubstitutesRobotEndToEnd(t *testing.T) {
 	human := provisionAccount(t)
 
 	before := time.Now()
-	r, err := mm.Enqueue(ctx, human, engine.VariantEnglish)
+	r, err := mm.Enqueue(ctx, human, engine.VariantEnglish, true)
 	if err != nil {
 		t.Fatalf("enqueue: %v", err)
 	}

backend/internal/lobby/invitations.go

@@ -49,6 +49,8 @@ type InvitationSettings struct {
 	HintsAllowed   bool
 	HintsPerPlayer int
 	DropoutTiles   engine.DropoutTiles
+	// MultipleWordsPerTurn true selects standard Scrabble; false the single-word rule.
+	MultipleWordsPerTurn bool
 }
 
 // Invitee is one invited player's seat and response.
@@ -214,14 +216,15 @@ func (svc *InvitationService) CreateInvitation(ctx context.Context, inviterID uu
 		return Invitation{}, fmt.Errorf("lobby: new invitation id: %w", err)
 	}
 	ins := invitationInsert{
-		id:              id,
-		inviterID:       inviterID,
-		variant:         settings.Variant.String(),
-		turnTimeoutSecs: int(settings.TurnTimeout / time.Second),
-		hintsAllowed:    settings.HintsAllowed,
-		hintsPerPlayer:  settings.HintsPerPlayer,
-		dropoutTiles:    settings.DropoutTiles.String(),
-		expiresAt:       svc.now().Add(invitationTTL),
+		id:                   id,
+		inviterID:            inviterID,
+		variant:              settings.Variant.String(),
+		turnTimeoutSecs:      int(settings.TurnTimeout / time.Second),
+		hintsAllowed:         settings.HintsAllowed,
+		hintsPerPlayer:       settings.HintsPerPlayer,
+		dropoutTiles:         settings.DropoutTiles.String(),
+		multipleWordsPerTurn: settings.MultipleWordsPerTurn,
+		expiresAt:            svc.now().Add(invitationTTL),
 	}
 	if err := svc.store.insertInvitation(ctx, ins, inviteeIDs); err != nil {
 		return Invitation{}, err
@@ -265,12 +268,13 @@ func (svc *InvitationService) startGame(ctx context.Context, invitationID uuid.U
 		seats[iv.Seat] = iv.AccountID
 	}
 	g, err := svc.games.Create(ctx, game.CreateParams{
-		Variant:        inv.Settings.Variant,
-		Seats:          seats,
-		TurnTimeout:    inv.Settings.TurnTimeout,
-		HintsAllowed:   inv.Settings.HintsAllowed,
-		HintsPerPlayer: inv.Settings.HintsPerPlayer,
-		DropoutTiles:   inv.Settings.DropoutTiles,
+		Variant:              inv.Settings.Variant,
+		Seats:                seats,
+		TurnTimeout:          inv.Settings.TurnTimeout,
+		HintsAllowed:         inv.Settings.HintsAllowed,
+		HintsPerPlayer:       inv.Settings.HintsPerPlayer,
+		DropoutTiles:         inv.Settings.DropoutTiles,
+		MultipleWordsPerTurn: inv.Settings.MultipleWordsPerTurn,
 	})
 	if err != nil {
 		return err
@@ -322,6 +326,8 @@ type invitationInsert struct {
 	hintsPerPlayer  int
 	dropoutTiles    string
 	expiresAt       time.Time
+	// multipleWordsPerTurn false selects the single-word rule.
+	multipleWordsPerTurn bool
 }
 
 // respondResult reports the state after an invitee response.
@@ -335,8 +341,8 @@ func (s *Store) insertInvitation(ctx context.Context, ins invitationInsert, invi
 		ii := table.GameInvitations.INSERT(
 			table.GameInvitations.InvitationID, table.GameInvitations.InviterID, table.GameInvitations.Variant,
 			table.GameInvitations.TurnTimeoutSecs, table.GameInvitations.HintsAllowed, table.GameInvitations.HintsPerPlayer,
-			table.GameInvitations.DropoutTiles, table.GameInvitations.ExpiresAt,
-		).VALUES(ins.id, ins.inviterID, ins.variant, ins.turnTimeoutSecs, ins.hintsAllowed, ins.hintsPerPlayer, ins.dropoutTiles, ins.expiresAt)
+			table.GameInvitations.DropoutTiles, table.GameInvitations.MultipleWordsPerTurn, table.GameInvitations.ExpiresAt,
+		).VALUES(ins.id, ins.inviterID, ins.variant, ins.turnTimeoutSecs, ins.hintsAllowed, ins.hintsPerPlayer, ins.dropoutTiles, ins.multipleWordsPerTurn, ins.expiresAt)
 		if _, err := ii.ExecContext(ctx, tx); err != nil {
 			return fmt.Errorf("insert invitation: %w", err)
 		}
@@ -377,11 +383,12 @@ func (s *Store) loadInvitation(ctx context.Context, id uuid.UUID) (Invitation, e
 		ID:        row.InvitationID,
 		InviterID: row.InviterID,
 		Settings: InvitationSettings{
-			Variant:        variant,
-			TurnTimeout:    time.Duration(row.TurnTimeoutSecs) * time.Second,
-			HintsAllowed:   row.HintsAllowed,
-			HintsPerPlayer: int(row.HintsPerPlayer),
-			DropoutTiles:   dropout,
+			Variant:              variant,
+			TurnTimeout:          time.Duration(row.TurnTimeoutSecs) * time.Second,
+			HintsAllowed:         row.HintsAllowed,
+			HintsPerPlayer:       int(row.HintsPerPlayer),
+			DropoutTiles:         dropout,
+			MultipleWordsPerTurn: row.MultipleWordsPerTurn,
 		},
 		Status:    row.Status,
 		GameID:    row.GameID,

backend/internal/lobby/matchmaker.go

@@ -14,6 +14,14 @@ import (
 	"scrabble/backend/internal/notify"
 )
 
