diff --git a/app/build.gradle.kts b/app/build.gradle.kts
index fabcbf1b..2ff19d2c 100644
--- a/app/build.gradle.kts
+++ b/app/build.gradle.kts
@@ -109,6 +109,11 @@ dependencies {
     implementation(libs.androidx.navigation.fragment.ktx)
     implementation(libs.androidx.navigation.ui.ktx)
 
+    // WorkManager (FCM 토큰 전송 예약)
+    implementation(libs.androidx.work.runtime.ktx)
+    implementation(libs.androidx.hilt.work)
+    "ksp"(libs.androidx.hilt.compiler)
+
     implementation(libs.appauth)
 
     // Kakao Map
diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 86b9abff..ce261c91 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
-<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools">
 
     <!-- 인터넷 권한 -->
     <uses-permission android:name="android.permission.INTERNET" />
@@ -44,6 +45,18 @@
             android:name="com.kakao.sdk.AppKey"
             android:value="${KAKAO_NATIVE_APP_KEY}" />
 
+        <!-- WorkManager 기본 초기화를 끄고 Configuration.Provider로 직접 초기화합니다 -->
+        <provider
+            android:name="androidx.startup.InitializationProvider"
+            android:authorities="${applicationId}.androidx-startup"
+            android:exported="false"
+            tools:node="merge">
+            <meta-data
+                android:name="androidx.work.WorkManagerInitializer"
+                android:value="androidx.startup"
+                tools:node="remove" />
+        </provider>
+
         <provider
             android:name="androidx.core.content.FileProvider"
             android:authorities="${applicationId}.fileprovider"
diff --git a/app/src/main/java/com/project200/undabang/ApplicationClass.kt b/app/src/main/java/com/project200/undabang/ApplicationClass.kt
index 76520803..56c950e5 100644
--- a/app/src/main/java/com/project200/undabang/ApplicationClass.kt
+++ b/app/src/main/java/com/project200/undabang/ApplicationClass.kt
@@ -5,13 +5,26 @@ import android.app.NotificationChannel
 import android.app.NotificationManager
 import android.content.Context
 import androidx.appcompat.app.AppCompatDelegate
+import androidx.hilt.work.HiltWorkerFactory
+import androidx.work.Configuration
 import com.google.firebase.crashlytics.FirebaseCrashlytics
 import com.kakao.vectormap.KakaoMapSdk
 import dagger.hilt.android.HiltAndroidApp
 import timber.log.Timber
+import javax.inject.Inject
 
 @HiltAndroidApp
-class ApplicationClass : Application() {
+class ApplicationClass : Application(), Configuration.Provider {
+    @Inject
+    lateinit var workerFactory: HiltWorkerFactory
+
+    /** WorkManager가 Hilt로 Worker를 생성하도록 팩토리를 넘깁니다 */
+    override val workManagerConfiguration: Configuration
+        get() =
+            Configuration.Builder()
+                .setWorkerFactory(workerFactory)
+                .build()
+
     override fun onCreate() {
         super.onCreate()
 
diff --git a/app/src/main/java/com/project200/undabang/fcm/FcmService.kt b/app/src/main/java/com/project200/undabang/fcm/FcmService.kt
index b8945885..d0fedca6 100644
--- a/app/src/main/java/com/project200/undabang/fcm/FcmService.kt
+++ b/app/src/main/java/com/project200/undabang/fcm/FcmService.kt
@@ -30,13 +30,15 @@ class FcmService : FirebaseMessagingService() {
 
     /**
      * 새로운 FCM 토큰이 발급되거나 갱신될 때 호출됩니다.
-     * 이 토큰은 백엔드 서버로 전송되어 특정 기기에 알림을 보내는 데 사용됩니다.
+     * 기기에 저장한 뒤 서버 반영은 워커에 맡깁니다.
+     * 이 콜백은 백그라운드에서도 불려 네트워크와 로그인 상태를 확신할 수 없습니다.
      */
     override fun onNewToken(token: String) {
         super.onNewToken(token)
         Timber.tag(TAG).d("Refreshed FCM token: $token")
 
         saveFcmToken(token)
+        FcmTokenSyncWorker.enqueue(applicationContext)
     }
 
