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.

gateway/README.md

@@ -77,7 +77,6 @@ connector (`ValidateLoginWidget`) and forward the trusted `external_id`. These
 | `GATEWAY_BACKEND_TIMEOUT` | `5s` | per backend REST call |
 | `GATEWAY_ADMIN_USER` / `GATEWAY_ADMIN_PASSWORD` | unset | enable + guard the admin console at `/_gm` |
 | `GATEWAY_CONNECTOR_ADDR` | unset | Telegram connector gRPC address (enables initData validation + out-of-app push) |
-| `GATEWAY_DEFAULT_SUPPORTED_LANGUAGES` | `en,ru` | New Game variant gating set placed on the Session for non-platform logins (web / email / guest); a deployment may narrow it |
 | `GATEWAY_SESSION_TTL` | `10m` | cached session lifetime |
 | `GATEWAY_SESSION_CACHE_MAX` | `50000` | cached session cap |
 | `GATEWAY_PUSH_HEARTBEAT_INTERVAL` | `10s` | live-stream keep-alive (an immediate heartbeat also fires on open, under the ~15s edge idle timeout) |

gateway/cmd/gateway/main.go

@@ -126,7 +126,7 @@ func run(ctx context.Context, cfg config.Config, logger *zap.Logger) error {
 		logger.Info("admin console disabled (set GATEWAY_ADMIN_USER and GATEWAY_ADMIN_PASSWORD)")
 	}
 
-	registry := transcode.NewRegistry(backend, validator, cfg.DefaultSupportedLanguages...)
+	registry := transcode.NewRegistry(backend, validator)
 	edge := connectsrv.NewServer(connectsrv.Deps{
 		Registry:     registry,
 		Sessions:     sessions,
@@ -258,7 +258,7 @@ func runPushPump(ctx context.Context, backend *backendclient.Client, hub *push.H
 			// deliver the event over the platform push channel. Done in a goroutine
 			// so a slow connector never stalls the in-app firehose.
 			if conn != nil && connector.OutOfAppKind(ev.GetKind()) && !hub.HasSubscribers(ev.GetUserId()) {
-				go deliverOutOfApp(ctx, backend, conn, ev.GetUserId(), ev.GetKind(), ev.GetPayload(), ev.GetLanguage(), logger)
+				go deliverOutOfApp(ctx, backend, conn, ev.GetUserId(), ev.GetKind(), ev.GetPayload(), logger)
 			}
 		}
 		if !sleep(ctx, pushReconnectDelay) {
@@ -271,7 +271,7 @@ func runPushPump(ctx context.Context, backend *backendclient.Client, hub *push.H
 // Telegram identity and have not confined notifications to the app, asks the
 // connector to deliver the event. It is best-effort: every failure is logged and
 // dropped (the in-app stream remains the primary channel).
-func deliverOutOfApp(ctx context.Context, backend *backendclient.Client, conn *connector.Client, userID, kind string, payload []byte, gameLang string, logger *zap.Logger) {
+func deliverOutOfApp(ctx context.Context, backend *backendclient.Client, conn *connector.Client, userID, kind string, payload []byte, logger *zap.Logger) {
 	target, err := backend.PushTarget(ctx, userID)
 	if err != nil {
 		logger.Warn("push target lookup failed", zap.String("user_id", userID), zap.Error(err))
@@ -280,13 +280,8 @@ func deliverOutOfApp(ctx context.Context, backend *backendclient.Client, conn *c
 	if !connector.DeliverToTarget(target.ExternalID, target.NotificationsInAppOnly) {
 		return
 	}
-	// A game event carries its own language, so the push comes from the game's bot rather than
-	// the recipient's last-login bot; other events fall back to the service language.
-	lang := target.Language
-	if gameLang != "" {
-		lang = gameLang
-	}
-	if _, err := conn.Notify(ctx, target.ExternalID, kind, payload, lang); err != nil {
+	// The single bot renders the message in the recipient's interface language.
+	if _, err := conn.Notify(ctx, target.ExternalID, kind, payload, target.Language); err != nil {
 		logger.Warn("out-of-app notify failed", zap.String("kind", kind), zap.Error(err))
 	}
 }

gateway/internal/backendclient/api.go

@@ -14,26 +14,26 @@ import (
 
 // SessionResp is the credential minted by an auth operation.
 type SessionResp 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"`
 }
 