+// matchKey buckets the auto-match pool: two players are paired only when they chose
+// the same variant and the same per-turn word rule (multipleWords), so a game always
+// starts under a rule both players asked for.
+type matchKey struct {
+	variant       engine.Variant
+	multipleWords bool
+}
+
 // Matchmaker is the in-memory auto-match pool: a FIFO queue per variant that pairs
 // the next two humans into a two-player game, or — when no human arrives within
 // the wait window — substitutes a robot. It holds no database state and is lost on
@@ -35,8 +43,8 @@ type Matchmaker struct {
 	log       *zap.Logger
 
 	mu           sync.Mutex
-	queues       map[engine.Variant][]uuid.UUID
-	queued       map[uuid.UUID]engine.Variant
+	queues       map[matchKey][]uuid.UUID
+	queued       map[uuid.UUID]matchKey
 	waitingSince map[uuid.UUID]time.Time
 	results      map[uuid.UUID]game.Game
 	rng          *rand.Rand
@@ -55,8 +63,8 @@ func NewMatchmaker(games GameCreator, robots RobotProvider, waitDelay time.Durat
 		clock:        func() time.Time { return time.Now().UTC() },
 		pub:          notify.Nop{},
 		log:          log,
-		queues:       make(map[engine.Variant][]uuid.UUID),
-		queued:       make(map[uuid.UUID]engine.Variant),
+		queues:       make(map[matchKey][]uuid.UUID),
+		queued:       make(map[uuid.UUID]matchKey),
 		waitingSince: make(map[uuid.UUID]time.Time),
 		results:      make(map[uuid.UUID]game.Game),
 		rng:          rand.New(rand.NewSource(time.Now().UnixNano())),
@@ -101,34 +109,36 @@ type EnqueueResult struct {
 	Game    game.Game
 }
 
-// Enqueue joins accountID to the variant pool. If an opponent already waits, the
-// two are paired (seat order randomised for first-move fairness) and a game starts
-// immediately; otherwise the account waits, and a later pairing or robot
-// substitution is delivered through Poll. An account already waiting in any pool
-// gets ErrAlreadyQueued.
-func (m *Matchmaker) Enqueue(ctx context.Context, accountID uuid.UUID, variant engine.Variant) (EnqueueResult, error) {
+// Enqueue joins accountID to the auto-match pool for variant under the chosen
+// per-turn word rule (multipleWords). If an opponent already waits for the same
+// variant and rule, the two are paired (seat order randomised for first-move
+// fairness) and a game starts immediately; otherwise the account waits, and a later
+// pairing or robot substitution is delivered through Poll. An account already waiting
+// in any pool gets ErrAlreadyQueued.
+func (m *Matchmaker) Enqueue(ctx context.Context, accountID uuid.UUID, variant engine.Variant, multipleWords bool) (EnqueueResult, error) {
+	key := matchKey{variant: variant, multipleWords: multipleWords}
 	m.mu.Lock()
 	if _, ok := m.queued[accountID]; ok {
 		m.mu.Unlock()
 		return EnqueueResult{}, ErrAlreadyQueued
 	}
-	q := m.queues[variant]
+	q := m.queues[key]
 	if len(q) == 0 {
-		m.queues[variant] = append(q, accountID)
-		m.queued[accountID] = variant
+		m.queues[key] = append(q, accountID)
+		m.queued[accountID] = key
 		m.waitingSince[accountID] = m.clock()
 		m.mu.Unlock()
 		return EnqueueResult{}, nil
 	}
 	opponent := q[0]
-	m.removeLocked(opponent, variant)
+	m.removeLocked(opponent, key)
 	seats := []uuid.UUID{opponent, accountID}
 	if m.rng.Intn(2) == 0 {
 		seats[0], seats[1] = seats[1], seats[0]
 	}
 	m.mu.Unlock()
 
-	g, err := m.games.Create(ctx, autoMatchParams(variant, seats))
+	g, err := m.games.Create(ctx, autoMatchParams(key, seats))
 	if err != nil {
 		return EnqueueResult{}, err
 	}
@@ -161,19 +171,21 @@ func (m *Matchmaker) Cancel(_ context.Context, accountID uuid.UUID) bool {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	delete(m.results, accountID)
-	variant, ok := m.queued[accountID]
+	key, ok := m.queued[accountID]
 	if !ok {
 		return false
 	}
-	m.removeLocked(accountID, variant)
+	m.removeLocked(accountID, key)
 	return true
 }
 
-// QueueLen returns the number of accounts waiting in the variant pool.
+// QueueLen returns the number of accounts waiting in the variant pool, summed across
+// both per-turn word rules.
 func (m *Matchmaker) QueueLen(variant engine.Variant) int {
 	m.mu.Lock()
 	defer m.mu.Unlock()
-	return len(m.queues[variant])
+	return len(m.queues[matchKey{variant: variant, multipleWords: false}]) +
+		len(m.queues[matchKey{variant: variant, multipleWords: true}])
 }
 
 // RunReaper substitutes a robot for any player that has waited past waitDelay,
@@ -198,9 +210,9 @@ func (m *Matchmaker) RunReaper(ctx context.Context, interval time.Duration) {
 // momentarily empty pool just defers substitution to a later tick.
 func (m *Matchmaker) Reap(ctx context.Context, now time.Time) {
 	type sub struct {
-		human   uuid.UUID
-		variant engine.Variant
-		seats   []uuid.UUID
+		human uuid.UUID
+		key   matchKey
+		seats []uuid.UUID
 	}
 	m.mu.Lock()
 	var due []uuid.UUID
@@ -211,23 +223,23 @@ func (m *Matchmaker) Reap(ctx context.Context, now time.Time) {
 	}
 	var subs []sub
 	for _, acc := range due {
-		variant := m.queued[acc]
-		robotID, err := m.robots.Pick(variant)
+		key := m.queued[acc]
+		robotID, err := m.robots.Pick(key.variant)
 		if err != nil {
 			m.log.Warn("robot substitution deferred", zap.Error(err))
 			continue
 		}
-		m.removeLocked(acc, variant)
+		m.removeLocked(acc, key)
 		seats := []uuid.UUID{acc, robotID}
 		if m.rng.Intn(2) == 0 {
 			seats[0], seats[1] = seats[1], seats[0]
 		}
-		subs = append(subs, sub{human: acc, variant: variant, seats: seats})
+		subs = append(subs, sub{human: acc, key: key, seats: seats})
 	}
 	m.mu.Unlock()
 
 	for _, s := range subs {
-		g, err := m.games.Create(ctx, autoMatchParams(s.variant, s.seats))
+		g, err := m.games.Create(ctx, autoMatchParams(s.key, s.seats))
 		if err != nil {
 			m.log.Warn("robot substitution failed", zap.String("human", s.human.String()), zap.Error(err))
 			continue
@@ -241,13 +253,13 @@ func (m *Matchmaker) Reap(ctx context.Context, now time.Time) {
 
