diff --git a/plugins/workbench/src/Workbench.zig b/plugins/workbench/src/Workbench.zig
index cdc7d6699..309a55a80 100644
--- a/plugins/workbench/src/Workbench.zig
+++ b/plugins/workbench/src/Workbench.zig
@@ -38,6 +38,10 @@ workspaces: std.AutoArrayHashMapUnmanaged(u64, Workspace) = .empty,
 /// plugin's own directory whenever it changes (`workbench_layout.savePanes`).
 panes: Panes,
 panes_dirty: bool = false,
+/// The person's arrangement while a demo has the window (`holdPanes`), a copy of its own, and the
+/// pane they were in: nothing is saved while it is held.
+held_panes: ?Panes = null,
+held_open: u64 = 0,
 /// Where the panes are arranged when the app arranges them instead of `panes`: each pane a view
 /// of the app's, in a place of the app's, beside another by a split of the app's (fizzy's
 /// `Workspaces`, behind `FIZZY_WORKSPACES=1`). Null: the panes are this tree's leaves, as before.
@@ -387,6 +391,18 @@ pub fn rebuildWorkspaces(self: *Workbench) !void {
     return workbench_layout.rebuildWorkspaces(self);
 }
 
+pub fn holdPanes(self: *Workbench) void {
+    workbench_layout.holdPanes(self);
+}
+
+pub fn onePane(self: *Workbench) void {
+    workbench_layout.onePane(self);
+}
+
+pub fn restorePanes(self: *Workbench) void {
+    workbench_layout.restorePanes(self);
+}
+
 pub fn forgetPanes(self: *Workbench) void {
     workbench_layout.forgetPanes(self);
 }
diff --git a/plugins/workbench/src/workbench_layout.zig b/plugins/workbench/src/workbench_layout.zig
index 55d655c74..64c398642 100644
--- a/plugins/workbench/src/workbench_layout.zig
+++ b/plugins/workbench/src/workbench_layout.zig
@@ -156,6 +156,8 @@ pub fn drawWorkspaces(wb: *Workbench, index: usize) !dvui.App.Result {
 /// no plugin directory to offer.
 fn savePanes(wb: *Workbench) void {
     wb.panes_dirty = false;
+    // A demo has the window: what it arranges is not the person's (`holdPanes`).
+    if (wb.held_panes != null) return;
     if (comptime builtin.target.cpu.arch == .wasm32) return;
     const path = panesPath(wb) orelse return;
     defer wb.allocator.free(path);
@@ -214,7 +216,11 @@ fn loadPanes(wb: *Workbench) void {
         loaded.deinit();
         return;
     }
+    adoptPanes(wb, loaded);
+}
 
+/// Make `loaded` the arrangement, every pane in it a workspace.
+fn adoptPanes(wb: *Workbench, loaded: Panes) void {
     wb.panes.deinit();
     wb.panes = loaded;
     for (wb.panes.nodes.items) |n| {
@@ -231,6 +237,41 @@ fn loadPanes(wb: *Workbench) void {
     }
 }
 
+/// Keep the person's arrangement while a demo has the window, and save nothing until it is put
+/// back (`restorePanes`): the demo's splits are not theirs. A second hold keeps the first.
+pub fn holdPanes(wb: *Workbench) void {
+    if (wb.held_panes != null) return;
+    // A copy through a snapshot: a snapshot borrows the pane names from the live tree, which the
+    // demo's first cut replaces (`onePane`).
+    const snap = wb.panes.snapshot(wb.allocator) catch return;
+    defer snap.deinit(wb.allocator);
+    wb.held_panes = Panes.fromSnapshot(wb.allocator, snap) catch return;
+    wb.held_open = wb.open_workspace_grouping;
+}
+
+/// One pane, as a demo's keyframe declares the window: the open one, the others closing with
+/// their leaves (`rebuildWorkspaces`). Its documents are the keyframe's to open.
+pub fn onePane(wb: *Workbench) void {
+    var one = Panes.init(wb.allocator);
+    one.owns_panel_ids = true;
+    one.animated = true;
+    const root = one.allocNodeForRoot() catch return;
+    var buf: [32]u8 = undefined;
+    one.insertTabOwned(root, 0, Workspace.name(&buf, wb.open_workspace_grouping)) catch {
+        one.deinit();
+        return;
+    };
+    adoptPanes(wb, one);
+}
+
+/// The person's arrangement again (`holdPanes`), and saving with it.
+pub fn restorePanes(wb: *Workbench) void {
+    const held = wb.held_panes orelse return;
+    wb.held_panes = null;
+    adoptPanes(wb, held);
+    if (wb.workspaces.contains(wb.held_open)) wb.open_workspace_grouping = wb.held_open;
+}
+
 /// Delete the saved arrangement: the app has taken it over (`Workbench.places`).
 pub fn forgetPanes(wb: *Workbench) void {
     if (comptime builtin.target.cpu.arch == .wasm32) return;
diff --git a/src/editor/Demo.zig b/src/editor/Demo.zig
index d1267a4b4..28907fd6b 100644
--- a/src/editor/Demo.zig
+++ b/src/editor/Demo.zig
@@ -460,6 +460,8 @@ fn begin(ctx: *anyopaque, _: *const automation.Tape) void {
     editor.flushLayout();
     editor.flushSettings();
     self.saveSettings();
+    // The document panes too: kept in memory, and none of the demo's saved over them.
+    editor.workbench.holdPanes();
 
     const gpa = editor.app.gpa;
     var docs: std.ArrayList(Saved.Doc) = .empty;
@@ -497,11 +499,14 @@ fn end(ctx: *anyopaque) void {
     if (self.quitting) {
         self.freeSaved();
         self.freeSavedSettings();
+        editor.workbench.restorePanes();
         return;
     }
     self.restoreSettings();
     self.closeAllDocuments();
     self.unmountFiles();
+    // Before the person's documents reopen: into the pane they were in.
+    editor.workbench.restorePanes();
 
