diff --git a/adapter-sdk-kotlin/src/main/kotlin/com/github/oslokommune/oslonokkelen/adapter/thing/ThingState.kt b/adapter-sdk-kotlin/src/main/kotlin/com/github/oslokommune/oslonokkelen/adapter/thing/ThingState.kt
index 88ed685..e0633c8 100644
--- a/adapter-sdk-kotlin/src/main/kotlin/com/github/oslokommune/oslonokkelen/adapter/thing/ThingState.kt
+++ b/adapter-sdk-kotlin/src/main/kotlin/com/github/oslokommune/oslonokkelen/adapter/thing/ThingState.kt
@@ -132,10 +132,13 @@ sealed class ThingState {
         val status : Status,
         val lastSeen: Instant?,
         val explanation: String?
-    ) : ThingState() {
+    ) : ThingState(), ComparableThingState {
 
         override val key = Key(thingId, "thing.${thingId.value}.online")
 
+        override fun hasSameStateAs(other: ThingState): Boolean {
+            return other is Online && lastSeen == other.lastSeen && status == other.status && explanation == other.explanation
+        }
 
         enum class Status {
             REPORTED_ONLINE, REPORTED_OFFLINE, ONLINE_STATUS_UNSUPPORTED
diff --git a/adapter-sdk-kotlin/src/main/kotlin/com/github/oslokommune/oslonokkelen/adapter/thing/ThingsStateSnapshot.kt b/adapter-sdk-kotlin/src/main/kotlin/com/github/oslokommune/oslonokkelen/adapter/thing/ThingsStateSnapshot.kt
index 6c2007b..0817326 100644
--- a/adapter-sdk-kotlin/src/main/kotlin/com/github/oslokommune/oslonokkelen/adapter/thing/ThingsStateSnapshot.kt
+++ b/adapter-sdk-kotlin/src/main/kotlin/com/github/oslokommune/oslonokkelen/adapter/thing/ThingsStateSnapshot.kt
@@ -11,6 +11,12 @@ data class ThingStateSnapshot(
     val data: PersistentMap<ThingState.Key, ThingState> = persistentMapOf()
 ) {
 
+    init {
+        if (data.keys.any { id -> id.thingId != thingId }) {
+            throw IllegalArgumentException("Tried to create snapshot of $thingId with state belonging to a different thing: $data")
+        }
+    }
+
     constructor(first: ThingState, vararg state: ThingState) : this(
         thingId = first.thingId,
         data = (state.toList() + first).associateBy { it.key }.toPersistentHashMap()
diff --git a/adapter-sdk-kotlin/src/test/kotlin/com/github/oslokommune/oslonokkelen/adapter/manifest/ManifestSnapshotTest.kt b/adapter-sdk-kotlin/src/test/kotlin/com/github/oslokommune/oslonokkelen/adapter/manifest/ManifestSnapshotTest.kt
index e75669b..8ab4388 100644
--- a/adapter-sdk-kotlin/src/test/kotlin/com/github/oslokommune/oslonokkelen/adapter/manifest/ManifestSnapshotTest.kt
+++ b/adapter-sdk-kotlin/src/test/kotlin/com/github/oslokommune/oslonokkelen/adapter/manifest/ManifestSnapshotTest.kt
@@ -9,14 +9,15 @@ import com.github.oslokommune.oslonokkelen.adapter.thing.ThingDescription
 import com.github.oslokommune.oslonokkelen.adapter.thing.ThingId
 import com.github.oslokommune.oslonokkelen.adapter.thing.ThingState
 import com.github.oslokommune.oslonokkelen.adapter.thing.ThingStateSnapshot
+import java.time.Instant
 import kotlinx.collections.immutable.persistentListOf
 import kotlinx.collections.immutable.persistentMapOf
 import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Assertions.assertSame
 import org.junit.jupiter.api.Nested
 import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.assertThrows
-import java.time.Instant
 