 // ProfileResp is an account's own profile.
 type ProfileResp struct {
-	UserID                 string `json:"user_id"`
-	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"`
-	HintBalance            int    `json:"hint_balance"`
-	BlockChat              bool   `json:"block_chat"`
-	BlockFriendRequests    bool   `json:"block_friend_requests"`
-	IsGuest                bool   `json:"is_guest"`
-	NotificationsInAppOnly bool   `json:"notifications_in_app_only"`
+	UserID                 string   `json:"user_id"`
+	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"`
+	HintBalance            int      `json:"hint_balance"`
+	BlockChat              bool     `json:"block_chat"`
+	BlockFriendRequests    bool     `json:"block_friend_requests"`
+	IsGuest                bool     `json:"is_guest"`
+	NotificationsInAppOnly bool     `json:"notifications_in_app_only"`
+	VariantPreferences     []string `json:"variant_preferences"`
 	// Banner is the advertising-banner block, present only for a viewer eligible to
 	// see the banner. The gateway forwards it verbatim into the Profile payload.
 	Banner *BannerResp `json:"banner,omitempty"`
@@ -184,18 +184,15 @@ type ChatResp struct {
 }
 
 // TelegramAuth provisions/finds the Telegram account and mints a session, seeding a
-// brand-new account's display name and language from the validated launch fields and
-// recording the validating bot's serviceLanguage (which routes the account's later
-// out-of-app push).
-func (c *Client) TelegramAuth(ctx context.Context, externalID, languageCode, username, firstName, serviceLanguage string) (SessionResp, error) {
+// brand-new account's display name and language from the validated launch fields.
+func (c *Client) TelegramAuth(ctx context.Context, externalID, languageCode, username, firstName string) (SessionResp, error) {
 	var out SessionResp
 	err := c.do(ctx, http.MethodPost, "/api/v1/internal/sessions/telegram", "", "",
 		map[string]string{
-			"external_id":      externalID,
-			"language_code":    languageCode,
-			"username":         username,
-			"first_name":       firstName,
-			"service_language": serviceLanguage,
+			"external_id":   externalID,
+			"language_code": languageCode,
+			"username":      username,
+			"first_name":    firstName,
 		}, &out)
 	return out, err
 }

gateway/internal/backendclient/api_social.go

@@ -287,6 +287,7 @@ func (c *Client) UpdateProfile(ctx context.Context, userID string, p ProfileResp
 		"block_chat":                p.BlockChat,
 		"block_friend_requests":     p.BlockFriendRequests,
 		"notifications_in_app_only": p.NotificationsInAppOnly,
+		"variant_preferences":       p.VariantPreferences,
 	}
 	err := c.do(ctx, http.MethodPut, "/api/v1/user/profile", userID, "", body, &out)
 	return out, err

gateway/internal/config/config.go

@@ -6,7 +6,6 @@ import (
 	"fmt"
 	"os"
 	"strconv"
-	"strings"
 	"time"
 
 	pkgtel "scrabble/pkg/telemetry"
@@ -33,11 +32,6 @@ type Config struct {
 	// gateway calls it to validate Mini App initData and to deliver out-of-app push.
 	// Empty disables the telegram auth path and the out-of-app push channel.
 	ConnectorAddr string
-	// DefaultSupportedLanguages is the New Game variant gating set put on the Session
-	// for non-platform logins (web / email / guest), which carry no service container
-	// to declare one. The UI offers only variants in this set (en -> English; ru ->
-	// Russian + Эрудит). Defaults to all of them; a deployment may narrow it.
-	DefaultSupportedLanguages []string
 	// SessionTTL bounds how long a resolved session stays cached; SessionCacheMax
 	// caps the number of cached sessions.
 	SessionTTL      time.Duration
@@ -85,13 +79,6 @@ const (
 // yet small enough to stop a cheap memory-amplification upload.
 const DefaultMaxBodyBytes = 1 << 20
 
