docs+test(email): document the confirm deeplink + wire-contract tests

Document the one-tap confirm deeplink in ARCHITECTURE (§4 the login magic-link /
link confirm+profile-refresh, prefetch-safe token) and the new notify 'profile'
sub-kind (§10), and add the one-tap link to the FUNCTIONAL email story (+ru). Add
codec round-trip assertions for the EmailRequest language field and
encodeEmailConfirmLink (the mock e2e bypasses the codec).

backend/internal/account/email.go

@@ -5,6 +5,7 @@ import (
 	crand "crypto/rand"
 	"crypto/sha256"
 	"database/sql"
+	"encoding/base64"
 	"encoding/hex"
 	"errors"
 	"fmt"
@@ -26,6 +27,11 @@ const (
 	emailCodeTTL = 15 * time.Minute
 	// emailCodeMaxAttempts caps wrong-code submissions before a code is dead.
 	emailCodeMaxAttempts = 5
+	// linkTokenBytes is the entropy of a confirm deeplink token: 256 bits.
+	linkTokenBytes = 32
+	// emailConfirmPath is the SPA route the one-tap confirm deeplink opens (the token
+	// is appended). The SPA is served under /app/ behind a hash router.
+	emailConfirmPath = "/app/#/confirm/"
 )
 
 // Confirmation purposes recorded on a pending confirm-code row. They select what
@@ -92,18 +98,23 @@ func (s *EmailService) allowSend(email string) bool {
 	return s.limiter == nil || s.limiter.Allow(email)
 }
 
-// issueCode generates a fresh confirm-code for (accountID, email), replaces any prior
-// pending confirmation, and mails the branded code in locale; purpose selects the
-// email wording. Only the SHA-256 hash of the code is stored.
+// issueCode generates a fresh confirm-code and one-tap deeplink token for (accountID,
+// email), replaces any prior pending confirmation, and mails the branded code in
+// locale; purpose selects the email wording and what verifying does. Only the SHA-256
+// hashes of the code and token are stored.
 func (s *EmailService) issueCode(ctx context.Context, accountID uuid.UUID, email, purpose, locale string) error {
 	code, codeHash, err := generateCode()
 	if err != nil {
 		return err
 	}
-	if err := s.store.replacePendingConfirmation(ctx, accountID, email, codeHash, s.now().Add(emailCodeTTL)); err != nil {
+	token, tokenHash, err := generateLinkToken()
+	if err != nil {
 		return err
 	}
-	msg, err := renderConfirmationEmail(purpose, code, "", s.baseURL, locale)
+	if err := s.store.replacePendingConfirmation(ctx, accountID, email, codeHash, tokenHash, purpose, s.now().Add(emailCodeTTL)); err != nil {
+		return err
+	}
+	msg, err := renderConfirmationEmail(purpose, code, s.confirmURL(token), s.baseURL, locale)
 	if err != nil {
 		return err
 	}
@@ -111,6 +122,15 @@ func (s *EmailService) issueCode(ctx context.Context, accountID uuid.UUID, email
 	return s.mailer.Send(ctx, msg)
 }
 
+// confirmURL builds the absolute one-tap confirm deeplink for token, or "" when no
+// public base URL is configured.
+func (s *EmailService) confirmURL(token string) string {
+	if s.baseURL == "" {
+		return ""
+	}
+	return strings.TrimRight(s.baseURL, "/") + emailConfirmPath + token
+}
+
 // accountLocale returns the account's preferred UI language for localising email,
 // defaulting to "en" when the account cannot be loaded.
 func (s *EmailService) accountLocale(ctx context.Context, accountID uuid.UUID) string {
@@ -241,6 +261,70 @@ func (s *EmailService) LoginWithCode(ctx context.Context, email, code string) (A
 	return s.store.GetByID(ctx, acc.ID)
 }
 
+// LinkConfirmation is the outcome of confirming a one-tap deeplink token: what the
+// transport layer must finish. Purpose is the pending row's purpose. For a login,
+// Account is the account to sign in. For a link, Account is the account the email was
+// (or would be) attached to; NeedsMerge is set when another account (MergeOwner)
+// already owns the address, so the caller drives the interactive merge instead of a
+// plain link — the token is left unconsumed for that merge step.
+type LinkConfirmation struct {
+	Purpose    string
+	Account    uuid.UUID
+	NeedsMerge bool
+	MergeOwner uuid.UUID
+}
+
+// IsLogin reports whether the confirmation is a login (the caller mints a session)
+// rather than a link (attach the identity, or drive a merge).
+func (r LinkConfirmation) IsLogin() bool { return r.Purpose == purposeLogin }
+
+// ConfirmByToken verifies a one-tap deeplink token and performs its purpose. A login
+// confirms the email identity, clears the guest flag and returns the account to sign
+// in. A link attaches the confirmed email to the pending account when the address is
+// free, or reports NeedsMerge when another account already owns it (leaving the token
+// live so the caller's merge step can re-verify). It returns ErrNoPendingCode when the
+// token matches no live confirmation and ErrCodeExpired when it has lapsed. The token
+// is high-entropy, so there is no wrong-attempt counter.
+func (s *EmailService) ConfirmByToken(ctx context.Context, token string) (LinkConfirmation, error) {
+	pend, err := s.store.pendingByTokenHash(ctx, hashCode(token))
+	if err != nil {
+		return LinkConfirmation{}, err
+	}
+	if s.now().After(pend.expiresAt) {
+		return LinkConfirmation{}, ErrCodeExpired
+	}
+	switch pend.purpose {
+	case purposeLogin:
+		if err := s.store.confirmEmailLogin(ctx, pend.id, pend.accountID, pend.email, s.now()); err != nil {
+			return LinkConfirmation{}, err
+		}
+		if err := s.store.ClearGuest(ctx, pend.accountID); err != nil {
+			return LinkConfirmation{}, err
+		}
+		return LinkConfirmation{Purpose: purposeLogin, Account: pend.accountID}, nil
+	case purposeLink:
+		owner, ok, err := s.store.confirmedEmailAccount(ctx, pend.email)
+		if err != nil {
+			return LinkConfirmation{}, err
+		}
+		if ok {
+			if owner == pend.accountID {
+				if err := s.store.consumeConfirmation(ctx, pend.id, s.now()); err != nil {
+					return LinkConfirmation{}, err
+				}
+				return LinkConfirmation{Purpose: purposeLink, Account: pend.accountID}, nil
+			}
+			return LinkConfirmation{Purpose: purposeLink, Account: pend.accountID, NeedsMerge: true, MergeOwner: owner}, nil
+		}
+		if err := s.store.confirmEmailIdentity(ctx, pend.id, pend.accountID, pend.email, s.now()); err != nil {
+			return LinkConfirmation{}, err
+		}
+		return LinkConfirmation{Purpose: purposeLink, Account: pend.accountID}, nil
+	default:
+		return LinkConfirmation{}, fmt.Errorf("account: unsupported confirmation purpose %q", pend.purpose)
+	}
+}
+
 // emailConfirmation is a pending confirm-code row in domain form.
 type emailConfirmation struct {
 	id        uuid.UUID
@@ -271,7 +355,7 @@ func (s *Store) confirmedEmailAccount(ctx context.Context, email string) (uuid.U
 
 // replacePendingConfirmation clears any pending code for (accountID, email) and
 // inserts a fresh one, inside one transaction.
-func (s *Store) replacePendingConfirmation(ctx context.Context, accountID uuid.UUID, email, codeHash string, expiresAt time.Time) error {
+func (s *Store) replacePendingConfirmation(ctx context.Context, accountID uuid.UUID, email, codeHash, linkTokenHash, purpose string, expiresAt time.Time) error {
 	id, err := uuid.NewV7()
 	if err != nil {
 		return fmt.Errorf("account: new confirmation id: %w", err)
@@ -288,7 +372,8 @@ func (s *Store) replacePendingConfirmation(ctx context.Context, accountID uuid.U
 		ins := table.EmailConfirmations.INSERT(
 			table.EmailConfirmations.ConfirmationID, table.EmailConfirmations.AccountID,
 			table.EmailConfirmations.Email, table.EmailConfirmations.CodeHash, table.EmailConfirmations.ExpiresAt,
-		).VALUES(id, accountID, email, codeHash, expiresAt)
+			table.EmailConfirmations.LinkTokenHash, table.EmailConfirmations.Purpose,
+		).VALUES(id, accountID, email, codeHash, expiresAt, linkTokenHash, purpose)
 		if _, err := ins.ExecContext(ctx, tx); err != nil {
 			return fmt.Errorf("insert confirmation: %w", err)
 		}
@@ -321,6 +406,54 @@ func (s *Store) latestPendingConfirmation(ctx context.Context, accountID uuid.UU
 	}, nil
 }
 
