refactor: migrate UsageCache from DataStore JSON to Room

- New: UsageRecordEntity (Room Entity, indexed on workspaceId+timeCreated)
- New: UsageDao (CRUD + time-range queries)
- New: UsageDatabase (Room Database, version 1)
- New: migrateDataStoreToRoom() — one-time migration from old DataStore JSON
- Rewrite: UsageCache internal impl from JSON serialize/deserialize to Room DAO
- UsageCache public API unchanged (getAll/insertAll/getRecords/count/etc.)
- Old DataStore key cleared after successful migration
- SharedPreferences flag prevents re-migration
- Room 2.7.1 + KSP compatible
- libs.versions.toml + build.gradle.kts updated

PLAN.md

@@ -0,0 +1,198 @@
+# RainyToken 改进计划
+
+> 临时计划文件，执行完毕后删除。
+
+---
+
+## 1. 迁移 UsageCache 到 Room
+
+**现状问题**：
+- ~3700 条记录序列化为一个 JSON 字符串存入 DataStore 单 key
+- 每次 `insertAll` → `loadAll()` 全量读取 → 追加 → `persist()` 全量序列化写回
+- APP 冷启动时内存缓存丢失，需反序列化整个 JSON 字符串
+- 数据只增不减，半年后可能上万条，写入和启动读取会线性恶化
+- `getRecords(workspaceId, fromTs, toTs)` 是全量遍历后过滤，Room 用索引查询是 O(log n)
+
+**目标**：
+- 用 Room 替换 DataStore JSON 方案
+- `UsageRecord` 作为 Entity，`workspaceId` + `timeCreated` 建索引
+- `UsageCache` 接口不变（`getAll` / `insertAll` / `getRecords` / `getStatsByModel` / `getStatsByDay` / `getOverview` / `deleteByWorkspaceId` / `count` / `getDistinctModels` / `getLatest` / `getAllIds`），内部实现从 JSON 序列化改为 Room DAO 查询
+- 保留内存缓存层（`@Volatile cachedAll`），但改为按需查询而非全量加载
+- 数据迁移：首次启动时检查旧 DataStore 数据，一次性导入 Room，然后清理旧 key
+
+**涉及文件**：
+- 新建：`data/local/UsageDatabase.kt`（Room Database + DAO）
+- 新建：`data/local/UsageRecordEntity.kt`（Entity 定义，从现有 `UsageRecord` 迁移）
+- 修改：`data/local/UsageCache.kt`（内部实现改为 Room DAO 调用，接口不变）
+- 修改：`di/NetworkModule.kt`（@Provides RoomDatabase 实例）
+- 修改：`app/build.gradle.kts`（添加 Room 依赖）
+
+**验证标准**：
+- APP 启动后 OCGO / CCGO 用量数据正常显示
+- 下拉刷新触发增量同步后新数据正确入库
+- CCGO 清除按钮能正确删除并重新全量同步
+- 图表、总览、原始数据页面正常渲染
+- 冷启动不再有全量 JSON 反序列化卡顿
+
+---
+
+## 2. 加解析单元测试
+
+**现状问题**：
+- `OllamaRepository.parseUsage()` 和 `OpenCodeGoRepository.parseWindows()` 用正则解析 HTML
+- 对方改一次页面结构就失效，且失效表现是静默的（显示 0% 而非报错）
+- `CredentialEditViewModel.load()` 每次加新服务都要改回显分支，漏了用户看不到已存凭据
+
+**目标**：
+- 纯 JVM 单元测试，不需要 Android 设备
+- 测试用例用之前抓到的真实 HTML（Ollama settings 页）作为 fixture
+
+**涉及文件**：
+- 新建：`app/src/test/java/com/rainy/token/data/repository/OllamaRepositoryTest.kt`
+  - 测试 plan 解析（Pro / Max / Free）
+  - 测试 session/weekly 百分比解析（含小数 35.1%）
+  - 测试 data-time 重置时间戳解析
+  - 测试 data-model + data-requests 模型级数据解析
+  - 测试无效 Cookie / 空页面 / HTML 结构变更场景
+- 新建：`app/src/test/java/com/rainy/token/data/repository/OpenCodeGoRepositoryTest.kt`
+  - 测试 rollingUsage / weeklyUsage / monthlyUsage 解析
+  - 测试嵌套对象的括号匹配
+  - 测试 HTML 无目标数据时的 fallback
+
+**验证标准**：
+- `./gradlew test` 全部通过
+- 测试覆盖正则解析的主要路径和边界情况
+
+---
+
+## 3. DashboardScreen 拆分
+
+**现状问题**：
+- DashboardScreen.kt 1121 行，包含主框架 + 所有服务卡片 + 拖拽逻辑 + 工具函数
+- 加一个新服务要改这一个文件至少 3 处
+
+**目标**：
+- 拆成 3 个文件：
+  - `DashboardScreen.kt` — 主框架 + Scaffold + PullToRefresh（~200 行）
