diff --git a/src/main/java/com/clearfolio/viewer/repository/InMemoryConversionJobRepository.java b/src/main/java/com/clearfolio/viewer/repository/InMemoryConversionJobRepository.java
index 74da3832..8b074888 100644
--- a/src/main/java/com/clearfolio/viewer/repository/InMemoryConversionJobRepository.java
+++ b/src/main/java/com/clearfolio/viewer/repository/InMemoryConversionJobRepository.java
@@ -238,10 +238,17 @@ public List<ConversionJobLifecycleEvent> findLifecycleEventsByJobId(UUID jobId)
     /**
      * Returns lifecycle events for a tenant.
      *
+     * <p>Missing or blank scoped tenant identifiers fail closed and never infer
+     * the explicit legacy demo tenant.</p>
+     *
      * @param tenantId tenant identifier
-     * @return append-only lifecycle events for the tenant
+     * @return append-only lifecycle events for the tenant, or an empty list when
+     *         scoped tenant context is absent
      */
     public List<ConversionJobLifecycleEvent> findLifecycleEventsByTenantId(String tenantId) {
+        if (tenantId == null || tenantId.isBlank()) {
+            return List.of();
+        }
         String normalizedTenantId = normalizeTenantId(tenantId);
         return lifecycleEvents.stream()
                 .filter(event -> event.tenantId().equals(normalizedTenantId))
@@ -379,7 +386,7 @@ private String contentKey(String tenantId, String contentHash) {
     }
 
     private String normalizeTenantId(String tenantId) {
-        return tenantId == null || tenantId.isBlank() ? "buyer-demo" : tenantId.strip();
+        return Objects.requireNonNull(tenantId, "tenantId").strip();
     }
 
     private boolean matchesContentIndex(ConversionJob job, String expectedContentKey) {
diff --git a/src/test/java/com/clearfolio/viewer/repository/InMemoryConversionJobRepositoryTenantLifecycleIsolationTest.java b/src/test/java/com/clearfolio/viewer/repository/InMemoryConversionJobRepositoryTenantLifecycleIsolationTest.java
new file mode 100644
index 00000000..7a0c9828
--- /dev/null
+++ b/src/test/java/com/clearfolio/viewer/repository/InMemoryConversionJobRepositoryTenantLifecycleIsolationTest.java
@@ -0,0 +1,37 @@
+package com.clearfolio.viewer.repository;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.UUID;
+
+import org.junit.jupiter.api.Test;
+
+import com.clearfolio.viewer.model.ConversionJob;
+
+/**
+ * Verifies that lifecycle-event queries never infer the demo tenant from a
+ * missing scoped tenant identifier.
+ */
+class InMemoryConversionJobRepositoryTenantLifecycleIsolationTest {
+
+    @Test
+    void nullAndBlankTenantQueriesCannotReadDemoLifecycleEvents() {
+        InMemoryConversionJobRepository repository = new InMemoryConversionJobRepository();
+        ConversionJob demoJob = new ConversionJob(
+                UUID.fromString("11111111-2222-3333-4444-555555555555"),
+                "buyer-demo",
+                "subject-demo",
+                "report.pdf",
+                "application/pdf",
+                "tenant-lifecycle-isolation-hash",
+                42L,
+                3
+        );
+        repository.findOrStoreByContentHash(demoJob);
+
+        assertEquals(1, repository.findLifecycleEventsByTenantId("buyer-demo").size());
+        assertTrue(repository.findLifecycleEventsByTenantId(null).isEmpty());
+        assertTrue(repository.findLifecycleEventsByTenantId("   ").isEmpty());
+    }
+}