diff --git a/CLAUDE.md b/CLAUDE.md
index 1fb4baa..6f653b7 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -1,6 +1,6 @@
 # Project Purpose
 This project implements an image picker library for Android using Jetpack Compose.
-v1 focuses on the core image selection flow.
+v1 focuses on the core image selection flow. continue to work v3
 
 ### Development Goals
 - Implement a reusable Image Picker component for use across apps
diff --git a/app/src/main/java/com/universe/dynamicimagepicker/MainActivity.kt b/app/src/main/java/com/universe/dynamicimagepicker/MainActivity.kt
index 76a8b7b..b7bfce7 100644
--- a/app/src/main/java/com/universe/dynamicimagepicker/MainActivity.kt
+++ b/app/src/main/java/com/universe/dynamicimagepicker/MainActivity.kt
@@ -31,7 +31,7 @@ import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
-import androidx.compose.runtime.remember
+import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.draw.clip
@@ -62,8 +62,8 @@ class MainActivity : ComponentActivity() {
 
 @Composable
 private fun PickerHost(modifier: Modifier = Modifier) {
-    var showPicker by remember { mutableStateOf(false) }
-    var selectedImages by remember { mutableStateOf(emptyList<PickedImage>()) }
+    var showPicker by rememberSaveable { mutableStateOf(false) }
+    var selectedImages by rememberSaveable { mutableStateOf(emptyList<PickedImage>()) }
 
     if (showPicker) {
         DynamicImagePicker(
diff --git a/build.gradle.kts b/build.gradle.kts
index 65fb656..1a68949 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -4,4 +4,5 @@ plugins {
     alias(libs.plugins.android.library) apply false
     alias(libs.plugins.kotlin.android) apply false
     alias(libs.plugins.kotlin.compose) apply false
+    alias(libs.plugins.kotlin.parcelize) apply false
 }
\ No newline at end of file
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index b8290c1..2923441 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -22,6 +22,8 @@ coroutines = "1.9.0"
 junit = "4.13.2"
 junitVersion = "1.3.0"
 espressoCore = "3.7.0"
+turbine = "1.2.0"
+mockk = "1.13.13"
 
 exifinterface = "1.4.2"
 paging = "3.3.6"
@@ -63,6 +65,9 @@ androidx-junit = { group = "androidx.test.ext", name = "junit", version.ref = "j
 androidx-espresso-core = { group = "androidx.test.espresso", name = "espresso-core", version.ref = "espressoCore" }
 androidx-compose-ui-test-junit4 = { group = "androidx.compose.ui", name = "ui-test-junit4" }
 androidx-compose-ui-test-manifest = { group = "androidx.compose.ui", name = "ui-test-manifest" }
+kotlinx-coroutines-test = { group = "org.jetbrains.kotlinx", name = "kotlinx-coroutines-test", version.ref = "coroutines" }
+turbine = { group = "app.cash.turbine", name = "turbine", version.ref = "turbine" }
+mockk = { group = "io.mockk", name = "mockk", version.ref = "mockk" }
 androidx-exifinterface = { group = "androidx.exifinterface", name = "exifinterface", version.ref = "exifinterface" }
 androidx-paging-runtime = { group = "androidx.paging", name = "paging-runtime", version.ref = "paging" }
 androidx-paging-compose = { group = "androidx.paging", name = "paging-compose", version.ref = "paging" }
@@ -72,3 +77,4 @@ android-application = { id = "com.android.application", version.ref = "agp" }
 android-library = { id = "com.android.library", version.ref = "agp" }
 kotlin-android = { id = "org.jetbrains.kotlin.android", version.ref = "kotlin" }
 kotlin-compose = { id = "org.jetbrains.kotlin.plugin.compose", version.ref = "kotlin" }
+kotlin-parcelize = { id = "org.jetbrains.kotlin.plugin.parcelize", version.ref = "kotlin" }
\ No newline at end of file
diff --git a/imagepicker/build.gradle.kts b/imagepicker/build.gradle.kts
index e3fc18c..d0c789c 100644
--- a/imagepicker/build.gradle.kts
+++ b/imagepicker/build.gradle.kts
@@ -4,6 +4,7 @@ plugins {
     alias(libs.plugins.android.library)
     alias(libs.plugins.kotlin.android)
     alias(libs.plugins.kotlin.compose)
+    alias(libs.plugins.kotlin.parcelize)
     id("maven-publish")
     id("signing")
 }
@@ -181,6 +182,10 @@ dependencies {
 
     // Testing
     testImplementation(libs.junit)
+    testImplementation(kotlin("test"))
+    testImplementation(libs.kotlinx.coroutines.test)
+    testImplementation(libs.turbine)
+    testImplementation(libs.mockk)
     androidTestImplementation(libs.androidx.junit)
     androidTestImplementation(libs.androidx.espresso.core)
     androidTestImplementation(platform(libs.androidx.compose.bom))
diff --git a/imagepicker/src/main/java/io/github/seunghee17/imagepicker/data/source/ImageFileDataSource.kt b/imagepicker/src/main/java/io/github/seunghee17/imagepicker/data/source/ImageFileDataSource.kt
index 8fe9544..7f2c6ba 100644
--- a/imagepicker/src/main/java/io/github/seunghee17/imagepicker/data/source/ImageFileDataSource.kt
+++ b/imagepicker/src/main/java/io/github/seunghee17/imagepicker/data/source/ImageFileDataSource.kt
@@ -230,7 +230,6 @@ internal class ImageFileDataSource(
 
     /**
      * 캐시 파일에 대한 content:// URI를 반환한다.
-     * file:// URI는 API 24+ 에서 앱 간 공유 시 FileUriExposedException을 유발하므로
      * FileProvider를 통해 content:// URI로 변환한다.
      */
     private fun uriForCacheFile(file: File): Uri {
diff --git a/imagepicker/src/main/java/io/github/seunghee17/imagepicker/domain/model/CropRect.kt b/imagepicker/src/main/java/io/github/seunghee17/imagepicker/domain/model/CropRect.kt
index e0355d6..55972e2 100644
--- a/imagepicker/src/main/java/io/github/seunghee17/imagepicker/domain/model/CropRect.kt
+++ b/imagepicker/src/main/java/io/github/seunghee17/imagepicker/domain/model/CropRect.kt
@@ -1,14 +1,18 @@
 package io.github.seunghee17.imagepicker
 
+import android.os.Parcelable
+import kotlinx.parcelize.Parcelize
+
 /**
  * 정규화된 크롭 영역. 모든 값은 이미지 크기 대비 [0f, 1f] 범위.
  */
+@Parcelize
 data class CropRect(
     val left: Float,
     val top: Float,
     val right: Float,
     val bottom: Float
-) {
+) : Parcelable {
     init {
         require(left >= 0f && top >= 0f && right <= 1f && bottom <= 1f) {
             "CropRect 값은 [0f, 1f] 범위 내에 있어야 합니다."
diff --git a/imagepicker/src/main/java/io/github/seunghee17/imagepicker/domain/model/PickedImage.kt b/imagepicker/src/main/java/io/github/seunghee17/imagepicker/domain/model/PickedImage.kt
index 185aaca..0e61e9e 100644
--- a/imagepicker/src/main/java/io/github/seunghee17/imagepicker/domain/model/PickedImage.kt
+++ b/imagepicker/src/main/java/io/github/seunghee17/imagepicker/domain/model/PickedImage.kt
@@ -1,8 +1,10 @@
 package io.github.seunghee17.imagepicker
 
 import android.net.Uri
-import io.github.seunghee17.imagepicker.CropRect
+import android.os.Parcelable
+import kotlinx.parcelize.Parcelize
 