     /**
diff --git a/app/src/main/java/com/project200/undabang/fcm/FcmTokenSyncPolicy.kt b/app/src/main/java/com/project200/undabang/fcm/FcmTokenSyncPolicy.kt
new file mode 100644
index 00000000..4767586c
--- /dev/null
+++ b/app/src/main/java/com/project200/undabang/fcm/FcmTokenSyncPolicy.kt
@@ -0,0 +1,10 @@
+package com.project200.undabang.fcm
+
+/** FcmTokenSyncWorker의 재시도 판단. 안드로이드 의존성이 없어 단위 테스트로 검증합니다 */
+object FcmTokenSyncPolicy {
+    /** 전송 실패 시 총 시도 횟수 상한 */
+    const val MAX_ATTEMPT_COUNT = 5
+
+    /** runAttemptCount는 WorkManager가 주는 값으로 첫 실행이 0입니다 */
+    fun shouldRetry(runAttemptCount: Int): Boolean = runAttemptCount + 1 < MAX_ATTEMPT_COUNT
+}
diff --git a/app/src/main/java/com/project200/undabang/fcm/FcmTokenSyncWorker.kt b/app/src/main/java/com/project200/undabang/fcm/FcmTokenSyncWorker.kt
new file mode 100644
index 00000000..653c90b5
--- /dev/null
+++ b/app/src/main/java/com/project200/undabang/fcm/FcmTokenSyncWorker.kt
@@ -0,0 +1,106 @@
+package com.project200.undabang.fcm
+
+import android.content.Context
+import androidx.hilt.work.HiltWorker
+import androidx.work.BackoffPolicy
+import androidx.work.Constraints
+import androidx.work.CoroutineWorker
+import androidx.work.ExistingWorkPolicy
+import androidx.work.NetworkType
+import androidx.work.OneTimeWorkRequestBuilder
+import androidx.work.WorkManager
+import androidx.work.WorkerParameters
+import com.project200.domain.model.FcmTokenSyncResult
+import com.project200.domain.usecase.SyncFcmTokenUseCase
+import com.project200.undabang.oauth.AuthManager
+import com.project200.undabang.oauth.AuthStateManager
+import com.project200.undabang.oauth.TokenRefreshResult
+import dagger.assisted.Assisted
+import dagger.assisted.AssistedInject
+import net.openid.appauth.AuthorizationException
+import timber.log.Timber
+import java.util.concurrent.TimeUnit
+
+/**
+ * 갱신된 FCM 토큰을 서버에 반영하는 워커입니다
+ * onNewToken()은 백그라운드나 프로세스 기동 직후에도 불려 네트워크와 로그인 상태를 확신할 수 없습니다
+ * 전송을 워커로 미뤄 연결이 잡힌 뒤에 보내고 실패하면 다시 시도합니다
+ */
+@HiltWorker
+class FcmTokenSyncWorker
+    @AssistedInject
+    constructor(
+        @Assisted appContext: Context,
+        @Assisted params: WorkerParameters,
+        private val syncFcmTokenUseCase: SyncFcmTokenUseCase,
+        private val authStateManager: AuthStateManager,
+        private val authManager: AuthManager,
+    ) : CoroutineWorker(appContext, params) {
+        override suspend fun doWork(): Result {
+            // POST /login은 @AccessTokenWithFcmApi라 401 자동 갱신이 없음 - 만료면 먼저 갱신
+            if (authStateManager.getCurrent().needsTokenRefresh) {
+                when (val refresh = authManager.refreshAccessToken()) {
+                    is TokenRefreshResult.Success -> Unit
+                    is TokenRefreshResult.Error -> {
+                        val ex = refresh.exception
+                        val invalidGrant =
+                            ex?.type == AuthorizationException.TYPE_OAUTH_TOKEN_ERROR &&
+                                ex.error == "invalid_grant"
+                        // invalid_grant는 재시도해도 같음. 세션 정리는 refreshAccessToken() 내부가 함
+                        return if (invalidGrant) {
+                            Result.failure()
+                        } else if (FcmTokenSyncPolicy.shouldRetry(runAttemptCount)) {
+                            Result.retry()
+                        } else {
+                            Result.failure()
+                        }
+                    }
+                    is TokenRefreshResult.NoRefreshToken,
