diff --git a/VERSION b/VERSION
index f1cd7fa..fa2d855 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.1.49
+2.1.50
diff --git a/containers/chameleon/Dockerfile.chameleon b/containers/chameleon/Dockerfile.chameleon
index a608e77..5c3e90c 100644
--- a/containers/chameleon/Dockerfile.chameleon
+++ b/containers/chameleon/Dockerfile.chameleon
@@ -13,7 +13,7 @@
 # limitations under the License.
 
 # xosproject/chameleon
-FROM xosproject/xos-base:2.1.49
+FROM xosproject/xos-base:2.1.50
 
 # xos-base already has protoc and dependencies installed
 
diff --git a/containers/xos/Dockerfile.client b/containers/xos/Dockerfile.client
index a6a229b..3b00725 100644
--- a/containers/xos/Dockerfile.client
+++ b/containers/xos/Dockerfile.client
@@ -13,7 +13,7 @@
 # limitations under the License.
 
 # xosproject/xos-client
-FROM xosproject/xos-libraries:2.1.49
+FROM xosproject/xos-libraries:2.1.50
 
 
 # Install XOS client
diff --git a/containers/xos/Dockerfile.libraries b/containers/xos/Dockerfile.libraries
index eeb22a8..6ab827f 100644
--- a/containers/xos/Dockerfile.libraries
+++ b/containers/xos/Dockerfile.libraries
@@ -13,7 +13,7 @@
 # limitations under the License.
 
 # xosproject/xos-libraries
-FROM xosproject/xos-base:2.1.49
+FROM xosproject/xos-base:2.1.50
 
 # Add libraries
 COPY lib /opt/xos/lib
diff --git a/containers/xos/Dockerfile.synchronizer-base b/containers/xos/Dockerfile.synchronizer-base
index 06d9fa0..5a64c55 100644
--- a/containers/xos/Dockerfile.synchronizer-base
+++ b/containers/xos/Dockerfile.synchronizer-base
@@ -13,7 +13,7 @@
 # limitations under the License.
 
 # xosproject/xos-synchronizer-base
-FROM xosproject/xos-client:2.1.49
+FROM xosproject/xos-client:2.1.50
 
 COPY xos/synchronizers/new_base /opt/xos/synchronizers/new_base
 COPY xos/xos/logger.py /opt/xos/xos/logger.py
diff --git a/containers/xos/Dockerfile.xos-core b/containers/xos/Dockerfile.xos-core
index 4b30bdf..c9045ef 100644
--- a/containers/xos/Dockerfile.xos-core
+++ b/containers/xos/Dockerfile.xos-core
@@ -13,7 +13,7 @@
 # limitations under the License.
 
 # xosproject/xos-core
-FROM xosproject/xos-libraries:2.1.49
+FROM xosproject/xos-libraries:2.1.50
 
 # Install XOS
 ADD xos /opt/xos
diff --git a/xos/coreapi/dynamicbuild.py b/xos/coreapi/dynamicbuild.py
index cc55fac..958aec4 100644
--- a/xos/coreapi/dynamicbuild.py
+++ b/xos/coreapi/dynamicbuild.py
@@ -29,8 +29,13 @@
 
 
 class DynamicBuilder(object):
-    NOTHING_TO_DO = 0
-    SOMETHING_CHANGED = 1
+    # These constants must agree with what is declared in dnyamicload.proto
+    SUCCESS = 0
+    SUCCESS_NOTHING_CHANGED = 1
+    ERROR = 101
+    ERROR_LIVE_MODELS = 102
+    ERROR_DELETION_IN_PROGRESS = 103
+    TRYAGAIN = 201
 
     def __init__(self, base_dir=DEFAULT_BASE_DIR):
         self.services_dir = os.path.join(base_dir, "dynamic_services")
@@ -46,7 +51,7 @@
     def pre_validate_file(self, item):
         # various filename validations
         #   alphas (upper and lower), digits, underscore, dash, and period.
-        if not re.match("^[\w.-]+$", item.filename):
+        if not re.match("^[\w.-]+$", item.filename):  # noqa: W605
             raise Exception("illegal character in filename %s" % item.filename)
 
     def pre_validate_python(self, item):
@@ -119,7 +124,7 @@
                 "Models are already up-to-date; skipping dynamic load.",
                 name=request.name,
             )
-            return self.NOTHING_TO_DO
+            return self.SUCCESS_NOTHING_CHANGED
 
         self.pre_validate_models(request)
 