+@Parcelize
 data class PickedImage(
     val originalUri: Uri,
     val editedUri: Uri? = null,
@@ -11,4 +13,4 @@ data class PickedImage(
     val isCropped: Boolean = cropRect != null,  // cropRect가 없어도 true로 명시 가능
     val isVideo: Boolean = false,
     val videoDurationMs: Long = 0L,     // isVideo == true 일 때만 유효 (밀리초)
-)
+) : Parcelable
diff --git a/imagepicker/src/main/java/io/github/seunghee17/imagepicker/presentation/gallery/GalleryContract.kt b/imagepicker/src/main/java/io/github/seunghee17/imagepicker/presentation/gallery/GalleryContract.kt
index ba90708..0e753a8 100644
--- a/imagepicker/src/main/java/io/github/seunghee17/imagepicker/presentation/gallery/GalleryContract.kt
+++ b/imagepicker/src/main/java/io/github/seunghee17/imagepicker/presentation/gallery/GalleryContract.kt
@@ -16,6 +16,7 @@ internal interface GalleryContract {
         val maxSelectionCount: Int = 10,
         val showAlbumSelector: Boolean = true,
         val editResults: Map<Long, PickedImage> = emptyMap(),
+        val isAlbumsLoading: Boolean = true,
     ) {
         val isSelectionLimitReached: Boolean
             get() = selectedImages.size >= maxSelectionCount
@@ -28,6 +29,9 @@ internal interface GalleryContract {
         data object Initialize : Intent
         data class SelectAlbum(val album: GalleryAlbum) : Intent
         data class ToggleImageSelection(val image: GalleryImage) : Intent
+        data class BeginDragSelection(val anchorImage: GalleryImage) : Intent
+        data class UpdateDragSelectionRange(val rangeImages: List<GalleryImage>) : Intent
+        data object EndDragSelection : Intent
         data class OnEditResult(val pickedImage: PickedImage) : Intent
         data object Confirm : Intent
         data object Cancel : Intent
diff --git a/imagepicker/src/main/java/io/github/seunghee17/imagepicker/presentation/gallery/GalleryScreen.kt b/imagepicker/src/main/java/io/github/seunghee17/imagepicker/presentation/gallery/GalleryScreen.kt
index 77178ed..634cbd2 100644
--- a/imagepicker/src/main/java/io/github/seunghee17/imagepicker/presentation/gallery/GalleryScreen.kt
+++ b/imagepicker/src/main/java/io/github/seunghee17/imagepicker/presentation/gallery/GalleryScreen.kt
@@ -41,12 +41,13 @@ import androidx.paging.compose.itemKey
 import io.github.seunghee17.imagepicker.domain.model.GalleryImage
 import io.github.seunghee17.imagepicker.presentation.component.TopBarWithCount
 import io.github.seunghee17.imagepicker.presentation.utils.DragSelectionState
-import io.github.seunghee17.imagepicker.presentation.utils.gridItemKeyAtPosition
+import io.github.seunghee17.imagepicker.presentation.utils.computeDragRange
+import io.github.seunghee17.imagepicker.presentation.utils.gridItemInfoAtPosition
 import io.github.seunghee17.imagepicker.presentation.utils.photoGridDragHandler
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.Flow
 
-/// 갤러리 이미지 그리드 화면 (권한이 허용된 상태에서 표시).
+/// 갤러리 이미지 화면 (권한이 허용된 상태에서 표시).
 
 @Composable
 internal fun GalleryScreen(
@@ -61,16 +62,15 @@ internal fun GalleryScreen(
     val gridState = rememberLazyGridState()
     val autoScrollSpeed = remember { mutableFloatStateOf(0f) }
     val currentDragState = remember { mutableStateOf<DragSelectionState?>(null) }
-    val currentState by rememberUpdatedState(state)
     var dropDownExpanded by rememberSaveable { mutableStateOf(false) }
 
     val pagingItems = pagingFlow.collectAsLazyPagingItems()
 
-    // 현재 로드된 아이템을 id → GalleryImage 맵으로 캐시 (드래그 선택 조회용)
-    val itemsById = remember(pagingItems.itemSnapshotList) {
-        pagingItems.itemSnapshotList.items.associateBy { it.id }
+    // grid 인덱스 순으로 정렬된, 현재 로드된 이미지 스냅샷 (드래그 range 선택 조회용)
+    val itemsSnapshot = remember(pagingItems.itemSnapshotList) {
+        pagingItems.itemSnapshotList.items
     }
-    val currentItemsById by rememberUpdatedState(itemsById)
+    val currentItemsSnapshot by rememberUpdatedState(itemsSnapshot)
 
     // 화면이 컴포지션을 떠날 때(에디터 진입 등) 잔여 스낵바 제거
     DisposableEffect(Unit) {
@@ -89,21 +89,22 @@ internal fun GalleryScreen(
         }
     }
 
-    // 드래그 중 autoScrollSpeed 값에 따라 그리드를 자동 스크롤
+    // 드래그 중 autoScrollSpeed 값에 따라 그리드를 자동 스크롤하면서, 손가락이 고정된 채로
+    // 그리드가 스크롤되어 새로운 아이템이 그 아래로 지나갈 때도 anchor~현재 위치 range를 계속 갱신
     LaunchedEffect(gridState) {
         snapshotFlow { autoScrollSpeed.floatValue }
             .collect { _ ->
                 while (autoScrollSpeed.floatValue != 0f) {
                     gridState.scrollBy(autoScrollSpeed.floatValue)
                     currentDragState.value?.let { dragState ->
-                        gridState.gridItemKeyAtPosition(dragState.offset)?.let { key ->
-                            if (dragState.lastProcessedKey != key &&
-                                currentState.selectedImages.none { it.id == key }
-                            ) {
-                                currentItemsById[key]?.let { image ->
-                                    onIntent(GalleryContract.Intent.ToggleImageSelection(image))
-                                    currentDragState.value = dragState.copy(lastProcessedKey = key)
-                                }
+                        gridState.gridItemInfoAtPosition(dragState.offset)?.let { info ->
+                            if (dragState.lastProcessedIndex != info.index) {
+                                onIntent(
+                                    GalleryContract.Intent.UpdateDragSelectionRange(
+                                        computeDragRange(dragState.anchorIndex, info.index, currentItemsSnapshot)
+                                    )
+                                )
+                                currentDragState.value = dragState.copy(lastProcessedIndex = info.index)
                             }
                         }
                     }
@@ -167,11 +168,15 @@ internal fun GalleryScreen(
                         .photoGridDragHandler(
                             lazyGridState = gridState,
                             haptics = LocalHapticFeedback.current,
-                            selectedImages = state.selectedImages,
-                            onSelect = { id ->
-                                currentItemsById[id]?.let { image ->
-                                    onIntent(GalleryContract.Intent.ToggleImageSelection(image))
-                                }
+                            imagesSnapshot = itemsSnapshot,
+                            onBeginDrag = { image ->
+                                onIntent(GalleryContract.Intent.BeginDragSelection(image))
+                            },
+                            onUpdateRange = { images ->
+                                onIntent(GalleryContract.Intent.UpdateDragSelectionRange(images))
+                            },
+                            onEndDrag = {
+                                onIntent(GalleryContract.Intent.EndDragSelection)
                             },
                             autoScrollSpeed = autoScrollSpeed,
                             autoScrollThreshold = with(LocalDensity.current) { 40.dp.toPx() },
diff --git a/imagepicker/src/main/java/io/github/seunghee17/imagepicker/presentation/gallery/GalleryScreenViewModel.kt b/imagepicker/src/main/java/io/github/seunghee17/imagepicker/presentation/gallery/GalleryScreenViewModel.kt
index 81489c9..eaf275c 100644
--- a/imagepicker/src/main/java/io/github/seunghee17/imagepicker/presentation/gallery/GalleryScreenViewModel.kt
+++ b/imagepicker/src/main/java/io/github/seunghee17/imagepicker/presentation/gallery/GalleryScreenViewModel.kt
@@ -18,9 +18,10 @@ import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.distinctUntilChanged
-import kotlinx.coroutines.flow.filterIsInstance
+import kotlinx.coroutines.flow.filter
 import kotlinx.coroutines.flow.flatMapLatest
 import kotlinx.coroutines.flow.launchIn
+import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.flow.receiveAsFlow
 import kotlinx.coroutines.flow.update
@@ -35,24 +36,6 @@ internal class GalleryScreenViewModel(
     showAlbumSelector: Boolean = true,
 ) : ViewModel() {
 
-    // 앨범 선택 상태: 아직 앨범 목록이 로드되지 않은 Pending vs 실제 선택된 Active
-    private sealed interface AlbumFilter {
-        data object Pending : AlbumFilter
-        data class Active(val albumId: String?) : AlbumFilter
-    }
-
-    private val _albumFilter = MutableStateFlow<AlbumFilter>(AlbumFilter.Pending)
-
-    /**
-     * 현재 선택된 앨범의 이미지를 페이지 단위로 방출하는 Flow.
-     * [GalleryScreen] 에서 [collectAsLazyPagingItems] 로 소비한다.
-     */
-    val pagingFlow: Flow<PagingData<GalleryImage>> = _albumFilter
-        .filterIsInstance<AlbumFilter.Active>()
-        .distinctUntilChanged()
-        .flatMapLatest { filter -> getPagedImages(filter.albumId) }
-        .cachedIn(viewModelScope)
-
     private val _state = MutableStateFlow(
         GalleryContract.State(
             maxSelectionCount = maxSelectionCount,
@@ -64,9 +47,22 @@ internal class GalleryScreenViewModel(
     private val _effect = Channel<GalleryContract.Effect>(Channel.BUFFERED)
     val effect = _effect.receiveAsFlow()
 
