Fix #577: the gradient stop popover stays open after the click that opens it

The Gradient panel's colour chip opens the stop popover on a click. The
popover closes on a click elsewhere, and the opening click itself, which
is released in the frame the popover first draws and lies outside it,
counted as one: the popover closed at once (a double-click got through,
as the popover lets the double-click that opens it from the canvas pass).

The popover now records the frame it first drew in and only a click in a
later frame closes it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

ROADMAP.md

@@ -4,7 +4,7 @@ VectorCraft is a clean-room, open-source, pure-Rust reimplementation of the Adob
 
 This file tracks **how far we are and what's left**. Time estimates are wall-clock hours of continuous Claude Opus 5.5 agent work (including builds and the CI gate), given both for **one agent** and for **4–6 parallel agents** on disjoint crates. They are counted from the remaining work (see [Parity estimate](#parity-estimate)), calibrated against measured throughput, and updated as work lands.
 
-_Last updated: 2026-10-09 (after placed documents (File › Place of a `.vectorcraft` file, linked), M4.14–M4.98, M8.1–M8.20, M14.4–M14.7, the MCP prompts, resource templates, completions and logging, the 2026-10-07 issue fixes, the Layers panel rework and the 2026-10-08 community contributions: Pen and shape-tool modifiers, path editing, Layers, Artboards, Swatches/Brushes and dialogs, Japanese composition and PDF text, Hebrew/Arabic type, interface languages (Spanish among them), the font menu, saved selections, MCP and EPS, the missing-font export warning (#319), open paths in the Shape Builder (#374), PDF/`.ai` import keeping strokes live and hidden and nested layers (#372), per-corner Live Corners (#381), SVG type opening at the size it draws at (#396), the Wayland clipboard with copied-file paste (#398), ruler guides that can be selected, moved and deleted (#414), two batches of Preferences options that were stored but unused (#394), skeleton reads with `document.find` for large documents over MCP (#416) and anchors dragged with Direct Selection snapping to points, segments and smart guides, clipped SVG layers opening as clipping layers (#420), PDF/`.ai` layers read on pages of tens of millions of operators (#419), Document Color Mode putting RGB greys on the black plate on request and converting pattern tiles (#421) and movable dialogs with Offset Path's Joins dropdown (#423) and numeric fields scrubbed by dragging their label (#400), stroke weight presets in the stroke unit (#426), the Appearance panel's Opacity popup (#430), type on a path brackets, flip and Type on a Path Options that keep the type in place (#429), Layers rows dragged with a ghost and dropped on the trash or New Layer (#435), tool flyouts opening on a right or corner press (#436), tool flyouts torn off into floating toolbars (#437), the Shape Builder's erase mode deleting edges too (#439), installed fonts registered outside the font folders and fonts installed while the app runs listed in the font menus (#443), alike circular corners on rectangles that aren't square (#442), tool cursors as OS cursors so the pointer no longer trails over the canvas (#444), artboards copied and pasted with their art (#446), guides dragged out of the rulers snapping to the art's side midpoints and the artboards, artboard guides (#451), the toolbar's double arrow and Window › Toolbars › Double Column switching between one and two columns in any window height (#455), the Smart Guides display options and Snapping Tolerance (#394), Font Size and Leading combo boxes with preset lists in the Character and Properties panels and the Control bar (#458), screenshots pasted from the clipboard on macOS, Windows and the web (#457), the Properties panel's Fill and Stroke matching the Control bar's, Illustrator's Window menu panel keys (Shift+F7 for Align…) and Alt-wheel zoom whatever the wheel preference (Discord feedback), the point/area type widget (Discord feedback), groups in legacy Illustrator .ai files (Discord feedback), a rotating desktop log file (#465), image controls in the Control bar and Properties panel: Image Trace with its presets, Mask, Crop Image, Embed/Unembed, and an Image Trace object's preset, Expand and Release (Discord feedback), the Pen working as the Anchor Point tool with Alt held over a selected path's handles and anchors, and anchor buttons that convert, connect and cut paths at the selected anchors (Discord feedback), Japanese hanging punctuation (burasagari, #463), Escape leaving Presentation Mode with no screen mode saved across restarts, documents dropped on the desktop app opening as tabs of their own and a note that an `.ai` file's art off its artboards isn't in the part read (#472), Add/Delete Anchor Point tool icons drawn from the Pen tool's (#479), EPS import running more of PostScript Level 3 (patterns, Type 3 fonts, mesh shadings, masked images, VM and resource probes), and a preview that stands in saying why (Discord feedback, #466, #469, #474), chords with modifiers recorded in Edit › Keyboard Shortcuts (#487), Type Object Selection by Path Only (#394), Anti-aliased Artwork (#394), Show Pixel Grid (#394), pen and touch taps pressed and lifted within one frame clicking where they tapped and the Linux/Wayland pen-tablet workaround (#491), bounding-box resizes landing on the other objects' anchors and centres with labels, and the Rotate, Scale, Shear and Reflect tools snapping their drags (#482), Shift-drag marquees that toggle the objects or anchors they reach and a Lasso whose Alt subtraction keeps the rest of the selection (#483), the mouse wheel stepping the focused numeric field, the dialogs' and preferences' drag values made such fields (#485), Show The Home Screen When No Documents Are Open (#394), Numbers Without Units Are Points (#394), Auto-Collapse Iconic Panels (#394), the Contextual Task Bar moved by its handle and its More Options menu pinning and resetting its position, a designed macOS DMG windoLine truncated