+  - `ServiceBalanceCards.kt` — 各服务的 MainBalance + UsageWindows Composable
+  - `DashboardDragState.kt` — 拖拽状态管理类 + 工具函数
+
+**涉及文件**：
+- 修改：`ui/dashboard/DashboardScreen.kt`（大幅精简）
+- 新建：`ui/dashboard/ServiceBalanceCards.kt`
+- 新建：`ui/dashboard/DashboardDragState.kt`
+
+**验证标准**：
+- 编译通过
+- Dashboard 功能不变（卡片显示、拖拽排序、下拉刷新、自适应布局）
+- 新增服务时只需改 `ServiceBalanceCards.kt` + `secondaryLine`
+
+---
+
+## 4. 重复函数提取
+
+**现状问题**：
+- `formatAmount(Double)` — DashboardScreen.kt + ServiceDetailScreen.kt 各一份
+- `normalizeWindowLabel(String)` — DashboardScreen.kt + WidgetProvider 各一份
+- `formatResetInSec(Long)` / `formatReset(Long)` — DashboardScreen.kt + ServiceDetailScreen.kt + WidgetProvider 三份
+- `parseCookieString(String)` — CredentialEditViewModel.kt 独一份，但应该在公共位置
+
+**目标**：
+- 抽取到 `ui/components/FormatUtils.kt`（UI 层共享）
+- `parseCookieString` 抽到 `data/repository/CookieUtils.kt`
+
+**涉及文件**：
+- 新建：`ui/components/FormatUtils.kt`
+- 新建：`data/repository/CookieUtils.kt`
+- 修改：DashboardScreen.kt / ServiceDetailScreen.kt / OpenCodeGoWidgetProvider.kt / CredentialEditViewModel.kt（删除重复定义，改用 import）
+
+**验证标准**：
+- 编译通过，无行为变化
+
+---
+
+## 5. Repository 加重试
+
+**现状问题**：
+- 所有 Repository 的 `fetchBalance()` 只做一次请求，失败就返回 `Result.failure`
+- 网络抖动时用户需手动下拉刷新
+
+**目标**：
+- 对 `RepositoryError.Network` 和 `RepositoryError.ServerError(5xx)` 加一次指数退避重试（最多 2 次）
+- 401/403/429 不重试
+- 可以做成 OkHttp Interceptor 或在 Repository 层包一层 `retryOnce`
+
+**涉及文件**：
+- 新建或修改：`data/repository/RetryHelper.kt`（通用重试包装）
+- 修改：各 Repository 的 `fetchBalance()`（包一层 retry）
+
+**验证标准**：
+- 编译通过
+- 网络抖动时自动重试一次而非直接失败
+- 401/403 仍然立即失败不重试
+
+---
+
+## 6. CredentialEditViewModel 模板化
+
+**现状问题**：
+- `saveOpenCodeGoSession()` / `testAndSaveOpenCodeGo()` / `saveOllamaCredential()` / `testAndSaveOllama()` / `saveCommandCodeGoCredential()` / `testAndSaveCommandCodeGo()` 等方法成对出现，结构几乎一样
+
+**目标**：
+- 抽取通用的 `saveAndTestCredential(service, saveBlock, testBlock)` 模板方法
+- 各服务只传不同的 save + test lambda
+
+**涉及文件**：
+- 修改：`ui/settings/CredentialEditViewModel.kt`
+
+**验证标准**：
+- 编译通过
+- 各服务的保存/测试功能不变
+- 新增服务时只需写 save + test 两个 lambda，不再写完整的成对方法
+
+---
+
+## 7. 删除 Jsoup 依赖
+
+**现状问题**：
+- `build.gradle.kts` 引入了 `org.jsoup:jsoup`，代码里 0 处 import
+
+**涉及文件**：
+- 修改：`app/build.gradle.kts`（删除 `implementation(libs.jsoup)`）
+
+**验证标准**：
+- 编译通过
+
+---
+
+## 8. ChartSettingsStore 改 Flow
+
+**现状问题**：
+- `ChartSettingsStore.getUseUtc8()` 用 `runBlocking` 同步读 DataStore，在 UI 线程调用
+
+**目标**：
+- 改成 `StateFlow` 暴露，Composable 层 `collectAsState`
+
+**涉及文件**：
+- 修改：`data/local/ChartSettingsStore.kt`
+- 修改：调用 `getUseUtc8()` 的 Composable 层
+
+**验证标准**：
+- 编译通过
+- 图表页 UTC 偏好切换正常
+- 退出再进入能恢复上次偏好
+
+---
+
+## 执行顺序
+
+1. 迁移 Room（基础设施，后续都依赖它）
+2. 加解析单元测试（在改其他代码前先有回归保护）
+3. DashboardScreen 拆分
+4. 重复函数提取
+5. Repository 加重试
+6. CredentialEditViewModel 模板化
+7. 删除 Jsoup 依赖
+8. ChartSettingsStore 改 Flow
+
+每步完成后 `./gradlew assembleDebug` 验证编译，全部完成后执行 `git commit` 并删除此计划文件。

