diff --git a/hermes_cli/tools_config.py b/hermes_cli/tools_config.py
index 32645aea3d..411aefcdb3 100644
--- a/hermes_cli/tools_config.py
+++ b/hermes_cli/tools_config.py
@@ -717,6 +717,7 @@ def _save_platform_tools(config: dict, platform: str, enabled_toolset_keys: Set[
     existing_toolsets = config.get("platform_toolsets", {}).get(platform, [])
     if not isinstance(existing_toolsets, list):
         existing_toolsets = []
+    existing_toolsets = [str(ts) for ts in existing_toolsets]
 
     # Preserve any entries that are NOT configurable toolsets and NOT platform
     # defaults (i.e. only MCP server names should be preserved)
@@ -724,6 +725,11 @@ def _save_platform_tools(config: dict, platform: str, enabled_toolset_keys: Set[
         entry for entry in existing_toolsets
         if entry not in configurable_keys and entry not in platform_default_keys
     }
+    # Opening `hermes tools` is the user's opt-in to reconfigure tools, so treat
+    # saving from the picker as consent to clear the "no_mcp" sentinel. The
+    # picker has no checkbox for no_mcp, so without this users who once set it
+    # by hand could never re-enable MCP servers through the UI.
+    preserved_entries.discard("no_mcp")
 
     # Merge preserved entries with new enabled toolsets
     config["platform_toolsets"][platform] = sorted(enabled_toolset_keys | preserved_entries)
diff --git a/tests/hermes_cli/test_tools_config.py b/tests/hermes_cli/test_tools_config.py
index b134fc98b3..bf57ebb60b 100644
--- a/tests/hermes_cli/test_tools_config.py
+++ b/tests/hermes_cli/test_tools_config.py
@@ -601,3 +601,57 @@ class TestImagegenModelPicker:
             _configure_imagegen_model("fal", config)
         assert isinstance(config["image_gen"], dict)
         assert config["image_gen"]["model"] == "fal-ai/flux-2/klein/9b"
+
+
+def test_save_platform_tools_normalizes_numeric_entries():
+    """YAML may parse bare numeric toolset names as int. They should be
+    normalized to str so they survive the save round-trip.
+    """
+    config = {
+        "platform_toolsets": {
+            "cli": ["web", "terminal", 12306, "custom-mcp"]
+        }
+    }
+
+    with patch("hermes_cli.tools_config.save_config"):
+        _save_platform_tools(config, "cli", {"web", "browser"})
+
+    saved = config["platform_toolsets"]["cli"]
+    assert "12306" in saved
+    assert 12306 not in saved
+
+
+def test_save_platform_tools_clears_no_mcp_sentinel():
+    """`hermes tools` has no UI for no_mcp, so saving from the picker clears
+    the sentinel unconditionally — otherwise a user who once set no_mcp by
+    hand could never re-enable MCP servers through the UI.
+    """
+    config = {
+        "platform_toolsets": {
+            "cli": ["web", "terminal", "no_mcp"]
+        }
+    }
+
+    with patch("hermes_cli.tools_config.save_config"):
+        _save_platform_tools(config, "cli", {"web", "browser"})
+
+    saved = config["platform_toolsets"]["cli"]
+    assert "no_mcp" not in saved
+
+
+def test_save_platform_tools_preserves_mcp_server_names():
+    """Non-sentinel passthrough entries (MCP server names) must still survive
+    the save — we only clear `no_mcp`, not every non-configurable entry.
+    """
+    config = {
+        "platform_toolsets": {
+            "cli": ["web", "terminal", "custom-mcp", "another-mcp"]
+        }
+    }
+
+    with patch("hermes_cli.tools_config.save_config"):
+        _save_platform_tools(config, "cli", {"web", "browser"})
+
+    saved = config["platform_toolsets"]["cli"]
+    assert "custom-mcp" in saved
+    assert "another-mcp" in saved