-// supportedLanguages is the set of game languages a service may declare for the
-// New Game variant gating; defaultSupportedLanguages is the non-platform fallback.
-var (
-	supportedLanguages        = map[string]bool{"en": true, "ru": true}
-	defaultSupportedLanguages = []string{"en", "ru"}
-)
-
 // DefaultRateLimit returns the built-in anti-abuse limits.
 func DefaultRateLimit() RateLimitConfig {
 	return RateLimitConfig{
@@ -141,9 +128,6 @@ func Load() (Config, error) {
 	if c.MaxBodyBytes, err = envInt("GATEWAY_MAX_BODY_BYTES", DefaultMaxBodyBytes); err != nil {
 		return Config{}, err
 	}
-	if c.DefaultSupportedLanguages, err = envLanguages("GATEWAY_DEFAULT_SUPPORTED_LANGUAGES", defaultSupportedLanguages); err != nil {
-		return Config{}, err
-	}
 	if err := c.validate(); err != nil {
 		return Config{}, err
 	}
@@ -190,31 +174,6 @@ func envOr(key, fallback string) string {
 	return fallback
 }
 
-// envLanguages parses a comma-separated language list (e.g. "en,ru") from the
-// environment variable named key, returning fallback when it is unset. Every entry
-// must be a supported language and the result must be non-empty.
-func envLanguages(key string, fallback []string) ([]string, error) {
-	raw := strings.TrimSpace(os.Getenv(key))
-	if raw == "" {
-		return fallback, nil
-	}
-	var out []string
-	for part := range strings.SplitSeq(raw, ",") {
-		lang := strings.ToLower(strings.TrimSpace(part))
-		if lang == "" {
-			continue
-		}
-		if !supportedLanguages[lang] {
-			return nil, fmt.Errorf("config: %s: unsupported language %q", key, lang)
-		}
-		out = append(out, lang)
-	}
-	if len(out) == 0 {
-		return nil, fmt.Errorf("config: %s must list at least one language", key)
-	}
-	return out, nil
-}
-
 // envInt parses the environment variable named key as an int, returning fallback
 // when it is unset and an error when it is set but malformed.
 func envInt(key string, fallback int) (int, error) {

gateway/internal/connector/client.go

@@ -27,18 +27,13 @@ var ErrInvalidInitData = errors.New("connector: invalid telegram init data")
 // rejects the Login Widget data (a gRPC InvalidArgument).
 var ErrInvalidLoginWidget = errors.New("connector: invalid telegram login widget data")
 
-// User is a validated Mini App identity. ServiceLanguage is the validating bot's
-// language tag (en/ru), persisted to route the user's out-of-app push back through
-// the right bot; SupportedLanguages is that bot's set of offered game languages,
-// which the UI gates the New Game variant choice by. Both are empty for a Login
-// Widget validation (it carries no bot language).
+// User is a validated Mini App identity. LanguageCode seeds a brand-new account's
+// preferred (interface) language; it is empty for a Login Widget validation.
 type User struct {
-	ExternalID         string
-	Username           string
-	FirstName          string
-	LanguageCode       string
-	ServiceLanguage    string
-	SupportedLanguages []string
+	ExternalID   string
+	Username     string
+	FirstName    string
+	LanguageCode string
 }
 
 // Client wraps the connector's Telegram gRPC service.
@@ -73,12 +68,10 @@ func (c *Client) ValidateInitData(ctx context.Context, initData string) (User, e
 		return User{}, err
 	}
 	return User{
-		ExternalID:         resp.GetExternalId(),
-		Username:           resp.GetUsername(),
-		FirstName:          resp.GetFirstName(),
-		LanguageCode:       resp.GetLanguageCode(),
-		ServiceLanguage:    resp.GetServiceLanguage(),
-		SupportedLanguages: resp.GetSupportedLanguages(),
+		ExternalID:   resp.GetExternalId(),
+		Username:     resp.GetUsername(),
+		FirstName:    resp.GetFirstName(),
+		LanguageCode: resp.GetLanguageCode(),
 	}, nil
 }
 

gateway/internal/transcode/encode.go

@@ -13,38 +13,17 @@ import (
 // created before the table that references it, and no two tables/vectors are
 // under construction at once.
 
