Connect sign-up to Sendico Facts intake (#46)

Reviewed-on: #43

backend/product/README.md

@@ -33,9 +33,10 @@ API versions are installed explicitly by the product composition. See
 mounts, shared lifecycle and adding a future version. Customer profile endpoint
 wiring remains follow-up work.
 
-Sendico integration is not wired. Its organization context belongs only to the
+Optional `api.sendico` connects sign-up to the public individual registry and
-future public HTTP adapter. There is no unused public API snapshot in this module;
+immutable Facts intake. The adapter owns organization context and consumed wire
-copy only the wire definitions consumed by an implemented adapter.
+contracts; local customers retain no platform tenancy. See
+[configuration, recovery and measurement](../../docs/signup-facts.md).
 
 ## Validate
 

backend/product/app/api/config.go

@@ -3,10 +3,12 @@ package api
 import (
 	mwa "git.sendico.io/tech/sxchnge/product/auth/config"
 	"git.sendico.io/tech/sxchnge/product/notifications"
+	"git.sendico.io/tech/sxchnge/product/providers/sendico"
 	verificationconfig "git.sendico.io/tech/sxchnge/product/verification/config"
 )
 
 type Config struct {
+	Sendico *sendico.Config `yaml:"sendico"`
 	// nil preserves the legacy v1 mount; an explicit empty list installs no API.
 	Versions      []Mount                    `yaml:"versions"`
 	Notifications *notifications.Config      `yaml:"notifications"`

backend/product/app/runtime/bootstrap_test.go

@@ -2,16 +2,20 @@ package runtime_test
 
 import (
 	"context"
+	"encoding/base64"
+	"encoding/json"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
 	"os"
+	"path/filepath"
 	"testing"
 	"time"
 
 	"git.sendico.io/tech/sxchnge/product/app/api"
 	"git.sendico.io/tech/sxchnge/product/app/profile"
 	sharedruntime "git.sendico.io/tech/sxchnge/product/app/runtime"
+	"git.sendico.io/tech/sxchnge/product/providers/sendico"
 	"git.sendico.io/tech/sxchnge/shared/database"
 	sharedmodel "git.sendico.io/tech/sxchnge/shared/model"
 	"github.com/go-chi/chi/v5"
@@ -61,4 +65,22 @@ func TestProfileStartsOnEmptyDatabase(t *testing.T) {
 	result = httptest.NewRecorder()
 	root.ServeHTTP(result, httptest.NewRequest(http.MethodPost, "/api/v1/accounts/login", nil))
 	require.Equal(t, http.StatusBadRequest, result.Code)
+	// Enabling the adapter validates credentials, composes once, and does not
+	// register any provider resource until a customer starts sign-up.
+	const source = "507f1f77bcf86cd799439011"
+	claims, err := json.Marshal(map[string]any{"id": source, "exp": time.Now().Add(time.Hour).Unix()})
+	require.NoError(t, err)
+	file := filepath.Join(t.TempDir(), "credential")
+	require.NoError(t, os.WriteFile(file, []byte("header."+base64.RawURLEncoding.EncodeToString(claims)+".signature"), 0600))
+	example.API.Sendico = &sendico.Config{APIURL: "https://api.example/api/v1", OrganizationID: source, SourceID: source, TokenFile: file}
+	dependencies, finish, err := sharedruntime.OpenDependencies(ctx, zap.NewNop(), &example.API, factory)
+	require.NoError(t, err)
+	require.NotNil(t, dependencies.Auth.Facts)
+	require.NoError(t, finish(ctx))
+	example.API.Sendico.TokenFile = ""
+	_, _, err = sharedruntime.OpenDependencies(ctx, zap.NewNop(), &example.API, factory)
+	require.Error(t, err)
+	example.API.Notifications = nil
+	_, _, err = sharedruntime.OpenDependencies(ctx, zap.NewNop(), &example.API, factory)
+	require.Error(t, err)
 }

backend/product/app/runtime/services.go

@@ -8,11 +8,14 @@ import (
 	"git.sendico.io/tech/sxchnge/product/auth/flow"
 	"git.sendico.io/tech/sxchnge/product/auth/storage"
 	"git.sendico.io/tech/sxchnge/product/customers"
+	"git.sendico.io/tech/sxchnge/product/identity"
 	"git.sendico.io/tech/sxchnge/product/notifications"
+	"git.sendico.io/tech/sxchnge/product/providers/sendico"
 	"git.sendico.io/tech/sxchnge/product/twofactor"
 	"git.sendico.io/tech/sxchnge/product/twofactor/delivery"
 	factorstore "git.sendico.io/tech/sxchnge/product/twofactor/store"
 	"git.sendico.io/tech/sxchnge/shared/database"
+	merrors "git.sendico.io/tech/sxchnge/shared/errors"
 	"git.sendico.io/tech/sxchnge/shared/logging"
 	"go.uber.org/zap"
 )
@@ -55,6 +58,18 @@ func OpenDependencies(_ context.Context, logger mlogger.Logger, config *api.Conf
 			return nil, nil, err
 		}
 		deps.Auth.Sender = client
+		if config.Sendico != nil {
+			provider, err := sendico.Open(*config.Sendico)
+			if err != nil {
+				return nil, nil, err
+			}
+			bindings, err := identity.OpenStore(db)
+			if err != nil {
+				return nil, nil, err
+			}
+			deps.Auth.Facts = &identity.Service{Store: bindings, Provider: provider, Logger: logger.Named("signup_facts")}
+			logger.Info("Sendico sign-up facts integration enabled")
+		}
 		records, err := factorstore.Open(logger, db)
 		if err != nil {
 			return nil, nil, err
@@ -64,6 +79,9 @@ func OpenDependencies(_ context.Context, logger mlogger.Logger, config *api.Conf
 			return nil, nil, err
 		}
 	}
+	if config.Sendico != nil && deps.Auth == nil {
+		return nil, nil, merrors.InvalidArgument("Sendico sign-up facts require notifications configuration")
+	}
 	logger.Info("Product dependencies initialized")
 	return deps, cleanup, nil
 }

backend/product/auth/flow/service.go

@@ -26,7 +26,13 @@ import (
 
 const Cooldown = time.Minute
 
+type SignupFacts interface {
+	Ensure(context.Context, *customer.Account) error
+	Ready(context.Context, bson.ObjectID) error
+}
+
 type Service struct {
+	Facts         SignupFacts
 	Accounts      account.DB
 	Customers     accountservice.AccountService
 	Tokens        verification.DB
@@ -85,20 +91,25 @@ func (s *Service) Signup(ctx context.Context, a *customer.Account, ip, key strin
 	if err = s.Limit(ctx, ip, email); err != nil {
 		return nil, err
 	}
-	raw, err := s.Customers.CreateAccount(ctx, a)
+	raw, err := s.Customers.CreateAccountWithActivationKey(ctx, a, s.activationKey(a.Login, key))
 	if errors.Is(err, merrors.ErrDataConflict) {
 		existing, lookup := s.Accounts.GetByEmail(ctx, email)
 		if lookup != nil {
 			return nil, lookup
 		}
 		// A retry after a queue failure may resume only with the original password.
-		if existing.Status != customer.AccountPendingVerification || !existing.MatchPassword(a.Password) {
+		if existing.Status != customer.AccountPendingVerification || existing.IsArchived() || !existing.MatchPassword(a.Password) {
 			return nil, merrors.DataConflict("email already registered")
 		}
 		a = existing
 	} else if err != nil {
 		return nil, err
 	}
+	if s.Facts != nil {
+		if err := s.Facts.Ensure(ctx, a); err != nil {
+			return nil, err
+		}
+	}
 	if raw != "" {
 		u, _ := url.Parse(s.ActivationURL)
 		q := u.Query()
@@ -132,14 +143,22 @@ func (s *Service) ResendActivation(ctx context.Context, email, ip, key string) e
 	if a.Status != customer.AccountPendingVerification || a.IsArchived() {
 		return nil
 	}
+	if s.Facts != nil {
+		if err := s.Facts.Ensure(ctx, a); err != nil {
+			return err
+		}
+	}
 	_, err = s.sendActivation(ctx, a, key)
 	return err
 }
+func (s *Service) activationKey(email, key string) string {
+	return s.key(email, string(verificationmodel.PurposeAccountActivation), "", key)
+}
 func (s *Service) sendActivation(ctx context.Context, a *customer.Account, key string) (time.Time, error) {
 	if strings.TrimSpace(key) == "" || len(key) > 128 {
 		return time.Time{}, merrors.InvalidArgument("idempotency key required")
 	}
-	secretKey := s.key(a.ID.Hex(), string(verificationmodel.PurposeAccountActivation), "", key)
+	secretKey := s.activationKey(a.Login, key)
 	req := verification.NewLinkRequest(a.ID, verificationmodel.PurposeAccountActivation, "").WithTTL(24 * time.Hour).WithCooldown(Cooldown).WithIdempotencyKey(secretKey)
 	req.WithIssuanceLimits(verification.NewIssuanceLimit("auth_delivery", a.Login, 5, time.Hour, time.Now().UTC()))
 	result, err := s.Tokens.CreateWithResult(ctx, req)
@@ -176,6 +195,11 @@ func (s *Service) Activate(ctx context.Context, raw string) error {
 		if a.Status != customer.AccountPendingVerification || a.IsArchived() {
 			return nil, merrors.Unauthorized("account cannot be activated")
 		}
+		if s.Facts != nil {
+			if err := s.Facts.Ready(tx, a.ID); err != nil {
+				return nil, err
+			}
+		}
 		return nil, s.Accounts.Patch(tx, a.ID, repository.Patch().Set(repository.Field("status"), customer.AccountActive))
 	})
 	return err

backend/product/auth/flow/service_test.go

@@ -55,7 +55,7 @@ func TestIssueRetriesSamePayloadAndBindsServerSecret(t *testing.T) {
 	require.Equal(t, sender.messages[0], sender.messages[1])
 	require.Equal(t, "ru", sender.messages[0].Locale)
 	service.Secret = []byte(strings.Repeat("b", 32))
-	require.NotEqual(t, key, service.key(a.ID.Hex(), "account_activation", "client-key"))
+	require.NotEqual(t, key, service.activationKey(a.Login, "client-key"))
 	tokens.result.ExpiresAt = time.Now().Add(-time.Minute)
 	_, err = service.sendActivation(context.Background(), a, "expired")
 	require.ErrorIs(t, err, verification.ErrTokenExpired)

backend/product/auth/http/v1/public/facts_test.go

@@ -0,0 +1,29 @@
+package public
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	merrors "git.sendico.io/tech/sxchnge/shared/errors"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/zap"
+)
+
+func TestFactsAssistanceHasTypedPrivacySafeResponse(t *testing.T) {
+	router := &PublicRouter{logger: zap.NewNop(), service: "accounts"}
+	request := httptest.NewRequest(http.MethodPost, "/api/v1/accounts/signup", nil)
+	response := httptest.NewRecorder()
+	router.flowError(merrors.FailedPrecondition("private upstream detail"))(response, request)
+	require.Equal(t, http.StatusServiceUnavailable, response.Code)
+	require.Equal(t, "no-store", response.Header().Get("Cache-Control"))
+	var envelope struct {
+		Data struct {
+			Error string `json:"error"`
+		}
+	}
+	require.NoError(t, json.Unmarshal(response.Body.Bytes(), &envelope))
+	require.Equal(t, "signup_attention_required", envelope.Data.Error)
+	require.NotContains(t, response.Body.String(), "private upstream detail")
+}

backend/product/auth/http/v1/public/verification.go

@@ -72,6 +72,8 @@ func (pr *PublicRouter) flowError(err error) http.HandlerFunc {
 		return pr.loginRateLimited(details.RetryAfter)
 	}
 	switch {
+	case errors.Is(err, merrors.ErrFailedPrecondition):
+		return response.Error(pr.logger, pr.service, http.StatusServiceUnavailable, "signup_attention_required", "We could not finish setting up your account. Please contact support.")
 	case errors.Is(err, verification.ErrTokenExpired):
 		return response.BadRequest(pr.logger, pr.service, "expired", "Verification expired; request a new email")
 	case errors.Is(err, verification.ErrTokenAttemptsExceeded):

backend/product/auth/http/v1/public/verification_integration_test.go

@@ -15,6 +15,7 @@ import (
 	authstorage "git.sendico.io/tech/sxchnge/product/auth/storage"
 	accountservice "git.sendico.io/tech/sxchnge/product/customers"
 	customer "git.sendico.io/tech/sxchnge/product/customers/model"
+	"git.sendico.io/tech/sxchnge/product/identity"
 	"git.sendico.io/tech/sxchnge/product/notifications"
 	session "git.sendico.io/tech/sxchnge/product/sessions/model"
 	"git.sendico.io/tech/sxchnge/product/twofactor"
@@ -26,6 +27,7 @@ import (
 	"github.com/go-chi/chi/v5"
 	"github.com/stretchr/testify/require"
 	"github.com/testcontainers/testcontainers-go/modules/mongodb"
+	"go.mongodb.org/mongo-driver/v2/bson"
 	"go.uber.org/zap"
 )
 