 internal class ManifestSnapshotTest {
 
@@ -397,4 +398,69 @@ internal class ManifestSnapshotTest {
     }
 
 
+    @Nested
+    inner class Debug {
+
+        @Test
+        fun `Add thing to empty manifest`() {
+            val original = ManifestSnapshot()
+            val door = createThingDescription("door")
+            val withDoor = original + door
+
+            val expectedManifest = ManifestSnapshot(
+                version = 2,
+                things = persistentMapOf(door.id to door)
+            )
+
+            assertEquals(expectedManifest, withDoor)
+        }
+
+        @Test
+        fun `Update thing description`() {
+            val original = ManifestSnapshot()
+            val originalDoor = createThingDescription("door", "First door description")
+            val updatedDoor = createThingDescription("door", "Second door description")
+            val withOriginalDoor = original + originalDoor
+            val withUpdatedDoor = withOriginalDoor + updatedDoor
+
+            val expectedManifest = ManifestSnapshot(
+                version = 3,
+                things = persistentMapOf(originalDoor.id to updatedDoor)
+            )
+
+            assertEquals(expectedManifest, withUpdatedDoor)
+        }
+
+        @Test
+        fun `Should keep state when updating description`() {
+            val original = ManifestSnapshot()
+            val originalDoor = createThingDescription("door", "First door description")
+            val updatedDoor = createThingDescription("door", "Second door description")
+            val withOriginalDoor = original + originalDoor
+            val openState = ThingState.OpenPosition(timestamp = Instant.now(), originalDoor.id, open = true)
+            val withOriginalDoorAndState = withOriginalDoor + openState
+            val withUpdatedDoorAndState = withOriginalDoorAndState + updatedDoor
+
+            val expectedManifest = ManifestSnapshot(
+                version = 4,
+                things = persistentMapOf(originalDoor.id to updatedDoor),
+                thingStates = persistentMapOf(originalDoor.id to ThingStateSnapshot(openState))
+            )
+
+            assertEquals(expectedManifest, withUpdatedDoorAndState)
+        }
+
+    }
+
+    private fun createThingDescription(id: String, description: String = "Description of $id"): ThingDescription {
+        return ThingDescription(
+            id = ThingId(id),
+            description = description,
+            adminRole = "admin_role",
+            tags = emptySet(),
+            link = null,
+            timeWithoutMessageBeforeAlert = null
+        )
+    }
+
 }
\ No newline at end of file
diff --git a/adapter-sdk-kotlin/src/test/kotlin/com/github/oslokommune/oslonokkelen/adapter/protobuf/ProtobufSerializerTest.kt b/adapter-sdk-kotlin/src/test/kotlin/com/github/oslokommune/oslonokkelen/adapter/protobuf/ProtobufSerializerTest.kt
index 600ad56..0f8a782 100644
--- a/adapter-sdk-kotlin/src/test/kotlin/com/github/oslokommune/oslonokkelen/adapter/protobuf/ProtobufSerializerTest.kt
+++ b/adapter-sdk-kotlin/src/test/kotlin/com/github/oslokommune/oslonokkelen/adapter/protobuf/ProtobufSerializerTest.kt
@@ -186,6 +186,14 @@ internal class ProtobufSerializerTest {
 
         private val timestamp = Instant.now().truncatedTo(ChronoUnit.SECONDS)
 
+        private val deviceType = ThingState.DeviceType(
+            timestamp = timestamp,
+            thingId = frontDoor.id,
+            vendor = "Armin",
+            model = "Oslonøkkelboksen",
+            firmwareVersion = "v0.5.55"
+        )
+
         @Test
         fun `Serialize and parse manifest with thing`() {
             test(ManifestSnapshot() + frontDoor)
@@ -196,6 +204,11 @@ internal class ProtobufSerializerTest {
             test(ManifestSnapshot() + frontDoor + unlockFrontDoor)
         }
 
+        @Test
+        fun `Serialize and parse manifest with reported firmware`() {
+            test(ManifestSnapshot() + frontDoor + deviceType)
+        }
+
         @Test
         fun `Serialize and parse manifest with locked door`() {
             val lockedDoor = ThingState.Lock(