+                    is TokenRefreshResult.ConfigError,
+                    -> return Result.failure()
+                }
+            }
+
+            val syncResult = syncFcmTokenUseCase()
+            Timber.tag(TAG).d("FCM 토큰 전송 결과: $syncResult (시도 ${runAttemptCount + 1}회)")
+
+            return when (syncResult) {
+                FcmTokenSyncResult.SUCCESS -> Result.success()
+                // 로그인 전이거나 보낼 토큰이 없는 상태 - 재시도해도 같으므로 성공 처리
+                FcmTokenSyncResult.SKIPPED -> Result.success()
+                FcmTokenSyncResult.FAILURE ->
+                    if (FcmTokenSyncPolicy.shouldRetry(runAttemptCount)) Result.retry() else Result.failure()
+            }
+        }
+
+        companion object {
+            private const val TAG = "FcmTokenSyncWorker"
+            const val WORK_NAME = "fcm_token_sync"
+            private const val BACKOFF_DELAY_SECONDS = 30L
+
+            /**
+             * 토큰 등록을 예약합니다
+             * 대기 중에 토큰이 다시 갱신되면 새 요청으로 바꿔 백오프를 처음부터 다시 셉니다
+             * 워커는 실행 시점에 저장소에서 토큰을 읽으므로 마지막 값이 올라갑니다
+             */
+            fun enqueue(context: Context) {
+                val constraints =
+                    Constraints.Builder()
+                        .setRequiredNetworkType(NetworkType.CONNECTED)
+                        .build()
+
+                val request =
+                    OneTimeWorkRequestBuilder<FcmTokenSyncWorker>()
+                        .setConstraints(constraints)
+                        .setBackoffCriteria(
+                            BackoffPolicy.EXPONENTIAL,
+                            BACKOFF_DELAY_SECONDS,
+                            TimeUnit.SECONDS,
+                        )
+                        .build()
+
+                WorkManager.getInstance(context)
+                    .enqueueUniqueWork(WORK_NAME, ExistingWorkPolicy.REPLACE, request)
+            }
+        }
+    }
diff --git a/app/src/test/java/com/project200/undabang/fcm/FcmTokenSyncPolicyTest.kt b/app/src/test/java/com/project200/undabang/fcm/FcmTokenSyncPolicyTest.kt
new file mode 100644
index 00000000..9147cc3a
--- /dev/null
+++ b/app/src/test/java/com/project200/undabang/fcm/FcmTokenSyncPolicyTest.kt
@@ -0,0 +1,30 @@
+package com.project200.undabang.fcm
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.Test
+
+class FcmTokenSyncPolicyTest {
+    @Test
+    fun `첫 실행에서 실패하면 재시도한다`() {
+        assertThat(FcmTokenSyncPolicy.shouldRetry(0)).isTrue()
+    }
+
+    @Test
+    fun `상한 직전까지는 재시도한다`() {
+        val lastRetryableAttempt = FcmTokenSyncPolicy.MAX_ATTEMPT_COUNT - 2
+
+        assertThat(FcmTokenSyncPolicy.shouldRetry(lastRetryableAttempt)).isTrue()
+    }
+
+    @Test
+    fun `상한에 닿으면 재시도하지 않는다`() {
+        val lastAttempt = FcmTokenSyncPolicy.MAX_ATTEMPT_COUNT - 1
+
+        assertThat(FcmTokenSyncPolicy.shouldRetry(lastAttempt)).isFalse()
+    }
+
+    @Test
+    fun `상한을 넘긴 뒤에도 재시도하지 않는다`() {
+        assertThat(FcmTokenSyncPolicy.shouldRetry(FcmTokenSyncPolicy.MAX_ATTEMPT_COUNT)).isFalse()
+    }
+}
diff --git a/app/src/test/java/com/project200/undabang/main/MainViewModelTest.kt b/app/src/test/java/com/project200/undabang/main/MainViewModelTest.kt
index 7c752c2c..23f7b790 100644
--- a/app/src/test/java/com/project200/undabang/main/MainViewModelTest.kt
+++ b/app/src/test/java/com/project200/undabang/main/MainViewModelTest.kt
@@ -495,6 +495,27 @@ class MainViewModelTest {
             coVerify(exactly = 1) { mockLoginUseCase() }
         }
 
