diff --git a/core/build.gradle.kts b/core/build.gradle.kts
index 96f77274..80282cb6 100644
--- a/core/build.gradle.kts
+++ b/core/build.gradle.kts
@@ -1,3 +1,4 @@
+import com.codingfeline.buildkonfig.compiler.FieldSpec.Type.STRING
 import com.powersync.plugins.sonatype.setupGithubRepository
 import de.undercouch.gradle.tasks.download.Download
 import org.gradle.api.tasks.testing.logging.TestExceptionFormat
@@ -21,6 +22,7 @@ plugins {
     id("com.powersync.plugins.sonatype")
     alias(libs.plugins.mokkery)
     alias(libs.plugins.kotlin.atomicfu)
+    alias(libs.plugins.buildKonfig)
 }
 
 val binariesFolder = project.layout.buildDirectory.dir("binaries/desktop")
@@ -315,8 +317,19 @@ android {
 }
 
 androidComponents.onVariants {
-        tasks.named("preBuild") {
-            dependsOn(moveJDBCJNIFiles)
+    tasks.named("preBuild") {
+        dependsOn(moveJDBCJNIFiles)
+    }
+}
+
+buildkonfig {
+    packageName = "com.powersync.core"
+    defaultConfigs {
+        buildConfigField(STRING, "LIBRARY_VERSION", version.toString())
+
+        // TODO: Swift SDK relies on this too.
+        // Find out how to add a build flag to toggle between "powersync-kotlin" and "powersync-swift".
+        buildConfigField(STRING, "LIBRARY_NAME", "powersync-kotlin")
     }
 }
 
@@ -349,4 +362,13 @@ tasks.withType<KotlinTest> {
         showStackTraces = true
     }
 }
+
+tasks.formatKotlinCommonMain {
+    exclude { it.file.name == "BuildKonfig.kt" }
+}
+
+tasks.lintKotlinCommonMain {
+    exclude { it.file.name == "BuildKonfig.kt" }
+}
+
 setupGithubRepository()
diff --git a/core/src/androidMain/kotlin/com/powersync/sync/SyncStream.android.kt b/core/src/androidMain/kotlin/com/powersync/sync/SyncStream.android.kt
new file mode 100644
index 00000000..a9c4c67a
--- /dev/null
+++ b/core/src/androidMain/kotlin/com/powersync/sync/SyncStream.android.kt
@@ -0,0 +1,9 @@
+package com.powersync.sync
+
+import android.os.Build
+
+internal actual fun getOS(): String {
+    val base = Build.VERSION.BASE_OS
+    val version = Build.VERSION.SDK_INT
+    return "android $base/$version"
+}
diff --git a/core/src/commonMain/kotlin/com/powersync/sync/SyncStream.kt b/core/src/commonMain/kotlin/com/powersync/sync/SyncStream.kt
index 23b3e5ed..4f8155ad 100644
--- a/core/src/commonMain/kotlin/com/powersync/sync/SyncStream.kt
+++ b/core/src/commonMain/kotlin/com/powersync/sync/SyncStream.kt
@@ -8,6 +8,8 @@ import com.powersync.bucket.BucketStorage
 import com.powersync.bucket.Checkpoint
 import com.powersync.bucket.WriteCheckpointResponse
 import com.powersync.connectors.PowerSyncBackendConnector
+import com.powersync.core.BuildKonfig.LIBRARY_NAME
+import com.powersync.core.BuildKonfig.LIBRARY_VERSION
 import com.powersync.db.crud.CrudEntry
 import com.powersync.utils.JsonUtil
 import io.ktor.client.HttpClient
@@ -35,6 +37,22 @@ import kotlinx.coroutines.flow.flow
 import kotlinx.datetime.Clock
 import kotlinx.serialization.encodeToString
 import kotlinx.serialization.json.JsonObject
+import kotlin.collections.MutableSet
+import kotlin.collections.buildList
+import kotlin.collections.component1
+import kotlin.collections.component2
+import kotlin.collections.filter
+import kotlin.collections.forEach
+import kotlin.collections.isNotEmpty
+import kotlin.collections.joinToString
+import kotlin.collections.listOf
+import kotlin.collections.map
+import kotlin.collections.mutableMapOf
+import kotlin.collections.mutableSetOf
+import kotlin.collections.set
+import kotlin.collections.toList
+import kotlin.collections.toMutableList
+import kotlin.collections.toMutableSet
 
