diff --git a/server/internal/auth/device_register_test.go b/server/internal/auth/device_register_test.go
index af37572..6c3924c 100644
--- a/server/internal/auth/device_register_test.go
+++ b/server/internal/auth/device_register_test.go
@@ -43,7 +43,7 @@ func TestService_RegisterDevice_OnRegisterAndLogin(t *testing.T) {
 		t.Fatalf("SendCode: %v", err)
 	}
 	code := codeInRedis(t, svc, email)
-	if _, e := svc.Register(ctx, email, code, pw, "1.2.3.4", meta); e != nil {
+	if _, e := svc.Register(ctx, email, code, pw, "1.2.3.4", meta, ""); e != nil {
 		t.Fatalf("Register: %v", e)
 	}
 	if len(reg.calls) != 1 || reg.calls[0].meta.DeviceID != "dev-uuid-1" || reg.calls[0].meta.Platform != "macos" {
@@ -79,7 +79,7 @@ func TestService_Login_SurfacesDeviceLimit(t *testing.T) {
 		t.Fatalf("SendCode: %v", err)
 	}
 	code := codeInRedis(t, svc, email)
-	if _, e := svc.Register(ctx, email, code, pw, "", meta); e != nil {
+	if _, e := svc.Register(ctx, email, code, pw, "", meta, ""); e != nil {
 		t.Fatalf("Register: %v", e)
 	}
 	out, _, e := svc.Login(ctx, email, pw, "", meta)
@@ -104,7 +104,7 @@ func TestService_RegisterDevice_BestEffort(t *testing.T) {
 		t.Fatalf("SendCode: %v", err)
 	}
 	code := codeInRedis(t, svc, email)
-	if _, e := svc.Register(ctx, email, code, "supersecret", "", DeviceMeta{DeviceID: "x", Platform: "windows"}); e != nil {
+	if _, e := svc.Register(ctx, email, code, "supersecret", "", DeviceMeta{DeviceID: "x", Platform: "windows"}, ""); e != nil {
 		t.Fatalf("Register must succeed despite registrar error: %v", e)
 	}
 }
@@ -120,7 +120,7 @@ func TestService_RegisterDevice_NoMeta(t *testing.T) {
 		t.Fatalf("SendCode: %v", err)
 	}
 	code := codeInRedis(t, svc, email)
-	if _, e := svc.Register(ctx, email, code, "supersecret", "", DeviceMeta{}); e != nil {
+	if _, e := svc.Register(ctx, email, code, "supersecret", "", DeviceMeta{}, ""); e != nil {
 		t.Fatalf("Register: %v", e)
 	}
 	if len(reg.calls) != 0 {
diff --git a/server/internal/auth/handler.go b/server/internal/auth/handler.go
index 24389e6..6152ae7 100644
--- a/server/internal/auth/handler.go
+++ b/server/internal/auth/handler.go
@@ -61,10 +61,11 @@ func (d deviceBody) toMeta() DeviceMeta {
 }
 
 type registerRequest struct {
-	Email    string     `json:"email"`
-	Code     string     `json:"code"`
-	Password string     `json:"password"`
-	Device   deviceBody `json:"device"`
+	Email      string     `json:"email"`
+	Code       string     `json:"code"`
+	Password   string     `json:"password"`
+	Device     deviceBody `json:"device"`
+	InviteCode string     `json:"invite_code"` // 选填:邀请码,注册后 best-effort 归因
 }
 
 type loginRequest struct {
@@ -104,7 +105,7 @@ func (h *Handler) Register(w http.ResponseWriter, r *http.Request) {
 	if !decodeJSON(w, r, &req) {
 		return
 	}
-	pair, apiErr := h.svc.Register(r.Context(), req.Email, req.Code, req.Password, clientIP(r), req.Device.toMeta())
+	pair, apiErr := h.svc.Register(r.Context(), req.Email, req.Code, req.Password, clientIP(r), req.Device.toMeta(), req.InviteCode)
 	if apiErr != nil {
 		writeAPIErr(w, apiErr, 0)
 		return
diff --git a/server/internal/auth/integration_test.go b/server/internal/auth/integration_test.go
index e3fb5bf..015aec7 100644
--- a/server/internal/auth/integration_test.go
+++ b/server/internal/auth/integration_test.go
@@ -140,7 +140,7 @@ func TestIntegration_FullChain(t *testing.T) {
 	}
 