@@ -132,12 +137,26 @@
 
         log.info("Finished LoadModels request", name=request.name)
 
-        return self.SOMETHING_CHANGED
+        return self.SUCCESS
 
-    def handle_unloadmodels_request(self, request):
+    def handle_unloadmodels_request(self, request, models):
         (manifest, manifest_fn) = self.load_manifest_from_request(request)
 
-        # TODO: Check version number to make sure this is not a downgrade ?
+        for (name, model) in models.items():
+            if model.objects.exists():
+                if request.cleanup_behavior == request.REQUIRE_CLEAN:
+                    return self.ERROR_LIVE_MODELS
+                elif request.cleanup_behavior == request.AUTOMATICALLY_CLEAN:
+                    # Deleting the model will add it to model.deleted_objects automatically, and it will be caught
+                    # by the next loop and return a TRYAGAIN as necessary.
+                    model.objects.all().delete()
+
+        for (name, model) in models.items():
+            if model.deleted_objects.exists():
+                if request.cleanup_behavior == request.REQUIRE_CLEAN:
+                    return self.ERROR_DELETION_IN_PROGRESS
+                elif request.cleanup_behavior == request.AUTOMATICALLY_CLEAN:
+                    return self.TRYAGAIN
 
         hash = self.generate_request_hash(request, state="unload")
         if hash == manifest.get("hash"):
@@ -147,7 +166,7 @@
                 "Models are already up-to-date; skipping dynamic unload.",
                 name=request.name,
             )
-            return self.NOTHING_TO_DO
+            return self.SUCCESS_NOTHING_CHANGED
 
         manifest = self.save_models(request, state="unload", hash=hash)
 
@@ -158,7 +177,7 @@
 
         log.info("Finished UnloadModels request", name=request.name)
 
-        return self.SOMETHING_CHANGED
+        return self.SUCCESS
 
     def generate_request_hash(self, request, state):
         # TODO: could we hash the request rather than individually hashing the subcomponents of the request?
diff --git a/xos/coreapi/protos/dynamicload.proto b/xos/coreapi/protos/dynamicload.proto
index 38b55fc..192ee42 100644
--- a/xos/coreapi/protos/dynamicload.proto
+++ b/xos/coreapi/protos/dynamicload.proto
@@ -47,14 +47,25 @@
 message LoadModelsReply {
     enum LoadModelsStatus {
         SUCCESS = 0;
-        ERROR = 1;
+        SUCCESS_NOTHING_CHANGED = 1;      // Succeeded by not doing anything
+        ERROR = 101;                      // Unspecified Error
+        ERROR_LIVE_MODELS = 102;          // Live models are present during unload request
+        ERROR_DELETION_IN_PROGRESS = 103; // Soft-deleted models are present, waiting for delete steps
+        TRYAGAIN = 201;                   // Caller should try again
     }
     LoadModelsStatus status = 1;
 };
 
 message UnloadModelsRequest {
+    enum CleanupBehavior {
+        REQUIRE_CLEAN = 0;          // Return an error if live data is present (DEFAULT)
+        AUTOMATICALLY_CLEAN = 1;    // Automatically delete live data, return an in-progress response as necessary
+        PURGE = 2;                  // Forcibly purge database tables without running delete steps
+    };
+
     string name = 1;
     string version = 2;
+    CleanupBehavior cleanup_behavior = 3;
 };
 
