diff --git a/Android.bp b/Android.bp
index 46529b7a2..d91128085 100644
--- a/Android.bp
+++ b/Android.bp
@@ -26,7 +26,8 @@ android_app {
         "com.google.android.material_material",
         "kotlinx-coroutines-android",
         "kotlinx-coroutines-core",
-        // storage backup lib
+        // our own gradle module libs
+        "seedvault-lib-core",
         "seedvault-lib-storage",
         // koin
         "seedvault-lib-koin-core-jvm", // did not manage to add this as transitive dependency
@@ -36,7 +37,6 @@ android_app {
         // WebDAV
         "seedvault-lib-dav4jvm",
         "seedvault-lib-okhttp",
-        "seedvault-lib-okio",
     ],
     manifest: "app/src/main/AndroidManifest.xml",
 
diff --git a/app/src/main/java/com/stevesoltys/seedvault/App.kt b/app/src/main/java/com/stevesoltys/seedvault/App.kt
index a62710ecc..afc5bc74e 100644
--- a/app/src/main/java/com/stevesoltys/seedvault/App.kt
+++ b/app/src/main/java/com/stevesoltys/seedvault/App.kt
@@ -20,13 +20,13 @@ import android.os.UserManager
 import androidx.work.ExistingPeriodicWorkPolicy.UPDATE
 import androidx.work.WorkManager
 import com.google.android.material.color.DynamicColors
+import com.stevesoltys.seedvault.backend.BackendManager
+import com.stevesoltys.seedvault.backend.saf.storagePluginModuleSaf
+import com.stevesoltys.seedvault.backend.webdav.storagePluginModuleWebDav
 import com.stevesoltys.seedvault.crypto.cryptoModule
 import com.stevesoltys.seedvault.header.headerModule
 import com.stevesoltys.seedvault.metadata.MetadataManager
 import com.stevesoltys.seedvault.metadata.metadataModule
-import com.stevesoltys.seedvault.backend.BackendManager
-import com.stevesoltys.seedvault.backend.saf.storagePluginModuleSaf
-import com.stevesoltys.seedvault.backend.webdav.storagePluginModuleWebDav
 import com.stevesoltys.seedvault.restore.install.installModule
 import com.stevesoltys.seedvault.restore.restoreUiModule
 import com.stevesoltys.seedvault.settings.AppListRetriever
@@ -63,7 +63,14 @@ open class App : Application() {
         single { SettingsManager(this@App) }
         single { BackupNotificationManager(this@App) }
         single { BackendManager(this@App, get(), get()) }
-        single { BackendFactory(this@App) }
+        single {
+            BackendFactory {
+                // uses context of the device's main user to be able to access USB storage
+                this@App.applicationContext.getStorageContext {
+                    get<SettingsManager>().getSafProperties()?.isUsb == true
+                }
+            }
+        }
         single { BackupStateManager(this@App) }
         single { Clock() }
         factory<IBackupManager> { IBackupManager.Stub.asInterface(getService(BACKUP_SERVICE)) }
@@ -215,6 +222,10 @@ fun <T> permitDiskReads(func: () -> T): T {
     }
 }
 
