diff --git a/crates/engine/src/cmd/sheet.rs b/crates/engine/src/cmd/sheet.rs
index ea615cb83..276d14f13 100644
--- a/crates/engine/src/cmd/sheet.rs
+++ b/crates/engine/src/cmd/sheet.rs
@@ -12,6 +12,10 @@ use super::{
     str_param, target_range, target_sheet, u32_param,
 };
 
+mod tabs;
+
+use tabs::{activate, delete_sheet, hide_sheet, insert_sheet, move_sheet, rename_sheet, step_sheet, tab_color, unhide_sheet};
+
 pub fn specs() -> Vec<CommandSpec> {
     vec![
         cmd!(
@@ -694,42 +698,6 @@ fn insert_copied_steps(s: &mut Session, clip: &crate::Clipboard, sheet: usize, a
     Ok((moved, out))
 }
 
-fn insert_sheet(s: &mut Session, p: &Json) -> Result<Json> {
-    if s.doc()?.wb.protected_structure {
-        return Err(EngineError::Other("The workbook is protected and cannot be changed.".into()));
-    }
-    let name = match str_param(p, "name") {
-        Some(n) => n.to_string(),
-        None => s.doc()?.wb.next_sheet_name(),
-    };
-    s.doc()?.wb.check_sheet_name(&name, None).map_err(EngineError::Other)?;
-    let d = s.doc_mut()?;
-    let before = p.get("before").and_then(Json::as_u64).map(|v| v as usize);
-    let idx = edit_doc(d, |cx| {
-        // Excel inserts before the active sheet; the "+" button appends after it.
-        let at = before.unwrap_or(cx.wb.active_sheet() + 1).min(cx.wb.sheets.len());
-        cx.wb.sheets.insert(at, Arc::new(Sheet::new(name.clone())));
-        // Names scoped to later sheets shift.
-        for n in cx.wb.names.iter_mut() {
-            if let Some(sc) = n.scope.as_mut()
-                && *sc >= at
-            {
-                *sc += 1;
-            }
-        }
-        cx.wb.set_active_sheet(at);
-        *cx.sel = crate::Selection::default();
-        cx.structural = true;
-        Ok(at)
-    })?;
-    d.sheet_selections.insert(idx.min(d.sheet_selections.len()), crate::Selection::default());
-    Ok(json!({"index": idx, "name": name}))
-}
-
-fn edit_doc<R>(d: &mut crate::DocState, f: impl FnOnce(&mut Ctx) -> Result<R>) -> Result<R> {
-    super::commit(d, f)
-}
-
 /// Sheet protection for inserting or deleting rows/columns: the protection must allow it, and
 /// deleted lines must not hold locked cells.
 fn check_lines_protection(s: &Session, p: &Json, axis: Axis, at: u32, count: u32, insert: bool) -> Result<()> {
@@ -763,254 +731,6 @@ fn check_lines_protection(s: &Session, p: &Json, axis: Axis, at: u32, count: u32
     Ok(())
 }
 
-fn delete_sheet(s: &mut Session, p: &Json) -> Result<Json> {
-    let i = target_sheet(s, p)?;
-    let d = s.doc()?;
-    if d.wb.protected_structure {
-        return Err(EngineError::Other("The workbook is protected and cannot be changed.".into()));
-    }
-    if d.wb.sheets.iter().filter(|s| s.visibility == Visibility::Visible).count() <= 1 {
-        return Err(EngineError::Other("A workbook must contain at least one visible worksheet.".into()));
-    }
-    let name = d.wb.sheet(i).map(|s| s.name.clone()).unwrap_or_default();
-    let order: Vec<String> = d.wb.sheets.iter().map(|s| s.name.clone()).collect();
-    let d = s.doc_mut()?;
-    edit_doc(d, |cx| {
-        cx.wb.sheets.remove(i);
-        for si in 0..cx.wb.sheets.len() {
-            let keys: Vec<(CellRef, Arc<gridcraft_model::Formula>)> =
-                cx.wb.sheets.get(si).map(|s| s.cells.iter().filter_map(|(c, x)| x.formula.clone().map(|f| (c, f))).collect()).unwrap_or_default();
-            let Some(sh) = cx.wb.sheet_mut(si) else { continue };
-            for (c, f) in keys {
-                if let Some(e) = f.expr() {
-                    let ne = gridcraft_formula::adjust::delete_sheet(e, &name, &order);
-                    if let Some(cell) = sh.cells.get_mut(c) {
-                        cell.formula = Some(Arc::new(gridcraft_model::Formula::from_expr(ne)));
-                    }
-                }
-            }
-        }
-        cx.wb.names.retain(|n| n.scope != Some(i));
-        for n in cx.wb.names.iter_mut() {
-            if let Some(sc) = n.scope.as_mut()
-                && *sc > i
-            {
-                *sc -= 1;
-            }
-            // Names referring to the sheet become #REF!.
