feat(telegram,game): single bot + per-user variant preferences

Collapse the two per-language Telegram bots into one unified bot and
replace language-based variant gating with explicit per-user variant
preferences.

- Telegram: one bot; drop service_language and the supported_languages
  set everywhere (DB, account, auth, FlatBuffers Session wire, gateway,
  connector proto). The single bot renders chat and out-of-app push in
  the recipient's preferred_language; remove the game-language push
  routing override (notify Intent.Language / push Event.language).
- Preferences: new accounts.variant_preferences (text[], DB default
  {erudit_ru}, CHECK non-empty + subset of the three variants). Gates
  the New Game picker, vs-AI and the friend invitation the player
  creates, enforced server-side (HTTP 400 otherwise); an invited friend
  may still accept any variant. Edited on the Settings screen; variants
  are Erudit-first everywhere.
- Admin: drop the per-bot language selectors (broadcast / send-to-user)
  and the feedback channel_lang column/field.
- Env/CI: collapse TELEGRAM_BOT_TOKEN_{EN,RU}, TELEGRAM_GAME_CHANNEL_ID_{EN,RU},
  VITE_TELEGRAM_LINK{,_EN,_RU} and VITE_TELEGRAM_GAME_CHANNEL_NAME_{EN,RU}
  to single unsuffixed names; drop GATEWAY_DEFAULT_SUPPORTED_LANGUAGES.
- Docs updated (ARCHITECTURE, FUNCTIONAL + _ru, platform/telegram, gateway,
  backend, ui, UI_DESIGN, PRERELEASE).

The migration squash is deferred to a follow-up PR.

backend/internal/account/account.go

@@ -55,12 +55,12 @@ type Account struct {
 	HintBalance         int
 	BlockChat           bool
 	BlockFriendRequests bool
-	// ServiceLanguage is the language tag (en/ru) of the bot the account last
-	// authenticated through (its last Telegram ValidateInitData); it routes the
-	// account's out-of-app push back through the right bot. Empty when the account
-	// has never signed in through a tagged bot. Distinct from PreferredLanguage (the
-	// interface language) and from a game's variant language.
-	ServiceLanguage string
+	// VariantPreferences is the set of game variants (engine.Variant stable labels:
+	// "scrabble_en", "scrabble_ru", "erudit_ru") the player is willing to be matched
+	// into. It gates the New Game picker, the matchmaker and the friend-invite the
+	// player creates; an invited friend may still accept any variant. A new account
+	// defaults to Erudit only. Never empty — enforced on update and by a DB check.
+	VariantPreferences []string
 	// IsGuest marks an ephemeral guest account: a durable row with no identity,
 	// excluded from statistics, friends and history.
 	IsGuest bool
@@ -491,36 +491,12 @@ func (s *Store) ClearHighRateFlag(ctx context.Context, id uuid.UUID) error {
 	return nil
 }
 
-// SetServiceLanguage records the service language (en/ru) of the bot a Telegram
-// user authenticated through. It is called on every Telegram login — new and
-// existing accounts — so it tracks the bot the user last came through (last-login-
-// wins), and the out-of-app push routes by it. It is a no-op for an empty language
-// (a non-Telegram login carries none) and does not bump updated_at (an infra
-// routing field, not a user profile edit).
-func (s *Store) SetServiceLanguage(ctx context.Context, id uuid.UUID, language string) error {
-	if language == "" {
-		return nil
-	}
-	stmt := table.Accounts.
-		UPDATE(table.Accounts.ServiceLanguage).
-		SET(postgres.String(language)).
-		WHERE(table.Accounts.AccountID.EQ(postgres.UUID(id)))
-	if _, err := stmt.ExecContext(ctx, s.db); err != nil {
-		return fmt.Errorf("account: set service language %s: %w", id, err)
-	}
-	return nil
-}
-
 // modelToAccount projects a generated model row into the public Account struct.
 func modelToAccount(row model.Accounts) Account {
 	var mergedInto uuid.UUID
 	if row.MergedInto != nil {
 		mergedInto = *row.MergedInto
 	}
-	var serviceLanguage string
-	if row.ServiceLanguage != nil {
-		serviceLanguage = *row.ServiceLanguage
-	}
 	var flaggedHighRateAt time.Time
 	if row.FlaggedHighRateAt != nil {
 		flaggedHighRateAt = *row.FlaggedHighRateAt
@@ -529,7 +505,7 @@ func modelToAccount(row model.Accounts) Account {
 		ID:                     row.AccountID,
 		DisplayName:            row.DisplayName,
 		PreferredLanguage:      row.PreferredLanguage,
-		ServiceLanguage:        serviceLanguage,
+		VariantPreferences:     []string(row.VariantPreferences),
 		TimeZone:               row.TimeZone,
 		AwayStart:              row.AwayStart,
 		AwayEnd:                row.AwayEnd,

backend/internal/account/profile.go

@@ -14,6 +14,7 @@ import (
 	"github.com/go-jet/jet/v2/postgres"
 	"github.com/go-jet/jet/v2/qrm"
 	"github.com/google/uuid"
+	"github.com/lib/pq"
 
 	"scrabble/backend/internal/postgres/jet/backend/model"
 	"scrabble/backend/internal/postgres/jet/backend/table"
@@ -58,6 +59,46 @@ type ProfileUpdate struct {
 	BlockChat              bool
 	BlockFriendRequests    bool
 	NotificationsInAppOnly bool
+	// VariantPreferences is the set of game variants the player allows themselves to
+	// be matched into (engine.Variant stable labels). UpdateProfile cleans it to a
+	// deduplicated, canonically ordered subset of the known variants and rejects an
+	// empty set.
+	VariantPreferences []string
+}
+
+// knownVariants is the closed set of game-variant labels (engine.Variant stable
+// labels) a profile's variant preferences may contain. It lives here so the store
+// does not depend on the engine package; the server handler additionally validates
+// against engine.ParseVariant, and a DB check enforces the same subset.
+var knownVariants = map[string]bool{"erudit_ru": true, "scrabble_ru": true, "scrabble_en": true}
+
+// canonicalVariantOrder is the deterministic order variant preferences are stored
+// in (Erudit, Russian Scrabble, English), independent of the client's order.
+var canonicalVariantOrder = []string{"erudit_ru", "scrabble_ru", "scrabble_en"}
+
+// validateVariantPreferences cleans a profile's variant-preference set: it drops
+// duplicates, rejects an unknown label or an empty set (ErrInvalidProfile) and
+// returns the preferences in canonicalVariantOrder so the stored value is
+// deterministic regardless of the order the client sent.
+func validateVariantPreferences(prefs []string) ([]string, error) {
+	seen := make(map[string]bool, len(prefs))
+	for _, p := range prefs {
+		p = strings.TrimSpace(p)
+		if !knownVariants[p] {
+			return nil, fmt.Errorf("%w: variant preference %q", ErrInvalidProfile, p)
+		}
+		seen[p] = true
+	}
+	if len(seen) == 0 {
+		return nil, fmt.Errorf("%w: variant preferences must not be empty", ErrInvalidProfile)
+	}
+	out := make([]string, 0, len(seen))
+	for _, v := range canonicalVariantOrder {
+		if seen[v] {
+			out = append(out, v)
+		}
+	}
+	return out, nil
 }
 
 // UpdateProfile validates and overwrites the editable fields of the account, then
@@ -79,17 +120,26 @@ func (s *Store) UpdateProfile(ctx context.Context, id uuid.UUID, p ProfileUpdate
 	if err := validateAwayWindow(p.AwayStart, p.AwayEnd); err != nil {
 		return Account{}, err
 	}
+	prefs, err := validateVariantPreferences(p.VariantPreferences)
+	if err != nil {
+		return Account{}, err
+	}
 
 	stmt := table.Accounts.UPDATE(
 		table.Accounts.DisplayName, table.Accounts.PreferredLanguage, table.Accounts.TimeZone,
 		table.Accounts.AwayStart, table.Accounts.AwayEnd,
 		table.Accounts.BlockChat, table.Accounts.BlockFriendRequests,
-		table.Accounts.NotificationsInAppOnly, table.Accounts.UpdatedAt,
+		table.Accounts.NotificationsInAppOnly, table.Accounts.VariantPreferences,
+		table.Accounts.UpdatedAt,
 	).SET(
 		postgres.String(name), postgres.String(lang), postgres.String(tz),
 		postgres.TimeT(p.AwayStart), postgres.TimeT(p.AwayEnd),
 		postgres.Bool(p.BlockChat), postgres.Bool(p.BlockFriendRequests),
-		postgres.Bool(p.NotificationsInAppOnly), postgres.TimestampzT(time.Now().UTC()),
+		postgres.Bool(p.NotificationsInAppOnly),
+		// prefs are validated against the closed knownVariants set; bind as a text[]
+		// parameter (lib/pq encodes the array, the cast pins the column type).
+		postgres.Raw("#variant_prefs::text[]", map[string]interface{}{"#variant_prefs": pq.StringArray(prefs)}),
+		postgres.TimestampzT(time.Now().UTC()),
 	).WHERE(table.Accounts.AccountID.EQ(postgres.UUID(id))).
 		RETURNING(table.Accounts.AllColumns)
 

