diff --git a/apps/ely-show/src/deck.rs b/apps/ely-show/src/deck.rs
index 2a41547..b8355b3 100644
--- a/apps/ely-show/src/deck.rs
+++ b/apps/ely-show/src/deck.rs
@@ -1,16 +1,15 @@
 //! ElyShow's window: decks over one LOK worker (§10.1).
 
 use std::{
-    collections::{HashMap, HashSet},
+    collections::HashSet,
     path::PathBuf,
     sync::{Arc, Mutex},
 };
 
 use ely_gpui_component::{feedback::EmptyState, primitives::IconName, shell::StatusBar};
 use ely_lok::{
-    LokView, Sheets, Worker,
-    history::Step,
-    show::{Design, Objects},
+    LokView, Worker,
+    show::Design,
 };
 use ely_office::{Core, Kind, prelude::*};
 use ely_platform::AppId;
@@ -18,61 +17,13 @@ use ely_ui::{Root, Shell, commands};
 use gpui::prelude::FluentBuilder as _;
 use gpui::{
     AnyElement, App, AppContext as _, Context, Entity, InteractiveElement as _, IntoElement,
-    ParentElement as _, Render, RenderImage, SharedString, Styled as _, Window, div,
+    ParentElement as _, Render, SharedString, Styled as _, Window, div,
 };
 
 use crate::design::Panel;
 use crate::slides::Strip;
 
-/// Parts, edits, caret and selected frame.
-pub type Seen = (u64, u64, bool, Option<ely_lok::Rect>);
-
-/// What ElyShow keeps per deck.
-#[derive(Default)]
-pub struct Extra {
-    pub slides: Sheets,
-    /// The document as the last read saw it.
-    pub read_at: Option<ely_lok::Doc>,
-    /// What the view showed at the last read.
-    pub read: Option<Seen>,
-    pub reading: bool,
-    pub design: Option<Design>,
-    pub objects: Option<Objects>,
-    pub notes: Option<ely_lok::show::Notes>,
-    pub remarks: Vec<ely_lok::show::Remark>,
-    /// The shown slide's transition and effects; none on a master.
-    pub motion: Option<(ely_lok::show::Transition, Vec<ely_lok::show::Effect>)>,
-    pub media: Vec<ely_lok::show::Media>,
-    /// Counts completed reads.
-    pub reads: u64,
-    /// The slide size in twips.
-    pub size: (i64, i64),
-    /// Undo and redo lists at the last read.
-    pub history: Option<(Vec<Step>, Vec<Step>)>,
-    /// A size sent, in 1/100 mm, until read back.
-    pub size_asked: Option<(i64, i64)>,
-    /// A transition sent for a slide, until read back.
-    pub transition_asked: Option<(String, ely_lok::show::Transition, u64)>,
-    /// Pictures by slide name; stale ones show until repainted.
-    pub thumbs: HashMap<String, Arc<RenderImage>>,
-    pub retired: ely_gpui_component::primitives::Retired,
-    pub stale: HashSet<String>,
-    /// Pictures that failed; retried after the next read.
-    pub failed: HashSet<String>,
-    pub painting: bool,
-    /// The parts are masters.
-    pub masters: bool,
-    /// The scheme the pictures were painted with.
-    pub dark: Option<bool>,
-}
-
-impl Extra {
-    /// The size to show, in 1/100 mm: asked, else read.
-    pub fn shown_size(&self) -> (i64, i64) {
-        self.size_asked
-            .unwrap_or_else(|| crate::design::mm100(self.size))
-    }
-}
+pub use crate::extra::Extra;
 
 pub struct Deck {
     pub core: Core<Deck>,
@@ -137,7 +88,13 @@ impl Host for Deck {
     }
 