-            if let Ok(e) = gridcraft_formula::parse_name(&n.formula) {
-                let ne = gridcraft_formula::adjust::delete_sheet(e.clone(), &name, &order);
-                if ne != e {
-                    n.formula = gridcraft_formula::print(&ne);
-                }
-            }
-        }
-        if cx.wb.active_sheet() >= cx.wb.sheets.len() || cx.wb.active_sheet() > i {
-            cx.wb.set_active_sheet(cx.wb.active_sheet().saturating_sub(1).min(cx.wb.sheets.len().saturating_sub(1)));
-        }
-        *cx.sel = crate::Selection::default();
-        cx.structural = true;
-        Ok(())
-    })?;
-    if i < d.sheet_selections.len() {
-        d.sheet_selections.remove(i);
-    }
-    ok()
-}
-
-fn rename_sheet(s: &mut Session, p: &Json) -> Result<Json> {
-    if s.doc()?.wb.protected_structure {
-        return Err(EngineError::Other("The workbook is protected and cannot be changed.".into()));
-    }
-    let i = target_sheet(s, p)?;
-    let Some(name) = str_param(p, "name").map(|n| n.trim().to_string()) else { return Err(bad("sheet.rename", "missing `name`")) };
-    s.doc()?.wb.check_sheet_name(&name, Some(i)).map_err(EngineError::Other)?;
-    edit(s, |cx| {
-        let old = cx.wb.sheet(i).map(|s| s.name.clone()).unwrap_or_default();
-        cx.sheet_mut(i)?.name = name.clone();
-        for si in 0..cx.wb.sheets.len() {
-            let keys: Vec<(CellRef, Arc<gridcraft_model::Formula>)> =
-                cx.wb.sheets.get(si).map(|s| s.cells.iter().filter_map(|(c, x)| x.formula.clone().map(|f| (c, f))).collect()).unwrap_or_default();
-            let Some(sh) = cx.wb.sheet_mut(si) else { continue };
-            for (c, f) in keys {
-                if let Some(e) = f.expr() {
-                    let ne = gridcraft_formula::adjust::rename_sheet(e, &old, &name);
-                    let text = gridcraft_formula::print(&ne);
-                    if text != f.text
-                        && let Some(cell) = sh.cells.get_mut(c)
-                    {
-                        cell.formula = Some(Arc::new(gridcraft_model::Formula::from_expr(ne)));
-                    }
-                }
-            }
-            let fix = |t: &str| {
-                gridcraft_formula::parse(t)
-                    .map(|e| gridcraft_formula::print(&gridcraft_formula::adjust::rename_sheet(e, &old, &name)))
-                    .unwrap_or_else(|_| t.to_string())
-            };
-            for ch in sh.charts.iter_mut() {
-                for se in ch.series.iter_mut() {
-                    se.values = fix(&se.values);
-                    se.categories = se.categories.as_deref().map(fix);
-                    se.name = se.name.as_deref().map(fix);
-                }
-                // A PivotChart follows its PivotTable's sheet.