+_Last updated: 2026-10-09 (after placed documents (File › Place of a `.vectorcraft` file, linked), M4.14–M4.98, M8.1–M8.20, M14.4–M14.7, the MCP prompts, resource templates, completions and logging, the 2026-10-07 issue fixes, the Layers panel rework and the 2026-10-08 community contributions: Pen and shape-tool modifiers, path editing, Layers, Artboards, Swatches/Brushes and dialogs, Japanese composition and PDF text, Hebrew/Arabic type, interface languages (Spanish among them), the font menu, saved selections, MCP and EPS, the missing-font export warning (#319), open paths in the Shape Builder (#374), PDF/`.ai` import keeping strokes live and hidden and nested layers (#372), per-corner Live Corners (#381), SVG type opening at the size it draws at (#396), the Wayland clipboard with copied-file paste (#398), ruler guides that can be selected, moved and deleted (#414), two batches of Preferences options that were stored but unused (#394), skeleton reads with `document.find` for large documents over MCP (#416) and anchors dragged with Direct Selection snapping to points, segments and smart guides, clipped SVG layers opening as clipping layers (#420), PDF/`.ai` layers read on pages of tens of millions of operators (#419), Document Color Mode putting RGB greys on the black plate on request and converting pattern tiles (#421) and movable dialogs with Offset Path's Joins dropdown (#423) and numeric fields scrubbed by dragging their label (#400), stroke weight presets in the stroke unit (#426), the Appearance panel's Opacity popup (#430), type on a path brackets, flip and Type on a Path Options that keep the type in place (#429), Layers rows dragged with a ghost and dropped on the trash or New Layer (#435), tool flyouts opening on a right or corner press (#436), tool flyouts torn off into floating toolbars (#437), the Shape Builder's erase mode deleting edges too (#439), installed fonts registered outside the font folders and fonts installed while the app runs listed in the font menus (#443), alike circular corners on rectangles that aren't square (#442), tool cursors as OS cursors so the pointer no longer trails over the canvas (#444), artboards copied and pasted with their art (#446), guides dragged out of the rulers snapping to the art's side midpoints and the artboards, artboard guides (#451), the toolbar's double arrow and Window › Toolbars › Double Column switching between one and two columns in any window height (#455), the Smart Guides display options and Snapping Tolerance (#394), Font Size and Leading combo boxes with preset lists in the Character and Properties panels and the Control bar (#458), screenshots pasted from the clipboard on macOS, Windows and the web (#457), the Properties panel's Fill and Stroke matching the Control bar's, Illustrator's Window menu panel keys (Shift+F7 for Align…) and Alt-wheel zoom whatever the wheel preference (Discord feedback), the point/area type widget (Discord feedback), groups in legacy Illustrator .ai files (Discord feedback), a rotating desktop log file (#465), image controls in the Control bar and Properties panel: Image Trace with its presets, Mask, Crop Image, Embed/Unembed, and an Image Trace object's preset, Expand and Release (Discord feedback), the Pen working as the Anchor Point tool with Alt held over a selected path's handles and anchors, and anchor buttons that convert, connect and cut paths at the selected anchors (Discord feedback), Japanese hanging punctuation (burasagari, #463), Escape leaving Presentation Mode with no screen mode saved across restarts, documents dropped on the desktop app opening as tabs of their own and a note that an `.ai` file's art off its artboards isn't in the part read (#472), Add/Delete Anchor Point tool icons drawn from the Pen tool's (#479), EPS import running more of PostScript Level 3 (patterns, Type 3 fonts, mesh shadings, masked images, VM and resource probes), and a preview that stands in saying why (Discord feedback, #466, #469, #474), chords with modifiers recorded in Edit › Keyboard Shortcuts (#487), Type Object Selection by Path Only (#394), Anti-aliased Artwork (#394), Show Pixel Grid (#394), pen and touch taps pressed and lifted within one frame clicking where they tapped and the Linux/Wayland pen-tablet workaround (#491), bounding-box resizes landing on the other objects' anchors and centres with labels, and the Rotate, Scale, Shear and Reflect tools snapping their drags (#482), Shift-drag marquees that toggle the objects or anchors they reach and a Lasso whose Alt subtraction keeps the rest of the selection (#483), the mouse wheel stepping the focused numeric field, the dialogs' and preferences' drag values made such fields (#485), Show The Home Screen When No Documents Are Open (#394), Numbers Without Units Are Points (#394), Auto-Collapse Iconic Panels (#394), the Contextual Task Bar moved by its handle and its More Options menu pinning and resetting its position, a designed macOS DMG windoLine truncated
 