@@ -34,6 +36,38 @@ type capturedMail struct {
 	fail     bool
 }
 
+type signupProvider struct {
+	registrations, submissions int
+	fail                       bool
+	last                       identity.Facts
+}
+
+func (*signupProvider) Namespace() string { return "test-provider" }
+func (p *signupProvider) Register(context.Context, string) (string, error) {
+	p.registrations++
+	return "subject", nil
+}
+func (p *signupProvider) Submit(_ context.Context, subject, source string, facts identity.Facts) (identity.Receipt, error) {
+	p.submissions++
+	p.last = facts
+	if p.fail {
+		return identity.Receipt{}, merrors.ServiceUnavailable("provider unavailable")
+	}
+	return identity.Receipt{SubjectRef: subject, SubmissionRef: "submission", AcceptedAt: time.Now().UTC()}, nil
+}
+
+type activationGuard struct {
+	flow.SignupFacts
+	block bool
+}
+
+func (g *activationGuard) Ready(ctx context.Context, id bson.ObjectID) error {
+	if g.block {
+		return merrors.ServiceUnavailable("intake receipt unavailable")
+	}
+	return g.SignupFacts.Ready(ctx, id)
+}
+
 func (m *capturedMail) Send(_ context.Context, r notifications.Message) error {
 	m.messages = append(m.messages, r)
 	if m.fail {
@@ -64,6 +98,10 @@ func TestSignupActivationAndLoginEmailFlow(t *testing.T) {
 	mail := &capturedMail{}
 	service := &flow.Service{Accounts: stores.Accounts, Customers: customers, Tokens: stores.Verification, Transactions: factory.TransactionFactory(), Attempts: stores.LoginAttempts, Sender: mail, Secret: []byte(strings.Repeat("s", 32)), ActivationURL: "https://app.example/verify-email"}
 	require.NoError(t, service.Validate())
+	bindings, err := identity.OpenStore(factory)
+	require.NoError(t, err)
+	provider := &signupProvider{fail: true}
+	service.Facts = &identity.Service{Store: bindings, Provider: provider, Logger: zap.NewNop()}
 	// Keep the real verification/customer stores and capture only session writes.
 	sessions := &testRefreshTokenDB{client: &session.Client{ClientID: "web"}}
 	records, err := factorstore.Open(zap.NewNop(), factory)
@@ -83,7 +121,22 @@ func TestSignupActivationAndLoginEmailFlow(t *testing.T) {
 	}
 	signup := map[string]any{"name": "Customer", "email": "USER@example.com", "password": " correct password ", "locale": "ru", "idempotencyKey": "signup-one"}
 	w := post("signup", signup)
+	require.Equal(t, 503, w.Code, w.Body.String())
+	require.Empty(t, mail.messages)
+	require.Equal(t, 1, provider.registrations)
+	require.Equal(t, 503, post("verification/send", map[string]string{"email": "user@example.com", "idempotencyKey": "failed-resend"}).Code)
+	require.Empty(t, mail.messages)
+	// Only the original password can resume a pending local customer.
+	signup["password"] = "different password"
+	require.Equal(t, 400, post("signup", signup).Code)
+	signup["password"] = " correct password "
+	signup["name"] = "Changed retry name"
+	provider.fail = false
+	w = post("signup", signup)
 	require.Equal(t, 202, w.Code, w.Body.String())
+	require.Equal(t, 1, provider.registrations)
+	require.Equal(t, "Customer", provider.last.FullName)
+	require.Equal(t, "user@example.com", provider.last.Email)
 	require.Len(t, mail.messages, 1)
 	require.Equal(t, "auth.activation", mail.messages[0].Template)
 	require.Equal(t, "user@example.com", mail.messages[0].Email)
@@ -95,9 +148,18 @@ func TestSignupActivationAndLoginEmailFlow(t *testing.T) {
 	a, err := stores.Accounts.GetByEmail(ctx, "user@example.com")
 	require.NoError(t, err)
 	require.False(t, a.IsActive())
+	require.Equal(t, a.ID.Hex(), provider.last.CustomerRef)
+	require.NoError(t, service.Facts.Ready(ctx, a.ID))
 	login := map[string]any{"login": map[string]string{"login": "user@example.com", "password": " correct password "}, "clientId": "web", "deviceId": "browser"}
 	require.Equal(t, 403, post("login", login).Code)
 	require.Equal(t, 400, post("verification/confirm", map[string]string{"token": "invalid"}).Code)
+	guard := &activationGuard{SignupFacts: service.Facts, block: true}
+	service.Facts = guard
+	require.Equal(t, 503, post("verification/confirm", map[string]string{"token": activation}).Code)
+	a, err = stores.Accounts.GetByEmail(ctx, a.Login)
+	require.NoError(t, err)
+	require.False(t, a.IsActive())
+	guard.block = false
 	w = post("verification/confirm", map[string]string{"token": activation})
 	require.Equal(t, 202, w.Code, w.Body.String())
 	require.Equal(t, 400, post("verification/confirm", map[string]string{"token": activation}).Code)

backend/product/config.example.yml

@@ -9,6 +9,13 @@ database:
     uri_env: SXCHNGE_MONGO_URI
     database: sxchnge
 api:
+  # Optional public Sendico facts integration. Enable with provisioned values;
+  # omit this block to retain local-only sign-up. See docs/signup-facts.md.
+  # sendico:
+  #   api_url: https://sendico.example/api/v1
+  #   organization_ref: <sxchnge-organization-object-id>
+  #   source_account_ref: <integration-account-object-id>
+  #   token_file: /run/sxchnge/sendico-token
   # Optional: omit for v1 at SXCHNGE_API_ENDPOINT; [] disables application APIs.
   # versions:
   #   - version: v1

backend/product/customers/internal/service.go

@@ -119,6 +119,17 @@ func (s *service) CreateAccount(
 	ctx context.Context,
 	acct *customermodel.Account,
 ) (string, error) {
+	return s.createAccount(ctx, acct, "")
+}
+
+func (s *service) CreateAccountWithActivationKey(ctx context.Context, acct *customermodel.Account, key string) (string, error) {
+	if len(key) < 32 || len(key) > 128 {
+		return "", merrors.InvalidArgument("server activation key required")
+	}
+	return s.createAccount(ctx, acct, key)
+}
+
+func (s *service) createAccount(ctx context.Context, acct *customermodel.Account, key string) (string, error) {
 	if acct == nil {
 		return "", merrors.InvalidArgument("account is required")
 	}
@@ -137,7 +148,7 @@ func (s *service) CreateAccount(
 		if err := s.accountDB.Create(tx, saved); err != nil {
 			return nil, err
 		}
-		return s.VerifyAccount(tx, saved)
+		return s.vdb.Create(tx, verification.NewLinkRequest(saved.ID, verificationmodel.PurposeAccountActivation, "").WithTTL(24*time.Hour).WithIdempotencyKey(key))
 	})
 	if err != nil {
 		if errors.Is(err, merrors.ErrDataConflict) {

backend/product/customers/types.go

@@ -36,6 +36,9 @@ type AccountService interface {
 		ctx context.Context,
 		acct *customermodel.Account,
 	) (verificationToken string, err error)
+	// CreateAccountWithActivationKey preserves atomic creation and lets the auth
+	// service replay an unsent initial token. The key must be server-secret-derived.
+	CreateAccountWithActivationKey(context.Context, *customermodel.Account, string) (string, error)
 
 	VerifyAccount(
 		ctx context.Context,

backend/product/identity/metrics.go

@@ -0,0 +1,9 @@
+package identity
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+var requests = promauto.NewCounterVec(prometheus.CounterOpts{Name: "sxchnge_signup_facts_total", Help: "Sign-up facts handoff attempts; acceptance is not verification."}, []string{"outcome"})
+var duration = promauto.NewHistogram(prometheus.HistogramOpts{Name: "sxchnge_signup_facts_duration_seconds", Help: "Sign-up facts handoff latency including retries."})

backend/product/identity/model.go

@@ -0,0 +1,39 @@
+// Package identity owns the durable sign-up facts handoff, not KYC decisions.
+package identity
+
+import (
+	"time"
+
+	"git.sendico.io/tech/sxchnge/shared/database/record"
+	"go.mongodb.org/mongo-driver/v2/bson"
+)
+
+// Facts is a snapshot of local sign-up assertions. It never contains credentials.
+type Facts struct {
+	FullName    string `bson:"fullName"`
+	Email       string `bson:"email"`
+	CustomerRef string `bson:"customerRef"`
+}
+
+type Receipt struct {
+	SubmissionRef string    `bson:"submissionRef"`
+	SubjectRef    string    `bson:"subjectRef"`
+	AcceptedAt    time.Time `bson:"acceptedAt"`
+}
+
+// Binding uses the local customer ID as its primary key. Namespace is an opaque
+// adapter configuration fingerprint; no platform tenancy enters the customer model.
+type Binding struct {
+	storable.Base       `bson:",inline"`
+	Namespace           string    `bson:"namespace"`
+	RegistrationRequest string    `bson:"registrationRequest"`
+	Facts               Facts     `bson:"facts"`
+	Registering         bool      `bson:"registering"`
+	RegisteringAt       time.Time `bson:"registeringAt"`
+	SubjectRef          string    `bson:"subjectRef"`
+	Receipt             *Receipt  `bson:"receipt,omitempty"`
+}
+
+func (*Binding) Collection() string { return "signup_facts" }
+
+func sourceRef(id bson.ObjectID) string { return "sxchnge:signup:" + id.Hex() }