-                if let Some((sheet, pivot)) = ch.pivot.as_deref().and_then(crate::pivot::parse_chart_link)
-                    && sheet.eq_ignore_ascii_case(&old)
-                {
-                    ch.pivot = Some(crate::pivot::chart_link(&name, &pivot));
-                }
-            }
-        }
-        for n in cx.wb.names.iter_mut() {
-            if let Ok(e) = gridcraft_formula::parse_name(&n.formula) {
-                n.formula = gridcraft_formula::print(&gridcraft_formula::adjust::rename_sheet(e, &old, &name));
-            }
-        }
-        cx.structural = true;
-        Ok(Json::Null)
-    })
-}
-
-fn move_sheet(s: &mut Session, p: &Json) -> Result<Json> {
-    if s.doc()?.wb.protected_structure {
-        return Err(EngineError::Other("The workbook is protected and cannot be changed.".into()));
-    }
-    let i = target_sheet(s, p)?;
-    let copy = bool_param(p, "copy").unwrap_or(false);
-    let to = p.get("to").and_then(Json::as_u64).map(|v| v as usize).ok_or_else(|| bad("sheet.move", "missing `to`"))?;
-    edit(s, |cx| {
-        let n = cx.wb.sheets.len();
-        let Some(src) = cx.wb.sheets.get(i).cloned() else { return Err(bad("sheet.move", "no such sheet")) };
-        if copy {
-            let mut sh = (*src).clone();
-            let base = sh.name.clone();
-            // `Name (2)`: the name is shortened so the suffix fits in Excel's 31 characters.
-            let name = (2..)
-                .map(|k| {
-                    let suffix = format!(" ({k})");
-                    let keep = 31usize.saturating_sub(suffix.chars().count());
-                    format!("{}{suffix}", base.chars().take(keep).collect::<String>().trim_end())
-                })
-                .find(|nm| cx.wb.sheet_index(nm).is_none())
-                .unwrap_or(base.clone());
-            sh.name = name;
-            sh.tables.clear(); // table names must be unique
-            sh.preserved = None; // kept file content (form controls, OLE objects…) stays with the original
-            let at = to.min(n);
-            // The copy gets its own copies of the sheet's names, referring to the copy.
-            let copies: Vec<gridcraft_model::DefinedName> = cx
-                .wb
-                .names
-                .iter()
-                .filter(|nm| nm.scope == Some(i))
-                .map(|nm| {
-                    let formula = gridcraft_formula::parse_name(&nm.formula)
-                        .map(|e| gridcraft_formula::print(&gridcraft_formula::adjust::rename_sheet(e, &base, &sh.name)))
-                        .unwrap_or_else(|_| nm.formula.clone());
-                    gridcraft_model::DefinedName { scope: Some(at), formula, ..nm.clone() }
-                })
-                .collect();
-            for nm in cx.wb.names.iter_mut() {
-                if let Some(sc) = nm.scope.as_mut()
-                    && *sc >= at
-                {
-                    *sc += 1;
-                }
-            }
-            cx.wb.names.extend(copies);
-            cx.wb.sheets.insert(at, Arc::new(sh));
-            cx.wb.set_active_sheet(at);
-        } else {
-            let sh = cx.wb.sheets.remove(i);
-            let at = to.min(n - 1);
-            cx.wb.sheets.insert(at, sh);
-            cx.wb.set_active_sheet(at);
-            // Sheet-level names follow their sheet.
