diff --git a/README.md b/README.md
index 97390ce..a949544 100644
--- a/README.md
+++ b/README.md
@@ -71,7 +71,7 @@ X-Request-ID: <request id>
 X-Device-ID: <optional device id>
 ```
 
-默认租户通过 `OLONS_SERVER_DEFAULT_TENANT_ID` 配置，现有 `olons_admin` 数据使用 `tenant_id=0`。服务不接受客户端传入租户身份。
+服务采用单租户模式，登录仅按手机号查找账号，不读取或接受租户环境变量。现有数据库中的 `tenant_id` 字段仅作为兼容字段保留，新注册数据固定写入 `0`。
 
 ## 验证
 
diff --git a/configs/olons_server.local.json b/configs/olons_server.local.json
index 730defc..c6a7dad 100644
--- a/configs/olons_server.local.json
+++ b/configs/olons_server.local.json
@@ -18,7 +18,6 @@
     "api_keys": [],
     "session_key_pattern": "olons_server:session:token:%s",
     "session_ttl_seconds": 1209600,
-    "default_tenant_id": 0,
     "finance_master_key": "olons-finance-master-key-v1-20261013",
     "allow_dev_header_auth": true,
     "required_api_key": false
diff --git a/configs/olons_server.test.json b/configs/olons_server.test.json
index 1e9d004..898a0f9 100644
--- a/configs/olons_server.test.json
+++ b/configs/olons_server.test.json
@@ -18,7 +18,6 @@
     "api_keys": [],
     "session_key_pattern": "olons_server:session:token:%s",
     "session_ttl_seconds": 1209600,
-    "default_tenant_id": 0,
     "finance_master_key": "olons-finance-master-key-v1-20261013",
     "required_api_key": true
   }
diff --git a/docs/移动端任务与账户平台前后端对接文档.md b/docs/移动端任务与账户平台前后端对接文档.md
index 8c50863..c374a7c 100644
--- a/docs/移动端任务与账户平台前后端对接文档.md
+++ b/docs/移动端任务与账户平台前后端对接文档.md
@@ -54,7 +54,7 @@
 | `Authorization: Bearer <token>` | 受保护接口必填 | 登录成功后取得的用户会话 |
 | `Idempotency-Key` | 取出提交必填 | 8–80 位请求唯一键；相同业务重试必须复用，不同请求禁止复用 |
 
-`tenant_id` 由后端部署配置确定。客户端不得在 Header、Query 或 Body 中传入租户身份。
+服务采用单租户模式，客户端不得在 Header、Query 或 Body 中传入租户身份。登录仅按手机号查找账号；数据库中的 `tenant_id` 仅作为兼容字段保留。
 
 ### 3.3 登录会话
 
diff --git a/internal/accounts/profile_test.go b/internal/accounts/profile_test.go
index fa07a19..a0550b2 100644
--- a/internal/accounts/profile_test.go
+++ b/internal/accounts/profile_test.go
@@ -19,7 +19,7 @@ type profileRepository struct {
 func (r *profileRepository) RegisterAccount(context.Context, store.AccountRegistration) (*store.Account, error) {
 	return nil, errors.New("not implemented")
 }
-func (r *profileRepository) AccountByMobile(context.Context, int64, string) (*store.Account, error) {
+func (r *profileRepository) AccountByMobile(context.Context, string) (*store.Account, error) {
 	return nil, errors.New("not implemented")
 }
 func (r *profileRepository) RecordLogin(context.Context, int64, int64) error { return nil }
diff --git a/internal/accounts/service.go b/internal/accounts/service.go
index 5ee0762..1af1e17 100644
--- a/internal/accounts/service.go
+++ b/internal/accounts/service.go
@@ -11,7 +11,6 @@ import (
 	"fmt"
 	"math/big"
 	"regexp"
-	"strconv"
 	"strings"
 	"time"
 	"unicode"
@@ -47,7 +46,7 @@ var (
 
 type Repository interface {
 	RegisterAccount(context.Context, store.AccountRegistration) (*store.Account, error)
-	AccountByMobile(context.Context, int64, string) (*store.Account, error)
