diff --git a/crates/ui-egui/src/workspace_state.rs b/crates/ui-egui/src/workspace_state.rs
index 92e41fde5..4807e4e40 100644
--- a/crates/ui-egui/src/workspace_state.rs
+++ b/crates/ui-egui/src/workspace_state.rs
@@ -202,350 +202,4 @@ impl WorkspaceStore {
 }
 
 #[cfg(test)]
-mod tests {
-    use super::*;
-    use crate::dock::{Floating, Layout, Node, StackEntry, WorkspaceExt as _};
-    use craft_ui::docking::Action;
-    use craft_ui::layout::{SplitAxis, SplitSize};
-    use effectcraft_engine::config::MemoryConfig;
-
-    fn minimal() -> Workspace {
-        Workspace::new(crate::dock::workspace("Minimal"))
-    }
-
-    fn tabs(panels: &[PanelKind]) -> Node<PanelKind> {
-        Node::Tabs { panels: panels.to_vec(), active: 0 }
-    }
-
-    #[test]
-    fn corrupt_future_or_unknown_workspace_keeps_defaults_and_original_file() {
-        let valid = Snapshot::capture(&UiState::default());
-        // Damaged files of the earlier version: a panel in two places, a bad split, an unknown
-        // panel, a tree deeper than craft-ui allows, a missing field.
-        let earlier = |dock: &str| {
-            format!(
-                r#"{{"version":1,"workspace":"Default","dock":{dock},"floating":[],"focused":"Composition","maximized":null,"saved_workspaces":{{}},"saved_floating":{{}}}}"#
-            )
-        };
-        let mut deep = r#"{"Tabs":{"panels":["Composition"],"active":0}}"#.to_string();
-        for _ in 0..=craft_ui::docking::MAX_DEPTH {
-            deep = format!(r#"{{"Split":{{"vertical":true,"size":{{"Ratio":0.5}},"a":{deep},"b":{{"Tabs":{{"panels":[],"active":0}}}}}}}}"#);
-        }
-        let twice =
-            r#"{"Split":{"vertical":true,"size":{"Ratio":0.5},"a":{"Tabs":{"panels":["Project"],"active":0}},"b":{"Tabs":{"panels":["Project"],"active":0}}}}"#;
-        let bad_split = r#"{"Split":{"vertical":true,"size":{"Ratio":7.0},"a":{"Tabs":{"panels":["Project"],"active":0}},"b":{"Tabs":{"panels":["Timeline"],"active":0}}}}"#;
-        for text in [
-            "{".into(),
-            "{}".into(),
-            "[1, 2]".into(),
-            serde_json::to_string(&Snapshot { version: VERSION + 1, ..valid }).unwrap(),
-            " ".repeat(MAX_BYTES + 1),
-            earlier(twice),
-            earlier(bad_split),
-            earlier(r#"{"Tabs":{"panels":["NoSuchPanel"],"active":0}}"#),
-            earlier(&deep),
-            r#"{"version":1,"workspace":"Default"}"#.into(),
-            r#"{"workspaces":{"Mine":{"Tabs":{"panels":["Composition"],"active":3}}}}"#.into(),
-        ] {
-            let config = MemoryConfig::default();
-            config.write(FILE, &text).unwrap();
-            let mut ui = UiState::default();
-            let mut store = WorkspaceStore::load(Some(&config), &mut ui);
-            assert!(store.error.is_some());
-            assert_eq!(ui.workspace, "Default");
-            assert_eq!(ui.dock, UiState::default().dock);
-            ui.focused = PanelKind::Project;
-            ui.dock = minimal();
-            assert!(!store.save(Some(&config), &ui).unwrap());
-            assert!(store.save_now(Some(&config), &ui).unwrap_err().contains("couldn't be loaded"));
-            assert_eq!(config.read(FILE).as_deref(), Some(text.as_str()));
-            assert_eq!(config.read(BACKUP), None);
-        }
-    }
-
-    /// A file written by EffectCraft 0.10 (craft-libs 5c874d51): the Default workspace with
-    /// Preview floating, Render Queue floating in its own native window, Align closed,
-    /// Effects & Presets moved into the Project group and Audio split beside the Timeline,
-    /// saved as "My Layout"; then Layer closed.
-    const V1: &str = include_str!("../tests/fixtures/workspaces-v1.json");
-
-    #[test]
-    fn version_one_file_loads_with_every_panel_in_place() {
-        let config = MemoryConfig::default();
-        config.write(FILE, V1).unwrap();
-        let mut ui = UiState::default();
-        let store = WorkspaceStore::load(Some(&config), &mut ui);
-        assert_eq!(store.error, None);
-        assert_eq!(ui.workspace, "My Layout");
-        assert_eq!(ui.focused, PanelKind::Composition);
-        use PanelKind::*;
-        let root = crate::dock::hsplit(
-            SplitSize::FixedSecond(300.0),
-            crate::dock::vsplit(
-                SplitSize::Ratio(0.56),
-                crate::dock::hsplit(SplitSize::FixedFirst(300.0), crate::dock::tabs(&[Project, EffectControls, EffectsPresets], 2), tabs(&[Composition])),
-                crate::dock::hsplit(SplitSize::Ratio(0.5), tabs(&[Timeline]), tabs(&[Audio])),
-            ),
-            tabs(&[Properties]),
-        );
-        assert_eq!(ui.dock.layout.root, Some(root));
-        let floating: Vec<_> = ui.dock.layout.floating.iter().map(|w| (w.panels().copied().collect::<Vec<_>>(), w.rect, w.native)).collect();
-        assert_eq!(
-            floating,
-            [
-                (vec![Preview], [900.0, 120.0, 300.0, 260.0], None),
-                (vec![RenderQueue], [200.0, 500.0, 520.0, 240.0], Some(crate::dock_ui::sanitized_window_rect([200.0, 500.0, 520.0, 240.0]))),
-            ]
-        );
-        // Closed panels stay closed.
