diff --git a/crates/engine/src/cmd/fileio/load.rs b/crates/engine/src/cmd/fileio/load.rs
index 788d34206..73aa81c2e 100644
--- a/crates/engine/src/cmd/fileio/load.rs
+++ b/crates/engine/src/cmd/fileio/load.rs
@@ -395,14 +395,8 @@ fn is_loss(note: &str) -> bool {
 /// it left something out (hidden text, art or layers), unless `p` has `acknowledgeLoss: true`.
 /// Another name keeps the original file, with all it has.
 pub(crate) fn check_not_lossy_overwrite(st: &crate::DocState, target: &str, p: &Value, cmd: &str) -> Result<()> {
-    let Some(source) = st.imported_from.as_deref().filter(|_| !st.import_losses.is_empty()) else { return Ok(()) };
-    if bool_or(p, "acknowledgeLoss", false) || !same_file(source, target) {
-        return Ok(());
-    }
-    let mut what = st.import_losses.iter().take(3).map(|n| format!("“{n}”")).collect::<Vec<_>>().join("; ");
-    if st.import_losses.len() > 3 {
-        what.push_str(&format!("; {} more", st.import_losses.len() - 3));
-    }
+    let Some(losses) = overwrite_losses(st, target, p) else { return Ok(()) };
+    let what = losses_summary(losses);
     Err(bad(
         cmd,
         format!(
@@ -411,6 +405,23 @@ pub(crate) fn check_not_lossy_overwrite(st: &crate::DocState, target: &str, p: &
     ))
 }
 
+/// What writing the file `target` for document `st` would lose for good: the notes of what reading
+/// it left out when `target` is the file `st` was read from, unless `p` has `acknowledgeLoss: true`.
+/// The UI asks before such a write and repeats it with `acknowledgeLoss` ([`check_not_lossy_overwrite`]).
+pub fn overwrite_losses<'a>(st: &'a crate::DocState, target: &str, p: &Value) -> Option<&'a [String]> {
+    let source = st.imported_from.as_deref().filter(|_| !st.import_losses.is_empty())?;
+    (!bool_or(p, "acknowledgeLoss", false) && same_file(source, target)).then_some(st.import_losses.as_slice())
+}
+
+/// Up to three of `losses`, quoted, and how many more.
+pub fn losses_summary(losses: &[String]) -> String {
+    let mut what = losses.iter().take(3).map(|n| format!("“{n}”")).collect::<Vec<_>>().join("; ");
+    if losses.len() > 3 {
+        what.push_str(&format!("; {} more", losses.len() - 3));
+    }
+    what
+}
+
 /// Do `a` and `b` name one file (spelled differently, or through a link)?
 fn same_file(a: &str, b: &str) -> bool {
     match (std::fs::canonicalize(a), std::fs::canonicalize(b)) {
diff --git a/crates/engine/src/cmd/fileio/mod.rs b/crates/engine/src/cmd/fileio/mod.rs
index dad634b65..4a71c4dba 100644
--- a/crates/engine/src/cmd/fileio/mod.rs
+++ b/crates/engine/src/cmd/fileio/mod.rs
@@ -53,6 +53,7 @@ pub(crate) use load::import_svg;
 pub(crate) use load::native_file;
 pub(crate) use load::source;
 pub use load::{Loaded, RasterImage, detect, file_name, load, load_with, open_bytes, open_bytes_with, open_template, raster_image};
+pub use load::{losses_summary, overwrite_losses};
 pub use native::with_compression_pref;
 pub use pdfimport::{LoadOptions, page_document};
 pub(crate) use save::job_for;
diff --git a/crates/ui-egui/src/dialogs/package.rs b/crates/ui-egui/src/dialogs/package.rs
index 234141c9f..ca49854fb 100644
--- a/crates/ui-egui/src/dialogs/package.rs
+++ b/crates/ui-egui/src/dialogs/package.rs
@@ -104,7 +104,11 @@ fn confirm(app: &mut VectorcraftApp, d: &Dialog) -> Result<Value, String> {
     }
     // The package holds the document as saved.
     if app.session.active().is_some_and(|st| st.is_dirty()) {
-        io::save(app, vectorcraft_engine::cmd::fileio::SaveMode::Save, &json!({}), false)?;
+        let r = io::save(app, vectorcraft_engine::cmd::fileio::SaveMode::Save, &json!({}), false)?;
+        // The save asks first (it would replace a file that loses what opening it left out).