app/build.gradle.kts

@@ -109,6 +109,11 @@ dependencies {
     ksp(libs.hilt.compiler)
     implementation(libs.androidx.hilt.navigation.compose)
 
+    // Room
+    implementation(libs.room.runtime)
+    implementation(libs.room.ktx)
+    ksp(libs.room.compiler)
+
     // Test
     testImplementation(libs.junit)
     androidTestImplementation(libs.androidx.junit)

app/src/main/java/com/rainy/token/data/local/UsageCache.kt

@@ -3,91 +3,81 @@ package com.rainy.token.data.local
 import android.content.Context
 import androidx.datastore.core.DataStore
 import androidx.datastore.preferences.core.Preferences
-import androidx.datastore.preferences.core.edit
-import androidx.datastore.preferences.core.stringPreferencesKey
-import androidx.datastore.preferences.preferencesDataStore
 import kotlinx.coroutines.flow.Flow
-import kotlinx.coroutines.flow.first
-import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.sync.Mutex
+import kotlinx.coroutines.sync.withLock
 import kotlinx.serialization.Serializable
-import kotlinx.serialization.builtins.ListSerializer
 import kotlinx.serialization.json.Json
 
 /**
- * 用量记录本地缓存（DataStore，非 Room）。
+ * 用量记录本地缓存（Room 实现）。
  *
- * 所有记录序列化为 JSON 列表存入 DataStore。
- * 约 3700 条记录，每条约 300 字节 → ~1.1MB，DataStore 可承受。
+ * 接口与旧 DataStore 版本完全一致，内部改为 Room DAO 查询。
+ * 首次访问时自动从旧 DataStore JSON 迁移数据到 Room。
  */
 class UsageCache(
+    private val context: Context,
+    private val dao: UsageDao,
     private val dataStore: DataStore<Preferences>,
     private val json: Json = Json { ignoreUnknownKeys = true; encodeDefaults = true }
 ) {
-    private val cacheKey = stringPreferencesKey("usage_cache_v1")
+    private val migrationMutex = Mutex()
+    @Volatile private var migrated = false
 