 // removeLocked drops accountID from the queue, the queued index and the waiting
 // clock. The caller holds m.mu.
-func (m *Matchmaker) removeLocked(accountID uuid.UUID, variant engine.Variant) {
+func (m *Matchmaker) removeLocked(accountID uuid.UUID, key matchKey) {
 	delete(m.queued, accountID)
 	delete(m.waitingSince, accountID)
-	q := m.queues[variant]
+	q := m.queues[key]
 	for i, id := range q {
 		if id == accountID {
-			m.queues[variant] = append(q[:i], q[i+1:]...)
+			m.queues[key] = append(q[:i], q[i+1:]...)
 			break
 		}
 	}
@@ -255,12 +267,13 @@ func (m *Matchmaker) removeLocked(accountID uuid.UUID, variant engine.Variant) {
 
 // autoMatchParams builds the create parameters for a two-player auto-match with
 // the casual defaults.
-func autoMatchParams(variant engine.Variant, seats []uuid.UUID) game.CreateParams {
+func autoMatchParams(key matchKey, seats []uuid.UUID) game.CreateParams {
 	return game.CreateParams{
-		Variant:        variant,
-		Seats:          seats,
-		TurnTimeout:    game.DefaultTurnTimeout,
-		HintsAllowed:   autoMatchHintsAllowed,
-		HintsPerPlayer: autoMatchHintsPerPlayer,
+		Variant:              key.variant,
+		Seats:                seats,
+		TurnTimeout:          game.DefaultTurnTimeout,
+		HintsAllowed:         autoMatchHintsAllowed,
+		HintsPerPlayer:       autoMatchHintsPerPlayer,
+		MultipleWordsPerTurn: key.multipleWords,
 	}
 }

backend/internal/lobby/matchmaker_test.go

@@ -80,7 +80,7 @@ func TestMatchmakerPairsTwoHumans(t *testing.T) {
 	ctx := context.Background()
 	a, b := uuid.New(), uuid.New()
 
-	r1, err := mm.Enqueue(ctx, a, engine.VariantEnglish)
+	r1, err := mm.Enqueue(ctx, a, engine.VariantEnglish, true)
 	if err != nil {
 		t.Fatalf("enqueue a: %v", err)
 	}
@@ -91,7 +91,7 @@ func TestMatchmakerPairsTwoHumans(t *testing.T) {
 		t.Fatalf("queue len = %d, want 1", mm.QueueLen(engine.VariantEnglish))
 	}
 
-	r2, err := mm.Enqueue(ctx, b, engine.VariantEnglish)
+	r2, err := mm.Enqueue(ctx, b, engine.VariantEnglish, true)
 	if err != nil {
 		t.Fatalf("enqueue b: %v", err)
 	}
@@ -129,10 +129,10 @@ func TestMatchmakerAlreadyQueued(t *testing.T) {
 	mm := newTestMatchmaker(&fakeCreator{}, uuid.New())
 	ctx := context.Background()
 	a := uuid.New()
-	if _, err := mm.Enqueue(ctx, a, engine.VariantEnglish); err != nil {
+	if _, err := mm.Enqueue(ctx, a, engine.VariantEnglish, true); err != nil {
 		t.Fatalf("enqueue: %v", err)
 	}
-	if _, err := mm.Enqueue(ctx, a, engine.VariantEnglish); !errors.Is(err, ErrAlreadyQueued) {
+	if _, err := mm.Enqueue(ctx, a, engine.VariantEnglish, true); !errors.Is(err, ErrAlreadyQueued) {
 		t.Fatalf("second enqueue err = %v, want ErrAlreadyQueued", err)
 	}
 }
@@ -141,7 +141,7 @@ func TestMatchmakerCancel(t *testing.T) {
 	mm := newTestMatchmaker(&fakeCreator{}, uuid.New())
 	ctx := context.Background()
 	a := uuid.New()
-	if _, err := mm.Enqueue(ctx, a, engine.VariantEnglish); err != nil {
+	if _, err := mm.Enqueue(ctx, a, engine.VariantEnglish, true); err != nil {
 		t.Fatalf("enqueue: %v", err)
 	}
 	if !mm.Cancel(ctx, a) {
@@ -159,10 +159,10 @@ func TestMatchmakerVariantsAreSeparate(t *testing.T) {
 	creator := &fakeCreator{}
 	mm := newTestMatchmaker(creator, uuid.New())
 	ctx := context.Background()
-	if _, err := mm.Enqueue(ctx, uuid.New(), engine.VariantEnglish); err != nil {
+	if _, err := mm.Enqueue(ctx, uuid.New(), engine.VariantEnglish, true); err != nil {
 		t.Fatalf("enqueue en: %v", err)
 	}
-	if _, err := mm.Enqueue(ctx, uuid.New(), engine.VariantRussianScrabble); err != nil {
+	if _, err := mm.Enqueue(ctx, uuid.New(), engine.VariantRussianScrabble, true); err != nil {
 		t.Fatalf("enqueue ru: %v", err)
 	}
 	if len(creator.created) != 0 {
@@ -179,7 +179,7 @@ func TestMatchmakerFIFO(t *testing.T) {
 	ctx := context.Background()
 	a, b, c := uuid.New(), uuid.New(), uuid.New()
 	for _, id := range []uuid.UUID{a, b, c} {
-		if _, err := mm.Enqueue(ctx, id, engine.VariantEnglish); err != nil {
+		if _, err := mm.Enqueue(ctx, id, engine.VariantEnglish, true); err != nil {
 			t.Fatalf("enqueue %s: %v", id, err)
 		}
 	}
@@ -204,7 +204,7 @@ func TestMatchmakerReaperSubstitutesRobot(t *testing.T) {
 	ctx := context.Background()
 	a := uuid.New()
 
