diff --git a/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java b/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java
index 3ee96b9e8..8bfb1488c 100644
--- a/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java
+++ b/src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java
@@ -176,19 +176,19 @@ public UUID submit(MultipartFile file, PolicyOverrideRequest overrideRequest) {
      */
     @Override
     public UUID submit(MultipartFile file, PolicyOverrideRequest overrideRequest, TenantContext tenantContext) {
+        if (tenantContext == null) {
+            throw new IllegalArgumentException("tenant context is required");
+        }
         PolicyOverrideRequest effectiveOverride = overrideRequest == null
                 ? PolicyOverrideRequest.none()
                 : overrideRequest;
-        TenantContext effectiveTenant = tenantContext == null
-                ? new TenantContext(TenantContext.DEMO_TENANT_ID, TenantContext.DEMO_SUBJECT_ID, java.util.Set.of())
-                : tenantContext;
         validationService.validateOrThrow(file, effectiveOverride);
 
         String contentHash = contentHash(file);
         ConversionJob job = new ConversionJob(
                 UUID.randomUUID(),
-                effectiveTenant.tenantId(),
-                effectiveTenant.subjectId(),
+                tenantContext.tenantId(),
+                tenantContext.subjectId(),
                 sanitizeFilename(file.getOriginalFilename()),
                 file.getContentType(),
                 contentHash,
diff --git a/src/test/java/com/clearfolio/viewer/service/DefaultDocumentConversionServiceTenantAuthorityTest.java b/src/test/java/com/clearfolio/viewer/service/DefaultDocumentConversionServiceTenantAuthorityTest.java
new file mode 100644
index 000000000..2b5151739
--- /dev/null
+++ b/src/test/java/com/clearfolio/viewer/service/DefaultDocumentConversionServiceTenantAuthorityTest.java
@@ -0,0 +1,49 @@
+package com.clearfolio.viewer.service;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verifyNoInteractions;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.mock.web.MockMultipartFile;
+
+import com.clearfolio.viewer.artifact.ArtifactStore;
+import com.clearfolio.viewer.config.ConversionProperties;
+import com.clearfolio.viewer.repository.ConversionJobRepository;
+
+/**
+ * Verifies that the production tenant-aware submission boundary never invents
+ * demo authority when an authenticated tenant context is absent.
+ */
+class DefaultDocumentConversionServiceTenantAuthorityTest {
+
+    @Test
+    void tenantAwareSubmitRejectsMissingAuthorityBeforeAnyDocumentOrJobWork() {
+        ConversionJobRepository repository = mock(ConversionJobRepository.class);
+        DocumentValidationService validationService = mock(DocumentValidationService.class);
+        ConversionWorker worker = mock(ConversionWorker.class);
+        ArtifactStore artifactStore = mock(ArtifactStore.class);
+        DefaultDocumentConversionService service = new DefaultDocumentConversionService(
+                repository,
+                validationService,
+                worker,
+                artifactStore,
+                new ConversionProperties()
+        );
+        MockMultipartFile file = new MockMultipartFile(
+                "file",
+                "contract.docx",
+                "application/octet-stream",
+                "sensitive-document".getBytes(java.nio.charset.StandardCharsets.UTF_8)
+        );
+
+        IllegalArgumentException exception = assertThrows(
+                IllegalArgumentException.class,
+                () -> service.submit(file, PolicyOverrideRequest.none(), null)
+        );
+
+        assertEquals("tenant context is required", exception.getMessage());
+        verifyNoInteractions(validationService, repository, worker, artifactStore);
+    }
+}
diff --git a/src/test/java/com/clearfolio/viewer/service/DefaultDocumentConversionServiceTest.java b/src/test/java/com/clearfolio/viewer/service/DefaultDocumentConversionServiceTest.java
index 8d18efa00..57a313673 100644
--- a/src/test/java/com/clearfolio/viewer/service/DefaultDocumentConversionServiceTest.java
+++ b/src/test/java/com/clearfolio/viewer/service/DefaultDocumentConversionServiceTest.java
@@ -260,7 +260,7 @@ void submitStoresTenantAndSubjectMetadataOnJob() {
     }
 
     @Test
-    void submitWithNullTenantContextFallsBackToDemoOwnership() {
+    void submitWithNullTenantContextFailsClosed() {
         ConversionJobRepository repository = new InMemoryConversionJobRepository();
         RecordingConversionWorker worker = new RecordingConversionWorker();
         DocumentConversionService service = new DefaultDocumentConversionService(
@@ -277,11 +277,14 @@ void submitWithNullTenantContextFallsBackToDemoOwnership() {
                 "hello-viewer".getBytes()
         );
 
-        UUID jobId = service.submit(file, PolicyOverrideRequest.none(), null);
+        IllegalArgumentException error = assertThrows(
+                IllegalArgumentException.class,
+                () -> service.submit(file, PolicyOverrideRequest.none(), null)
+        );
 
-        ConversionJob job = repository.findById(jobId).orElseThrow();
-        assertEquals(TenantContext.DEMO_TENANT_ID, job.getTenantId());
-        assertEquals(TenantContext.DEMO_SUBJECT_ID, job.getSubjectId());
+        assertEquals("tenant context is required", error.getMessage());
+        assertTrue(repository.findAll().isEmpty());
+        assertEquals(0, worker.enqueuedCount());
     }
 
     @Test