diff --git a/crates/ui-egui/src/panels/left/folders.rs b/crates/ui-egui/src/panels/left/folders.rs
index 6e6d8a651a..d5b4d21956 100644
--- a/crates/ui-egui/src/panels/left/folders.rs
+++ b/crates/ui-egui/src/panels/left/folders.rs
@@ -552,18 +552,37 @@ fn library_node_for(tree: &[FolderNode], path: &str) -> Option<(FolderNode, Stri
     Some((node, name))
 }
 
+/// Move Folder To… can't start while Open Library… or New Library… waits for its folder: the
+/// dialogs answer in the order they were opened ([`crate::pick::poll`]), so the library could
+/// switch first and the move then run in the other library, moving the folder on disk with
+/// nothing to relink (issue #3140).
+fn can_move_folder(app: &LightcraftApp) -> Result<(), String> {
+    for (command, label) in [("app.openLibrary", "Open Library…"), ("app.newLibrary", "New Library…")] {
+        if app.pending_picks.iter().any(|p| p.command == command) {
+            return Err(format!("wait for {label} to finish before moving a folder"));
+        }
+    }
+    Ok(())
+}
+
 /// Move Folder To… of a folder row (widget `folderMoveTo`): asks for the destination through the
 /// shared folder dialog, off the UI thread where the host has one (issue #3140: a dialog on the UI
 /// thread froze the window); `folder.move` then runs when it closes ([`crate::pick::poll`]).
+/// Disabled while a library dialog is up ([`can_move_folder`]).
 fn move_folder_item(app: &mut LightcraftApp, ui: &mut egui::Ui, path: &str) {
     if app.services.pick_folder.is_none() && app.services.picker.is_none() {
         return;
     }
-    let r = ui.button(crate::i18n::tr("Move Folder To…"));
+    let r = ui.add_enabled(can_move_folder(app).is_ok(), egui::Button::new(crate::i18n::tr("Move Folder To…")));
     register(ui, "folderMoveTo", r.rect);
     if !r.clicked() {
         return;
     }
+    if let Err(e) = can_move_folder(app) {
+        app.toast(ui.ctx(), e);
+        ui.close();
+        return;
+    }
     let req = crate::pick::PickRequest::folder(crate::i18n::tr("Move Folder To…"));
     let params = json!({"path": path});
     let picked = crate::pick::ask(app, "folder.move", &params, "into", req, |s| s.pick_folder.as_mut().and_then(|f| f()).map(|x| vec![x]));
diff --git a/crates/ui-egui/src/tests/move_folder.rs b/crates/ui-egui/src/tests/move_folder.rs
index 58358c2512..71ff3df620 100644
--- a/crates/ui-egui/src/tests/move_folder.rs
+++ b/crates/ui-egui/src/tests/move_folder.rs
@@ -179,3 +179,33 @@ fn no_library_switch_while_move_folder_to_waits_for_its_destination() {
     h.app.run("app.openLibrary", json!({"path": other})).expect("the switch works once the move is done");
     assert_eq!(library(&h), Some(other));
 }
+
+/// Issue #3140: while Open Library… waits for its folder, Move Folder To… can't start (both
+/// dialogs answer in the order opened, so the library could switch before the move ran, which
+/// would then move the folder in the other library with nothing to relink): the item is disabled,
+/// no destination is asked for, and the folder stays. Once the library dialog is cancelled it works.
+#[test]
+fn move_folder_to_waits_for_open_library_to_finish() {
+    let dir = Scratch::new("after-open");
+    std::fs::create_dir_all(dir.path("dest")).unwrap();
+    let (mut h, asked, blocking) = app_with_trip(&dir);
+    assert_eq!(h.app.run("app.openLibrary", json!({})).ok(), Some(serde_json::Value::Null));
+    assert_eq!(asked.lock().unwrap().len(), 1, "the Open Library dialog is up");
+    open_row_menu(&mut h, &format!("source:libfolder:{}", dir.path("trip")));
+    let _ = h.request("ui.clickWidget", json!({"id": "folderMoveTo"}), T);
+    h.settle(SETTLE);
+    assert_eq!(asked.lock().unwrap().len(), 1, "no destination is asked for");
+    assert_eq!(blocking.load(Ordering::Relaxed), 0, "not on the UI thread either");
+    assert!(!h.app.pending_picks.iter().any(|p| p.command == "folder.move"), "nothing waits to move");
+    assert!(std::path::Path::new(&dir.path("trip/a.png")).exists(), "the folder stays");
+    // the Open Library dialog is cancelled: Move Folder To… asks for its destination again
+    asked.lock().unwrap()[0].1.send(vec![]).unwrap();
+    h.settle(SETTLE);
+    assert!(h.app.pending_picks.is_empty());
+    open_row_menu(&mut h, &format!("source:libfolder:{}", dir.path("trip")));
+    let r = h.request("ui.clickWidget", json!({"id": "folderMoveTo"}), T);
+    assert_eq!(r["ok"], true, "{r}");
+    h.step();
+    assert_eq!(asked.lock().unwrap().len(), 2, "the destination is asked for");
+    assert!(h.app.pending_picks.iter().any(|p| p.command == "folder.move"));
+}
diff --git a/docs/whats-new.md b/docs/whats-new.md
index 9c197f39c0..e121e5b33a 100644
--- a/docs/whats-new.md
+++ b/docs/whats-new.md
@@ -7,7 +7,8 @@
   Folder… do: the window keeps drawing and answering while you choose, and the folder moves when the dialog closes,
   with the same "Moved; N photo(s) relinked" message. Before, the dialog held up the whole window until it closed;
   on Linux with X11 the app could stop responding altogether. While the dialog is open, another library can't be
-  opened (the move belongs to the library it was started in).
+  opened (the move belongs to the library it was started in), and while Open Library… or New Library… waits for
+  its folder, Move Folder To… is unavailable.
 
 ## 2026-10-24