 ## Where we are
 

crates/engine/src/cmd/fileio/encode.rs

@@ -417,6 +417,12 @@ fn encode_files(doc: &Document, f: &Format, p: &Value) -> Result<Encoded> {
         "txt" => super::text::encode(doc, p)?,
         "svg" | "svgz" => return super::svg::encode(doc, p, f.id == "svgz").map_err(|e| bad(C, e)),
         "dxf" => return super::dxf::encode(doc, p, use_artboards),
+        // As Save As writes it (a PDF of every artboard carrying the native document).
+        "ai" => {
+            let mut q = p.clone();
+            super::save::ai_params(&mut q);
+            return super::save::encode_ai(C, f, doc, &q);
+        }
         // EPS reads its own `useArtboards` (the art's bounds unless asked).
         "eps" => return super::eps::encode(doc, p),
         "emf" => return super::metafile::encode(doc, p, use_artboards, vectorcraft_metafile::Kind::Emf),

crates/engine/src/cmd/fileio/mod.rs

@@ -465,8 +465,8 @@ pub const FORMATS: &[Format] = &[
         extensions: &["ai"],
         mime: "application/pdf",
         read: true,
-        // Saved (Save As), not exported.
-        write: false,
+        // Save As writes it; exports write the same file.
+        write: true,
         raster: false,
         options: native::AI_OPTIONS,
     },

crates/engine/src/cmd/fileio/save.rs

@@ -305,6 +305,35 @@ fn blank_pages(doc: &Document) -> Document {
 /// Why a `.ai` file saved without PDF content looks empty elsewhere.
 const NOT_PDF_COMPATIBLE: &str = "saved without PDF content: VectorCraft opens it as before, other apps show empty pages";
 