backend/internal/account/profile_test.go

@@ -3,6 +3,7 @@ package account
 import (
 	"context"
 	"errors"
+	"slices"
 	"strings"
 	"testing"
 	"time"
@@ -16,7 +17,7 @@ import (
 // offset/IANA timezone), not just their unit tests in validate_test.go.
 func TestUpdateProfileValidation(t *testing.T) {
 	s := &Store{}
-	base := ProfileUpdate{DisplayName: "Kaya", PreferredLanguage: "en", TimeZone: "UTC"}
+	base := ProfileUpdate{DisplayName: "Kaya", PreferredLanguage: "en", TimeZone: "UTC", VariantPreferences: []string{"erudit_ru"}}
 	hm := func(h, m int) time.Time { return time.Date(0, 1, 1, h, m, 0, 0, time.UTC) }
 	tests := []struct {
 		name string
@@ -28,6 +29,8 @@ func TestUpdateProfileValidation(t *testing.T) {
 		{"over-long name", func(p *ProfileUpdate) { p.DisplayName = strings.Repeat("x", maxDisplayName+1) }},
 		{"bad name layout", func(p *ProfileUpdate) { p.DisplayName = "Bad__Name" }},
 		{"away over 12h", func(p *ProfileUpdate) { p.AwayStart, p.AwayEnd = hm(8, 0), hm(21, 0) }},
+		{"empty variant preferences", func(p *ProfileUpdate) { p.VariantPreferences = nil }},
+		{"unknown variant preference", func(p *ProfileUpdate) { p.VariantPreferences = []string{"chess"} }},
 	}
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {
@@ -39,3 +42,22 @@ func TestUpdateProfileValidation(t *testing.T) {
 		})
 	}
 }
+
+// TestValidateVariantPreferences checks the cleaning of a profile's variant set:
+// duplicates collapse, the result is canonically ordered (Erudit, Russian Scrabble,
+// English) regardless of input order, and an empty or unknown set is rejected.
+func TestValidateVariantPreferences(t *testing.T) {
+	got, err := validateVariantPreferences([]string{"scrabble_en", "erudit_ru", "scrabble_en"})
+	if err != nil {
+		t.Fatalf("validate: %v", err)
+	}
+	if want := []string{"erudit_ru", "scrabble_en"}; !slices.Equal(got, want) {
+		t.Fatalf("got %v, want %v", got, want)
+	}
+	if _, err := validateVariantPreferences(nil); !errors.Is(err, ErrInvalidProfile) {
+		t.Fatalf("empty err = %v, want ErrInvalidProfile", err)
+	}
+	if _, err := validateVariantPreferences([]string{"chess"}); !errors.Is(err, ErrInvalidProfile) {
+		t.Fatalf("unknown err = %v, want ErrInvalidProfile", err)
+	}
+}

backend/internal/adminconsole/render_test.go

@@ -43,7 +43,7 @@ func TestRendererRendersEveryPage(t *testing.T) {
 		{"messages", MessagesView{Items: []MessageRow{{ID: "m1", SenderID: "a1", SenderName: "Kaya", Source: "telegram", Body: "good luck", GameID: "g1", Unread: true}}, UnreadOnly: true, Pager: NewPager(1, 50, 1)}, "unread only"},
 		{"chatmessage", ChatMessageDetailView{ID: "m1", GameID: "g1", SenderID: "a1", SenderName: "Kaya", Source: "telegram", Kind: "message", Body: "good luck", Unread: true, Seats: []ChatSeatStatusRow{{Seat: 0, AccountID: "a1", DisplayName: "Kaya", Role: "sender"}, {Seat: 1, AccountID: "b2", DisplayName: "Opp", Role: "unread"}}}, "Read by seat"},
 		{"feedback", FeedbackView{Items: []FeedbackRow{{ID: "f1", AccountID: "a1", SenderName: "Kaya", Source: "telegram", Channel: "web", HasAttachment: true, Replied: true}}, Status: "unread", Pager: NewPager(1, 50, 1)}, "replied"},
-		{"feedback_detail", FeedbackDetailView{ID: "f1", AccountID: "a1", SenderName: "Kaya", Channel: "telegram", InterfaceLanguage: "en", BotLanguage: "ru", Body: "please fix the board", HasAttachment: true, AttachmentName: "shot.png", IsImage: true, Banned: true}, "bot: ru"},
+		{"feedback_detail", FeedbackDetailView{ID: "f1", AccountID: "a1", SenderName: "Kaya", Channel: "telegram", InterfaceLanguage: "en", Body: "please fix the board", HasAttachment: true, AttachmentName: "shot.png", IsImage: true, Banned: true}, "Interface language"},
 		{"complaint_detail", ComplaintDetailView{ID: "c1", Word: "qi", Variant: "scrabble_en"}, "Resolve"},
 		{"dictionary", DictionaryView{ActiveVersion: "v1.0.0", Variants: []VariantVersions{{Variant: "scrabble_en", Versions: []string{"v1.0.0"}}}, Changes: []DictChangeRow{{Variant: "scrabble_en", Word: "qi", Action: "add"}}}, "Update dictionaries"},
 		{"dictionary_preview", DictionaryPreviewView{Version: "v1.1.0", Token: "0123456789abcdef0123456789abcdef", ActiveVersion: "v1.0.0", Variants: []VariantDiffRow{{Variant: "scrabble_en", AddedCount: 2, RemovedCount: 1, AddedSample: []string{"qi", "za"}, RemovedSample: []string{"xqz"}, RemovedTruncated: true}}}, "v1.1.0"},

backend/internal/adminconsole/templates/pages/broadcast.gohtml

@@ -5,7 +5,6 @@
 {{if .ConnectorEnabled}}
 <form class="form col" method="post" action="/_gm/broadcast">
 <label>Message <textarea name="text" required></textarea></label>
-<label>Bot language <select name="language"><option value="en">en</option><option value="ru">ru</option></select></label>
 <div><button type="submit">Post to channel</button></div>
 </form>
 {{else}}<p class="note">connector not configured (set BACKEND_CONNECTOR_ADDR)</p>{{end}}

backend/internal/adminconsole/templates/pages/feedback_detail.gohtml

@@ -5,7 +5,7 @@
 <section class="panel"><h2>Message</h2>
 <ul class="kv">
 <li><b>From</b> <a href="/_gm/users/{{.AccountID}}">{{.SenderName}}</a> ({{.Source}})</li>
-<li><b>Channel</b> {{.Channel}}{{if .BotLanguage}} (bot: {{.BotLanguage}}){{end}}</li>
+<li><b>Channel</b> {{.Channel}}</li>
 <li><b>Interface language</b> {{.InterfaceLanguage}}</li>
 <li><b>IP</b> {{if .IP}}<code>{{.IP}}</code>{{else}}<span class="note">none</span>{{end}}</li>
 <li><b>Filed</b> {{.CreatedAt}}</li>

backend/internal/adminconsole/templates/pages/user_detail.gohtml

@@ -137,7 +137,6 @@
 {{if .ConnectorEnabled}}
 <form class="form col" method="post" action="/_gm/users/{{.ID}}/message">
 <label>Message <textarea name="text" required></textarea></label>
-<label>Bot language <select name="language"><option value="en">en</option><option value="ru">ru</option></select></label>
 <div><button type="submit">Send to user</button></div>
 </form>
 {{else}}<p class="note">connector not configured (set BACKEND_CONNECTOR_ADDR)</p>{{end}}

backend/internal/adminconsole/views.go

@@ -531,11 +531,8 @@ type FeedbackDetailView struct {
 	SenderName string
 	Source     string
 	Channel    string
-	// InterfaceLanguage is the sender's interface language (account preference);
-	// BotLanguage is the connector bot they last used (en/ru), set only for a
-	// message that arrived through an external connector (Telegram).
+	// InterfaceLanguage is the sender's interface language (account preference).
 	InterfaceLanguage string
-	BotLanguage       string
 	IP                string
 	Body              string
 	HasAttachment     bool

backend/internal/connector/client.go

@@ -1,11 +1,10 @@
 // Package connector is the backend's gRPC client for the Telegram platform
 // connector side-service. The admin console uses it to send operator broadcasts:
-// a direct message to one user, or a post to a game channel. Each broadcast
-// selects the delivering bot by language (an operator choice, since the connector
-// hosts one bot per service language). The connector lives on the trusted internal
-// network, so the connection uses insecure (plaintext) transport credentials
-// (docs/ARCHITECTURE.md §12). It mirrors gateway/internal/connector, narrowed to
-// the two broadcast methods the admin surface needs.
+// a direct message to one user, or a post to the game channel, through the single
+// bot. The connector lives on the trusted internal network, so the connection uses
+// insecure (plaintext) transport credentials (docs/ARCHITECTURE.md §12). It mirrors
+// gateway/internal/connector, narrowed to the two broadcast methods the admin
+// surface needs.
 package connector
 
 import (
@@ -37,22 +36,21 @@ func New(addr string) (*Client, error) {
 func (c *Client) Close() error { return c.conn.Close() }
 