-        for panel in [Align, Layer] {
-            assert!(!ui.dock.is_open(panel), "{panel:?}");
-        }
-        // The native window's place is its outer position until the main window reports its
-        // frame (here a 28-point title bar); the file is not rewritten before.
-        let id = ui.dock.layout.floating[1].id;
-        assert_eq!(ui.native_outer, [id]);
-        let mut store = store;
-        assert!(!store.save(Some(&config), &ui).unwrap());
-        let outer = egui::Rect::from_min_size(egui::pos2(10.0, 20.0), egui::vec2(1600.0, 1000.0));
-        crate::dock_ui::native_outer_to_content(&mut ui, Some(outer), Some(outer.translate(egui::vec2(0.0, 28.0))), 0.1);
-        assert_eq!(ui.dock.layout.floating[1].native, Some([200.0, 528.0, 520.0, 240.0]));
-        assert!(ui.native_outer.is_empty());
-        assert!(store.save(Some(&config), &ui).unwrap());
-        // The named workspace still has Layer, closed only after it was saved.
-        let saved = ui.saved_workspaces.get("My Layout").unwrap();
-        assert!(saved.is_docked(Layer) && saved.is_floating(Preview) && !saved.is_open(Align));
-        assert_eq!(saved.layout.floating.iter().filter_map(|w| w.native).count(), 0);
-    }
-
-    #[test]
-    fn version_one_file_is_rewritten_once_in_the_current_format_and_kept_as_a_backup() {
-        let config = MemoryConfig::default();
-        config.write(FILE, V1).unwrap();
-        let mut ui = UiState::default();
-        let mut store = WorkspaceStore::load(Some(&config), &mut ui);
-        // A backend that reports no window positions: the native place stays as it was.
-        let native = ui.dock.layout.floating[1].native;
-        crate::dock_ui::native_outer_to_content(&mut ui, None, None, 1.0);
-        assert!(!ui.native_outer.is_empty(), "waits for a report");
-        crate::dock_ui::native_outer_to_content(&mut ui, None, None, 5.0);
-        assert!(ui.native_outer.is_empty());
-        assert_eq!(ui.dock.layout.floating[1].native, native);
-        let migrated = Snapshot::capture(&ui);
-        assert!(store.has_changes(&ui), "the migrated layout is written without waiting for an edit");
-        assert!(store.save(Some(&config), &ui).unwrap());
-        assert_eq!(config.read(BACKUP).as_deref(), Some(V1));
-        let text = config.read(FILE).unwrap();
-        assert_eq!(serde_json::from_str::<serde_json::Value>(&text).unwrap()["version"], VERSION);
-        assert!(!store.has_changes(&ui));
-        let mut restored = UiState::default();
-        let reloaded = WorkspaceStore::load(Some(&config), &mut restored);
-        assert_eq!(reloaded.error, None);
-        assert!(!reloaded.has_changes(&restored));
-        assert_eq!(Snapshot::capture(&restored), migrated);
-    }
-
-    #[test]
-    fn stacked_frames_with_tabs_and_an_empty_root_migrate() {
-        let text = r#"{"version":1,"workspace":"Mine","dock":{"Tabs":{"panels":[],"active":0}},
-            "floating":[{"panels":["Project"],"active":0,"rect":[10.0,10.0,300.0,200.0]}],
-            "focused":"Project","maximized":null,
-            "saved_workspaces":{"Mine":{"Stack":{"entries":[{"panel":"Info","open":true},{"panels":["Audio","Preview"],"active":1,"open":true,"height":80.0}]}},
-                "Column":{"Stack":{"entries":[{"panel":"Align","open":false},{"panel":"Preview","open":true,"height":46.0},{"panels":["Properties","Paint"],"active":1,"open":false,"height":300.0},{"panel":"Info","open":true}]}}},
-            "saved_floating":{"Gone":[{"panels":["Align"],"active":0,"rect":[0.0,0.0,100.0,100.0]}]}}"#;
-        let config = MemoryConfig::default();
-        config.write(FILE, text).unwrap();
-        let mut ui = UiState::default();
-        let store = WorkspaceStore::load(Some(&config), &mut ui);
-        assert_eq!(store.error, None);
-        assert_eq!(ui.dock.layout.root, None);
-        assert!(ui.dock.is_floating(PanelKind::Project));
-        use PanelKind::*;
-        // Each open frame is a tab group with all its tabs; a frame's height is a fixed size
-        // (with its tab strip), and the frame without one takes the rest.