 message ServiceModelStatus {
diff --git a/xos/coreapi/test_dynamicbuild.py b/xos/coreapi/test_dynamicbuild.py
index 6982747..3f464d1 100644
--- a/xos/coreapi/test_dynamicbuild.py
+++ b/xos/coreapi/test_dynamicbuild.py
@@ -17,7 +17,7 @@
 import shutil
 import tempfile
 import unittest
-from mock import patch
+from mock import patch, MagicMock, Mock
 
 from xosconfig import Config
 
@@ -39,7 +39,12 @@
 
 
 class DynamicUnloadRequest:
+    REQUIRE_CLEAN = 0
+    AUTOMATICALLY_CLEAN = 1
+    PURGE = 2
+
     def __init__(self, **kwargs):
+        self.cleanup_behavior = self.REQUIRE_CLEAN
         for (k, v) in kwargs.items():
             setattr(self, k, v)
 
@@ -216,7 +221,7 @@
             run_xosgenx_service.assert_called()
             remove_service.assert_not_called()
 
-            self.assertEqual(result, self.builder.SOMETHING_CHANGED)
+            self.assertEqual(result, self.builder.SUCCESS)
 
             self.assertTrue(os.path.exists(self.builder.manifest_dir))
             self.assertTrue(
@@ -268,7 +273,7 @@
             run_xosgenx_service.assert_called()
             remove_service.assert_not_called()
 
-            self.assertEqual(result, self.builder.SOMETHING_CHANGED)
+            self.assertEqual(result, self.builder.SUCCESS)
 
             self.assertTrue(os.path.exists(self.builder.manifest_dir))
             self.assertTrue(
@@ -295,7 +300,9 @@
             )
             self.assertEqual(manifest.get("state"), "load")
 
-            self.assertEqual(manifest.get("migrations"), [{u'filename': u'migration1.py'}, {u'filename': u'migration2.py'}])
+            self.assertEqual(
+                manifest.get("migrations"),
+                [{u'filename': u'migration1.py'}, {u'filename': u'migration2.py'}])
 
     def test_handle_unloadmodels_request(self):
         with patch.object(
@@ -310,14 +317,15 @@
             wraps=self.builder.remove_service,
         ) as remove_service:
             result = self.builder.handle_unloadmodels_request(
-                self.example_unload_request
+                self.example_unload_request,
+                {}
             )
 
             save_models.assert_called()
             run_xosgenx_service.assert_not_called()
             remove_service.assert_called()
 
-            self.assertEqual(result, self.builder.SOMETHING_CHANGED)
+            self.assertEqual(result, self.builder.SUCCESS)
 
             self.assertTrue(os.path.exists(self.builder.manifest_dir))
             self.assertTrue(
@@ -333,12 +341,95 @@
             )
             self.assertEqual(manifest.get("state"), "unload")
 