 // SendToUser sends an operator text message to one user, addressed by their
-// platform external_id, through the bot for the given language. delivered reports
-// whether the connector actually sent it (false when the user has not started that
-// bot).
-func (c *Client) SendToUser(ctx context.Context, externalID, text, language string) (bool, error) {
-	resp, err := c.c.SendToUser(ctx, &telegramv1.SendToUserRequest{ExternalId: externalID, Text: text, Language: language})
+// platform external_id, through the bot. delivered reports whether the connector
+// actually sent it (false when the user has not started the bot).
+func (c *Client) SendToUser(ctx context.Context, externalID, text string) (bool, error) {
+	resp, err := c.c.SendToUser(ctx, &telegramv1.SendToUserRequest{ExternalId: externalID, Text: text})
 	if err != nil {
 		return false, err
 	}
 	return resp.GetDelivered(), nil
 }
 
-// SendToGameChannel posts an operator text message to the game channel of the bot
-// for the given language. delivered reports whether the connector sent it (false
-// when that bot has no channel configured).
-func (c *Client) SendToGameChannel(ctx context.Context, text, language string) (bool, error) {
-	resp, err := c.c.SendToGameChannel(ctx, &telegramv1.SendToGameChannelRequest{Text: text, Language: language})
+// SendToGameChannel posts an operator text message to the bot's game channel.
+// delivered reports whether the connector sent it (false when the bot has no
+// channel configured).
+func (c *Client) SendToGameChannel(ctx context.Context, text string) (bool, error) {
+	resp, err := c.c.SendToGameChannel(ctx, &telegramv1.SendToGameChannelRequest{Text: text})
 	if err != nil {
 		return false, err
 	}

backend/internal/feedback/service.go

@@ -112,14 +112,9 @@ func (svc *Service) Submit(ctx context.Context, accountID uuid.UUID, body string
 		attachmentName = "" // a name without bytes carries no attachment
 	}
 	ch := normalizeChannel(channel)
-	// Snapshot the languages at submit time (acc is already loaded for the guest check):
-	// the sender's interface language, and the connector bot language when the message
-	// came through an external connector (currently Telegram).
-	var channelLang string
-	if ch == "telegram" {
-		channelLang = acc.ServiceLanguage
-	}
-	_, err = svc.store.Insert(ctx, accountID, body, attachment, attachmentName, ch, acc.PreferredLanguage, channelLang, parseIP(senderIP))
+	// Snapshot the sender's interface language at submit time (acc is already loaded
+	// for the guest check) so the operator later sees the state as it was.
+	_, err = svc.store.Insert(ctx, accountID, body, attachment, attachmentName, ch, acc.PreferredLanguage, parseIP(senderIP))
 	return err
 }
 

backend/internal/feedback/store.go

@@ -34,11 +34,10 @@ func NewStore(db *sql.DB) *Store {
 
 // Insert stores one feedback message from accountID and returns its id. attachment
 // is the raw file bytes (nil for none); attachmentName, ip and a non-default
-// channel are stored as given. lang (the sender's interface language) and channelLang
-// (the connector bot language, empty for a non-connector channel) are snapshots taken
-// now, so the operator later sees the state at submit time. created_at defaults to
-// now() in the database.
-func (s *Store) Insert(ctx context.Context, accountID uuid.UUID, body string, attachment []byte, attachmentName, channel, lang, channelLang string, ip *string) (uuid.UUID, error) {
+// channel are stored as given. lang (the sender's interface language) is a snapshot
+// taken now, so the operator later sees the state at submit time. created_at defaults
+// to now() in the database.
+func (s *Store) Insert(ctx context.Context, accountID uuid.UUID, body string, attachment []byte, attachmentName, channel, lang string, ip *string) (uuid.UUID, error) {
 	id, err := uuid.NewV7()
 	if err != nil {
 		return uuid.Nil, fmt.Errorf("feedback: new message id: %w", err)
@@ -49,9 +48,9 @@ func (s *Store) Insert(ctx context.Context, accountID uuid.UUID, body string, at
 	}
 	if _, err := s.db.ExecContext(ctx,
 		`INSERT INTO backend.feedback_messages
-		   (message_id, account_id, body, attachment, attachment_name, channel, lang, channel_lang, sender_ip)
-		 VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9)`,
-		id, accountID, body, att, nullStr(attachmentName), channel, nullStr(lang), nullStr(channelLang), ip); err != nil {
+		   (message_id, account_id, body, attachment, attachment_name, channel, lang, sender_ip)
+		 VALUES ($1, $2, $3, $4, $5, $6, $7, $8)`,
+		id, accountID, body, att, nullStr(attachmentName), channel, nullStr(lang), ip); err != nil {
 		return uuid.Nil, fmt.Errorf("feedback: insert: %w", err)
 	}
 	return id, nil
@@ -228,10 +227,8 @@ type AdminMessage struct {
 	Source     string
 	Body       string
 	Channel    string
-	// Lang is the sender's interface language and ChannelLang the connector bot language
-	// (en/ru, empty for a non-connector channel) — both snapshotted at submit time.
+	// Lang is the sender's interface language, snapshotted at submit time.
 	Lang           string
-	ChannelLang    string
 	SenderIP       string
 	HasAttachment  bool
 	AttachmentName string
@@ -346,7 +343,7 @@ func (s *Store) AdminGet(ctx context.Context, id uuid.UUID) (AdminMessage, error
 	var m AdminMessage
 	var repliedAt sql.NullTime
 	q := `SELECT m.message_id, m.account_id, a.display_name, ` + feedbackSource + ` AS source, m.body, m.channel,
-		COALESCE(m.lang, ''), COALESCE(m.channel_lang, ''),
+		COALESCE(m.lang, ''),
 		COALESCE(m.sender_ip, ''), (m.attachment IS NOT NULL), COALESCE(m.attachment_name, ''),
 		(m.read_at IS NOT NULL), (m.archived_at IS NOT NULL), (m.reply_body IS NOT NULL),
 		COALESCE(m.reply_body, ''), m.replied_at, m.created_at
@@ -355,7 +352,7 @@ func (s *Store) AdminGet(ctx context.Context, id uuid.UUID) (AdminMessage, error
 	WHERE m.message_id = $1`
 	err := s.db.QueryRowContext(ctx, q, id).Scan(
 		&m.ID, &m.AccountID, &m.SenderName, &m.Source, &m.Body, &m.Channel,
-		&m.Lang, &m.ChannelLang,
+		&m.Lang,
 		&m.SenderIP, &m.HasAttachment, &m.AttachmentName,
 		&m.Read, &m.Archived, &m.Replied, &m.ReplyBody, &repliedAt, &m.CreatedAt)
 	if errors.Is(err, sql.ErrNoRows) {

backend/internal/game/emit_test.go

@@ -68,10 +68,6 @@ func TestEmitMoveNotifiesActor(t *testing.T) {
 	if got := string(yt.ScoreLine()); got != "13:19" { // seat 1 (recipient) first, then seat 0
 		t.Errorf("your_turn score_line = %q, want 13:19", got)
 	}
-	// Routed out-of-app by the game's language (the default Variant is English).
-	if yourTurn.Language != "en" {
-		t.Errorf("your_turn language = %q, want en", yourTurn.Language)
-	}
 }
 
 // TestEmitMoveAnnouncesGameOver checks the closing move sends a game_over push to every seat,
@@ -106,7 +102,4 @@ func TestEmitMoveAnnouncesGameOver(t *testing.T) {
 	if string(l.Result()) != "lost" || string(l.ScoreLine()) != "95:120" {
 		t.Errorf("loser game_over = %q / %q, want lost / 95:120", l.Result(), l.ScoreLine())
 	}
-	if over[winner].Language != "en" || over[loser].Language != "en" {
-		t.Errorf("game_over languages = %q/%q, want en/en", over[winner].Language, over[loser].Language)
-	}
 }

backend/internal/game/service.go

@@ -554,16 +554,6 @@ func (svc *Service) GameVariant(ctx context.Context, gameID uuid.UUID) (engine.V
 	return svc.store.GetGameVariant(ctx, gameID)
 }
 
-// GameLanguage returns the game's language tag ("en"/"ru"), derived from its variant, so a
-// game push routes out-of-app to the game's own bot rather than the recipient's last-login bot.
-func (svc *Service) GameLanguage(ctx context.Context, gameID uuid.UUID) (string, error) {
-	v, err := svc.GameVariant(ctx, gameID)
-	if err != nil {
-		return "", err
-	}
-	return v.Language(), nil
-}
-
 // RobotSchedule returns a game's bag seed and turn-start time, for the admin console's
 // robot-schedule panel (the deterministic play-to-win intent and next-move ETA).
 func (svc *Service) RobotSchedule(ctx context.Context, gameID uuid.UUID) (seed int64, turnStartedAt time.Time, err error) {
@@ -740,9 +730,6 @@ func (svc *Service) emitMove(ctx context.Context, post Game, rec engine.MoveReco
 		}
 		intents = append(intents, notify.OpponentMoved(s.AccountID, post.ID, rec, summary, bagLen))
 	}
-	// Game pushes are routed out-of-app by the game's own language, not the recipient's
-	// last-login bot.
-	lang := post.Variant.Language()
 	switch post.Status {
 	case StatusActive:
 		// Honest-AI games suppress your_turn: the robot replies instantly, so a "your turn"
@@ -757,7 +744,6 @@ func (svc *Service) emitMove(ctx context.Context, post Game, rec engine.MoveReco
 			}
 			opponent := svc.displayName(ctx, post.Seats, rec.Player)
 			yourTurn := notify.YourTurn(next, post.ID, deadline, opponent, action, word, scoreLine(post, post.ToMove), post.MoveCount)
-			yourTurn.Language = lang
 			intents = append(intents, yourTurn)
 		}
 	case StatusFinished:
@@ -769,7 +755,6 @@ func (svc *Service) emitMove(ctx context.Context, post Game, rec engine.MoveReco
 				continue
 			}
 			over := notify.GameOver(s.AccountID, post.ID, seatResult(post.Seats, s.Seat), scoreLine(post, s.Seat), summary)
-			over.Language = lang
 			intents = append(intents, over)
 		}
 	}

backend/internal/inttest/account_test.go

@@ -159,46 +159,6 @@ func TestProvisionTelegramUnknownLanguageDefaults(t *testing.T) {
 	}
 }
 