+    @Test
+    fun `FCM 등록 - 토큰이 없어 실패하면 대기가 닫히지 않고 재연결 때 재시도한다`() =
+        runTest {
+            // Given: FCM 토큰이 없어 서버 로그인이 막힌다
+            stubNoUpdate()
+            stubAuthState(isAuthorized = true)
+            coEvery { mockLoginUseCase() } returns
+                BaseResult.Error("NO_FCM_TOKEN", "FCM 토큰이 없어 서버 로그인을 보내지 않았습니다.") andThen
+                BaseResult.Success(Unit)
+            viewModel = createViewModel()
+            testDispatcher.scheduler.advanceUntilIdle()
+
+            // When: offline → online 재연결
+            networkStateFlow.emit(false)
+            networkStateFlow.emit(true)
+            testDispatcher.scheduler.advanceUntilIdle()
+
+            // Then: 성공으로 닫히지 않았으므로 재시도가 한 번 더 나간다
+            coVerify(exactly = 2) { mockLoginUseCase() }
+        }
+
     @Test
     fun `FCM 등록 - 요청이 진행 중이면 재연결이 겹쳐도 중복 발행하지 않는다`() =
         runTest {
diff --git a/data/src/main/java/com/project200/data/impl/AuthRepositoryImpl.kt b/data/src/main/java/com/project200/data/impl/AuthRepositoryImpl.kt
index e2dd2e70..001f7aae 100644
--- a/data/src/main/java/com/project200/data/impl/AuthRepositoryImpl.kt
+++ b/data/src/main/java/com/project200/data/impl/AuthRepositoryImpl.kt
@@ -6,6 +6,7 @@ import com.project200.data.dto.GetIsNicknameDuplicated
 import com.project200.data.dto.PostLoginRequest
 import com.project200.data.dto.PostSignUpRequest
 import com.project200.data.local.PreferenceManager
+import com.project200.data.utils.FcmTokenProvider
 import com.project200.data.utils.apiCallBuilder
 import com.project200.domain.model.BaseResult
 import com.project200.domain.model.RegistrationStatus
@@ -23,6 +24,7 @@ class AuthRepositoryImpl
         private val apiService: ApiService,
         private val spManager: PreferenceManager,
         private val authStateManager: AuthStateManager,
+        private val fcmTokenProvider: FcmTokenProvider,
         @IoDispatcher private val ioDispatcher: CoroutineDispatcher,
     ) : AuthRepository {
         override suspend fun checkIsRegistered(): RegistrationStatus {
@@ -56,7 +58,21 @@ class AuthRepositoryImpl
             }
         }
 