backend/product/identity/service.go

@@ -0,0 +1,132 @@
+package identity
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	customer "git.sendico.io/tech/sxchnge/product/customers/model"
+	merrors "git.sendico.io/tech/sxchnge/shared/errors"
+	mlogger "git.sendico.io/tech/sxchnge/shared/logging"
+	"go.mongodb.org/mongo-driver/v2/bson"
+	"go.uber.org/zap"
+)
+
+type Provider interface {
+	Namespace() string
+	Register(context.Context, string) (string, error)
+	Submit(context.Context, string, string, Facts) (Receipt, error)
+}
+
+type Service struct {
+	Store    Store
+	Provider Provider
+	Logger   mlogger.Logger
+}
+
+func unavailable() error { return merrors.ServiceUnavailable("sign-up facts unavailable") }
+
+// Ensure completes only after a provider receipt has been persisted. Registration
+// has no idempotency contract, so its durable claim is never automatically expired.
+func (s *Service) Ensure(ctx context.Context, a *customer.Account) (result error) {
+	if a == nil || a.ID.IsZero() {
+		return merrors.InvalidArgument("customer required")
+	}
+	started := time.Now()
+	requestRef := ""
+	outcome := "unavailable"
+	defer func() {
+		requests.WithLabelValues(outcome).Inc()
+		duration.Observe(time.Since(started).Seconds())
+		fields := []zap.Field{zap.String("account_ref", a.ID.Hex()), zap.String("request_ref", requestRef), zap.String("outcome", outcome)}
+		if result != nil {
+			s.Logger.Warn("Sign-up facts handoff incomplete", fields...)
+		} else {
+			s.Logger.Info("Sign-up facts handoff completed", fields...)
+		}
+	}()
+	namespace := s.Provider.Namespace()
+	b, err := s.Store.Get(ctx, a.ID)
+	if errors.Is(err, merrors.ErrNoData) {
+		b = &Binding{Namespace: namespace, RegistrationRequest: bson.NewObjectID().Hex(), Facts: Facts{FullName: a.Name, Email: a.Login, CustomerRef: a.ID.Hex()}}
+		b.SetID(a.ID)
+		if err = s.Store.Create(ctx, b); err != nil {
+			if !errors.Is(err, merrors.ErrDataConflict) {
+				return merrors.OpaqueWrap(merrors.ErrServiceUnavailable, err, "persist sign-up facts")
+			}
+			b, err = s.Store.Get(ctx, a.ID)
+		}
+	}
+	if err != nil {
+		return merrors.OpaqueWrap(merrors.ErrServiceUnavailable, err, "load sign-up facts")
+	}
+	requestRef = b.RegistrationRequest
+	if b.Namespace != namespace {
+		outcome = "attention_required"
+		return merrors.FailedPrecondition("sign-up provider binding changed")
+	}
+	if b.Receipt != nil {
+		outcome = "replayed"
+		return nil
+	}
+	if b.SubjectRef == "" {
+		claimed, err := s.Store.Claim(ctx, a.ID, namespace)
+		if err != nil {
+			return merrors.OpaqueWrap(merrors.ErrServiceUnavailable, err, "claim individual registration")
+		}
+		if !claimed {
+			// Another request may have completed while this request was claiming.
+			b, err = s.Store.Get(ctx, a.ID)
+			if err != nil {
+				return merrors.OpaqueWrap(merrors.ErrServiceUnavailable, err, "reload sign-up facts")
+			}
+			if b.SubjectRef == "" {
+				if b.RegisteringAt.Add(30 * time.Second).After(time.Now()) {
+					return unavailable()
+				}
+				outcome = "attention_required"
+				return merrors.FailedPrecondition("individual registration requires reconciliation")
+			}
+		} else {
+			subject, err := s.Provider.Register(ctx, b.RegistrationRequest)
+			if err != nil {
+				outcome = "attention_required"
+				return merrors.OpaqueWrap(merrors.ErrFailedPrecondition, err, "individual registration requires reconciliation")
+			}
+			// Persist even if the browser left while Sendico accepted registration.
+			saveCtx, cancel := context.WithTimeout(context.WithoutCancel(ctx), 5*time.Second)
+			err = s.Store.Bind(saveCtx, a.ID, namespace, subject)
+			cancel()
+			if err != nil {
+				outcome = "attention_required"
+				s.Logger.Warn("Registered individual binding needs reconciliation", zap.String("account_ref", a.ID.Hex()), zap.String("subject_ref", subject))
+				return merrors.OpaqueWrap(merrors.ErrFailedPrecondition, err, "persist individual binding")
+			}
+			b.SubjectRef = subject
+		}
+	}
+	receipt, err := s.Provider.Submit(ctx, b.SubjectRef, sourceRef(a.ID), b.Facts)
+	if err != nil {
+		return merrors.OpaqueWrap(merrors.ErrServiceUnavailable, err, "submit sign-up facts")
+	}
+	if receipt.SubjectRef != b.SubjectRef || receipt.SubmissionRef == "" || receipt.AcceptedAt.IsZero() {
+		return unavailable()
+	}
+	if err = s.Store.Accept(ctx, a.ID, namespace, receipt); err != nil {
+		return merrors.OpaqueWrap(merrors.ErrServiceUnavailable, err, "persist facts receipt")
+	}
+	outcome = "accepted"
+	return nil
+}
+
+// Ready checks confirmed intake without external I/O inside activation transactions.
+func (s *Service) Ready(ctx context.Context, id bson.ObjectID) error {
+	b, err := s.Store.Get(ctx, id)
+	if err != nil {
+		return merrors.OpaqueWrap(merrors.ErrServiceUnavailable, err, "load facts receipt")
+	}
+	if b.Namespace != s.Provider.Namespace() || b.Receipt == nil {
+		return unavailable()
+	}
+	return nil
+}

backend/product/identity/service_test.go

@@ -0,0 +1,213 @@
+package identity
+
+import (
+	"context"
+	"sync"
+	"testing"
+	"time"
+
+	customer "git.sendico.io/tech/sxchnge/product/customers/model"
+	merrors "git.sendico.io/tech/sxchnge/shared/errors"
+	"github.com/stretchr/testify/require"
+	"go.mongodb.org/mongo-driver/v2/bson"
+	"go.uber.org/zap"
+	"go.uber.org/zap/zaptest/observer"
+)
+
+type memoryStore struct {
+	mu                 sync.Mutex
+	rows               map[bson.ObjectID]Binding
+	bindErr, acceptErr error
+}
+
+func (s *memoryStore) Get(_ context.Context, id bson.ObjectID) (*Binding, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	b, ok := s.rows[id]
+	if !ok {
+		return nil, merrors.NoData("missing")
+	}
+	return &b, nil
+}
+func (s *memoryStore) Create(_ context.Context, b *Binding) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if _, ok := s.rows[b.ID]; ok {
+		return merrors.DataConflict("duplicate")
+	}
+	s.rows[b.ID] = *b
+	return nil
+}
+func (s *memoryStore) Claim(_ context.Context, id bson.ObjectID, namespace string) (bool, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	b := s.rows[id]
+	if b.Namespace != namespace || b.Registering || b.SubjectRef != "" {
+		return false, nil
+	}
+	b.Registering = true
+	b.RegisteringAt = time.Now()
+	s.rows[id] = b
+	return true, nil
+}
+func (s *memoryStore) Bind(_ context.Context, id bson.ObjectID, namespace, subject string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.bindErr != nil {
+		return s.bindErr
+	}
+	b := s.rows[id]
+	b.SubjectRef = subject
+	b.Registering = false
+	s.rows[id] = b
+	return nil
+}
+func (s *memoryStore) Accept(_ context.Context, id bson.ObjectID, namespace string, r Receipt) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.acceptErr != nil {
+		return s.acceptErr
+	}
+	b := s.rows[id]
+	b.Receipt = &r
+	s.rows[id] = b
+	return nil
+}
+
+type providerStub struct {
+	registrations, submissions int
+	registerErr, submitErr     error
+	snapshots                  []Facts
+	sources                    []string
+	entered, release           chan struct{}
+}
+
+func (*providerStub) Namespace() string { return "provider-1" }
+func (p *providerStub) Register(context.Context, string) (string, error) {
+	p.registrations++
+	if p.entered != nil {
+		close(p.entered)
+		<-p.release
+	}
+	return "subject-1", p.registerErr
+}
+func (p *providerStub) Submit(_ context.Context, subject, source string, f Facts) (Receipt, error) {
+	p.submissions++
+	p.snapshots = append(p.snapshots, f)
+	p.sources = append(p.sources, source)
+	return Receipt{SubjectRef: subject, SubmissionRef: "submission-1", AcceptedAt: time.Now()}, p.submitErr
+}
+func fixture() (*Service, *memoryStore, *providerStub, *customer.Account) {
+	store := &memoryStore{rows: map[bson.ObjectID]Binding{}}
+	provider := &providerStub{}
+	a := &customer.Account{}
+	a.ID = bson.NewObjectID()
+	a.Name = "Ada Lovelace"
+	a.Login = "ada@example.com"
+	a.Password = "never transmit"
+	return &Service{Store: store, Provider: provider, Logger: zap.NewNop()}, store, provider, a
+}
+
+func TestIntakeRetryUsesPersistedSubjectSnapshotAndStableSource(t *testing.T) {
+	s, store, p, a := fixture()
+	p.submitErr = merrors.ServiceUnavailable("upstream")
+	require.Error(t, s.Ensure(context.Background(), a))
+	require.Error(t, s.Ready(context.Background(), a.ID))
+	require.Equal(t, 1, p.registrations)
+	b, err := store.Get(context.Background(), a.ID)
+	require.NoError(t, err)
+	require.Equal(t, "subject-1", b.SubjectRef)
+	require.Nil(t, b.Receipt)
+	a.Name = "changed retry"
+	p.submitErr = nil
+	require.NoError(t, s.Ensure(context.Background(), a))
+	require.NoError(t, s.Ready(context.Background(), a.ID))
+	require.Equal(t, 1, p.registrations)
+	require.Equal(t, 2, p.submissions)
+	require.Equal(t, p.snapshots[0], p.snapshots[1])
+	require.Equal(t, "Ada Lovelace", p.snapshots[1].FullName)
+	require.Equal(t, p.sources[0], p.sources[1])
+	require.NoError(t, s.Ensure(context.Background(), a))
+	require.Equal(t, 2, p.submissions)
+	other := a.Copy()
+	other.ID = bson.NewObjectID()
+	require.Error(t, s.Ready(context.Background(), other.ID))
+}
+func TestLostAcceptanceReceiptIsSafelyReplayed(t *testing.T) {
+	s, store, p, a := fixture()
+	store.acceptErr = merrors.ServiceUnavailable("storage")
+	require.Error(t, s.Ensure(context.Background(), a))
+	store.acceptErr = nil
+	require.NoError(t, s.Ensure(context.Background(), a))
+	require.Equal(t, 1, p.registrations)
+	require.Equal(t, 2, p.submissions)
+	require.Equal(t, p.sources[0], p.sources[1])
+}
+func TestAmbiguousRegistrationNeverAutomaticallyRegistersAgain(t *testing.T) {
+	for _, bindFailure := range []bool{false, true} {
+		t.Run(map[bool]string{false: "request", true: "binding"}[bindFailure], func(t *testing.T) {
+			s, store, p, a := fixture()
+			if bindFailure {
+				store.bindErr = merrors.ServiceUnavailable("storage")
+			} else {
+				p.registerErr = merrors.ServiceUnavailable("lost response")
+			}
+			require.ErrorIs(t, s.Ensure(context.Background(), a), merrors.ErrFailedPrecondition)
+			b := store.rows[a.ID]
+			b.RegisteringAt = time.Now().Add(-time.Minute)
+			store.rows[a.ID] = b
+			store.bindErr = nil
+			p.registerErr = nil
+			require.ErrorIs(t, s.Ensure(context.Background(), a), merrors.ErrFailedPrecondition)
+			require.Equal(t, 1, p.registrations)
+			require.Zero(t, p.submissions)
+		})
+	}
+}
+func TestConcurrentRequestCannotRegisterSameCustomerTwice(t *testing.T) {
+	s, _, p, a := fixture()
+	p.entered = make(chan struct{})
+	p.release = make(chan struct{})
+	done := make(chan error, 1)
+	go func() { done <- s.Ensure(context.Background(), a) }()
+	<-p.entered
+	require.ErrorIs(t, s.Ensure(context.Background(), a), merrors.ErrServiceUnavailable)
+	close(p.release)
+	require.NoError(t, <-done)
+	require.Equal(t, 1, p.registrations)
+	require.NoError(t, s.Ensure(context.Background(), a))
+	require.Equal(t, 1, p.submissions)
+}
+func TestNamespaceChangeFailsClosed(t *testing.T) {
+	s, store, p, a := fixture()
+	require.NoError(t, s.Ensure(context.Background(), a))
+	b := store.rows[a.ID]
+	b.Namespace = "other-account-or-organization"
+	store.rows[a.ID] = b
+	require.ErrorIs(t, s.Ensure(context.Background(), a), merrors.ErrFailedPrecondition)
+	require.Error(t, s.Ready(context.Background(), a.ID))
+	require.Equal(t, 1, p.submissions)
+}
+
+func TestHandoffLogsExcludeAssertionsAndCredentials(t *testing.T) {
+	s, _, p, a := fixture()
+	core, logs := observer.New(zap.InfoLevel)
+	s.Logger = zap.New(core)
+	p.submitErr = merrors.ServiceUnavailable(a.Login + " " + a.Password)
+	require.Error(t, s.Ensure(context.Background(), a))
+	p.submitErr = nil
+	require.NoError(t, s.Ensure(context.Background(), a))
+	require.Len(t, logs.All(), 2)
+	for _, entry := range logs.All() {
+		require.NotContains(t, entry.Message, a.Login)
+		require.NotContains(t, entry.Message, a.Name)
+		fields := entry.ContextMap()
+		require.Equal(t, a.ID.Hex(), fields["account_ref"])
+		require.NotEmpty(t, fields["request_ref"])
+		for _, value := range fields {
+			require.NotEqual(t, a.Login, value)
+			require.NotEqual(t, a.Name, value)
+			require.NotEqual(t, a.Password, value)
+		}
+	}
+}