+        if r.get("pending").is_some() {
+            return Ok(r);
+        }
     }
     let r = app.run("file.package", params)?;
     app.ui.dialog = None;
diff --git a/crates/ui-egui/src/i18n/es.tsv b/crates/ui-egui/src/i18n/es.tsv
index 068cd35fa..ae9cfbfed 100644
--- a/crates/ui-egui/src/i18n/es.tsv
+++ b/crates/ui-egui/src/i18n/es.tsv
@@ -2147,6 +2147,8 @@
 	Reverse Spine	Invertir eje
 	Revert	Revertir
 	Revert to the saved version of “{name}”?	¿Revertir a la versión guardada de “{name}”?
+	Replace “{name}”, the file this document was opened from?	¿Reemplazar “{name}”, el archivo desde el que se abrió este documento?
+	Opening it left out what VectorCraft can't read yet ({what}), so replacing it loses that for good. Save under another name to keep it.	Al abrirlo quedó fuera lo que VectorCraft aún no puede leer ({what}), así que reemplazarlo lo pierde para siempre. Guárdelo con otro nombre para conservarlo.
 	Revolve…	Revolución…
 	RGB Color	Color RGB
 	Right	Derecha
diff --git a/crates/ui-egui/src/i18n/it.tsv b/crates/ui-egui/src/i18n/it.tsv
index ec309b0e0..6bcba24b0 100644
--- a/crates/ui-egui/src/i18n/it.tsv
+++ b/crates/ui-egui/src/i18n/it.tsv
@@ -2147,6 +2147,8 @@
 	Reverse Spine	Inverti dorsale
 	Revert	Ripristina
 	Revert to the saved version of “{name}”?	Ripristinare la versione salvata di “{name}”?
+	Replace “{name}”, the file this document was opened from?	Sostituire “{name}”, il file da cui è stato aperto questo documento?
+	Opening it left out what VectorCraft can't read yet ({what}), so replacing it loses that for good. Save under another name to keep it.	Aprendolo è rimasto fuori ciò che VectorCraft non sa ancora leggere ({what}), quindi sostituirlo lo perde per sempre. Salva con un altro nome per conservarlo.
 	Revolve…	Rivoluzione…
 	RGB Color	Colore RGB
 	Right	Destra
diff --git a/crates/ui-egui/src/i18n/ja.tsv b/crates/ui-egui/src/i18n/ja.tsv
index 1540e48d1..3d7b6c6ba 100644
--- a/crates/ui-egui/src/i18n/ja.tsv
+++ b/crates/ui-egui/src/i18n/ja.tsv
@@ -2115,6 +2115,8 @@
 	Reverse Path Direction Off	パスの方向を反転: オフ
 	Reverse Path Direction On	パスの方向を反転: オン
 	Revert to the saved version of “{name}”?	「{name}」を保存済みの状態に戻しますか？
+	Replace “{name}”, the file this document was opened from?	このドキュメントの開き元のファイル「{name}」を置き換えますか？
+	Opening it left out what VectorCraft can't read yet ({what}), so replacing it loses that for good. Save under another name to keep it.	開いたときに VectorCraft がまだ読み込めない内容（{what}）が除外されたため、置き換えるとそれは完全に失われます。保持するには別の名前で保存してください。
 	Right Grid:	右グリッド:
 	Right Indent	右インデント
 	Right Plane	右面
diff --git a/crates/ui-egui/src/i18n/pt-br.tsv b/crates/ui-egui/src/i18n/pt-br.tsv
index 1d168bcad..bf3679f92 100644
--- a/crates/ui-egui/src/i18n/pt-br.tsv
+++ b/crates/ui-egui/src/i18n/pt-br.tsv
@@ -1904,6 +1904,8 @@
 	Reverse Spine	Inverter Coluna
 	Revert	Reverter
 	Revert to the saved version of “{name}”?	Reverter para a versão salva de “{name}”?