+/// The encoder's params for a `.ai` file, from a save's or an export's: a PDF of every artboard
+/// with the PDF options, always carrying the native document; Use Compression compresses the
+/// PDF's content.
+pub(super) fn ai_params(params: &mut Value) {
+    let Some(o) = params.as_object_mut() else { return };
+    o.extend([("preserveEditing".into(), json!(true)), ("range".into(), json!("all"))]);
+    if let Some(c) = o.get("compress").and_then(Value::as_bool) {
+        let compression = o.entry("compression").or_insert_with(|| json!({}));
+        if let Some(m) = compression.as_object_mut() {
+            m.insert("compressText".into(), json!(c));
+        }
+    }
+}
+
+/// Encode `doc` as a PDF-compatible `.ai` file (`params` as [`ai_params`] makes them) for command
+/// `cmd`: its pages (blank with `pdfCompatible: false`, which it then notes), carrying the native
+/// document. File › Save As writes it, and so do the exports (`document.export`, the CLI).
+pub(super) fn encode_ai(cmd: &str, f: &Format, doc: &Document, params: &Value) -> Result<Encoded> {
+    let compatible = bool_or(params, "pdfCompatible", true);
+    let pages = doc.without_edit_modes();
+    let pages = if compatible { pages } else { std::borrow::Cow::Owned(blank_pages(&pages)) };
+    let native = || super::native::ai_native(cmd, f, doc, params);
+    let (bytes, mut warnings) = super::pdf::encode_carrying(cmd, &pages, params, native)?;
+    if !compatible {
+        warnings.insert(0, NOT_PDF_COMPATIBLE.to_string());
+    }
+    Ok(Encoded { warnings, ..Encoded::one(bytes) })
+}
+
 /// Snapshot the active document for `plan` (stamping File Info's dates when the file becomes the
 /// document's own). Bad options fail here, before anything is encoded.
 pub fn save_job(s: &mut Session, plan: SavePlan) -> Result<SaveJob> {
@@ -339,16 +368,8 @@ pub(crate) fn job_for(s: &Session, st: &DocState, plan: SavePlan) -> Result<Save
     }
     let boards = separate_boards(cmd, plan.format, &doc, &params)?;
     let mut params = super::pdf::expand_preset(s, cmd, &params)?.into_owned();
-    if let (Some(o), "ai") = (params.as_object_mut(), plan.format.id) {
-        // A PDF of every artboard with the PDF options, always carrying the native document.
-        o.extend([("preserveEditing".into(), json!(true)), ("range".into(), json!("all"))]);
-        // Use Compression compresses the PDF's content.
-        if let Some(c) = o.get("compress").and_then(Value::as_bool) {
-            let compression = o.entry("compression").or_insert_with(|| json!({}));
-            if let Some(m) = compression.as_object_mut() {
-                m.insert("compressText".into(), json!(c));
-            }
-        }
+    if plan.format.id == "ai" {
+        ai_params(&mut params);
     }
     Ok(SaveJob { plan, doc, params, snapshot: st.doc.clone(), boards })
 }
@@ -372,25 +393,14 @@ impl SaveJob {
             let one = self.encode_one(&artboard_doc(&self.doc, b))?;
             enc.files.extend(one.files.into_iter().map(|(_, bytes)| (Some(b), bytes)));
         }
-        let pdf_less = self.plan.format.id == "ai" && !bool_or(&self.params, "pdfCompatible", true);
-        let notes = fidelity_warning(self.plan.format).into_iter().chain(pdf_less.then(|| NOT_PDF_COMPATIBLE.to_string()));
-        enc.warnings.splice(0..0, notes);
+        enc.warnings.splice(0..0, fidelity_warning(self.plan.format));
         Ok(enc)
     }
 
     /// Encode one file of `doc` in the job's format.
     fn encode_one(&self, doc: &Document) -> Result<Encoded> {
         let (cmd, f) = (self.plan.mode.command(), self.plan.format);
-        let enc = if f.id == "ai" {
-            // The pages (blank without PDF content), carrying the native document.
-            let pages = doc.without_edit_modes();
-            let pages = if bool_or(&self.params, "pdfCompatible", true) { pages } else { std::borrow::Cow::Owned(blank_pages(&pages)) };
-            let native = || super::native::ai_native(cmd, f, doc, &self.params);
-            let (bytes, warnings) = super::pdf::encode_carrying(cmd, &pages, &self.params, native)?;
-            Encoded { warnings, ..Encoded::one(bytes) }
-        } else {
-            encode_all(doc, f.id, &self.params)?
-        };
+        let enc = if f.id == "ai" { encode_ai(cmd, f, doc, &self.params)? } else { encode_all(doc, f.id, &self.params)? };
         if enc.files.len() != 1 {
             return Err(bad(cmd, "Save writes one artboard: name one, or export several with document.export"));
         }

crates/engine/src/cmd/fileio/screens.rs

@@ -161,7 +161,7 @@ impl Row {
             return Err(bad(C, "each format is an object {format, scale?, suffix?}"));
         }
         let format = writable(C, Some(str_param(row, "format").unwrap_or("png")), None)?;
-        if matches!(format.id, "vectorcraft" | "template" | "txt" | "dxf" | "eps" | "emf" | "wmf") {
+        if matches!(format.id, "vectorcraft" | "template" | "ai" | "txt" | "dxf" | "eps" | "emf" | "wmf") {
             return Err(bad(C, "Export for Screens writes png, png8, jpg, webp, gif, svg, svgz or pdf"));
         }
         // Vector formats have no pixel size: it doesn't apply and adds no @2x suffix (not even one