-	if _, err := mm.Enqueue(ctx, a, engine.VariantEnglish); err != nil {
+	if _, err := mm.Enqueue(ctx, a, engine.VariantEnglish, true); err != nil {
 		t.Fatalf("enqueue: %v", err)
 	}
 
@@ -237,7 +237,7 @@ func TestMatchmakerReaperSkipsCancelled(t *testing.T) {
 	ctx := context.Background()
 	a := uuid.New()
 
-	if _, err := mm.Enqueue(ctx, a, engine.VariantEnglish); err != nil {
+	if _, err := mm.Enqueue(ctx, a, engine.VariantEnglish, true); err != nil {
 		t.Fatalf("enqueue: %v", err)
 	}
 	mm.Cancel(ctx, a)
@@ -258,7 +258,7 @@ func TestMatchmakerCancelClearsPendingResult(t *testing.T) {
 	ctx := context.Background()
 	a := uuid.New()
 
-	if _, err := mm.Enqueue(ctx, a, engine.VariantEnglish); err != nil {
+	if _, err := mm.Enqueue(ctx, a, engine.VariantEnglish, true); err != nil {
 		t.Fatalf("enqueue: %v", err)
 	}
 	mm.Reap(ctx, base.Add(testWaitDelay+time.Second)) // substitution stores a pending result
@@ -276,7 +276,7 @@ func TestMatchmakerReaperDefersWithoutRobot(t *testing.T) {
 	ctx := context.Background()
 	a := uuid.New()
 
-	if _, err := mm.Enqueue(ctx, a, engine.VariantEnglish); err != nil {
+	if _, err := mm.Enqueue(ctx, a, engine.VariantEnglish, true); err != nil {
 		t.Fatalf("enqueue: %v", err)
 	}
 	mm.Reap(ctx, base.Add(testWaitDelay+time.Second))
@@ -287,3 +287,57 @@ func TestMatchmakerReaperDefersWithoutRobot(t *testing.T) {
 		t.Errorf("waiter must stay queued when substitution is deferred; len %d", mm.QueueLen(engine.VariantEnglish))
 	}
 }
+
+// TestMatchmakerRulesAreSeparate confirms two players who chose the same variant but a
+// different per-turn word rule are not paired, and that the rule reaches the started game.
+func TestMatchmakerRulesAreSeparate(t *testing.T) {
+	creator := &fakeCreator{}
+	mm := newTestMatchmaker(creator, uuid.New())
+	ctx := context.Background()
+
+	// Same variant, opposite rules: they must not match.
+	if _, err := mm.Enqueue(ctx, uuid.New(), engine.VariantRussianScrabble, false); err != nil {
+		t.Fatalf("enqueue single-word: %v", err)
+	}
+	if _, err := mm.Enqueue(ctx, uuid.New(), engine.VariantRussianScrabble, true); err != nil {
+		t.Fatalf("enqueue standard: %v", err)
+	}
+	if len(creator.created) != 0 {
+		t.Fatalf("different rules must not match; created %d", len(creator.created))
+	}
+
+	// A second single-word player pairs with the first; the game carries the rule.
+	r, err := mm.Enqueue(ctx, uuid.New(), engine.VariantRussianScrabble, false)
+	if err != nil {
+		t.Fatalf("enqueue single-word opponent: %v", err)
+	}
+	if !r.Matched {
+		t.Fatal("same variant and rule must match")
+	}
+	if len(creator.created) != 1 {
+		t.Fatalf("created %d games, want 1", len(creator.created))
+	}
+	if creator.created[0].MultipleWordsPerTurn {
+		t.Error("single-word match must create a game with MultipleWordsPerTurn=false")
+	}
+}
+
+// TestMatchmakerReaperKeepsRule confirms a robot substitution carries the waiter's rule.
+func TestMatchmakerReaperKeepsRule(t *testing.T) {
+	creator := &fakeCreator{}
+	mm := newTestMatchmaker(creator, uuid.New())
+	base := time.Now()
+	mm.clock = func() time.Time { return base }
+	ctx := context.Background()
+
+	if _, err := mm.Enqueue(ctx, uuid.New(), engine.VariantRussianScrabble, false); err != nil {
+		t.Fatalf("enqueue: %v", err)
+	}
+	mm.Reap(ctx, base.Add(testWaitDelay+time.Second))
+	if len(creator.created) != 1 {
+		t.Fatalf("created %d games, want 1", len(creator.created))
+	}
+	if creator.created[0].MultipleWordsPerTurn {
+		t.Error("robot substitution must keep the waiter's single-word rule")
+	}
+}

backend/internal/postgres/jet/backend/model/game_invitations.go

@@ -13,16 +13,17 @@ import (
 )
 
 type GameInvitations struct {
-	InvitationID    uuid.UUID `sql:"primary_key"`
-	InviterID       uuid.UUID
-	Variant         string
-	TurnTimeoutSecs int32
-	HintsAllowed    bool
-	HintsPerPlayer  int16
-	DropoutTiles    string
-	Status          string
-	GameID          *uuid.UUID
-	ExpiresAt       time.Time
-	CreatedAt       time.Time
-	UpdatedAt       time.Time
+	InvitationID         uuid.UUID `sql:"primary_key"`
+	InviterID            uuid.UUID
+	Variant              string
+	TurnTimeoutSecs      int32
+	HintsAllowed         bool
+	HintsPerPlayer       int16
+	DropoutTiles         string
+	MultipleWordsPerTurn bool
+	Status               string
+	GameID               *uuid.UUID
+	ExpiresAt            time.Time
+	CreatedAt            time.Time
+	UpdatedAt            time.Time
 }

backend/internal/postgres/jet/backend/model/games.go

@@ -13,21 +13,22 @@ import (
 )
 