-// TestServiceLanguageRoundTrip checks SetServiceLanguage persists the push-routing
-// language (the bot a Telegram user last signed in through): a fresh account has
-// none, a set value reads back, a later login overwrites it (last-login-wins), and
-// an empty value is a no-op. The push-target route coalesces it with the preferred
-// language.
-func TestServiceLanguageRoundTrip(t *testing.T) {
-	ctx := context.Background()
-	store := account.NewStore(testDB)
-	acc, err := store.ProvisionTelegram(ctx, "tg-"+uuid.NewString(), "en", "", "Player")
-	if err != nil {
-		t.Fatalf("provision telegram: %v", err)
-	}
-	if acc.ServiceLanguage != "" {
-		t.Errorf("fresh ServiceLanguage = %q, want empty", acc.ServiceLanguage)
-	}
-
-	if err := store.SetServiceLanguage(ctx, acc.ID, "ru"); err != nil {
-		t.Fatalf("set service language: %v", err)
-	}
-	if got, err := store.GetByID(ctx, acc.ID); err != nil {
-		t.Fatalf("get by id: %v", err)
-	} else if got.ServiceLanguage != "ru" {
-		t.Errorf("ServiceLanguage = %q, want ru", got.ServiceLanguage)
-	}
-
-	// A later login through the other bot updates it; a subsequent empty value
-	// (a non-Telegram login) leaves it unchanged.
-	if err := store.SetServiceLanguage(ctx, acc.ID, "en"); err != nil {
-		t.Fatalf("update service language: %v", err)
-	}
-	if err := store.SetServiceLanguage(ctx, acc.ID, ""); err != nil {
-		t.Fatalf("noop service language: %v", err)
-	}
-	if got, err := store.GetByID(ctx, acc.ID); err != nil {
-		t.Fatalf("get by id: %v", err)
-	} else if got.ServiceLanguage != "en" {
-		t.Errorf("ServiceLanguage after update+noop = %q, want en", got.ServiceLanguage)
-	}
-}
-
 // TestHighRateFlagRoundTrip covers the soft high-rate marker: a fresh account
 // is unflagged, FlagHighRate stamps it exactly once (a second sustained episode
 // never moves the timestamp), ClearHighRateFlag reverses it, and a re-flag after
@@ -299,6 +259,7 @@ func TestNotificationsInAppOnlyRoundTrip(t *testing.T) {
 		PreferredLanguage:      "en",
 		TimeZone:               "UTC",
 		NotificationsInAppOnly: false,
+		VariantPreferences:     []string{"erudit_ru"},
 	})
 	if err != nil {
 		t.Fatalf("update profile: %v", err)

backend/internal/inttest/banner_console_test.go

@@ -256,7 +256,8 @@ func TestBannerSurvivesProfileUpdate(t *testing.T) {
 	id := provisionAccount(t)
 
 	body := `{"display_name":"Tester","preferred_language":"ru","time_zone":"UTC","away_start":"00:00",` +
-		`"away_end":"00:00","block_chat":false,"block_friend_requests":false,"notifications_in_app_only":true}`
+		`"away_end":"00:00","block_chat":false,"block_friend_requests":false,"notifications_in_app_only":true,` +
+		`"variant_preferences":["erudit_ru"]}`
 	rec := httptest.NewRecorder()
 	req := httptest.NewRequest(http.MethodPut, "/api/v1/user/profile", strings.NewReader(body))
 	req.Header.Set("X-User-ID", id.String())

backend/internal/inttest/email_test.go

@@ -6,6 +6,7 @@ import (
 	"context"
 	"errors"
 	"regexp"
+	"slices"
 	"testing"
 	"time"
 
@@ -134,12 +135,20 @@ func TestUpdateProfilePersists(t *testing.T) {
 	store := account.NewStore(testDB)
 	acc := provisionAccount(t)
 
+	// A fresh account defaults to Erudit only (the DB-level column default).
+	if def, err := store.GetByID(ctx, acc); err != nil {
+		t.Fatalf("get default: %v", err)
+	} else if want := []string{"erudit_ru"}; !slices.Equal(def.VariantPreferences, want) {
+		t.Errorf("default variant preferences = %v, want %v", def.VariantPreferences, want)
+	}
+
 	updated, err := store.UpdateProfile(ctx, acc, account.ProfileUpdate{
 		DisplayName:         "Kaya",
 		PreferredLanguage:   "ru",
 		TimeZone:            "Europe/Moscow",
 		BlockChat:           true,
 		BlockFriendRequests: true,
+		VariantPreferences:  []string{"scrabble_en", "erudit_ru"},
 	})
 	if err != nil {
 		t.Fatalf("update profile: %v", err)
@@ -157,6 +166,10 @@ func TestUpdateProfilePersists(t *testing.T) {
 	if reloaded.TimeZone != "Europe/Moscow" || !reloaded.BlockChat {
 		t.Errorf("profile did not persist: %+v", reloaded)
 	}
+	// The text[] column round-trips and is stored canonically (Erudit-first).
+	if want := []string{"erudit_ru", "scrabble_en"}; !slices.Equal(reloaded.VariantPreferences, want) {
+		t.Errorf("variant preferences = %v, want %v", reloaded.VariantPreferences, want)
+	}
 }
 
 // TestUpdateProfileOffsetTimezone checks the UTC-offset timezone: it is
@@ -167,9 +180,10 @@ func TestUpdateProfileOffsetTimezone(t *testing.T) {
 	acc := provisionAccount(t)
 
 	updated, err := store.UpdateProfile(ctx, acc, account.ProfileUpdate{
-		DisplayName:       "Kaya",
-		PreferredLanguage: "en",
-		TimeZone:          "+03:00",
+		DisplayName:        "Kaya",
+		PreferredLanguage:  "en",
+		TimeZone:           "+03:00",
+		VariantPreferences: []string{"erudit_ru"},
 	})
 	if err != nil {
 		t.Fatalf("update with offset timezone: %v", err)

backend/internal/inttest/feedback_test.go

@@ -145,48 +145,33 @@ func TestFeedbackReplyHiddenAfterNewMessage(t *testing.T) {
 	}
 }
 
-func TestFeedbackSnapshotsLanguages(t *testing.T) {
+func TestFeedbackSnapshotsLanguage(t *testing.T) {
 	ctx := context.Background()
 	svc := newFeedbackService()
 	acc := provisionAccount(t)
 	if _, err := testDB.ExecContext(ctx,
-		`UPDATE backend.accounts SET preferred_language = 'en', service_language = 'ru' WHERE account_id = $1`, acc); err != nil {
-		t.Fatalf("set languages: %v", err)
+		`UPDATE backend.accounts SET preferred_language = 'en' WHERE account_id = $1`, acc); err != nil {
+		t.Fatalf("set language: %v", err)
 	}
-	// A Telegram (connector) message snapshots both the interface language and the bot.
+	// A message snapshots the sender's interface language at submit time.
 	if err := svc.Submit(ctx, acc, "from telegram", nil, "", "telegram", ""); err != nil {
 		t.Fatalf("submit: %v", err)
 	}
 	id := latestFeedbackID(t, svc, acc)
 	if m, err := svc.AdminGet(ctx, id); err != nil {
 		t.Fatalf("admin get: %v", err)
-	} else if m.Lang != "en" || m.ChannelLang != "ru" {
-		t.Fatalf("snapshot = lang %q / channel_lang %q, want en / ru", m.Lang, m.ChannelLang)
+	} else if m.Lang != "en" {
+		t.Fatalf("snapshot = lang %q, want en", m.Lang)
 	}
 	// Changing the account afterwards must not change the stored snapshot.
 	if _, err := testDB.ExecContext(ctx,
-		`UPDATE backend.accounts SET preferred_language = 'ru', service_language = 'en' WHERE account_id = $1`, acc); err != nil {
-		t.Fatalf("change languages: %v", err)
+		`UPDATE backend.accounts SET preferred_language = 'ru' WHERE account_id = $1`, acc); err != nil {
+		t.Fatalf("change language: %v", err)
 	}
 	if m, err := svc.AdminGet(ctx, id); err != nil {
 		t.Fatal(err)
-	} else if m.Lang != "en" || m.ChannelLang != "ru" {
-		t.Fatalf("snapshot drifted after account change = lang %q / channel_lang %q", m.Lang, m.ChannelLang)
-	}
-
-	// A non-connector channel records no bot language even when the account has one.
-	acc2 := provisionAccount(t)
-	if _, err := testDB.ExecContext(ctx,
-		`UPDATE backend.accounts SET preferred_language = 'en', service_language = 'ru' WHERE account_id = $1`, acc2); err != nil {
-		t.Fatalf("set languages 2: %v", err)
-	}
-	if err := svc.Submit(ctx, acc2, "from web", nil, "", "web", ""); err != nil {
-		t.Fatalf("submit web: %v", err)
-	}
-	if m, err := svc.AdminGet(ctx, latestFeedbackID(t, svc, acc2)); err != nil {
-		t.Fatal(err)
-	} else if m.Lang != "en" || m.ChannelLang != "" {
-		t.Fatalf("web snapshot = lang %q / channel_lang %q, want en / empty", m.Lang, m.ChannelLang)
+	} else if m.Lang != "en" {
+		t.Fatalf("snapshot drifted after account change = lang %q, want en", m.Lang)
 	}
 }
 