+        /**
+         * POST /login은 X-Fcm-Token 헤더로 기기 토큰을 등록합니다.
+         * 토큰이 없으면 서버는 헤더 없는 요청을 LOGIN_SUCCESS로 돌려주고 등록은 건너뜁니다.
+         * 그 성공을 그대로 올리면 재시도 경로가 닫히므로 보내기 전에 막습니다.
+         */
         override suspend fun login(): BaseResult<Unit> {
+            val fcmToken = withContext(ioDispatcher) { fcmTokenProvider.getFcmToken() }
+            if (fcmToken.isNullOrBlank()) {
+                Timber.tag(TAG).w("FCM 토큰이 없어 서버 로그인을 보내지 않습니다.")
+                return BaseResult.Error(
+                    errorCode = NO_FCM_TOKEN_ERROR_CODE,
+                    message = NO_FCM_TOKEN_ERROR_MESSAGE,
+                )
+            }
+
             return apiCallBuilder(
                 ioDispatcher = ioDispatcher,
                 apiCall = { apiService.postLogin(PostLoginRequest("ANDROID", "APP")) },
@@ -114,5 +130,7 @@ class AuthRepositoryImpl
 
         companion object {
             const val TAG = "AuthRepositoryImpl"
+            const val NO_FCM_TOKEN_ERROR_CODE = "NO_FCM_TOKEN"
+            private const val NO_FCM_TOKEN_ERROR_MESSAGE = "FCM 토큰이 없어 서버 로그인을 보내지 않았습니다."
         }
     }
diff --git a/data/src/main/java/com/project200/data/utils/FcmTokenProvider.kt b/data/src/main/java/com/project200/data/utils/FcmTokenProvider.kt
index 8f0afb0c..d82b7dca 100644
--- a/data/src/main/java/com/project200/data/utils/FcmTokenProvider.kt
+++ b/data/src/main/java/com/project200/data/utils/FcmTokenProvider.kt
@@ -3,35 +3,19 @@ package com.project200.data.utils
 import android.content.SharedPreferences
 import com.project200.common.constants.FcmConstants.KEY_FCM_TOKEN
 import com.project200.common.utils.EncryptedPrefs
-import timber.log.Timber
 import javax.inject.Inject
 import javax.inject.Singleton
 