+/**
+ * Hack to allow other profiles access to USB backend.
+ * @return the context of the device's main user, so use with great care!
+ */
 @Suppress("MissingPermission")
 fun Context.getStorageContext(isUsbStorage: () -> Boolean): Context {
     if (checkSelfPermission(INTERACT_ACROSS_USERS_FULL) == PERMISSION_GRANTED && isUsbStorage()) {
diff --git a/core/Android.bp b/core/Android.bp
new file mode 100644
index 000000000..6922e7f55
--- /dev/null
+++ b/core/Android.bp
@@ -0,0 +1,35 @@
+//
+// SPDX-FileCopyrightText: 2021 The Calyx Institute
+// SPDX-License-Identifier: Apache-2.0
+//
+
+android_library {
+    name: "seedvault-lib-core",
+    sdk_version: "current",
+    srcs: [
+        "src/main/java/**/*.kt",
+        "src/main/java/**/*.java",
+    ],
+    exclude_srcs: [
+        "src/main/java/org/calyxos/seedvault/core/backends/BackendTest.kt",
+    ],
+    static_libs: [
+        "androidx.core_core-ktx",
+        "androidx.documentfile_documentfile",
+        "kotlinx-coroutines-android",
+        "kotlinx-coroutines-core",
+        "seedvault-lib-kotlin-logging-jvm",
+        "seedvault-lib-slf4j-api",
+        // WebDAV
+        "seedvault-lib-dav4jvm",
+        "seedvault-lib-okhttp",
+        "okio-lib",
+    ],
+    manifest: "src/main/AndroidManifest.xml",
+    optimize: {
+        enabled: false,
+    },
+    kotlincflags: [
+        "-opt-in=kotlin.RequiresOptIn",
+    ],
+}
diff --git a/core/build.gradle.kts b/core/build.gradle.kts
index 201768ab0..daed7a8f4 100644
--- a/core/build.gradle.kts
+++ b/core/build.gradle.kts
@@ -36,17 +36,17 @@ android {
 dependencies {
     val aospLibs: FileTree by rootProject.extra
     compileOnly(aospLibs)
-    compileOnly("org.ogce:xpp3:1.1.6")
     compileOnly(kotlin("test"))
     implementation(libs.bundles.kotlin)
     implementation(libs.bundles.coroutines)
     implementation(libs.androidx.documentfile)
     implementation(libs.androidx.core.ktx)
-    // implementation(fileTree("${rootProject.rootDir}/libs/dav4jvm").include("okio-jvm-3.7.0.jar"))
     implementation(fileTree("${rootProject.rootDir}/libs/dav4jvm").include("*.jar"))
-    implementation("io.github.oshai:kotlin-logging-jvm:6.0.3")
-    implementation("org.slf4j:slf4j-simple:2.0.3")
+    implementation(libs.squareup.okio)
+    implementation(libs.kotlin.logging)
+    implementation(libs.slf4j.api)
 
     testImplementation(kotlin("test"))
     testImplementation("org.ogce:xpp3:1.1.6")
+    testImplementation("org.slf4j:slf4j-simple:2.0.3")
 }
diff --git a/core/src/main/AndroidManifest.xml b/core/src/main/AndroidManifest.xml
index 6c244e77d..6099552b2 100644
--- a/core/src/main/AndroidManifest.xml
+++ b/core/src/main/AndroidManifest.xml
@@ -2,7 +2,8 @@
   SPDX-FileCopyrightText: 2021 The Calyx Institute
   SPDX-License-Identifier: Apache-2.0
   -->
-<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="org.calyxos.seedvault.core">
 
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
 </manifest>
diff --git a/core/src/main/java/org/calyxos/seedvault/core/Utils.kt b/core/src/main/java/org/calyxos/seedvault/core/Utils.kt
deleted file mode 100644
index 28982dfa6..000000000
--- a/core/src/main/java/org/calyxos/seedvault/core/Utils.kt
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
- * SPDX-FileCopyrightText: 2024 The Calyx Institute
- * SPDX-License-Identifier: Apache-2.0
- */
-
-package org.calyxos.seedvault.core
-
-import android.Manifest.permission.INTERACT_ACROSS_USERS_FULL
-import android.content.Context
-import android.content.pm.PackageManager.PERMISSION_GRANTED
-import android.os.UserManager
-
-/**
- * Hack to allow other profiles access to USB backend.
- * @return the context of the device's main user, so use with great care!
- */
-@Suppress("MissingPermission")
-public fun Context.getBackendContext(isUsbStorage: () -> Boolean): Context {
-    if (checkSelfPermission(INTERACT_ACROSS_USERS_FULL) == PERMISSION_GRANTED && isUsbStorage()) {
-        UserManager.get(this).getProfileParent(user)
-            ?.let { parent -> return createContextAsUser(parent, 0) }
-    }
-    return this
-}
diff --git a/core/src/main/java/org/calyxos/seedvault/core/backends/BackendFactory.kt b/core/src/main/java/org/calyxos/seedvault/core/backends/BackendFactory.kt
index 953e0c56c..f05bcb549 100644
--- a/core/src/main/java/org/calyxos/seedvault/core/backends/BackendFactory.kt
+++ b/core/src/main/java/org/calyxos/seedvault/core/backends/BackendFactory.kt
@@ -12,8 +12,10 @@ import org.calyxos.seedvault.core.backends.webdav.WebDavBackend
 import org.calyxos.seedvault.core.backends.webdav.WebDavConfig
 