-            for nm in cx.wb.names.iter_mut() {
-                if let Some(sc) = nm.scope.as_mut() {
-                    *sc = match *sc {
-                        x if x == i => at,
-                        x if i < x && x <= at => x - 1,
-                        x if at <= x && x < i => x + 1,
-                        x => x,
-                    };
-                }
-            }
-        }
-        cx.structural = true;
-        Ok(Json::Null)
-    })
-}
-
-fn tab_color(s: &mut Session, p: &Json) -> Result<Json> {
-    let i = target_sheet(s, p)?;
-    let c = super::format::color_param(p.get("color"));
-    edit(s, |cx| {
-        cx.sheet_mut(i)?.tab_color = c.filter(|c| *c != gridcraft_model::Color::Auto);
-        Ok(Json::Null)
-    })
-}
-
-fn hide_sheet(s: &mut Session, p: &Json) -> Result<Json> {
-    if s.doc()?.wb.protected_structure {
-        return Err(EngineError::Other("The workbook is protected and cannot be changed.".into()));
-    }
-    let i = target_sheet(s, p)?;
-    if s.doc()?.wb.sheets.iter().filter(|s| s.visibility == Visibility::Visible).count() <= 1 {
-        return Err(EngineError::Other("A workbook must contain at least one visible worksheet.".into()));
-    }
-    edit(s, |cx| {
-        cx.sheet_mut(i)?.visibility = Visibility::Hidden;
-        if cx.wb.active_sheet() == i {
-            cx.wb.set_active_sheet(cx.wb.sheets.iter().position(|s| s.visibility == Visibility::Visible).unwrap_or(0));
-        }
-        Ok(Json::Null)
-    })
-}
-
-fn unhide_sheet(s: &mut Session, p: &Json) -> Result<Json> {
-    if s.doc()?.wb.protected_structure {
-        return Err(EngineError::Other("The workbook is protected and cannot be changed.".into()));
-    }
-    if p.get("sheet").is_none() {
-        let hidden: Vec<String> = s.doc()?.wb.sheets.iter().filter(|s| s.visibility != Visibility::Visible).map(|s| s.name.clone()).collect();
-        if hidden.is_empty() {
-            return Err(EngineError::Other("No sheets are hidden.".into()));
-        }
-        s.ui_requests.push(crate::UiRequest::Dialog("unhideSheet".into(), json!({"sheets": hidden})));
-        return ok();
-    }
-    let i = target_sheet(s, p)?;
-    edit(s, |cx| {
-        cx.sheet_mut(i)?.visibility = Visibility::Visible;
-        cx.wb.set_active_sheet(i);
-        Ok(Json::Null)
-    })
-}
-
-fn activate(s: &mut Session, p: &Json) -> Result<Json> {
-    let i = target_sheet(s, p)?;
-    let d = s.doc_mut()?;
-    d.wb_switch_sheet(i);
-    Ok(json!({"sheet": i, "name": d.wb.active().map(|s| s.name.clone())}))
-}
-
-fn step_sheet(s: &mut Session, dir: isize) -> Result<Json> {
-    let d = s.doc()?;
-    let mut i = d.wb.active_sheet();
-    while let Some(next) = i.checked_add_signed(dir) {
-        let Some(sheet) = d.wb.sheet(next) else { break };
-        if sheet.visibility == Visibility::Visible {
-            s.doc_mut()?.wb_switch_sheet(next);
-            return ok();
-        }
-        i = next;
-    }
-    // No visible sheet in this direction: keep the current sheet and its selection.
-    ok()
-}
-
 /// Where a range of the edited sheet goes after a structural edit (`None` = deleted).
 pub(crate) fn map_range(r: RangeRef, e: &Edit) -> Option<RangeRef> {
     let expr = gridcraft_formula::Expr::Ref(gridcraft_formula::Reference {
diff --git a/crates/engine/src/cmd/sheet/tabs.rs b/crates/engine/src/cmd/sheet/tabs.rs
new file mode 100644
index 000000000..245404723
--- /dev/null
+++ b/crates/engine/src/cmd/sheet/tabs.rs
@@ -0,0 +1,285 @@
+use super::*;
+
+pub(super) fn insert_sheet(s: &mut Session, p: &Json) -> Result<Json> {
+    if s.doc()?.wb.protected_structure {
+        return Err(EngineError::Other("The workbook is protected and cannot be changed.".into()));
+    }
+    let name = match str_param(p, "name") {
+        Some(n) => n.to_string(),
+        None => s.doc()?.wb.next_sheet_name(),
+    };
+    s.doc()?.wb.check_sheet_name(&name, None).map_err(EngineError::Other)?;
+    let d = s.doc_mut()?;
+    let before = p.get("before").and_then(Json::as_u64).map(|v| v as usize);
+    let idx = edit_doc(d, |cx| {
+        // Excel inserts before the active sheet; the "+" button appends after it.