+/**
+ * FCM 토큰을 읽는 단일 창구입니다
+ * 토큰은 FcmService.onNewToken()이 저장소에 직접 씁니다
+ * 메모리에 캐시하면 갱신 이후에도 옛 토큰이 헤더에 실리므로 호출할 때마다 저장소를 읽습니다
+ */
 @Singleton
 class FcmTokenProvider
     @Inject
     constructor(
         @EncryptedPrefs private val prefs: SharedPreferences,
     ) {
-        private var fcmToken: String? = null
-
-        init {
-            loadTokenFromPrefs()
-        }
-
-        private fun loadTokenFromPrefs() {
-            fcmToken = prefs.getString(KEY_FCM_TOKEN, null)
-            Timber.tag("FcmTokenProvider").d("FCM 토큰 : $fcmToken")
-        }
-
-        fun getFcmToken(): String? {
-            if (fcmToken == null) {
-                loadTokenFromPrefs()
-            }
-            return fcmToken
-        }
-
-        fun refreshToken() {
-            loadTokenFromPrefs()
-        }
+        fun getFcmToken(): String? = prefs.getString(KEY_FCM_TOKEN, null)
     }
diff --git a/domain/src/main/java/com/project200/domain/model/FcmTokenSyncResult.kt b/domain/src/main/java/com/project200/domain/model/FcmTokenSyncResult.kt
new file mode 100644
index 00000000..b51d8d0b
--- /dev/null
+++ b/domain/src/main/java/com/project200/domain/model/FcmTokenSyncResult.kt
@@ -0,0 +1,8 @@
+package com.project200.domain.model
+
+/** FCM 토큰 서버 반영 결과 */
+enum class FcmTokenSyncResult {
+    SUCCESS, // 서버에 반영됨
+    SKIPPED, // 로그인 전이거나 보낼 토큰이 없음. 재시도해도 같음
+    FAILURE, // 전송을 시도했으나 실패. 재시도 대상
+}
diff --git a/domain/src/main/java/com/project200/domain/usecase/SyncFcmTokenUseCase.kt b/domain/src/main/java/com/project200/domain/usecase/SyncFcmTokenUseCase.kt
new file mode 100644
index 00000000..21cb48ea
--- /dev/null
+++ b/domain/src/main/java/com/project200/domain/usecase/SyncFcmTokenUseCase.kt
@@ -0,0 +1,32 @@
+package com.project200.domain.usecase
+
+import com.project200.domain.model.BaseResult
+import com.project200.domain.model.FcmTokenSyncResult
+import com.project200.domain.repository.AuthRepository
+import com.project200.domain.repository.FcmRepository
+import javax.inject.Inject
+
+/**
+ * 저장된 FCM 토큰을 서버에 반영합니다
+ * 토큰 전용 엔드포인트가 없어 당분간 POST /login을 씁니다
+ * 토큰은 호출 시점에 저장소에서 읽습니다. 예약과 실행 사이에 토큰이 다시 갱신될 수 있습니다
+ */
+class SyncFcmTokenUseCase @Inject constructor(
+    private val authRepository: AuthRepository,
+    private val fcmRepository: FcmRepository
+) {
+    suspend operator fun invoke(): FcmTokenSyncResult {
+        if (authRepository.getMemberId().isNullOrBlank()) {
+            return FcmTokenSyncResult.SKIPPED
+        }
+
+        if (fcmRepository.getFcmTokenFromPrefs().isNullOrBlank()) {
+            return FcmTokenSyncResult.SKIPPED
+        }
+
+        return when (authRepository.login()) {
+            is BaseResult.Success -> FcmTokenSyncResult.SUCCESS
+            is BaseResult.Error -> FcmTokenSyncResult.FAILURE
+        }
+    }
+}
diff --git a/domain/src/test/java/com/project200/domain/usecase/SyncFcmTokenUseCaseTest.kt b/domain/src/test/java/com/project200/domain/usecase/SyncFcmTokenUseCaseTest.kt
new file mode 100644
index 00000000..356039ba
--- /dev/null
+++ b/domain/src/test/java/com/project200/domain/usecase/SyncFcmTokenUseCaseTest.kt
@@ -0,0 +1,123 @@
+package com.project200.domain.usecase
+
+import com.google.common.truth.Truth.assertThat
+import com.project200.domain.model.BaseResult
+import com.project200.domain.model.FcmTokenSyncResult
+import com.project200.domain.repository.AuthRepository
+import com.project200.domain.repository.FcmRepository
+import io.mockk.coEvery
+import io.mockk.coVerify
+import io.mockk.impl.annotations.MockK
+import io.mockk.junit4.MockKRule
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.runTest
+import org.junit.Before
+import org.junit.Rule
+import org.junit.Test
+
+@ExperimentalCoroutinesApi
+class SyncFcmTokenUseCaseTest {
+
+    @get:Rule
+    val mockkRule = MockKRule(this)
+
+    @MockK
+    private lateinit var mockAuthRepository: AuthRepository
+
+    @MockK
+    private lateinit var mockFcmRepository: FcmRepository
+
+    private lateinit var useCase: SyncFcmTokenUseCase
+
+    @Before
+    fun setUp() {
+        useCase = SyncFcmTokenUseCase(mockAuthRepository, mockFcmRepository)
+    }
+
+    @Test
+    fun `로그인 전이면 전송하지 않고 SKIPPED를 반환한다`() = runTest {
