diff --git a/crates/engine/src/settings/prefs/sections.rs b/crates/engine/src/settings/prefs/sections.rs
index 328f93bf4..9a9f4ab21 100644
--- a/crates/engine/src/settings/prefs/sections.rs
+++ b/crates/engine/src/settings/prefs/sections.rs
@@ -93,7 +93,7 @@ page!(Previews {
     /// Largest downsampling while playing back: `1/2`, `1/4`, `1/8`.
     adaptive_resolution_limit: String = "1/8".into(),
     show_internal_wireframes: bool = false,
-    cache_frames_when_idle: bool = false,
+    cache_frames_when_idle: bool = true,
     fast_previews: bool = false,
     /// `faster` or `moreAccurate`.
     zoom_quality: String = "moreAccurate".into(),
diff --git a/crates/ui-egui/src/state.rs b/crates/ui-egui/src/state.rs
index 612aa0a10..635b46acd 100644
--- a/crates/ui-egui/src/state.rs
+++ b/crates/ui-egui/src/state.rs
@@ -806,7 +806,7 @@ impl Default for UiState {
             home_learn: false,
             home_templates: false,
             align_to_selection: false,
-            cache_when_idle: false,
+            cache_when_idle: true,
             tracker_source: None,
             layer_panel: None,
             layer_view: None,
diff --git a/crates/ui-egui/tests/it/ui_comp_presets.rs b/crates/ui-egui/tests/it/ui_comp_presets.rs
index 3fda8a8cc..93cd02030 100644
--- a/crates/ui-egui/tests/it/ui_comp_presets.rs
+++ b/crates/ui-egui/tests/it/ui_comp_presets.rs
@@ -174,6 +174,8 @@ fn composition_settings_view_stays_put_when_it_scrolls() {
 #[test]
 fn composition_settings_refits_when_the_language_changes() {
     let mut s = Session::default();
+    // Idle caching keeps repainting while it renders; this test waits for repaints to stop.
+    s.prefs.previews.cache_frames_when_idle = false;
     s.execute("comp.new", json!({"name": "Edit", "width": 2560, "height": 1440, "frameRate": 60, "duration": 4})).unwrap();
     let mut h = Harness::builder()
         .with_size(egui::vec2(1600.0, 1000.0))
diff --git a/crates/ui-egui/tests/it/ui_preview_align.rs b/crates/ui-egui/tests/it/ui_preview_align.rs
index 1469a5e9e..622df0397 100644
--- a/crates/ui-egui/tests/it/ui_preview_align.rs
+++ b/crates/ui-egui/tests/it/ui_preview_align.rs
@@ -238,8 +238,9 @@ fn cache_frames_when_idle_fills_the_work_area() {
     let mut h = harness();
     let cid = h.state().session.active_comp_id().unwrap();
     let cached = |h: &Harness<'_, EffectcraftApp>| h.state().frames.cached_frames(&h.state().shown_series(cid)).len();
-    // Off: only a few frames ahead of the current time are prefetched (the work area is the
-    // whole 240 frames).
+    // Off (it is on by default): only a few frames ahead of the current time are prefetched (the
+    // work area is the whole 240 frames).
+    invoke(&mut h, "playback.cacheWhenIdle", json!({"value": false}));
     for _ in 0..120 {
         h.step();
         std::thread::sleep(std::time::Duration::from_millis(2));
diff --git a/docs/preferences.md b/docs/preferences.md
index 927b66788..de7e426bc 100644
--- a/docs/preferences.md
+++ b/docs/preferences.md
@@ -55,7 +55,8 @@ Commands (CLI, MCP, control channel):
   Adaptive Resolution drops to while you drag; a playing preview keeps the viewer's resolution)
 - `previews.cacheFramesWhenIdle`: Cache Frames When Idle (Composition ▸ Preview): after a second
   without input or edits, the viewer renders the work area into the RAM preview in the
-  background, from the current time on, until it is cached or the budget is full
+  background, from the current time on, until it is cached or the budget is full. On by default,
+  as in After Effects, so the first playback of a comp left alone for a second is already cached
 - `previews.fastPreviews`: Fast Previews (Draft 3D, Faster Effects)
 - `appearance.appearanceMode`: Appearance Mode (`auto` / `dark` / `light`). `auto` (Sync with System) follows the operating system's light or dark appearance while the app runs: on Linux the desktop app reads the XDG desktop portal (`org.freedesktop.appearance` `color-scheme`) once and then listens for its `SettingChanged` signal on a worker thread, repainting only when the value changes (nothing polls); `gsettings` runs at most once at start-up, by absolute path, when the portal gives no answer. Elsewhere it uses what the window system reports. With no answer it shows the dark theme. New installs stay `dark`; Sync with System is opt-in. The Tools bar's appearance button (a monitor, sun or moon) cycles Sync with System, Light and Dark (`view.theme.toggle`, Next Appearance Mode).
 - `appearance.darkTheme`: Dark Theme (`dark` / `darker`), shown in dark appearance