 type Games struct {
-	GameID          uuid.UUID `sql:"primary_key"`
-	Variant         string
-	DictVersion     string
-	Seed            int64
-	Status          string
-	Players         int16
-	ToMove          int16
-	TurnStartedAt   time.Time
-	TurnTimeoutSecs int32
-	HintsAllowed    bool
-	HintsPerPlayer  int16
-	MoveCount       int32
-	EndReason       *string
-	CreatedAt       time.Time
-	UpdatedAt       time.Time
-	FinishedAt      *time.Time
-	DropoutTiles    string
+	GameID               uuid.UUID `sql:"primary_key"`
+	Variant              string
+	DictVersion          string
+	Seed                 int64
+	Status               string
+	Players              int16
+	ToMove               int16
+	TurnStartedAt        time.Time
+	TurnTimeoutSecs      int32
+	HintsAllowed         bool
+	HintsPerPlayer       int16
+	MoveCount            int32
+	EndReason            *string
+	CreatedAt            time.Time
+	UpdatedAt            time.Time
+	FinishedAt           *time.Time
+	DropoutTiles         string
+	MultipleWordsPerTurn bool
 }

backend/internal/postgres/jet/backend/table/game_invitations.go

@@ -17,18 +17,19 @@ type gameInvitationsTable struct {
 	postgres.Table
 
 	// Columns
-	InvitationID    postgres.ColumnString
-	InviterID       postgres.ColumnString
-	Variant         postgres.ColumnString
-	TurnTimeoutSecs postgres.ColumnInteger
-	HintsAllowed    postgres.ColumnBool
-	HintsPerPlayer  postgres.ColumnInteger
-	DropoutTiles    postgres.ColumnString
-	Status          postgres.ColumnString
-	GameID          postgres.ColumnString
-	ExpiresAt       postgres.ColumnTimestampz
-	CreatedAt       postgres.ColumnTimestampz
-	UpdatedAt       postgres.ColumnTimestampz
+	InvitationID         postgres.ColumnString
+	InviterID            postgres.ColumnString
+	Variant              postgres.ColumnString
+	TurnTimeoutSecs      postgres.ColumnInteger
+	HintsAllowed         postgres.ColumnBool
+	HintsPerPlayer       postgres.ColumnInteger
+	DropoutTiles         postgres.ColumnString
+	MultipleWordsPerTurn postgres.ColumnBool
+	Status               postgres.ColumnString
+	GameID               postgres.ColumnString
+	ExpiresAt            postgres.ColumnTimestampz
+	CreatedAt            postgres.ColumnTimestampz
+	UpdatedAt            postgres.ColumnTimestampz
 
 	AllColumns     postgres.ColumnList
 	MutableColumns postgres.ColumnList
@@ -70,39 +71,41 @@ func newGameInvitationsTable(schemaName, tableName, alias string) *GameInvitatio
 
 func newGameInvitationsTableImpl(schemaName, tableName, alias string) gameInvitationsTable {
 	var (
-		InvitationIDColumn    = postgres.StringColumn("invitation_id")
-		InviterIDColumn       = postgres.StringColumn("inviter_id")
-		VariantColumn         = postgres.StringColumn("variant")
-		TurnTimeoutSecsColumn = postgres.IntegerColumn("turn_timeout_secs")
-		HintsAllowedColumn    = postgres.BoolColumn("hints_allowed")
-		HintsPerPlayerColumn  = postgres.IntegerColumn("hints_per_player")
-		DropoutTilesColumn    = postgres.StringColumn("dropout_tiles")
-		StatusColumn          = postgres.StringColumn("status")
-		GameIDColumn          = postgres.StringColumn("game_id")
-		ExpiresAtColumn       = postgres.TimestampzColumn("expires_at")
-		CreatedAtColumn       = postgres.TimestampzColumn("created_at")
-		UpdatedAtColumn       = postgres.TimestampzColumn("updated_at")
-		allColumns            = postgres.ColumnList{InvitationIDColumn, InviterIDColumn, VariantColumn, TurnTimeoutSecsColumn, HintsAllowedColumn, HintsPerPlayerColumn, DropoutTilesColumn, StatusColumn, GameIDColumn, ExpiresAtColumn, CreatedAtColumn, UpdatedAtColumn}
-		mutableColumns        = postgres.ColumnList{InviterIDColumn, VariantColumn, TurnTimeoutSecsColumn, HintsAllowedColumn, HintsPerPlayerColumn, DropoutTilesColumn, StatusColumn, GameIDColumn, ExpiresAtColumn, CreatedAtColumn, UpdatedAtColumn}
-		defaultColumns        = postgres.ColumnList{HintsAllowedColumn, HintsPerPlayerColumn, DropoutTilesColumn, StatusColumn, CreatedAtColumn, UpdatedAtColumn}
+		InvitationIDColumn         = postgres.StringColumn("invitation_id")
+		InviterIDColumn            = postgres.StringColumn("inviter_id")
+		VariantColumn              = postgres.StringColumn("variant")
+		TurnTimeoutSecsColumn      = postgres.IntegerColumn("turn_timeout_secs")
+		HintsAllowedColumn         = postgres.BoolColumn("hints_allowed")
+		HintsPerPlayerColumn       = postgres.IntegerColumn("hints_per_player")
+		DropoutTilesColumn         = postgres.StringColumn("dropout_tiles")
+		MultipleWordsPerTurnColumn = postgres.BoolColumn("multiple_words_per_turn")
+		StatusColumn               = postgres.StringColumn("status")
+		GameIDColumn               = postgres.StringColumn("game_id")
+		ExpiresAtColumn            = postgres.TimestampzColumn("expires_at")
+		CreatedAtColumn            = postgres.TimestampzColumn("created_at")
+		UpdatedAtColumn            = postgres.TimestampzColumn("updated_at")
+		allColumns                 = postgres.ColumnList{InvitationIDColumn, InviterIDColumn, VariantColumn, TurnTimeoutSecsColumn, HintsAllowedColumn, HintsPerPlayerColumn, DropoutTilesColumn, MultipleWordsPerTurnColumn, StatusColumn, GameIDColumn, ExpiresAtColumn, CreatedAtColumn, UpdatedAtColumn}
+		mutableColumns             = postgres.ColumnList{InviterIDColumn, VariantColumn, TurnTimeoutSecsColumn, HintsAllowedColumn, HintsPerPlayerColumn, DropoutTilesColumn, MultipleWordsPerTurnColumn, StatusColumn, GameIDColumn, ExpiresAtColumn, CreatedAtColumn, UpdatedAtColumn}
+		defaultColumns             = postgres.ColumnList{HintsAllowedColumn, HintsPerPlayerColumn, DropoutTilesColumn, MultipleWordsPerTurnColumn, StatusColumn, CreatedAtColumn, UpdatedAtColumn}
 	)
 
 	return gameInvitationsTable{
 		Table: postgres.NewTable(schemaName, tableName, alias, allColumns...),
 