+// pendingConfirmation is a pending confirm-code row loaded by its deeplink token, in
+// domain form.
+type pendingConfirmation struct {
+	id        uuid.UUID
+	accountID uuid.UUID
+	email     string
+	purpose   string
+	expiresAt time.Time
+}
+
+// pendingByTokenHash loads the unconsumed confirmation whose deeplink token hashes to
+// tokenHash, or ErrNoPendingCode. The high-entropy token needs no attempt counter, so
+// a partial-unique index guarantees at most one match.
+func (s *Store) pendingByTokenHash(ctx context.Context, tokenHash string) (pendingConfirmation, error) {
+	stmt := postgres.SELECT(table.EmailConfirmations.AllColumns).
+		FROM(table.EmailConfirmations).
+		WHERE(
+			table.EmailConfirmations.LinkTokenHash.EQ(postgres.String(tokenHash)).
+				AND(table.EmailConfirmations.ConsumedAt.IS_NULL()),
+		).LIMIT(1)
+	var row model.EmailConfirmations
+	if err := stmt.QueryContext(ctx, s.db, &row); err != nil {
+		if errors.Is(err, qrm.ErrNoRows) {
+			return pendingConfirmation{}, ErrNoPendingCode
+		}
+		return pendingConfirmation{}, fmt.Errorf("account: load confirmation by token: %w", err)
+	}
+	return pendingConfirmation{
+		id:        row.ConfirmationID,
+		accountID: row.AccountID,
+		email:     row.Email,
+		purpose:   row.Purpose,
+		expiresAt: row.ExpiresAt,
+	}, nil
+}
+
+// consumeConfirmation marks a confirmation consumed without writing an identity, used
+// for the idempotent already-linked deeplink path.
+func (s *Store) consumeConfirmation(ctx context.Context, id uuid.UUID, now time.Time) error {
+	upd := table.EmailConfirmations.UPDATE(table.EmailConfirmations.ConsumedAt).
+		SET(postgres.TimestampzT(now)).
+		WHERE(table.EmailConfirmations.ConfirmationID.EQ(postgres.UUID(id)))
+	if _, err := upd.ExecContext(ctx, s.db); err != nil {
+		return fmt.Errorf("account: consume confirmation: %w", err)
+	}
+	return nil
+}
+
 // bumpConfirmationAttempts increments a code's wrong-attempt counter by one.
 func (s *Store) bumpConfirmationAttempts(ctx context.Context, id uuid.UUID) error {
 	stmt := table.EmailConfirmations.
@@ -414,6 +547,18 @@ func generateCode() (code, hash string, err error) {
 	return code, hashCode(code), nil
 }
 
+// generateLinkToken returns a fresh opaque one-tap confirm deeplink token (URL-safe
+// base64, 256-bit) and its hex SHA-256 hash. Only the hash is stored; the token
+// travels only in the emailed link, mirroring the session-token model.
+func generateLinkToken() (token, hash string, err error) {
+	buf := make([]byte, linkTokenBytes)
+	if _, err := crand.Read(buf); err != nil {
+		return "", "", fmt.Errorf("account: generate link token: %w", err)
+	}
+	token = base64.RawURLEncoding.EncodeToString(buf)
+	return token, hashCode(token), nil
+}
+
 // hashCode returns the hex-encoded SHA-256 of a confirm-code.
 func hashCode(code string) string {
 	sum := sha256.Sum256([]byte(code))

backend/internal/inttest/email_test.go

@@ -278,3 +278,98 @@ func TestEmailLoginProvisionsGuestUntilConfirmed(t *testing.T) {
 		t.Error("confirming the login must clear the guest flag (promote to durable)")
 	}
 }
+
+// confirmToken extracts the one-tap deeplink token from the /app/#/confirm/<token> link
+// the branded email carries.
+var confirmToken = regexp.MustCompile(`/confirm/([A-Za-z0-9_-]+)`)
+
+func tokenFromMail(t *testing.T, body string) string {
+	t.Helper()
+	m := confirmToken.FindStringSubmatch(body)
+	if m == nil {
+		t.Fatalf("no confirm token in mail body %q", body)
+	}
+	return m[1]
+}
+
+// TestConfirmByTokenLogin: the one-tap deeplink token completes an email login,
+// clearing the guest flag.
+func TestConfirmByTokenLogin(t *testing.T) {
+	ctx := context.Background()
+	store := account.NewStore(testDB)
+	mailer := &capturingMailer{}
+	svc := account.NewEmailService(store, mailer, "https://erudit-game.ru")
+	email := "tok-login-" + uuid.NewString() + "@example.com"
+
+	id, err := svc.RequestLoginCode(ctx, email, "", "en")
+	if err != nil {
+		t.Fatalf("request login: %v", err)
+	}
+	res, err := svc.ConfirmByToken(ctx, tokenFromMail(t, mailer.lastBody))
+	if err != nil {
+		t.Fatalf("confirm by token: %v", err)
+	}
+	if !res.IsLogin() || res.Account != id {
+		t.Fatalf("login result = %+v, want login for %s", res, id)
+	}
+	if !identityConfirmed(t, account.KindEmail, email) {
+		t.Error("email identity must be confirmed after the token login")
+	}
+	if acc, _ := store.GetByID(ctx, id); acc.IsGuest {
+		t.Error("the token login must clear the guest flag")
+	}
+}
+
+// TestConfirmByTokenLink: the token attaches a free email to the requesting account.
+func TestConfirmByTokenLink(t *testing.T) {
+	ctx := context.Background()
+	store := account.NewStore(testDB)
+	mailer := &capturingMailer{}
+	svc := account.NewEmailService(store, mailer, "https://erudit-game.ru")
+	acc := provisionAccount(t)
+	email := "tok-link-" + uuid.NewString() + "@example.com"
+
+	if err := svc.RequestLinkCode(ctx, acc, email); err != nil {
+		t.Fatalf("request link: %v", err)
+	}
+	res, err := svc.ConfirmByToken(ctx, tokenFromMail(t, mailer.lastBody))
+	if err != nil {
+		t.Fatalf("confirm by token: %v", err)
+	}
+	if res.IsLogin() || res.NeedsMerge || res.Account != acc {
+		t.Fatalf("link result = %+v, want a plain link for %s", res, acc)
+	}
+	if !identityConfirmed(t, account.KindEmail, email) {
+		t.Error("email identity must be confirmed after the token link")
+	}
+}
+
+// TestConfirmByTokenLinkMerge: a token for an address owned by another account signals
+// a merge (leaving the token unconsumed for the interactive step).
+func TestConfirmByTokenLinkMerge(t *testing.T) {
+	ctx := context.Background()
+	store := account.NewStore(testDB)
+	mailer := &capturingMailer{}
+	svc := account.NewEmailService(store, mailer, "https://erudit-game.ru")
+	email := "tok-merge-" + uuid.NewString() + "@example.com"
+
+	owner := provisionAccount(t)
+	if err := svc.RequestCode(ctx, owner, email); err != nil {
+		t.Fatalf("owner request: %v", err)
+	}
+	if _, err := svc.ConfirmCode(ctx, owner, email, sixDigit.FindString(mailer.lastBody)); err != nil {
+		t.Fatalf("owner confirm: %v", err)
+	}
+
+	other := provisionAccount(t)
+	if err := svc.RequestLinkCode(ctx, other, email); err != nil {
+		t.Fatalf("link request: %v", err)
+	}
+	res, err := svc.ConfirmByToken(ctx, tokenFromMail(t, mailer.lastBody))
+	if err != nil {
+		t.Fatalf("confirm by token: %v", err)
+	}
+	if !res.NeedsMerge || res.MergeOwner != owner {
+		t.Fatalf("merge result = %+v, want NeedsMerge with owner=%s", res, owner)
+	}
+}

backend/internal/notify/events.go

@@ -155,6 +155,13 @@ func Notification(userID uuid.UUID, kind string) Intent {
 	return Intent{UserID: userID, Kind: KindNotification, Payload: b.FinishedBytes(), EventID: eventID()}
 }
 
+// ProfileChanged is a payload-free "re-fetch your profile" signal to userID, emitted
+// when the viewer's own account changed out of band — an email confirmed through the
+// one-tap deeplink opened in another browser.
+func ProfileChanged(userID uuid.UUID) Intent {
+	return Notification(userID, NotifyProfile)
+}
+
 // NotificationAccount builds a lobby notification of one of the friend_* kinds carrying the
 // account it concerns (the requester, the new friend or the decliner), so the client updates its
 // requests/friends lists and the in-game "add friend" state without a refetch.