-        let column = crate::dock::vsplit(SplitSize::FixedSecond(80.0 + crate::dock::TAB_STRIP), tabs(&[Info]), crate::dock::tabs(&[Audio, Preview], 1));
-        assert_eq!(ui.saved_workspaces.get("Mine").and_then(|w| w.layout.root.clone()), Some(column));
-        // Closed frames' tabs join the open frame above them, or below at the top.
-        let column = crate::dock::vsplit(SplitSize::FixedFirst(46.0 + crate::dock::TAB_STRIP), tabs(&[Preview, Properties, Paint, Align]), tabs(&[Info]));
-        assert_eq!(ui.saved_workspaces.get("Column").and_then(|w| w.layout.root.clone()), Some(column));
-        assert_eq!(ui.saved_workspaces.len(), 2, "floating groups of no named workspace are dropped");
-    }
-
-    #[test]
-    fn explicit_save_without_a_settings_folder_is_an_error() {
-        let mut ui = UiState::default();
-        let mut store = WorkspaceStore::load(None, &mut ui);
-        ui.focused = PanelKind::Project;
-        assert!(!store.save(None, &ui).unwrap());
-        assert!(store.save_now(None, &ui).is_err());
-    }
-
-    #[test]
-    fn explicit_save_with_nothing_new_succeeds() {
-        let config = MemoryConfig::default();
-        let mut ui = UiState::default();
-        let mut store = WorkspaceStore::load(Some(&config), &mut ui);
-        ui.focused = PanelKind::Project;
-        store.save_now(Some(&config), &ui).unwrap();
-        store.save_now(Some(&config), &ui).unwrap();
-        assert!(config.read(FILE).is_some());
-    }
-
-    #[test]
-    fn invalid_tabs_split_and_deep_tree_are_rejected() {
-        let mut snapshot = Snapshot::capture(&UiState::default());
-        snapshot.dock = Workspace::new(Layout { root: Some(Node::Tabs { panels: vec![PanelKind::Project], active: usize::MAX }), floating: vec![] });
-        assert!(snapshot.validate().is_err());
-        let split = |size, first, second| Node::Split { axis: SplitAxis::Horizontal, size, first: Box::new(first), second: Box::new(second) };
-        snapshot.dock = Workspace::new(Layout {
-            root: Some(split(SplitSize::FixedFirst(f32::NAN), tabs(&[PanelKind::Project]), tabs(&[PanelKind::Timeline]))),
-            floating: vec![],
-        });
-        assert!(snapshot.validate().is_err());
-        let mut root = tabs(&[PanelKind::Composition]);
-        for _ in 0..=craft_ui::docking::MAX_DEPTH {
-            root = split(SplitSize::Ratio(0.5), root, tabs(&[]));
-        }
-        snapshot.dock = Workspace::new(Layout { root: Some(root), floating: vec![] });
-        assert!(snapshot.validate().is_err());
-        // A panel in two places.
-        snapshot.dock = Workspace::new(Layout {
-            root: Some(tabs(&[PanelKind::Project])),
-            floating: vec![Floating::single(vec![PanelKind::Project], 0, [0.0, 0.0, 200.0, 100.0])],
-        });
-        assert!(snapshot.validate().is_err());
-    }
-
-    #[test]
-    fn closing_all_docked_panels_remains_a_persistable_layout() {
-        let config = MemoryConfig::default();
-        let mut ui = UiState::default();
-        let mut store = WorkspaceStore::load(Some(&config), &mut ui);
-        for panel in ui.dock.panels() {
-            ui.dock.apply(Action::Close { panel }, crate::dock::permissions).unwrap();
-        }
-        assert!(ui.dock.layout.root.is_none());
-        assert!(store.save(Some(&config), &ui).unwrap());
-        let mut restored = UiState::default();
-        let loaded = WorkspaceStore::load(Some(&config), &mut restored);
-        assert!(loaded.error.is_none());
-        assert_eq!(restored.dock, ui.dock);
-    }
-
-    #[test]
-    fn floating_groups_and_named_snapshots_roundtrip_without_document_state() {
-        let config = MemoryConfig::default();
-        let mut ui = UiState::default();
-        let mut store = WorkspaceStore::load(Some(&config), &mut ui);
-        ui.workspace = "Floating".into();
-        ui.dock.apply(Action::Float { panel: PanelKind::Preview, rect: [50.0, 80.0, 200.0, 160.0] }, crate::dock::permissions).unwrap();
-        ui.dock.apply(Action::Close { panel: PanelKind::Align }, crate::dock::permissions).unwrap();
-        ui.saved_workspaces.insert(ui.workspace.clone(), ui.dock.clone());
-        ui.maximized = Some(PanelKind::Composition);
-        ui.project_search = "do not persist".into();
-        assert!(store.save(Some(&config), &ui).unwrap());
-        let mut restored = UiState::default();
-        WorkspaceStore::load(Some(&config), &mut restored);
-        assert_eq!(Snapshot::capture(&restored), Snapshot::capture(&ui));
-        // The closed panel's place comes back with it.