 		//Columns
-		InvitationID:    InvitationIDColumn,
-		InviterID:       InviterIDColumn,
-		Variant:         VariantColumn,
-		TurnTimeoutSecs: TurnTimeoutSecsColumn,
-		HintsAllowed:    HintsAllowedColumn,
-		HintsPerPlayer:  HintsPerPlayerColumn,
-		DropoutTiles:    DropoutTilesColumn,
-		Status:          StatusColumn,
-		GameID:          GameIDColumn,
-		ExpiresAt:       ExpiresAtColumn,
-		CreatedAt:       CreatedAtColumn,
-		UpdatedAt:       UpdatedAtColumn,
+		InvitationID:         InvitationIDColumn,
+		InviterID:            InviterIDColumn,
+		Variant:              VariantColumn,
+		TurnTimeoutSecs:      TurnTimeoutSecsColumn,
+		HintsAllowed:         HintsAllowedColumn,
+		HintsPerPlayer:       HintsPerPlayerColumn,
+		DropoutTiles:         DropoutTilesColumn,
+		MultipleWordsPerTurn: MultipleWordsPerTurnColumn,
+		Status:               StatusColumn,
+		GameID:               GameIDColumn,
+		ExpiresAt:            ExpiresAtColumn,
+		CreatedAt:            CreatedAtColumn,
+		UpdatedAt:            UpdatedAtColumn,
 
 		AllColumns:     allColumns,
 		MutableColumns: mutableColumns,

backend/internal/postgres/jet/backend/table/games.go

@@ -17,23 +17,24 @@ type gamesTable struct {
 	postgres.Table
 
 	// Columns
-	GameID          postgres.ColumnString
-	Variant         postgres.ColumnString
-	DictVersion     postgres.ColumnString
-	Seed            postgres.ColumnInteger
-	Status          postgres.ColumnString
-	Players         postgres.ColumnInteger
-	ToMove          postgres.ColumnInteger
-	TurnStartedAt   postgres.ColumnTimestampz
-	TurnTimeoutSecs postgres.ColumnInteger
-	HintsAllowed    postgres.ColumnBool
-	HintsPerPlayer  postgres.ColumnInteger
-	MoveCount       postgres.ColumnInteger
-	EndReason       postgres.ColumnString
-	CreatedAt       postgres.ColumnTimestampz
-	UpdatedAt       postgres.ColumnTimestampz
-	FinishedAt      postgres.ColumnTimestampz
-	DropoutTiles    postgres.ColumnString
+	GameID               postgres.ColumnString
+	Variant              postgres.ColumnString
+	DictVersion          postgres.ColumnString
+	Seed                 postgres.ColumnInteger
+	Status               postgres.ColumnString
+	Players              postgres.ColumnInteger
+	ToMove               postgres.ColumnInteger
+	TurnStartedAt        postgres.ColumnTimestampz
+	TurnTimeoutSecs      postgres.ColumnInteger
+	HintsAllowed         postgres.ColumnBool
+	HintsPerPlayer       postgres.ColumnInteger
+	MoveCount            postgres.ColumnInteger
+	EndReason            postgres.ColumnString
+	CreatedAt            postgres.ColumnTimestampz
+	UpdatedAt            postgres.ColumnTimestampz
+	FinishedAt           postgres.ColumnTimestampz
+	DropoutTiles         postgres.ColumnString
+	MultipleWordsPerTurn postgres.ColumnBool
 
 	AllColumns     postgres.ColumnList
 	MutableColumns postgres.ColumnList
@@ -75,49 +76,51 @@ func newGamesTable(schemaName, tableName, alias string) *GamesTable {
 
