diff --git a/Auth/build.gradle.kts b/Auth/build.gradle.kts
index 41acf0129..673155124 100644
--- a/Auth/build.gradle.kts
+++ b/Auth/build.gradle.kts
@@ -57,6 +57,7 @@ dependencies {
     implementation(core.kotlinx.serialization.json)
     implementation(core.gson)
     implementation(core.splitties.appctx)
+    implementation(core.splitties.bitflags)
     implementation(core.okhttp)
     api(core.gson)
 
diff --git a/Auth/src/fdroid/kotlin/com/infomaniak/core/auth/backup/BlockStoreBackup.kt b/Auth/src/fdroid/kotlin/com/infomaniak/core/auth/backup/BlockStoreBackup.kt
index c6b2d5753..08335d839 100644
--- a/Auth/src/fdroid/kotlin/com/infomaniak/core/auth/backup/BlockStoreBackup.kt
+++ b/Auth/src/fdroid/kotlin/com/infomaniak/core/auth/backup/BlockStoreBackup.kt
@@ -17,8 +17,15 @@
  */
 package com.infomaniak.core.auth.backup
 
+import android.app.backup.FullBackupDataOutput
+import com.infomaniak.core.common.backup.FullBackupAgent
+
 object BlockStoreBackup {
     const val isSupported: Boolean = false
+
+    context(agent: FullBackupAgent)
+    fun backupTestBlockStoreIfNeeded(data: FullBackupDataOutput) {}
+
     suspend fun backupTokens(): Boolean = false
     suspend fun restoreTokens(): Boolean = false
 }
diff --git a/Auth/src/main/kotlin/com/infomaniak/core/auth/backup/BlockStoreCredentialsBackup.kt b/Auth/src/main/kotlin/com/infomaniak/core/auth/backup/BlockStoreCredentialsBackup.kt
index ebd3fcdb3..f82a7445a 100644
--- a/Auth/src/main/kotlin/com/infomaniak/core/auth/backup/BlockStoreCredentialsBackup.kt
+++ b/Auth/src/main/kotlin/com/infomaniak/core/auth/backup/BlockStoreCredentialsBackup.kt
@@ -17,6 +17,7 @@
  */
 package com.infomaniak.core.auth.backup
 
+import android.app.backup.FullBackupDataOutput
 import androidx.room.execSQL
 import androidx.room.immediateTransaction
 import androidx.room.useWriterConnection
@@ -27,6 +28,7 @@ import kotlinx.coroutines.runBlocking
 