+	Replace “{name}”, the file this document was opened from?	Substituir “{name}”, o arquivo do qual este documento foi aberto?
+	Opening it left out what VectorCraft can't read yet ({what}), so replacing it loses that for good. Save under another name to keep it.	Ao abri-lo, ficou de fora o que o VectorCraft ainda não consegue ler ({what}), então substituí-lo perde isso para sempre. Salve com outro nome para mantê-lo.
 	Revolve…	Revolver…
 	Right Grid:	Grade Direita:
 	Right Indent	Recuo Direito
diff --git a/crates/ui-egui/src/i18n/ru.tsv b/crates/ui-egui/src/i18n/ru.tsv
index c13dbad08..b4efe1df6 100644
--- a/crates/ui-egui/src/i18n/ru.tsv
+++ b/crates/ui-egui/src/i18n/ru.tsv
@@ -2143,6 +2143,8 @@
 	Reverse Spine	Обратить остов
 	Revert	Вернуть
 	Revert to the saved version of “{name}”?	Вернуться к сохранённой версии «{name}»?
+	Replace “{name}”, the file this document was opened from?	Заменить «{name}» — файл, из которого открыт этот документ?
+	Opening it left out what VectorCraft can't read yet ({what}), so replacing it loses that for good. Save under another name to keep it.	При открытии было пропущено то, что VectorCraft пока не умеет читать ({what}), поэтому замена файла потеряет это навсегда. Чтобы сохранить это, сохраните документ под другим именем.
 	Revolve…	Вращение…
 	RGB Color	Цвет RGB
 	Right	Справа
diff --git a/crates/ui-egui/src/i18n/zh-hans.tsv b/crates/ui-egui/src/i18n/zh-hans.tsv
index 15939595c..0a2acad89 100644
--- a/crates/ui-egui/src/i18n/zh-hans.tsv
+++ b/crates/ui-egui/src/i18n/zh-hans.tsv
@@ -2102,6 +2102,8 @@
 	Reverse Spine	反转路径
 	Revert	恢复
 	Revert to the saved version of “{name}”?	要恢复为“{name}”已存储的版本吗？
+	Replace “{name}”, the file this document was opened from?	要替换“{name}”（打开此文档的源文件）吗？
+	Opening it left out what VectorCraft can't read yet ({what}), so replacing it loses that for good. Save under another name to keep it.	打开时略去了 VectorCraft 尚无法读取的内容（{what}），替换该文件会永久丢失这些内容。要保留它们，请以其他名称存储。
 	Revolve…	回转…
 	RGB Color	RGB 颜色
 	Right	右
diff --git a/crates/ui-egui/src/i18n/zh-hant.tsv b/crates/ui-egui/src/i18n/zh-hant.tsv
index d44527e25..3226c1280 100644
--- a/crates/ui-egui/src/i18n/zh-hant.tsv
+++ b/crates/ui-egui/src/i18n/zh-hant.tsv
@@ -2150,6 +2150,8 @@
 	Reverse Spine	反轉軸線
 	Revert	回復
 	Revert to the saved version of “{name}”?	要回復為「{name}」已儲存的版本嗎？
+	Replace “{name}”, the file this document was opened from?	要取代「{name}」（開啟此文件的來源檔案）嗎？
+	Opening it left out what VectorCraft can't read yet ({what}), so replacing it loses that for good. Save under another name to keep it.	開啟時略過了 VectorCraft 尚無法讀取的內容（{what}），取代該檔案會永久遺失這些內容。若要保留，請以其他名稱儲存。
 	Revolve…	迴轉…
 	RGB Color	RGB 色彩
 	Right	右
diff --git a/crates/ui-egui/src/io.rs b/crates/ui-egui/src/io.rs
index 96913fc04..635697f77 100644
--- a/crates/ui-egui/src/io.rs
+++ b/crates/ui-egui/src/io.rs
@@ -239,9 +239,13 @@ fn plan(app: &VectorcraftApp, mode: SaveMode, p: &Value) -> Result<SavePlan, Str
 /// path?}` while a dialog is open.
 pub fn save(app: &mut VectorcraftApp, mode: SaveMode, p: &Value, ask_options: bool) -> Result<Value, String> {
     remember_view(app);
-    let first = plan(app, mode, p)?;
+    // Writing over the file the document was read from is asked about here, not refused.