+	AccountByMobile(context.Context, string) (*store.Account, error)
 	RecordLogin(context.Context, int64, int64) error
 	MemberOverview(context.Context, int64, int64) (*store.MemberOverview, error)
 	UpdateAvatar(context.Context, int64, int64, int64) (*store.Avatar, error)
@@ -179,7 +178,7 @@ func (s *Service) Register(ctx context.Context, input RegisterInput) (*Result, e
 			return nil, err
 		}
 		account, err := s.repository.RegisterAccount(ctx, store.AccountRegistration{
-			TenantID:     s.cfg.DefaultTenantID,
+			TenantID:     0,
 			MemberNo:     memberNo,
 			Username:     input.Username,
 			Mobile:       input.Phone,
@@ -237,7 +236,7 @@ func (s *Service) Login(ctx context.Context, input LoginInput) (*Result, error)
 	if attempts, err := s.redis.Get(ctx, rateKey).Int(); err == nil && attempts >= 10 {
 		return nil, ErrRateLimited
 	}
-	account, err := s.repository.AccountByMobile(ctx, s.cfg.DefaultTenantID, phone)
+	account, err := s.repository.AccountByMobile(ctx, phone)
 	if err != nil {
 		if errors.Is(err, store.ErrInvalidCredentials) {
 			s.recordLoginFailure(ctx, rateKey)
@@ -387,7 +386,7 @@ func (s *Service) issueSession(ctx context.Context, account *store.Account, devi
 
 func (s *Service) loginRateKey(phone string) string {
 	digest := sha256.Sum256([]byte(phone))
-	return "olons_server:auth:login-rate:" + strconv.FormatInt(s.cfg.DefaultTenantID, 10) + ":" + hex.EncodeToString(digest[:])
+	return "olons_server:auth:login-rate:" + hex.EncodeToString(digest[:])
 }
 
 func (s *Service) recordLoginFailure(ctx context.Context, key string) {
diff --git a/internal/accounts/service_test.go b/internal/accounts/service_test.go
index 3ba0674..28db536 100644
--- a/internal/accounts/service_test.go
+++ b/internal/accounts/service_test.go
@@ -14,7 +14,7 @@ type fakeRepository struct{}
 func (fakeRepository) RegisterAccount(context.Context, store.AccountRegistration) (*store.Account, error) {
 	return nil, errors.New("should not be called")
 }
-func (fakeRepository) AccountByMobile(context.Context, int64, string) (*store.Account, error) {
+func (fakeRepository) AccountByMobile(context.Context, string) (*store.Account, error) {
 	return nil, errors.New("should not be called")
 }
 func (fakeRepository) RecordLogin(context.Context, int64, int64) error {
diff --git a/internal/auth/auth.go b/internal/auth/auth.go
index 7fff5f0..7ccd513 100644
--- a/internal/auth/auth.go
+++ b/internal/auth/auth.go
@@ -46,17 +46,13 @@ func New(cfg config.AuthConfig, redisClient *redis.Client) *Authenticator {
 	return &Authenticator{cfg: cfg, redis: redisClient}
 }
 
-func (a *Authenticator) DefaultTenantID() int64 {
-	return a.cfg.DefaultTenantID
-}
-
 func (a *Authenticator) Authenticate(req *http.Request) (*Principal, error) {
 	if err := a.ValidateAPIKey(req); err != nil {
 		return nil, err
 	}
 	if a.cfg.AllowDevHeaderAuth {
 		if memberID := parseInt64Header(req, "X-Member-ID"); memberID > 0 {
-			return &Principal{TenantID: a.cfg.DefaultTenantID, MemberID: memberID,