crates/engine/src/cmd/fileio/tests.rs

@@ -173,6 +173,7 @@ fn export_extensions_name_every_writable_format() {
             "svg",
             "svgz",
             "pdf",
+            "ai",
             "png",
             "jpg",
             "gif",
@@ -206,6 +207,7 @@ fn formats_query_lists_readers_writers_and_options() {
             "svg",
             "svgz",
             "pdf",
+            "ai",
             "png",
             "jpg",
             "gif",

crates/engine/src/cmd/fileio/tests_pdfedit.rs

@@ -118,6 +118,27 @@ fn ai_files_are_pdfs_that_save_and_reopen_editable() {
     assert_eq!(s.doc().unwrap().path, None);
 }
 
+/// #526: the exports (`document.export`, the CLI's `--export` and `convert`) write `.ai` as Save
+/// As does, leaving the document's own path alone.
+#[test]
+fn exports_write_ai_as_save_as_does() {
+    let mut s = rich();
+    let before = comparable(&s.doc().unwrap().doc);
+    let path = tmp("exported.ai");
+    let r = s.execute("document.export", &json!({"path": path})).unwrap();
+    assert_eq!(r["format"], "ai", "{r}");
+    let bytes = std::fs::read(&path).unwrap();
+    assert!(bytes.starts_with(b"%PDF") && vectorcraft_pdf::editing(&bytes).is_some_and(|e| e.intact), "PDF-compatible, carrying the document");
+    assert_eq!(s.doc().unwrap().path, None, "an export doesn't give the document a path");
+    let r = s.execute("document.open", &json!({"path": path})).unwrap();
+    assert_eq!((&r["format"], &r["restored"]), (&json!("ai"), &json!(true)), "{r}");
+    assert_eq!(comparable(&s.doc().unwrap().doc), before);
+    // Its options as Save As takes them; no path gives the bytes.
+    let r = s.execute("document.export", &json!({"format": "ai", "pdfCompatible": false})).unwrap();
+    assert!(r["warnings"].as_array().unwrap().iter().any(|w| w.as_str().is_some_and(|w| w.contains("without PDF content"))), "{r}");
+    assert!(b64(&r).starts_with(b"%PDF"));
+}
+
 #[test]
 fn ait_templates_open_their_document_untitled() {
     let mut s = rich();

crates/mcp/src/tests_fileio.rs

@@ -62,6 +62,7 @@ fn export_tool_lists_engine_formats_and_options() {
             "svg",
             "svgz",
             "pdf",
+            "ai",
             "png",
             "jpg",
             "gif",

crates/ui-egui/src/dialogs/export_as.rs

@@ -17,8 +17,9 @@ use crate::{VectorcraftApp, io, widgets};
 pub(super) const SPEC: DialogSpec =
     DialogSpec { heading: |_| tl!("Export As").into(), body, confirm, ok: Some("Export…"), min_width: 380.0, ..DialogSpec::FORM };
 
-/// The formats Export As writes (the native format is Save's).
-static FORMATS: LazyLock<Vec<&'static Format>> = LazyLock::new(|| fileio::FORMATS.iter().filter(|f| f.write && f.id != "vectorcraft").collect());
+/// The formats Export As writes (the native format and `.ai` are Save As's).
+static FORMATS: LazyLock<Vec<&'static Format>> =
+    LazyLock::new(|| fileio::FORMATS.iter().filter(|f| f.write && !matches!(f.id, "vectorcraft" | "ai")).collect());
 /// Formats listed after them that can't be written (`fileio::unsupported` ids), greyed out.
 const UNAVAILABLE: [(&str, &str); 1] = [("dwg", "DWG (use DXF)")];
 static LABELS: LazyLock<Vec<&'static str>> = LazyLock::new(|| FORMATS.iter().map(|f| f.label).chain(UNAVAILABLE.iter().map(|u| u.1)).collect());

crates/ui-egui/src/dialogs/gradient_stop.rs

@@ -29,6 +29,9 @@ use crate::widgets::{self, Live};
 
 pub(super) const SPEC: DialogSpec = DialogSpec::window(show, confirm);
 
