diff --git a/crates/engine/src/cmd/edit.rs b/crates/engine/src/cmd/edit.rs
index 30437b15..19225abb 100644
--- a/crates/engine/src/cmd/edit.rs
+++ b/crates/engine/src/cmd/edit.rs
@@ -18,7 +18,7 @@ pub fn specs() -> Vec<CommandSpec> {
         cmd!("edit.pasteText", "Paste and Match Formatting", ["Edit"], Some("Cmd+Shift+V"), "{text?}", has_doc, paste_text),
         cmd!("edit.duplicate", "Duplicate", ["Edit"], Some("Cmd+D"), "{ids?}", has_selection, duplicate),
         cmd!("edit.delete", "Delete", ["Edit"], Some("Delete"), "{ids?, scope?: slides}", has_doc, delete),
-        cmd!(noundo "edit.selectAll", "Select All", ["Edit"], Some("Cmd+A"), "{}", has_slide, select_all),
+        cmd!(noundo "edit.selectAll", "Select All", ["Edit"], Some("Cmd+A"), "{scope?: slides}", has_slide, select_all),
         cmd!(noundo "edit.deselect", "Deselect", [], Some("Escape"), "{}", has_doc, deselect),
         cmd!(noundo "edit.select", "Select Objects", [], None, "{ids: [id], add?: bool, toggle?: bool}", has_slide, select),
     ]
@@ -323,7 +323,12 @@ fn count(v: &[Shape]) -> usize {
     n
 }
 
-fn select_all(s: &mut Session, _p: &Value) -> Result<Value> {
+fn select_all(s: &mut Session, p: &Value) -> Result<Value> {
+    match p.get("scope") {
+        None | Some(Value::Null) => {}
+        Some(Value::String(v)) if v == "slides" => return select_all_slides(s),
+        Some(_) => return Err(bad("edit.selectAll", "scope must be \"slides\"")),
+    }
     if s.doc()?.selection.text.is_some() {
         return s.execute("text.selectAll", &json!({}));
     }
@@ -335,6 +340,22 @@ fn select_all(s: &mut Session, _p: &Value) -> Result<Value> {
     Ok(json!({"ids": ids}))
 }
 
+/// Thumbnail-pane / sorter select all: every slide, hidden ones included. The current
+/// slide stays where it is (the canvas must not jump), so this is not `slide.selectSlides`.
+fn select_all_slides(s: &mut Session) -> Result<Value> {
+    if s.doc()?.selection.target != crate::Target::Slides {
+        return Err(bad("edit.selectAll", "the slide list is not shown while editing a master"));
+    }
+    let ids: Vec<SlideId> = s.doc()?.doc.slides.iter().map(|x| x.id).collect();
+    s.select(|_, sel| {
+        sel.slides = ids.clone();
+        sel.shapes.clear();
+        sel.text = None;
+        sel.cells = None;
+    })?;
+    Ok(json!({"selected": ids}))
+}
+
 fn deselect(s: &mut Session, _p: &Value) -> Result<Value> {
     s.painter = None;
     s.anim_painter = None;
diff --git a/crates/engine/src/tests.rs b/crates/engine/src/tests.rs
index 9aefd0b7..0fa8357d 100644
--- a/crates/engine/src/tests.rs
+++ b/crates/engine/src/tests.rs
@@ -543,3 +543,43 @@ fn inserted_hyperlinks_look_like_links() {
     s.execute("format.underline", &json!({})).unwrap();
     assert_eq!(s.execute("format.state", &json!({})).unwrap()["underline"], false);
 }
+
+#[test]
+fn select_all_slides_scope() {
+    let mut s = session();
+    // One slide: selects it, no panic.
+    let r = s.execute("edit.selectAll", &json!({"scope": "slides"})).unwrap();
+    assert_eq!(r["selected"].as_array().map(Vec::len), Some(1));
+    for _ in 0..3 {
+        s.execute("slide.new", &json!({})).unwrap();
+    }
+    s.execute("slide.hide", &json!({"index": 1})).unwrap();
+    s.execute("slide.go", &json!({"index": 1})).unwrap();
+    let before = s.doc().unwrap().selection.slide;
+    s.execute("edit.selectAll", &json!({"scope": "slides"})).unwrap();
+    let st = s.doc().unwrap();
+    let all: Vec<_> = st.doc.slides.iter().map(|x| x.id).collect();
+    assert_eq!(st.selection.slides, all);
+    assert_eq!(st.selection.slide, before, "the current slide must not jump");
+    assert!(st.selection.shapes.is_empty() && st.selection.text.is_none());
+    assert_eq!(st.doc.slides.len(), 4);
+}
+
+#[test]
+fn select_all_slides_leaves_shape_select_all_alone() {
+    let mut s = session();
+    s.execute("shape.insert", &json!({"preset": "rect", "rect": [10, 10, 50, 50]})).unwrap();
+    s.execute("slide.new", &json!({})).unwrap();
+    s.execute("slide.go", &json!({"index": 0})).unwrap();
+    // No scope: still selects shapes on the current slide.
+    s.execute("edit.selectAll", &json!({})).unwrap();
+    assert!(!s.doc().unwrap().selection.shapes.is_empty());
+    assert!(s.doc().unwrap().selection.slides.len() <= 1);
+}
+
+#[test]
+fn select_all_slides_bad_scope_is_an_error() {
+    let mut s = session();
+    assert!(s.execute("edit.selectAll", &json!({"scope": "everything"})).is_err());
+    assert!(s.execute("edit.selectAll", &json!({"scope": 3})).is_err());
+}