diff --git a/core/events/src/main/kotlin/com/correx/core/events/events/JournalCompactedEvent.kt b/core/events/src/main/kotlin/com/correx/core/events/events/JournalCompactedEvent.kt
new file mode 100644
index 00000000..97af9f37
--- /dev/null
+++ b/core/events/src/main/kotlin/com/correx/core/events/events/JournalCompactedEvent.kt
@@ -0,0 +1,15 @@
+package com.correx.core.events.events
+
+import com.correx.core.events.types.ArtifactId
+import com.correx.core.events.types.SessionId
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+@Serializable
+@SerialName("JournalCompacted")
+data class JournalCompactedEvent(
+    val sessionId: SessionId,
+    val coversThroughSequence: Long,
+    val summaryArtifactId: ArtifactId,
+    val lowSalienceOmittedCount: Int,
+) : EventPayload
diff --git a/core/events/src/main/kotlin/com/correx/core/events/serialization/Serialization.kt b/core/events/src/main/kotlin/com/correx/core/events/serialization/Serialization.kt
index bf5efde9..2b43625f 100644
--- a/core/events/src/main/kotlin/com/correx/core/events/serialization/Serialization.kt
+++ b/core/events/src/main/kotlin/com/correx/core/events/serialization/Serialization.kt
@@ -14,6 +14,7 @@ import com.correx.core.events.events.SessionWorkspaceBoundEvent
 import com.correx.core.events.events.ContextTruncatedEvent
 import com.correx.core.events.events.EventPayload
 import com.correx.core.events.events.ExecutionPlanLockedEvent
+import com.correx.core.events.events.JournalCompactedEvent
 import com.correx.core.events.events.FileWrittenEvent
 import com.correx.core.events.events.L3MemoryRetrievedEvent
 import com.correx.core.events.events.InferenceCompletedEvent
@@ -93,6 +94,7 @@ val eventModule = SerializersModule {
         subclass(L3MemoryRetrievedEvent::class)
         subclass(ContextTruncatedEvent::class)
         subclass(ExecutionPlanLockedEvent::class)
+        subclass(JournalCompactedEvent::class)
     }
 }
 
diff --git a/core/events/src/test/kotlin/com/correx/core/events/serialization/JournalCompactedEventSerializationTest.kt b/core/events/src/test/kotlin/com/correx/core/events/serialization/JournalCompactedEventSerializationTest.kt
new file mode 100644
index 00000000..4dc8cd9e
--- /dev/null
+++ b/core/events/src/test/kotlin/com/correx/core/events/serialization/JournalCompactedEventSerializationTest.kt
@@ -0,0 +1,26 @@
+package com.correx.core.events.serialization
+
+import com.correx.core.events.events.EventPayload
+import com.correx.core.events.events.JournalCompactedEvent
+import com.correx.core.events.types.ArtifactId
+import com.correx.core.events.types.SessionId
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+class JournalCompactedEventSerializationTest {
+
+    @Test
+    fun `JournalCompactedEvent round-trips as polymorphic EventPayload`() {
+        val sample: EventPayload = JournalCompactedEvent(
+            sessionId = SessionId("s1"),
+            coversThroughSequence = 42L,
+            summaryArtifactId = ArtifactId("summary-1"),
+            lowSalienceOmittedCount = 7,
+        )
+        val encoded = eventJson.encodeToString(EventPayload.serializer(), sample)
+        assertTrue(encoded.contains("\"type\":\"JournalCompacted\""), "SerialName must be present: $encoded")
+        val decoded = eventJson.decodeFromString(EventPayload.serializer(), encoded)
+        assertEquals(sample, decoded)
+    }
+}