     // The layout as the user left it: `begin` flushed it, and nothing has been written since.
     editor.app.layout.resetLayout(gpa);
@@ -568,6 +573,8 @@ fn keyframe(ctx: *anyopaque, kf: *const automation.Tape.Keyframe) void {
 
     editor.command_palette.finishClose();
     self.closeAllDocuments();
+    // One pane: a split a later moment made is gone at a cut, as on the first pass.
+    editor.workbench.onePane();
     self.applySettings(kf.settings);
 
     // Fresh bytes every time: a replay must not see what the last pass typed or saved.
diff --git a/src/editor/Editor.zig b/src/editor/Editor.zig
index 3cb74eee2..4490214b9 100644
--- a/src/editor/Editor.zig
+++ b/src/editor/Editor.zig
@@ -4471,8 +4471,8 @@ pub fn tick(editor: *Editor) !dvui.App.Result {
     {
         const t = fizzy.core.hitch.begin(.rebuild_workspaces);
         defer t.end();
-        editor.rebuildWorkspaces() catch {
-            dvui.log.err("Failed to rebuild workspaces", .{});
+        editor.rebuildWorkspaces() catch |err| {
+            dvui.log.err("Failed to rebuild workspaces: {t}", .{err});
         };
         // The first rebuild reopened last session's tabs; what the session held beyond them is
         // kept in recovery files. A frame on, the panes have drawn, and each shows the tab it did.
diff --git a/tests/demos.zig b/tests/demos.zig
index e06c28986..abb7d575a 100644
--- a/tests/demos.zig
+++ b/tests/demos.zig
@@ -185,6 +185,29 @@ test "demo: every bundled demo plays to the end through fizzy's stage, a seek la
     while (p.state == .seeking and frames < 400) : (frames += 1) _ = try dvui.testing.step(headlessFrame);
     try std.testing.expect(p.seq.now >= @as(f64, @floatFromInt(second)));
 
+    // A demo's panes are its own: a cut is one pane again, and the end gives back the person's.
+    {
+        const wb = &app.editor.workbench;
+        p.unload();
+        try dvui.testing.settle(headlessFrame);
+        const panes_before = wb.workspaces.count();
+        const split = try splitDemo();
+        defer gpa.free(split);
+        try app.editor.demo.playTape(split);
+        frames = 0;
+        while (p.state != .ended and frames < 2_000) : (frames += 1) _ = try dvui.testing.step(headlessFrame);
+        try std.testing.expectEqual(@as(u32, 0), p.timeouts);
+        try std.testing.expectEqual(@as(usize, 2), wb.workspaces.count());
+        p.seek(0);
+        frames = 0;
+        while ((p.state == .seeking or wb.workspaces.count() != 1) and frames < 400) : (frames += 1) _ = try dvui.testing.step(headlessFrame);
+        try std.testing.expectEqual(@as(usize, 1), wb.workspaces.count());
+        p.unload();
+        try dvui.testing.settle(headlessFrame);
+        try std.testing.expectEqual(panes_before, wb.workspaces.count());
+        try std.testing.expect(wb.held_panes == null);
+    }
+
     // A tape loaded some other way is not the one the service started.
     try app.editor.demo.play("markdown");
     try std.testing.expectEqual(@as(?[]const u8, null), api.current());
@@ -220,6 +243,23 @@ fn openZipFromBytes(editor: *fizzy.Editor, name: []const u8, files: []const stru
     return gpa.dupe(u8, folder);
 }
 
+/// A demo that drags its second tab onto the editor's right edge, opening a pane beside, encoded.
+fn splitDemo() ![]u8 {
+    const gpa = std.testing.allocator;
+    var s: automation.Script = .init(gpa, "split", "Split");
+    errdefer s.deinit();
+    try s.keyframe(.{
+        .root = "demo://split",
+        .files = &.{ .{ .path = "a.md", .text = "# A\n" }, .{ .path = "b.md", .text = "# B\n" } },
+        .open = &.{ "a.md", "b.md" },
+    });
+    try s.drag(.{ .tag = "workbench.tab:demo://split/b.md" }, .{ .tag = "region:Main", .dx = 132 }, .{});
+    s.pause(600);
+    var owned = try s.finish();
+    defer owned.deinit();
+    return automation.binary.encode(gpa, owned.tape, .{});
+}
+
 /// A tape a plugin might register, encoded: a demo opening on a keyframe of one file, in two
 /// chapters, or (`demo` false) a live tape of the same pauses, which a demo list leaves out.
 fn encodedDemo(name: []const u8, demo: bool) ![]u8 {