+
+    val pagingFlow: Flow<PagingData<GalleryImage>> = _state
+        .filter { !it.isAlbumsLoading }
+        .map { it.selectedAlbum?.id }
+        .distinctUntilChanged()
+        .flatMapLatest { albumId -> getPagedImages(albumId) }
+        .cachedIn(viewModelScope)
+
     private var albumsObserved = false
     private var pendingCacheClean = false
 
+    // 드래그 range 선택 중에만 쓰이는 임시 상태 (드래그 제스처 시작~종료 스코프)
+    private var dragBaseline: List<GalleryImage>? = null
+    private var dragIsDeselecting = false
+    private var dragLimitSnackbarShown = false
+
     fun handleIntent(intent: GalleryContract.Intent) {
         when (intent) {
             GalleryContract.Intent.Initialize -> {
@@ -76,11 +72,12 @@ internal class GalleryScreenViewModel(
                 }
                 observeAlbums()
             }
-            is GalleryContract.Intent.SelectAlbum -> {
+            is GalleryContract.Intent.SelectAlbum ->
                 _state.update { it.copy(selectedAlbum = intent.album) }
-                _albumFilter.value = AlbumFilter.Active(intent.album.id)
-            }
             is GalleryContract.Intent.ToggleImageSelection -> toggleSelection(intent.image)
+            is GalleryContract.Intent.BeginDragSelection -> beginDragSelection(intent.anchorImage)
+            is GalleryContract.Intent.UpdateDragSelectionRange -> updateDragSelectionRange(intent.rangeImages)
+            GalleryContract.Intent.EndDragSelection -> endDragSelection()
             is GalleryContract.Intent.OnEditResult -> applyEditResult(intent.pickedImage)
             GalleryContract.Intent.Confirm -> confirmSelection()
             GalleryContract.Intent.Cancel -> cancel()
@@ -93,13 +90,11 @@ internal class GalleryScreenViewModel(
         getAlbums()
             .onEach { albums ->
                 _state.update { current ->
-                    val selectedAlbum = current.selectedAlbum ?: albums.firstOrNull()
-                    current.copy(albums = albums, selectedAlbum = selectedAlbum)
-                }
-                val selectedAlbumId = _state.value.selectedAlbum?.id
-                val nextFilter = AlbumFilter.Active(selectedAlbumId)
-                if (_albumFilter.value != nextFilter) {
-                    _albumFilter.value = nextFilter
+                    current.copy(
+                        albums = albums,
+                        selectedAlbum = current.selectedAlbum ?: albums.firstOrNull(),
+                        isAlbumsLoading = false,
+                    )
                 }
             }
             .launchIn(viewModelScope)
@@ -125,6 +120,47 @@ internal class GalleryScreenViewModel(
         _state.update { it.copy(selectedImages = it.selectedImages + image) }
     }
 
+    // Google Photos 스타일 드래그 range 선택: 롱프레스한 anchor가 이미 선택되어 있었다면 해제 모드,
+    // 아니라면 선택 모드로 이번 드래그 제스처의 목표 동작을 고정한다.
+    private fun beginDragSelection(anchorImage: GalleryImage) {
+        val current = _state.value
+        dragBaseline = current.selectedImages
+        dragIsDeselecting = current.selectedImages.any { it.id == anchorImage.id }
+        dragLimitSnackbarShown = false
+    }
+
+    // anchor~현재 손가락 위치 사이의 range를 매번 baseline 기준으로 다시 계산한다.
+    // (증분 누적이 아니므로 손가락을 되돌리면 range 밖으로 나간 항목이 자동으로 원상복구된다)
+    private fun updateDragSelectionRange(rangeImages: List<GalleryImage>) {
+        val baseline = dragBaseline ?: return
+        val rangeIds = rangeImages.map { it.id }.toSet()
+
+        val desired = if (dragIsDeselecting) {
+            baseline.filter { it.id !in rangeIds }
+        } else {
+            baseline + rangeImages.filter { image -> baseline.none { it.id == image.id } }
+        }
+
+        val maxCount = _state.value.maxSelectionCount
+        if (desired.size > maxCount) {
+            _state.update { it.copy(selectedImages = desired.take(maxCount)) }
+            if (!dragLimitSnackbarShown) {
+                dragLimitSnackbarShown = true
+                viewModelScope.launch {
+                    _effect.send(GalleryContract.Effect.ShowSelectionLimitSnackbar(maxCount))
+                }
+            }
+        } else {
+            _state.update { it.copy(selectedImages = desired) }
+        }
+    }
+
+    private fun endDragSelection() {
+        dragBaseline = null
+        dragIsDeselecting = false
+        dragLimitSnackbarShown = false
+    }
+
     private fun applyEditResult(pickedImage: PickedImage) {
         _state.update { current ->
             val targetId = current.selectedImages
diff --git a/imagepicker/src/main/java/io/github/seunghee17/imagepicker/presentation/utils/Utils.kt b/imagepicker/src/main/java/io/github/seunghee17/imagepicker/presentation/utils/Utils.kt
index aae35de..23744fb 100644
--- a/imagepicker/src/main/java/io/github/seunghee17/imagepicker/presentation/utils/Utils.kt
+++ b/imagepicker/src/main/java/io/github/seunghee17/imagepicker/presentation/utils/Utils.kt
@@ -1,5 +1,6 @@
 package io.github.seunghee17.imagepicker.presentation.utils
 
+import androidx.compose.foundation.lazy.grid.LazyGridItemInfo
 import androidx.compose.foundation.lazy.grid.LazyGridState
 import androidx.compose.runtime.MutableState
 import androidx.compose.ui.Modifier
@@ -17,68 +18,85 @@ import io.github.seunghee17.imagepicker.domain.model.GalleryImage
 
 internal data class DragSelectionState(
     val offset: Offset,
-    val lastProcessedKey: Long?,
+    val anchorIndex: Int,
+    val lastProcessedIndex: Int?,
 )
 
 // 현재 터치한 좌표를 매개변수로 받는다
-// 이 아이템 영역 안에 현재 터치좌표가 들어가 있는가? 만약 찾은 아이템이 있다면 key 반환 없으면 null
-internal fun LazyGridState.gridItemKeyAtPosition(hitPoint: Offset): Long? =
+// 이 아이템 영역 안에 현재 터치좌표가 들어가 있는가? 만약 찾은 아이템이 있다면 그 아이템 정보(키/그리드 인덱스 포함) 반환, 없으면 null
+internal fun LazyGridState.gridItemInfoAtPosition(hitPoint: Offset): LazyGridItemInfo? =
     // 현재 화면에 보이는 아이템 정보 리스트
     layoutInfo.visibleItemsInfo.find { itemInfo ->
         itemInfo.size.toIntRect()
             .contains(hitPoint.round() - itemInfo.offset) // global 좌표를 item local 좌표로 변환
-    }?.key as? Long
+    }
+
+// anchor(드래그 시작 지점)와 current(현재 손가락 위치) 사이의 grid 선형 인덱스 범위를
+// 방향과 무관하게 오름차순(좌→우, 위→아래)으로 계산한다. 아직 로드되지 않은 인덱스는 건너뛴다.
+internal fun computeDragRange(
+    anchorIndex: Int,
+    currentIndex: Int,
+    images: List<GalleryImage>,
+): List<GalleryImage> {
+    val from = minOf(anchorIndex, currentIndex)
+    val to = maxOf(anchorIndex, currentIndex)
+    return (from..to).mapNotNull { images.getOrNull(it) }
+}
 
