diff --git a/gateway/display_config.py b/gateway/display_config.py
index 76466d521525..e58e6e82b22d 100644
--- a/gateway/display_config.py
+++ b/gateway/display_config.py
@@ -140,7 +140,12 @@ _PLATFORM_DEFAULTS: dict[str, dict[str, Any]] = {
     # Tier 2 — edit support, often customer/workspace channels
     # Slack: tool_progress off by default — Bolt posts cannot be edited like CLI;
     # "new"/"all" spam permanent lines in channels (hermes-agent#14663).
-    "slack":           {**_TIER_MEDIUM, "tool_progress": "off"},
+    "slack":           {
+        **_TIER_MEDIUM,
+        "tool_progress": "off",
+        "long_running_notifications": False,
+        "busy_ack_detail": False,
+    },
     "mattermost":      _TIER_MEDIUM,
     "matrix":          _TIER_MEDIUM,
     "feishu":          _TIER_MEDIUM,
diff --git a/tests/gateway/test_display_config.py b/tests/gateway/test_display_config.py
index c45705bc4ab0..4d11f22db96c 100644
--- a/tests/gateway/test_display_config.py
+++ b/tests/gateway/test_display_config.py
@@ -328,6 +328,14 @@ class TestPlatformDefaults:
         assert resolve_display_setting({}, "discord", "long_running_notifications") is True
         assert resolve_display_setting({}, "discord", "busy_ack_detail") is True
 
+    def test_slack_workspace_chatter_defaults(self):
+        """Slack should not leave permanent heartbeat/debug breadcrumbs in channels."""
+        from gateway.display_config import resolve_display_setting
+
+        assert resolve_display_setting({}, "slack", "tool_progress") == "off"
+        assert resolve_display_setting({}, "slack", "long_running_notifications") is False
+        assert resolve_display_setting({}, "slack", "busy_ack_detail") is False
+
     def test_telegram_mobile_chatter_can_opt_in(self):
         """Per-platform config can re-enable Telegram busy-ack detail
         and re-disable the kept-on defaults."""
diff --git a/tests/gateway/test_restart_notification.py b/tests/gateway/test_restart_notification.py
index b090503c5b13..e110eb876e02 100644
--- a/tests/gateway/test_restart_notification.py
+++ b/tests/gateway/test_restart_notification.py
@@ -665,6 +665,27 @@ async def test_shutdown_notifications_use_cached_live_thread_source_when_origin_
     )
 
 
+@pytest.mark.asyncio
+async def test_shutdown_notifications_are_fully_muted_when_flag_disabled():
+    runner, adapter = make_restart_runner()
+    source = make_restart_source(chat_id="active-42", chat_type="group", thread_id="topic-7")
+    session_key = build_session_key(source)
+
+    runner.config.platforms[Platform.TELEGRAM].gateway_restart_notification = False
+    runner.config.platforms[Platform.TELEGRAM].home_channel = HomeChannel(
+        platform=Platform.TELEGRAM,
+        chat_id="home-42",
+        name="Ops Home",
+    )
+    runner._running_agents[session_key] = object()
+    runner.session_store._entries[session_key] = MagicMock(origin=source)
+    adapter.send = AsyncMock()
+
+    await runner._notify_active_sessions_of_shutdown()
+
+    adapter.send.assert_not_awaited()
+
+
 @pytest.mark.asyncio
 async def test_restart_shutdown_notification_anchors_telegram_dm_topic():
     runner, adapter = make_restart_runner()