+        let at = before.unwrap_or(cx.wb.active_sheet() + 1).min(cx.wb.sheets.len());
+        cx.wb.sheets.insert(at, Arc::new(Sheet::new(name.clone())));
+        // Names scoped to later sheets shift.
+        for n in cx.wb.names.iter_mut() {
+            if let Some(sc) = n.scope.as_mut()
+                && *sc >= at
+            {
+                *sc += 1;
+            }
+        }
+        cx.wb.set_active_sheet(at);
+        *cx.sel = crate::Selection::default();
+        cx.structural = true;
+        Ok(at)
+    })?;
+    d.sheet_selections.insert(idx.min(d.sheet_selections.len()), crate::Selection::default());
+    Ok(json!({"index": idx, "name": name}))
+}
+
+fn edit_doc<R>(d: &mut crate::DocState, f: impl FnOnce(&mut Ctx) -> Result<R>) -> Result<R> {
+    crate::cmd::commit(d, f)
+}
+
+pub(super) fn delete_sheet(s: &mut Session, p: &Json) -> Result<Json> {
+    let i = target_sheet(s, p)?;
+    let d = s.doc()?;
+    if d.wb.protected_structure {
+        return Err(EngineError::Other("The workbook is protected and cannot be changed.".into()));
+    }
+    if d.wb.sheets.iter().filter(|s| s.visibility == Visibility::Visible).count() <= 1 {
+        return Err(EngineError::Other("A workbook must contain at least one visible worksheet.".into()));
+    }
+    let name = d.wb.sheet(i).map(|s| s.name.clone()).unwrap_or_default();
+    let order: Vec<String> = d.wb.sheets.iter().map(|s| s.name.clone()).collect();
+    let d = s.doc_mut()?;
+    edit_doc(d, |cx| {
+        cx.wb.sheets.remove(i);
+        for si in 0..cx.wb.sheets.len() {
+            let keys: Vec<(CellRef, Arc<gridcraft_model::Formula>)> =
+                cx.wb.sheets.get(si).map(|s| s.cells.iter().filter_map(|(c, x)| x.formula.clone().map(|f| (c, f))).collect()).unwrap_or_default();
+            let Some(sh) = cx.wb.sheet_mut(si) else { continue };
+            for (c, f) in keys {
+                if let Some(e) = f.expr() {
+                    let ne = gridcraft_formula::adjust::delete_sheet(e, &name, &order);
+                    if let Some(cell) = sh.cells.get_mut(c) {
+                        cell.formula = Some(Arc::new(gridcraft_model::Formula::from_expr(ne)));
+                    }
+                }
+            }
+        }
+        cx.wb.names.retain(|n| n.scope != Some(i));
+        for n in cx.wb.names.iter_mut() {
+            if let Some(sc) = n.scope.as_mut()
+                && *sc > i
+            {
+                *sc -= 1;
+            }
+            // Names referring to the sheet become #REF!.
+            if let Ok(e) = gridcraft_formula::parse_name(&n.formula) {
+                let ne = gridcraft_formula::adjust::delete_sheet(e.clone(), &name, &order);
+                if ne != e {
+                    n.formula = gridcraft_formula::print(&ne);
+                }
+            }
+        }
+        if cx.wb.active_sheet() >= cx.wb.sheets.len() || cx.wb.active_sheet() > i {
+            cx.wb.set_active_sheet(cx.wb.active_sheet().saturating_sub(1).min(cx.wb.sheets.len().saturating_sub(1)));
+        }
+        *cx.sel = crate::Selection::default();
+        cx.structural = true;
+        Ok(())
+    })?;
+    if i < d.sheet_selections.len() {
+        d.sheet_selections.remove(i);
+    }
+    ok()
+}
+
+pub(super) fn rename_sheet(s: &mut Session, p: &Json) -> Result<Json> {
+    if s.doc()?.wb.protected_structure {
+        return Err(EngineError::Other("The workbook is protected and cannot be changed.".into()));
+    }
+    let i = target_sheet(s, p)?;
+    let Some(name) = str_param(p, "name").map(|n| n.trim().to_string()) else { return Err(bad("sheet.rename", "missing `name`")) };
+    s.doc()?.wb.check_sheet_name(&name, Some(i)).map_err(EngineError::Other)?;
+    edit(s, |cx| {