-    // ── 内存缓存：避免每次都反序列化整个 JSON ──
-    @Volatile private var cachedAll: List<UsageRecord>? = null
-    @Volatile private var cachedIds: Set<String>? = null
-
-    /** 读取全量（优先内存缓存） */
-    private suspend fun loadAll(): List<UsageRecord> {
-        cachedAll?.let { return it }
-        val records = readFromStore()
-        cachedAll = records
-        cachedIds = records.map { it.id }.toSet()
-        return records
+    /** 确保旧数据已迁移到 Room（仅执行一次） */
+    private suspend fun ensureMigrated() {
+        if (migrated) return
+        migrationMutex.withLock {
+            if (migrated) return
+            migrateDataStoreToRoom(context, dataStore, dao, json)
+            migrated = true
+        }
     }
 
-    private suspend fun readFromStore(): List<UsageRecord> {
-        val raw = dataStore.data.map { it[cacheKey] }.first() ?: return emptyList()
-        return runCatching {
-            json.decodeFromString(ListSerializer(UsageRecord.serializer()), raw)
-        }.getOrDefault(emptyList())
+    suspend fun getAll(): List<UsageRecord> {
+        ensureMigrated()
+        return dao.getAll().map { it.toDomain() }
     }
 
-    /** 写入后清空内存缓存 */
-    private fun invalidateCache() {
-        cachedAll = null
-        cachedIds = null
-    }
-
-    suspend fun getAll(): List<UsageRecord> = loadAll()
-
-    fun getAllFlow(): Flow<List<UsageRecord>> =
-        dataStore.data.map { prefs ->
-            val raw = prefs[cacheKey] ?: return@map emptyList()
-            runCatching {
-                json.decodeFromString(ListSerializer(UsageRecord.serializer()), raw)
-            }.getOrDefault(emptyList())
+    fun getAllFlow(): Flow<List<UsageRecord>> = flow {
+        ensureMigrated()
+        emit(dao.getAll().map { it.toDomain() })
     }
 
     suspend fun insertAll(newRecords: List<UsageRecord>) {
-        val current = loadAll().toMutableList()
-        val existingIds = cachedIds ?: current.map { it.id }.toSet()
-        val toAdd = newRecords.filter { it.id !in existingIds }
-        if (toAdd.isEmpty()) return
-        current.addAll(toAdd)
-        persist(current)
+        ensureMigrated()
+        if (newRecords.isEmpty()) return
+        val entities = newRecords.map { it.toEntity() }
+        dao.insertAll(entities)
     }
 
-    suspend fun getLatest(): UsageRecord? = loadAll().maxByOrNull { it.timeCreated }
+    suspend fun getLatest(): UsageRecord? {
+        ensureMigrated()
+        return dao.getLatest()?.toDomain()
+    }
 
     suspend fun getAllIds(): Set<String> {
-        cachedIds?.let { return it }
-        return loadAll().map { it.id }.toSet()
+        ensureMigrated()
+        return dao.getAllIds().toSet()
     }
 
     /** 按 workspaceId 删除所有记录。用于修复旧数据格式问题后重新全量同步。 */
     suspend fun deleteByWorkspaceId(workspaceId: String) {
-        val current = loadAll().toMutableList()
-        val removed = current.removeAll { it.workspaceId == workspaceId }
-        if (removed) persist(current)
+        ensureMigrated()
+        dao.deleteByWorkspaceId(workspaceId)
     }
 
-    suspend fun count(): Int = loadAll().size
+    suspend fun count(): Int {
+        ensureMigrated()
+        return dao.count()
+    }
 
     /** 按 workspaceId 统计记录数。 */
-    suspend fun count(workspaceId: String): Int = loadAll().count { it.workspaceId == workspaceId }
+    suspend fun count(workspaceId: String): Int {
+        ensureMigrated()
+        return dao.countByWorkspace(workspaceId)
+    }
 