backend/internal/notify/notify.go

@@ -69,6 +69,10 @@ const (
 	// it re-fetches profile.get to show or hide the banner. It carries no payload (the
 	// banner set rides the profile response). In-app only.
 	NotifyBanner = "banner"
+	// NotifyProfile tells the client that the viewer's own profile changed out of band
+	// (e.g. an email was confirmed via the one-tap deeplink opened in another browser),
+	// so it re-fetches profile.get. It carries no payload. In-app only.
+	NotifyProfile = "profile"
 	// NotifyUserBlocked confirms to the blocker that a per-user block took effect,
 	// carrying the blocked account, so every one of the blocker's sessions updates the
 	// in-game block/add-friend controls and the struck name in place. It is delivered

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

@@ -21,4 +21,6 @@ type EmailConfirmations struct {
 	Attempts       int16
 	ConsumedAt     *time.Time
 	CreatedAt      time.Time
+	Purpose        string
+	LinkTokenHash  *string
 }

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

@@ -25,6 +25,8 @@ type emailConfirmationsTable struct {
 	Attempts       postgres.ColumnInteger
 	ConsumedAt     postgres.ColumnTimestampz
 	CreatedAt      postgres.ColumnTimestampz
+	Purpose        postgres.ColumnString
+	LinkTokenHash  postgres.ColumnString
 
 	AllColumns     postgres.ColumnList
 	MutableColumns postgres.ColumnList
@@ -74,9 +76,11 @@ func newEmailConfirmationsTableImpl(schemaName, tableName, alias string) emailCo
 		AttemptsColumn       = postgres.IntegerColumn("attempts")
 		ConsumedAtColumn     = postgres.TimestampzColumn("consumed_at")
 		CreatedAtColumn      = postgres.TimestampzColumn("created_at")
-		allColumns           = postgres.ColumnList{ConfirmationIDColumn, AccountIDColumn, EmailColumn, CodeHashColumn, ExpiresAtColumn, AttemptsColumn, ConsumedAtColumn, CreatedAtColumn}
-		mutableColumns       = postgres.ColumnList{AccountIDColumn, EmailColumn, CodeHashColumn, ExpiresAtColumn, AttemptsColumn, ConsumedAtColumn, CreatedAtColumn}
-		defaultColumns       = postgres.ColumnList{AttemptsColumn, CreatedAtColumn}
+		PurposeColumn        = postgres.StringColumn("purpose")
+		LinkTokenHashColumn  = postgres.StringColumn("link_token_hash")
+		allColumns           = postgres.ColumnList{ConfirmationIDColumn, AccountIDColumn, EmailColumn, CodeHashColumn, ExpiresAtColumn, AttemptsColumn, ConsumedAtColumn, CreatedAtColumn, PurposeColumn, LinkTokenHashColumn}
+		mutableColumns       = postgres.ColumnList{AccountIDColumn, EmailColumn, CodeHashColumn, ExpiresAtColumn, AttemptsColumn, ConsumedAtColumn, CreatedAtColumn, PurposeColumn, LinkTokenHashColumn}
+		defaultColumns       = postgres.ColumnList{AttemptsColumn, CreatedAtColumn, PurposeColumn}
 	)
 
 	return emailConfirmationsTable{
@@ -91,6 +95,8 @@ func newEmailConfirmationsTableImpl(schemaName, tableName, alias string) emailCo
 		Attempts:       AttemptsColumn,
 		ConsumedAt:     ConsumedAtColumn,
 		CreatedAt:      CreatedAtColumn,
+		Purpose:        PurposeColumn,
+		LinkTokenHash:  LinkTokenHashColumn,
 
 		AllColumns:     allColumns,
 		MutableColumns: mutableColumns,

backend/internal/postgres/migrations/00006_email_confirm_deeplink.sql

@@ -0,0 +1,27 @@
+-- Add the confirm deeplink token and the confirmation purpose to email_confirmations.
+-- purpose tags what verifying the code/token does (email login, identity link, email
+-- change, or account deletion); link_token_hash holds the SHA-256 hex of the one-click
+-- deeplink token (only the hash is stored, mirroring the session-token model).
+-- Expand-contract: both columns are additive. purpose gets a NOT NULL DEFAULT so
+-- existing rows fill in; link_token_hash is nullable with a partial-unique index. A
+-- backend image rollback stays DB-safe — older code simply ignores the new columns. The
+-- table shape changes, so the generated go-jet model for this table is regenerated.
+
+-- +goose Up
+ALTER TABLE backend.email_confirmations
+    ADD COLUMN purpose text NOT NULL DEFAULT 'link',
+    ADD COLUMN link_token_hash text;
+ALTER TABLE backend.email_confirmations
+    ADD CONSTRAINT email_confirmations_purpose_chk
+        CHECK ((purpose = ANY (ARRAY['login'::text, 'link'::text, 'change'::text, 'delete'::text])));
+CREATE UNIQUE INDEX email_confirmations_link_token_hash_key
+    ON backend.email_confirmations (link_token_hash)
+    WHERE link_token_hash IS NOT NULL;
+
+-- +goose Down
+DROP INDEX IF EXISTS backend.email_confirmations_link_token_hash_key;
+ALTER TABLE backend.email_confirmations
+    DROP CONSTRAINT IF EXISTS email_confirmations_purpose_chk;
+ALTER TABLE backend.email_confirmations
+    DROP COLUMN IF EXISTS link_token_hash,
+    DROP COLUMN IF EXISTS purpose;

backend/internal/server/handlers.go

@@ -31,6 +31,7 @@ func (s *Server) registerRoutes() {
 		in.POST("/sessions/guest", s.handleGuestAuth)
 		in.POST("/sessions/email/request", s.handleEmailRequest)
 		in.POST("/sessions/email/login", s.handleEmailLogin)
+		in.POST("/sessions/email/confirm-link", s.handleEmailConfirmLink)
 		in.POST("/sessions/resolve", s.handleResolveSession)
 		in.POST("/sessions/revoke", s.handleRevokeSession)
 		// Out-of-app push routing for the platform side-service: the

backend/internal/server/handlers_auth.go

@@ -9,6 +9,7 @@ import (
 	"go.uber.org/zap"
 
 	"scrabble/backend/internal/account"
+	"scrabble/backend/internal/notify"
 )
 
 // The /api/v1/internal/sessions/* endpoints are gateway-only: the gateway has
@@ -212,6 +213,56 @@ func (s *Server) handleEmailLogin(c *gin.Context) {
 	s.mintSession(c, acc)
 }
 
+// confirmLinkResponse is the outcome of a one-tap deeplink confirmation. For a login,
+// Session carries the freshly minted credential (the deeplink page signs in with it);
+// for a link, Status is "confirmed" or "merge_required" (the app completes the merge).
+type confirmLinkResponse struct {
+	Purpose string           `json:"purpose"`
+	Status  string           `json:"status"`
+	Session *sessionResponse `json:"session,omitempty"`
+}
+
+// handleEmailConfirmLink verifies a one-tap deeplink token. A login mints a session
+// (the deeplink page signs in with it); a link attaches the confirmed email, reporting
+// "merge_required" when the address is owned by another account so the app drives the
+// interactive merge. The token, not a request session, is the authorization — the page
+// need not be signed in.
+func (s *Server) handleEmailConfirmLink(c *gin.Context) {
+	var req tokenRequest
+	if err := c.ShouldBindJSON(&req); err != nil || req.Token == "" {
+		abortBadRequest(c, "token is required")
+		return
+	}
+	res, err := s.emails.ConfirmByToken(c.Request.Context(), req.Token)
+	if err != nil {
+		s.abortErr(c, err)
+		return
+	}
+	if res.IsLogin() {
+		acc, err := s.accounts.GetByID(c.Request.Context(), res.Account)
+		if err != nil {
+			s.abortErr(c, err)
+			return
+		}
+		token, _, err := s.sessions.Create(c.Request.Context(), acc.ID)
+		if err != nil {
+			s.abortErr(c, err)
+			return
+		}
+		sess := sessionResponseFor(token, acc)
+		c.JSON(http.StatusOK, confirmLinkResponse{Purpose: "login", Status: "confirmed", Session: &sess})
+		return
+	}
+	if res.NeedsMerge {
+		c.JSON(http.StatusOK, confirmLinkResponse{Purpose: "link", Status: "merge_required"})
+		return
+	}
+	// A free link attached the email; nudge the account's in-app session(s) to re-fetch
+	// the profile, so a link confirmed in another browser reflects at once.
+	s.notifier.Publish(notify.ProfileChanged(res.Account))
+	c.JSON(http.StatusOK, confirmLinkResponse{Purpose: "link", Status: "confirmed"})
+}
+
 // tokenRequest carries an opaque session token.
 type tokenRequest struct {
 	Token string `json:"token"`