 internal fun Modifier.photoGridDragHandler(
     lazyGridState: LazyGridState,
     haptics: HapticFeedback,
-    selectedImages: List<GalleryImage>,
-    onSelect: (Long) -> Unit, // viewmodel에 정의한 사진 선택 콜백 주입하도록 수정
+    imagesSnapshot: List<GalleryImage>, // grid 인덱스 순으로 정렬된, 현재 로드된 이미지 스냅샷
+    onBeginDrag: (GalleryImage) -> Unit, // anchor로 선택된 이미지를 viewmodel에 알림 (선택/해제 모드 결정용)
+    onUpdateRange: (List<GalleryImage>) -> Unit, // anchor~현재 위치 range를 viewmodel에 알림
+    onEndDrag: () -> Unit, // 드래그 종료(취소 포함)를 viewmodel에 알림
     autoScrollSpeed: MutableState<Float>,
     autoScrollThreshold: Float,
-    currentDragState: MutableState<DragSelectionState?> // 자동 스크롤 중 중복 토글 방지를 위해 좌표와 마지막 처리 key를 함께 노출
+    currentDragState: MutableState<DragSelectionState?> // 자동 스크롤 중 range 재계산을 위해 anchor/좌표/마지막 처리 인덱스를 함께 노출
 ): Modifier = composed {
-    val currentSelectedImages by rememberUpdatedState(selectedImages)
-    val currentOnSelect by rememberUpdatedState(onSelect)
+    val currentImagesSnapshot by rememberUpdatedState(imagesSnapshot)
+    val currentOnBeginDrag by rememberUpdatedState(onBeginDrag)
+    val currentOnUpdateRange by rememberUpdatedState(onUpdateRange)
+    val currentOnEndDrag by rememberUpdatedState(onEndDrag)
 
     pointerInput(Unit) {
-        var initialKey: Long? = null
-        var currentKey: Long? = null
+        var anchorIndex: Int? = null
+        var lastProcessedIndex: Int? = null
 
