diff --git a/src/app/update/file.rs b/src/app/update/file.rs
index 2f71266a..62a76667 100644
--- a/src/app/update/file.rs
+++ b/src/app/update/file.rs
@@ -2096,7 +2096,22 @@ pub(super) fn on_open_file(&mut self) -> Task<Message> {
     /// save-before-close flow — the version picker is reserved for Save As.
     pub(in crate::app) fn save_with_default_format(&mut self, tab_idx: usize) -> Task<Message> {
         self.active_tab = tab_idx;
-        self.save_dialog_format = if self.tabs[tab_idx].recovery_save_as_required {
+        // CMMS embedding fix (upstream bug, not introduced by CMMS patches -
+        // real live data corruption caught 2026-08-23): on native, plain
+        // Save on an already-loaded document takes an early-return path in
+        // on_save_file() that preserves scene.document.version, never
+        // reaching this function at all. Web has no equivalent early
+        // return - EVERY web Save (not just recovery/never-saved-yet ones)
+        // used to fall straight to `else { self.default_save_format }`
+        // below, silently re-serializing a loaded DXF as DWG 2018 (the
+        // hardcoded default) under its original .dxf filename. Extending
+        // the same format-preservation branch recovery already uses to
+        // cover "this document has a known current_path" (i.e. it's not
+        // actually a fresh, never-saved drawing) fixes both cases with the
+        // same logic.
+        let preserve_format = self.tabs[tab_idx].recovery_save_as_required
+            || self.tabs[tab_idx].current_path.is_some();
+        self.save_dialog_format = if preserve_format {
             let document = &self.tabs[tab_idx].scene.document;
             let is_dxf = crate::io::source_is_dxf(
                 self.tabs[tab_idx].current_path.as_deref(),
diff --git a/src/sys.rs b/src/sys.rs
index 18faf21a..c9ada909 100644
--- a/src/sys.rs
+++ b/src/sys.rs
@@ -509,10 +509,16 @@ pub async fn post_stl_export_to_host(bytes: &[u8], filename: &str) -> Result<(),
         percent_encode(entity_type),
         percent_encode(entity_id)
     );
+    // Open in a new tab/window rather than navigating this one away. A
+    // full top-level navigation of the CAD editor's own tab (the original
+    // set_href approach) tears down its WASM/GPU/worker context - even
+    // "going back" afterward doesn't reliably restore it, and a user who
+    // then hits Save on the broken restored state would silently overwrite
+    // the real file with whatever the broken state actually held. Opening
+    // a new tab leaves this one completely untouched.
     window
-        .location()
-        .set_href(&url)
-        .map_err(|_| "navigation to the CAM page failed")?;
+        .open_with_url_and_target(&url, "_blank")
+        .map_err(|_| "opening the CAM page failed")?;
     Ok(())
 }