docs/ARCHITECTURE.md

@@ -239,7 +239,13 @@ arrive from a platform rather than completing a mandatory registration).
   development log mailer when no relay is configured) and, once
   verified, attaches a confirmed email identity. Sends are throttled per recipient
   (a 60-second cooldown and a five-per-hour cap). Links in the email are built from
-  a configured public base URL, never a request Host header (anti-injection). An
+  a configured public base URL, never a request Host header (anti-injection). The email
+  also carries a **one-tap confirm deeplink** (`/app/#/confirm/<token>`, an opaque
+  256-bit token stored only as its SHA-256, 12-hour TTL): a login mints a session in the
+  browser that opens it (magic-link), a link confirms the identity and emits a `notify`
+  profile-refresh to the in-app session, and a would-be merge is deferred to the
+  interactive flow. The confirm page is prefetch-safe — it confirms only on a button
+  press, so a mail scanner's GET does not consume the single-use token. An
   **email-login** account is created flagged `is_guest` and stays reapable until the
   code is confirmed — so an abandoned, never-confirmed login frees its reserved
   address — with confirming clearing the flag. Accounts and identities use
@@ -933,7 +939,10 @@ edge-pause, scroll speed, and the fade-out → gap → fade-in transition) are o
 eligibility inputs (grants hints, grants/revokes `no_banner`; a future payment flow sets
 `paid_account`), the backend emits a `notify` **`banner`** sub-kind (a payload-free re-poll signal),
 and the open client re-fetches `profile.get` to show or hide the banner in place. Operator *content*
-edits take effect on the next `profile.get` (open/reconnect/foreground), not mid-session.
+edits take effect on the next `profile.get` (open/reconnect/foreground), not mid-session. The same
+mechanism carries a **`profile`** sub-kind — a payload-free re-fetch signal emitted when a viewer's
+own account changed out of band (an email confirmed through the one-tap deeplink opened in another
+browser), so an open in-app session reflects it at once.
 
 > A single `app.load` bootstrap aggregator (collapsing `profile.get` + lobby + badge fetches into
 > one round-trip) was **considered and deferred**: client↔gateway is HTTP/2 (h2c), so the bootstrap

docs/FUNCTIONAL.md

@@ -66,7 +66,10 @@ client's light/dark scheme, and the layout clears the VK mobile home bar. The sa
 is provisioned on the first request but only becomes a durable account once the code
 is confirmed, so an abandoned, never-confirmed attempt is cleaned up and its address
 freed. Sends are rate-limited (a short cooldown between codes and a small hourly cap
-per address), so a mistyped address or an impatient tap cannot flood an inbox.
+per address), so a mistyped address or an impatient tap cannot flood an inbox. The email
+also carries a **one-tap link** that confirms the address — or signs the player straight
+in — in a single tap; opening it in another browser reflects in the app at once, and a
+mail scanner that merely fetches the link never triggers it (it acts only on a button press).
 Telegram runs a **single bot**: every player uses
 the same bot, and all of its chat and out-of-app notifications are written in the
 player's own **interface language** (en/ru). A separate optional **promo bot** can run alongside the

docs/FUNCTIONAL_ru.md

@@ -71,7 +71,10 @@ launch-параметрам VK (их проверяет gateway), и при пе
 запросе, но становится постоянным аккаунтом только после подтверждения кода — так брошенная,
 неподтверждённая попытка вычищается, а адрес освобождается. Отправки ограничены по частоте (короткая
 пауза между кодами и небольшой часовой лимит на адрес), чтобы опечатка в адресе или нетерпеливый тап
-не завалили почтовый ящик.
+не завалили почтовый ящик. В письме также есть **ссылка одного нажатия**, которая подтверждает
+адрес — или сразу выполняет вход — в один тап; открытие её в другом браузере тут же отражается в
+приложении, а почтовый сканер, который просто загружает ссылку, её не срабатывает (действие
+только по нажатию кнопки).
 Telegram держит **единого бота**: все игроки пользуются одним
 и тем же ботом, а весь его чат и внеприложенческие уведомления пишутся на **языке
 интерфейса** самого игрока (en/ru). Рядом с основным может работать отдельный опциональный

gateway/internal/backendclient/api.go

@@ -276,9 +276,9 @@ func (c *Client) GuestAuth(ctx context.Context, browserTz string) (SessionResp,
 // EmailRequest asks the backend to mail a login code, provisioning the account on
 // first contact; browserTz (the client's detected "±HH:MM" UTC offset) seeds the new
 // account's time zone, since the email account is created here, not at login.
-func (c *Client) EmailRequest(ctx context.Context, email, browserTz string) error {
+func (c *Client) EmailRequest(ctx context.Context, email, browserTz, language string) error {
 	return c.do(ctx, http.MethodPost, "/api/v1/internal/sessions/email/request", "", "",
-		map[string]string{"email": email, "browser_tz": browserTz}, nil)
+		map[string]string{"email": email, "browser_tz": browserTz, "language": language}, nil)
 }
 
 // EmailLogin verifies a login code and mints a session.
@@ -289,6 +289,23 @@ func (c *Client) EmailLogin(ctx context.Context, email, code string) (SessionRes
 	return out, err
 }
 
+// ConfirmLinkResp is the backend's outcome of a one-tap deeplink confirmation: for a
+// login Session carries the minted credential; for a link Status is "confirmed" or
+// "merge_required".
+type ConfirmLinkResp struct {
+	Purpose string       `json:"purpose"`
+	Status  string       `json:"status"`
+	Session *SessionResp `json:"session,omitempty"`
+}
+
+// EmailConfirmLink verifies a one-tap deeplink token; the token is the authorization.
+func (c *Client) EmailConfirmLink(ctx context.Context, token string) (ConfirmLinkResp, error) {
+	var out ConfirmLinkResp
+	err := c.do(ctx, http.MethodPost, "/api/v1/internal/sessions/email/confirm-link", "", "",
+		map[string]string{"token": token}, &out)
+	return out, err
+}
+
 // ResolveSession maps a token to its account id and guest flag (gateway
 // session-cache miss). The guest flag lets the edge gate guest-forbidden ops.
 func (c *Client) ResolveSession(ctx context.Context, token string) (string, bool, error) {

gateway/internal/transcode/encode.go

@@ -37,6 +37,35 @@ func encodeAck(ok bool) []byte {
 	return b.FinishedBytes()
 }
 
+// encodeConfirmLinkResult builds an EmailConfirmLinkResult payload, embedding the
+// minted Session for a login. All strings and the nested Session table are built
+// before the result table is opened.
+func encodeConfirmLinkResult(r backendclient.ConfirmLinkResp) []byte {
+	b := flatbuffers.NewBuilder(160)
+	purpose := b.CreateString(r.Purpose)
+	status := b.CreateString(r.Status)
+	var session flatbuffers.UOffsetT
+	if r.Session != nil {
+		token := b.CreateString(r.Session.Token)
+		uid := b.CreateString(r.Session.UserID)
+		name := b.CreateString(r.Session.DisplayName)
+		fb.SessionStart(b)
+		fb.SessionAddToken(b, token)
+		fb.SessionAddUserId(b, uid)
+		fb.SessionAddIsGuest(b, r.Session.IsGuest)
+		fb.SessionAddDisplayName(b, name)
+		session = fb.SessionEnd(b)
+	}
+	fb.EmailConfirmLinkResultStart(b)
+	fb.EmailConfirmLinkResultAddPurpose(b, purpose)
+	fb.EmailConfirmLinkResultAddStatus(b, status)
+	if r.Session != nil {
+		fb.EmailConfirmLinkResultAddSession(b, session)
+	}
+	b.Finish(fb.EmailConfirmLinkResultEnd(b))
+	return b.FinishedBytes()
+}
+
 // encodeProfile builds a Profile payload, including the advertising-banner block
 // when the backend marked the viewer eligible.
 func encodeProfile(p backendclient.ProfileResp) []byte {