backend/internal/inttest/game_limit_test.go

@@ -97,10 +97,12 @@ func TestGameLimitGate(t *testing.T) {
 	if !gamesListAtLimit(t, srv, human) {
 		t.Fatalf("at %d games at_game_limit must be true", game.MaxActiveQuickGames)
 	}
-	if rec := userPost(t, srv, "/api/v1/user/lobby/enqueue", human, `{"variant":"scrabble_en"}`); rec.Code != http.StatusConflict || errorCode(t, rec) != "game_limit_reached" {
+	// erudit_ru is in the default variant preferences, so the variant gate passes and the
+	// game-limit gate is what fires here.
+	if rec := userPost(t, srv, "/api/v1/user/lobby/enqueue", human, `{"variant":"erudit_ru"}`); rec.Code != http.StatusConflict || errorCode(t, rec) != "game_limit_reached" {
 		t.Fatalf("enqueue at limit = (%d, %q), want (409, game_limit_reached)", rec.Code, errorCode(t, rec))
 	}
-	invBody := fmt.Sprintf(`{"variant":"scrabble_en","invitee_ids":[%q]}`, opp.String())
+	invBody := fmt.Sprintf(`{"variant":"erudit_ru","invitee_ids":[%q]}`, opp.String())
 	if rec := userPost(t, srv, "/api/v1/user/invitations", human, invBody); rec.Code != http.StatusConflict || errorCode(t, rec) != "game_limit_reached" {
 		t.Fatalf("invitation at limit = (%d, %q), want (409, game_limit_reached)", rec.Code, errorCode(t, rec))
 	}

backend/internal/inttest/seat_display_name_test.go

@@ -37,7 +37,7 @@ func TestSeatNameFrozenAfterRename(t *testing.T) {
 
 	starter := provisionAccount(t)
 	if _, err := accounts.UpdateProfile(ctx, starter, account.ProfileUpdate{
-		DisplayName: "Original Name", PreferredLanguage: "en", TimeZone: "UTC",
+		DisplayName: "Original Name", PreferredLanguage: "en", TimeZone: "UTC", VariantPreferences: []string{"erudit_ru"},
 	}); err != nil {
 		t.Fatalf("set name: %v", err)
 	}
@@ -50,7 +50,7 @@ func TestSeatNameFrozenAfterRename(t *testing.T) {
 
 	// Rename the account; the snapshot on the already-taken seat must not follow.
 	if _, err := accounts.UpdateProfile(ctx, starter, account.ProfileUpdate{
-		DisplayName: "Renamed Player99", PreferredLanguage: "en", TimeZone: "UTC",
+		DisplayName: "Renamed Player99", PreferredLanguage: "en", TimeZone: "UTC", VariantPreferences: []string{"erudit_ru"},
 	}); err != nil {
 		t.Fatalf("rename: %v", err)
 	}

backend/internal/inttest/social_test.go

@@ -135,7 +135,7 @@ func TestFriendRequestRefusedByToggleAndBlock(t *testing.T) {
 
 	// Toggle: the addressee does not accept friend requests.
 	a, b := provisionAccount(t), provisionAccount(t)
-	if _, err := store.UpdateProfile(ctx, b, account.ProfileUpdate{DisplayName: "Player", PreferredLanguage: "en", TimeZone: "UTC", BlockFriendRequests: true}); err != nil {
+	if _, err := store.UpdateProfile(ctx, b, account.ProfileUpdate{DisplayName: "Player", PreferredLanguage: "en", TimeZone: "UTC", BlockFriendRequests: true, VariantPreferences: []string{"erudit_ru"}}); err != nil {
 		t.Fatalf("set toggle: %v", err)
 	}
 	if err := svc.SendFriendRequest(ctx, a, b); !errors.Is(err, social.ErrRequestBlocked) {
@@ -353,7 +353,7 @@ func TestChatPostListAndBlocks(t *testing.T) {
 	if _, err := svc.PostMessage(ctx, other, seats2[0], "hi", ""); err != nil {
 		t.Fatalf("post 2: %v", err)
 	}
-	if _, err := store.UpdateProfile(ctx, seats2[1], account.ProfileUpdate{DisplayName: "Player", PreferredLanguage: "en", TimeZone: "UTC", BlockChat: true}); err != nil {
+	if _, err := store.UpdateProfile(ctx, seats2[1], account.ProfileUpdate{DisplayName: "Player", PreferredLanguage: "en", TimeZone: "UTC", BlockChat: true, VariantPreferences: []string{"erudit_ru"}}); err != nil {
 		t.Fatalf("set block_chat: %v", err)
 	}
 	if msgs, _ := svc.Messages(ctx, other, seats2[1]); len(msgs) != 0 {
@@ -588,32 +588,6 @@ func TestRespondPublishesToRequester(t *testing.T) {
 	}
 }
 
-// TestNudgeRoutedByGameLanguage checks a nudge's out-of-app push carries the game's language, so
-// it is delivered by the game's bot rather than the recipient's last-login bot.
-func TestNudgeRoutedByGameLanguage(t *testing.T) {
-	ctx := context.Background()
-	svc := newSocialService()
-	pub := &capturePublisher{}
-	svc.SetNotifier(pub)
-
-	gameID, seats := newGameWithSeats(t, 2) // an English game; seat 0 is to move
-	if _, err := svc.Nudge(ctx, gameID, seats[1]); err != nil {
-		t.Fatalf("nudge: %v", err)
-	}
-	found := false
-	for _, in := range pub.intents {
-		if in.Kind == notify.KindNudge {
-			found = true
-			if in.Language != "en" {
-				t.Errorf("nudge language = %q, want en (the game's language)", in.Language)
-			}
-		}
-	}
-	if !found {
-		t.Fatal("no nudge intent published")
-	}
-}
-
 // TestAdminListMessages checks the admin moderation list: real messages only
 // (nudges excluded), the game / sender pins, the sender glob masks, and the source label.
 func TestAdminListMessages(t *testing.T) {

backend/internal/inttest/variant_preference_test.go

@@ -0,0 +1,51 @@
+//go:build integration
+
+package inttest
+
+import (
+	"fmt"
+	"net/http"
+	"testing"
+	"time"
+
+	"go.uber.org/zap/zaptest"
+
+	"scrabble/backend/internal/account"
+	"scrabble/backend/internal/server"
+)
+
+// TestVariantPreferenceGate covers the New Game gate: a player may start a quick game
+// or create a friend invitation only in a variant they have enabled in their profile
+// (a fresh account defaults to Erudit only), and any other variant is refused with 400.
+// The complementary case — an invited friend accepting an invitation in a variant they
+// have NOT enabled — is exercised by TestGameLimitGate, where a default-Erudit human
+// accepts an English invitation over HTTP.
+func TestVariantPreferenceGate(t *testing.T) {
+	clearOpenGames(t)
+	srv := server.New(":0", server.Deps{
+		Logger:      zaptest.NewLogger(t),
+		DB:          testDB,
+		Accounts:    account.NewStore(testDB),
+		Games:       newGameService(),
+		Matchmaker:  newMatchmaker(t, newRobotService(t, newGameService()), time.Minute, 0),
+		Invitations: newInvitationService(),
+	})
+
+	human := provisionAccount(t) // default preferences: erudit_ru only
+	opp := provisionAccount(t)
+
+	// A variant outside the player's preferences is refused on both create paths.
+	if rec := userPost(t, srv, "/api/v1/user/lobby/enqueue", human, `{"variant":"scrabble_en"}`); rec.Code != http.StatusBadRequest {
+		t.Fatalf("enqueue non-preferred variant = %d (%s), want 400", rec.Code, rec.Body.String())
+	}
+	invBody := fmt.Sprintf(`{"variant":"scrabble_en","invitee_ids":[%q]}`, opp.String())
+	if rec := userPost(t, srv, "/api/v1/user/invitations", human, invBody); rec.Code != http.StatusBadRequest {
+		t.Fatalf("invitation non-preferred variant = %d (%s), want 400", rec.Code, rec.Body.String())
+	}
+
+	// The default-enabled variant (Erudit) is allowed: the quick enqueue opens a game.
+	if rec := userPost(t, srv, "/api/v1/user/lobby/enqueue", human, `{"variant":"erudit_ru"}`); rec.Code != http.StatusOK {
+		t.Fatalf("enqueue preferred variant = %d (%s), want 200", rec.Code, rec.Body.String())
+	}
+	clearOpenGames(t)
+}

backend/internal/lobby/matchmaker.go

@@ -206,7 +206,6 @@ func (m *Matchmaker) announceOpponent(ctx context.Context, g game.Game, joinerID
 		return
 	}
 	intent := notify.OpponentJoined(starter, g.ID, state)
-	intent.Language = g.Variant.Language()
 	m.pub.Publish(intent)
 }
 

backend/internal/notify/notify.go

@@ -82,11 +82,6 @@ type Intent struct {
 	Kind    string
 	Payload []byte
 	EventID string
-	// Language routes an out-of-app push to a specific per-language bot: for a
-	// game event it is the game's language ("en"/"ru"), so the notification comes from the
-	// game's bot rather than the recipient's last-login bot. Empty falls back to the
-	// recipient's service language at the gateway.
-	Language string
 }
 
