diff --git a/core/events/src/main/kotlin/com/correx/core/events/events/RepoMapEvents.kt b/core/events/src/main/kotlin/com/correx/core/events/events/RepoMapEvents.kt
new file mode 100644
index 00000000..f3d2f0a9
--- /dev/null
+++ b/core/events/src/main/kotlin/com/correx/core/events/events/RepoMapEvents.kt
@@ -0,0 +1,28 @@
+package com.correx.core.events.events
+
+import com.correx.core.events.types.SessionId
+import kotlinx.datetime.Instant
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+/** A single ranked entry in a repo map: a path, its relevance [score], and symbol names. */
+@Serializable
+data class RepoMapEntry(
+    val path: String,
+    val score: Double,
+    val symbols: List<String> = emptyList(),
+)
+
+/**
+ * Environment observation (invariant #9): the repo map computed once at the moment it ran.
+ * Replay reads these recorded facts and never re-scans the filesystem. Paths + symbol names
+ * only — never file bodies — so it is referenced, not inlined.
+ */
+@Serializable
+@SerialName("RepoMapComputed")
+data class RepoMapComputedEvent(
+    val sessionId: SessionId,
+    val repoRoot: String,
+    val entries: List<RepoMapEntry>,
+    val computedAt: Instant,
+) : 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 1db44e84..e608d4eb 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
@@ -24,6 +24,7 @@ import com.correx.core.events.events.ModelUnloadedEvent
 import com.correx.core.events.events.OrchestrationPausedEvent
 import com.correx.core.events.events.OrchestrationResumedEvent
 import com.correx.core.events.events.RefinementIterationEvent
+import com.correx.core.events.events.RepoMapComputedEvent
 import com.correx.core.events.events.RetryAttemptedEvent
 import com.correx.core.events.events.RiskAssessedEvent
 import com.correx.core.events.events.StageCompletedEvent
@@ -80,6 +81,7 @@ val eventModule = SerializersModule {
         subclass(WorkflowCompletedEvent::class)
         subclass(RetryAttemptedEvent::class)
         subclass(RefinementIterationEvent::class)
+        subclass(RepoMapComputedEvent::class)
         subclass(RiskAssessedEvent::class)
         subclass(ChatSessionStartedEvent::class)
         subclass(ChatTurnEvent::class)
diff --git a/testing/replay/src/test/kotlin/RepoMapReplayTest.kt b/testing/replay/src/test/kotlin/RepoMapReplayTest.kt
new file mode 100644
index 00000000..de0f3822
--- /dev/null
+++ b/testing/replay/src/test/kotlin/RepoMapReplayTest.kt
@@ -0,0 +1,47 @@
+import com.correx.core.events.events.EventMetadata
+import com.correx.core.events.events.NewEvent
+import com.correx.core.events.events.RepoMapComputedEvent
+import com.correx.core.events.events.RepoMapEntry
+import com.correx.core.events.events.StoredEvent
+import com.correx.core.events.types.EventId
+import com.correx.core.events.types.SessionId
+import com.correx.core.sessions.projections.Projection
+import com.correx.core.sessions.projections.replay.DefaultEventReplayer
+import com.correx.infrastructure.persistence.InMemoryEventStore
+import kotlinx.coroutines.runBlocking
+import kotlinx.datetime.Instant
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+/** Collects the latest recorded repo map purely from events — never touches the filesystem. */
+private class RepoMapProjection : Projection<List<RepoMapEntry>> {
+    override fun initial(): List<RepoMapEntry> = emptyList()
+    override fun apply(state: List<RepoMapEntry>, event: StoredEvent): List<RepoMapEntry> =
+        when (val p = event.payload) {
+            is RepoMapComputedEvent -> p.entries
+            else -> state
+        }
+}
+
+class RepoMapReplayTest {
+
+    @Test
+    fun `repo map is reconstructed from the recorded event without re-scanning`(): Unit = runBlocking {
+        val sessionId = SessionId("s")
+        val store = InMemoryEventStore()
+        val entries = listOf(
+            RepoMapEntry("src/Main.kt", 0.9, listOf("main", "boot")),
+            RepoMapEntry("src/Util.kt", 0.4, listOf("clamp")),
+        )
+        store.append(
+            NewEvent(
+                EventMetadata(EventId("rm"), sessionId, Instant.parse("2026-06-04T00:00:00Z"), 1, null, null),
+                RepoMapComputedEvent(sessionId, "/repo", entries, Instant.parse("2026-06-04T00:00:00Z")),
+            ),
+        )
+
+        val rebuilt = DefaultEventReplayer(store, RepoMapProjection()).rebuild(sessionId)
+
+        assertEquals(entries, rebuilt)
+    }
+}