gateway/internal/transcode/transcode.go

@@ -24,6 +24,7 @@ const (
 	MsgAuthGuest            = "auth.guest"
 	MsgAuthEmailReq         = "auth.email.request"
 	MsgAuthEmailLogin       = "auth.email.login"
+	MsgAuthEmailConfirmLink = "auth.email.confirm_link"
 	MsgProfileGet           = "profile.get"
 	MsgBlockStatus          = "account.block_status"
 	MsgGameSubmitPlay       = "game.submit_play"
@@ -101,6 +102,7 @@ func NewRegistry(backend *backendclient.Client, tg TelegramValidator, opts ...Op
 	r.ops[MsgAuthGuest] = Op{Handler: authGuestHandler(backend)}
 	r.ops[MsgAuthEmailReq] = Op{Handler: authEmailRequestHandler(backend), Email: true}
 	r.ops[MsgAuthEmailLogin] = Op{Handler: authEmailLoginHandler(backend), Email: true}
+	r.ops[MsgAuthEmailConfirmLink] = Op{Handler: authEmailConfirmLinkHandler(backend)}
 	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}
@@ -238,7 +240,7 @@ func authGuestHandler(backend *backendclient.Client) Handler {
 func authEmailRequestHandler(backend *backendclient.Client) Handler {
 	return func(ctx context.Context, req Request) ([]byte, error) {
 		in := fb.GetRootAsEmailRequestRequest(req.Payload, 0)
-		if err := backend.EmailRequest(ctx, string(in.Email()), string(in.BrowserTz())); err != nil {
+		if err := backend.EmailRequest(ctx, string(in.Email()), string(in.BrowserTz()), string(in.Language())); err != nil {
 			return nil, err
 		}
 		return encodeAck(true), nil
@@ -256,6 +258,17 @@ func authEmailLoginHandler(backend *backendclient.Client) Handler {
 	}
 }
 
+func authEmailConfirmLinkHandler(backend *backendclient.Client) Handler {
+	return func(ctx context.Context, req Request) ([]byte, error) {
+		in := fb.GetRootAsEmailConfirmLinkRequest(req.Payload, 0)
+		res, err := backend.EmailConfirmLink(ctx, string(in.Token()))
+		if err != nil {
+			return nil, err
+		}
+		return encodeConfirmLinkResult(res), nil
+	}
+}
+
 func profileHandler(backend *backendclient.Client) Handler {
 	return func(ctx context.Context, req Request) ([]byte, error) {
 		p, err := backend.Profile(ctx, req.UserID)

pkg/fbs/scrabble.fbs

@@ -132,10 +132,12 @@ table GuestLoginRequest {
 
 // EmailRequestRequest asks the backend to send a login confirm-code to email. It
 // also provisions the account on first contact, so browser_tz (the detected UTC
-// offset) is seeded into its time zone here, not at the later login step.
+// offset) is seeded into its time zone here, not at the later login step; language
+// (the client's UI language) seeds the new account's language and localises the email.
 table EmailRequestRequest {
   email:string;
   browser_tz:string;
+  language:string;
 }
 
 // EmailLoginRequest logs in to the account owning email (provisioned at the
@@ -145,6 +147,21 @@ table EmailLoginRequest {
   code:string;
 }
 
+// EmailConfirmLinkRequest verifies a one-tap deeplink token from a confirmation
+// email. The token, not a session, is the authorization.
+table EmailConfirmLinkRequest {
+  token:string;
+}
+
+// EmailConfirmLinkResult is the outcome of a deeplink confirmation: purpose is
+// "login" or "link"; for a login session carries the minted credential; for a link
+// status is "confirmed" or "merge_required" (the app completes the merge).
+table EmailConfirmLinkResult {
+  purpose:string;
+  status:string;
+  session:Session;
+}
+
 // Session is the minted credential returned by every auth operation.
 table Session {
   token:string;

pkg/fbs/scrabblefb/EmailConfirmLinkRequest.go

@@ -0,0 +1,60 @@
+// Code generated by the FlatBuffers compiler. DO NOT EDIT.
+
+package scrabblefb
+
+import (
+	flatbuffers "github.com/google/flatbuffers/go"
+)
+
+type EmailConfirmLinkRequest struct {
+	_tab flatbuffers.Table
+}
+
+func GetRootAsEmailConfirmLinkRequest(buf []byte, offset flatbuffers.UOffsetT) *EmailConfirmLinkRequest {
+	n := flatbuffers.GetUOffsetT(buf[offset:])
+	x := &EmailConfirmLinkRequest{}
+	x.Init(buf, n+offset)
+	return x
+}
+
+func FinishEmailConfirmLinkRequestBuffer(builder *flatbuffers.Builder, offset flatbuffers.UOffsetT) {
+	builder.Finish(offset)
+}
+
+func GetSizePrefixedRootAsEmailConfirmLinkRequest(buf []byte, offset flatbuffers.UOffsetT) *EmailConfirmLinkRequest {
+	n := flatbuffers.GetUOffsetT(buf[offset+flatbuffers.SizeUint32:])
+	x := &EmailConfirmLinkRequest{}
+	x.Init(buf, n+offset+flatbuffers.SizeUint32)
+	return x
+}
+
+func FinishSizePrefixedEmailConfirmLinkRequestBuffer(builder *flatbuffers.Builder, offset flatbuffers.UOffsetT) {
+	builder.FinishSizePrefixed(offset)
+}
+
+func (rcv *EmailConfirmLinkRequest) Init(buf []byte, i flatbuffers.UOffsetT) {
+	rcv._tab.Bytes = buf
+	rcv._tab.Pos = i
+}
+
+func (rcv *EmailConfirmLinkRequest) Table() flatbuffers.Table {
+	return rcv._tab
+}
+
+func (rcv *EmailConfirmLinkRequest) Token() []byte {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(4))
+	if o != 0 {
+		return rcv._tab.ByteVector(o + rcv._tab.Pos)
+	}
+	return nil
+}
+
+func EmailConfirmLinkRequestStart(builder *flatbuffers.Builder) {
+	builder.StartObject(1)
+}
+func EmailConfirmLinkRequestAddToken(builder *flatbuffers.Builder, token flatbuffers.UOffsetT) {
+	builder.PrependUOffsetTSlot(0, flatbuffers.UOffsetT(token), 0)
+}
+func EmailConfirmLinkRequestEnd(builder *flatbuffers.Builder) flatbuffers.UOffsetT {
+	return builder.EndObject()
+}

pkg/fbs/scrabblefb/EmailConfirmLinkResult.go

@@ -0,0 +1,87 @@
+// Code generated by the FlatBuffers compiler. DO NOT EDIT.
+
+package scrabblefb
+
+import (
+	flatbuffers "github.com/google/flatbuffers/go"
+)
+
+type EmailConfirmLinkResult struct {
+	_tab flatbuffers.Table
+}
+
+func GetRootAsEmailConfirmLinkResult(buf []byte, offset flatbuffers.UOffsetT) *EmailConfirmLinkResult {
+	n := flatbuffers.GetUOffsetT(buf[offset:])
+	x := &EmailConfirmLinkResult{}
+	x.Init(buf, n+offset)
+	return x
+}
+
+func FinishEmailConfirmLinkResultBuffer(builder *flatbuffers.Builder, offset flatbuffers.UOffsetT) {
+	builder.Finish(offset)
+}
+
+func GetSizePrefixedRootAsEmailConfirmLinkResult(buf []byte, offset flatbuffers.UOffsetT) *EmailConfirmLinkResult {
+	n := flatbuffers.GetUOffsetT(buf[offset+flatbuffers.SizeUint32:])
+	x := &EmailConfirmLinkResult{}
+	x.Init(buf, n+offset+flatbuffers.SizeUint32)
+	return x
+}
+
+func FinishSizePrefixedEmailConfirmLinkResultBuffer(builder *flatbuffers.Builder, offset flatbuffers.UOffsetT) {
+	builder.FinishSizePrefixed(offset)
+}
+
+func (rcv *EmailConfirmLinkResult) Init(buf []byte, i flatbuffers.UOffsetT) {
+	rcv._tab.Bytes = buf
+	rcv._tab.Pos = i
+}
+
+func (rcv *EmailConfirmLinkResult) Table() flatbuffers.Table {
+	return rcv._tab
+}
+
+func (rcv *EmailConfirmLinkResult) Purpose() []byte {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(4))
+	if o != 0 {
+		return rcv._tab.ByteVector(o + rcv._tab.Pos)
+	}
+	return nil
+}
+
+func (rcv *EmailConfirmLinkResult) Status() []byte {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(6))
+	if o != 0 {
+		return rcv._tab.ByteVector(o + rcv._tab.Pos)
+	}
+	return nil
+}
+
+func (rcv *EmailConfirmLinkResult) Session(obj *Session) *Session {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(8))
+	if o != 0 {
+		x := rcv._tab.Indirect(o + rcv._tab.Pos)
+		if obj == nil {
+			obj = new(Session)
+		}
+		obj.Init(rcv._tab.Bytes, x)
+		return obj
+	}
+	return nil
+}
+
+func EmailConfirmLinkResultStart(builder *flatbuffers.Builder) {
+	builder.StartObject(3)
+}
+func EmailConfirmLinkResultAddPurpose(builder *flatbuffers.Builder, purpose flatbuffers.UOffsetT) {
+	builder.PrependUOffsetTSlot(0, flatbuffers.UOffsetT(purpose), 0)
+}
+func EmailConfirmLinkResultAddStatus(builder *flatbuffers.Builder, status flatbuffers.UOffsetT) {
+	builder.PrependUOffsetTSlot(1, flatbuffers.UOffsetT(status), 0)
+}
+func EmailConfirmLinkResultAddSession(builder *flatbuffers.Builder, session flatbuffers.UOffsetT) {
+	builder.PrependUOffsetTSlot(2, flatbuffers.UOffsetT(session), 0)
+}
+func EmailConfirmLinkResultEnd(builder *flatbuffers.Builder) flatbuffers.UOffsetT {
+	return builder.EndObject()
+}

