diff --git a/crates/komorebi-settings/tests/reload.rs b/crates/komorebi-settings/tests/reload.rs
new file mode 100644
index 00000000..890f4019
--- /dev/null
+++ b/crates/komorebi-settings/tests/reload.rs
@@ -0,0 +1,127 @@
+//! A configuration load through a `Handle`, the way the daemons apply `apply_globals` for the groups
+//! that have moved (paddings, aspect ratio, layout defaults, display index preferences): a reload
+//! merges, a few keys reset. Section 4 of `docs/dev/settings.md`.
+
+use std::collections::HashMap;
+
+use komorebi_config::aspect_ratio::AspectRatio;
+use komorebi_config::aspect_ratio::PredefinedAspectRatio;
+use komorebi_layouts::DefaultLayout;
+use komorebi_layouts::LayoutDefaultEntry;
+use komorebi_settings::Handle;
+use komorebi_settings::Settings;
+use komorebi_settings::Shared;
+use komorebi_settings::shared::PlatformDefaults;
+use komorebi_settings::shared::SharedDelta;
+
+fn handle() -> Handle<()> {
+    Handle::new(Settings::new(
+        Shared::defaults_for(PlatformDefaults::WINDOWS),
+        (),
+    ))
+}
+
+fn load(handle: &Handle<()>, delta: SharedDelta) {
+    handle.update(|settings| delta.apply(&mut settings.shared));
+}
+
+fn entry() -> LayoutDefaultEntry {
+    LayoutDefaultEntry {
+        layout_options: None,
+        layout_options_rules: None,
+    }
+}
+
+#[test]
+fn the_first_load_without_the_keys_changes_widescreen_to_standard() {
+    let handle = handle();
+    assert_eq!(
+        handle.snapshot().shared.floating_window_aspect_ratio,
+        AspectRatio::Predefined(PredefinedAspectRatio::Widescreen)
+    );
+
+    load(&handle, SharedDelta::default());
+
+    assert_eq!(
+        handle.snapshot().shared.floating_window_aspect_ratio,
+        AspectRatio::Predefined(PredefinedAspectRatio::Standard)
+    );
+}
+
+#[test]
+fn a_reload_merges_what_the_file_gives_and_resets_what_it_resets() {
+    let handle = handle();
+
+    // load 1 gives everything
+    load(
+        &handle,
+        SharedDelta {
+            default_container_padding: Some(7),
+            default_workspace_padding: Some(8),
+            floating_window_aspect_ratio: Some(AspectRatio::Custom(3, 2)),
+            layout_defaults: Some(HashMap::from([(DefaultLayout::BSP, entry())])),
+            display_index_preferences: Some(HashMap::from([(0, String::from("a"))])),
+            ..SharedDelta::default()
+        },
+    );
+    let first = handle.snapshot();
+    assert_eq!(first.shared.defaults.container_padding, 7);
+    assert_eq!(first.shared.defaults.workspace_padding, 8);
+    assert_eq!(
+        first.shared.floating_window_aspect_ratio,
+        AspectRatio::Custom(3, 2)
+    );
+    assert_eq!(first.shared.layout_defaults.len(), 1);
+
+    // load 2 gives only a workspace padding
+    load(
+        &handle,
+        SharedDelta {
+            default_workspace_padding: Some(1),
+            ..SharedDelta::default()
+        },
+    );
+    let second = handle.snapshot();
+    // kept: container padding, display index preferences
+    assert_eq!(second.shared.defaults.container_padding, 7);
+    assert_eq!(
+        second.shared.display_index_preferences,
+        HashMap::from([(0, String::from("a"))])
+    );
+    // replaced
+    assert_eq!(second.shared.defaults.workspace_padding, 1);
+    // reset: layout defaults cleared, aspect ratio Standard
+    assert!(second.shared.layout_defaults.is_empty());
+    assert_eq!(
+        second.shared.floating_window_aspect_ratio,
+        AspectRatio::Predefined(PredefinedAspectRatio::Standard)
+    );
+
+    // a reader that held the first snapshot still sees the first load, whole
+    assert_eq!(first.shared.defaults.workspace_padding, 8);
+    assert_eq!(first.shared.layout_defaults.len(), 1);
+}
+
+#[test]
+fn a_load_never_touches_the_groups_it_does_not_name() {
+    let handle = handle();
+    handle.update(|settings| {
+        settings.shared.border.width = 42;
+        settings.shared.animation.fps = 144;
+        settings.shared.transparency.alpha = 9;
+    });
+    let before = handle.snapshot();
+
+    load(
+        &handle,
+        SharedDelta {
+            default_container_padding: Some(3),
+            ..SharedDelta::default()
+        },
+    );
+
+    let after = handle.snapshot();
+    assert_eq!(after.shared.border, before.shared.border);
+    assert_eq!(after.shared.animation, before.shared.animation);
+    assert_eq!(after.shared.transparency, before.shared.transparency);
+}