 context(_: FullBackupAgent)
 inline fun withBlockStoreCredentialsBackup(
+    data: FullBackupDataOutput,
     crossinline backupCredentials: suspend () -> Boolean = { BlockStoreBackup.backupTokens() },
     crossinline defaultBackupCalls: () -> Unit
 ): Unit = runBlocking {
@@ -36,6 +38,7 @@ inline fun withBlockStoreCredentialsBackup(
     }
     val succeeded = backupCredentials()
     if (!succeeded) return@runBlocking // Abort backup
+    BlockStoreBackup.backupTestBlockStoreIfNeeded(data)
     val db = UserDatabase.instance
     // We don't want to keep tokens in the db for backup, so we remove them temporarily.
     // Note that the app can perfectly recover from this state if the backup process is aborted, here's why:
diff --git a/Auth/src/standard/kotlin/com/infomaniak/core/auth/backup/BlockStore.kt b/Auth/src/standard/kotlin/com/infomaniak/core/auth/backup/BlockStore.kt
new file mode 100644
index 000000000..3436a436f
--- /dev/null
+++ b/Auth/src/standard/kotlin/com/infomaniak/core/auth/backup/BlockStore.kt
@@ -0,0 +1,42 @@
+/*
+ * Infomaniak Core - Android
+ * Copyright (C) 2026 Infomaniak Network SA
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package com.infomaniak.core.auth.backup
+
+import android.app.backup.FullBackupDataOutput
+import android.content.pm.ApplicationInfo
+import com.infomaniak.core.common.backup.FullBackupAgent
+import splitties.bitflags.hasFlag
+import splitties.init.appCtx
+
+sealed class BlockStore {
+
+    abstract suspend fun storeBytes(key: String, shouldBackupToCloud: Boolean, bytes: ByteArray)
+    abstract suspend fun retrieveBytes(keys: List<String>? = null): Map<String, ByteArray>
+    abstract suspend fun deleteBytes(keys: List<String>): Boolean
+    abstract suspend fun isE2eeAvailable(): Boolean
+
+    context(agent: FullBackupAgent)
+    abstract fun backupTestBlockStoreIfNeeded(data: FullBackupDataOutput)
+
+    companion object {
+        val instance: BlockStore = when {
+            appCtx.applicationInfo.flags.hasFlag(ApplicationInfo.FLAG_DEBUGGABLE) -> BlockStoreTestingImpl(e2eeAvailable = true)
+            else -> BlockStorePlayServicesImpl()
+        }
+    }
+}
diff --git a/Auth/src/standard/kotlin/com/infomaniak/core/auth/backup/BlockStoreBackup.kt b/Auth/src/standard/kotlin/com/infomaniak/core/auth/backup/BlockStoreBackup.kt
index 362d8e586..73039a129 100644
--- a/Auth/src/standard/kotlin/com/infomaniak/core/auth/backup/BlockStoreBackup.kt
+++ b/Auth/src/standard/kotlin/com/infomaniak/core/auth/backup/BlockStoreBackup.kt
@@ -17,29 +17,30 @@
  */
 package com.infomaniak.core.auth.backup
 
+import android.app.backup.FullBackupDataOutput
 import androidx.collection.LongObjectMap
 import androidx.collection.buildLongObjectMap
 import androidx.room.immediateTransaction
 import androidx.room.useWriterConnection
-import com.google.android.gms.auth.blockstore.Blockstore
-import com.google.android.gms.auth.blockstore.DeleteBytesRequest
-import com.google.android.gms.auth.blockstore.RetrieveBytesRequest
-import com.google.android.gms.auth.blockstore.StoreBytesData
 import com.infomaniak.core.auth.room.UserDatabase
+import com.infomaniak.core.common.backup.FullBackupAgent
 import com.infomaniak.core.common.cancellable
 import com.infomaniak.core.sentry.SentryLog
-import kotlinx.coroutines.tasks.await
-import splitties.init.appCtx
 
 object BlockStoreBackup {
 
     private const val TAG = "BlockStoreBackup"
 
-    private val blockstoreClient = Blockstore.getClient(appCtx)
+    private val blockStore = BlockStore.instance
     private val db = UserDatabase.instance
 
     const val isSupported: Boolean = true
 
+    context(agent: FullBackupAgent)
+    fun backupTestBlockStoreIfNeeded(data: FullBackupDataOutput) {
+        BlockStore.instance.backupTestBlockStoreIfNeeded(data)
+    }
+
     suspend fun backupTokens(): Boolean {
         val backupContent = dumpTokens()
         val alreadyBackedUpContent = readTokensBackup()
@@ -61,13 +62,12 @@ object BlockStoreBackup {
                 // This can happen if a previous backup was aborted, leaving tokens in the Block Store, but out of the DB.
                 return@count false // Didn't fail.
             }
-            val storeRequest = StoreBytesData.Builder()
-                .setKey(userId.toString())
-                .setShouldBackupToCloud(true)
-                .setBytes(accessToken.toByteArray())
-                .build()
             runCatching {
-                blockstoreClient.storeBytes(storeRequest).await()
+                blockStore.storeBytes(
+                    key = userId.toString(),
+                    shouldBackupToCloud = true,
+                    bytes = accessToken.toByteArray()
+                )
                 false // Didn't fail.
             }.cancellable().getOrElse { throwable ->
                 SentryLog.wtf(TAG, "Failed to backup token", throwable)
@@ -85,8 +85,7 @@ object BlockStoreBackup {
         val keysToDelete: List<String> = buildList {
             previousDump.forEachKey { key -> if (key !in tokensDump) add(key.toString()) }
         }
-        val deleteRequest = DeleteBytesRequest.Builder().setKeys(keysToDelete).build()
-        blockstoreClient.deleteBytes(deleteRequest).await()
+        blockStore.deleteBytes(keysToDelete)
     }
 
