diff --git a/bot_bottle/backend/egress_apply.py b/bot_bottle/backend/egress_apply.py
index 9cf8200..ed54cdf 100644
--- a/bot_bottle/backend/egress_apply.py
+++ b/bot_bottle/backend/egress_apply.py
@@ -11,7 +11,7 @@ from pathlib import Path
 
 from ..bottle_state import egress_state_dir
 from ..egress import EGRESS_ROUTES_FILENAME
-from ..egress_addon_core import load_routes
+from ..egress_addon_core import LOG_OFF, load_config
 
 
 class EgressApplyError(RuntimeError):
@@ -33,11 +33,15 @@ class EgressApplicator(ABC):
     @staticmethod
     def validate_routes_content(content: str) -> None:
         try:
-            load_routes(content)
+            config = load_config(content)
         except ValueError as e:
             raise EgressApplyError(
                 f"proposed routes.yaml is not valid: {e}"
             ) from e
+        if config.log != LOG_OFF:
+            raise EgressApplyError(
+                "proposed routes.yaml must not change egress logging"
+            )
 
     @staticmethod
     def _routes_path(slug: str) -> Path:
diff --git a/bot_bottle/supervise_server.py b/bot_bottle/supervise_server.py
index 3e9ba1c..b6bed85 100644
--- a/bot_bottle/supervise_server.py
+++ b/bot_bottle/supervise_server.py
@@ -47,11 +47,11 @@ from pathlib import Path
 try:
     # Same-directory imports inside the bundle container; these files are
     # COPYed flat under /app by Dockerfile.sidecars.
-    from egress_addon_core import load_routes
+    from egress_addon_core import LOG_OFF, load_config
     import supervise as _sv
 except ModuleNotFoundError:
     # Package imports for host-side tests and tooling.
-    from .egress_addon_core import load_routes
+    from .egress_addon_core import LOG_OFF, load_config
     from . import supervise as _sv
 
 
@@ -297,12 +297,17 @@ def validate_proposed_file(tool: str, content: str) -> None:
         pass
     elif tool in (_sv.TOOL_EGRESS_ALLOW, _sv.TOOL_EGRESS_BLOCK):
         try:
-            load_routes(content)
+            config = load_config(content)
         except ValueError as e:
             raise _RpcError(
                 ERR_INVALID_PARAMS,
                 f"{tool}: proposed routes.yaml is not valid: {e}",
             ) from e
+        if config.log != LOG_OFF:
+            raise _RpcError(
+                ERR_INVALID_PARAMS,
+                f"{tool}: proposed routes.yaml must not change egress logging",
+            )
     else:
         raise _RpcError(ERR_INVALID_PARAMS, f"unknown tool {tool!r}")
 
diff --git a/tests/unit/test_egress_apply.py b/tests/unit/test_egress_apply.py
index 2966f05..de51c57 100644
--- a/tests/unit/test_egress_apply.py
+++ b/tests/unit/test_egress_apply.py
@@ -54,6 +54,15 @@ class TestValidateRoutesContent(unittest.TestCase):
                 '    auth_scheme: "Bearer"\n'
             )
 
+    def test_rejects_log_full(self):
+        with self.assertRaises(EgressApplyError) as cm:
+            applicator.validate_routes_content(
+                'log: 2\n'
+                'routes:\n'
+                '  - host: "x.example"\n'
+            )
+        self.assertIn("must not change egress logging", str(cm.exception))
+
 
 class TestApplyRoutesChange(unittest.TestCase):
     def setUp(self):
diff --git a/tests/unit/test_supervise_server.py b/tests/unit/test_supervise_server.py
index 0535076..c18d6a5 100644
--- a/tests/unit/test_supervise_server.py
+++ b/tests/unit/test_supervise_server.py
@@ -67,6 +67,15 @@ class TestValidation(unittest.TestCase):
         with self.assertRaises(_RpcError):
             validate_proposed_file(_sv.TOOL_EGRESS_BLOCK, "routes: nope\n")
 
+    def test_egress_routes_yaml_rejects_log_full(self):
+        with self.assertRaises(_RpcError) as cm:
+            validate_proposed_file(
+                _sv.TOOL_EGRESS_ALLOW,
+                "log: 2\nroutes:\n  - host: example.com\n",
+            )
+        self.assertEqual(ERR_INVALID_PARAMS, cm.exception.code)
+        self.assertIn("must not change egress logging", cm.exception.message)
+
 
 # --- JSON-RPC parsing ------------------------------------------------------