-        assert!(restored.dock.hidden.iter().any(|(p, _)| *p == PanelKind::Align));
-        assert!(restored.project_search.is_empty());
-    }
-
-    #[test]
-    fn restored_viewer_slots_do_not_reuse_ids_or_restore_document_links() {
-        let config = MemoryConfig::default();
-        let mut ui = UiState::default();
-        let mut store = WorkspaceStore::load(Some(&config), &mut ui);
-        let two = |viewer| Workspace::new(Layout { root: Some(tabs(&[PanelKind::Composition, PanelKind::Viewer(viewer)])), floating: vec![] });
-        ui.dock = two(2);
-        ui.saved_workspaces.insert("Two views".into(), two(5));
-        ui.viewers.insert(2, Some(42));
-        assert!(store.save(Some(&config), &ui).unwrap());
-        let mut app = crate::EffectcraftApp::new(effectcraft_engine::Session::default());
-        WorkspaceStore::load(Some(&config), &mut app.ui);
-        assert_eq!(app.ui.viewers.get(&2), Some(&None));
-        assert_eq!(app.ui.viewers.get(&5), Some(&None));
-        assert_eq!(crate::panels::viewers::new_viewer(&mut app), 6);
-        assert!(app.ui.dock.is_docked(PanelKind::Viewer(2)));
-    }
-
-    #[test]
-    fn invalid_viewer_ids_are_rejected_in_every_workspace_reference() {
-        for id in [0, MAX_VIEWER_ID + 1, u32::MAX] {
-            for location in 0..8 {
-                let mut snapshot = Snapshot::capture(&UiState::default());
-                let panel = PanelKind::Viewer(id);
-                let docked = Workspace::new(Layout { root: Some(tabs(&[panel])), floating: vec![] });
-                let stacked =
-                    Workspace::new(Layout { root: Some(Node::Stack { entries: vec![StackEntry { panel, open: true, height: None }] }), floating: vec![] });
-                let floating = Workspace::new(Layout {
-                    root: Some(tabs(&[PanelKind::Composition])),
-                    floating: vec![Floating::single(vec![panel], 0, [0.0, 0.0, 200.0, 100.0])],
-                });
-                let mut hidden = Workspace::new(Layout { root: Some(tabs(&[PanelKind::Composition, panel])), floating: vec![] });
-                hidden.apply(Action::Close { panel }, crate::dock::permissions).unwrap();
-                match location {
-                    0 => snapshot.focused = panel,
-                    1 => snapshot.maximized = Some(panel),
-                    2 => snapshot.dock = docked,
-                    3 => snapshot.dock = stacked,
-                    4 => snapshot.dock = floating,
-                    5 => snapshot.dock = hidden,
-                    6 => {
-                        snapshot.saved_workspaces.insert("Saved".into(), stacked);
-                    }
-                    _ => {
-                        snapshot.saved_workspaces.insert("Saved".into(), floating);
-                    }
-                }
-                assert!(snapshot.validate().is_err(), "viewer {id} at location {location} must be rejected");
-            }
-        }
-    }
-
-    #[test]
-    fn hostile_native_window_places_are_made_safe_on_load() {
-        let config = MemoryConfig::default();
-        let mut ui = UiState::default();
-        let mut store = WorkspaceStore::load(Some(&config), &mut ui);
-        ui.dock.apply(Action::Float { panel: PanelKind::Project, rect: [10.0, 10.0, 300.0, 200.0] }, crate::dock::permissions).unwrap();
-        ui.dock.apply(Action::SetNative { panel: PanelKind::Project, rect: Some([90_000.0, -90_000.0, 1.0e5, 0.5]) }, crate::dock::permissions).unwrap();
-        assert!(store.save(Some(&config), &ui).unwrap());
-        let mut restored = UiState::default();
-        WorkspaceStore::load(Some(&config), &mut restored);
-        let native = restored.dock.layout.floating.iter().find(|w| w.contains(&PanelKind::Project)).and_then(|w| w.native).unwrap();
-        assert_eq!(native, crate::dock_ui::sanitized_window_rect(native));
-        assert!(native[2] <= crate::dock_ui::PANEL_WINDOW_MAX && native[3] >= crate::dock_ui::PANEL_WINDOW_MIN[1]);
-    }
-
-    #[test]
-    fn failed_write_keeps_previous_snapshot_and_retries() {
-        struct Fails<'a>(&'a MemoryConfig);
-        impl ConfigStore for Fails<'_> {
-            fn read(&self, name: &str) -> Option<String> {
-                self.0.read(name)
-            }
-            fn write(&self, _name: &str, _data: &str) -> std::io::Result<()> {
-                Err(std::io::Error::other("synthetic full disk"))
-            }
-            fn remove(&self, _name: &str) -> std::io::Result<()> {
-                Err(std::io::Error::other("unused"))
-            }
-        }
-        let config = MemoryConfig::default();
-        let mut ui = UiState::default();
-        let mut store = WorkspaceStore::load(Some(&config), &mut ui);
-        ui.focused = PanelKind::Project;
-        assert!(store.save(Some(&config), &ui).unwrap());
-        let previous = config.read(FILE).unwrap();
-        ui.focused = PanelKind::Timeline;
-        assert!(store.save(Some(&Fails(&config)), &ui).unwrap_err().contains("synthetic full disk"));
-        assert_eq!(config.read(FILE).as_deref(), Some(previous.as_str()));
-        assert!(store.has_changes(&ui));
-        assert!(store.save(Some(&config), &ui).unwrap());
-        let mut restored = UiState::default();
-        WorkspaceStore::load(Some(&config), &mut restored);
-        assert_eq!(restored.focused, PanelKind::Timeline);
-    }
-}
+mod tests;
diff --git a/crates/ui-egui/src/workspace_state/tests.rs b/crates/ui-egui/src/workspace_state/tests.rs
new file mode 100644
index 000000000..9fbfeea64
--- /dev/null
+++ b/crates/ui-egui/src/workspace_state/tests.rs
@@ -0,0 +1,345 @@
+use super::*;
+use crate::dock::{Floating, Layout, Node, StackEntry, WorkspaceExt as _};
+use craft_ui::docking::Action;
+use craft_ui::layout::{SplitAxis, SplitSize};
+use effectcraft_engine::config::MemoryConfig;
+
+fn minimal() -> Workspace {
+    Workspace::new(crate::dock::workspace("Minimal"))
+}
+
+fn tabs(panels: &[PanelKind]) -> Node<PanelKind> {
+    Node::Tabs { panels: panels.to_vec(), active: 0 }
+}
+
+#[test]
+fn corrupt_future_or_unknown_workspace_keeps_defaults_and_original_file() {
+    let valid = Snapshot::capture(&UiState::default());
+    // Damaged files of the earlier version: a panel in two places, a bad split, an unknown
+    // panel, a tree deeper than craft-ui allows, a missing field.