+			return &Principal{TenantID: 0, MemberID: memberID,
 				DeviceID: strings.TrimSpace(req.Header.Get("X-Device-ID"))}, nil
 		}
 	}
diff --git a/internal/config/config.go b/internal/config/config.go
index 2d70cd3..797a54f 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -67,7 +67,6 @@ type AuthConfig struct {
 	APIKeys            []string `json:"api_keys"`
 	SessionKeyPattern  string   `json:"session_key_pattern"`
 	SessionTTLSeconds  int      `json:"session_ttl_seconds"`
-	DefaultTenantID    int64    `json:"default_tenant_id"`
 	DataEncryptionKey  string   `json:"data_encryption_key"`
 	LookupHMACKey      string   `json:"lookup_hmac_key"`
 	FinanceMasterKey   string   `json:"finance_master_key"`
@@ -106,7 +105,6 @@ func defaultConfig() *Config {
 		Auth: AuthConfig{
 			SessionKeyPattern: "olons_server:session:token:%s",
 			SessionTTLSeconds: 14 * 24 * 60 * 60,
-			DefaultTenantID:   0,
 			RequiredAPIKey:    true,
 		},
 		Upload: UploadConfig{Driver: "local", Dir: "storage/uploads", PublicPath: "/uploads", Region: "us-east-1"},
@@ -133,7 +131,6 @@ func applyEnv(cfg *Config) {
 	setInt(&cfg.Redis.DB, "OLONS_SERVER_REDIS_DB")
 	setString(&cfg.Auth.SessionKeyPattern, "OLONS_SERVER_SESSION_KEY_PATTERN")
 	setInt(&cfg.Auth.SessionTTLSeconds, "OLONS_SERVER_SESSION_TTL_SECONDS")
-	setInt64(&cfg.Auth.DefaultTenantID, "OLONS_SERVER_DEFAULT_TENANT_ID")
 	setString(&cfg.Auth.DataEncryptionKey, "OLONS_SERVER_DATA_ENCRYPTION_KEY")
 	setString(&cfg.Auth.LookupHMACKey, "OLONS_SERVER_LOOKUP_HMAC_KEY")
 	setString(&cfg.Auth.FinanceMasterKey, "OLONS_SERVER_FINANCE_MASTER_KEY")
@@ -177,9 +174,6 @@ func (c *Config) validate() error {
 	if c.Auth.SessionTTLSeconds <= 0 {
 		c.Auth.SessionTTLSeconds = 14 * 24 * 60 * 60
 	}
-	if c.Auth.DefaultTenantID < 0 {
-		return errors.New("default tenant id must not be negative")
-	}
 	if err := ValidateUpload(c.Upload); err != nil {
 		return err
 	}
@@ -261,14 +255,6 @@ func setInt(target *int, key string) {
 	}
 }
 
-func setInt64(target *int64, key string) {
-	if value := strings.TrimSpace(os.Getenv(key)); value != "" {
-		if parsed, err := strconv.ParseInt(value, 10, 64); err == nil {
-			*target = parsed
-		}
-	}
-}
-
 func setBool(target *bool, key string) {
 	switch strings.ToLower(strings.TrimSpace(os.Getenv(key))) {
 	case "1", "true", "yes", "on":
diff --git a/internal/config/config_test.go b/internal/config/config_test.go
index a8cd467..fe77552 100644
--- a/internal/config/config_test.go
+++ b/internal/config/config_test.go
@@ -7,9 +7,6 @@ func TestDefaultConfigUsesOlonsAdmin(t *testing.T) {
 	if err := cfg.validate(); err != nil {
 		t.Fatal(err)
 	}
-	if cfg.Auth.DefaultTenantID != 0 {
-		t.Fatalf("DefaultTenantID = %d", cfg.Auth.DefaultTenantID)
-	}
 }
 
 func TestConfigRejectsOtherDatabase(t *testing.T) {
diff --git a/internal/httpapi/portal.go b/internal/httpapi/portal.go
index ad0ebe5..6a9f6ed 100644
--- a/internal/httpapi/portal.go
+++ b/internal/httpapi/portal.go
@@ -85,7 +85,7 @@ func (a *API) content(w http.ResponseWriter, r *http.Request) {