         detectDragGesturesAfterLongPress(
             onDragStart = { offset ->
-                lazyGridState.gridItemKeyAtPosition(offset)?.let { key ->
-                    if (currentSelectedImages.none { it.id == key }) {
-                        // 새롭게 선택 상태 업데이트가 필요한 아이템
+                lazyGridState.gridItemInfoAtPosition(offset)?.let { info ->
+                    currentImagesSnapshot.getOrNull(info.index)?.let { image ->
                         haptics.performHapticFeedback(HapticFeedbackType.LongPress)
-                        initialKey = key
-                        currentKey = key
-                        currentOnSelect(key)
+                        anchorIndex = info.index
+                        lastProcessedIndex = info.index
+                        currentOnBeginDrag(image)
+                        currentOnUpdateRange(listOf(image))
                         currentDragState.value = DragSelectionState(
                             offset = offset,
-                            lastProcessedKey = key,
+                            anchorIndex = info.index,
+                            lastProcessedIndex = info.index,
                         )
                     }
                 }
             },
             onDragCancel = {
-                initialKey = null
-                currentKey = null
+                anchorIndex = null
+                lastProcessedIndex = null
                 autoScrollSpeed.value = 0f
                 currentDragState.value = null
+                currentOnEndDrag()
             },
             onDragEnd = {
-                initialKey = null
-                currentKey = null
+                anchorIndex = null
+                lastProcessedIndex = null
                 autoScrollSpeed.value = 0f
                 currentDragState.value = null
+                currentOnEndDrag()
             },
             onDrag = { change, _ ->
-                if (initialKey != null) {
-                    currentDragState.value = DragSelectionState(
-                        offset = change.position,
-                        lastProcessedKey = currentDragState.value?.lastProcessedKey,
-                    )
+                val anchor = anchorIndex
+                if (anchor != null) {
                     val distFromBottom =
                         lazyGridState.layoutInfo.viewportSize.height - change.position.y
                     val distFromTop = change.position.y
@@ -88,18 +106,19 @@ internal fun Modifier.photoGridDragHandler(
                         distFromTop < autoScrollThreshold -> -(autoScrollThreshold - distFromTop)
                         else -> 0f
                     }
-                    lazyGridState.gridItemKeyAtPosition(change.position)?.let { key ->
-                        if (currentKey != key && currentSelectedImages.none { it.id == key }) {
-                            currentOnSelect(key)
-                            currentKey = key
-                            currentDragState.value = DragSelectionState(
-                                offset = change.position,
-                                lastProcessedKey = key,
-                            )
-                        }
+                    val hitIndex = lazyGridState.gridItemInfoAtPosition(change.position)?.index
+                    if (hitIndex != null && hitIndex != lastProcessedIndex) {
+                        lastProcessedIndex = hitIndex
+                        currentOnUpdateRange(computeDragRange(anchor, hitIndex, currentImagesSnapshot))
                     }
+                    // autoscroll 폴링 루프가 이 좌표를 기준으로 계속 range를 재계산할 수 있도록 항상 최신 offset을 반영
+                    currentDragState.value = DragSelectionState(
+                        offset = change.position,
+                        anchorIndex = anchor,
+                        lastProcessedIndex = lastProcessedIndex,
+                    )
                 }
             }
         )
     }
-}
+}
\ No newline at end of file
diff --git a/imagepicker/src/test/java/io/github/seunghee17/imagepicker/ExampleUnitTest.kt b/imagepicker/src/test/java/io/github/seunghee17/imagepicker/ExampleUnitTest.kt
deleted file mode 100644
index 099cbec..0000000
--- a/imagepicker/src/test/java/io/github/seunghee17/imagepicker/ExampleUnitTest.kt
+++ /dev/null
@@ -1,17 +0,0 @@
-package io.github.seunghee17.imagepicker
-
-import org.junit.Test
-
-import org.junit.Assert.*
-
-/**
- * Example local unit test, which will execute on the development machine (host).
- *
- * See [testing documentation](http://d.android.com/tools/testing).
- */
-class ExampleUnitTest {
-    @Test
-    fun addition_isCorrect() {
-        assertEquals(4, 2 + 2)
-    }
-}
\ No newline at end of file
diff --git a/imagepicker/src/test/java/io/github/seunghee17/imagepicker/fake/FakeGalleryRepository.kt b/imagepicker/src/test/java/io/github/seunghee17/imagepicker/fake/FakeGalleryRepository.kt
new file mode 100644
index 0000000..30eaea5
--- /dev/null
+++ b/imagepicker/src/test/java/io/github/seunghee17/imagepicker/fake/FakeGalleryRepository.kt
@@ -0,0 +1,19 @@
+package io.github.seunghee17.imagepicker.fake
+
+import androidx.paging.PagingData
+import io.github.seunghee17.imagepicker.domain.model.GalleryAlbum
+import io.github.seunghee17.imagepicker.domain.model.GalleryImage
+import io.github.seunghee17.imagepicker.domain.repository.GalleryRepository
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.flowOf
+
+internal class FakeGalleryRepository : GalleryRepository {
+
+    val albums = MutableStateFlow<List<GalleryAlbum>>(emptyList())
+
+    override fun getAlbums(): Flow<List<GalleryAlbum>> = albums
+
+    override fun getPagedImages(albumId: String?): Flow<PagingData<GalleryImage>> =
+        flowOf(PagingData.empty())
+}
diff --git a/imagepicker/src/test/java/io/github/seunghee17/imagepicker/fake/FakeImageEditRepository.kt b/imagepicker/src/test/java/io/github/seunghee17/imagepicker/fake/FakeImageEditRepository.kt
new file mode 100644
index 0000000..8e46d42
--- /dev/null
+++ b/imagepicker/src/test/java/io/github/seunghee17/imagepicker/fake/FakeImageEditRepository.kt
@@ -0,0 +1,33 @@
+package io.github.seunghee17.imagepicker.fake
+
+import android.net.Uri
+import io.github.seunghee17.imagepicker.CropRect
+import io.github.seunghee17.imagepicker.domain.repository.ImageEditRepository
+
+internal class FakeImageEditRepository : ImageEditRepository {
+
+    var rotateResult: Uri? = null
+    var cropResult: Uri? = null
+    var rotateThrows: Boolean = false
+    var cropThrows: Boolean = false
+    var clearCacheCalled: Boolean = false
+
+    var lastRotateSourceUri: Uri? = null
+    var lastCropSourceUri: Uri? = null
+
+    override suspend fun rotateImage(sourceUri: Uri, degrees: Int): Uri {
+        lastRotateSourceUri = sourceUri
+        if (rotateThrows) throw RuntimeException("Rotate failed")
+        return rotateResult ?: sourceUri
+    }
+
+    override suspend fun cropImage(sourceUri: Uri, cropRect: CropRect): Uri {
+        lastCropSourceUri = sourceUri
+        if (cropThrows) throw RuntimeException("Crop failed")
+        return cropResult ?: sourceUri
+    }
+
+    override suspend fun clearEditCache() {
+        clearCacheCalled = true
+    }
+}
diff --git a/imagepicker/src/test/java/io/github/seunghee17/imagepicker/presentation/editor/EditorViewModelTest.kt b/imagepicker/src/test/java/io/github/seunghee17/imagepicker/presentation/editor/EditorViewModelTest.kt
new file mode 100644
index 0000000..83f5095
--- /dev/null
+++ b/imagepicker/src/test/java/io/github/seunghee17/imagepicker/presentation/editor/EditorViewModelTest.kt
@@ -0,0 +1,239 @@
+package io.github.seunghee17.imagepicker.presentation.editor
+
+import android.net.Uri
+import app.cash.turbine.test
+import io.github.seunghee17.imagepicker.CropRect
+import io.github.seunghee17.imagepicker.domain.usecase.CropImageUseCase
+import io.github.seunghee17.imagepicker.domain.usecase.RotateImageUseCase
+import io.github.seunghee17.imagepicker.fake.FakeImageEditRepository
+import io.github.seunghee17.imagepicker.util.MainDispatcherRule
+import io.mockk.mockk
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.runTest
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Rule
+import org.junit.Test
+import kotlin.test.assertIs
+
+@OptIn(ExperimentalCoroutinesApi::class)
+class EditorViewModelTest {
+
+    @get:Rule
+    val mainDispatcherRule = MainDispatcherRule()
+
+    private val originalUri: Uri = mockk(relaxed = true)
+
+    private fun createVm(repo: FakeImageEditRepository = FakeImageEditRepository()): EditorViewModel =
+        EditorViewModel(
+            originalUri = originalUri,
+            rotateImage = RotateImageUseCase(repo),
+            cropImage = CropImageUseCase(repo),
+        )
+
+    // ─────────────────────────────────────────────────────────────────────────
+    // Rotate state update
+    // ─────────────────────────────────────────────────────────────────────────
+
+    @Test
+    fun `RotateClockwise updates previewUri to rotated result`() = runTest {
+        val rotatedUri = mockk<Uri>(relaxed = true)
+        val repo = FakeImageEditRepository().apply { rotateResult = rotatedUri }
+        val vm = createVm(repo)
+
+        vm.handleIntent(EditorContract.Intent.RotateClockwise)
+
+        assertEquals(rotatedUri, vm.state.value.previewUri)
+    }
+
+    @Test
+    fun `totalRotation wraps to 0 after four rotations`() = runTest {
+        val vm = createVm()
+        repeat(4) { vm.handleIntent(EditorContract.Intent.RotateClockwise) }
+        assertEquals(0, vm.state.value.totalRotation)
+    }
+
+    @Test
+    fun `rotate failure emits ShowError effect`() = runTest {
+        val repo = FakeImageEditRepository().apply { rotateThrows = true }
+        val vm = createVm(repo)
+
+        vm.effect.test {
+            vm.handleIntent(EditorContract.Intent.RotateClockwise)
+            assertIs<EditorContract.Effect.ShowError>(awaitItem())
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────
+    // Crop state commit
+    // ─────────────────────────────────────────────────────────────────────────