+        let old = cx.wb.sheet(i).map(|s| s.name.clone()).unwrap_or_default();
+        cx.sheet_mut(i)?.name = name.clone();
+        for si in 0..cx.wb.sheets.len() {
+            let keys: Vec<(CellRef, Arc<gridcraft_model::Formula>)> =
+                cx.wb.sheets.get(si).map(|s| s.cells.iter().filter_map(|(c, x)| x.formula.clone().map(|f| (c, f))).collect()).unwrap_or_default();
+            let Some(sh) = cx.wb.sheet_mut(si) else { continue };
+            for (c, f) in keys {
+                if let Some(e) = f.expr() {
+                    let ne = gridcraft_formula::adjust::rename_sheet(e, &old, &name);
+                    let text = gridcraft_formula::print(&ne);
+                    if text != f.text
+                        && let Some(cell) = sh.cells.get_mut(c)
+                    {
+                        cell.formula = Some(Arc::new(gridcraft_model::Formula::from_expr(ne)));
+                    }
+                }
+            }
+            let fix = |t: &str| {
+                gridcraft_formula::parse(t)
+                    .map(|e| gridcraft_formula::print(&gridcraft_formula::adjust::rename_sheet(e, &old, &name)))
+                    .unwrap_or_else(|_| t.to_string())
+            };
+            for ch in sh.charts.iter_mut() {
+                for se in ch.series.iter_mut() {
+                    se.values = fix(&se.values);
+                    se.categories = se.categories.as_deref().map(fix);
+                    se.name = se.name.as_deref().map(fix);
+                }
+                // A PivotChart follows its PivotTable's sheet.
+                if let Some((sheet, pivot)) = ch.pivot.as_deref().and_then(crate::pivot::parse_chart_link)
+                    && sheet.eq_ignore_ascii_case(&old)
+                {
+                    ch.pivot = Some(crate::pivot::chart_link(&name, &pivot));
+                }
+            }
+        }
+        for n in cx.wb.names.iter_mut() {
+            if let Ok(e) = gridcraft_formula::parse_name(&n.formula) {
+                n.formula = gridcraft_formula::print(&gridcraft_formula::adjust::rename_sheet(e, &old, &name));
+            }
+        }
+        cx.structural = true;
+        Ok(Json::Null)
+    })
+}
+
+pub(super) fn move_sheet(s: &mut Session, p: &Json) -> Result<Json> {
+    if s.doc()?.wb.protected_structure {
+        return Err(EngineError::Other("The workbook is protected and cannot be changed.".into()));
+    }
+    let i = target_sheet(s, p)?;
+    let copy = bool_param(p, "copy").unwrap_or(false);
+    let to = p.get("to").and_then(Json::as_u64).map(|v| v as usize).ok_or_else(|| bad("sheet.move", "missing `to`"))?;
+    edit(s, |cx| {
+        let n = cx.wb.sheets.len();
+        let Some(src) = cx.wb.sheets.get(i).cloned() else { return Err(bad("sheet.move", "no such sheet")) };
+        if copy {
+            let mut sh = (*src).clone();
+            let base = sh.name.clone();
+            // `Name (2)`: the name is shortened so the suffix fits in Excel's 31 characters.
+            let name = (2..)
+                .map(|k| {
+                    let suffix = format!(" ({k})");
+                    let keep = 31usize.saturating_sub(suffix.chars().count());
+                    format!("{}{suffix}", base.chars().take(keep).collect::<String>().trim_end())
+                })
+                .find(|nm| cx.wb.sheet_index(nm).is_none())
+                .unwrap_or(base.clone());
+            sh.name = name;
+            sh.tables.clear(); // table names must be unique
+            sh.preserved = None; // kept file content (form controls, OLE objects…) stays with the original
+            let at = to.min(n);
+            // The copy gets its own copies of the sheet's names, referring to the copy.