     /** 获取过滤后的原始记录列表（供图表等聚合使用） */
     suspend fun getRecords(
@@ -95,24 +85,20 @@ class UsageCache(
         fromTs: Long? = null,
         toTs: Long? = null
     ): List<UsageRecord> {
-        return filterByTime(loadAll().filter { it.workspaceId == workspaceId }, fromTs, toTs)
+        ensureMigrated()
+        val entities = when {
+            fromTs != null && toTs != null -> dao.getByWorkspaceAndTime(workspaceId, fromTs, toTs)
+            fromTs != null -> dao.getByWorkspaceFrom(workspaceId, fromTs)
+            toTs != null -> dao.getByWorkspaceTo(workspaceId, toTs)
+            else -> dao.getByWorkspace(workspaceId)
+        }
+        return entities.map { it.toDomain() }
     }
 
     /** 获取所有不同模型名称 */
     suspend fun getDistinctModels(workspaceId: String): List<String> {
-        return loadAll()
-            .filter { it.workspaceId == workspaceId }
-            .map { it.model }
-            .distinct()
-            .sorted()
-    }
-
-    /** 按时间范围过滤记录 */
-    private fun filterByTime(records: List<UsageRecord>, fromTs: Long?, toTs: Long?): List<UsageRecord> {
-        var result = records
-        if (fromTs != null) result = result.filter { it.timeCreated >= fromTs }
-        if (toTs != null) result = result.filter { it.timeCreated <= toTs }
-        return result
+        ensureMigrated()
+        return dao.getDistinctModels(workspaceId)
     }
 
     suspend fun getStatsByModel(
@@ -120,14 +106,15 @@ class UsageCache(
         fromTs: Long? = null,
         toTs: Long? = null
     ): List<ModelStats> {
-        return filterByTime(loadAll().filter { it.workspaceId == workspaceId }, fromTs, toTs)
+        val records = getRecords(workspaceId, fromTs, toTs)
+        return records
             .groupBy { it.model }
-            .map { (model, records) ->
+            .map { (model, recs) ->
                 ModelStats(
                     model = model,
-                    totalTokens = records.sumOf { it.totalTokens },
-                    totalCost = records.sumOf { it.cost },
-                    count = records.size
+                    totalTokens = recs.sumOf { it.totalTokens },
+                    totalCost = recs.sumOf { it.cost },
+                    count = recs.size
                 )
             }
             .sortedByDescending { it.totalTokens }
@@ -139,14 +126,15 @@ class UsageCache(
         fromTs: Long? = null,
         toTs: Long? = null
     ): List<DailyStats> {
-        return filterByTime(loadAll().filter { it.workspaceId == workspaceId }, fromTs, toTs)
+        val records = getRecords(workspaceId, fromTs, toTs)
+        return records
             .groupBy { it.timeCreated / 86_400_000L * 86_400_000L }
-            .map { (dayTs, records) ->
+            .map { (dayTs, recs) ->
                 DailyStats(
                     dayTs = dayTs,
-                    totalTokens = records.sumOf { it.totalTokens },
-                    totalCost = records.sumOf { it.cost },
-                    count = records.size
+                    totalTokens = recs.sumOf { it.totalTokens },
+                    totalCost = recs.sumOf { it.cost },
+                    count = recs.size
                 )
             }
             .sortedByDescending { it.dayTs }
@@ -158,7 +146,7 @@ class UsageCache(
         fromTs: Long? = null,
         toTs: Long? = null
     ): OverviewStats? {
-        val records = filterByTime(loadAll().filter { it.workspaceId == workspaceId }, fromTs, toTs)
+        val records = getRecords(workspaceId, fromTs, toTs)
         if (records.isEmpty()) return null
         return OverviewStats(
             totalTokens = records.sumOf { it.inputTokens + it.cacheReadTokens + it.outputTokens },
@@ -173,12 +161,6 @@ class UsageCache(
             cacheWrite1hTokens = records.sumOf { it.cacheWrite1hTokens }
         )
     }
-
-    private suspend fun persist(list: List<UsageRecord>) {
-        val raw = json.encodeToString(ListSerializer(UsageRecord.serializer()), list)
-        dataStore.edit { it[cacheKey] = raw }
-        invalidateCache()
-    }
 }
 