+        // Given: 회원ID가 없다 = 로그인 전
+        coEvery { mockAuthRepository.getMemberId() } returns null
+
+        // When
+        val result = useCase()
+
+        // Then
+        assertThat(result).isEqualTo(FcmTokenSyncResult.SKIPPED)
+        coVerify(exactly = 0) { mockAuthRepository.login() }
+    }
+
+    @Test
+    fun `저장된 토큰이 없으면 전송하지 않고 SKIPPED를 반환한다`() = runTest {
+        // Given
+        coEvery { mockAuthRepository.getMemberId() } returns "member-1"
+        coEvery { mockFcmRepository.getFcmTokenFromPrefs() } returns null
+
+        // When
+        val result = useCase()
+
+        // Then
+        assertThat(result).isEqualTo(FcmTokenSyncResult.SKIPPED)
+        coVerify(exactly = 0) { mockAuthRepository.login() }
+    }
+
+    @Test
+    fun `전송에 성공하면 SUCCESS를 반환한다`() = runTest {
+        // Given
+        coEvery { mockAuthRepository.getMemberId() } returns "member-1"
+        coEvery { mockFcmRepository.getFcmTokenFromPrefs() } returns "token-1"
+        coEvery { mockAuthRepository.login() } returns BaseResult.Success(Unit)
+
+        // When
+        val result = useCase()
+
+        // Then
+        assertThat(result).isEqualTo(FcmTokenSyncResult.SUCCESS)
+        coVerify(exactly = 1) { mockAuthRepository.login() }
+    }
+
+    @Test
+    fun `전송에 실패하면 FAILURE를 반환한다`() = runTest {
+        // Given
+        coEvery { mockAuthRepository.getMemberId() } returns "member-1"
+        coEvery { mockFcmRepository.getFcmTokenFromPrefs() } returns "token-1"
+        coEvery { mockAuthRepository.login() } returns BaseResult.Error("NETWORK_ERROR", "네트워크 오류")
+
+        // When
+        val result = useCase()
+
+        // Then
+        assertThat(result).isEqualTo(FcmTokenSyncResult.FAILURE)
+    }
+
+    @Test
+    fun `토큰이 없어 로그인이 막히면 FAILURE를 반환한다`() = runTest {
+        // Given: 조회 직후 토큰이 지워져 login()이 NO_FCM_TOKEN으로 막힌 경우
+        coEvery { mockAuthRepository.getMemberId() } returns "member-1"
+        coEvery { mockFcmRepository.getFcmTokenFromPrefs() } returns "token-1"
+        coEvery { mockAuthRepository.login() } returns
+            BaseResult.Error("NO_FCM_TOKEN", "FCM 토큰이 없어 서버 로그인을 보내지 않았습니다.")
+
+        // When
+        val result = useCase()
+
+        // Then
+        assertThat(result).isEqualTo(FcmTokenSyncResult.FAILURE)
+    }
+
+    @Test
+    fun `대기 중 토큰이 갱신되면 호출 시점의 값을 읽는다`() = runTest {
+        // Given: 예약 시점의 token-1이 아니라 실행 시점의 token-2가 저장소에 있다
+        coEvery { mockAuthRepository.getMemberId() } returns "member-1"
+        coEvery { mockFcmRepository.getFcmTokenFromPrefs() } returns "token-1" andThen "token-2"
+        coEvery { mockAuthRepository.login() } returns BaseResult.Success(Unit)
+        useCase() // 첫 실행이 token-1을 읽는다
+
+        // When: 두 번째 실행
+        val result = useCase()
+
+        // Then: 저장소를 매번 다시 읽는다
+        assertThat(result).isEqualTo(FcmTokenSyncResult.SUCCESS)
+        coVerify(exactly = 2) { mockFcmRepository.getFcmTokenFromPrefs() }
+    }
+}
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 7ec70c78..f8912edd 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -32,6 +32,8 @@ androidxLifecycle = "2.7.0"
 androidxNavigation = "2.7.7"
 androidxRoom = "2.6.1"
 androidxDatastore = "1.0.0"
+androidxWork = "2.9.1"
+androidxHilt = "1.2.0"
 androidxArchCoreTesting = "2.2.0" # 테스트용
 androidxMedia = "1.7.0"
 lottie = "6.6.6"
@@ -164,6 +166,11 @@ androidx-room-compiler = { group = "androidx.room", name = "room-compiler", vers
 # AndroidX DataStore (Preferences Example)
 androidx-datastore-preferences = { group = "androidx.datastore", name = "datastore-preferences", version.ref = "androidxDatastore" }
 
+# AndroidX WorkManager
+androidx-work-runtime-ktx = { group = "androidx.work", name = "work-runtime-ktx", version.ref = "androidxWork" }
+androidx-hilt-work = { group = "androidx.hilt", name = "hilt-work", version.ref = "androidxHilt" }
+androidx-hilt-compiler = { group = "androidx.hilt", name = "hilt-compiler", version.ref = "androidxHilt" } # KSP
+
 # Hilt (DI)
 hilt-android = { group = "com.google.dagger", name = "hilt-android", version.ref = "hilt" }
 hilt-compiler = { group = "com.google.dagger", name = "hilt-compiler", version.ref = "hilt" } # KSP/Kapt