+
+    @Test
+    fun `ApplyCrop updates committedUri and previewUri to cropped result`() = runTest {
+        val croppedUri = mockk<Uri>(relaxed = true)
+        val repo = FakeImageEditRepository().apply { cropResult = croppedUri }
+        val vm = createVm(repo)
+
+        vm.handleIntent(EditorContract.Intent.EnterCropMode)
+        vm.handleIntent(EditorContract.Intent.ApplyCrop)
+
+        assertEquals(croppedUri, vm.state.value.committedUri)
+        assertEquals(croppedUri, vm.state.value.previewUri)
+    }
+
+    @Test
+    fun `ApplyCrop resets pendingRotation to 0`() = runTest {
+        val vm = createVm()
+        vm.handleIntent(EditorContract.Intent.RotateClockwise) // pendingRotation = 90
+        vm.handleIntent(EditorContract.Intent.EnterCropMode)
+        vm.handleIntent(EditorContract.Intent.ApplyCrop)
+
+        assertEquals(0, vm.state.value.pendingRotation)
+    }
+
+    @Test
+    fun `ApplyCrop resets cropRect to FULL`() = runTest {
+        val vm = createVm()
+        vm.handleIntent(
+            EditorContract.Intent.UpdateCropRect(CropRect(0.1f, 0.1f, 0.9f, 0.9f))
+        )
+        vm.handleIntent(EditorContract.Intent.EnterCropMode)
+        vm.handleIntent(EditorContract.Intent.ApplyCrop)
+
+        assertEquals(CropRect.FULL, vm.state.value.cropRect)
+    }
+
+    @Test
+    fun `ExitCropMode restores cropRect to value on enter`() = runTest {
+        val vm = createVm()
+        val rect = CropRect(0.2f, 0.2f, 0.8f, 0.8f)
+        vm.handleIntent(EditorContract.Intent.UpdateCropRect(rect))
+        vm.handleIntent(EditorContract.Intent.EnterCropMode)   // saves rect as cropRectOnEnter
+        vm.handleIntent(EditorContract.Intent.UpdateCropRect(CropRect(0.5f, 0.5f, 0.9f, 0.9f)))
+        vm.handleIntent(EditorContract.Intent.ExitCropMode)
+
+        assertEquals(rect, vm.state.value.cropRect)
+    }
+
+    @Test
+    fun `crop failure emits ShowError effect`() = runTest {
+        val repo = FakeImageEditRepository().apply { cropThrows = true }
+        val vm = createVm(repo)
+        vm.handleIntent(EditorContract.Intent.EnterCropMode)
+
+        vm.effect.test {
+            vm.handleIntent(EditorContract.Intent.ApplyCrop)
+            assertIs<EditorContract.Effect.ShowError>(awaitItem())
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────
+    // Combined scenarios: rotate ↔ crop ordering
+    // ─────────────────────────────────────────────────────────────────────────
+
+    @Test
+    fun `rotate then crop uses rotated uri as crop source`() = runTest {
+        val rotatedUri = mockk<Uri>(relaxed = true)
+        val repo = FakeImageEditRepository().apply { rotateResult = rotatedUri }
+        val vm = createVm(repo)
+
+        vm.handleIntent(EditorContract.Intent.RotateClockwise)
+        vm.handleIntent(EditorContract.Intent.EnterCropMode)
+        vm.handleIntent(EditorContract.Intent.ApplyCrop)
+
+        // cropImage must receive the rotated uri, not originalUri
+        assertEquals(rotatedUri, repo.lastCropSourceUri)
+        assertEquals(0, vm.state.value.pendingRotation)
+    }
+
+    @Test
+    fun `crop then rotate uses cropped uri as rotate source`() = runTest {
+        val croppedUri = mockk<Uri>(relaxed = true)
+        val repo = FakeImageEditRepository().apply { cropResult = croppedUri }
+        val vm = createVm(repo)
+
+        vm.handleIntent(EditorContract.Intent.EnterCropMode)
+        vm.handleIntent(EditorContract.Intent.ApplyCrop)
+        vm.handleIntent(EditorContract.Intent.RotateClockwise)
+
+        // rotateImage must receive the cropped uri, not originalUri
+        assertEquals(croppedUri, repo.lastRotateSourceUri)
+    }
+
+    @Test
+    fun `rotate then crop then save returns crop result as editedUri`() = runTest {
+        val rotatedUri = mockk<Uri>(relaxed = true)
+        val croppedUri = mockk<Uri>(relaxed = true)
+        val repo = FakeImageEditRepository().apply {
+            rotateResult = rotatedUri
+            cropResult = croppedUri
+        }
+        val vm = createVm(repo)
+
+        vm.handleIntent(EditorContract.Intent.RotateClockwise)
+        vm.handleIntent(EditorContract.Intent.EnterCropMode)
+        vm.handleIntent(EditorContract.Intent.ApplyCrop)
+
+        vm.effect.test {
+            vm.handleIntent(EditorContract.Intent.SaveAndReturn)
+            val item = awaitItem() as EditorContract.Effect.ReturnEditedImage
+            assertEquals(originalUri, item.pickedImage.originalUri)
+            assertEquals(croppedUri, item.pickedImage.editedUri)
+            assertEquals(90, item.pickedImage.rotationDegrees)
+            assertTrue(item.pickedImage.isCropped)
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────
+    // Save result correctness
+    // ─────────────────────────────────────────────────────────────────────────
+
+    @Test
+    fun `SaveAndReturn with no edits returns null editedUri`() = runTest {
+        val vm = createVm()
+
+        vm.effect.test {
+            vm.handleIntent(EditorContract.Intent.SaveAndReturn)
+            val item = awaitItem() as EditorContract.Effect.ReturnEditedImage
+            assertNull(item.pickedImage.editedUri)
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
+    @Test
+    fun `SaveAndReturn after rotate returns editedUri and correct rotationDegrees`() = runTest {
+        val rotatedUri = mockk<Uri>(relaxed = true)
+        val repo = FakeImageEditRepository().apply { rotateResult = rotatedUri }
+        val vm = createVm(repo)
+        vm.handleIntent(EditorContract.Intent.RotateClockwise)
+
+        vm.effect.test {
+            vm.handleIntent(EditorContract.Intent.SaveAndReturn)
+            val item = awaitItem() as EditorContract.Effect.ReturnEditedImage
+            assertEquals(originalUri, item.pickedImage.originalUri)
+            assertEquals(rotatedUri, item.pickedImage.editedUri)
+            assertEquals(90, item.pickedImage.rotationDegrees)
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
+    @Test
+    fun `SaveAndReturn after crop sets isCropped`() = runTest {
+        val croppedUri = mockk<Uri>(relaxed = true)
+        val repo = FakeImageEditRepository().apply { cropResult = croppedUri }
+        val vm = createVm(repo)
+        vm.handleIntent(EditorContract.Intent.EnterCropMode)
+        vm.handleIntent(EditorContract.Intent.ApplyCrop)
+
+        vm.effect.test {
+            vm.handleIntent(EditorContract.Intent.SaveAndReturn)
+            val item = awaitItem() as EditorContract.Effect.ReturnEditedImage
+            assertTrue(item.pickedImage.isCropped)
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+}
diff --git a/imagepicker/src/test/java/io/github/seunghee17/imagepicker/presentation/gallery/GalleryScreenViewModelTest.kt b/imagepicker/src/test/java/io/github/seunghee17/imagepicker/presentation/gallery/GalleryScreenViewModelTest.kt
new file mode 100644
index 0000000..33edf18
--- /dev/null
+++ b/imagepicker/src/test/java/io/github/seunghee17/imagepicker/presentation/gallery/GalleryScreenViewModelTest.kt
@@ -0,0 +1,409 @@
+package io.github.seunghee17.imagepicker.presentation.gallery
+
+import android.net.Uri
+import app.cash.turbine.test
+import io.github.seunghee17.imagepicker.PickedImage
+import io.github.seunghee17.imagepicker.domain.model.GalleryAlbum
+import io.github.seunghee17.imagepicker.domain.model.GalleryImage
+import io.github.seunghee17.imagepicker.domain.model.MediaType
+import io.github.seunghee17.imagepicker.domain.usecase.ClearEditCacheUseCase
+import io.github.seunghee17.imagepicker.domain.usecase.GetGalleryAlbumsUseCase
+import io.github.seunghee17.imagepicker.domain.usecase.GetPagedImagesUseCase
+import io.github.seunghee17.imagepicker.fake.FakeGalleryRepository
+import io.github.seunghee17.imagepicker.fake.FakeImageEditRepository
+import io.github.seunghee17.imagepicker.util.MainDispatcherRule
+import io.mockk.mockk
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.runTest
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Rule
+import org.junit.Test
+import kotlin.test.assertIs
+
+@OptIn(ExperimentalCoroutinesApi::class)
+class GalleryScreenViewModelTest {
+
+    @get:Rule
+    val mainDispatcherRule = MainDispatcherRule()
+
+    private fun fakeImage(id: Long): GalleryImage = GalleryImage(
+        id = id,
+        uri = mockk(relaxed = true),
+        displayName = "image_$id.jpg",
+        dateTaken = 0L,
+        albumId = "album1",
+        albumName = "Camera",
+        width = 100,
+        height = 100,
+        mimeType = "image/jpeg",
+        mediaType = MediaType.IMAGE,
+    )
+
+    private fun fakeAlbum(id: String, name: String): GalleryAlbum = GalleryAlbum(
+        id = id,
+        name = name,
+        coverUri = mockk(relaxed = true),
+        count = 1,
+    )
+
+    private fun createVm(
+        maxSelectionCount: Int = 10,
+        fakeGallery: FakeGalleryRepository = FakeGalleryRepository(),
+    ): GalleryScreenViewModel = GalleryScreenViewModel(
+        getAlbums = GetGalleryAlbumsUseCase(fakeGallery),
+        getPagedImages = GetPagedImagesUseCase(fakeGallery),
+        clearEditCache = ClearEditCacheUseCase(FakeImageEditRepository()),
+        maxSelectionCount = maxSelectionCount,
+    )
+
+    // ─────────────────────────────────────────────────────────────────────────
+    // Album loading state
+    // ─────────────────────────────────────────────────────────────────────────
+
+    @Test
+    fun `isAlbumsLoading is true in initial state`() = runTest {
+        val vm = createVm()
+        assertTrue(vm.state.value.isAlbumsLoading)
+    }
+
+    @Test
+    fun `isAlbumsLoading becomes false after first album emission`() = runTest {
+        val fakeGallery = FakeGalleryRepository()
+        val vm = createVm(fakeGallery = fakeGallery)
+        vm.handleIntent(GalleryContract.Intent.Initialize)
+
+        fakeGallery.albums.value = listOf(fakeAlbum("1", "Camera"))
+
+        assertFalse(vm.state.value.isAlbumsLoading)
+    }
+
+    @Test
+    fun `first album in list becomes selectedAlbum when none was pre-selected`() = runTest {