+/// The field holding the frame the popover was first drawn in.
+const OPENED: &str = "__opened";
+
 /// What the popover edits: the selected stop of the gradient behind the active proxy (with all
 /// its stops), or the selected point of a freeform gradient.
 enum Target {
@@ -131,12 +134,18 @@ fn show(app: &mut VectorcraftApp, ctx: &egui::Context) {
             });
         })
         .response;
-    if let (Some(tab), Some(d)) = (tab, app.ui.dialog.as_mut()) {
-        d.fields.insert("tab".into(), json!(tab));
+    // The frame it opened in (its first drawn).
+    let frame = ctx.cumulative_frame_nr();
+    let opened = d.fields.get(OPENED).and_then(Value::as_u64).unwrap_or(frame);
+    if let Some(d) = app.ui.dialog.as_mut() {
+        if let Some(tab) = tab {
+            d.fields.insert("tab".into(), json!(tab));
+        }
+        d.fields.insert(OPENED.into(), json!(opened));
     }
-    // The double-click that opened the popover lands on its chip, outside it: only a later click
-    // elsewhere closes it.
-    if resp.clicked_elsewhere() && !ctx.input(|i| i.pointer.button_double_clicked(egui::PointerButton::Primary)) {
+    // The click that opened the popover (the Gradient panel's colour chip) or the double-click
+    // (a stop's chip) lands outside it: only a later click elsewhere closes it (#577).
+    if frame > opened && resp.clicked_elsewhere() && !ctx.input(|i| i.pointer.button_double_clicked(egui::PointerButton::Primary)) {
         app.ui.dialog = None;
     }
 }
@@ -246,10 +255,18 @@ mod tests {
         }
     }
 
+    thread_local! {
+        // One context per test, so frames follow one another as in the app.
+        static CTX: egui::Context = {
+            let ctx = egui::Context::default();
+            crate::theme::install_fonts(&ctx);
+            ctx
+        };
+    }
+
     /// One headless frame of the dialog layer and the shortcuts.
     fn frame(app: &mut VectorcraftApp, events: Vec<egui::Event>) {
-        let ctx = egui::Context::default();
-        crate::theme::install_fonts(&ctx);
+        let ctx = CTX.with(Clone::clone);
         let mut out = ctx.run_ui(egui::RawInput { events, ..Default::default() }, |ui| {
             crate::shortcuts::handle(app, ui.ctx());
             super::super::show(app, ui.ctx());
@@ -312,6 +329,25 @@ mod tests {
         assert!(app.ui.dialog.is_none(), "a click elsewhere closes it");
     }
 
+    /// #577: the Gradient panel's colour chip opens it with a click whose release lands in the
+    /// frame it opens in, outside it: that click doesn't close it.
+    #[test]
+    fn the_click_that_opens_it_from_the_panel_keeps_it_open() {
+        let mut app = app();
+        let at = egui::pos2(5.0, 5.0);
+        frame(&mut app, vec![egui::Event::PointerMoved(at), click(at, true)]);
+        // The panel opens it while the click is released.
+        app.ui.dialog = Some(Dialog::new("gradientStop", json!({"index": 1, "screen": [200.0, 200.0], "tab": "color"})));
+        frame(&mut app, vec![click(at, false)]);
+        for _ in 0..3 {
+            frame(&mut app, vec![]);
+        }
+        assert!(app.ui.dialog.is_some(), "the opening click must not close it");
+        let away = egui::pos2(5.0, 600.0);
+        frame(&mut app, vec![egui::Event::PointerMoved(away), click(away, true), click(away, false)]);
+        assert!(app.ui.dialog.is_none(), "a later click elsewhere closes it");
+    }
+
     #[test]
     fn the_popover_closes_when_its_stop_goes_away() {
         let mut app = app();

docs/mcp.md

@@ -423,6 +423,8 @@ document exactly (`restored: true`); when another app changed the pages, or the
 imported instead and the first warning says why. Choosing a standard turns it off (PDF/A refuses it). Save to a `.ai`
 path (`document.save {path: "art.ai"}` or `{format: "ai"}`) writes a PDF-compatible file that always carries the
 document, takes the PDF options and keeps its path when reopened, so Save writes `.ai` again; a `.ait` opens untitled.
+`document.export` / `serialize` to `.ai` (and the CLI's `run --export x.ai` and `convert in.svg out.ai`) write the same file
+without giving the document a path.
 
 Drive a tool like a mouse: