diff --git a/.wt-consolidate b/.wt-consolidate
new file mode 160000
index 000000000..e1604d179
--- /dev/null
+++ b/.wt-consolidate
@@ -0,0 +1 @@
+Subproject commit e1604d17915fe5a1f8d75fe9a5eef449226ec867
diff --git a/.wt-delim b/.wt-delim
new file mode 160000
index 000000000..e1604d179
--- /dev/null
+++ b/.wt-delim
@@ -0,0 +1 @@
+Subproject commit e1604d17915fe5a1f8d75fe9a5eef449226ec867
diff --git a/.wt-display b/.wt-display
new file mode 160000
index 000000000..e1604d179
--- /dev/null
+++ b/.wt-display
@@ -0,0 +1 @@
+Subproject commit e1604d17915fe5a1f8d75fe9a5eef449226ec867
diff --git a/.wt-engine b/.wt-engine
new file mode 160000
index 000000000..e1604d179
--- /dev/null
+++ b/.wt-engine
@@ -0,0 +1 @@
+Subproject commit e1604d17915fe5a1f8d75fe9a5eef449226ec867
diff --git a/.wt-fill b/.wt-fill
new file mode 160000
index 000000000..e1604d179
--- /dev/null
+++ b/.wt-fill
@@ -0,0 +1 @@
+Subproject commit e1604d17915fe5a1f8d75fe9a5eef449226ec867
diff --git a/.wt-fonts b/.wt-fonts
new file mode 160000
index 000000000..e1604d179
--- /dev/null
+++ b/.wt-fonts
@@ -0,0 +1 @@
+Subproject commit e1604d17915fe5a1f8d75fe9a5eef449226ec867
diff --git a/.wt-hf b/.wt-hf
new file mode 160000
index 000000000..e1604d179
--- /dev/null
+++ b/.wt-hf
@@ -0,0 +1 @@
+Subproject commit e1604d17915fe5a1f8d75fe9a5eef449226ec867
diff --git a/.wt-keytips b/.wt-keytips
new file mode 160000
index 000000000..e1604d179
--- /dev/null
+++ b/.wt-keytips
@@ -0,0 +1 @@
+Subproject commit e1604d17915fe5a1f8d75fe9a5eef449226ec867
diff --git a/.wt-numval b/.wt-numval
new file mode 160000
index 000000000..e1604d179
--- /dev/null
+++ b/.wt-numval
@@ -0,0 +1 @@
+Subproject commit e1604d17915fe5a1f8d75fe9a5eef449226ec867
diff --git a/.wt-passthrough b/.wt-passthrough
new file mode 160000
index 000000000..e1604d179
--- /dev/null
+++ b/.wt-passthrough
@@ -0,0 +1 @@
+Subproject commit e1604d17915fe5a1f8d75fe9a5eef449226ec867
diff --git a/.wt-pivotfilter b/.wt-pivotfilter
new file mode 160000
index 000000000..e1604d179
--- /dev/null
+++ b/.wt-pivotfilter
@@ -0,0 +1 @@
+Subproject commit e1604d17915fe5a1f8d75fe9a5eef449226ec867
diff --git a/.wt-textfn b/.wt-textfn
new file mode 160000
index 000000000..e1604d179
--- /dev/null
+++ b/.wt-textfn
@@ -0,0 +1 @@
+Subproject commit e1604d17915fe5a1f8d75fe9a5eef449226ec867
diff --git a/crates/xlsx/src/styles.rs b/crates/xlsx/src/styles.rs
index c1f93aca9..d962881d3 100644
--- a/crates/xlsx/src/styles.rs
+++ b/crates/xlsx/src/styles.rs
@@ -59,11 +59,14 @@ fn bool_prop(e: &El, name: &str) -> bool {
 
 const DEFAULT_FONT_FAMILY: u8 = 2;
 const MAX_FONT_FAMILY: u8 = 14;
+/// Longest font name kept, in characters (Excel's own limit). Every cell format copies its
+/// font, so a long name repeated by many formats would otherwise multiply in memory.
+const MAX_FONT_NAME: usize = 31;
 
 pub fn read_font(e: &El, palette: &[u32]) -> Font {
     let mut f = Font::default();
     if let Some(n) = e.child("name").or_else(|| e.child("rFont")).and_then(|n| n.attr("val")) {
-        f.name = n.to_string();
+        f.name = n.chars().take(MAX_FONT_NAME).collect();
     }
     if let Some(sz) = e.child("sz").and_then(|s| s.attr_f64("val")) {
         f.size = sz.clamp(1.0, 409.0) as f32;
@@ -277,14 +280,14 @@ fn read_protection(p: &El) -> Protection {
     Protection { locked: p.flag("locked", true), hidden: p.flag("hidden", false) }
 }
 
-fn num_fmt_code(id: u32, custom: &HashMap<u32, String>) -> NumFmt {
+fn num_fmt_code(id: u32, custom: &HashMap<u32, NumFmt>) -> NumFmt {
     if let Some(c) = custom.get(&id) {
-        return NumFmt::new(c);
+        return c.clone();
     }
     NumFmt::new(builtin_format(id).unwrap_or("General"))
 }
 
-fn read_xf(xf: &El, fonts: &[Font], fills: &[Fill], borders: &[Borders], fmts: &HashMap<u32, String>, checkboxes: &[bool]) -> Style {
+fn read_xf(xf: &El, fonts: &[Font], fills: &[Fill], borders: &[Borders], fmts: &HashMap<u32, NumFmt>, checkboxes: &[bool]) -> Style {
     let mut s = Style::default();
     if let Some(f) = xf.attr_u32("fontId").and_then(|i| fonts.get(i as usize)) {
         s.font = f.clone();
@@ -336,6 +339,8 @@ pub fn read_styles(root: &El, checkboxes: &[bool], minor_font: &str) -> StylesIn
             }
         }
     }
+    // One shared copy of each custom code, which every format using it points to.
+    let shared_fmts: HashMap<u32, NumFmt> = fmts.iter().map(|(id, code)| (*id, NumFmt::new(code))).collect();
     // The scheme link only means something on a font in the body face; elsewhere it stays as a new font has it.
     let body_font = |e: &El| {
         let mut f = read_font(e, &palette);
@@ -345,10 +350,14 @@ pub fn read_styles(root: &El, checkboxes: &[bool], minor_font: &str) -> StylesIn
     let fonts: Vec<Font> = root.child("fonts").map(|f| f.kids("font").map(body_font).collect()).unwrap_or_default();
     let fills: Vec<Fill> = root.child("fills").map(|f| f.kids("fill").map(|e| read_fill(e, &palette, false)).collect()).unwrap_or_default();
     let borders: Vec<Borders> = root.child("borders").map(|f| f.kids("border").map(|e| read_border(e, &palette)).collect()).unwrap_or_default();
-    let xfs =
-        root.child("cellXfs").map(|x| x.kids("xf").map(|xf| read_xf(xf, &fonts, &fills, &borders, &fmts, checkboxes)).collect()).unwrap_or_default();
-    let style_xfs: Vec<Style> =
-        root.child("cellStyleXfs").map(|x| x.kids("xf").map(|xf| read_xf(xf, &fonts, &fills, &borders, &fmts, &[])).collect()).unwrap_or_default();
+    let xfs = root
+        .child("cellXfs")
+        .map(|x| x.kids("xf").map(|xf| read_xf(xf, &fonts, &fills, &borders, &shared_fmts, checkboxes)).collect())
+        .unwrap_or_default();
+    let style_xfs: Vec<Style> = root
+        .child("cellStyleXfs")
+        .map(|x| x.kids("xf").map(|xf| read_xf(xf, &fonts, &fills, &borders, &shared_fmts, &[])).collect())
+        .unwrap_or_default();
     let mut named = Vec::new();
     if let Some(cs) = root.child("cellStyles") {
         for c in cs.kids("cellStyle") {
@@ -359,12 +368,12 @@ pub fn read_styles(root: &El, checkboxes: &[bool], minor_font: &str) -> StylesIn
             }
         }
     }
-    let dxfs = root.child("dxfs").map(|d| d.kids("dxf").map(|x| read_dxf(x, &palette, &fmts)).collect()).unwrap_or_default();
+    let dxfs = root.child("dxfs").map(|d| d.kids("dxf").map(|x| read_dxf(x, &palette, &shared_fmts)).collect()).unwrap_or_default();
     StylesIn { xfs, dxfs, palette, named, num_fmts: fmts }
 }
 
 /// One differential format (`dxf`): the style it sets over a cell's own.
-fn read_dxf(x: &El, palette: &[u32], fmts: &HashMap<u32, String>) -> Style {
+fn read_dxf(x: &El, palette: &[u32], fmts: &HashMap<u32, NumFmt>) -> Style {
     let mut s = Style::default();
     if let Some(e) = x.child("font") {
         let f = read_font(e, palette);
diff --git a/crates/xlsx/src/tests/malformed.rs b/crates/xlsx/src/tests/malformed.rs
index 0fb9f1b43..c80572593 100644
--- a/crates/xlsx/src/tests/malformed.rs
+++ b/crates/xlsx/src/tests/malformed.rs
@@ -385,3 +385,22 @@ fn outline_summary_directions_round_trip() {
     let xml = String::from_utf8(crate::package::Package::open(&bytes).unwrap().read("xl/worksheets/sheet1.xml").unwrap().unwrap()).unwrap();
     assert!(!xml.contains("outlinePr"), "{xml}");
 }
+
+/// Many cell formats naming one long font and one long custom number format: the code is shared
+/// by every format and the font name is cut to Excel's 31 characters, so neither is copied per
+/// format.
+#[test]
+fn cell_formats_share_their_number_format_and_keep_short_font_names() {
+    let xml = format!(
+        r#"<styleSheet><numFmts><numFmt numFmtId="164" formatCode="{}"/></numFmts><fonts><font><name val="{}"/></font></fonts><cellXfs>{}</cellXfs></styleSheet>"#,
+        "0".repeat(100_000),
+        "F".repeat(100_000),
+        r#"<xf numFmtId="164" fontId="0"/>"#.repeat(20_000)
+    );
+    let root = crate::xml::parse(xml.as_bytes()).unwrap();
+    let st = crate::styles::read_styles(&root, &[], "Calibri");
+    assert_eq!(st.xfs.len(), 20_000);
+    assert!(st.xfs.iter().all(|s| std::sync::Arc::ptr_eq(&s.num_fmt.0, &st.xfs[0].num_fmt.0)));
+    assert_eq!(st.xfs[0].num_fmt.as_str().len(), 100_000);
+    assert!(st.xfs.iter().all(|s| s.font.name.chars().count() == 31));
+}