 	// 2. Register → trial subscription must exist for 7 days.
-	pair, apiErr := svc.Register(ctx, email, code, pw, "203.0.113.10", DeviceMeta{})
+	pair, apiErr := svc.Register(ctx, email, code, pw, "203.0.113.10", DeviceMeta{}, "")
 	if apiErr != nil {
 		t.Fatalf("Register: %v", apiErr)
 	}
@@ -170,7 +170,7 @@ func TestIntegration_FullChain(t *testing.T) {
 	}
 	// Force a fresh code regardless of rate limit.
 	_ = rdb.Set(ctx, codeKey(email), code, 10*time.Minute).Err()
-	if _, e := svc.Register(ctx, email, code, pw, "203.0.113.10", DeviceMeta{}); e == nil || e.Code != ErrCodeInvalid.Code {
+	if _, e := svc.Register(ctx, email, code, pw, "203.0.113.10", DeviceMeta{}, ""); e == nil || e.Code != ErrCodeInvalid.Code {
 		t.Fatalf("want code_invalid (anti-enumeration), got %v", e)
 	}
 
diff --git a/server/internal/auth/register_invite_test.go b/server/internal/auth/register_invite_test.go
new file mode 100644
index 0000000..0cd4c78
--- /dev/null
+++ b/server/internal/auth/register_invite_test.go
@@ -0,0 +1,43 @@
+package auth
+
+import (
+	"context"
+	"testing"
+)
+
+// fakeHook captures the arguments passed to OnRegister so tests can assert on
+// them without depending on the real reward.Service.
+type fakeHook struct {
+	gotInvitee int64
+	gotCode    string
+	gotDev     string
+}
+
+func (f *fakeHook) OnRegister(_ context.Context, inviteeID int64, code, dev string) {
+	f.gotInvitee, f.gotCode, f.gotDev = inviteeID, code, dev
+}
+
+// TestRegister_CallsReferralHookWithInviteCode verifies that a successful
+// registration best-effort invokes the ReferralHook with the invite code and
+// this registration's device UUID (not some stale/historical value).
+func TestRegister_CallsReferralHookWithInviteCode(t *testing.T) {
+	svc, _, _ := newService(t, ServiceConfig{})
+	ctx := context.Background()
+	const email = "new@x.com"
+
+	if _, err := svc.SendCode(ctx, email, "1.2.3.4"); err != nil {
+		t.Fatalf("SendCode: %v", err)
+	}
+	code := codeInRedis(t, svc, email)
+
+	h := &fakeHook{}
+	svc.SetReferralHook(h)
+
+	_, apiErr := svc.Register(ctx, email, code, "password123", "1.2.3.4", DeviceMeta{DeviceID: "dev-1"}, "INVCODE9")
+	if apiErr != nil {
+		t.Fatalf("Register: %v", apiErr)
+	}
+	if h.gotCode != "INVCODE9" || h.gotDev != "dev-1" || h.gotInvitee == 0 {
+		t.Fatalf("hook got invitee=%d code=%q dev=%q", h.gotInvitee, h.gotCode, h.gotDev)
+	}
+}
diff --git a/server/internal/auth/service.go b/server/internal/auth/service.go
index e99b78a..0b77e14 100644
--- a/server/internal/auth/service.go
+++ b/server/internal/auth/service.go
@@ -132,12 +132,22 @@ type Service struct {
 	now      func() time.Time
 	devReg   DeviceRegistrar // nil until wired; registration is best-effort
 	sessions SessionStore    // nil until wired; session recording is best-effort
+	referral ReferralHook    // nil until wired; referral attribution is best-effort
 }
 