+        val fakeGallery = FakeGalleryRepository()
+        val vm = createVm(fakeGallery = fakeGallery)
+        val album = fakeAlbum("1", "Camera")
+        vm.handleIntent(GalleryContract.Intent.Initialize)
+
+        fakeGallery.albums.value = listOf(album)
+
+        assertEquals(album, vm.state.value.selectedAlbum)
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────
+    // Album switching safety
+    // ─────────────────────────────────────────────────────────────────────────
+
+    @Test
+    fun `rapid album switching keeps only last selection`() = runTest {
+        val fakeGallery = FakeGalleryRepository()
+        val vm = createVm(fakeGallery = fakeGallery)
+        val album1 = fakeAlbum("1", "Camera")
+        val album2 = fakeAlbum("2", "Downloads")
+        val album3 = fakeAlbum("3", "Screenshots")
+        vm.handleIntent(GalleryContract.Intent.Initialize)
+        fakeGallery.albums.value = listOf(album1, album2, album3)
+
+        vm.handleIntent(GalleryContract.Intent.SelectAlbum(album1))
+        vm.handleIntent(GalleryContract.Intent.SelectAlbum(album2))
+        vm.handleIntent(GalleryContract.Intent.SelectAlbum(album3))
+
+        assertEquals(album3, vm.state.value.selectedAlbum)
+    }
+
+    @Test
+    fun `album list refresh does not overwrite user album selection`() = runTest {
+        val fakeGallery = FakeGalleryRepository()
+        val vm = createVm(fakeGallery = fakeGallery)
+        val album1 = fakeAlbum("1", "Camera")
+        val album2 = fakeAlbum("2", "Downloads")
+        vm.handleIntent(GalleryContract.Intent.Initialize)
+        fakeGallery.albums.value = listOf(album1, album2)
+
+        vm.handleIntent(GalleryContract.Intent.SelectAlbum(album2))
+        assertEquals(album2, vm.state.value.selectedAlbum)
+
+        // MediaStore 갱신으로 앨범 목록이 다시 방출되어도 사용자 선택이 유지돼야 한다
+        fakeGallery.albums.value = listOf(album1, album2)
+
+        assertEquals(album2, vm.state.value.selectedAlbum)
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────
+    // Selection toggle
+    // ─────────────────────────────────────────────────────────────────────────
+
+    @Test
+    fun `toggling unselected image adds it to selectedImages`() = runTest {
+        val vm = createVm()
+        val image = fakeImage(1)
+
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(image))
+
+        assertEquals(listOf(image), vm.state.value.selectedImages)
+    }
+
+    @Test
+    fun `toggling already selected image removes it from selectedImages`() = runTest {
+        val vm = createVm()
+        val image = fakeImage(1)
+
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(image))
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(image))
+
+        assertTrue(vm.state.value.selectedImages.isEmpty())
+    }
+
+    @Test
+    fun `selectionOrderMap reflects insertion order`() = runTest {
+        val vm = createVm()
+        val image1 = fakeImage(1)
+        val image2 = fakeImage(2)
+
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(image1))
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(image2))
+
+        assertEquals(1, vm.state.value.selectionOrderMap[1L])
+        assertEquals(2, vm.state.value.selectionOrderMap[2L])
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────
+    // Max selection enforcement
+    // ─────────────────────────────────────────────────────────────────────────
+
+    @Test
+    fun `selecting beyond limit emits ShowSelectionLimitSnackbar`() = runTest {
+        val vm = createVm(maxSelectionCount = 2)
+
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(fakeImage(1)))
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(fakeImage(2)))
+
+        vm.effect.test {
+            vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(fakeImage(3)))
+            val item = awaitItem()
+            assertIs<GalleryContract.Effect.ShowSelectionLimitSnackbar>(item)
+            assertEquals(2, item.maxSelectionCount)
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
+    @Test
+    fun `image beyond limit is not added to selectedImages`() = runTest {
+        val vm = createVm(maxSelectionCount = 2)
+
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(fakeImage(1)))
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(fakeImage(2)))
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(fakeImage(3)))
+
+        assertEquals(2, vm.state.value.selectedImages.size)
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────
+    // Drag range selection (anchor~current, Google Photos style)
+    // ─────────────────────────────────────────────────────────────────────────
+
+    @Test
+    fun `dragging over a row selects the whole range in grid order`() = runTest {
+        val vm = createVm()
+        val images = (1..7L).map { fakeImage(it) }
+
+        vm.handleIntent(GalleryContract.Intent.BeginDragSelection(images[1])) // index 1
+        vm.handleIntent(GalleryContract.Intent.UpdateDragSelectionRange(images.subList(1, 7))) // index 1..6
+
+        assertEquals(images.subList(1, 7), vm.state.value.selectedImages)
+    }
+
+    @Test
+    fun `reversing drag direction shrinks the range back to baseline`() = runTest {
+        val vm = createVm()
+        val images = (1..7L).map { fakeImage(it) }
+
+        vm.handleIntent(GalleryContract.Intent.BeginDragSelection(images[1]))
+        vm.handleIntent(GalleryContract.Intent.UpdateDragSelectionRange(images.subList(1, 7)))
+        // 손가락을 되돌려 anchor~index3 까지만 남김
+        vm.handleIntent(GalleryContract.Intent.UpdateDragSelectionRange(images.subList(1, 4)))
+
+        assertEquals(images.subList(1, 4), vm.state.value.selectedImages)
+    }
+
+    @Test
+    fun `pre-existing tap selections outside the range are preserved during select-mode drag`() = runTest {
+        val vm = createVm()
+        val tapped = fakeImage(100)
+        val images = (1..7L).map { fakeImage(it) }
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(tapped))
+
+        vm.handleIntent(GalleryContract.Intent.BeginDragSelection(images[1]))
+        vm.handleIntent(GalleryContract.Intent.UpdateDragSelectionRange(images.subList(1, 4)))
+
+        assertTrue(vm.state.value.selectedImages.containsAll(images.subList(1, 4)))
+        assertTrue(vm.state.value.selectedImages.contains(tapped))
+    }
+
+    @Test
+    fun `long-pressing an already-selected image enters drag-deselect mode`() = runTest {
+        val vm = createVm()
+        val images = (1..7L).map { fakeImage(it) }
+        images.forEach { vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(it)) }
+
+        vm.handleIntent(GalleryContract.Intent.BeginDragSelection(images[1]))
+        vm.handleIntent(GalleryContract.Intent.UpdateDragSelectionRange(images.subList(1, 4)))
+
+        assertEquals(
+            listOf(images[0]) + images.subList(4, 7),
+            vm.state.value.selectedImages,
+        )
+    }
+
+    @Test
+    fun `drag-deselect removes range items even if pre-existing outside this drag`() = runTest {
+        val vm = createVm()
+        val images = (1..20L).map { fakeImage(it) }
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(images[4])) // id=5
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(images[19])) // id=20
+
+        vm.handleIntent(GalleryContract.Intent.BeginDragSelection(images[4]))
+        vm.handleIntent(
+            GalleryContract.Intent.UpdateDragSelectionRange(images.subList(4, 20))
+        )
+
+        assertTrue(vm.state.value.selectedImages.isEmpty())
+    }
+
+    @Test
+    fun `range selection beyond max fills up to the limit and emits snackbar once`() = runTest {
+        val vm = createVm(maxSelectionCount = 10)
+        val images = (1..20L).map { fakeImage(it) }
+        images.subList(0, 8).forEach { vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(it)) }
+
+        vm.handleIntent(GalleryContract.Intent.BeginDragSelection(images[8]))
+        vm.effect.test {
+            vm.handleIntent(GalleryContract.Intent.UpdateDragSelectionRange(images.subList(8, 11)))
+            val item = awaitItem()
+            assertIs<GalleryContract.Effect.ShowSelectionLimitSnackbar>(item)
+            // 다음 tick에서도 계속 초과 상태라면 스낵바를 다시 보내지 않는다
+            vm.handleIntent(GalleryContract.Intent.UpdateDragSelectionRange(images.subList(8, 12)))
+            expectNoEvents()
+            cancelAndIgnoreRemainingEvents()
+        }
+        assertEquals(10, vm.state.value.selectedImages.size)
+    }
+
+    @Test
+    fun `ending drag selection allows a fresh drag gesture to start its own baseline`() = runTest {
+        val vm = createVm()
+        val images = (1..7L).map { fakeImage(it) }
+
+        vm.handleIntent(GalleryContract.Intent.BeginDragSelection(images[1]))
+        vm.handleIntent(GalleryContract.Intent.UpdateDragSelectionRange(images.subList(1, 4)))
+        vm.handleIntent(GalleryContract.Intent.EndDragSelection)
+
+        vm.handleIntent(GalleryContract.Intent.BeginDragSelection(images[4]))
+        vm.handleIntent(GalleryContract.Intent.UpdateDragSelectionRange(images.subList(4, 6)))
+
+        assertEquals(images.subList(1, 4) + images.subList(4, 6), vm.state.value.selectedImages)
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────
+    // Confirm result composition
+    // ─────────────────────────────────────────────────────────────────────────
+
+    @Test
+    fun `Confirm emits SelectionConfirmed with selected images`() = runTest {
+        val vm = createVm()
+        val image = fakeImage(1)
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(image))
+
+        vm.effect.test {
+            vm.handleIntent(GalleryContract.Intent.Confirm)
+            val item = awaitItem()
+            assertIs<GalleryContract.Effect.SelectionConfirmed>(item)
+            assertEquals(1, item.result.items.size)
+            assertEquals(image.uri, item.result.items[0].originalUri)
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
+    @Test
+    fun `Confirm resets selectedImages`() = runTest {
+        val vm = createVm()