 @Serializable
@@ -234,7 +216,7 @@ data class OverviewStats(
     val cacheWriteTokens: Long get() = cacheWrite5mTokens + cacheWrite1hTokens
 }
 
-/** DataStore 委托 */
-val Context.usageCacheDataStore: DataStore<Preferences> by preferencesDataStore(
+/** DataStore 委托 — 保留用于数据迁移，迁移完成后旧 key 会被清除 */
+val Context.usageCacheDataStore: DataStore<Preferences> by androidx.datastore.preferences.preferencesDataStore(
     name = "usage_cache"
 )

app/src/main/java/com/rainy/token/data/local/UsageDao.kt

@@ -0,0 +1,52 @@
+package com.rainy.token.data.local
+
+import androidx.room.Dao
+import androidx.room.Insert
+import androidx.room.OnConflictStrategy
+import androidx.room.Query
+
+@Dao
+interface UsageDao {
+
+    @Query("SELECT * FROM usage_records")
+    suspend fun getAll(): List<UsageRecordEntity>
+
+    @Query("SELECT * FROM usage_records WHERE workspaceId = :workspaceId ORDER BY timeCreated DESC")
+    suspend fun getByWorkspace(workspaceId: String): List<UsageRecordEntity>
+
+    @Query("SELECT * FROM usage_records WHERE workspaceId = :workspaceId AND timeCreated >= :fromTs AND timeCreated <= :toTs ORDER BY timeCreated DESC")
+    suspend fun getByWorkspaceAndTime(workspaceId: String, fromTs: Long, toTs: Long): List<UsageRecordEntity>
+
+    @Query("SELECT * FROM usage_records WHERE workspaceId = :workspaceId AND timeCreated >= :fromTs ORDER BY timeCreated DESC")
+    suspend fun getByWorkspaceFrom(workspaceId: String, fromTs: Long): List<UsageRecordEntity>
+
+    @Query("SELECT * FROM usage_records WHERE workspaceId = :workspaceId AND timeCreated <= :toTs ORDER BY timeCreated DESC")
+    suspend fun getByWorkspaceTo(workspaceId: String, toTs: Long): List<UsageRecordEntity>
+
+    @Insert(onConflict = OnConflictStrategy.IGNORE)
+    suspend fun insertAll(records: List<UsageRecordEntity>): List<Long>
+
+    @Query("DELETE FROM usage_records WHERE workspaceId = :workspaceId")
+    suspend fun deleteByWorkspaceId(workspaceId: String): Int
+
+    @Query("SELECT COUNT(*) FROM usage_records")
+    suspend fun count(): Int
+
+    @Query("SELECT COUNT(*) FROM usage_records WHERE workspaceId = :workspaceId")
+    suspend fun countByWorkspace(workspaceId: String): Int
+
+    @Query("SELECT DISTINCT model FROM usage_records WHERE workspaceId = :workspaceId ORDER BY model ASC")
+    suspend fun getDistinctModels(workspaceId: String): List<String>
+
+    @Query("SELECT * FROM usage_records ORDER BY timeCreated DESC LIMIT 1")
+    suspend fun getLatest(): UsageRecordEntity?
+
+    @Query("SELECT id FROM usage_records")
+    suspend fun getAllIds(): List<String>
+
+    @Query("SELECT id FROM usage_records WHERE workspaceId = :workspaceId")
+    suspend fun getIdsByWorkspace(workspaceId: String): List<String>
+
+    @Query("SELECT MAX(timeCreated) FROM usage_records WHERE workspaceId = :workspaceId")
+    suspend fun getMaxTimeCreated(workspaceId: String): Long?
+}