+    let first = plan(app, mode, &acknowledged(p))?;
     let ask = ask_options && !has_options(p);
     if let Some(path) = first.path.clone() {
+        if let Some(r) = ask_before_losing(app, &path, save_command(mode), p) {
+            return Ok(r);
+        }
         if ask && matches!(mode, SaveMode::SaveAs | SaveMode::Copy) && matches!(first.format.id, "svg" | "svgz") {
             return ask_format_options(app, mode, first.format, &path);
         }
@@ -261,7 +265,10 @@ pub fn save(app: &mut VectorcraftApp, mode: SaveMode, p: &Value, ask_options: bo
         o.remove("format");
         o.insert("path".into(), json!(with_save_extension(&picked, first.format)));
     }
-    let chosen = plan(app, mode, &q)?;
+    let chosen = plan(app, mode, &acknowledged(&q))?;
+    if let Some(r) = chosen.path.as_deref().and_then(|path| ask_before_losing(app, path, save_command(mode), &q)) {
+        return Ok(r);
+    }
     if ask && asks_options(mode, chosen.format) {
         let path = chosen.path.clone().unwrap_or_default();
         return ask_format_options(app, mode, chosen.format, &path);
@@ -269,6 +276,42 @@ pub fn save(app: &mut VectorcraftApp, mode: SaveMode, p: &Value, ask_options: bo
     write_plan(app, chosen)
 }
 
+/// The UI command that runs a save in `mode`.
+fn save_command(mode: SaveMode) -> &'static str {
+    match mode {
+        SaveMode::Save => "file.save",
+        SaveMode::SaveAs => "file.saveAs",
+        SaveMode::Copy => "file.saveCopy",
+        SaveMode::Template => "file.saveAsTemplate",
+    }
+}
+
+/// `p` with `acknowledgeLoss: true`.
+fn acknowledged(p: &Value) -> Value {
+    let mut p = if p.is_object() { p.clone() } else { json!({}) };
+    p["acknowledgeLoss"] = json!(true);
+    p
+}
+
+/// Writing `path` over the file the active document was read from, when reading it left things
+/// out (hidden text, art or layers VectorCraft can't read yet): asks first, and OK runs `command`
+/// with `params` and `acknowledgeLoss` → `{pending}` while it asks, `None` when nothing is lost.
+fn ask_before_losing(app: &mut VectorcraftApp, path: &str, command: &str, params: &Value) -> Option<Value> {
+    let what = fileio::losses_summary(fileio::overwrite_losses(app.session.active()?, path, params)?);
+    let name = fileio::file_name(path);
+    let message = crate::i18n::fmt(tl!("Replace “{name}”, the file this document was opened from?"), &[("name", &name)]);
+    let detail = crate::i18n::fmt(
+        tl!("Opening it left out what VectorCraft can't read yet ({what}), so replacing it loses that for good. Save under another name to keep it."),
+        &[("what", &what)],
+    );
+    let mut params = acknowledged(params);
+    if command != "file.save" {
+        params["path"] = json!(path);
+    }
+    dialogs::confirm::ask(app, &message, &detail, command, params);
+    Some(json!({ "pending": dialogs::confirm::KIND }))
+}
+
 /// Does a save (`mode`) to a picked file of format `f` ask for its options first? Native and `.ai`
 /// files only on Save As (the options dialog after the save panel); Save, a Copy and templates
 /// reuse the remembered options or Use Compression.