-// buildSupportedLanguagesVector creates the Session.supported_languages [string]
-// vector from langs. FlatBuffers is built bottom-up, so the caller must invoke this
-// (which itself creates the element strings) before SessionStart and with no table
-// under construction.
-func buildSupportedLanguagesVector(b *flatbuffers.Builder, langs []string) flatbuffers.UOffsetT {
-	offsets := make([]flatbuffers.UOffsetT, len(langs))
-	for i, lang := range langs {
-		offsets[i] = b.CreateString(lang)
-	}
-	fb.SessionStartSupportedLanguagesVector(b, len(langs))
-	for i := len(offsets) - 1; i >= 0; i-- {
-		b.PrependUOffsetT(offsets[i])
-	}
-	return b.EndVector(len(langs))
-}
-
-// encodeSession builds a Session payload. supportedLangs is the service's set of
-// offered game languages, which the UI gates the New Game variant choice by.
-func encodeSession(s backendclient.SessionResp, supportedLangs []string) []byte {
+// encodeSession builds a Session payload.
+func encodeSession(s backendclient.SessionResp) []byte {
 	b := flatbuffers.NewBuilder(128)
 	token := b.CreateString(s.Token)
 	uid := b.CreateString(s.UserID)
 	name := b.CreateString(s.DisplayName)
-	svcLang := b.CreateString(s.ServiceLanguage)
-	langs := buildSupportedLanguagesVector(b, supportedLangs)
 	fb.SessionStart(b)
 	fb.SessionAddToken(b, token)
 	fb.SessionAddUserId(b, uid)
 	fb.SessionAddIsGuest(b, s.IsGuest)
 	fb.SessionAddDisplayName(b, name)
-	fb.SessionAddSupportedLanguages(b, langs)
-	fb.SessionAddServiceLanguage(b, svcLang)
 	b.Finish(fb.SessionEnd(b))
 	return b.FinishedBytes()
 }
@@ -74,6 +53,7 @@ func encodeProfile(p backendclient.ProfileResp) []byte {
 	if p.Banner != nil {
 		banner = encodeBanner(b, *p.Banner)
 	}
+	prefs := buildStringVector(b, p.VariantPreferences, fb.ProfileStartVariantPreferencesVector)
 	fb.ProfileStart(b)
 	fb.ProfileAddUserId(b, uid)
 	fb.ProfileAddDisplayName(b, name)
@@ -86,6 +66,7 @@ func encodeProfile(p backendclient.ProfileResp) []byte {
 	fb.ProfileAddAwayStart(b, awayStart)
 	fb.ProfileAddAwayEnd(b, awayEnd)
 	fb.ProfileAddNotificationsInAppOnly(b, p.NotificationsInAppOnly)
+	fb.ProfileAddVariantPreferences(b, prefs)
 	if p.Banner != nil {
 		fb.ProfileAddBanner(b, banner)
 	}
@@ -147,10 +128,8 @@ func encodeBlockStatus(s backendclient.BlockStatusResp) []byte {
 
 // encodeLinkResult builds a LinkResult payload. A switched-session token
 // (a guest initiator whose durable counterpart won) is carried as a nested Session
-// for the client to adopt; it is omitted otherwise. supportedLangs is the variant
-// gating set for that switched session — the link flows run on the web, so it is the
-// gateway's default (non-platform) set.
-func encodeLinkResult(r backendclient.LinkResultResp, supportedLangs []string) []byte {
+// for the client to adopt; it is omitted otherwise.
+func encodeLinkResult(r backendclient.LinkResultResp) []byte {
 	b := flatbuffers.NewBuilder(256)
 	status := b.CreateString(r.Status)
 	secID := b.CreateString(r.SecondaryUserID)
@@ -161,13 +140,11 @@ func encodeLinkResult(r backendclient.LinkResultResp, supportedLangs []string) [
 		token := b.CreateString(r.Token)
 		uid := b.CreateString(r.Profile.UserID)
 		name := b.CreateString(r.Profile.DisplayName)
-		langs := buildSupportedLanguagesVector(b, supportedLangs)
 		fb.SessionStart(b)
 		fb.SessionAddToken(b, token)
 		fb.SessionAddUserId(b, uid)
 		fb.SessionAddIsGuest(b, r.Profile.IsGuest)
 		fb.SessionAddDisplayName(b, name)
-		fb.SessionAddSupportedLanguages(b, langs)
 		sess = fb.SessionEnd(b)
 	}
 	fb.LinkResultStart(b)

gateway/internal/transcode/transcode.go

@@ -89,20 +89,14 @@ type TelegramValidator interface {
 // NewRegistry builds the slice's message-type catalog over the backend client.
 // The Telegram auth op is registered only when a validator is supplied (the
 // connector is configured); otherwise auth.telegram is simply unknown.
-// defaultLanguages is the New Game variant gating set placed on the Session for
-// non-platform logins (web / email / guest) and on a switched link session; an
-// empty argument falls back to all languages (matching the config default).
-func NewRegistry(backend *backendclient.Client, tg TelegramValidator, defaultLanguages ...string) *Registry {
-	if len(defaultLanguages) == 0 {
-		defaultLanguages = []string{"en", "ru"}
-	}
+func NewRegistry(backend *backendclient.Client, tg TelegramValidator) *Registry {
 	r := &Registry{ops: make(map[string]Op)}
 	if tg != nil {
 		r.ops[MsgAuthTelegram] = Op{Handler: authTelegramHandler(backend, tg)}
 	}
-	r.ops[MsgAuthGuest] = Op{Handler: authGuestHandler(backend, defaultLanguages)}
+	r.ops[MsgAuthGuest] = Op{Handler: authGuestHandler(backend)}
 	r.ops[MsgAuthEmailReq] = Op{Handler: authEmailRequestHandler(backend), Email: true}
-	r.ops[MsgAuthEmailLogin] = Op{Handler: authEmailLoginHandler(backend, defaultLanguages), Email: true}
+	r.ops[MsgAuthEmailLogin] = Op{Handler: authEmailLoginHandler(backend), Email: true}
 	r.ops[MsgProfileGet] = Op{Handler: profileHandler(backend), Auth: true}
 	r.ops[MsgBlockStatus] = Op{Handler: blockStatusHandler(backend), Auth: true}
 	r.ops[MsgGameSubmitPlay] = Op{Handler: submitPlayHandler(backend), Auth: true}
@@ -130,7 +124,7 @@ func NewRegistry(backend *backendclient.Client, tg TelegramValidator, defaultLan
 	r.ops[MsgFeedbackGet] = Op{Handler: feedbackGetHandler(backend), Auth: true}
 	r.ops[MsgFeedbackUnread] = Op{Handler: feedbackUnreadHandler(backend), Auth: true}
 	registerSocialOps(r, backend)
-	registerLinkOps(r, backend, tg, defaultLanguages)
+	registerLinkOps(r, backend, tg)
 	return r
 }
 
@@ -164,21 +158,21 @@ func authTelegramHandler(backend *backendclient.Client, tg TelegramValidator) Ha
 		if err != nil {
 			return nil, err
 		}
-		sess, err := backend.TelegramAuth(ctx, user.ExternalID, user.LanguageCode, user.Username, user.FirstName, user.ServiceLanguage)
+		sess, err := backend.TelegramAuth(ctx, user.ExternalID, user.LanguageCode, user.Username, user.FirstName)
 		if err != nil {
 			return nil, err
 		}
-		return encodeSession(sess, user.SupportedLanguages), nil
+		return encodeSession(sess), nil
 	}
 }
 
-func authGuestHandler(backend *backendclient.Client, supportedLangs []string) Handler {
+func authGuestHandler(backend *backendclient.Client) Handler {
 	return func(ctx context.Context, _ Request) ([]byte, error) {
 		sess, err := backend.GuestAuth(ctx)
 		if err != nil {
 			return nil, err
 		}
-		return encodeSession(sess, supportedLangs), nil
+		return encodeSession(sess), nil
 	}
 }
 
@@ -192,14 +186,14 @@ func authEmailRequestHandler(backend *backendclient.Client) Handler {
 	}
 }
 
-func authEmailLoginHandler(backend *backendclient.Client, supportedLangs []string) Handler {
+func authEmailLoginHandler(backend *backendclient.Client) Handler {
 	return func(ctx context.Context, req Request) ([]byte, error) {
 		in := fb.GetRootAsEmailLoginRequest(req.Payload, 0)
 		sess, err := backend.EmailLogin(ctx, string(in.Email()), string(in.Code()))
 		if err != nil {
 			return nil, err
 		}
-		return encodeSession(sess, supportedLangs), nil
+		return encodeSession(sess), nil
 	}
 }
 

gateway/internal/transcode/transcode_link.go

@@ -22,15 +22,13 @@ const (
 
 // registerLinkOps adds the linking & merge operations. The telegram ops need the
 // connector's Login Widget validator, so they are registered only when tg is set.
-// supportedLangs is the variant gating set for a switched link session (the link
-// flows run on the web, so the gateway default set).
-func registerLinkOps(r *Registry, backend *backendclient.Client, tg TelegramValidator, supportedLangs []string) {
+func registerLinkOps(r *Registry, backend *backendclient.Client, tg TelegramValidator) {
 	r.ops[MsgLinkEmailRequest] = Op{Handler: linkEmailRequestHandler(backend), Auth: true, Email: true}
-	r.ops[MsgLinkEmailConfirm] = Op{Handler: linkEmailConfirmHandler(backend, supportedLangs), Auth: true, Email: true}
-	r.ops[MsgLinkEmailMerge] = Op{Handler: linkEmailMergeHandler(backend, supportedLangs), Auth: true, Email: true}
+	r.ops[MsgLinkEmailConfirm] = Op{Handler: linkEmailConfirmHandler(backend), Auth: true, Email: true}
+	r.ops[MsgLinkEmailMerge] = Op{Handler: linkEmailMergeHandler(backend), Auth: true, Email: true}
 	if tg != nil {
-		r.ops[MsgLinkTelegram] = Op{Handler: linkTelegramHandler(backend, tg, false, supportedLangs), Auth: true}
-		r.ops[MsgLinkTelegramMerge] = Op{Handler: linkTelegramHandler(backend, tg, true, supportedLangs), Auth: true}
+		r.ops[MsgLinkTelegram] = Op{Handler: linkTelegramHandler(backend, tg, false), Auth: true}
+		r.ops[MsgLinkTelegramMerge] = Op{Handler: linkTelegramHandler(backend, tg, true), Auth: true}
 	}
 }
 
@@ -44,31 +42,31 @@ func linkEmailRequestHandler(backend *backendclient.Client) Handler {
 	}
 }
 
-func linkEmailConfirmHandler(backend *backendclient.Client, supportedLangs []string) Handler {
+func linkEmailConfirmHandler(backend *backendclient.Client) Handler {
 	return func(ctx context.Context, req Request) ([]byte, error) {
 		in := fb.GetRootAsLinkEmailConfirm(req.Payload, 0)
 		res, err := backend.LinkEmailConfirm(ctx, req.UserID, string(in.Email()), string(in.Code()))
 		if err != nil {
 			return nil, err
 		}
-		return encodeLinkResult(res, supportedLangs), nil
+		return encodeLinkResult(res), nil
 	}
 }
 
-func linkEmailMergeHandler(backend *backendclient.Client, supportedLangs []string) Handler {
+func linkEmailMergeHandler(backend *backendclient.Client) Handler {
 	return func(ctx context.Context, req Request) ([]byte, error) {
 		in := fb.GetRootAsLinkEmailConfirm(req.Payload, 0)
 		res, err := backend.LinkEmailMerge(ctx, req.UserID, string(in.Email()), string(in.Code()))
 		if err != nil {
 			return nil, err
 		}
-		return encodeLinkResult(res, supportedLangs), nil
+		return encodeLinkResult(res), nil
 	}
 }
 
 // linkTelegramHandler validates Login Widget data via the connector and then calls
 // the backend's link or merge endpoint with the trusted Telegram external id.
-func linkTelegramHandler(backend *backendclient.Client, tg TelegramValidator, merge bool, supportedLangs []string) Handler {
+func linkTelegramHandler(backend *backendclient.Client, tg TelegramValidator, merge bool) Handler {
 	return func(ctx context.Context, req Request) ([]byte, error) {
 		in := fb.GetRootAsLinkTelegramRequest(req.Payload, 0)
 		user, err := tg.ValidateLoginWidget(ctx, string(in.Data()))
@@ -84,6 +82,6 @@ func linkTelegramHandler(backend *backendclient.Client, tg TelegramValidator, me
 		if err != nil {
 			return nil, err
 		}
-		return encodeLinkResult(res, supportedLangs), nil
+		return encodeLinkResult(res), nil
 	}
 }

gateway/internal/transcode/transcode_social.go

@@ -246,6 +246,10 @@ func invitationCancelHandler(backend *backendclient.Client) Handler {
 func profileUpdateHandler(backend *backendclient.Client) Handler {
 	return func(ctx context.Context, req Request) ([]byte, error) {
 		in := fb.GetRootAsUpdateProfileRequest(req.Payload, 0)
+		prefs := make([]string, in.VariantPreferencesLength())
+		for i := range prefs {
+			prefs[i] = string(in.VariantPreferences(i))
+		}
 		p := backendclient.ProfileResp{
 			DisplayName:            string(in.DisplayName()),
 			PreferredLanguage:      string(in.PreferredLanguage()),
@@ -255,6 +259,7 @@ func profileUpdateHandler(backend *backendclient.Client) Handler {
 			BlockChat:              in.BlockChat(),
 			BlockFriendRequests:    in.BlockFriendRequests(),
 			NotificationsInAppOnly: in.NotificationsInAppOnly(),
+			VariantPreferences:     prefs,
 		}
 		out, err := backend.UpdateProfile(ctx, req.UserID, p)
 		if err != nil {

gateway/internal/transcode/transcode_telegram_test.go

@@ -43,11 +43,11 @@ func TestTelegramAuthForwardsSeedFields(t *testing.T) {
 			t.Errorf("unexpected path %q", r.URL.Path)
 		}
 		_ = json.NewDecoder(r.Body).Decode(&gotBody)
-		_, _ = w.Write([]byte(`{"token":"tok-tg","user_id":"u-tg","is_guest":false,"display_name":"Иван","service_language":"ru"}`))
+		_, _ = w.Write([]byte(`{"token":"tok-tg","user_id":"u-tg","is_guest":false,"display_name":"Иван"}`))
 	})
 	defer cleanup()
 
-	v := fakeValidator{user: connector.User{ExternalID: "42", Username: "neo", FirstName: "Иван", LanguageCode: "ru", ServiceLanguage: "ru", SupportedLanguages: []string{"ru"}}}
+	v := fakeValidator{user: connector.User{ExternalID: "42", Username: "neo", FirstName: "Иван", LanguageCode: "ru"}}
 	reg := transcode.NewRegistry(backend, v)
 	op, ok := reg.Lookup(transcode.MsgAuthTelegram)
 	if !ok {
@@ -62,48 +62,9 @@ func TestTelegramAuthForwardsSeedFields(t *testing.T) {
 	if string(sess.Token()) != "tok-tg" || string(sess.UserId()) != "u-tg" {
 		t.Fatalf("session decoded wrong: token=%q user=%q", sess.Token(), sess.UserId())
 	}
-	// The validating bot's supported languages ride the Session so the UI gates the
-	// New Game variant choice (here: ru -> Russian + Эрудит only).
-	if got := sessionLanguages(sess); len(got) != 1 || got[0] != "ru" {
-		t.Errorf("session supported_languages = %v, want [ru]", got)
-	}
-	// The bot's service language rides the Session so the UI can build a share link to
-	// the same bot.
-	if got := string(sess.ServiceLanguage()); got != "ru" {
-		t.Errorf("session service_language = %q, want ru", got)
-	}
-	// The validated launch fields are forwarded so the backend can seed a new account;
-	// service_language is recorded to route the account's later out-of-app push.
-	if gotBody["external_id"] != "42" || gotBody["language_code"] != "ru" || gotBody["first_name"] != "Иван" || gotBody["service_language"] != "ru" {
-		t.Errorf("forwarded body = %+v, want external_id=42 language_code=ru first_name=Иван service_language=ru", gotBody)
-	}
-}
-
-// sessionLanguages reads the supported_languages vector off a decoded Session.
-func sessionLanguages(s *fb.Session) []string {
-	out := make([]string, s.SupportedLanguagesLength())
-	for i := range out {
-		out[i] = string(s.SupportedLanguages(i))
-	}
-	return out
-}
-
-// TestGuestAuthSeedsDefaultLanguages confirms a non-platform (guest) session carries
-// the gateway's default supported-languages set, so the web client is ungated.
-func TestGuestAuthSeedsDefaultLanguages(t *testing.T) {
-	backend, cleanup := fakeBackend(t, func(w http.ResponseWriter, _ *http.Request) {
-		_, _ = w.Write([]byte(`{"token":"tok-g","user_id":"u-g","is_guest":true,"display_name":"Guest"}`))
-	})
-	defer cleanup()
-
-	reg := transcode.NewRegistry(backend, nil, "en", "ru")
-	op, _ := reg.Lookup(transcode.MsgAuthGuest)
-	payload, err := op.Handler(context.Background(), transcode.Request{})
-	if err != nil {
-		t.Fatalf("handler: %v", err)
-	}
-	if got := sessionLanguages(fb.GetRootAsSession(payload, 0)); len(got) != 2 || got[0] != "en" || got[1] != "ru" {
-		t.Errorf("guest session supported_languages = %v, want [en ru]", got)
+	// The validated launch fields are forwarded so the backend can seed a new account.
+	if gotBody["external_id"] != "42" || gotBody["language_code"] != "ru" || gotBody["first_name"] != "Иван" {
+		t.Errorf("forwarded body = %+v, want external_id=42 language_code=ru first_name=Иван", gotBody)
 	}
 }