+    let earlier = |dock: &str| {
+        format!(
+            r#"{{"version":1,"workspace":"Default","dock":{dock},"floating":[],"focused":"Composition","maximized":null,"saved_workspaces":{{}},"saved_floating":{{}}}}"#
+        )
+    };
+    let mut deep = r#"{"Tabs":{"panels":["Composition"],"active":0}}"#.to_string();
+    for _ in 0..=craft_ui::docking::MAX_DEPTH {
+        deep = format!(r#"{{"Split":{{"vertical":true,"size":{{"Ratio":0.5}},"a":{deep},"b":{{"Tabs":{{"panels":[],"active":0}}}}}}}}"#);
+    }
+    let twice =
+        r#"{"Split":{"vertical":true,"size":{"Ratio":0.5},"a":{"Tabs":{"panels":["Project"],"active":0}},"b":{"Tabs":{"panels":["Project"],"active":0}}}}"#;
+    let bad_split = r#"{"Split":{"vertical":true,"size":{"Ratio":7.0},"a":{"Tabs":{"panels":["Project"],"active":0}},"b":{"Tabs":{"panels":["Timeline"],"active":0}}}}"#;
+    for text in [
+        "{".into(),
+        "{}".into(),
+        "[1, 2]".into(),
+        serde_json::to_string(&Snapshot { version: VERSION + 1, ..valid }).unwrap(),
+        " ".repeat(MAX_BYTES + 1),
+        earlier(twice),
+        earlier(bad_split),
+        earlier(r#"{"Tabs":{"panels":["NoSuchPanel"],"active":0}}"#),
+        earlier(&deep),
+        r#"{"version":1,"workspace":"Default"}"#.into(),
+        r#"{"workspaces":{"Mine":{"Tabs":{"panels":["Composition"],"active":3}}}}"#.into(),
+    ] {
+        let config = MemoryConfig::default();
+        config.write(FILE, &text).unwrap();
+        let mut ui = UiState::default();
+        let mut store = WorkspaceStore::load(Some(&config), &mut ui);
+        assert!(store.error.is_some());
+        assert_eq!(ui.workspace, "Default");
+        assert_eq!(ui.dock, UiState::default().dock);
+        ui.focused = PanelKind::Project;
+        ui.dock = minimal();
+        assert!(!store.save(Some(&config), &ui).unwrap());
+        assert!(store.save_now(Some(&config), &ui).unwrap_err().contains("couldn't be loaded"));
+        assert_eq!(config.read(FILE).as_deref(), Some(text.as_str()));
+        assert_eq!(config.read(BACKUP), None);
+    }
+}
+
+/// A file written by EffectCraft 0.10 (craft-libs 5c874d51): the Default workspace with
+/// Preview floating, Render Queue floating in its own native window, Align closed,
+/// Effects & Presets moved into the Project group and Audio split beside the Timeline,
+/// saved as "My Layout"; then Layer closed.
+const V1: &str = include_str!("../../tests/fixtures/workspaces-v1.json");
+
+#[test]
+fn version_one_file_loads_with_every_panel_in_place() {
+    let config = MemoryConfig::default();
+    config.write(FILE, V1).unwrap();
+    let mut ui = UiState::default();
+    let store = WorkspaceStore::load(Some(&config), &mut ui);
+    assert_eq!(store.error, None);
+    assert_eq!(ui.workspace, "My Layout");
+    assert_eq!(ui.focused, PanelKind::Composition);
+    use PanelKind::*;
+    let root = crate::dock::hsplit(
+        SplitSize::FixedSecond(300.0),
+        crate::dock::vsplit(
+            SplitSize::Ratio(0.56),
+            crate::dock::hsplit(SplitSize::FixedFirst(300.0), crate::dock::tabs(&[Project, EffectControls, EffectsPresets], 2), tabs(&[Composition])),
+            crate::dock::hsplit(SplitSize::Ratio(0.5), tabs(&[Timeline]), tabs(&[Audio])),
+        ),
+        tabs(&[Properties]),
+    );
+    assert_eq!(ui.dock.layout.root, Some(root));
+    let floating: Vec<_> = ui.dock.layout.floating.iter().map(|w| (w.panels().copied().collect::<Vec<_>>(), w.rect, w.native)).collect();
+    assert_eq!(
+        floating,
+        [
+            (vec![Preview], [900.0, 120.0, 300.0, 260.0], None),
+            (vec![RenderQueue], [200.0, 500.0, 520.0, 240.0], Some(crate::dock_ui::sanitized_window_rect([200.0, 500.0, 520.0, 240.0]))),
+        ]
+    );
+    // Closed panels stay closed.