     private suspend fun dumpTokens(): LongObjectMap<String> = buildLongObjectMap {
@@ -94,14 +93,11 @@ object BlockStoreBackup {
     }
 
     private suspend fun readTokensBackup(): LongObjectMap<String>? {
-        val retrieveRequest = RetrieveBytesRequest.Builder()
-            .setRetrieveAll(true)
-            .build()
-        val dataMap = blockstoreClient.retrieveBytes(retrieveRequest).await().blockstoreDataMap.ifEmpty { return null }
+        val dataMap = blockStore.retrieveBytes().ifEmpty { return null }
         return buildLongObjectMap {
-            dataMap.forEach { (key, data) ->
+            dataMap.forEach { (key, bytes) ->
                 val userId = key.toLongOrNull() ?: return@forEach
-                this[userId] = String(data.bytes)
+                this[userId] = String(bytes)
             }
         }
     }
@@ -115,6 +111,4 @@ object BlockStoreBackup {
             }
         }
     }
-
-    private suspend fun isE2eeAvailable(): Boolean = blockstoreClient.isEndToEndEncryptionAvailable.await()
 }
diff --git a/Auth/src/standard/kotlin/com/infomaniak/core/auth/backup/BlockStorePlayServicesImpl.kt b/Auth/src/standard/kotlin/com/infomaniak/core/auth/backup/BlockStorePlayServicesImpl.kt
new file mode 100644
index 000000000..aa41c8365
--- /dev/null
+++ b/Auth/src/standard/kotlin/com/infomaniak/core/auth/backup/BlockStorePlayServicesImpl.kt
@@ -0,0 +1,62 @@
+/*
+ * Infomaniak Core - Android
+ * Copyright (C) 2026 Infomaniak Network SA
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package com.infomaniak.core.auth.backup
+
+import android.app.backup.FullBackupDataOutput
+import com.google.android.gms.auth.blockstore.Blockstore
+import com.google.android.gms.auth.blockstore.DeleteBytesRequest
+import com.google.android.gms.auth.blockstore.RetrieveBytesRequest
+import com.google.android.gms.auth.blockstore.StoreBytesData
+import com.infomaniak.core.common.backup.FullBackupAgent
+import kotlinx.coroutines.tasks.await
+import splitties.init.appCtx
+
+internal class BlockStorePlayServicesImpl : BlockStore() {
+    private val client = Blockstore.getClient(appCtx)
+
+    override suspend fun storeBytes(
+        key: String,
+        shouldBackupToCloud: Boolean,
+        bytes: ByteArray
+    ) {
+        val storeRequest = StoreBytesData.Builder()
+            .setKey(key)
+            .setShouldBackupToCloud(shouldBackupToCloud)
+            .setBytes(bytes)
+            .build()
+        client.storeBytes(storeRequest).await()
+    }
+
+    override suspend fun retrieveBytes(keys: List<String>?): Map<String, ByteArray> {
+        val retrieveRequest = RetrieveBytesRequest.Builder()
+            .setKeys(keys ?: emptyList())
+            .setRetrieveAll(keys == null)
+            .build()
+        return client.retrieveBytes(retrieveRequest).await().blockstoreDataMap.mapValues { it.value.bytes }
+    }
+
+    override suspend fun deleteBytes(keys: List<String>): Boolean {
+        val deleteRequest = DeleteBytesRequest.Builder().setKeys(keys).build()
+        return client.deleteBytes(deleteRequest).await()
+    }
+
+    override suspend fun isE2eeAvailable(): Boolean = client.isEndToEndEncryptionAvailable.await()
+
+    context(agent: FullBackupAgent)