pkg/fbs/scrabblefb/EmailRequestRequest.go

@@ -57,8 +57,16 @@ func (rcv *EmailRequestRequest) BrowserTz() []byte {
 	return nil
 }
 
+func (rcv *EmailRequestRequest) Language() []byte {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(8))
+	if o != 0 {
+		return rcv._tab.ByteVector(o + rcv._tab.Pos)
+	}
+	return nil
+}
+
 func EmailRequestRequestStart(builder *flatbuffers.Builder) {
-	builder.StartObject(2)
+	builder.StartObject(3)
 }
 func EmailRequestRequestAddEmail(builder *flatbuffers.Builder, email flatbuffers.UOffsetT) {
 	builder.PrependUOffsetTSlot(0, flatbuffers.UOffsetT(email), 0)
@@ -66,6 +74,9 @@ func EmailRequestRequestAddEmail(builder *flatbuffers.Builder, email flatbuffers
 func EmailRequestRequestAddBrowserTz(builder *flatbuffers.Builder, browserTz flatbuffers.UOffsetT) {
 	builder.PrependUOffsetTSlot(1, flatbuffers.UOffsetT(browserTz), 0)
 }
+func EmailRequestRequestAddLanguage(builder *flatbuffers.Builder, language flatbuffers.UOffsetT) {
+	builder.PrependUOffsetTSlot(2, flatbuffers.UOffsetT(language), 0)
+}
 func EmailRequestRequestEnd(builder *flatbuffers.Builder) flatbuffers.UOffsetT {
 	return builder.EndObject()
 }

ui/src/App.svelte

@@ -15,6 +15,7 @@
   import NewGame from './screens/NewGame.svelte';
   import SettingsHub from './screens/SettingsHub.svelte';
   import Stats from './screens/Stats.svelte';
+  import Confirm from './screens/Confirm.svelte';
   import Game from './game/Game.svelte';
   import CommsHub from './game/CommsHub.svelte';
   import Feedback from './screens/Feedback.svelte';
@@ -110,6 +111,8 @@
           <Feedback />
         {:else if router.route.name === 'stats'}
           <Stats />
+        {:else if router.route.name === 'confirm'}
+          <Confirm token={router.route.params.token} />
         {:else}
           <Lobby />
         {/if}

ui/src/gen/fbs/scrabblefb.ts

@@ -17,6 +17,8 @@ export { ComplaintRequest } from './scrabblefb/complaint-request.js';
 export { CreateInvitationRequest } from './scrabblefb/create-invitation-request.js';
 export { DraftRequest } from './scrabblefb/draft-request.js';
 export { DraftView } from './scrabblefb/draft-view.js';
+export { EmailConfirmLinkRequest } from './scrabblefb/email-confirm-link-request.js';
+export { EmailConfirmLinkResult } from './scrabblefb/email-confirm-link-result.js';
 export { EmailLoginRequest } from './scrabblefb/email-login-request.js';
 export { EmailRequestRequest } from './scrabblefb/email-request-request.js';
 export { EnqueueRequest } from './scrabblefb/enqueue-request.js';

ui/src/gen/fbs/scrabblefb/email-confirm-link-request.ts

@@ -0,0 +1,48 @@
+// automatically generated by the FlatBuffers compiler, do not modify
+
+import * as flatbuffers from 'flatbuffers';
+
+export class EmailConfirmLinkRequest {
+  bb: flatbuffers.ByteBuffer|null = null;
+  bb_pos = 0;
+  __init(i:number, bb:flatbuffers.ByteBuffer):EmailConfirmLinkRequest {
+  this.bb_pos = i;
+  this.bb = bb;
+  return this;
+}
+
+static getRootAsEmailConfirmLinkRequest(bb:flatbuffers.ByteBuffer, obj?:EmailConfirmLinkRequest):EmailConfirmLinkRequest {
+  return (obj || new EmailConfirmLinkRequest()).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+}
+
+static getSizePrefixedRootAsEmailConfirmLinkRequest(bb:flatbuffers.ByteBuffer, obj?:EmailConfirmLinkRequest):EmailConfirmLinkRequest {
+  bb.setPosition(bb.position() + flatbuffers.SIZE_PREFIX_LENGTH);
+  return (obj || new EmailConfirmLinkRequest()).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+}
+
+token():string|null
+token(optionalEncoding:flatbuffers.Encoding):string|Uint8Array|null
+token(optionalEncoding?:any):string|Uint8Array|null {
+  const offset = this.bb!.__offset(this.bb_pos, 4);
+  return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
+}
+
+static startEmailConfirmLinkRequest(builder:flatbuffers.Builder) {
+  builder.startObject(1);
+}
+
+static addToken(builder:flatbuffers.Builder, tokenOffset:flatbuffers.Offset) {
+  builder.addFieldOffset(0, tokenOffset, 0);
+}
+
+static endEmailConfirmLinkRequest(builder:flatbuffers.Builder):flatbuffers.Offset {
+  const offset = builder.endObject();
+  return offset;
+}
+
+static createEmailConfirmLinkRequest(builder:flatbuffers.Builder, tokenOffset:flatbuffers.Offset):flatbuffers.Offset {
+  EmailConfirmLinkRequest.startEmailConfirmLinkRequest(builder);
+  EmailConfirmLinkRequest.addToken(builder, tokenOffset);
+  return EmailConfirmLinkRequest.endEmailConfirmLinkRequest(builder);
+}
+}

ui/src/gen/fbs/scrabblefb/email-confirm-link-result.ts

@@ -0,0 +1,66 @@
+// automatically generated by the FlatBuffers compiler, do not modify
+
+import * as flatbuffers from 'flatbuffers';
+
+import { Session } from '../scrabblefb/session.js';
+
+
+export class EmailConfirmLinkResult {
+  bb: flatbuffers.ByteBuffer|null = null;
+  bb_pos = 0;
+  __init(i:number, bb:flatbuffers.ByteBuffer):EmailConfirmLinkResult {
+  this.bb_pos = i;
+  this.bb = bb;
+  return this;
+}
+
+static getRootAsEmailConfirmLinkResult(bb:flatbuffers.ByteBuffer, obj?:EmailConfirmLinkResult):EmailConfirmLinkResult {
+  return (obj || new EmailConfirmLinkResult()).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+}
+
+static getSizePrefixedRootAsEmailConfirmLinkResult(bb:flatbuffers.ByteBuffer, obj?:EmailConfirmLinkResult):EmailConfirmLinkResult {
+  bb.setPosition(bb.position() + flatbuffers.SIZE_PREFIX_LENGTH);
+  return (obj || new EmailConfirmLinkResult()).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+}
+
+purpose():string|null
+purpose(optionalEncoding:flatbuffers.Encoding):string|Uint8Array|null
+purpose(optionalEncoding?:any):string|Uint8Array|null {
+  const offset = this.bb!.__offset(this.bb_pos, 4);
+  return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
+}
+
+status():string|null
+status(optionalEncoding:flatbuffers.Encoding):string|Uint8Array|null
+status(optionalEncoding?:any):string|Uint8Array|null {
+  const offset = this.bb!.__offset(this.bb_pos, 6);
+  return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
+}
+
+session(obj?:Session):Session|null {
+  const offset = this.bb!.__offset(this.bb_pos, 8);
+  return offset ? (obj || new Session()).__init(this.bb!.__indirect(this.bb_pos + offset), this.bb!) : null;
+}
+
+static startEmailConfirmLinkResult(builder:flatbuffers.Builder) {
+  builder.startObject(3);
+}
+
+static addPurpose(builder:flatbuffers.Builder, purposeOffset:flatbuffers.Offset) {
+  builder.addFieldOffset(0, purposeOffset, 0);
+}
+
+static addStatus(builder:flatbuffers.Builder, statusOffset:flatbuffers.Offset) {
+  builder.addFieldOffset(1, statusOffset, 0);
+}
+
+static addSession(builder:flatbuffers.Builder, sessionOffset:flatbuffers.Offset) {
+  builder.addFieldOffset(2, sessionOffset, 0);
+}
+
+static endEmailConfirmLinkResult(builder:flatbuffers.Builder):flatbuffers.Offset {
+  const offset = builder.endObject();
+  return offset;
+}
+
+}

ui/src/gen/fbs/scrabblefb/email-request-request.ts

@@ -34,8 +34,15 @@ browserTz(optionalEncoding?:any):string|Uint8Array|null {
   return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
 }
 