 // Publisher accepts live-event intents. Implementations must be safe for

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

@@ -9,6 +9,7 @@ package model
 
 import (
 	"github.com/google/uuid"
+	"github.com/lib/pq"
 	"time"
 )
 
@@ -29,6 +30,6 @@ type Accounts struct {
 	PaidAccount            bool
 	MergedInto             *uuid.UUID
 	MergedAt               *time.Time
-	ServiceLanguage        *string
 	FlaggedHighRateAt      *time.Time
+	VariantPreferences     pq.StringArray
 }

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

@@ -20,12 +20,11 @@ type FeedbackMessages struct {
 	AttachmentName *string
 	SenderIP       *string
 	Channel        string
-	Lang           *string
-	ChannelLang    *string
 	ReadAt         *time.Time
 	ArchivedAt     *time.Time
 	ReplyBody      *string
 	RepliedAt      *time.Time
 	ReplyReadAt    *time.Time
 	CreatedAt      time.Time
+	Lang           *string
 }

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

@@ -33,8 +33,8 @@ type accountsTable struct {
 	PaidAccount            postgres.ColumnBool
 	MergedInto             postgres.ColumnString
 	MergedAt               postgres.ColumnTimestampz
-	ServiceLanguage        postgres.ColumnString
 	FlaggedHighRateAt      postgres.ColumnTimestampz
+	VariantPreferences     postgres.ColumnStringArray
 
 	AllColumns     postgres.ColumnList
 	MutableColumns postgres.ColumnList
@@ -92,11 +92,11 @@ func newAccountsTableImpl(schemaName, tableName, alias string) accountsTable {
 		PaidAccountColumn            = postgres.BoolColumn("paid_account")
 		MergedIntoColumn             = postgres.StringColumn("merged_into")
 		MergedAtColumn               = postgres.TimestampzColumn("merged_at")
-		ServiceLanguageColumn        = postgres.StringColumn("service_language")
 		FlaggedHighRateAtColumn      = postgres.TimestampzColumn("flagged_high_rate_at")
-		allColumns                   = postgres.ColumnList{AccountIDColumn, DisplayNameColumn, PreferredLanguageColumn, TimeZoneColumn, BlockChatColumn, BlockFriendRequestsColumn, CreatedAtColumn, UpdatedAtColumn, AwayStartColumn, AwayEndColumn, HintBalanceColumn, IsGuestColumn, NotificationsInAppOnlyColumn, PaidAccountColumn, MergedIntoColumn, MergedAtColumn, ServiceLanguageColumn, FlaggedHighRateAtColumn}
-		mutableColumns               = postgres.ColumnList{DisplayNameColumn, PreferredLanguageColumn, TimeZoneColumn, BlockChatColumn, BlockFriendRequestsColumn, CreatedAtColumn, UpdatedAtColumn, AwayStartColumn, AwayEndColumn, HintBalanceColumn, IsGuestColumn, NotificationsInAppOnlyColumn, PaidAccountColumn, MergedIntoColumn, MergedAtColumn, ServiceLanguageColumn, FlaggedHighRateAtColumn}
-		defaultColumns               = postgres.ColumnList{DisplayNameColumn, PreferredLanguageColumn, TimeZoneColumn, BlockChatColumn, BlockFriendRequestsColumn, CreatedAtColumn, UpdatedAtColumn, AwayStartColumn, AwayEndColumn, HintBalanceColumn, IsGuestColumn, NotificationsInAppOnlyColumn, PaidAccountColumn}
+		VariantPreferencesColumn     = postgres.StringArrayColumn("variant_preferences")
+		allColumns                   = postgres.ColumnList{AccountIDColumn, DisplayNameColumn, PreferredLanguageColumn, TimeZoneColumn, BlockChatColumn, BlockFriendRequestsColumn, CreatedAtColumn, UpdatedAtColumn, AwayStartColumn, AwayEndColumn, HintBalanceColumn, IsGuestColumn, NotificationsInAppOnlyColumn, PaidAccountColumn, MergedIntoColumn, MergedAtColumn, FlaggedHighRateAtColumn, VariantPreferencesColumn}
+		mutableColumns               = postgres.ColumnList{DisplayNameColumn, PreferredLanguageColumn, TimeZoneColumn, BlockChatColumn, BlockFriendRequestsColumn, CreatedAtColumn, UpdatedAtColumn, AwayStartColumn, AwayEndColumn, HintBalanceColumn, IsGuestColumn, NotificationsInAppOnlyColumn, PaidAccountColumn, MergedIntoColumn, MergedAtColumn, FlaggedHighRateAtColumn, VariantPreferencesColumn}
+		defaultColumns               = postgres.ColumnList{DisplayNameColumn, PreferredLanguageColumn, TimeZoneColumn, BlockChatColumn, BlockFriendRequestsColumn, CreatedAtColumn, UpdatedAtColumn, AwayStartColumn, AwayEndColumn, HintBalanceColumn, IsGuestColumn, NotificationsInAppOnlyColumn, PaidAccountColumn, VariantPreferencesColumn}
 	)
 
 	return accountsTable{
@@ -119,8 +119,8 @@ func newAccountsTableImpl(schemaName, tableName, alias string) accountsTable {
 		PaidAccount:            PaidAccountColumn,
 		MergedInto:             MergedIntoColumn,
 		MergedAt:               MergedAtColumn,
-		ServiceLanguage:        ServiceLanguageColumn,
 		FlaggedHighRateAt:      FlaggedHighRateAtColumn,
+		VariantPreferences:     VariantPreferencesColumn,
 
 		AllColumns:     allColumns,
 		MutableColumns: mutableColumns,

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

@@ -24,14 +24,13 @@ type feedbackMessagesTable struct {
 	AttachmentName postgres.ColumnString
 	SenderIP       postgres.ColumnString
 	Channel        postgres.ColumnString
-	Lang           postgres.ColumnString
-	ChannelLang    postgres.ColumnString
 	ReadAt         postgres.ColumnTimestampz
 	ArchivedAt     postgres.ColumnTimestampz
 	ReplyBody      postgres.ColumnString
 	RepliedAt      postgres.ColumnTimestampz
 	ReplyReadAt    postgres.ColumnTimestampz
 	CreatedAt      postgres.ColumnTimestampz
+	Lang           postgres.ColumnString
 
 	AllColumns     postgres.ColumnList
 	MutableColumns postgres.ColumnList
@@ -80,16 +79,15 @@ func newFeedbackMessagesTableImpl(schemaName, tableName, alias string) feedbackM
 		AttachmentNameColumn = postgres.StringColumn("attachment_name")
 		SenderIPColumn       = postgres.StringColumn("sender_ip")
 		ChannelColumn        = postgres.StringColumn("channel")
-		LangColumn           = postgres.StringColumn("lang")
-		ChannelLangColumn    = postgres.StringColumn("channel_lang")
 		ReadAtColumn         = postgres.TimestampzColumn("read_at")
 		ArchivedAtColumn     = postgres.TimestampzColumn("archived_at")
 		ReplyBodyColumn      = postgres.StringColumn("reply_body")
 		RepliedAtColumn      = postgres.TimestampzColumn("replied_at")
 		ReplyReadAtColumn    = postgres.TimestampzColumn("reply_read_at")
 		CreatedAtColumn      = postgres.TimestampzColumn("created_at")
-		allColumns           = postgres.ColumnList{MessageIDColumn, AccountIDColumn, BodyColumn, AttachmentColumn, AttachmentNameColumn, SenderIPColumn, ChannelColumn, LangColumn, ChannelLangColumn, ReadAtColumn, ArchivedAtColumn, ReplyBodyColumn, RepliedAtColumn, ReplyReadAtColumn, CreatedAtColumn}
-		mutableColumns       = postgres.ColumnList{AccountIDColumn, BodyColumn, AttachmentColumn, AttachmentNameColumn, SenderIPColumn, ChannelColumn, LangColumn, ChannelLangColumn, ReadAtColumn, ArchivedAtColumn, ReplyBodyColumn, RepliedAtColumn, ReplyReadAtColumn, CreatedAtColumn}
+		LangColumn           = postgres.StringColumn("lang")
+		allColumns           = postgres.ColumnList{MessageIDColumn, AccountIDColumn, BodyColumn, AttachmentColumn, AttachmentNameColumn, SenderIPColumn, ChannelColumn, ReadAtColumn, ArchivedAtColumn, ReplyBodyColumn, RepliedAtColumn, ReplyReadAtColumn, CreatedAtColumn, LangColumn}
+		mutableColumns       = postgres.ColumnList{AccountIDColumn, BodyColumn, AttachmentColumn, AttachmentNameColumn, SenderIPColumn, ChannelColumn, ReadAtColumn, ArchivedAtColumn, ReplyBodyColumn, RepliedAtColumn, ReplyReadAtColumn, CreatedAtColumn, LangColumn}
 		defaultColumns       = postgres.ColumnList{CreatedAtColumn}
 	)
 