+    for panel in [Align, Layer] {
+        assert!(!ui.dock.is_open(panel), "{panel:?}");
+    }
+    // The native window's place is its outer position until the main window reports its
+    // frame (here a 28-point title bar); the file is not rewritten before.
+    let id = ui.dock.layout.floating[1].id;
+    assert_eq!(ui.native_outer, [id]);
+    let mut store = store;
+    assert!(!store.save(Some(&config), &ui).unwrap());
+    let outer = egui::Rect::from_min_size(egui::pos2(10.0, 20.0), egui::vec2(1600.0, 1000.0));
+    crate::dock_ui::native_outer_to_content(&mut ui, Some(outer), Some(outer.translate(egui::vec2(0.0, 28.0))), 0.1);
+    assert_eq!(ui.dock.layout.floating[1].native, Some([200.0, 528.0, 520.0, 240.0]));
+    assert!(ui.native_outer.is_empty());
+    assert!(store.save(Some(&config), &ui).unwrap());
+    // The named workspace still has Layer, closed only after it was saved.
+    let saved = ui.saved_workspaces.get("My Layout").unwrap();
+    assert!(saved.is_docked(Layer) && saved.is_floating(Preview) && !saved.is_open(Align));
+    assert_eq!(saved.layout.floating.iter().filter_map(|w| w.native).count(), 0);
+}
+
+#[test]
+fn version_one_file_is_rewritten_once_in_the_current_format_and_kept_as_a_backup() {
+    let config = MemoryConfig::default();
+    config.write(FILE, V1).unwrap();
+    let mut ui = UiState::default();
+    let mut store = WorkspaceStore::load(Some(&config), &mut ui);
+    // A backend that reports no window positions: the native place stays as it was.
+    let native = ui.dock.layout.floating[1].native;
+    crate::dock_ui::native_outer_to_content(&mut ui, None, None, 1.0);
+    assert!(!ui.native_outer.is_empty(), "waits for a report");
+    crate::dock_ui::native_outer_to_content(&mut ui, None, None, 5.0);
+    assert!(ui.native_outer.is_empty());
+    assert_eq!(ui.dock.layout.floating[1].native, native);
+    let migrated = Snapshot::capture(&ui);
+    assert!(store.has_changes(&ui), "the migrated layout is written without waiting for an edit");
+    assert!(store.save(Some(&config), &ui).unwrap());
+    assert_eq!(config.read(BACKUP).as_deref(), Some(V1));
+    let text = config.read(FILE).unwrap();
+    assert_eq!(serde_json::from_str::<serde_json::Value>(&text).unwrap()["version"], VERSION);
+    assert!(!store.has_changes(&ui));
+    let mut restored = UiState::default();
+    let reloaded = WorkspaceStore::load(Some(&config), &mut restored);
+    assert_eq!(reloaded.error, None);
+    assert!(!reloaded.has_changes(&restored));
+    assert_eq!(Snapshot::capture(&restored), migrated);
+}
+
+#[test]
+fn stacked_frames_with_tabs_and_an_empty_root_migrate() {
+    let text = r#"{"version":1,"workspace":"Mine","dock":{"Tabs":{"panels":[],"active":0}},
+            "floating":[{"panels":["Project"],"active":0,"rect":[10.0,10.0,300.0,200.0]}],
+            "focused":"Project","maximized":null,
+            "saved_workspaces":{"Mine":{"Stack":{"entries":[{"panel":"Info","open":true},{"panels":["Audio","Preview"],"active":1,"open":true,"height":80.0}]}},
+                "Column":{"Stack":{"entries":[{"panel":"Align","open":false},{"panel":"Preview","open":true,"height":46.0},{"panels":["Properties","Paint"],"active":1,"open":false,"height":300.0},{"panel":"Info","open":true}]}}},
+            "saved_floating":{"Gone":[{"panels":["Align"],"active":0,"rect":[0.0,0.0,100.0,100.0]}]}}"#;
+    let config = MemoryConfig::default();
+    config.write(FILE, text).unwrap();
+    let mut ui = UiState::default();
+    let store = WorkspaceStore::load(Some(&config), &mut ui);
+    assert_eq!(store.error, None);
+    assert_eq!(ui.dock.layout.root, None);
+    assert!(ui.dock.is_floating(PanelKind::Project));
+    use PanelKind::*;
+    // Each open frame is a tab group with all its tabs; a frame's height is a fixed size
+    // (with its tab strip), and the frame without one takes the rest.