 public class BackendFactory(
-    private val context: Context,
+    private val contextGetter: () -> Context,
 ) {
-    public fun createSafBackend(config: SafProperties): Backend = SafBackend(context, config)
+    public fun createSafBackend(config: SafProperties): Backend =
+        SafBackend(contextGetter(), config)
+
     public fun createWebDavBackend(config: WebDavConfig): Backend = WebDavBackend(config)
 }
diff --git a/core/src/main/java/org/calyxos/seedvault/core/backends/BackendProperties.kt b/core/src/main/java/org/calyxos/seedvault/core/backends/BackendProperties.kt
index f4d4acc6f..1b31136d3 100644
--- a/core/src/main/java/org/calyxos/seedvault/core/backends/BackendProperties.kt
+++ b/core/src/main/java/org/calyxos/seedvault/core/backends/BackendProperties.kt
@@ -5,10 +5,10 @@
 
 package org.calyxos.seedvault.core.backends
 
-import android.annotation.WorkerThread
 import android.content.Context
 import android.net.ConnectivityManager
 import android.net.NetworkCapabilities.NET_CAPABILITY_INTERNET
+import androidx.annotation.WorkerThread
 import at.bitfire.dav4jvm.exception.HttpException
 import java.io.IOException
 
diff --git a/core/src/main/java/org/calyxos/seedvault/core/backends/saf/SafBackend.kt b/core/src/main/java/org/calyxos/seedvault/core/backends/saf/SafBackend.kt
index bf7313372..028c521e9 100644
--- a/core/src/main/java/org/calyxos/seedvault/core/backends/saf/SafBackend.kt
+++ b/core/src/main/java/org/calyxos/seedvault/core/backends/saf/SafBackend.kt
@@ -29,7 +29,6 @@ import org.calyxos.seedvault.core.backends.FileHandle
 import org.calyxos.seedvault.core.backends.FileInfo
 import org.calyxos.seedvault.core.backends.LegacyAppBackupFile
 import org.calyxos.seedvault.core.backends.TopLevelFolder
-import org.calyxos.seedvault.core.getBackendContext
 import java.io.IOException
 import java.io.InputStream
 import java.io.OutputStream
@@ -41,17 +40,13 @@ internal const val ROOT_ID_DEVICE = "primary"
 private const val DEBUG_LOG = true
 
 public class SafBackend(
-    private val appContext: Context,
+    private val context: Context,
     private val safProperties: SafProperties,
     root: String = DIRECTORY_ROOT,
 ) : Backend {
 
     private val log = KotlinLogging.logger {}
 
-    /**
-     * Attention: This context might be from a different user. Use with care.
-     */
-    private val context: Context get() = appContext.getBackendContext { safProperties.isUsb }
     private val cache = DocumentFileCache(context, safProperties.getDocumentFile(context), root)
 
     override suspend fun test(): Boolean {
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index c4299fc03..e4c40d107 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -40,6 +40,10 @@ dokka = "1.9.20" # Dokka has no releases after 1.9.20
 # Lint versions
 lint-rules = { strictly = "0.1.0" }
 
+# Logging libs (check versions at /libs)
+logging = { strictly = "6.0.3" }
+slf4j-api = { strictly = "2.0.16" }
+
 # Google versions
 # https://android.googlesource.com/platform/external/protobuf/+/refs/tags/android-15.0.0_r1/java/pom.xml#7
 protobuf = { strictly = "3.21.12" }
@@ -74,6 +78,9 @@ androidx-documentfile = { strictly = "1.1.0-alpha01" } # 1.1.0-alpha02 in AOSP b
 # https://android.googlesource.com/platform/prebuilts/sdk/+/android-15.0.0_r1/current/androidx/m2repository/androidx/work/work-runtime-ktx?autodive=0
 androidx-work-runtime = { strictly = "2.10.0-alpha02" }
 
+# https://android.googlesource.com/platform/external/okio/+/refs/tags/android-14.0.0_r53/CHANGELOG.md
+squareup-okio = { strictly = "3.7.0" }
+
 [libraries]
 # Kotlin standard dependencies
 kotlin-stdlib = { module = "org.jetbrains.kotlin:kotlin-stdlib", version.ref = "kotlin" }
@@ -105,6 +112,10 @@ androidx-documentfile = { module = "androidx.documentfile:documentfile", version
 androidx-work-runtime-ktx = { module = "androidx.work:work-runtime-ktx", version.ref = "androidx-work-runtime" }
 androidx-room-runtime = { module = "androidx.room:room-runtime", version.ref = "room" }
 