@@ -421,6 +464,13 @@ pub fn export(app: &mut VectorcraftApp, format: Option<&str>, path: Option<Strin
         std::borrow::Cow::Owned(d) => std::sync::Arc::new(d),
     };
     let path = target_path(app, path, f.extensions[0])?;
+    let mut again = params.clone();
+    if let Some(o) = again.as_object_mut() {
+        o.insert("format".into(), json!(f.id));
+    }
+    if let Some(r) = ask_before_losing(app, &path, "file.exportAs", &again) {
+        return Ok(r);
+    }
     // An SVG given a .svgz name is written compressed.
     let f = match fileio::format_for_name(&path) {
         Some(z) if f.id == "svg" && z.id == "svgz" => z,
diff --git a/crates/ui-egui/src/tests_save.rs b/crates/ui-egui/src/tests_save.rs
index 30b0398e9..8a39c50a4 100644
--- a/crates/ui-egui/src/tests_save.rs
+++ b/crates/ui-egui/src/tests_save.rs
@@ -166,3 +166,42 @@ fn a_document_reopens_at_its_saved_view() {
     assert!(!app.view().unwrap().fitted);
     let _ = std::fs::remove_dir_all(d);
 }
+
+#[test]
+fn replacing_a_file_that_opening_left_things_out_of_asks_first() {
+    let d = dir("lossy");
+    let path = d.join("a.vectorcraft").to_string_lossy().to_string();
+    let mut app = app();
+    app.run("file.new", json!({"width": 100, "height": 100})).unwrap();
+    rect(&mut app);
+    app.run("file.saveAs", json!({"path": path})).unwrap();
+    // As if reading the file had left out text it can't read yet.
+    let st = app.session.doc_mut().unwrap();
+    st.imported_from = Some(path.clone());
+    st.import_losses = vec!["hidden type".into()];
+    let saved = std::fs::read(&path).unwrap();
+    rect(&mut app);
+    let r = app.run("file.save", json!({})).unwrap();
+    assert_eq!(r["pending"], dialogs::confirm::KIND);
+    let dialog = app.ui.dialog.as_ref().unwrap();
+    assert!(dialog.str("detail").contains("“hidden type”"), "{:?}", dialog.fields);
+    assert_eq!(std::fs::read(&path).unwrap(), saved, "nothing is written before OK");
+    // Export As over it asks too; Cancel leaves the file.
+    app.ui.dialog = None;
+    assert_eq!(app.run("file.exportAs", json!({"path": path, "format": "svg"})).unwrap()["pending"], dialogs::confirm::KIND);
+    app.ui.dialog = None;
+    assert_eq!(std::fs::read(&path).unwrap(), saved);
+    // Another name doesn't ask.
+    let copy = d.join("b.svg").to_string_lossy().to_string();
+    assert!(app.run("file.exportAs", json!({"path": copy, "format": "svg"})).unwrap().get("pending").is_none());
+    crate::background::wait_all(&mut app);
+    assert!(app.ui.dialog.is_none());
+    // OK replaces it.
+    app.run("file.save", json!({})).unwrap();
+    press_ok(&mut app);
+    crate::background::wait_all(&mut app);
+    assert!(app.ui.dialog.is_none());
+    assert_ne!(std::fs::read(&path).unwrap(), saved);
+    assert!(!app.session.active().unwrap().is_dirty());
+    let _ = std::fs::remove_dir_all(d);
+}
diff --git a/crates/ui-egui/src/unsaved.rs b/crates/ui-egui/src/unsaved.rs
index fc8e6d171..35c52dcac 100644
--- a/crates/ui-egui/src/unsaved.rs
+++ b/crates/ui-egui/src/unsaved.rs
@@ -77,6 +77,11 @@ pub fn confirm(app: &mut VectorcraftApp) -> Result<Value, String> {
     if !d.bool("discard") {
         app.session.set_active(i);
         let r = io::save(app, vectorcraft_engine::cmd::fileio::SaveMode::Save, &json!({}), false)?;
+        // A save that asks first (replacing a file that would lose what opening it left out) keeps
+        // the document open: it closes once saved.
+        if r.get("pending").is_some() {
+            return Ok(r);
+        }
         // Closing needs the file written: wait for a background save, and stop if it failed.
         if r["background"] == true {
             crate::background::wait_all(app);