+    let column = crate::dock::vsplit(SplitSize::FixedSecond(80.0 + crate::dock::TAB_STRIP), tabs(&[Info]), crate::dock::tabs(&[Audio, Preview], 1));
+    assert_eq!(ui.saved_workspaces.get("Mine").and_then(|w| w.layout.root.clone()), Some(column));
+    // Closed frames' tabs join the open frame above them, or below at the top.
+    let column = crate::dock::vsplit(SplitSize::FixedFirst(46.0 + crate::dock::TAB_STRIP), tabs(&[Preview, Properties, Paint, Align]), tabs(&[Info]));
+    assert_eq!(ui.saved_workspaces.get("Column").and_then(|w| w.layout.root.clone()), Some(column));
+    assert_eq!(ui.saved_workspaces.len(), 2, "floating groups of no named workspace are dropped");
+}
+
+#[test]
+fn explicit_save_without_a_settings_folder_is_an_error() {
+    let mut ui = UiState::default();
+    let mut store = WorkspaceStore::load(None, &mut ui);
+    ui.focused = PanelKind::Project;
+    assert!(!store.save(None, &ui).unwrap());
+    assert!(store.save_now(None, &ui).is_err());
+}
+
+#[test]
+fn explicit_save_with_nothing_new_succeeds() {
+    let config = MemoryConfig::default();
+    let mut ui = UiState::default();
+    let mut store = WorkspaceStore::load(Some(&config), &mut ui);
+    ui.focused = PanelKind::Project;
+    store.save_now(Some(&config), &ui).unwrap();
+    store.save_now(Some(&config), &ui).unwrap();
+    assert!(config.read(FILE).is_some());
+}
+
+#[test]
+fn invalid_tabs_split_and_deep_tree_are_rejected() {
+    let mut snapshot = Snapshot::capture(&UiState::default());
+    snapshot.dock = Workspace::new(Layout { root: Some(Node::Tabs { panels: vec![PanelKind::Project], active: usize::MAX }), floating: vec![] });
+    assert!(snapshot.validate().is_err());
+    let split = |size, first, second| Node::Split { axis: SplitAxis::Horizontal, size, first: Box::new(first), second: Box::new(second) };
+    snapshot.dock = Workspace::new(Layout {
+        root: Some(split(SplitSize::FixedFirst(f32::NAN), tabs(&[PanelKind::Project]), tabs(&[PanelKind::Timeline]))),
+        floating: vec![],
+    });
+    assert!(snapshot.validate().is_err());
+    let mut root = tabs(&[PanelKind::Composition]);
+    for _ in 0..=craft_ui::docking::MAX_DEPTH {
+        root = split(SplitSize::Ratio(0.5), root, tabs(&[]));
+    }
+    snapshot.dock = Workspace::new(Layout { root: Some(root), floating: vec![] });
+    assert!(snapshot.validate().is_err());
+    // A panel in two places.
+    snapshot.dock = Workspace::new(Layout {
+        root: Some(tabs(&[PanelKind::Project])),
+        floating: vec![Floating::single(vec![PanelKind::Project], 0, [0.0, 0.0, 200.0, 100.0])],
+    });
+    assert!(snapshot.validate().is_err());
+}
+
+#[test]
+fn closing_all_docked_panels_remains_a_persistable_layout() {
+    let config = MemoryConfig::default();
+    let mut ui = UiState::default();
+    let mut store = WorkspaceStore::load(Some(&config), &mut ui);
+    for panel in ui.dock.panels() {
+        ui.dock.apply(Action::Close { panel }, crate::dock::permissions).unwrap();
+    }
+    assert!(ui.dock.layout.root.is_none());
+    assert!(store.save(Some(&config), &ui).unwrap());
+    let mut restored = UiState::default();
+    let loaded = WorkspaceStore::load(Some(&config), &mut restored);
+    assert!(loaded.error.is_none());
+    assert_eq!(restored.dock, ui.dock);
+}
+
+#[test]
+fn floating_groups_and_named_snapshots_roundtrip_without_document_state() {
+    let config = MemoryConfig::default();
+    let mut ui = UiState::default();
+    let mut store = WorkspaceStore::load(Some(&config), &mut ui);
+    ui.workspace = "Floating".into();
+    ui.dock.apply(Action::Float { panel: PanelKind::Preview, rect: [50.0, 80.0, 200.0, 160.0] }, crate::dock::permissions).unwrap();
+    ui.dock.apply(Action::Close { panel: PanelKind::Align }, crate::dock::permissions).unwrap();
+    ui.saved_workspaces.insert(ui.workspace.clone(), ui.dock.clone());
+    ui.maximized = Some(PanelKind::Composition);
+    ui.project_search = "do not persist".into();
+    assert!(store.save(Some(&config), &ui).unwrap());
+    let mut restored = UiState::default();
+    WorkspaceStore::load(Some(&config), &mut restored);
+    assert_eq!(Snapshot::capture(&restored), Snapshot::capture(&ui));
+    // The closed panel's place comes back with it.