app/src/main/java/com/rainy/token/data/local/UsageDatabase.kt

@@ -0,0 +1,80 @@
+package com.rainy.token.data.local
+
+import android.content.Context
+import androidx.datastore.core.DataStore
+import androidx.datastore.preferences.core.Preferences
+import androidx.datastore.preferences.core.edit
+import androidx.datastore.preferences.core.stringPreferencesKey
+import androidx.room.Database
+import androidx.room.Room
+import androidx.room.RoomDatabase
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.flow.map
+import kotlinx.serialization.builtins.ListSerializer
+import kotlinx.serialization.json.Json
+
+@Database(
+    entities = [UsageRecordEntity::class],
+    version = 1,
+    exportSchema = false
+)
+abstract class UsageDatabase : RoomDatabase() {
+    abstract fun usageDao(): UsageDao
+
+    companion object {
+        @Volatile
+        private var INSTANCE: UsageDatabase? = null
+
+        fun getInstance(context: Context): UsageDatabase {
+            return INSTANCE ?: synchronized(this) {
+                INSTANCE ?: Room.databaseBuilder(
+                    context.applicationContext,
+                    UsageDatabase::class.java,
+                    "usage_database"
+                ).build().also { INSTANCE = it }
+            }
+        }
+    }
+}
+
+/**
+ * One-time migration from old DataStore JSON cache to Room.
+ *
+ * Called by [UsageCache] on first access. Reads the old JSON blob from DataStore,
+ * deserializes it, inserts into Room, then clears the old key.
+ *
+ * A SharedPreferences flag prevents re-running if the old data was already consumed
+ * (e.g. if the DataStore was cleared but the flag was set).
+ *
+ * @return true if migration ran and inserted records, false if no migration was needed.
+ */
+suspend fun migrateDataStoreToRoom(
+    context: Context,
+    dataStore: DataStore<Preferences>,
+    dao: UsageDao,
+    json: Json
+): Boolean {
+    val prefs = context.getSharedPreferences("usage_cache_migration", Context.MODE_PRIVATE)
+    if (prefs.getBoolean("migrated_to_room", false)) return false
+
+    val cacheKey = stringPreferencesKey("usage_cache_v1")
+    val raw = dataStore.data.map { it[cacheKey] }.first() ?: run {
+        // No old data — mark as migrated so we never check again
+        prefs.edit().putBoolean("migrated_to_room", true).apply()
+        return false
+    }
+
+    val records = runCatching {
+        json.decodeFromString(ListSerializer(UsageRecord.serializer()), raw)
+    }.getOrDefault(emptyList())
+
+    if (records.isNotEmpty()) {
+        val entities = records.map { it.toEntity() }
+        dao.insertAll(entities)
+    }
+
+    // Mark migrated and clear old key to free space
+    prefs.edit().putBoolean("migrated_to_room", true).apply()
+    dataStore.edit { it.remove(cacheKey) }
+    return records.isNotEmpty()
+}

app/src/main/java/com/rainy/token/data/local/UsageRecordEntity.kt

@@ -0,0 +1,81 @@
+package com.rainy.token.data.local
+
+import androidx.room.Entity
+import androidx.room.Index
+import androidx.room.PrimaryKey
+
+/**
+ * Room Entity for usage records.
+ *
+ * Mirrors the fields of [UsageRecord] exactly.
+ * Indexes on workspaceId + timeCreated for fast time-range queries.
+ */
+@Entity(
+    tableName = "usage_records",
+    indices = [
+        Index(value = ["workspaceId", "timeCreated"]),
+        Index(value = ["workspaceId", "model"]),
+        Index(value = ["id"], unique = true)
+    ]
+)
+data class UsageRecordEntity(
+    @PrimaryKey
+    val id: String,
+    val workspaceId: String,
+    val timeCreated: Long,
+    val timeUpdated: Long,
+    val model: String,
+    val provider: String,
+    val inputTokens: Long,
+    val outputTokens: Long,
+    val reasoningTokens: Long,
+    val cacheReadTokens: Long,
+    val cacheWrite5mTokens: Long = 0,
+    val cacheWrite1hTokens: Long = 0,
+    val cost: Long,
+    val keyId: String,
+    val sessionId: String,
+    val enrichmentPlan: String = ""
+) {
+    /** Convert Entity → domain model */
+    fun toDomain(): UsageRecord = UsageRecord(
+        id = id,
+        workspaceId = workspaceId,
+        timeCreated = timeCreated,
+        timeUpdated = timeUpdated,
+        model = model,
+        provider = provider,
+        inputTokens = inputTokens,
+        outputTokens = outputTokens,
+        reasoningTokens = reasoningTokens,
+        cacheReadTokens = cacheReadTokens,
+        cacheWrite5mTokens = cacheWrite5mTokens,
+        cacheWrite1hTokens = cacheWrite1hTokens,
+        cost = cost,
+        keyId = keyId,
+        sessionId = sessionId,
+        enrichmentPlan = enrichmentPlan
+    )
+
+    val totalTokens: Long get() = inputTokens + outputTokens + reasoningTokens
+}
+
+/** Convert domain model → Entity */
+fun UsageRecord.toEntity(): UsageRecordEntity = UsageRecordEntity(
+    id = id,
+    workspaceId = workspaceId,
+    timeCreated = timeCreated,
+    timeUpdated = timeUpdated,
+    model = model,
+    provider = provider,
+    inputTokens = inputTokens,
+    outputTokens = outputTokens,
+    reasoningTokens = reasoningTokens,
+    cacheReadTokens = cacheReadTokens,
+    cacheWrite5mTokens = cacheWrite5mTokens,
+    cacheWrite1hTokens = cacheWrite1hTokens,
+    cost = cost,
+    keyId = keyId,
+    sessionId = sessionId,
+    enrichmentPlan = enrichmentPlan
+)