-// SetDeviceRegistrar / SetSessionStore wire collaborators after construction
-// (main keeps auth, devices and sessions decoupled). Call once during startup.
+// ReferralHook is invoked after a successful registration to attribute the new
+// account to the invite code it registered with (best-effort; implemented by
+// reward.Service). Defined consumer-side to avoid an import cycle.
+type ReferralHook interface {
+	OnRegister(ctx context.Context, inviteeID int64, inviteCode, deviceUUID string)
+}
+
+// SetDeviceRegistrar / SetSessionStore / SetReferralHook wire collaborators
+// after construction (main keeps auth, devices, sessions and reward decoupled).
+// Call once during startup.
 func (s *Service) SetDeviceRegistrar(r DeviceRegistrar) { s.devReg = r }
 func (s *Service) SetSessionStore(st SessionStore)      { s.sessions = st }
+func (s *Service) SetReferralHook(h ReferralHook)       { s.referral = h }
 
 // recordLogin registers the device and binds a session to the freshly-issued
 // refresh JTI. Best-effort: a registrar/session error (device cap, transient DB)
@@ -267,7 +277,7 @@ func (s *Service) SendCode(ctx context.Context, rawEmail, ip string) (retryAfter
 
 // Register verifies the code (one-time), creates the account plus a 7-day PRO
 // trial in a single transaction, and returns a fresh token pair.
-func (s *Service) Register(ctx context.Context, rawEmail, code, password, ip string, device DeviceMeta) (*TokenPair, *apierr.Error) {
+func (s *Service) Register(ctx context.Context, rawEmail, code, password, ip string, device DeviceMeta, inviteCode string) (*TokenPair, *apierr.Error) {
 	email := NormalizeEmail(rawEmail)
 	if !ValidEmail(email) || len(password) < 8 || len(code) != 6 {
 		return nil, ErrInvalidRequest
@@ -301,6 +311,9 @@ func (s *Service) Register(ctx context.Context, rawEmail, code, password, ip str
 		return nil, ErrInternal
 	}
 	s.recordLogin(ctx, user.ID, jti, ip, device)
+	if s.referral != nil {
+		s.referral.OnRegister(ctx, user.ID, inviteCode, device.DeviceID) // best-effort
+	}
 	return pair, nil
 }
 
diff --git a/server/internal/auth/service_test.go b/server/internal/auth/service_test.go
index 33edc61..9f83d64 100644
--- a/server/internal/auth/service_test.go
+++ b/server/internal/auth/service_test.go
@@ -40,7 +40,7 @@ func TestService_RegisterFullFlow(t *testing.T) {
 	}
 	code := codeInRedis(t, svc, email)
 
-	pair, apiErr := svc.Register(ctx, email, code, "supersecret", "", DeviceMeta{})
+	pair, apiErr := svc.Register(ctx, email, code, "supersecret", "", DeviceMeta{}, "")
 	if apiErr != nil {
 		t.Fatalf("Register: %v", apiErr)
 	}
@@ -84,7 +84,7 @@ func TestService_DuplicateEmailConflict(t *testing.T) {
 
 	// First registration.
 	_, _ = svc.SendCode(ctx, email, "")
-	if _, e := svc.Register(ctx, email, codeInRedis(t, svc, email), "password1", "", DeviceMeta{}); e != nil {
+	if _, e := svc.Register(ctx, email, codeInRedis(t, svc, email), "password1", "", DeviceMeta{}, ""); e != nil {
 		t.Fatalf("first register: %v", e)
 	}
 
@@ -103,7 +103,7 @@ func TestService_DuplicateEmailConflict(t *testing.T) {
 	if err := svc.rdb.Set(ctx, codeKey(email), "654321", 10*time.Minute).Err(); err != nil {
 		t.Fatalf("force code: %v", err)
 	}
-	_, apiErr := svc.Register(ctx, email, "654321", "password2", "", DeviceMeta{})
+	_, apiErr := svc.Register(ctx, email, "654321", "password2", "", DeviceMeta{}, "")
 	if apiErr == nil || apiErr.Code != ErrCodeInvalid.Code {
 		t.Fatalf("want code_invalid (anti-enumeration), got %v", apiErr)
 	}
@@ -115,7 +115,7 @@ func TestService_CodeWrong(t *testing.T) {
 	const email = "wrong@example.com"
 	_, _ = svc.SendCode(ctx, email, "")
 