     fn observed(&mut self, id: u64, view: &Entity<LokView>, cx: &mut Context<Self>) {
-        view.update(cx, |view, cx| view.fit_page(cx));
+        // A new deck fits once; a zoom then stays.
+        if let Some(tab) = self.tab_mut(id)
+            && !tab.extra.fitted
+        {
+            tab.extra.fitted = true;
+            view.update(cx, |view, cx| view.fit_page(cx));
+        }
         // Pictures follow the kernel's light or dark scheme.
         let dark = view.read(cx).dark();
         if let Some(tab) = self.tab_mut(id)
diff --git a/apps/ely-show/src/extra.rs b/apps/ely-show/src/extra.rs
new file mode 100644
index 0000000..1836c7b
--- /dev/null
+++ b/apps/ely-show/src/extra.rs
@@ -0,0 +1,65 @@
+//! What ElyShow keeps per deck.
+
+use std::{
+    collections::{HashMap, HashSet},
+    sync::Arc,
+};
+
+use ely_lok::{
+    Sheets,
+    history::Step,
+    show::{Design, Objects},
+};
+use gpui::RenderImage;
+
+/// Parts, edits, caret and selected frame.
+pub type Seen = (u64, u64, bool, Option<ely_lok::Rect>);
+
+/// What ElyShow keeps per deck.
+#[derive(Default)]
+pub struct Extra {
+    pub slides: Sheets,
+    /// The document as the last read saw it.
+    pub read_at: Option<ely_lok::Doc>,
+    /// What the view showed at the last read.
+    pub read: Option<Seen>,
+    pub reading: bool,
+    pub design: Option<Design>,
+    pub objects: Option<Objects>,
+    pub notes: Option<ely_lok::show::Notes>,
+    pub remarks: Vec<ely_lok::show::Remark>,
+    /// The shown slide's transition and effects; none on a master.
+    pub motion: Option<(ely_lok::show::Transition, Vec<ely_lok::show::Effect>)>,
+    pub media: Vec<ely_lok::show::Media>,
+    /// Counts completed reads.
+    pub reads: u64,
+    /// The slide size in twips.
+    pub size: (i64, i64),
+    /// Undo and redo lists at the last read.
+    pub history: Option<(Vec<Step>, Vec<Step>)>,
+    /// A size sent, in 1/100 mm, until read back.
+    pub size_asked: Option<(i64, i64)>,
+    /// A transition sent for a slide, until read back.
+    pub transition_asked: Option<(String, ely_lok::show::Transition, u64)>,
+    /// Pictures by slide name; stale ones show until repainted.
+    pub thumbs: HashMap<String, Arc<RenderImage>>,
+    pub retired: ely_gpui_component::primitives::Retired,
+    pub stale: HashSet<String>,
+    /// Pictures that failed; retried after the next read.
+    pub failed: HashSet<String>,
+    pub painting: bool,
+    /// The parts are masters.
+    pub masters: bool,
+    /// The scheme the pictures were painted with.
+    pub dark: Option<bool>,
+    /// The view was fitted to the slide once.
+    pub fitted: bool,
+}
+
+impl Extra {
+    /// The size to show, in 1/100 mm: asked, else read.
+    pub fn shown_size(&self) -> (i64, i64) {
+        self.size_asked
+            .unwrap_or_else(|| crate::design::mm100(self.size))
+    }
+}
diff --git a/apps/ely-show/src/main.rs b/apps/ely-show/src/main.rs
index 8ab6928..072595b 100644
--- a/apps/ely-show/src/main.rs
+++ b/apps/ely-show/src/main.rs
@@ -3,6 +3,7 @@ mod check;
 mod deck;
 mod design;
 mod dialog;
+mod extra;
 mod guides;
 mod insert;
 mod list;
diff --git a/apps/ely-show/src/tests/slides.rs b/apps/ely-show/src/tests/slides.rs
index e55e481..9f51870 100644
--- a/apps/ely-show/src/tests/slides.rs
+++ b/apps/ely-show/src/tests/slides.rs
@@ -384,3 +384,27 @@ fn a_comment_picked_on_another_slide_shows_its_slide_again() {
     settle(&cx, |app| current(app) == Some(0));
     assert_eq!(cx.update(|app| deck.read(app).shown_remark()), Some(key));
 }
+
+#[test]
+fn a_zoom_stays_through_later_reports() {
+    use ely_gpui_component::shell::ZoomStep;
+    let dir = tempfile::tempdir().expect("a temp dir");
+    let mut cx = TestAppContext::single();
+    let Some(deck) = blank(&mut cx, dir.path()) else {
+        eprintln!("SKIP: no LOK build");
+        return;
+    };
+    let view = |app: &gpui::App| deck.read(app).active_tab().expect("a tab").view.clone();
+    settle(&cx, |app| view(app).read(app).fitting());
+    update(&mut cx, &deck, |deck, cx| deck.zoom(ZoomStep::In, cx));
+    let zoom = cx.update(|app| view(app).read(app).zoom());
+    update(&mut cx, &deck, |deck, cx| {
+        let (id, view) = deck.active_tab().map(|tab| (tab.id, tab.view.clone())).expect("a tab");
+        deck.observed(id, &view, cx);
+    });
+    cx.update(|app| {
+        let view = view(app);
+        assert!(!view.read(app).fitting(), "a report does not fit the slide again");
+        assert_eq!(view.read(app).zoom(), zoom, "the zoom stays");
+    });
+}
diff --git a/tasks/BUGS.md b/tasks/BUGS.md
index a8f645d..ed45409 100644
--- a/tasks/BUGS.md
+++ b/tasks/BUGS.md
@@ -24,8 +24,8 @@
 - [ ] T-14 导入扫描把整个文件的每个字段都建成字符串
 - [ ] T-15 非 UTF-8 文本的默认编码跟系统区域而不是界面语言
 - [ ] S-01 切换幻灯片后主画布不重画
-- [ ] S-02 `deck.rs` 超过 500 行
-- [ ] S-03 ElyShow 的缩放一两帧后弹回“适合幻灯片”，缩放功能不可用
+- [x] S-02 `deck.rs` 超过 500 行 — 随 S-03 把 Extra 移到 extra.rs，deck.rs 463 行
+- [x] S-03 ElyShow 的缩放一两帧后弹回“适合幻灯片”，缩放功能不可用 — 只在标签首次观察时适合一次；R1 PASS
 - [ ] S-04 选屏对话框被别的对话框顶掉后，`show_starting` 卡住、放映副本泄漏
 - [ ] S-05 一条批注的时间恰为午夜或只有日期，整个批注栏不显示
 - [ ] S-06 导出或打印的“从–到”填 0 时导出全部幻灯片
diff --git a/tasks/reviews/S-03-r1.md b/tasks/reviews/S-03-r1.md
new file mode 100644
index 0000000..7ef22e9
--- /dev/null
+++ b/tasks/reviews/S-03-r1.md
@@ -0,0 +1 @@
+PASS