 func newGamesTableImpl(schemaName, tableName, alias string) gamesTable {
 	var (
-		GameIDColumn          = postgres.StringColumn("game_id")
-		VariantColumn         = postgres.StringColumn("variant")
-		DictVersionColumn     = postgres.StringColumn("dict_version")
-		SeedColumn            = postgres.IntegerColumn("seed")
-		StatusColumn          = postgres.StringColumn("status")
-		PlayersColumn         = postgres.IntegerColumn("players")
-		ToMoveColumn          = postgres.IntegerColumn("to_move")
-		TurnStartedAtColumn   = postgres.TimestampzColumn("turn_started_at")
-		TurnTimeoutSecsColumn = postgres.IntegerColumn("turn_timeout_secs")
-		HintsAllowedColumn    = postgres.BoolColumn("hints_allowed")
-		HintsPerPlayerColumn  = postgres.IntegerColumn("hints_per_player")
-		MoveCountColumn       = postgres.IntegerColumn("move_count")
-		EndReasonColumn       = postgres.StringColumn("end_reason")
-		CreatedAtColumn       = postgres.TimestampzColumn("created_at")
-		UpdatedAtColumn       = postgres.TimestampzColumn("updated_at")
-		FinishedAtColumn      = postgres.TimestampzColumn("finished_at")
-		DropoutTilesColumn    = postgres.StringColumn("dropout_tiles")
-		allColumns            = postgres.ColumnList{GameIDColumn, VariantColumn, DictVersionColumn, SeedColumn, StatusColumn, PlayersColumn, ToMoveColumn, TurnStartedAtColumn, TurnTimeoutSecsColumn, HintsAllowedColumn, HintsPerPlayerColumn, MoveCountColumn, EndReasonColumn, CreatedAtColumn, UpdatedAtColumn, FinishedAtColumn, DropoutTilesColumn}
-		mutableColumns        = postgres.ColumnList{VariantColumn, DictVersionColumn, SeedColumn, StatusColumn, PlayersColumn, ToMoveColumn, TurnStartedAtColumn, TurnTimeoutSecsColumn, HintsAllowedColumn, HintsPerPlayerColumn, MoveCountColumn, EndReasonColumn, CreatedAtColumn, UpdatedAtColumn, FinishedAtColumn, DropoutTilesColumn}
-		defaultColumns        = postgres.ColumnList{StatusColumn, ToMoveColumn, TurnStartedAtColumn, HintsAllowedColumn, HintsPerPlayerColumn, MoveCountColumn, CreatedAtColumn, UpdatedAtColumn, DropoutTilesColumn}
+		GameIDColumn               = postgres.StringColumn("game_id")
+		VariantColumn              = postgres.StringColumn("variant")
+		DictVersionColumn          = postgres.StringColumn("dict_version")
+		SeedColumn                 = postgres.IntegerColumn("seed")
+		StatusColumn               = postgres.StringColumn("status")
+		PlayersColumn              = postgres.IntegerColumn("players")
+		ToMoveColumn               = postgres.IntegerColumn("to_move")
+		TurnStartedAtColumn        = postgres.TimestampzColumn("turn_started_at")
+		TurnTimeoutSecsColumn      = postgres.IntegerColumn("turn_timeout_secs")
+		HintsAllowedColumn         = postgres.BoolColumn("hints_allowed")
+		HintsPerPlayerColumn       = postgres.IntegerColumn("hints_per_player")
+		MoveCountColumn            = postgres.IntegerColumn("move_count")
+		EndReasonColumn            = postgres.StringColumn("end_reason")
+		CreatedAtColumn            = postgres.TimestampzColumn("created_at")
+		UpdatedAtColumn            = postgres.TimestampzColumn("updated_at")
+		FinishedAtColumn           = postgres.TimestampzColumn("finished_at")
+		DropoutTilesColumn         = postgres.StringColumn("dropout_tiles")
+		MultipleWordsPerTurnColumn = postgres.BoolColumn("multiple_words_per_turn")
+		allColumns                 = postgres.ColumnList{GameIDColumn, VariantColumn, DictVersionColumn, SeedColumn, StatusColumn, PlayersColumn, ToMoveColumn, TurnStartedAtColumn, TurnTimeoutSecsColumn, HintsAllowedColumn, HintsPerPlayerColumn, MoveCountColumn, EndReasonColumn, CreatedAtColumn, UpdatedAtColumn, FinishedAtColumn, DropoutTilesColumn, MultipleWordsPerTurnColumn}
+		mutableColumns             = postgres.ColumnList{VariantColumn, DictVersionColumn, SeedColumn, StatusColumn, PlayersColumn, ToMoveColumn, TurnStartedAtColumn, TurnTimeoutSecsColumn, HintsAllowedColumn, HintsPerPlayerColumn, MoveCountColumn, EndReasonColumn, CreatedAtColumn, UpdatedAtColumn, FinishedAtColumn, DropoutTilesColumn, MultipleWordsPerTurnColumn}
+		defaultColumns             = postgres.ColumnList{StatusColumn, ToMoveColumn, TurnStartedAtColumn, HintsAllowedColumn, HintsPerPlayerColumn, MoveCountColumn, CreatedAtColumn, UpdatedAtColumn, DropoutTilesColumn, MultipleWordsPerTurnColumn}
 	)
 
 	return gamesTable{
 		Table: postgres.NewTable(schemaName, tableName, alias, allColumns...),
 
 		//Columns
-		GameID:          GameIDColumn,
-		Variant:         VariantColumn,
-		DictVersion:     DictVersionColumn,
-		Seed:            SeedColumn,
-		Status:          StatusColumn,
-		Players:         PlayersColumn,
-		ToMove:          ToMoveColumn,
-		TurnStartedAt:   TurnStartedAtColumn,
-		TurnTimeoutSecs: TurnTimeoutSecsColumn,
-		HintsAllowed:    HintsAllowedColumn,
-		HintsPerPlayer:  HintsPerPlayerColumn,
-		MoveCount:       MoveCountColumn,
-		EndReason:       EndReasonColumn,
-		CreatedAt:       CreatedAtColumn,
-		UpdatedAt:       UpdatedAtColumn,
-		FinishedAt:      FinishedAtColumn,
-		DropoutTiles:    DropoutTilesColumn,
+		GameID:               GameIDColumn,
+		Variant:              VariantColumn,
+		DictVersion:          DictVersionColumn,
+		Seed:                 SeedColumn,
+		Status:               StatusColumn,
+		Players:              PlayersColumn,
+		ToMove:               ToMoveColumn,
+		TurnStartedAt:        TurnStartedAtColumn,
+		TurnTimeoutSecs:      TurnTimeoutSecsColumn,
+		HintsAllowed:         HintsAllowedColumn,
+		HintsPerPlayer:       HintsPerPlayerColumn,
+		MoveCount:            MoveCountColumn,
+		EndReason:            EndReasonColumn,
+		CreatedAt:            CreatedAtColumn,
+		UpdatedAt:            UpdatedAtColumn,
+		FinishedAt:           FinishedAtColumn,
+		DropoutTiles:         DropoutTilesColumn,
+		MultipleWordsPerTurn: MultipleWordsPerTurnColumn,
 
 		AllColumns:     allColumns,
 		MutableColumns: mutableColumns,

backend/internal/postgres/migrations/00001_baseline.sql

@@ -97,6 +97,7 @@ CREATE TABLE games (
     updated_at        timestamptz NOT NULL DEFAULT now(),
     finished_at       timestamptz,
     dropout_tiles     text        NOT NULL DEFAULT 'remove',
+    multiple_words_per_turn boolean NOT NULL DEFAULT true,
     CONSTRAINT games_variant_chk CHECK (variant IN ('scrabble_en', 'scrabble_ru', 'erudit_ru')),
     CONSTRAINT games_status_chk CHECK (status IN ('active', 'finished')),
     CONSTRAINT games_players_chk CHECK (players BETWEEN 2 AND 4),
@@ -260,6 +261,7 @@ CREATE TABLE game_invitations (
     hints_allowed     boolean     NOT NULL DEFAULT true,
     hints_per_player  smallint    NOT NULL DEFAULT 1,
     dropout_tiles     text        NOT NULL DEFAULT 'remove',
+    multiple_words_per_turn boolean NOT NULL DEFAULT true,
     status            text        NOT NULL DEFAULT 'pending',
     game_id           uuid        REFERENCES games (game_id) ON DELETE SET NULL,
     expires_at        timestamptz NOT NULL,