@@ -104,14 +102,13 @@ func newFeedbackMessagesTableImpl(schemaName, tableName, alias string) feedbackM
 		AttachmentName: AttachmentNameColumn,
 		SenderIP:       SenderIPColumn,
 		Channel:        ChannelColumn,
-		Lang:           LangColumn,
-		ChannelLang:    ChannelLangColumn,
 		ReadAt:         ReadAtColumn,
 		ArchivedAt:     ArchivedAtColumn,
 		ReplyBody:      ReplyBodyColumn,
 		RepliedAt:      RepliedAtColumn,
 		ReplyReadAt:    ReplyReadAtColumn,
 		CreatedAt:      CreatedAtColumn,
+		Lang:           LangColumn,
 
 		AllColumns:     allColumns,
 		MutableColumns: mutableColumns,

backend/internal/postgres/migrations/00014_single_bot_variant_preferences.sql

@@ -0,0 +1,45 @@
+-- +goose Up
+-- Single-bot collapse + per-user variant preferences.
+--
+-- With one Telegram bot there is no longer a "service language" (which bot a player
+-- signed in through), and variant availability is no longer gated by the bot's
+-- supported languages but by an explicit per-account preference. variant_preferences
+-- is the set of game variants (engine.Variant stable labels) a player is willing to be
+-- matched into: it gates the New Game picker and the matchmaker, while an invited friend
+-- may still accept any variant. New accounts default to Erudit only (a DB-level default,
+-- so no application seed is needed); the set may never be empty and must be a subset of
+-- the three known variants. feedback_messages.channel_lang (the bot a message arrived
+-- through) likewise loses meaning under one bot and is dropped; the sender's interface
+-- language (lang) is kept.
+SET search_path = backend, pg_catalog;
+
+ALTER TABLE accounts
+    ADD COLUMN variant_preferences text[] NOT NULL DEFAULT ARRAY['erudit_ru']::text[],
+    ADD CONSTRAINT accounts_variant_preferences_nonempty_chk
+        CHECK (cardinality(variant_preferences) >= 1),
+    ADD CONSTRAINT accounts_variant_preferences_subset_chk
+        CHECK (variant_preferences <@ ARRAY['scrabble_en', 'scrabble_ru', 'erudit_ru']::text[]);
+
+ALTER TABLE accounts DROP COLUMN service_language;
+
+ALTER TABLE feedback_messages DROP COLUMN channel_lang;
+
+-- The auto-match pairing query filters open games by (variant, multiple_words_per_turn)
+-- and takes the oldest by created_at; games_open_idx (open_deadline_at) does not serve it.
+-- A partial index over open games turns the scan-and-sort into a single index seek.
+CREATE INDEX games_open_match_idx ON games (variant, multiple_words_per_turn, created_at)
+    WHERE status = 'open';
+
+-- +goose Down
+SET search_path = backend, pg_catalog;
+
+DROP INDEX games_open_match_idx;
+
+ALTER TABLE feedback_messages ADD COLUMN channel_lang text;
+
+ALTER TABLE accounts ADD COLUMN service_language text CHECK (service_language IN ('en', 'ru'));
+
+ALTER TABLE accounts
+    DROP CONSTRAINT accounts_variant_preferences_subset_chk,
+    DROP CONSTRAINT accounts_variant_preferences_nonempty_chk,
+    DROP COLUMN variant_preferences;

backend/internal/pushgrpc/server.go

@@ -54,11 +54,10 @@ func (s *Service) Subscribe(req *pushv1.SubscribeRequest, stream grpc.ServerStre
 				return nil
 			}
 			ev := &pushv1.Event{
-				UserId:   in.UserID.String(),
-				Kind:     in.Kind,
-				Payload:  in.Payload,
-				EventId:  in.EventID,
-				Language: in.Language,
+				UserId:  in.UserID.String(),
+				Kind:    in.Kind,
+				Payload: in.Payload,
+				EventId: in.EventID,
 			}
 			if err := stream.Send(ev); err != nil {
 				return err

backend/internal/server/banner.go

@@ -88,13 +88,9 @@ func (s *Server) bannerFor(ctx context.Context, acc account.Account) *bannerDTO
 	}
 }
 
-// bannerLang resolves the message language for a viewer: the bot (service)
-// language they last signed in through, falling back to the interface language
-// and then English.
+// bannerLang resolves the message language for a viewer: their interface language
+// (Russian, or English by default).
 func bannerLang(acc account.Account) string {
-	if acc.ServiceLanguage == "ru" || acc.ServiceLanguage == "en" {
-		return acc.ServiceLanguage
-	}
 	if acc.PreferredLanguage == "ru" {
 		return "ru"
 	}

backend/internal/server/dto.go

@@ -16,11 +16,10 @@ import (
 
 // sessionResponse is the credential returned by every auth endpoint.
 type sessionResponse struct {
-	Token           string `json:"token"`
-	UserID          string `json:"user_id"`
-	IsGuest         bool   `json:"is_guest"`
-	DisplayName     string `json:"display_name"`
-	ServiceLanguage string `json:"service_language"`
+	Token       string `json:"token"`
+	UserID      string `json:"user_id"`
+	IsGuest     bool   `json:"is_guest"`
+	DisplayName string `json:"display_name"`
 }
 
 // okResponse is a simple success acknowledgement.
@@ -49,6 +48,10 @@ type profileResponse struct {
 	BlockFriendRequests    bool   `json:"block_friend_requests"`
 	IsGuest                bool   `json:"is_guest"`
 	NotificationsInAppOnly bool   `json:"notifications_in_app_only"`
+	// VariantPreferences is the set of game variants the player allows themselves to
+	// be matched into (engine.Variant stable labels), Erudit-first. It gates the New
+	// Game picker and the matchmaker; never empty.
+	VariantPreferences []string `json:"variant_preferences"`
 	// Banner is the advertising-banner block: present only for a viewer eligible to
 	// see the banner (a free account with an empty hint wallet and without the
 	// no_banner role), absent otherwise. See banner.go.
@@ -177,11 +180,10 @@ type errorBody struct {
 // sessionResponseFor builds the credential payload for a minted session.
 func sessionResponseFor(token string, acc account.Account) sessionResponse {
 	return sessionResponse{
-		Token:           token,
-		UserID:          acc.ID.String(),
-		IsGuest:         acc.IsGuest,
-		DisplayName:     acc.DisplayName,
-		ServiceLanguage: acc.ServiceLanguage,
+		Token:       token,
+		UserID:      acc.ID.String(),
+		IsGuest:     acc.IsGuest,
+		DisplayName: acc.DisplayName,
 	}
 }
 
@@ -199,6 +201,7 @@ func profileResponseFor(acc account.Account) profileResponse {
 		BlockFriendRequests:    acc.BlockFriendRequests,
 		IsGuest:                acc.IsGuest,
 		NotificationsInAppOnly: acc.NotificationsInAppOnly,
+		VariantPreferences:     acc.VariantPreferences,
 	}
 }
 

backend/internal/server/handlers_account.go

@@ -18,14 +18,15 @@ import (
 // updateProfileRequest is the full editable profile. away_start/away_end are
 // "HH:MM" local-time bounds of the daily away window.
 type updateProfileRequest struct {
-	DisplayName            string `json:"display_name"`
-	PreferredLanguage      string `json:"preferred_language"`
-	TimeZone               string `json:"time_zone"`
-	AwayStart              string `json:"away_start"`
-	AwayEnd                string `json:"away_end"`
-	BlockChat              bool   `json:"block_chat"`
-	BlockFriendRequests    bool   `json:"block_friend_requests"`
-	NotificationsInAppOnly bool   `json:"notifications_in_app_only"`
+	DisplayName            string   `json:"display_name"`
+	PreferredLanguage      string   `json:"preferred_language"`
+	TimeZone               string   `json:"time_zone"`
+	AwayStart              string   `json:"away_start"`
+	AwayEnd                string   `json:"away_end"`
+	BlockChat              bool     `json:"block_chat"`
+	BlockFriendRequests    bool     `json:"block_friend_requests"`
+	NotificationsInAppOnly bool     `json:"notifications_in_app_only"`
+	VariantPreferences     []string `json:"variant_preferences"`
 }
 