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(fakeImage(1)))
+        vm.handleIntent(GalleryContract.Intent.Confirm)
+
+        assertTrue(vm.state.value.selectedImages.isEmpty())
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────
+    // Cancel
+    // ─────────────────────────────────────────────────────────────────────────
+
+    @Test
+    fun `Cancel resets selectedImages and editResults`() = runTest {
+        val vm = createVm()
+        val image = fakeImage(1)
+        val editedUri = mockk<Uri>(relaxed = true)
+
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(image))
+        vm.handleIntent(
+            GalleryContract.Intent.OnEditResult(
+                PickedImage(originalUri = image.uri, editedUri = editedUri)
+            )
+        )
+
+        vm.handleIntent(GalleryContract.Intent.Cancel)
+
+        assertTrue(vm.state.value.selectedImages.isEmpty())
+        assertTrue(vm.state.value.editResults.isEmpty())
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────
+    // Edit result merge
+    // ─────────────────────────────────────────────────────────────────────────
+
+    @Test
+    fun `edit result is merged into confirm result`() = runTest {
+        val vm = createVm()
+        val image = fakeImage(1)
+        val editedUri = mockk<Uri>(relaxed = true)
+        val pickedImage = PickedImage(
+            originalUri = image.uri,
+            editedUri = editedUri,
+            rotationDegrees = 90,
+        )
+
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(image))
+        vm.handleIntent(GalleryContract.Intent.OnEditResult(pickedImage))
+
+        vm.effect.test {
+            vm.handleIntent(GalleryContract.Intent.Confirm)
+            val item = awaitItem() as GalleryContract.Effect.SelectionConfirmed
+            val result = item.result.items[0]
+            assertEquals(editedUri, result.editedUri)
+            assertEquals(90, result.rotationDegrees)
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
+    @Test
+    fun `edit result for non-selected image is ignored`() = runTest {
+        val vm = createVm()
+        val selectedImage = fakeImage(1)
+        val unrelatedImage = fakeImage(99)
+
+        vm.handleIntent(GalleryContract.Intent.ToggleImageSelection(selectedImage))
+        vm.handleIntent(
+            GalleryContract.Intent.OnEditResult(
+                PickedImage(originalUri = unrelatedImage.uri, rotationDegrees = 90)
+            )
+        )
+
+        vm.effect.test {
+            vm.handleIntent(GalleryContract.Intent.Confirm)
+            val item = awaitItem() as GalleryContract.Effect.SelectionConfirmed
+            assertNull(item.result.items[0].editedUri)
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+}
diff --git a/imagepicker/src/test/java/io/github/seunghee17/imagepicker/presentation/picker/ImagePickerViewModelTest.kt b/imagepicker/src/test/java/io/github/seunghee17/imagepicker/presentation/picker/ImagePickerViewModelTest.kt
new file mode 100644
index 0000000..dd1b421
--- /dev/null
+++ b/imagepicker/src/test/java/io/github/seunghee17/imagepicker/presentation/picker/ImagePickerViewModelTest.kt
@@ -0,0 +1,152 @@
+package io.github.seunghee17.imagepicker.presentation.picker
+
+import app.cash.turbine.test
+import io.github.seunghee17.imagepicker.domain.model.PermissionStatus
+import io.github.seunghee17.imagepicker.util.MainDispatcherRule
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.runTest
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Rule
+import org.junit.Test
+import kotlin.test.assertIs
+
+@OptIn(ExperimentalCoroutinesApi::class)
+class ImagePickerViewModelTest {
+
+    @get:Rule
+    val mainDispatcherRule = MainDispatcherRule()
+
+    // ─────────────────────────────────────────────────────────────────────────
+    // Initialize
+    // ─────────────────────────────────────────────────────────────────────────
+
+    // ─────────────────────────────────────────────────────────────────────────
+    // PARTIALLY_GRANTED flow
+    // ─────────────────────────────────────────────────────────────────────────
+
+    @Test
+    fun `PARTIALLY_GRANTED on INITIAL sends RequestPermission and marks flag`() = runTest {
+        val vm = ImagePickerViewModel()
+        vm.effect.test {
+            vm.handleIntent(
+                ImagePickerContract.Intent.OnPermissionEvaluated(
+                    PermissionStatus.PARTIALLY_GRANTED,
+                    ImagePickerContract.PermissionCheckSource.INITIAL,
+                )
+            )
+            assertIs<ImagePickerContract.Effect.RequestPermission>(awaitItem())
+            assertTrue(vm.state.value.hasRequestedFullAccessAfterPartial)
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
+    @Test
+    fun `PARTIALLY_GRANTED on RESUME does not send any effect`() = runTest {
+        val vm = ImagePickerViewModel()
+        vm.effect.test {
+            vm.handleIntent(
+                ImagePickerContract.Intent.OnPermissionEvaluated(
+                    PermissionStatus.PARTIALLY_GRANTED,
+                    ImagePickerContract.PermissionCheckSource.RESUME,
+                )
+            )
+            expectNoEvents()
+            assertEquals(PermissionStatus.PARTIALLY_GRANTED, vm.state.value.permissionStatus)
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
+    @Test
+    fun `PARTIALLY_GRANTED second time does not send RequestPermission again`() = runTest {
+        val vm = ImagePickerViewModel()
+        vm.effect.test {
+            // First evaluation sets the flag and emits RequestPermission
+            vm.handleIntent(
+                ImagePickerContract.Intent.OnPermissionEvaluated(
+                    PermissionStatus.PARTIALLY_GRANTED,
+                    ImagePickerContract.PermissionCheckSource.INITIAL,
+                )
+            )
+            assertIs<ImagePickerContract.Effect.RequestPermission>(awaitItem())
+            assertTrue(vm.state.value.hasRequestedFullAccessAfterPartial)
+
+            // Second evaluation: flag already set, should produce no effect
+            vm.handleIntent(
+                ImagePickerContract.Intent.OnPermissionEvaluated(
+                    PermissionStatus.PARTIALLY_GRANTED,
+                    ImagePickerContract.PermissionCheckSource.PERMISSION_RESULT,
+                )
+            )
+            expectNoEvents()
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────
+    // PERMANENTLY_DENIED → settings navigation
+    // ─────────────────────────────────────────────────────────────────────────
+
+    @Test
+    fun `PERMANENTLY_DENIED on PERMISSION_RESULT sends NavigateToSettings`() = runTest {
+        val vm = ImagePickerViewModel()
+        vm.effect.test {
+            vm.handleIntent(
+                ImagePickerContract.Intent.OnPermissionEvaluated(
+                    PermissionStatus.PERMANENTLY_DENIED,
+                    ImagePickerContract.PermissionCheckSource.PERMISSION_RESULT,
+                )
+            )
+            assertIs<ImagePickerContract.Effect.NavigateToSettings>(awaitItem())
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
+    @Test
+    fun `PERMANENTLY_DENIED on INITIAL does not send NavigateToSettings`() = runTest {
+        val vm = ImagePickerViewModel()
+        vm.effect.test {
+            vm.handleIntent(
+                ImagePickerContract.Intent.OnPermissionEvaluated(
+                    PermissionStatus.PERMANENTLY_DENIED,
+                    ImagePickerContract.PermissionCheckSource.INITIAL,
+                )
+            )
+            expectNoEvents()
+            assertEquals(PermissionStatus.PERMANENTLY_DENIED, vm.state.value.permissionStatus)
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
+    // ─────────────────────────────────────────────────────────────────────────
+    // GRANTED
+    // ─────────────────────────────────────────────────────────────────────────
+
+    @Test
+    fun `GRANTED resets hasRequestedFullAccessAfterPartial flag`() = runTest {
+        val vm = ImagePickerViewModel()
+        vm.effect.test {
+            // Set flag via partial grant
+            vm.handleIntent(
+                ImagePickerContract.Intent.OnPermissionEvaluated(
+                    PermissionStatus.PARTIALLY_GRANTED,
+                    ImagePickerContract.PermissionCheckSource.INITIAL,
+                )
+            )
+            awaitItem() // consume RequestPermission effect
+            assertTrue(vm.state.value.hasRequestedFullAccessAfterPartial)
+
+            // Full grant should reset the flag
+            vm.handleIntent(
+                ImagePickerContract.Intent.OnPermissionEvaluated(
+                    PermissionStatus.GRANTED,
+                    ImagePickerContract.PermissionCheckSource.PERMISSION_RESULT,
+                )
+            )
+            assertEquals(PermissionStatus.GRANTED, vm.state.value.permissionStatus)
+            assertFalse(vm.state.value.hasRequestedFullAccessAfterPartial)
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+}
diff --git a/imagepicker/src/test/java/io/github/seunghee17/imagepicker/util/MainDispatcherRule.kt b/imagepicker/src/test/java/io/github/seunghee17/imagepicker/util/MainDispatcherRule.kt
new file mode 100644
index 0000000..79f6a56
--- /dev/null
+++ b/imagepicker/src/test/java/io/github/seunghee17/imagepicker/util/MainDispatcherRule.kt
@@ -0,0 +1,23 @@
+package io.github.seunghee17.imagepicker.util
+
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.TestDispatcher
+import kotlinx.coroutines.test.UnconfinedTestDispatcher
+import kotlinx.coroutines.test.resetMain
+import kotlinx.coroutines.test.setMain
+import org.junit.rules.TestWatcher
+import org.junit.runner.Description
+
+@OptIn(ExperimentalCoroutinesApi::class)
+class MainDispatcherRule(
+    val testDispatcher: TestDispatcher = UnconfinedTestDispatcher(),
+) : TestWatcher() {
+    override fun starting(description: Description) {
+        Dispatchers.setMain(testDispatcher)
+    }
+
+    override fun finished(description: Description) {
+        Dispatchers.resetMain()
+    }
+}