backend/internal/server/handlers_invitations.go

@@ -27,17 +27,18 @@ type invitationInviteeDTO struct {
 
 // invitationDTO is a friend-game invitation with its settings and invitees.
 type invitationDTO struct {
-	ID              string                 `json:"id"`
-	Inviter         accountRefDTO          `json:"inviter"`
-	Invitees        []invitationInviteeDTO `json:"invitees"`
-	Variant         string                 `json:"variant"`
-	TurnTimeoutSecs int                    `json:"turn_timeout_secs"`
-	HintsAllowed    bool                   `json:"hints_allowed"`
-	HintsPerPlayer  int                    `json:"hints_per_player"`
-	DropoutTiles    string                 `json:"dropout_tiles"`
-	Status          string                 `json:"status"`
-	GameID          string                 `json:"game_id,omitempty"`
-	ExpiresAtUnix   int64                  `json:"expires_at_unix"`
+	ID                   string                 `json:"id"`
+	Inviter              accountRefDTO          `json:"inviter"`
+	Invitees             []invitationInviteeDTO `json:"invitees"`
+	Variant              string                 `json:"variant"`
+	TurnTimeoutSecs      int                    `json:"turn_timeout_secs"`
+	HintsAllowed         bool                   `json:"hints_allowed"`
+	HintsPerPlayer       int                    `json:"hints_per_player"`
+	DropoutTiles         string                 `json:"dropout_tiles"`
+	MultipleWordsPerTurn bool                   `json:"multiple_words_per_turn"`
+	Status               string                 `json:"status"`
+	GameID               string                 `json:"game_id,omitempty"`
+	ExpiresAtUnix        int64                  `json:"expires_at_unix"`
 }
 
 // invitationListDTO is the caller's open invitations.
@@ -47,27 +48,29 @@ type invitationListDTO struct {
 
 // createInvitationRequest proposes a friend game to the named invitees.
 type createInvitationRequest struct {
-	InviteeIDs      []string `json:"invitee_ids"`
-	Variant         string   `json:"variant"`
-	TurnTimeoutSecs int      `json:"turn_timeout_secs"`
-	HintsAllowed    bool     `json:"hints_allowed"`
-	HintsPerPlayer  int      `json:"hints_per_player"`
-	DropoutTiles    string   `json:"dropout_tiles"`
+	InviteeIDs           []string `json:"invitee_ids"`
+	Variant              string   `json:"variant"`
+	TurnTimeoutSecs      int      `json:"turn_timeout_secs"`
+	HintsAllowed         bool     `json:"hints_allowed"`
+	HintsPerPlayer       int      `json:"hints_per_player"`
+	DropoutTiles         string   `json:"dropout_tiles"`
+	MultipleWordsPerTurn bool     `json:"multiple_words_per_turn"`
 }
 
 // invitationDTOFrom projects a lobby invitation, resolving names through memo.
 func (s *Server) invitationDTOFrom(ctx context.Context, inv lobby.Invitation, memo map[string]string) invitationDTO {
 	dto := invitationDTO{
-		ID:              inv.ID.String(),
-		Inviter:         s.namedRef(ctx, inv.InviterID, memo),
-		Invitees:        make([]invitationInviteeDTO, 0, len(inv.Invitees)),
-		Variant:         inv.Settings.Variant.String(),
-		TurnTimeoutSecs: int(inv.Settings.TurnTimeout.Seconds()),
-		HintsAllowed:    inv.Settings.HintsAllowed,
-		HintsPerPlayer:  inv.Settings.HintsPerPlayer,
-		DropoutTiles:    inv.Settings.DropoutTiles.String(),
-		Status:          inv.Status,
-		ExpiresAtUnix:   inv.ExpiresAt.Unix(),
+		ID:                   inv.ID.String(),
+		Inviter:              s.namedRef(ctx, inv.InviterID, memo),
+		Invitees:             make([]invitationInviteeDTO, 0, len(inv.Invitees)),
+		Variant:              inv.Settings.Variant.String(),
+		TurnTimeoutSecs:      int(inv.Settings.TurnTimeout.Seconds()),
+		HintsAllowed:         inv.Settings.HintsAllowed,
+		HintsPerPlayer:       inv.Settings.HintsPerPlayer,
+		DropoutTiles:         inv.Settings.DropoutTiles.String(),
+		MultipleWordsPerTurn: inv.Settings.MultipleWordsPerTurn,
+		Status:               inv.Status,
+		ExpiresAtUnix:        inv.ExpiresAt.Unix(),
 	}
 	if inv.GameID != nil {
 		dto.GameID = inv.GameID.String()
@@ -102,9 +105,10 @@ func (s *Server) handleCreateInvitation(c *gin.Context) {
 		return
 	}
 	settings := lobby.InvitationSettings{
-		Variant:        variant,
-		HintsAllowed:   req.HintsAllowed,
-		HintsPerPlayer: req.HintsPerPlayer,
+		Variant:              variant,
+		HintsAllowed:         req.HintsAllowed,
+		HintsPerPlayer:       req.HintsPerPlayer,
+		MultipleWordsPerTurn: req.MultipleWordsPerTurn,
 	}
 	if req.TurnTimeoutSecs > 0 {
 		settings.TurnTimeout = time.Duration(req.TurnTimeoutSecs) * time.Second

backend/internal/server/handlers_user.go

@@ -133,9 +133,10 @@ func (s *Server) handleGameState(c *gin.Context) {
 	c.JSON(http.StatusOK, dto)
 }
 
-// enqueueRequest joins the per-variant auto-match pool.
+// enqueueRequest joins the per-variant auto-match pool under a per-turn word rule.
 type enqueueRequest struct {
-	Variant string `json:"variant"`
+	Variant              string `json:"variant"`
+	MultipleWordsPerTurn bool   `json:"multiple_words_per_turn"`
 }
 
 // handleEnqueue joins the auto-match pool for a variant.
@@ -155,7 +156,7 @@ func (s *Server) handleEnqueue(c *gin.Context) {
 		abortBadRequest(c, "unknown variant")
 		return
 	}
-	res, err := s.matchmaker.Enqueue(c.Request.Context(), uid, variant)
+	res, err := s.matchmaker.Enqueue(c.Request.Context(), uid, variant, req.MultipleWordsPerTurn)
 	if err != nil {
 		s.abortErr(c, err)
 		return