backend/product/identity/store.go

@@ -0,0 +1,68 @@
+package identity
+
+import (
+	"context"
+	"time"
+
+	db "git.sendico.io/tech/sxchnge/shared/database"
+	deps "git.sendico.io/tech/sxchnge/shared/database/dependencies"
+	"git.sendico.io/tech/sxchnge/shared/database/repository"
+	"git.sendico.io/tech/sxchnge/shared/database/source"
+	"go.mongodb.org/mongo-driver/v2/bson"
+)
+
+type Store interface {
+	Get(context.Context, bson.ObjectID) (*Binding, error)
+	Create(context.Context, *Binding) error
+	Claim(context.Context, bson.ObjectID, string) (bool, error)
+	Bind(context.Context, bson.ObjectID, string, string) error
+	Accept(context.Context, bson.ObjectID, string, Receipt) error
+}
+
+type mongoStore struct{ records repository.Repository }
+
+func OpenStore(factory db.Factory) (Store, error) {
+	d, err := deps.ResolveDependencies(factory)
+	if err != nil {
+		return nil, err
+	}
+	return &mongoStore{records: repository.CreateRepository(source.Majority(d.Database), "signup_facts")}, nil
+}
+
+func (s *mongoStore) Get(ctx context.Context, id bson.ObjectID) (*Binding, error) {
+	b := &Binding{}
+	err := s.records.Get(ctx, id, b)
+	return b, err
+}
+func (s *mongoStore) Create(ctx context.Context, b *Binding) error {
+	return s.records.Insert(ctx, b, nil)
+}
+func scoped(id bson.ObjectID, namespace string) repository.FilterQuery {
+	return repository.IDFilter(id).Filter(repository.Field("namespace"), namespace)
+}
+func (s *mongoStore) Claim(ctx context.Context, id bson.ObjectID, namespace string) (bool, error) {
+	query := scoped(id, namespace).Filter(repository.Field("registering"), false).Filter(repository.Field("subjectRef"), "")
+	return s.records.PatchOneByFilter(ctx, query, repository.Patch().Set(repository.Field("registering"), true).Set(repository.Field("registeringAt"), time.Now().UTC()), &Binding{})
+}
+func (s *mongoStore) Bind(ctx context.Context, id bson.ObjectID, namespace, subject string) error {
+	query := scoped(id, namespace).Filter(repository.Field("registering"), true).Filter(repository.Field("subjectRef"), "")
+	matched, err := s.records.PatchOneByFilter(ctx, query, repository.Patch().Set(repository.Field("subjectRef"), subject).Set(repository.Field("registering"), false), &Binding{})
+	if err != nil {
+		return err
+	}
+	if !matched {
+		return unavailable()
+	}
+	return nil
+}
+func (s *mongoStore) Accept(ctx context.Context, id bson.ObjectID, namespace string, receipt Receipt) error {
+	query := scoped(id, namespace).Filter(repository.Field("subjectRef"), receipt.SubjectRef)
+	matched, err := s.records.PatchOneByFilter(ctx, query, repository.Patch().Set(repository.Field("receipt"), receipt), &Binding{})
+	if err != nil {
+		return err
+	}
+	if !matched {
+		return unavailable()
+	}
+	return nil
+}

backend/product/identity/store_test.go

@@ -0,0 +1,81 @@
+package identity
+
+import (
+	"context"
+	"net/url"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	db "git.sendico.io/tech/sxchnge/shared/database"
+	merrors "git.sendico.io/tech/sxchnge/shared/errors"
+	sharedmodel "git.sendico.io/tech/sxchnge/shared/model"
+	"github.com/stretchr/testify/require"
+	"github.com/testcontainers/testcontainers-go/modules/mongodb"
+	"go.mongodb.org/mongo-driver/v2/bson"
+	"go.uber.org/zap"
+)
+
+func TestDurableBindingClaimsAndIsolation(t *testing.T) {
+	ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
+	defer cancel()
+	container, err := mongodb.Run(ctx, "mongo:latest", mongodb.WithReplicaSet("rs"))
+	require.NoError(t, err)
+	t.Cleanup(func() { require.NoError(t, container.Terminate(context.Background())) })
+	uri, err := container.ConnectionString(ctx)
+	require.NoError(t, err)
+	u, err := url.Parse(uri)
+	require.NoError(t, err)
+	q := u.Query()
+	q.Set("directConnection", "true")
+	// The handoff store must override unsafe caller defaults before claiming
+	// ownership of a non-idempotent external operation.
+	q.Set("w", "0")
+	q.Set("readPreference", "secondary")
+	u.RawQuery = q.Encode()
+	factory, err := db.NewConnection(zap.NewNop(), &db.Config{Driver: db.Mongo, Settings: sharedmodel.SettingsT{"uri": u.String(), "database": "facts"}})
+	require.NoError(t, err)
+	t.Cleanup(factory.CloseConnection)
+	store, err := OpenStore(factory)
+	require.NoError(t, err)
+	b := &Binding{Namespace: "configured-source", Facts: Facts{FullName: "Ada", Email: "ada@example.com"}}
+	b.SetID(bson.NewObjectID())
+	require.NoError(t, store.Create(ctx, b))
+	require.ErrorIs(t, store.Create(ctx, b), merrors.ErrDataConflict)
+	var wg sync.WaitGroup
+	var wins atomic.Int32
+	for range 12 {
+		wg.Go(func() {
+			claimed, err := store.Claim(ctx, b.ID, b.Namespace)
+			require.NoError(t, err)
+			if claimed {
+				wins.Add(1)
+			}
+		})
+	}
+	wg.Wait()
+	require.EqualValues(t, 1, wins.Load())
+	stored, err := store.Get(ctx, b.ID)
+	require.NoError(t, err)
+	require.True(t, stored.Registering)
+	require.False(t, stored.RegisteringAt.IsZero())
+	require.Error(t, store.Bind(ctx, b.ID, "other-source", "subject"))
+	require.NoError(t, store.Bind(ctx, b.ID, b.Namespace, "subject"))
+	require.Error(t, store.Bind(ctx, b.ID, b.Namespace, "different-subject"))
+	receipt := Receipt{SubjectRef: "other-subject", SubmissionRef: "submission", AcceptedAt: time.Now().UTC().Truncate(time.Millisecond)}
+	require.Error(t, store.Accept(ctx, b.ID, b.Namespace, receipt))
+	receipt.SubjectRef = "subject"
+	require.NoError(t, store.Accept(ctx, b.ID, b.Namespace, receipt))
+	// A separately opened store sees the durable receipt and cannot reclaim registration.
+	reopened, err := OpenStore(factory)
+	require.NoError(t, err)
+	stored, err = reopened.Get(ctx, b.ID)
+	require.NoError(t, err)
+	require.Equal(t, receipt, *stored.Receipt)
+	claimed, err := reopened.Claim(ctx, b.ID, b.Namespace)
+	require.NoError(t, err)
+	require.False(t, claimed)
+	_, err = reopened.Get(ctx, bson.NewObjectID())
+	require.ErrorIs(t, err, merrors.ErrNoData)
+}

backend/product/providers/sendico/client.go

@@ -0,0 +1,69 @@
+package sendico
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"io"
+	"net/http"
+
+	"git.sendico.io/tech/sxchnge/product/identity"
+	merrors "git.sendico.io/tech/sxchnge/shared/errors"
+	"go.mongodb.org/mongo-driver/v2/bson"
+)
+
+func (c *Client) post(ctx context.Context, resource, requestRef string, payload any) (receiptDTO, error) {
+	var receipt receiptDTO
+	token, err := c.token()
+	if err != nil {
+		return receipt, err
+	}
+	var body []byte
+	if payload != nil {
+		body, err = json.Marshal(payload)
+		if err != nil {
+			return receipt, merrors.OpaqueWrap(merrors.ErrServiceUnavailable, err, "encode Sendico request")
+		}
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.base+"/"+resource+"/"+c.config.OrganizationID, bytes.NewReader(body))
+	if err != nil {
+		return receipt, merrors.OpaqueWrap(merrors.ErrServiceUnavailable, err, "create Sendico request")
+	}
+	req.Header.Set("Authorization", "Bearer "+token)
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("X-Request-ID", requestRef)
+	response, err := c.http.Do(req)
+	if err != nil {
+		return receipt, merrors.OpaqueWrap(merrors.ErrServiceUnavailable, err, "Sendico request failed")
+	}
+	defer func() { _ = response.Body.Close() }()
+	// Never decode or expose upstream error bodies, which can contain assertions.
+	if response.StatusCode != http.StatusOK {
+		return receipt, merrors.ServiceUnavailable("Sendico request was not accepted")
+	}
+	decoder := json.NewDecoder(io.LimitReader(response.Body, 16385))
+	var envelope envelopeDTO
+	if err := decoder.Decode(&envelope); err != nil {
+		return receipt, merrors.OpaqueWrap(merrors.ErrServiceUnavailable, err, "decode Sendico receipt")
+	}
+	var trailing any
+	if decoder.Decode(&trailing) != io.EOF || envelope.Status != "success" {
+		return receipt, merrors.ServiceUnavailable("invalid Sendico response")
+	}
+	return envelope.Data, nil
+}
+
+func (c *Client) Register(ctx context.Context, requestRef string) (string, error) {
+	dto, err := c.post(ctx, "individuals", requestRef, nil)
+	if err != nil {
+		return "", err
+	}
+	return mapSubject(dto)
+}
+func (c *Client) Submit(ctx context.Context, subject, source string, facts identity.Facts) (identity.Receipt, error) {
+	dto, err := c.post(ctx, "identity_facts", bson.NewObjectID().Hex(), mapFacts(subject, source, facts))
+	if err != nil {
+		return identity.Receipt{}, err
+	}
+	return mapReceipt(dto, subject)
+}

backend/product/providers/sendico/client_test.go

@@ -0,0 +1,155 @@
+package sendico
+
+import (
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"git.sendico.io/tech/sxchnge/product/identity"
+	"github.com/stretchr/testify/require"
+)
+
+const org = "507f1f77bcf86cd799439011"
+const source = "507f1f77bcf86cd799439012"
+const subject = "507f1f77bcf86cd799439013"
+const submission = "507f1f77bcf86cd799439014"
+
+func credential(t *testing.T, id string, expiry int64) string {
+	t.Helper()
+	raw, err := json.Marshal(map[string]any{"id": id, "exp": expiry})
+	require.NoError(t, err)
+	return "header." + base64.RawURLEncoding.EncodeToString(raw) + ".signature"
+}
+func config(t *testing.T, endpoint string) Config {
+	t.Helper()
+	file := filepath.Join(t.TempDir(), "token")
+	require.NoError(t, os.WriteFile(file, []byte(credential(t, source, time.Now().Add(time.Hour).Unix())), 0600))
+	return Config{APIURL: endpoint + "/api/v1", OrganizationID: org, SourceID: source, TokenFile: file}
+}
+
+func TestSignupWireContractAndCredentialRotation(t *testing.T) {
+	paths := []string{}
+	var token string
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		require.Equal(t, http.MethodPost, r.Method)
+		require.Equal(t, "Bearer "+token, r.Header.Get("Authorization"))
+		paths = append(paths, r.URL.Path)
+		body, err := io.ReadAll(r.Body)
+		require.NoError(t, err)
+		if strings.Contains(r.URL.Path, "/individuals/") {
+			require.Equal(t, "registration-request", r.Header.Get("X-Request-ID"))
+			require.Empty(t, body)
+			_, _ = fmt.Fprintf(w, `{"status":"success","data":{"subject_ref":%q,"registered_at":"2026-10-07T10:30:00.123Z"}}`, subject)
+		} else {
+			require.JSONEq(t, `{"subject_ref":"`+subject+`","source_submission_ref":"signup-1","facts":{"full_name":"Ada Lovelace","email":"ada@example.com","external_customer_ref":"local-user"}}`, string(body))
+			_, _ = fmt.Fprintf(w, `{"status":"success","data":{"subject_ref":%q,"submission_ref":%q,"accepted_at":"2026-10-07T10:30:00.123Z"}}`, subject, submission)
+		}
+	}))
+	defer server.Close()
+	cfg := config(t, server.URL)
+	token = credential(t, source, time.Now().Add(time.Hour).Unix())
+	client, err := Open(cfg)
+	require.NoError(t, err)
+	ref, err := client.Register(context.Background(), "registration-request")
+	require.NoError(t, err)
+	require.Equal(t, subject, ref)
+	// File rotation takes effect without restarting; account identity stays fixed.
+	token = credential(t, source, time.Now().Add(2*time.Hour).Unix())
+	require.NoError(t, os.WriteFile(cfg.TokenFile, []byte(token), 0600))
+	receipt, err := client.Submit(context.Background(), subject, "signup-1", identity.Facts{FullName: "Ada Lovelace", Email: "ada@example.com", CustomerRef: "local-user"})
+	require.NoError(t, err)
+	require.Equal(t, submission, receipt.SubmissionRef)
+	require.Equal(t, subject, receipt.SubjectRef)
+	require.Equal(t, []string{"/api/v1/individuals/" + org, "/api/v1/identity_facts/" + org}, paths)
+	require.NoError(t, os.WriteFile(cfg.TokenFile, []byte(credential(t, org, time.Now().Add(time.Hour).Unix())), 0600))
+	_, err = client.Register(context.Background(), "registration-request")
+	require.Error(t, err)
+	require.Len(t, paths, 2)
+}
+
+func TestRejectInvalidConfiguration(t *testing.T) {
+	for _, endpoint := range []string{"http://remote.example", "https://user:pass@api.example", "https://api.example?secret=x", "https://api.example/#fragment", "//api.example", "ftp://localhost"} {
+		_, err := Open(config(t, endpoint))
+		require.Error(t, err, endpoint)
+	}
+	cfg := config(t, "https://api.example")
+	cfg.OrganizationID = "../other"
+	_, err := Open(cfg)
+	require.Error(t, err)
+	cfg = config(t, "https://api.example")
+	cfg.SourceID = ""
+	_, err = Open(cfg)
+	require.Error(t, err)
+	cfg = config(t, "https://api.example")
+	require.NoError(t, os.WriteFile(cfg.TokenFile, []byte(credential(t, source, 1)), 0600))
+	_, err = Open(cfg)
+	require.Error(t, err)
+}
+
+func TestUpstreamFailuresNeverProduceReceiptsOrLeakBodies(t *testing.T) {
+	for _, tc := range []struct {
+		name   string
+		status int
+		body   string
+	}{
+		{"denied", 403, `{"secret":"private-assertion"}`},
+		{"conflict", 409, `{"secret":"private-assertion"}`},
+		{"unavailable", 503, `{"secret":"private-assertion"}`},
+		{"malformed", 200, `{"private-assertion":`},
+		{"empty", 200, `{"status":"success","data":{}}`},
+		{"wrong-status", 200, `{"status":"error","data":{}}`},
+		{"oversized", 200, `{"padding":"` + strings.Repeat("x", 17000) + `"}`},
+		{"wrong-subject", 200, `{"status":"success","data":{"subject_ref":"` + org + `","submission_ref":"` + submission + `","accepted_at":"2026-10-07T10:30:00Z"}}`},
+		{"trailing", 200, `{"status":"success","data":{}} {}`},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.WriteHeader(tc.status)
+				_, _ = io.WriteString(w, tc.body)
+			}))
+			defer server.Close()
+			client, err := Open(config(t, server.URL))
+			require.NoError(t, err)
+			_, err = client.Submit(context.Background(), subject, "key", identity.Facts{})
+			require.Error(t, err)
+			require.NotContains(t, err.Error(), "private-assertion")
+			_, err = client.Register(context.Background(), "registration-request")
+			require.Error(t, err)
+		})
+	}
+}
+
+func TestRedirectAndTimeoutDoNotRepeatRegistration(t *testing.T) {
+	var calls int
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		calls++
+		http.Redirect(w, r, "/redirected", http.StatusTemporaryRedirect)
+	}))
+	defer server.Close()
+	client, err := Open(config(t, server.URL))
+	require.NoError(t, err)
+	_, err = client.Register(context.Background(), "registration-request")
+	require.Error(t, err)
+	require.Equal(t, 1, calls)
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	_, err = client.Register(ctx, "registration-request")
+	require.Error(t, err)
+	require.Equal(t, 1, calls)
+	timeoutServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { <-r.Context().Done() }))
+	defer timeoutServer.Close()
+	client, err = Open(config(t, timeoutServer.URL))
+	require.NoError(t, err)
+	client.http.Timeout = 20 * time.Millisecond
+	_, err = client.Register(context.Background(), "timeout-request")
+	require.Error(t, err)
+}

backend/product/providers/sendico/config.go

@@ -0,0 +1,87 @@
+// Package sendico consumes only Sendico's public HTTP contracts.
+package sendico
+
+import (
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/hex"
+	"encoding/json"
+	"net/http"
+	"net/url"
+	"os"
+	"strings"
+	"time"
+
+	merrors "git.sendico.io/tech/sxchnge/shared/errors"
+	"go.mongodb.org/mongo-driver/v2/bson"
+)
+
+type Config struct {
+	APIURL         string `yaml:"api_url"`
+	OrganizationID string `yaml:"organization_ref"`
+	SourceID       string `yaml:"source_account_ref"`
+	TokenFile      string `yaml:"token_file"`
+}
+
+type Client struct {
+	config    Config
+	base      string
+	namespace string
+	http      *http.Client
+}
+
+func Open(c Config) (*Client, error) {
+	u, err := url.Parse(c.APIURL)
+	if err != nil || u.Host == "" || u.User != nil || u.RawQuery != "" || u.Fragment != "" || u.RawPath != "" || (u.Scheme != "https" && !(u.Scheme == "http" && (u.Hostname() == "localhost" || u.Hostname() == "127.0.0.1"))) {
+		return nil, merrors.InvalidArgument("Sendico API URL must be absolute HTTPS (HTTP allowed on localhost)")
+	}
+	for _, ref := range []string{c.OrganizationID, c.SourceID} {
+		id, err := bson.ObjectIDFromHex(ref)
+		if err != nil || id.IsZero() || ref != id.Hex() {
+			return nil, merrors.InvalidArgument("Sendico organization and source references must be lowercase object IDs")
+		}
+	}
+	if strings.TrimSpace(c.TokenFile) == "" {
+		return nil, merrors.InvalidArgument("Sendico token file required")
+	}
+	base := strings.TrimRight(c.APIURL, "/")
+	hash := sha256.Sum256([]byte(base + "\x00" + c.OrganizationID + "\x00" + c.SourceID))
+	client := &Client{config: c, base: base, namespace: hex.EncodeToString(hash[:]), http: &http.Client{Timeout: 4 * time.Second, CheckRedirect: func(*http.Request, []*http.Request) error { return http.ErrUseLastResponse }}}
+	if _, err := client.token(); err != nil {
+		return nil, err
+	}
+	return client, nil
+}
+
+func (c *Client) Namespace() string { return c.namespace }
+
+// Rotation may replace this file, but must retain the authenticated account.
+// Claim inspection only protects the replay namespace from operator mistakes;
+// Sendico remains responsible for signature validation and authorization.
+func (c *Client) token() (string, error) {
+	raw, err := os.ReadFile(c.config.TokenFile)
+	if err != nil {
+		return "", merrors.OpaqueWrap(merrors.ErrServiceUnavailable, err, "read Sendico credential")
+	}
+	token := strings.TrimSpace(string(raw))
+	parts := strings.Split(token, ".")
+	if len(token) > 16384 || len(parts) != 3 {
+		return "", merrors.FailedPrecondition("invalid Sendico credential")
+	}
+	claims, err := base64.RawURLEncoding.DecodeString(parts[1])
+	if err != nil {
+		return "", merrors.OpaqueWrap(merrors.ErrFailedPrecondition, err, "invalid Sendico credential claims")
+	}
+	var payload struct {
+		ID      string `json:"id"`
+		Pending bool   `json:"pending"`
+		Exp     int64  `json:"exp"`
+	}
+	if err := json.Unmarshal(claims, &payload); err != nil {
+		return "", merrors.OpaqueWrap(merrors.ErrFailedPrecondition, err, "invalid Sendico credential claims")
+	}
+	if payload.ID != c.config.SourceID || payload.Pending || payload.Exp <= time.Now().Unix() {
+		return "", merrors.FailedPrecondition("Sendico credential must be unexpired and match configured source account")
+	}
+	return token, nil
+}

backend/product/providers/sendico/dto.go

@@ -0,0 +1,51 @@
+package sendico
+
+import (
+	"time"
+
+	"git.sendico.io/tech/sxchnge/product/identity"
+	merrors "git.sendico.io/tech/sxchnge/shared/errors"
+	"go.mongodb.org/mongo-driver/v2/bson"
+)
+
+// Only consumed wire fields are owned here; never import platform modules.
+type factsDTO struct {
+	FullName    string `json:"full_name"`
+	Email       string `json:"email"`
+	CustomerRef string `json:"external_customer_ref"`
+}
+type submissionDTO struct {
+	SubjectRef string   `json:"subject_ref"`
+	SourceRef  string   `json:"source_submission_ref"`
+	Facts      factsDTO `json:"facts"`
+}
+type receiptDTO struct {
+	SubjectRef    string    `json:"subject_ref"`
+	RegisteredAt  time.Time `json:"registered_at"`
+	SubmissionRef string    `json:"submission_ref"`
+	AcceptedAt    time.Time `json:"accepted_at"`
+}
+type envelopeDTO struct {
+	Status string     `json:"status"`
+	Data   receiptDTO `json:"data"`
+}
+
+func validRef(ref string) bool {
+	id, err := bson.ObjectIDFromHex(ref)
+	return err == nil && !id.IsZero() && id.Hex() == ref
+}
+func mapFacts(subject, source string, facts identity.Facts) submissionDTO {
+	return submissionDTO{SubjectRef: subject, SourceRef: source, Facts: factsDTO{FullName: facts.FullName, Email: facts.Email, CustomerRef: facts.CustomerRef}}
+}
+func mapSubject(dto receiptDTO) (string, error) {
+	if !validRef(dto.SubjectRef) || dto.RegisteredAt.IsZero() {
+		return "", merrors.ServiceUnavailable("invalid Sendico registration receipt")
+	}
+	return dto.SubjectRef, nil
+}
+func mapReceipt(dto receiptDTO, subject string) (identity.Receipt, error) {
+	if !validRef(dto.SubmissionRef) || dto.SubjectRef != subject || dto.AcceptedAt.IsZero() {
+		return identity.Receipt{}, merrors.ServiceUnavailable("invalid Sendico intake receipt")
+	}
+	return identity.Receipt{SubmissionRef: dto.SubmissionRef, SubjectRef: dto.SubjectRef, AcceptedAt: dto.AcceptedAt}, nil
+}

backend/shared/database/source/majority.go

@@ -0,0 +1,25 @@
+package source
+
+import (
+	"context"
+
+	"go.mongodb.org/mongo-driver/v2/mongo"
+	"go.mongodb.org/mongo-driver/v2/mongo/options"
+	"go.mongodb.org/mongo-driver/v2/mongo/readconcern"
+	"go.mongodb.org/mongo-driver/v2/mongo/readpref"
+	"go.mongodb.org/mongo-driver/v2/mongo/writeconcern"
+)
+
+type majority struct{ Source }
+
+// Majority retains the source's lease and transaction lifecycle while requiring
+// durable writes and primary majority reads for externally visible handoffs.
+func Majority(database Source) Source { return &majority{Source: database} }
+
+func (s *majority) Acquire(ctx context.Context) (*mongo.Database, context.Context, func(), error) {
+	database, scoped, release, err := s.Source.Acquire(ctx)
+	if err != nil {
+		return nil, scoped, release, err
+	}
+	return database.Client().Database(database.Name(), options.Database().SetWriteConcern(writeconcern.Majority()).SetReadConcern(readconcern.Majority()).SetReadPreference(readpref.Primary())), scoped, release, nil
+}

backend/shared/database/source/majority_test.go

@@ -0,0 +1,40 @@
+package source
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"go.mongodb.org/mongo-driver/v2/mongo"
+	"go.mongodb.org/mongo-driver/v2/mongo/options"
+	"go.mongodb.org/mongo-driver/v2/mongo/readpref"
+	"go.mongodb.org/mongo-driver/v2/mongo/writeconcern"
+)
+
+type trackedSource struct {
+	database *mongo.Database
+	released bool
+}
+
+func (s *trackedSource) Acquire(ctx context.Context) (*mongo.Database, context.Context, func(), error) {
+	return s.database, ctx, func() { s.released = true }, nil
+}
+
+func TestMajorityPreservesSourceLifetime(t *testing.T) {
+	client, err := mongo.Connect(options.Client().ApplyURI("mongodb://localhost:27017").SetWriteConcern(&writeconcern.WriteConcern{W: 1}).SetReadPreference(readpref.Secondary()))
+	require.NoError(t, err)
+	t.Cleanup(func() { require.NoError(t, client.Disconnect(context.Background())) })
+	underlying := &trackedSource{database: client.Database("handoff")}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	database, scoped, release, err := Majority(underlying).Acquire(ctx)
+	require.NoError(t, err)
+	require.Same(t, client, database.Client())
+	require.Equal(t, "handoff", database.Name())
+	require.Equal(t, ctx, scoped)
+	require.False(t, underlying.released)
+	release()
+	require.True(t, underlying.released)
+	_, _, _, err = Majority(Fixed(nil)).Acquire(ctx)
+	require.Error(t, err)
+}

docs/auth-notifications.md

@@ -61,7 +61,7 @@ envelope. Credentials, codes and activation tokens are sent in POST bodies.
 
 | Route | Request | Successful result |
 | --- | --- | --- |
-| POST `/signup` | `name`, `email`, `password`, `locale`, `idempotencyKey` | 202 with `userId`, after activation email queue acceptance |
+| POST `/signup` | `name`, `email`, `password`, `locale`, `idempotencyKey` | 202 with `userId`, after configured Facts intake and activation email queue acceptance |
 | POST `/verification/send` | `email`, `idempotencyKey` | 202; generic acceptance also applies to absent/already-active accounts |
 | POST `/verification/confirm` | `token` | 202 with `verified: true` after activation commits |
 | POST `/login` | `login: {login, password}`, `clientId`, `deviceId` | 202 with `userId`, `pendingToken: {token, expiration}`, `challengeId`, `channel`, masked `target`, `expiresAt`, `resendAt` |
@@ -101,6 +101,14 @@ retries can create replacement messages; they are not distributed exactly-once
 operations. Tokens are stored before the RPC, so a process crash between those
 steps requires user recovery; there is no product-side delivery outbox.
 
+When `api.sendico` is enabled, sign-up and activation resend first require a
+durable Facts intake receipt. Activation checks that receipt in its transaction.
+Initial account/token creation uses the same server-secret-derived activation
+key as a same-key retry, so an intake outage does not force an extra cooldown for
+an unsent initial token. Existing pending customers created before this change
+retain the prior cooldown behavior. See [Facts integration](signup-facts.md) for
+uncertain registration recovery and the `signup_attention_required` error.
+
 Code verification, one-use proof consumption and session creation now commit in
 one transaction. A session-write failure leaves the code retryable; a lost HTTP
 response after commit requires restarting password login. The adapter

docs/implementation.md

@@ -828,3 +828,55 @@ existing mount requires reauthentication at its new cookie path. Notification
 activation URLs remain configured frontend URLs. No live deployment, optional
 security scans or merge were performed. The unrelated local notifications sender
 configuration remains uncommitted. See [API version installation](api-versions.md).
+
+## Sign-up Facts intake — task #46
+
+[Task #46](https://git.sendico.io/tech/sxchnge/issues/46), branch
+`identity-facts-46`, connects the product sign-up service to Sendico's public
+individual registry and immutable Facts intake through optional `api.sendico`
+configuration. Owner: `tech`; project: SXCHNGE; labels: backend and frontend.
+
+The adapter sends full name, normalized email and the local customer reference.
+The BFF persists a customer-owned subject binding, immutable facts snapshot and
+confirmed receipt before activation email or sign-up acceptance. Activation and
+resend enforce the handoff. The shared database source can require majority
+writes and primary majority reads without bypassing its connection/transaction
+lifecycle. Initial account/token creation remains atomic and uses a secret-derived
+activation key, allowing same-key recovery after an intake outage without an
+extra cooldown for an unsent token. Archived customers cannot resume sign-up.
+
+Backend and frontend completion reviews covered the full task contribution,
+including the public contracts, customer ownership, stable replay namespace,
+concurrent claims, error classification, credential handling, logging, metrics and
+DTO/mapper/service/model/provider separation. UX review preserved input, loading
+suppression and confirmation-based success. Typed support guidance reaches both
+sign-up and verification resend/confirmation through the shared auth package;
+EN/RU feedback preserves live-region semantics and existing responsive controls.
+The new localized widget fixture initially double-disposed the app-owned locale
+provider; the fixture ownership was corrected. Focused integration tests also
+exposed the initial-token cooldown issue, which was fixed in the creation flow.
+
+Individual registration is not idempotent upstream. A durable claim prevents
+speculative repeat registration after an ambiguous result; reconciliation uses
+the saved request reference and authoritative Sendico records. Intake replay is
+safe after receipt loss and retains original assertions. Actual provider IDs,
+the endpoint and a same-account Vault-rendered access token must be provisioned
+before enabling this integration. Tests use simulated HTTP and disposable MongoDB;
+no live provider resources, live email, deployment, merge or optional security
+scan is part of this delivery. The unrelated notifications runtime configuration
+is excluded. Configuration, rollout, telemetry and recovery details are in
+[Sign-up Facts intake](signup-facts.md).
+
+Final validation passed: `GOFLAGS=-p=2 make test` (all backend race tests and
+`make test-frontend` suites), `make lint-backend`,
+`dart format --output=none --set-exit-if-changed` for all 11 changed Dart files,
+and `flutter analyze` in `frontend/app` and `frontend/packages/sxchnge_auth`.
+Focused Go race suites and Flutter backend/provider/widget tests also passed;
+the diagnostic public API run
+`go -C backend/product test -race -v ./auth/http/v1/public -count=1 -timeout=90s`
+passed. The initial unrestricted `make test` failed when Testcontainers could
+not start its reaper before the Mongo fixture deadline. Lower Go package
+parallelism resolved that infrastructure contention. The next full run exposed
+the new locale fixture disposal error noted above; the corrected final run
+passed, including EN/RU support states and verification recovery. No checks were
+weakened or unrelated work changed.

docs/signup-facts.md

@@ -0,0 +1,176 @@
+# Sign-up Facts intake
+
+Task [#46](https://git.sendico.io/tech/sxchnge/issues/46), branch
+`identity-facts-46`. Primary module: identity-facts; secondary modules: auth,
+customer creation, runtime, shared database source and Flutter error feedback.
+
+## Behavior and boundaries
+
+With `api.sendico` configured, the product BFF creates the local pending customer
+and activation token atomically, then registers an independent individual through
+Sendico's public HTTP API and submits the sign-up assertions. It persists the
+intake receipt before sending activation email or returning sign-up success.
+Activation resend runs the same handoff; activation checks the receipt in its
+local transaction, without external I/O. A failed receipt check rolls back token
+consumption and leaves the account pending. Existing active customers are not
+backfilled or blocked at login.
+
+The adapter consumes these existing Sendico contracts:
+
+- `POST /individuals/{organization_ref}`, empty body, HTTP 200 registration
+  receipt containing `subject_ref` and `registered_at`.
+- `POST /identity_facts/{organization_ref}`, HTTP 200 immutable intake receipt
+  containing `submission_ref`, `subject_ref` and `accepted_at`.
+
+The configured API prefix precedes both paths. See Sendico
+[individual subjects](https://git.sendico.io/tech/sendico/src/branch/main/docs/api/individual-subjects.md)
+and [Facts intake](https://git.sendico.io/tech/sendico/src/branch/main/docs/api/identity-facts-intake.md).
+The only assertions sent are `full_name`, normalized `email` and
+`external_customer_ref` (the local customer ID). Passwords, password hashes,
+activation tokens, session credentials and device data never enter the adapter.
+The input name is retained as a full name, without guessing name parts. No facts
+are marked verified; acceptance does not establish identity, KYC completeness,
+verification, limits or payout eligibility. The existing KYC preview is unchanged.
+
+Only the BFF owns Sendico credentials and organization scope. Local customer
+models have no organization, membership or platform permissions. HTTP DTOs and
+mappers stay in `providers/sendico`; the handoff operates on domain facts and
+receipts in `identity`. Flutter continues through its DTO, mapper, service,
+model and provider layers. It never calls Sendico or supplies subject references.
+
+## Configuration and rollout
+
+Add this block under `api` in the product service configuration, retaining
+`api.notifications`:
+
+```yaml
+sendico:
+  api_url: https://your-sendico-host/api/v1
+  organization_ref: <provisioned-SXCHNGE-organization-object-id>
+  source_account_ref: <provisioned-integration-account-object-id>
+  token_file: /run/sxchnge/sendico-token
+```
+
+Resolve the real IDs from the target Sendico deployment. The integration account
+must be a member of the SXCHNGE organization with the existing organizations
+`update` permission; reconciliation GET requests also require `read`. The token
+must be a full, unexpired Sendico access JWT whose `id` claim is that account.
+The adapter inspects claims only to protect the replay namespace; Sendico checks
+the signature and authorizes every call. No login, refresh or privileged account
+provisioning is performed by this adapter.
+
+Keep the token in Vault at `services/bff/sendico`, field `access_token`. Render it
+with the deployment's Vault Agent into the configured private runtime file; give
+only the BFF policy read access to that KV path. Endpoint, organization and source
+IDs remain in service YAML. For the local stack, configure
+`infra/local/bff/runtime.yml`, render to the BFF's existing `/run/sxchnge` tmpfs,
+and extend its Vault Agent policy/template for this provisioned secret. These
+deployment values and secret provisioning are deliberately not guessed or
+enabled by the example. Do not place tokens in Git, browser builds or shell
+history. Refresh the file atomically before expiry using the same Sendico account;
+the adapter rereads it on every request. Startup rejects missing, expired or
+mismatched credentials and rejects Sendico configuration without notifications.
+
+HTTPS is required except for loopback HTTP test/development endpoints. Redirects
+are rejected and each HTTP call has a four-second timeout. Non-200 responses,
+malformed/truncated receipts, invalid identifiers, wrong subjects and unsuccessful
+envelopes never count as acceptance. Upstream error bodies are not surfaced.
+
+Omitting `api.sendico` keeps existing local-only behavior. Enabling it also gates
+activation for previously pending customers; use activation resend to submit
+their saved name/email before confirming their old link. There is no automatic
+bulk migration. Changing endpoint, organization or source account changes the
+adapter fingerprint and blocks existing bindings for explicit reconciliation.
+Token rotation for the same account retains that fingerprint. Plan such changes
+as migrations; never reset a binding just to bypass the check.
+
+## Persistence, retries and recovery
+
+The local `signup_facts` collection uses the customer ID as `_id`, so its unique
+primary key coordinates concurrent requests and separate BFF instances. It stores
+an immutable sign-up facts snapshot, adapter fingerprint, random registration
+request correlation, registration claim, subject and confirmed receipt. It uses
+the shared database repository and connection lifecycle with majority writes and
+primary majority reads, overriding weaker connection defaults. No external call
+runs in a database transaction. Snapshots and bindings contain personal data and
+must follow the customer data retention policy; no TTL silently removes replay
+state, and customer deletion does not delete the immutable Sendico submission.
+
+Once a subject is stored, intake retries use
+`sxchnge:signup:<local-customer-id>` as `source_submission_ref`. Sendico's
+organization/authenticated-account/source-reference uniqueness returns the
+original receipt for that subject. Retries send the saved snapshot even if a
+later request changes name or email. Losing the HTTP receipt or a local receipt
+write is recoverable by replay. A saved receipt skips subsequent external calls.
+Retrying sign-up still requires the original password; active, archived or
+otherwise conflicting accounts cannot be resumed as a new customer.
+
+**Individual registration is not idempotent.** The BFF commits a claim before
+dispatch and never expires or automatically retries that registration. It cannot
+prove that a timed-out request, malformed response or failed local binding write
+did not create a subject. Another request sees an in-progress claim as temporarily
+unavailable for 30 seconds; an older unresolved claim requires support. The
+registration caller immediately reports assistance on an uncertain failure. An
+accepted registration is saved with a short independent context even if the
+browser disconnects. A crash before dispatch can also require reconciliation.
+This trades automatic recovery for avoiding duplicate subjects under the current
+upstream contract; there is no distributed exactly-once guarantee.
+
+For an unresolved registration, operators must stop requests for the affected
+customer and inspect the saved `registrationRequest` plus Sendico identity logs
+(`X-Request-ID`, operation `subject_register`) under the configured account and
+organization. A successful registration's server-issued `record_ref` identifies
+the candidate subject. Confirm it using the organization-scoped individual GET
+API before atomically setting the matching local binding's `subjectRef` and
+clearing `registering`; retain its snapshot, fingerprint and request reference.
+If a local binding write failed after receipt, BFF diagnostics also contain the
+subject reference. If authoritative records prove no subject was created, an
+operator may clear the claim after fixing the dependency. If neither result can
+be established, leave it blocked; never register a speculative replacement.
+Resume sign-up with the original credentials or activation resend after this
+repair. These are controlled operational repairs, not customer API endpoints.
+
+HTTP 503 `signup_attention_required` maps to typed shared auth and verification
+state and localized EN/RU support guidance, including activation resend recovery.
+Other intake/receipt failures remain temporary service
+failures. Form input is retained, duplicate submissions stay disabled during
+loading, and neither failure navigates to an email-sent screen or creates a
+session. The existing support channel must be available to handle reconciliation.
+
+## Measurement and UX review
+
+The existing [auth journey](ux/auth-journeys.md) keeps its attempt, retry,
+abandonment and 30-minute settled inactivity rules. `auth_signup_succeeded` now
+requires server confirmation of configured intake plus activation queue acceptance;
+it remains an intermediate step and email confirmation remains the terminal
+onboarding outcome. Sign-up dependency failures and assistance outcomes use the
+existing allowlisted `unavailable` analytics category; verification assistance
+uses it too. Retries retain the journey
+and operation semantics. No names, emails or provider response bodies are added.
+
+`sxchnge_signup_facts_total{outcome}` records `accepted`, `replayed`,
+`unavailable` and `attention_required` handoff attempts;
+`sxchnge_signup_facts_duration_seconds` measures their latency. Counts are
+attempts, not distinct users. Use unavailable/attention counts divided by total
+handoff attempts for operational failure rates; use the existing correlated auth
+journey for conversion, duration and abandonment. Structured handoff logs include
+local customer and random registration request references for support correlation,
+without asserted values, credentials or raw errors. IDs are never metric labels.
+The product team uses the distinction to separate retryable intake outages from
+registration reconciliation. The default client analytics sink remains in memory;
+production retention and cross-device conversion correlation remain deployment
+gaps, as documented by the existing journey contract.
+
+Review covers loading suppression, input preservation, success only on confirmed
+handoff, temporary retry and assistance states, existing navigation, mobile layout,
+text scaling and live-region error feedback. Focused tests cover these states,
+the mapped backend error, non-inflated client success, immutable retry payloads,
+credential rotation, timeout/cancellation/redirect behavior, receipt validation,
+privacy-safe errors, concurrent durable claims and activation rollback. The tests
+use disposable local MongoDB and a simulated Sendico HTTP server; they do not
+create live subjects or send email. Live integration and support operations must
+be verified against provisioned deployment credentials before enabling the block.
+The EN/RU error state is exercised at a 390px viewport with 1.5x text scaling;
+existing keyboard regression tests and a code review of the live-region semantics
+cover the unchanged controls. No manual browser or screen-reader walkthrough
+against a live Sendico deployment was performed.

frontend/app/lib/auth/feedback.dart

@@ -22,6 +22,7 @@ class AuthFeedback extends StatelessWidget {
             AuthError.accountNotVerified => l.authVerifyEmail,
             AuthError.invalidCredentials => l.authInvalidCredentials,
             AuthError.emailInUse => l.authEmailInUse,
+            AuthError.signupNeedsAssistance => l.authSignupNeedsAssistance,
             AuthError.unavailable => l.authUnavailable,
             AuthError.unexpected => l.authUnexpected,
             AuthError.factorLocked => l.factorLocked,

frontend/app/lib/l10n/en.arb

@@ -1,5 +1,6 @@
 {
   "@@locale": "en",
+  "authSignupNeedsAssistance": "We could not finish setting up your account. Please contact support.",
   "appTitle": "SXCHNGE · Your next move",
   "nextChapter": "YOUR NEXT CHAPTER",
   "loginHeading": "Hey, welcome\nback.",

frontend/app/lib/l10n/ru.arb

@@ -1,5 +1,6 @@
 {
   "@@locale": "ru",
+  "authSignupNeedsAssistance": "Не удалось завершить создание аккаунта. Обратитесь в службу поддержки.",
   "appTitle": "SXCHNGE · Ваш следующий шаг",
   "nextChapter": "НОВАЯ ГЛАВА",
   "loginHeading": "Рады видеть\nвас снова.",

frontend/app/lib/verification/page.dart

@@ -122,8 +122,10 @@ class _VerificationPageState extends State<VerificationPage> {
               (_provider.service as SimulationInfo).isSimulated) ||
           state.isSimulated;
       final sent = status == VerificationStatus.sent;
+      final needsAssistance = state.error == VerificationError.needsAssistance;
       final retryConfirmation =
           status == VerificationStatus.error &&
+          !needsAssistance &&
           !_lastWasSend &&
           widget.token != null;
       final title = switch (status) {
@@ -139,14 +141,16 @@ class _VerificationPageState extends State<VerificationPage> {
               ? l.verificationChecking
               : l.verificationRequest,
       };
-      final body = switch (status) {
+      final body = needsAssistance
-        VerificationStatus.sent => l.verificationSent,
+          ? l.authSignupNeedsAssistance
-        VerificationStatus.verified => l.verificationVerifiedBody,
+          : switch (status) {
-        VerificationStatus.expired => l.verificationExpiredBody,
+              VerificationStatus.sent => l.verificationSent,
-        VerificationStatus.invalid => l.verificationInvalidBody,
+              VerificationStatus.verified => l.verificationVerifiedBody,
-        VerificationStatus.error => l.verificationInternalBody,
+              VerificationStatus.expired => l.verificationExpiredBody,
-        _ => null,
+              VerificationStatus.invalid => l.verificationInvalidBody,
-      };
+              VerificationStatus.error => l.verificationInternalBody,
+              _ => null,
+            };
       return Scaffold(
         body: SafeArea(
           child: SingleChildScrollView(

frontend/app/test/auth_services_test.dart

@@ -6,6 +6,8 @@ import 'package:flutter_test/flutter_test.dart';
 
 import 'package:go_router/go_router.dart';
 
+import 'package:sxchnge_analytics/sxchnge_analytics.dart';
+
 import 'package:sxchnge_auth/sxchnge_auth.dart';
 
 import 'package:sxchnge_app/main.dart';
@@ -41,6 +43,84 @@ class UnverifiedBackend extends BackendAuthServices {
 }
 
 void main() {
+  for (final language in ['en', 'ru']) {
+    testWidgets(
+      'signup requiring assistance preserves input and records failure ($language)',
+      (tester) async {
+        tester.view.physicalSize = const Size(390, 844);
+        tester.view.devicePixelRatio = 1;
+        tester.platformDispatcher.textScaleFactorTestValue = 1.5;
+        addTearDown(tester.view.resetPhysicalSize);
+        addTearDown(tester.view.resetDevicePixelRatio);
+        addTearDown(tester.platformDispatcher.clearTextScaleFactorTestValue);
+        final analytics = DummyAnalyticsService();
+        final locale = LocaleProvider(initialLocale: Locale(language));
+        await tester.pumpWidget(
+          SxchngeApp(
+            localeProvider: locale,
+            analyticsService: analytics,
+            signupService: const DummySignupService(
+              delay: Duration.zero,
+              failure: AuthError.signupNeedsAssistance,
+            ),
+          ),
+        );
+        await tester.pumpAndSettle();
+        final signupLabel = language == 'ru' ? 'Регистрация' : 'Sign up';
+        await tester.ensureVisible(find.text(signupLabel));
+        await tester.tap(find.text(signupLabel));
+        await tester.pumpAndSettle();
+        for (final entry in {
+          'name': 'Ada Lovelace',
+          'email': 'ada@example.com',
+          'password': 'password preserved',
+          'confirmation': 'password preserved',
+        }.entries) {
+          await tester.enterText(find.byKey(ValueKey(entry.key)), entry.value);
+        }
+        await tester.ensureVisible(find.byKey(const ValueKey('submit')));
+        await tester.tap(find.byKey(const ValueKey('submit')));
+        await tester.pumpAndSettle();
+        final feedback = find.byKey(const ValueKey('auth-error'));
+        await tester.ensureVisible(feedback);
+        expect(
+          find.text(
+            language == 'ru'
+                ? 'Не удалось завершить создание аккаунта. Обратитесь в службу поддержки.'
+                : 'We could not finish setting up your account. Please contact support.',
+          ),
+          findsOneWidget,
+        );
+        expect(find.byKey(const ValueKey('verification-sent')), findsNothing);
+        expect(
+          tester
+              .widget<TextFormField>(find.byKey(const ValueKey('email')))
+              .controller!
+              .text,
+          'ada@example.com',
+        );
+        expect(
+          tester
+              .widget<TextFormField>(find.byKey(const ValueKey('password')))
+              .controller!
+              .text,
+          'password preserved',
+        );
+        expect(
+          analytics.events.where((event) => event.name == 'auth_signup_failed'),
+          hasLength(1),
+        );
+        expect(
+          analytics.events.where(
+            (event) => event.name == 'auth_signup_succeeded',
+          ),
+          isEmpty,
+        );
+        expect(tester.takeException(), isNull);
+      },
+    );
+  }
+
   testWidgets('backend mode gates workspace and recovers unverified login', (
     tester,
   ) async {

frontend/app/test/verification_test.dart

@@ -42,6 +42,37 @@ Future<void> openVerification(
 }
 
 void main() {
+  testWidgets('resend assistance retains email and does not claim delivery', (
+    tester,
+  ) async {
+    await openVerification(
+      tester,
+      '/verification-sent',
+      service: const DummyVerificationService(
+        delay: Duration.zero,
+        sendFailure: VerificationError.needsAssistance,
+      ),
+    );
+    final email = find.byKey(const ValueKey('verification-email'));
+    await tester.enterText(email, 'ada@example.com');
+    await tester.ensureVisible(
+      find.byKey(const ValueKey('verification-resend')),
+    );
+    await tester.tap(find.byKey(const ValueKey('verification-resend')));
+    await tester.pumpAndSettle();
+    expect(
+      find.text(
+        'We could not finish setting up your account. Please contact support.',
+      ),
+      findsOneWidget,
+    );
+    expect(find.byKey(const ValueKey('verification-sent')), findsNothing);
+    expect(
+      tester.widget<TextFormField>(email).controller!.text,
+      'ada@example.com',
+    );
+    expect(tester.takeException(), isNull);
+  });
   for (final scenario in {
     'demo-valid': 'verified',
     'demo-expired': 'expired',

frontend/packages/sxchnge_auth/lib/src/mappers/backend.dart

@@ -2,6 +2,7 @@ import '../dto/backend.dart';
 import '../models/auth.dart';
 import '../models/session.dart';
 import '../models/two_factor.dart';
+import '../models/verification.dart';
 
 abstract final class BackendMapper {
   static AuthResult signup(BackendDTO dto) {
@@ -33,11 +34,19 @@ abstract final class BackendMapper {
   static AuthException authFailure(int status, BackendDTO dto) =>
       AuthException(switch (dto.error) {
         'email_in_use' => AuthError.emailInUse,
+        'signup_attention_required' => AuthError.signupNeedsAssistance,
         'account_not_verified' => AuthError.accountNotVerified,
         _ when status == 401 => AuthError.invalidCredentials,
         _ when status == 429 => AuthError.factorCooldown,
         _ => AuthError.unavailable,
       });
+  static VerificationException verificationFailure(BackendDTO dto) =>
+      VerificationException(switch (dto.error) {
+        'expired' => VerificationError.expired,
+        'invalid' => VerificationError.invalid,
+        'signup_attention_required' => VerificationError.needsAssistance,
+        _ => VerificationError.internal,
+      });
   static FactorException factorFailure(int status, BackendDTO dto) =>
       FactorException(switch (dto.error) {
         'expired' => FactorError.expired,

frontend/packages/sxchnge_auth/lib/src/models/auth.dart

@@ -41,6 +41,7 @@ enum AuthError {
   invalidCredentials,
   accountNotVerified,
   emailInUse,
+  signupNeedsAssistance,
   unavailable,
   unexpected,
   factorLocked,

frontend/packages/sxchnge_auth/lib/src/models/verification.dart

@@ -9,7 +9,7 @@ enum VerificationStatus {
   error,
 }
 
-enum VerificationError { expired, invalid, internal }
+enum VerificationError { expired, invalid, internal, needsAssistance }
 
 class VerificationException implements Exception {
   const VerificationException(this.code);
@@ -22,8 +22,9 @@ class VerificationResult {
 }
 
 class VerificationState {
-  const VerificationState(this.status, {this.isSimulated = false});
+  const VerificationState(this.status, {this.isSimulated = false, this.error});
   final VerificationStatus status;
+  final VerificationError? error;
   final bool isSimulated;
   bool get isLoading =>
       status == VerificationStatus.sending ||

frontend/packages/sxchnge_auth/lib/src/providers/verification.dart

@@ -49,7 +49,9 @@ class VerificationProvider extends ChangeNotifier {
                 VerificationError.expired => VerificationStatus.expired,
                 VerificationError.invalid => VerificationStatus.invalid,
                 VerificationError.internal => VerificationStatus.error,
+                VerificationError.needsAssistance => VerificationStatus.error,
               },
+        error: code,
       );
     }
     notifyListeners();

frontend/packages/sxchnge_auth/lib/src/services/backend.dart

@@ -63,6 +63,7 @@ class BackendAuthServices
     String path,
     Map<String, Object?> body, {
     bool factor = false,
+    bool verification = false,
   }) async {
     try {
       final uri = baseUri.replace(
@@ -81,6 +82,7 @@ class BackendAuthServices
           .timeout(const Duration(seconds: 15));
       final dto = BackendDTO.decode(res.body);
       if (res.statusCode < 200 || res.statusCode >= 300) {
+        if (verification) throw BackendMapper.verificationFailure(dto);
         throw factor
             ? BackendMapper.factorFailure(res.statusCode, dto)
             : BackendMapper.authFailure(res.statusCode, dto);
@@ -90,7 +92,11 @@ class BackendAuthServices
       rethrow;
     } on FactorException {
       rethrow;
+    } on VerificationException {
+      rethrow;
     } catch (_) {
+      if (verification)
+        throw const VerificationException(VerificationError.internal);
       if (factor) throw const FactorException(FactorError.unavailable);
       throw const AuthException(AuthError.unavailable);
     }
@@ -148,16 +154,17 @@ class BackendAuthServices
       await _post('verification/send', {
         'email': normalized,
         'idempotencyKey': key,
-      }, factor: true);
+      }, verification: true);
       _retryKeys.remove('activation:$normalized');
       return VerificationMapper.fromDTO(
         const VerificationDTO(simulated: false),
       );
-    } on FactorException catch (e) {
+    } on VerificationException catch (e) {
-      if (e.code == FactorError.expired || e.code == FactorError.invalid) {
+      if (e.code == VerificationError.expired ||
+          e.code == VerificationError.invalid) {
         _retryKeys.remove('activation:$normalized');
       }
-      throw const VerificationException(VerificationError.internal);
+      rethrow;
     } catch (_) {
       throw const VerificationException(VerificationError.internal);
     }
@@ -165,18 +172,8 @@ class BackendAuthServices
 
   @override
   Future<VerificationResult> confirm({required String token}) async {
-    try {
+    await _post('verification/confirm', {'token': token}, verification: true);
-      await _post('verification/confirm', {'token': token}, factor: true);
+    return VerificationMapper.fromDTO(const VerificationDTO(simulated: false));
-      return VerificationMapper.fromDTO(
-        const VerificationDTO(simulated: false),
-      );
-    } on FactorException catch (e) {
-      throw VerificationException(switch (e.code) {
-        FactorError.expired => VerificationError.expired,
-        FactorError.invalid => VerificationError.invalid,
-        _ => VerificationError.internal,
-      });
-    }
   }
 
   @override

frontend/packages/sxchnge_auth/lib/src/services/instrumented.dart

@@ -60,6 +60,7 @@ class InstrumentedAuthServices
           AuthError.invalidCredentials => JourneyFailure.invalidCredentials,
           AuthError.emailInUse => JourneyFailure.emailInUse,
           AuthError.unavailable => JourneyFailure.unavailable,
+          AuthError.signupNeedsAssistance => JourneyFailure.unavailable,
           AuthError.unexpected => JourneyFailure.unexpected,
           AuthError.factorLocked ||
           AuthError.factorCooldown => JourneyFailure.unavailable,
@@ -69,6 +70,7 @@ class InstrumentedAuthServices
           VerificationError.expired => JourneyFailure.expired,
           VerificationError.invalid => JourneyFailure.invalid,
           VerificationError.internal => JourneyFailure.internal,
+          VerificationError.needsAssistance => JourneyFailure.unavailable,
         },
         FactorException(code: FactorError.expired) => JourneyFailure.expired,
         FactorException() => JourneyFailure.unavailable,

frontend/packages/sxchnge_auth/test/backend_test.dart

@@ -10,6 +10,43 @@ import 'package:sxchnge_auth/sxchnge_auth.dart';
 void main() {
   http.Response response(Map<String, Object?> data, [int status = 202]) =>
       http.Response(jsonEncode({'data': data}), status);
+  test(
+    'signup distinguishes support recovery and keeps the retry key',
+    () async {
+      final keys = <String>[];
+      var failed = true;
+      final service = BackendAuthServices(
+        baseUri: Uri.parse('https://api.example/api/v1'),
+        clientId: 'web',
+        client: MockClient((request) async {
+          keys.add(jsonDecode(request.body)['idempotencyKey'] as String);
+          return failed
+              ? response({'error': 'signup_attention_required'}, 503)
+              : response({'userId': 'user'});
+        }),
+      );
+      addTearDown(service.close);
+      const input = SignupRequest(
+        name: 'Ada',
+        email: 'ada@example.com',
+        password: 'password preserved',
+        locale: 'en',
+      );
+      await expectLater(
+        service.signup(input),
+        throwsA(
+          isA<AuthException>().having(
+            (error) => error.code,
+            'code',
+            AuthError.signupNeedsAssistance,
+          ),
+        ),
+      );
+      failed = false;
+      expect((await service.signup(input)).isSimulated, isFalse);
+      expect(keys[0], keys[1]);
+    },
+  );
   test('signup receipt avoids duplicate delivery and subsequent resend reaches API', () async {
     final paths = <String>[];
     final service = BackendAuthServices(
@@ -148,6 +185,34 @@ void main() {
       ),
     );
   });
+  test(
+    'verification recovery preserves assistance instead of requesting retry',
+    () async {
+      final service = BackendAuthServices(
+        baseUri: Uri.parse('https://api.example/api/v1'),
+        clientId: 'web',
+        client: MockClient(
+          (_) async => response({'error': 'signup_attention_required'}, 503),
+        ),
+      );
+      addTearDown(service.close);
+      final provider = VerificationProvider(service);
+      addTearDown(provider.dispose);
+      await provider.send(email: 'ada@example.com', locale: 'en');
+      expect(provider.state.status, VerificationStatus.error);
+      expect(provider.state.error, VerificationError.needsAssistance);
+      await expectLater(
+        service.confirm(token: 'old-token'),
+        throwsA(
+          isA<VerificationException>().having(
+            (e) => e.code,
+            'code',
+            VerificationError.needsAssistance,
+          ),
+        ),
+      );
+    },
+  );
   test(
     'resend preserves server challenge and retries the same delivery key',
     () async {