-	_, apiErr := svc.Register(ctx, email, "000000", "password1", "", DeviceMeta{})
+	_, apiErr := svc.Register(ctx, email, "000000", "password1", "", DeviceMeta{}, "")
 	if apiErr == nil || apiErr.Code != ErrCodeInvalid.Code {
 		t.Fatalf("want code_invalid, got %v", apiErr)
 	}
@@ -131,7 +131,7 @@ func TestService_CodeExpired(t *testing.T) {
 	// Expire the code key.
 	svc.rdb.Del(ctx, codeKey(email))
 
-	_, apiErr := svc.Register(ctx, email, code, "password1", "", DeviceMeta{})
+	_, apiErr := svc.Register(ctx, email, code, "password1", "", DeviceMeta{}, "")
 	if apiErr == nil || apiErr.Code != ErrCodeInvalid.Code {
 		t.Fatalf("want code_invalid after expiry, got %v", apiErr)
 	}
@@ -144,11 +144,11 @@ func TestService_CodeReuseRejected(t *testing.T) {
 	_, _ = svc.SendCode(ctx, email, "")
 	code := codeInRedis(t, svc, email)
 
-	if _, e := svc.Register(ctx, email, code, "password1", "", DeviceMeta{}); e != nil {
+	if _, e := svc.Register(ctx, email, code, "password1", "", DeviceMeta{}, ""); e != nil {
 		t.Fatalf("first register: %v", e)
 	}
 	// Re-using the consumed code must fail.
-	_, apiErr := svc.Register(ctx, "other@example.com", code, "password1", "", DeviceMeta{})
+	_, apiErr := svc.Register(ctx, "other@example.com", code, "password1", "", DeviceMeta{}, "")
 	if apiErr == nil || apiErr.Code != ErrCodeInvalid.Code {
 		t.Fatalf("want code_invalid on reuse, got %v", apiErr)
 	}
@@ -163,12 +163,12 @@ func TestService_CodeBruteForceBurned(t *testing.T) {
 
 	// 3 wrong attempts burn the code.
 	for i := 0; i < 3; i++ {
-		if _, e := svc.Register(ctx, email, "999999", "password1", "", DeviceMeta{}); e == nil {
+		if _, e := svc.Register(ctx, email, "999999", "password1", "", DeviceMeta{}, ""); e == nil {
 			t.Fatal("wrong code should fail")
 		}
 	}
 	// Even the correct code no longer works.
-	if _, e := svc.Register(ctx, email, good, "password1", "", DeviceMeta{}); e == nil || e.Code != ErrCodeInvalid.Code {
+	if _, e := svc.Register(ctx, email, good, "password1", "", DeviceMeta{}, ""); e == nil || e.Code != ErrCodeInvalid.Code {
 		t.Fatalf("burned code should reject correct value, got %v", e)
 	}
 }
@@ -205,7 +205,7 @@ func TestService_LoginAndLockout(t *testing.T) {
 	const pw = "rightpassword"
 
 	_, _ = svc.SendCode(ctx, email, "")
-	if _, e := svc.Register(ctx, email, codeInRedis(t, svc, email), pw, "", DeviceMeta{}); e != nil {
+	if _, e := svc.Register(ctx, email, codeInRedis(t, svc, email), pw, "", DeviceMeta{}, ""); e != nil {
 		t.Fatalf("register: %v", e)
 	}
 
@@ -247,7 +247,7 @@ func TestService_BannedUserRejected(t *testing.T) {
 	const pw = "password1"
 
 	_, _ = svc.SendCode(ctx, email, "")
-	if _, e := svc.Register(ctx, email, codeInRedis(t, svc, email), pw, "", DeviceMeta{}); e != nil {
+	if _, e := svc.Register(ctx, email, codeInRedis(t, svc, email), pw, "", DeviceMeta{}, ""); e != nil {
 		t.Fatalf("register: %v", e)
 	}
 	store.setStatus(email, "banned")
@@ -264,7 +264,7 @@ func TestService_RefreshRotation(t *testing.T) {
 	const email = "refresh@example.com"
 
 	_, _ = svc.SendCode(ctx, email, "")
-	pair, e := svc.Register(ctx, email, codeInRedis(t, svc, email), "password1", "", DeviceMeta{})
+	pair, e := svc.Register(ctx, email, codeInRedis(t, svc, email), "password1", "", DeviceMeta{}, "")
 	if e != nil {
 		t.Fatalf("register: %v", e)
 	}