+squareup-okio = { module= "com.squareup.okio:okio", version.ref = "squareup-okio" }
+kotlin-logging = { module = "io.github.oshai:kotlin-logging-jvm", version.ref = "logging" }
+slf4j-api = { module = "org.slf4j:slf4j-api", version.ref = "slf4j-api" }
+
 [bundles]
 kotlin = ["kotlin-stdlib", "kotlin-stdlib-jdk8", "kotlin-stdlib-common"]
 coroutines = ["kotlinx-coroutines-core-jvm", "kotlinx-coroutines-android"]
diff --git a/libs/Android.bp b/libs/Android.bp
index 33f511014..8a9c8e65c 100644
--- a/libs/Android.bp
+++ b/libs/Android.bp
@@ -8,3 +8,15 @@ java_import {
     jars: ["kotlin-bip39-jvm-1.0.6.jar"],
     sdk_version: "current",
 }
+
+java_import {
+    name: "seedvault-lib-kotlin-logging-jvm",
+    jars: ["kotlin-logging-jvm-6.0.3.jar"],
+    sdk_version: "current",
+}
+
+java_import {
+    name: "seedvault-lib-slf4j-api",
+    jars: ["slf4j-api-2.0.16.jar"],
+    sdk_version: "current",
+}
diff --git a/libs/dav4jvm/Android.bp b/libs/dav4jvm/Android.bp
index 660926629..ea70b04be 100644
--- a/libs/dav4jvm/Android.bp
+++ b/libs/dav4jvm/Android.bp
@@ -14,9 +14,3 @@ java_import {
     jars: ["okhttp-4.12.0.jar"],
     sdk_version: "current",
 }
-
-java_import {
-    name: "seedvault-lib-okio",
-    jars: ["okio-jvm-3.7.0.jar"],
-    sdk_version: "current",
-}
diff --git a/libs/dav4jvm/okio-jvm-3.7.0.jar b/libs/dav4jvm/okio-jvm-3.7.0.jar
deleted file mode 100644
index 8da081a91..000000000
Binary files a/libs/dav4jvm/okio-jvm-3.7.0.jar and /dev/null differ
diff --git a/libs/kotlin-logging-jvm-6.0.3.jar b/libs/kotlin-logging-jvm-6.0.3.jar
new file mode 100644
index 000000000..b9f78839b
Binary files /dev/null and b/libs/kotlin-logging-jvm-6.0.3.jar differ
diff --git a/libs/slf4j-api-2.0.16.jar b/libs/slf4j-api-2.0.16.jar
new file mode 100644
index 000000000..cbb5448d0
Binary files /dev/null and b/libs/slf4j-api-2.0.16.jar differ
diff --git a/storage/lib/Android.bp b/storage/lib/Android.bp
index d28d5c877..2cac46ca1 100644
--- a/storage/lib/Android.bp
+++ b/storage/lib/Android.bp
@@ -19,6 +19,7 @@ android_library {
         local_include_dirs: ["src/main/proto"],
     },
     static_libs: [
+        "seedvault-lib-core",
         "seedvault-lib-tink-android",
         "libprotobuf-java-lite",
         "androidx.core_core-ktx",
diff --git a/storage/lib/build.gradle.kts b/storage/lib/build.gradle.kts
index 49851eec9..5ada1faa4 100644
--- a/storage/lib/build.gradle.kts
+++ b/storage/lib/build.gradle.kts
@@ -94,9 +94,6 @@ dependencies {
     implementation(libs.androidx.room.runtime)
     implementation(libs.google.protobuf.javalite)
     implementation(libs.google.tink.android)
-    // TODO include via gradle and AOSP
-    //  https://android.googlesource.com/platform/external/okio/+/refs/tags/android-14.0.0_r53/CHANGELOG.md
-    implementation(fileTree("${rootProject.rootDir}/libs/dav4jvm").include("okio-jvm-3.7.0.jar"))
 
     ksp(group = "androidx.room", name = "room-compiler", version = libs.versions.room.get())
     lintChecks(libs.thirdegg.lint.rules)