+    assert!(restored.dock.hidden.iter().any(|(p, _)| *p == PanelKind::Align));
+    assert!(restored.project_search.is_empty());
+}
+
+#[test]
+fn restored_viewer_slots_do_not_reuse_ids_or_restore_document_links() {
+    let config = MemoryConfig::default();
+    let mut ui = UiState::default();
+    let mut store = WorkspaceStore::load(Some(&config), &mut ui);
+    let two = |viewer| Workspace::new(Layout { root: Some(tabs(&[PanelKind::Composition, PanelKind::Viewer(viewer)])), floating: vec![] });
+    ui.dock = two(2);
+    ui.saved_workspaces.insert("Two views".into(), two(5));
+    ui.viewers.insert(2, Some(42));
+    assert!(store.save(Some(&config), &ui).unwrap());
+    let mut app = crate::EffectcraftApp::new(effectcraft_engine::Session::default());
+    WorkspaceStore::load(Some(&config), &mut app.ui);
+    assert_eq!(app.ui.viewers.get(&2), Some(&None));
+    assert_eq!(app.ui.viewers.get(&5), Some(&None));
+    assert_eq!(crate::panels::viewers::new_viewer(&mut app), 6);
+    assert!(app.ui.dock.is_docked(PanelKind::Viewer(2)));
+}
+
+#[test]
+fn invalid_viewer_ids_are_rejected_in_every_workspace_reference() {
+    for id in [0, MAX_VIEWER_ID + 1, u32::MAX] {
+        for location in 0..8 {
+            let mut snapshot = Snapshot::capture(&UiState::default());
+            let panel = PanelKind::Viewer(id);
+            let docked = Workspace::new(Layout { root: Some(tabs(&[panel])), floating: vec![] });
+            let stacked =
+                Workspace::new(Layout { root: Some(Node::Stack { entries: vec![StackEntry { panel, open: true, height: None }] }), floating: vec![] });
+            let floating = Workspace::new(Layout {
+                root: Some(tabs(&[PanelKind::Composition])),
+                floating: vec![Floating::single(vec![panel], 0, [0.0, 0.0, 200.0, 100.0])],
+            });
+            let mut hidden = Workspace::new(Layout { root: Some(tabs(&[PanelKind::Composition, panel])), floating: vec![] });
+            hidden.apply(Action::Close { panel }, crate::dock::permissions).unwrap();
+            match location {
+                0 => snapshot.focused = panel,
+                1 => snapshot.maximized = Some(panel),
+                2 => snapshot.dock = docked,
+                3 => snapshot.dock = stacked,
+                4 => snapshot.dock = floating,
+                5 => snapshot.dock = hidden,
+                6 => {
+                    snapshot.saved_workspaces.insert("Saved".into(), stacked);
+                }
+                _ => {
+                    snapshot.saved_workspaces.insert("Saved".into(), floating);
+                }
+            }
+            assert!(snapshot.validate().is_err(), "viewer {id} at location {location} must be rejected");
+        }
+    }
+}
+
+#[test]
+fn hostile_native_window_places_are_made_safe_on_load() {
+    let config = MemoryConfig::default();
+    let mut ui = UiState::default();
+    let mut store = WorkspaceStore::load(Some(&config), &mut ui);
+    ui.dock.apply(Action::Float { panel: PanelKind::Project, rect: [10.0, 10.0, 300.0, 200.0] }, crate::dock::permissions).unwrap();
+    ui.dock.apply(Action::SetNative { panel: PanelKind::Project, rect: Some([90_000.0, -90_000.0, 1.0e5, 0.5]) }, crate::dock::permissions).unwrap();
+    assert!(store.save(Some(&config), &ui).unwrap());
+    let mut restored = UiState::default();
+    WorkspaceStore::load(Some(&config), &mut restored);
+    let native = restored.dock.layout.floating.iter().find(|w| w.contains(&PanelKind::Project)).and_then(|w| w.native).unwrap();
+    assert_eq!(native, crate::dock_ui::sanitized_window_rect(native));
+    assert!(native[2] <= crate::dock_ui::PANEL_WINDOW_MAX && native[3] >= crate::dock_ui::PANEL_WINDOW_MIN[1]);
+}
+
+#[test]
+fn failed_write_keeps_previous_snapshot_and_retries() {
+    struct Fails<'a>(&'a MemoryConfig);
+    impl ConfigStore for Fails<'_> {
+        fn read(&self, name: &str) -> Option<String> {
+            self.0.read(name)
+        }
+        fn write(&self, _name: &str, _data: &str) -> std::io::Result<()> {
+            Err(std::io::Error::other("synthetic full disk"))
+        }
+        fn remove(&self, _name: &str) -> std::io::Result<()> {
+            Err(std::io::Error::other("unused"))
+        }
+    }
+    let config = MemoryConfig::default();
+    let mut ui = UiState::default();
+    let mut store = WorkspaceStore::load(Some(&config), &mut ui);
+    ui.focused = PanelKind::Project;
+    assert!(store.save(Some(&config), &ui).unwrap());
+    let previous = config.read(FILE).unwrap();
+    ui.focused = PanelKind::Timeline;
+    assert!(store.save(Some(&Fails(&config)), &ui).unwrap_err().contains("synthetic full disk"));
+    assert_eq!(config.read(FILE).as_deref(), Some(previous.as_str()));
+    assert!(store.has_changes(&ui));
+    assert!(store.save(Some(&config), &ui).unwrap());
+    let mut restored = UiState::default();
+    WorkspaceStore::load(Some(&config), &mut restored);
+    assert_eq!(restored.focused, PanelKind::Timeline);
+}