app/src/main/java/com/rainy/token/di/NetworkModule.kt

@@ -6,6 +6,8 @@ import com.rainy.token.data.cache.balanceCacheDataStore
 import com.rainy.token.data.remote.DeepSeekApi
 import com.rainy.token.data.local.SecureStorage
 import com.rainy.token.data.local.UsageCache
+import com.rainy.token.data.local.UsageDao
+import com.rainy.token.data.local.UsageDatabase
 import com.rainy.token.data.local.usageCacheDataStore
 import com.rainy.token.data.repository.CredentialRepository
 import com.rainy.token.data.repository.DeepSeekRepository
@@ -78,12 +80,26 @@ object NetworkModule {
 
     // ---- Room ----
 
+    @Provides
+    @Singleton
+    fun provideUsageDatabase(
+        @ApplicationContext context: Context
+    ): UsageDatabase = UsageDatabase.getInstance(context)
+
+    @Provides
+    @Singleton
+    fun provideUsageDao(
+        database: UsageDatabase
+    ): UsageDao = database.usageDao()
+
     @Provides
     @Singleton
     fun provideUsageCache(
+        @ApplicationContext context: Context,
+        dao: UsageDao,
         @Named(DataStoreQualifiers.USAGE_CACHE) dataStore: DataStore<Preferences>,
         json: Json
-    ): UsageCache = UsageCache(dataStore, json)
+    ): UsageCache = UsageCache(context, dao, dataStore, json)
 
     // ---- Repositories ----
 

gradle/libs.versions.toml

@@ -33,6 +33,9 @@ workRuntimeKtx = "2.9.1"
 hilt = "2.59.2"
 hiltNavigationCompose = "1.2.0"
 
+# Room
+room = "2.7.1"
+
 # Test
 junit = "4.13.2"
 junitVersion = "1.2.1"
@@ -82,6 +85,11 @@ hilt-android = { group = "com.google.dagger", name = "hilt-android", version.ref
 hilt-compiler = { group = "com.google.dagger", name = "hilt-compiler", version.ref = "hilt" }
 androidx-hilt-navigation-compose = { group = "androidx.hilt", name = "hilt-navigation-compose", version.ref = "hiltNavigationCompose" }
 
+# Room
+room-runtime = { group = "androidx.room", name = "room-runtime", version.ref = "room" }
+room-ktx = { group = "androidx.room", name = "room-ktx", version.ref = "room" }
+room-compiler = { group = "androidx.room", name = "room-compiler", version.ref = "room" }
+
 # Test
 junit = { group = "junit", name = "junit", version.ref = "junit" }
 androidx-junit = { group = "androidx.test.ext", name = "junit", version.ref = "junitVersion" }