+    def test_handle_unloadmodels_request_live_models(self):
+        with patch.object(
+            dynamicbuild.DynamicBuilder, "save_models", wraps=self.builder.save_models
+        ) as save_models, patch.object(
+            dynamicbuild.DynamicBuilder,
+            "remove_service",
+            wraps=self.builder.remove_service,
+        ) as remove_service:
+            someobject = Mock()
+            somemodel = MagicMock()
+            somemodel.objects.all.return_value = [someobject]
+            somemodel.objects.exists.return_value = True
+
+            # Test with cleanup_behavior = REQUIRE_CLEAN
+
+            result = self.builder.handle_unloadmodels_request(
+                self.example_unload_request,
+                {"somemodel": somemodel, }
+            )
+
+            save_models.assert_not_called()
+            remove_service.assert_not_called()
+
+            self.assertEqual(result, self.builder.ERROR_LIVE_MODELS)
+
+            # Test with cleanup_behavior = AUTOMATICALLY_CLEAN
+
+            self.example_unload_request.cleanup_behavior = self.example_unload_request.AUTOMATICALLY_CLEAN
+            somemodel.objects.exists.return_value = False
+            somemodel.deleted_objects.all.return_value = [someobject]
+
+            result = self.builder.handle_unloadmodels_request(
+                self.example_unload_request,
+                {"somemodel": somemodel, }
+            )
+
+            save_models.assert_not_called()
+            remove_service.assert_not_called()
+
+            self.assertEqual(result, self.builder.TRYAGAIN)
+
+            # Test with cleanup_behavior = PURGE
+
+            self.example_unload_request.cleanup_behavior = self.example_unload_request.PURGE
+            somemodel.objects.exists.return_value = False
+            somemodel.deleted_objects.all.return_value = [someobject]
+
+            result = self.builder.handle_unloadmodels_request(
+                self.example_unload_request,
+                {"somemodel": somemodel, }
+            )
+
+            save_models.assert_called()
+            remove_service.assert_called()
+
+            self.assertEqual(result, self.builder.SUCCESS)
+
+    def test_handle_unloadmodels_request_softdeleted_models(self):
+        with patch.object(
+            dynamicbuild.DynamicBuilder, "save_models", wraps=self.builder.save_models
+        ) as save_models, patch.object(
+            dynamicbuild.DynamicBuilder,
+            "remove_service",
+            wraps=self.builder.remove_service,
+        ) as remove_service:
+            someobject = Mock()
+            somemodel = MagicMock()
+            somemodel.objects.all.return_value = []
+            somemodel.objects.exists.return_value = False
+            somemodel.deleted_objects.all.return_value = [someobject]
+
+            # Test with cleanup_behavior = REQUIRE_CLEAN
+
+            result = self.builder.handle_unloadmodels_request(
+                self.example_unload_request,
+                {"somemodel": somemodel, }
+            )
+
+            save_models.assert_not_called()
+            remove_service.assert_not_called()
+
+            self.assertEqual(result, self.builder.ERROR_DELETION_IN_PROGRESS)
+
     def test_handle_loadmodels_request_twice(self):
         result = self.builder.handle_loadmodels_request(self.example_request)
-        self.assertEqual(result, self.builder.SOMETHING_CHANGED)
+        self.assertEqual(result, self.builder.SUCCESS)
 
         result = self.builder.handle_loadmodels_request(self.example_request)
-        self.assertEqual(result, self.builder.NOTHING_TO_DO)
+        self.assertEqual(result, self.builder.SUCCESS_NOTHING_CHANGED)
 
     def test_save_models(self):
         manifest = self.builder.save_models(self.example_request, state="load")
diff --git a/xos/coreapi/xos_dynamicload_api.py b/xos/coreapi/xos_dynamicload_api.py
index b02af06..e153ff0 100644
--- a/xos/coreapi/xos_dynamicload_api.py
+++ b/xos/coreapi/xos_dynamicload_api.py
@@ -26,6 +26,7 @@
         self.thread_pool = thread_pool
         self.server = server
         self.django_apps = None
+        self.django_apps_by_name = {}
 
     def stop(self):
         pass
@@ -37,17 +38,33 @@
         """
         self.django_apps = django_apps
 
+        # Build up some dictionaries used by the API handlers. We can build these once at initialization time because
+        # when apps are onboarded, the core is always restarted.
+
+        self.django_apps_by_name = {}
+        self.django_app_models = {}
+        if self.django_apps:
+            for app in self.django_apps.get_app_configs():
+                self.django_apps_by_name[app.name] = app
+
+                # Build up a dictionary of all non-decl models.
+                django_models = {}
+                for (k, v) in app.models.items():
+                    if not k.endswith("_decl"):
+                        django_models[k] = v
+                self.django_app_models[app.name] = django_models
+
     @track_request_time("DynamicLoad", "LoadModels")
     def LoadModels(self, request, context):
         try:
             builder = DynamicBuilder()
             result = builder.handle_loadmodels_request(request)
 
