diff --git a/crates/engine/src/library.rs b/crates/engine/src/library.rs
index 4382160a..88fa2f3f 100644
--- a/crates/engine/src/library.rs
+++ b/crates/engine/src/library.rs
@@ -295,7 +295,13 @@ impl Session {
         {
             log::error!("library: {e}");
         }
-        let (mut journal, catalog, report) = Journal::open(catalog)?;
+        let (mut journal, mut catalog, report) = Journal::open(catalog)?;
+        // A loaded catalog counts revisions from 0, like every other one. Caches (sidebar counts,
+        // keyword tree, the grid's list…) are keyed on the revision, so give each library loaded
+        // in this process its own range: otherwise an empty library opened after one that was
+        // never edited this session would look unchanged and show the old library's numbers.
+        static LOADS: std::sync::atomic::AtomicU64 = std::sync::atomic::AtomicU64::new(0);
+        catalog.revision = LOADS.fetch_add(1, std::sync::atomic::Ordering::Relaxed).wrapping_add(1) << 32;
         self.catalog = catalog;
         self.undo.clear();
         self.redo.clear();
diff --git a/crates/ui-egui/src/lib.rs b/crates/ui-egui/src/lib.rs
index a4addbf3..a271bec9 100644
--- a/crates/ui-egui/src/lib.rs
+++ b/crates/ui-egui/src/lib.rs
@@ -42,6 +42,8 @@ mod tests_quit_unsaved;
 #[cfg(test)]
 mod tests_scroll;
 #[cfg(test)]
+mod tests_switch_library;
+#[cfg(test)]
 mod tests_unsaved;
 
 use std::sync::mpsc::{Receiver, Sender};
diff --git a/crates/ui-egui/src/tests_switch_library.rs b/crates/ui-egui/src/tests_switch_library.rs
new file mode 100644
index 00000000..d7bffc0d
--- /dev/null
+++ b/crates/ui-egui/src/tests_switch_library.rs
@@ -0,0 +1,43 @@
+//! Switching libraries must not leave the old library's sidebar numbers, keyword tree or date
+//! groups on screen. A library loaded from disk starts at catalog revision 0, and so does a brand
+//! new empty one, so caches keyed on the revision alone would see "nothing changed".
+
+use serde_json::json;
+
+use crate::{LightcraftApp, Services};
+
+#[test]
+fn opening_another_library_drops_the_old_librarys_cached_panels() {
+    let dir = std::env::temp_dir().join(format!("lc-ui-switchlib-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    let (a, b) = (dir.join("a"), dir.join("b"));
+    std::fs::create_dir_all(&a).unwrap();
+    std::fs::create_dir_all(&b).unwrap();
+
+    // library A with photos, reopened from disk (as at launch)
+    let mut session = lightcraft_engine::Session::new().with_fs();
+    session.open_library(&a, true).unwrap();
+    session.close_library().unwrap();
+    session.open_library(&a, false).unwrap();
+    assert!(!session.catalog.is_empty());
+
+    let mut app = LightcraftApp::new(session, Services::default());
+    let (cat, caches) = (&app.session.catalog, &mut app.caches);
+    assert!(caches.counts(cat).total > 0);
+    assert!(!caches.keyword_tree(cat).is_empty());
+    assert!(!caches.date_groups(cat).is_empty());
+
+    // the grid's own list is cached too
+    assert!(!app.session.visible().is_empty());
+
+    app.run("app.openLibrary", json!({"path": b.to_string_lossy()})).unwrap();
+    assert!(app.session.catalog.is_empty(), "library B is empty");
+    let (cat, caches) = (&app.session.catalog, &mut app.caches);
+    assert_eq!(caches.counts(cat).total, 0, "All Photos count");
+    assert_eq!(caches.counts(cat).picks, 0);
+    assert!(caches.keyword_tree(cat).is_empty(), "keywords");
+    assert!(caches.date_groups(cat).is_empty(), "By Date");
+    assert!(app.session.visible().is_empty(), "grid");
+
+    let _ = std::fs::remove_dir_all(&dir);
+}