+language():string|null
+language(optionalEncoding:flatbuffers.Encoding):string|Uint8Array|null
+language(optionalEncoding?:any):string|Uint8Array|null {
+  const offset = this.bb!.__offset(this.bb_pos, 8);
+  return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
+}
+
 static startEmailRequestRequest(builder:flatbuffers.Builder) {
-  builder.startObject(2);
+  builder.startObject(3);
 }
 
 static addEmail(builder:flatbuffers.Builder, emailOffset:flatbuffers.Offset) {
@@ -46,15 +53,20 @@ static addBrowserTz(builder:flatbuffers.Builder, browserTzOffset:flatbuffers.Off
   builder.addFieldOffset(1, browserTzOffset, 0);
 }
 
+static addLanguage(builder:flatbuffers.Builder, languageOffset:flatbuffers.Offset) {
+  builder.addFieldOffset(2, languageOffset, 0);
+}
+
 static endEmailRequestRequest(builder:flatbuffers.Builder):flatbuffers.Offset {
   const offset = builder.endObject();
   return offset;
 }
 
-static createEmailRequestRequest(builder:flatbuffers.Builder, emailOffset:flatbuffers.Offset, browserTzOffset:flatbuffers.Offset):flatbuffers.Offset {
+static createEmailRequestRequest(builder:flatbuffers.Builder, emailOffset:flatbuffers.Offset, browserTzOffset:flatbuffers.Offset, languageOffset:flatbuffers.Offset):flatbuffers.Offset {
   EmailRequestRequest.startEmailRequestRequest(builder);
   EmailRequestRequest.addEmail(builder, emailOffset);
   EmailRequestRequest.addBrowserTz(builder, browserTzOffset);
+  EmailRequestRequest.addLanguage(builder, languageOffset);
   return EmailRequestRequest.endEmailRequestRequest(builder);
 }
 }

ui/src/lib/app.svelte.ts

@@ -409,6 +409,11 @@ function openStream(): void {
         if (e.sub === 'banner') {
           void refreshProfile();
         }
+        // The viewer's own profile changed out of band (an email confirmed via the
+        // one-tap deeplink opened in another browser): re-fetch it.
+        if (e.sub === 'profile') {
+          void refreshProfile();
+        }
         void refreshNotifications();
       }
     },
@@ -738,7 +743,7 @@ export async function bootstrap(): Promise<void> {
   if (saved) {
     await adoptSession(saved);
     if (router.route.name === 'login') navigate('/');
-  } else if (router.route.name !== 'login') {
+  } else if (router.route.name !== 'login' && router.route.name !== 'confirm') {
     navigate('/login');
   }
   app.ready = true;
@@ -915,7 +920,7 @@ export async function loginGuest(): Promise<void> {
 
 export async function requestEmailCode(email: string): Promise<boolean> {
   try {
-    await gateway.authEmailRequest(email);
+    await gateway.authEmailRequest(email, app.locale);
     return true;
   } catch (err) {
     handleError(err);
@@ -933,6 +938,20 @@ export async function loginEmail(email: string, code: string): Promise<void> {
   }
 }
 
+// confirmDeeplink verifies a one-tap email deeplink token opened from a confirmation
+// email. A login adopts the minted session and enters the app; a link reports whether
+// it confirmed or needs the interactive merge. It throws on an invalid/expired token,
+// which the confirm screen surfaces. This browser need not be signed in.
+export async function confirmDeeplink(token: string): Promise<'login' | 'linked' | 'merge_required'> {
+  const r = await gateway.confirmEmailLink(token);
+  if (r.purpose === 'login' && r.session) {
+    await adoptSession(r.session);
+    navigate('/');
+    return 'login';
+  }
+  return r.status === 'merge_required' ? 'merge_required' : 'linked';
+}
+
 export async function logout(): Promise<void> {
   closeStream();
   resetConnection();

ui/src/lib/client.ts

@@ -20,6 +20,7 @@ import type {
   HintResult,
   Invitation,
   InvitationSettings,
+  ConfirmLinkResult,
   LinkResult,
   MatchResult,
   MoveResult,
@@ -64,8 +65,11 @@ export interface GatewayClient {
    *  cosmetic seed for a brand-new account). */
   authVK(params: string, displayName: string): Promise<Session>;
   authGuest(locale?: string): Promise<Session>;
-  authEmailRequest(email: string): Promise<void>;
+  authEmailRequest(email: string, language: string): Promise<void>;
   authEmailLogin(email: string, code: string): Promise<Session>;
+  /** Confirm a one-tap email deeplink token: a login returns a session to adopt; a
+   *  link returns a status ('confirmed' | 'merge_required'). */
+  confirmEmailLink(token: string): Promise<ConfirmLinkResult>;
 
   // --- profile / lists ---
   profileGet(): Promise<Profile>;

ui/src/lib/codec.test.ts

@@ -21,6 +21,7 @@ import {
   decodeStats,
   encodeCheckWord,
   encodeEmailRequest,
+  encodeEmailConfirmLink,
   encodeFeedbackSubmit,
   encodeDraftSave,
   encodeEnqueue,
@@ -117,10 +118,16 @@ describe('codec', () => {
     expect(guest.browserTz()).toBe('-05:30');
 
     const email = fb.EmailRequestRequest.getRootAsEmailRequestRequest(
-      new ByteBuffer(encodeEmailRequest('a@example.com', '+00:00')),
+      new ByteBuffer(encodeEmailRequest('a@example.com', '+00:00', 'en')),
     );
     expect(email.email()).toBe('a@example.com');
     expect(email.browserTz()).toBe('+00:00');
+    expect(email.language()).toBe('en');
+
+    const confirm = fb.EmailConfirmLinkRequest.getRootAsEmailConfirmLinkRequest(
+      new ByteBuffer(encodeEmailConfirmLink('tok-abc')),
+    );
+    expect(confirm.token()).toBe('tok-abc');
 
     const vk = fb.VKLoginRequest.getRootAsVKLoginRequest(
       new ByteBuffer(encodeVKLogin('vk_user_id=494075&vk_ts=1&sign=abc', '+03:00', 'Иван Петров')),

ui/src/lib/codec.ts

@@ -31,6 +31,7 @@ import type {
   Invitation,
   InvitationInvitee,
   InvitationSettings,
+  ConfirmLinkResult,
   LinkResult,
   MatchResult,
   MoveRecord,
@@ -212,13 +213,15 @@ export function encodeGuestLogin(locale: string, browserTz: string): Uint8Array
   return finish(b, fb.GuestLoginRequest.endGuestLoginRequest(b));
 }
 
-export function encodeEmailRequest(email: string, browserTz: string): Uint8Array {
+export function encodeEmailRequest(email: string, browserTz: string, language: string): Uint8Array {
   const b = new Builder(128);
   const e = b.createString(email);
   const tz = b.createString(browserTz);
+  const l = b.createString(language);
   fb.EmailRequestRequest.startEmailRequestRequest(b);
   fb.EmailRequestRequest.addEmail(b, e);
   fb.EmailRequestRequest.addBrowserTz(b, tz);
+  fb.EmailRequestRequest.addLanguage(b, l);
   return finish(b, fb.EmailRequestRequest.endEmailRequestRequest(b));
 }
 
@@ -232,6 +235,14 @@ export function encodeEmailLogin(email: string, code: string): Uint8Array {
   return finish(b, fb.EmailLoginRequest.endEmailLoginRequest(b));
 }
 