 // statsDTO is a durable account's lifetime statistics (the derived games-played and
@@ -92,6 +93,7 @@ func (s *Server) handleUpdateProfile(c *gin.Context) {
 		BlockChat:              req.BlockChat,
 		BlockFriendRequests:    req.BlockFriendRequests,
 		NotificationsInAppOnly: req.NotificationsInAppOnly,
+		VariantPreferences:     req.VariantPreferences,
 	})
 	if err != nil {
 		s.abortErr(c, err)

backend/internal/server/handlers_admin_console.go

@@ -424,7 +424,6 @@ func (s *Server) consoleUserMessage(c *gin.Context) {
 	}
 	back := "/_gm/users/" + id.String()
 	text := trimForm(c, "text")
-	language := trimForm(c, "language")
 	switch {
 	case text == "":
 		s.renderConsoleMessage(c, "Nothing sent", "the message was empty", back)
@@ -436,14 +435,14 @@ func (s *Server) consoleUserMessage(c *gin.Context) {
 			s.renderConsoleMessage(c, "No Telegram", "this account has no Telegram identity", back)
 			return
 		}
-		delivered, err := s.connector.SendToUser(ctx, ext, text, language)
+		delivered, err := s.connector.SendToUser(ctx, ext, text)
 		if err != nil {
 			s.consoleError(c, err)
 			return
 		}
 		body := "message delivered"
 		if !delivered {
-			body = "not delivered (the user may not have started that bot)"
+			body = "not delivered (the user may not have started the bot)"
 		}
 		s.renderConsoleMessage(c, "Sent", body, back)
 	}
@@ -833,21 +832,20 @@ func (s *Server) consoleBroadcast(c *gin.Context) {
 // consolePostBroadcast posts an operator message to the connector's game channel.
 func (s *Server) consolePostBroadcast(c *gin.Context) {
 	text := trimForm(c, "text")
-	language := trimForm(c, "language")
 	switch {
 	case text == "":
 		s.renderConsoleMessage(c, "Nothing sent", "the message was empty", "/_gm/broadcast")
 	case s.connector == nil:
 		s.renderConsoleMessage(c, "Not configured", "the connector is not configured (set BACKEND_CONNECTOR_ADDR)", "/_gm/broadcast")
 	default:
-		delivered, err := s.connector.SendToGameChannel(c.Request.Context(), text, language)
+		delivered, err := s.connector.SendToGameChannel(c.Request.Context(), text)
 		if err != nil {
 			s.consoleError(c, err)
 			return
 		}
 		body := "posted to the game channel"
 		if !delivered {
-			body = "not delivered (that bot has no game channel configured)"
+			body = "not delivered (the bot has no game channel configured)"
 		}
 		s.renderConsoleMessage(c, "Broadcast", body, "/_gm/broadcast")
 	}

backend/internal/server/handlers_admin_feedback.go

@@ -79,7 +79,7 @@ func (s *Server) consoleFeedbackDetail(c *gin.Context) {
 	}
 	view := adminconsole.FeedbackDetailView{
 		ID: m.ID.String(), AccountID: m.AccountID.String(), SenderName: m.SenderName,
-		Source: m.Source, Channel: m.Channel, InterfaceLanguage: m.Lang, BotLanguage: m.ChannelLang,
+		Source: m.Source, Channel: m.Channel, InterfaceLanguage: m.Lang,
 		IP: m.SenderIP, Body: m.Body,
 		HasAttachment: m.HasAttachment, AttachmentName: m.AttachmentName, IsImage: feedback.IsImage(m.AttachmentName),
 		Read: m.Read, Archived: m.Archived, Replied: m.Replied, ReplyBody: m.ReplyBody,

backend/internal/server/handlers_auth.go

@@ -19,20 +19,16 @@ import (
 // telegramAuthRequest carries the identity the connector extracted from a
 // validated initData payload. Username, FirstName and LanguageCode seed a
 // brand-new account's display name and language (first contact only).
-// ServiceLanguage is the validating bot's language tag (en/ru); it is recorded on
-// every login (the bot the user last came through) and routes their out-of-app push.
 type telegramAuthRequest struct {
-	ExternalID      string `json:"external_id"`
-	Username        string `json:"username"`
-	FirstName       string `json:"first_name"`
-	LanguageCode    string `json:"language_code"`
-	ServiceLanguage string `json:"service_language"`
+	ExternalID   string `json:"external_id"`
+	Username     string `json:"username"`
+	FirstName    string `json:"first_name"`
+	LanguageCode string `json:"language_code"`
 }
 
 // handleTelegramAuth provisions (or finds) the account bound to a Telegram
 // identity and mints a session for it, seeding a new account's display name and
-// language from the supplied Telegram fields and recording the validating bot's
-// service language (updated every login) so out-of-app push routes to that bot.
+// language from the supplied Telegram fields (first contact only).
 func (s *Server) handleTelegramAuth(c *gin.Context) {
 	var req telegramAuthRequest
 	if err := c.ShouldBindJSON(&req); err != nil || req.ExternalID == "" {
@@ -44,11 +40,6 @@ func (s *Server) handleTelegramAuth(c *gin.Context) {
 		s.abortErr(c, err)
 		return
 	}
-	if err := s.accounts.SetServiceLanguage(c.Request.Context(), acc.ID, req.ServiceLanguage); err != nil {
-		s.abortErr(c, err)
-		return
-	}
-	acc.ServiceLanguage = req.ServiceLanguage // reflect this login's bot in the session response
 	s.mintSession(c, acc)
 }
 
@@ -59,10 +50,9 @@ type pushTargetRequest struct {
 
 // pushTargetResponse carries what the gateway needs to route an out-of-app push:
 // the recipient's Telegram external_id (empty when they have no Telegram
-// identity, e.g. a guest or email-only account), the language that both selects the
-// delivering bot and renders the message (the account's service language, the bot
-// it last signed in through, falling back to its preferred language), and whether
-// they confined notifications to the in-app stream.
+// identity, e.g. a guest or email-only account), the language the single bot renders
+// the message in (the account's interface language), and whether they confined
+// notifications to the in-app stream.
 type pushTargetResponse struct {
 	ExternalID             string `json:"external_id"`
 	Language               string `json:"language"`
@@ -94,15 +84,9 @@ func (s *Server) handlePushTarget(c *gin.Context) {
 		s.abortErr(c, err)
 		return
 	}
-	// Route by the bot the user last signed in through; fall back to the interface
-	// language for an account that has never come through a tagged bot.
-	language := acc.ServiceLanguage
-	if language == "" {
-		language = acc.PreferredLanguage
-	}
 	c.JSON(http.StatusOK, pushTargetResponse{
 		ExternalID:             ext,
-		Language:               language,
+		Language:               acc.PreferredLanguage,
 		NotificationsInAppOnly: acc.NotificationsInAppOnly,
 	})
 }

backend/internal/server/handlers_invitations.go

@@ -104,6 +104,9 @@ func (s *Server) handleCreateInvitation(c *gin.Context) {
 		abortBadRequest(c, "unknown variant")
 		return
 	}
+	if !s.ensureVariantAllowed(c, uid, variant.String()) {
+		return
+	}
 	settings := lobby.InvitationSettings{
 		Variant:              variant,
 		HintsAllowed:         req.HintsAllowed,

backend/internal/server/handlers_user.go

@@ -2,8 +2,10 @@ package server
 
 import (
 	"net/http"
+	"slices"
 
 	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
 
 	"scrabble/backend/internal/engine"
 )
@@ -134,6 +136,24 @@ func (s *Server) handleGameState(c *gin.Context) {
 	c.JSON(http.StatusOK, dto)
 }
 
+// ensureVariantAllowed reports whether the caller's profile permits creating a game
+// of variant — it must be one of their VariantPreferences. It aborts the request
+// with 400 and returns false otherwise. Only the player who creates a game (quick
+// match, vs-AI or a friend invitation) is gated this way; an invited friend may
+// accept an invitation in any variant.
+func (s *Server) ensureVariantAllowed(c *gin.Context, uid uuid.UUID, variant string) bool {
+	acc, err := s.accounts.GetByID(c.Request.Context(), uid)
+	if err != nil {
+		s.abortErr(c, err)
+		return false
+	}
+	if !slices.Contains(acc.VariantPreferences, variant) {
+		abortBadRequest(c, "variant is not in your preferences")
+		return false
+	}
+	return true
+}
+
 // enqueueRequest enters per-variant auto-match under a per-turn word rule. VsAI true
 // starts an honest-AI game against a robot instead of the open/wait matchmaking path.
 type enqueueRequest struct {
@@ -162,6 +182,9 @@ func (s *Server) handleEnqueue(c *gin.Context) {
 		abortBadRequest(c, "unknown variant")
 		return
 	}
+	if !s.ensureVariantAllowed(c, uid, variant.String()) {
+		return
+	}
 	if !s.ensureUnderGameLimit(c, uid) {
 		return
 	}

backend/internal/social/chat.go

@@ -206,9 +206,6 @@ func (svc *Service) Nudge(ctx context.Context, gameID, senderID uuid.UUID) (Mess
 		// read "<name>: …"; an unresolved name (best-effort) falls back to the plain phrase.
 		senderName, _ := svc.games.SeatName(ctx, gameID, senderID)
 		nudge := notify.Nudge(target, gameID, senderID, senderName)
-		if lang, err := svc.games.GameLanguage(ctx, gameID); err == nil {
-			nudge.Language = lang // route by the game's bot, not the recipient's last-login one
-		}
 		svc.pub.Publish(nudge)
 	}
 	return msg, nil

backend/internal/social/social.go

@@ -44,9 +44,6 @@ type GameReader interface {
 	// one-chat-message-per-turn limit (a message counts toward the current turn when it
 	// was posted at or after this time).
 	TurnStartedAt(ctx context.Context, gameID uuid.UUID) (time.Time, error)
-	// GameLanguage is the game's language tag ("en"/"ru"), so a nudge's out-of-app push routes
-	// to the game's bot rather than the recipient's last-login bot.
-	GameLanguage(ctx context.Context, gameID uuid.UUID) (string, error)
 	// VsAI reports whether the game is an honest-AI game, in which chat and nudge are
 	// both disabled (the game still reports status 'active').
 	VsAI(ctx context.Context, gameID uuid.UUID) (bool, error)