-            if result == builder.SOMETHING_CHANGED:
+            if result == builder.SUCCESS:
                 self.server.delayed_shutdown(5)
 
             response = dynamicload_pb2.LoadModelsReply()
-            response.status = response.SUCCESS
+            response.status = result
             REQUEST_COUNT.labels(
                 "xos-core", "DynamicLoad", "LoadModels", grpc.StatusCode.OK
             ).inc()
@@ -61,17 +78,54 @@
             ).inc()
             raise e
 
+    def map_error_code(self, status, context):
+        """ Map the DynamicLoad status into an appropriate gRPC status code
+            and include an error description if appropriate.
+
+            Chameleon supports limited mapping to http status codes.
+            Picked a best-fit:
+                OK = 200
+                INVALID_ARGUMENT = 400
+                ALREADY_EXISTS = 409
+        """
+
+        code_names = {
+            DynamicBuilder.SUCCESS: "SUCCESS",
+            DynamicBuilder.SUCCESS_NOTHING_CHANGED: "SUCCESS_NOTHING_CHANGED",
+            DynamicBuilder.ERROR: "ERROR",
+            DynamicBuilder.ERROR_LIVE_MODELS: "ERROR_LIVE_MODELS",
+            DynamicBuilder.ERROR_DELETION_IN_PROGRESS: "ERROR_DELETION_IN_PROGRESS",
+            DynamicBuilder.TRYAGAIN: "TRYAGAIN"}
+
+        code_map = {
+            DynamicBuilder.SUCCESS: grpc.StatusCode.OK,
+            DynamicBuilder.SUCCESS_NOTHING_CHANGED: grpc.StatusCode.OK,
+            DynamicBuilder.ERROR: grpc.StatusCode.INVALID_ARGUMENT,
+            DynamicBuilder.ERROR_LIVE_MODELS: grpc.StatusCode.ALREADY_EXISTS,
+            DynamicBuilder.ERROR_DELETION_IN_PROGRESS: grpc.StatusCode.ALREADY_EXISTS,
+            DynamicBuilder.TRYAGAIN: grpc.StatusCode.OK}
+
+        code = code_map.get(status, DynamicBuilder.ERROR)
+
+        context.set_code(code)
+        if code != grpc.StatusCode.OK:
+            # In case of error, send helpful text back to the caller
+            context.set_details(code_names.get(status, "UNKNOWN"))
+
     @track_request_time("DynamicLoad", "UnloadModels")
     def UnloadModels(self, request, context):
         try:
             builder = DynamicBuilder()
-            result = builder.handle_unloadmodels_request(request)
+            result = builder.handle_unloadmodels_request(request,
+                                                         self.django_app_models.get("services." + request.name, []))
 
-            if result == builder.SOMETHING_CHANGED:
+            if result == builder.SUCCESS:
                 self.server.delayed_shutdown(5)
 
+            self.map_error_code(result, context)
+
             response = dynamicload_pb2.LoadModelsReply()
-            response.status = response.SUCCESS
+            response.status = result
             REQUEST_COUNT.labels(
                 "xos-core", "DynamicLoad", "UnloadModels", grpc.StatusCode.OK
             ).inc()
@@ -87,11 +141,6 @@
 
     @track_request_time("DynamicLoad", "GetLoadStatus")
     def GetLoadStatus(self, request, context):
-        django_apps_by_name = {}
-        if self.django_apps:
-            for app in self.django_apps.get_app_configs():
-                django_apps_by_name[app.name] = app
-
         try:
             builder = DynamicBuilder()
             manifests = builder.get_manifests()
@@ -106,7 +155,7 @@
                 item.state = manifest.get("state", "unspecified")
 
                 if item.state == "load":
-                    django_app = django_apps_by_name.get("services." + item.name)
+                    django_app = self.django_apps_by_name.get("services." + item.name)
                     if django_app:
                         item.state = "present"
                         # TODO: Might be useful to return a list of models as well
@@ -115,7 +164,7 @@
             item = response.services.add()
             item.name = "core"
             item.version = autodiscover_version_of_main()
-            if "core" in django_apps_by_name:
+            if "core" in self.django_apps_by_name:
                 item.state = "present"
             else:
                 item.state = "load"