+    override fun backupTestBlockStoreIfNeeded(data: FullBackupDataOutput) = Unit
+}
diff --git a/Auth/src/standard/kotlin/com/infomaniak/core/auth/backup/BlockStoreTestingImpl.kt b/Auth/src/standard/kotlin/com/infomaniak/core/auth/backup/BlockStoreTestingImpl.kt
new file mode 100644
index 000000000..1d35546f9
--- /dev/null
+++ b/Auth/src/standard/kotlin/com/infomaniak/core/auth/backup/BlockStoreTestingImpl.kt
@@ -0,0 +1,84 @@
+/*
+ * Infomaniak Core - Android
+ * Copyright (C) 2026 Infomaniak Network SA
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+@file:OptIn(ExperimentalAtomicApi::class)
+
+package com.infomaniak.core.auth.backup
+
+import android.app.backup.FullBackupDataOutput
+import com.infomaniak.core.common.backup.FullBackupAgent
+import com.infomaniak.core.common.backup.isDeviceToDeviceTransfer
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.invoke
+import splitties.init.appCtx
+import java.io.File
+import kotlin.concurrent.atomics.ExperimentalAtomicApi
+
+internal class BlockStoreTestingImpl(private val e2eeAvailable: Boolean) : BlockStore() {
+
+    private val dir by lazy { appCtx.filesDir.resolve("debugBlockStore").also { it.mkdir() } }
+    private val shouldBackupToCloudSuffix = "-cloud-ok"
+
+    override suspend fun storeBytes(key: String, shouldBackupToCloud: Boolean, bytes: ByteArray) {
+        Dispatchers.IO {
+            val cloudOkFile = dir.resolve(key + shouldBackupToCloudSuffix)
+            val deviceToDeviceOnlyFile = dir.resolve(key)
+            val file = if (shouldBackupToCloud) cloudOkFile else deviceToDeviceOnlyFile
+            file.writeBytes(bytes)
+            val fileToDelete = if (shouldBackupToCloud) deviceToDeviceOnlyFile else cloudOkFile
+            fileToDelete.delete()
+        }
+    }
+
+    override suspend fun retrieveBytes(keys: List<String>?): Map<String, ByteArray> = Dispatchers.IO {
+        val targetKeys = keys ?: getStoredKeys()
+        buildMap(capacity = targetKeys.size) {
+            targetKeys.forEach { key ->
+                val bytes = fileForKey(key)?.readBytes() ?: return@forEach
+                this[key] = bytes
+            }
+        }
+    }
+
+    override suspend fun deleteBytes(keys: List<String>): Boolean = Dispatchers.IO {
+        var deleted = false
+        keys.forEach { key ->
+            deleted = dir.resolve(key).delete() || deleted
+            deleted = dir.resolve(key + shouldBackupToCloudSuffix).delete() || deleted
+        }
+        deleted
+    }
+
+    override suspend fun isE2eeAvailable(): Boolean = e2eeAvailable
+
+    context(agent: FullBackupAgent)
+    override fun backupTestBlockStoreIfNeeded(data: FullBackupDataOutput) {
+        dir.listFiles()?.forEach { file ->
+            if (data.isDeviceToDeviceTransfer || file.name.endsWith(shouldBackupToCloudSuffix)) {
+                agent.fullBackupFile(file, data)
+            }
+        }
+    }
+
+    private fun fileForKey(key: String): File? {
+        return dir.resolve(key).takeIf { it.exists() } ?: dir.resolve(key + shouldBackupToCloudSuffix).takeIf { it.exists() }
+    }
+
+    private fun getStoredKeys(): List<String> {
+        return (dir.list()?.asList() ?: emptyList<String>()).map { it.removeSuffix(shouldBackupToCloudSuffix) }
+    }
+}