 		writePortalError(w, r, portal.ErrContentKeyInvalid)
 		return
 	}
-	tenantID := a.auth.DefaultTenantID()
+	tenantID := int64(0)
 	if _, public := publicContentKeys[key]; !public {
 		principal, ok := a.authenticateMember(w, r)
 		if !ok {
diff --git a/internal/store/accounts.go b/internal/store/accounts.go
index 09bbead..79af28e 100644
--- a/internal/store/accounts.go
+++ b/internal/store/accounts.go
@@ -95,11 +95,11 @@ func (s *Store) RegisterAccount(ctx context.Context, input AccountRegistration)
 		InviteCode: input.InviteCode, MemberStatus: memberStatusActive, MemberCategory: memberCategoryReal}, nil
 }
 
-func (s *Store) AccountByMobile(ctx context.Context, tenantID int64, mobile string) (*Account, error) {
+func (s *Store) AccountByMobile(ctx context.Context, mobile string) (*Account, error) {
 	if s == nil || s.db == nil {
 		return nil, errors.New("store is unavailable")
 	}
-	return accountByMobile(ctx, s.db, tenantID, mobile)
+	return accountByMobile(ctx, s.db, mobile)
 }
 
 func (s *Store) RecordLogin(ctx context.Context, tenantID, memberID int64) error {
@@ -112,11 +112,11 @@ type queryer interface {
 	GetContext(context.Context, any, string, ...any) error
 }
 
-func accountByMobile(ctx context.Context, db queryer, tenantID int64, mobile string) (*Account, error) {
+func accountByMobile(ctx context.Context, db queryer, mobile string) (*Account, error) {
 	var row Account
 	err := db.GetContext(ctx, &row, `SELECT tenant_id, id AS member_id, member_no, username, mobile,
 		password_hash, invite_code, member_status, risk_status AS member_category
-		FROM hg_app_member WHERE tenant_id=? AND mobile=? AND deleted_at IS NULL LIMIT 1`, tenantID, mobile)
+		FROM hg_app_member WHERE mobile=? AND deleted_at IS NULL LIMIT 1`, mobile)
 	if errors.Is(err, sql.ErrNoRows) {
 		return nil, ErrInvalidCredentials
 	}
diff --git a/internal/store/accounts_test.go b/internal/store/accounts_test.go
new file mode 100644
index 0000000..af500cf
--- /dev/null
+++ b/internal/store/accounts_test.go
@@ -0,0 +1,37 @@
+package store
+
+import (
+	"context"
+	"strings"
+	"testing"
+)
+
+type accountQueryRecorder struct {
+	query string
+	args  []any
+}
+
+func (r *accountQueryRecorder) GetContext(_ context.Context, dest any, query string, args ...any) error {
+	r.query = query
+	r.args = args
+	account := dest.(*Account)
+	*account = Account{MemberID: 9, Mobile: "13311111111", MemberStatus: memberStatusActive}
+	return nil
+}
+
+func TestAccountByMobileDoesNotFilterTenant(t *testing.T) {
+	recorder := &accountQueryRecorder{}
+	account, err := accountByMobile(context.Background(), recorder, "13311111111")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if account.MemberID != 9 {
+		t.Fatalf("MemberID = %d, want 9", account.MemberID)
+	}
+	if strings.Contains(strings.ToLower(recorder.query), "tenant_id=?") {
+		t.Fatalf("query must not filter tenant: %s", recorder.query)
+	}
+	if len(recorder.args) != 1 || recorder.args[0] != "13311111111" {
+		t.Fatalf("query args = %#v", recorder.args)
+	}
+}