 internal class SyncStream(
     private val bucketStorage: BucketStorage,
@@ -172,7 +190,7 @@ internal class SyncStream(
                 contentType(ContentType.Application.Json)
                 headers {
                     append(HttpHeaders.Authorization, "Token ${credentials.token}")
-                    append("User-Id", credentials.userId ?: "")
+                    append("User-Agent", powerSyncUserAgent())
                 }
             }
         if (response.status.value == 401) {
@@ -186,6 +204,8 @@ internal class SyncStream(
         return body.data.writeCheckpoint
     }
 
+    private fun powerSyncUserAgent(): String = "$LIBRARY_NAME/$LIBRARY_VERSION ${getOS()}"
+
     private fun streamingSyncRequest(req: StreamingSyncRequest): Flow<String> =
         flow {
             val credentials = connector.getCredentialsCached()
@@ -200,7 +220,7 @@ internal class SyncStream(
                     contentType(ContentType.Application.Json)
                     headers {
                         append(HttpHeaders.Authorization, "Token ${credentials.token}")
-                        append("User-Id", credentials.userId ?: "")
+                        append("User-Agent", powerSyncUserAgent())
                     }
                     timeout { socketTimeoutMillis = Long.MAX_VALUE }
                     setBody(bodyJson)
@@ -449,6 +469,8 @@ internal class SyncStream(
     }
 }
 
+internal expect fun getOS(): String
+
 internal data class SyncStreamState(
     var targetCheckpoint: Checkpoint?,
     var validatedCheckpoint: Checkpoint?,
diff --git a/core/src/iosMain/kotlin/com/powersync/sync/SyncStream.ios.kt b/core/src/iosMain/kotlin/com/powersync/sync/SyncStream.ios.kt
new file mode 100644
index 00000000..66b9de39
--- /dev/null
+++ b/core/src/iosMain/kotlin/com/powersync/sync/SyncStream.ios.kt
@@ -0,0 +1,10 @@
+package com.powersync.sync
+
+import platform.UIKit.UIDevice
+
+internal actual fun getOS(): String {
+    val current = UIDevice.currentDevice
+    val version = current.systemVersion
+
+    return "ios $version"
+}
diff --git a/core/src/jvmMain/kotlin/com/powersync/sync/SyncStream.jvm.kt b/core/src/jvmMain/kotlin/com/powersync/sync/SyncStream.jvm.kt
new file mode 100644
index 00000000..e8dee744
--- /dev/null
+++ b/core/src/jvmMain/kotlin/com/powersync/sync/SyncStream.jvm.kt
@@ -0,0 +1,7 @@
+package com.powersync.sync
+
+internal actual fun getOS(): String {
+    val os = System.getProperty("os.name")
+    val version = System.getProperty("os.version")
+    return "jvm $os/$version"
+}
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 224c0422..a20ac503 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -30,7 +30,7 @@ compose-preview = "1.7.8"
 androidxSqlite = "2.4.0"
 
 # plugins
-android-gradle-plugin = "8.9.0"
+android-gradle-plugin = "8.9.1"
 kmmBridge = "0.5.7"
 skie = "0.10.1"
 maven-publish = "0.27.0"
@@ -40,6 +40,7 @@ mokkery = "2.7.1"
 kotlinter = "5.0.1"
 keeper = "0.16.1"
 atomicfu = "0.27.0"
+buildKonfig = "0.17.0"
 
 # Sample - Android
 androidx-core = "1.15.0"
@@ -128,6 +129,7 @@ kotlinter = { id = "org.jmailen.kotlinter", version.ref = "kotlinter" }
 keeper = { id = "com.slack.keeper", version.ref = "keeper" }
 kotlin-android = { id = "org.jetbrains.kotlin.android", version.ref = "kotlin" }
 kotlin-atomicfu = { id = "org.jetbrains.kotlinx.atomicfu", version.ref = "atomicfu" }
+buildKonfig = { id = "com.codingfeline.buildkonfig", version.ref = "buildKonfig" }
 
 [bundles]
 sqldelight = [