+export function encodeEmailConfirmLink(token: string): Uint8Array {
+  const b = new Builder(128);
+  const t = b.createString(token);
+  fb.EmailConfirmLinkRequest.startEmailConfirmLinkRequest(b);
+  fb.EmailConfirmLinkRequest.addToken(b, t);
+  return finish(b, fb.EmailConfirmLinkRequest.endEmailConfirmLinkRequest(b));
+}
+
 // --- response decoders ---
 
 function s(v: string | null): string {
@@ -730,6 +741,16 @@ export function decodeLinkResult(buf: Uint8Array): LinkResult {
   };
 }
 
+export function decodeConfirmLinkResult(buf: Uint8Array): ConfirmLinkResult {
+  const r = fb.EmailConfirmLinkResult.getRootAsEmailConfirmLinkResult(new ByteBuffer(buf));
+  const sess = r.session();
+  return {
+    purpose: (s(r.purpose()) || 'link') as ConfirmLinkResult['purpose'],
+    status: (s(r.status()) || 'confirmed') as ConfirmLinkResult['status'],
+    session: sess ? sessionFromTable(sess) : null,
+  };
+}
+
 // --- social decoders ---
 
 function decodeAccountRef(r: fb.AccountRef): AccountRef {

ui/src/lib/i18n/en.ts

@@ -36,6 +36,12 @@ export const en = {
   'login.sendCode': 'Send code',
   'login.codePlaceholder': '6-digit code',
   'login.signIn': 'Sign in',
+  'confirm.prompt': 'Confirm your email to finish.',
+  'confirm.action': 'Confirm',
+  'confirm.linked': 'Email confirmed.',
+  'confirm.merge': 'Almost done — finish the merge in the app.',
+  'confirm.close': 'You can close this window and return to the game.',
+  'confirm.expired': 'This link is invalid or has expired. Request a new code.',
   'login.codeSent': 'We sent a code to {email}.',
 
   'lobby.activeGames': 'Active games',

ui/src/lib/i18n/ru.ts

@@ -37,6 +37,12 @@ export const ru: Record<MessageKey, string> = {
   'login.sendCode': 'Отправить код',
   'login.codePlaceholder': 'Код из 6 цифр',
   'login.signIn': 'Войти',
+  'confirm.prompt': 'Подтвердите почту, чтобы завершить.',
+  'confirm.action': 'Подтвердить',
+  'confirm.linked': 'Почта подтверждена.',
+  'confirm.merge': 'Почти готово — завершите объединение в приложении.',
+  'confirm.close': 'Можно закрыть это окно и вернуться в игру.',
+  'confirm.expired': 'Ссылка недействительна или истекла. Запросите новый код.',
   'login.codeSent': 'Мы отправили код на {email}.',
 
   'lobby.activeGames': 'Активные игры',

ui/src/lib/mock/client.ts

@@ -27,6 +27,7 @@ import type {
   HintResult,
   Invitation,
   InvitationSettings,
+  ConfirmLinkResult,
   LinkResult,
   MatchResult,
   MoveResult,
@@ -149,7 +150,10 @@ export class MockGateway implements GatewayClient {
   async authGuest(): Promise<Session> {
     return { ...SESSION };
   }
-  async authEmailRequest(): Promise<void> {}
+  async authEmailRequest(_email: string, _language: string): Promise<void> {}
+  async confirmEmailLink(_token: string): Promise<ConfirmLinkResult> {
+    return { purpose: 'link', status: 'confirmed', session: null };
+  }
   async authEmailLogin(): Promise<Session> {
     return { ...SESSION, isGuest: false };
   }

ui/src/lib/model.ts

@@ -355,6 +355,15 @@ export interface LinkResult {
   session: Session | null;
 }
 
+// ConfirmLinkResult is the outcome of a one-tap deeplink confirmation. purpose is
+// 'login' (session carries the minted credential to sign in) or 'link' (status is
+// 'confirmed' or 'merge_required' — the app finishes any merge from its manual flow).
+export interface ConfirmLinkResult {
+  purpose: 'login' | 'link';
+  status: 'confirmed' | 'merge_required';
+  session: Session | null;
+}
+
 export interface MatchResult {
   matched: boolean;
   game?: GameView;

ui/src/lib/routeparse.ts

@@ -15,6 +15,7 @@ export type RouteName =
   | 'friends'
   | 'feedback'
   | 'stats'
+  | 'confirm'
   | 'notfound';
 
 export interface Route {
@@ -58,6 +59,11 @@ export function parse(hash: string): Route {
       return { name: 'feedback', params: {} };
     case 'stats':
       return { name: 'stats', params: {} };
+    case 'confirm':
+      // The one-tap email deeplink: /confirm/<token>. The token is the confirmation
+      // authorization; the screen POSTs it (prefetch-safe), so a mail scanner's GET
+      // does not consume it.
+      return { name: 'confirm', params: { token: seg[1] ?? '' } };
     default:
       return { name: 'notfound', params: {} };
   }

ui/src/lib/transport.ts

@@ -101,8 +101,11 @@ export function createTransport(baseUrl: string): GatewayClient {
     async authGuest(locale) {
       return codec.decodeSession(await exec('auth.guest', codec.encodeGuestLogin(locale ?? '', browserOffset())));
     },
-    async authEmailRequest(email) {
-      await exec('auth.email.request', codec.encodeEmailRequest(email, browserOffset()));
+    async authEmailRequest(email, language) {
+      await exec('auth.email.request', codec.encodeEmailRequest(email, browserOffset(), language));
+    },
+    async confirmEmailLink(token) {
+      return codec.decodeConfirmLinkResult(await exec('auth.email.confirm_link', codec.encodeEmailConfirmLink(token)));
     },
     async authEmailLogin(email, code) {
       return codec.decodeSession(await exec('auth.email.login', codec.encodeEmailLogin(email, code)));

ui/src/screens/Confirm.svelte

@@ -0,0 +1,95 @@
+<script lang="ts">
+  import { confirmDeeplink } from '../lib/app.svelte';
+  import { t } from '../lib/i18n/index.svelte';
+
+  let { token }: { token: string } = $props();
+  // idle → busy → (login navigates away) | linked | merge | error. The token is
+  // confirmed only on the button press (a POST), so a mail scanner prefetching the
+  // link (a GET on the SPA route) never consumes it.
+  let stage = $state<'idle' | 'busy' | 'linked' | 'merge' | 'error'>('idle');
+
+  async function confirm(): Promise<void> {
+    if (!token) {
+      stage = 'error';
+      return;
+    }
+    stage = 'busy';
+    try {
+      const r = await confirmDeeplink(token);
+      // A login has already navigated into the app; a link stays here with a result.
+      stage = r === 'merge_required' ? 'merge' : 'linked';
+    } catch {
+      stage = 'error';
+    }
+  }
+</script>
+
+<main class="confirm">
+  <div class="card">
+    <div class="brand">{t('app.title')}</div>
+    {#if stage === 'idle' || stage === 'busy'}
+      <p>{t('confirm.prompt')}</p>
+      <button class="primary" disabled={stage === 'busy'} onclick={confirm}>
+        {t('confirm.action')}
+      </button>
+    {:else if stage === 'linked'}
+      <p class="ok">{t('confirm.linked')}</p>
+      <p class="muted">{t('confirm.close')}</p>
+    {:else if stage === 'merge'}
+      <p class="ok">{t('confirm.merge')}</p>
+      <p class="muted">{t('confirm.close')}</p>
+    {:else}
+      <p class="err">{t('confirm.expired')}</p>
+    {/if}
+  </div>
+</main>
+
+<style>
+  .confirm {
+    height: 100%;
+    display: grid;
+    place-items: center;
+    padding: 16px;
+  }
+  .card {
+    width: min(94vw, 360px);
+    background: var(--surface);
+    border: 1px solid var(--border);
+    border-radius: var(--radius);
+    box-shadow: var(--shadow);
+    padding: 24px;
+    display: flex;
+    flex-direction: column;
+    gap: 12px;
+    text-align: center;
+  }
+  .brand {
+    font-weight: 700;
+    letter-spacing: 0.04em;
+    color: var(--accent);
+  }
+  p {
+    margin: 0;
+  }
+  .muted {
+    color: var(--text-muted);
+    font-size: 0.9rem;
+  }
+  .ok {
+    font-weight: 600;
+  }
+  .err {
+    color: var(--danger, #c0392b);
+  }
+  button {
+    padding: 12px;
+    border-radius: var(--radius-sm);
+    border: 1px solid var(--accent);
+    font-weight: 600;
+    background: var(--accent);
+    color: var(--accent-text);
+  }
+  button:disabled {
+    opacity: 0.5;
+  }
+</style>