+            let copies: Vec<gridcraft_model::DefinedName> = cx
+                .wb
+                .names
+                .iter()
+                .filter(|nm| nm.scope == Some(i))
+                .map(|nm| {
+                    let formula = gridcraft_formula::parse_name(&nm.formula)
+                        .map(|e| gridcraft_formula::print(&gridcraft_formula::adjust::rename_sheet(e, &base, &sh.name)))
+                        .unwrap_or_else(|_| nm.formula.clone());
+                    gridcraft_model::DefinedName { scope: Some(at), formula, ..nm.clone() }
+                })
+                .collect();
+            for nm in cx.wb.names.iter_mut() {
+                if let Some(sc) = nm.scope.as_mut()
+                    && *sc >= at
+                {
+                    *sc += 1;
+                }
+            }
+            cx.wb.names.extend(copies);
+            cx.wb.sheets.insert(at, Arc::new(sh));
+            cx.wb.set_active_sheet(at);
+        } else {
+            let sh = cx.wb.sheets.remove(i);
+            let at = to.min(n - 1);
+            cx.wb.sheets.insert(at, sh);
+            cx.wb.set_active_sheet(at);
+            // Sheet-level names follow their sheet.
+            for nm in cx.wb.names.iter_mut() {
+                if let Some(sc) = nm.scope.as_mut() {
+                    *sc = match *sc {
+                        x if x == i => at,
+                        x if i < x && x <= at => x - 1,
+                        x if at <= x && x < i => x + 1,
+                        x => x,
+                    };
+                }
+            }
+        }
+        cx.structural = true;
+        Ok(Json::Null)
+    })
+}
+
+pub(super) fn tab_color(s: &mut Session, p: &Json) -> Result<Json> {
+    let i = target_sheet(s, p)?;
+    let c = crate::cmd::format::color_param(p.get("color"));
+    edit(s, |cx| {
+        cx.sheet_mut(i)?.tab_color = c.filter(|c| *c != gridcraft_model::Color::Auto);
+        Ok(Json::Null)
+    })
+}
+
+pub(super) fn hide_sheet(s: &mut Session, p: &Json) -> Result<Json> {
+    if s.doc()?.wb.protected_structure {
+        return Err(EngineError::Other("The workbook is protected and cannot be changed.".into()));
+    }
+    let i = target_sheet(s, p)?;
+    if s.doc()?.wb.sheets.iter().filter(|s| s.visibility == Visibility::Visible).count() <= 1 {
+        return Err(EngineError::Other("A workbook must contain at least one visible worksheet.".into()));
+    }
+    edit(s, |cx| {
+        cx.sheet_mut(i)?.visibility = Visibility::Hidden;
+        if cx.wb.active_sheet() == i {
+            cx.wb.set_active_sheet(cx.wb.sheets.iter().position(|s| s.visibility == Visibility::Visible).unwrap_or(0));
+        }
+        Ok(Json::Null)
+    })
+}
+
+pub(super) fn unhide_sheet(s: &mut Session, p: &Json) -> Result<Json> {
+    if s.doc()?.wb.protected_structure {
+        return Err(EngineError::Other("The workbook is protected and cannot be changed.".into()));
+    }
+    if p.get("sheet").is_none() {
+        let hidden: Vec<String> = s.doc()?.wb.sheets.iter().filter(|s| s.visibility != Visibility::Visible).map(|s| s.name.clone()).collect();
+        if hidden.is_empty() {
+            return Err(EngineError::Other("No sheets are hidden.".into()));
+        }
+        s.ui_requests.push(crate::UiRequest::Dialog("unhideSheet".into(), json!({"sheets": hidden})));
+        return ok();
+    }
+    let i = target_sheet(s, p)?;
+    edit(s, |cx| {
+        cx.sheet_mut(i)?.visibility = Visibility::Visible;
+        cx.wb.set_active_sheet(i);
+        Ok(Json::Null)
+    })
+}
+
+pub(super) fn activate(s: &mut Session, p: &Json) -> Result<Json> {
+    let i = target_sheet(s, p)?;
+    let d = s.doc_mut()?;
+    d.wb_switch_sheet(i);
+    Ok(json!({"sheet": i, "name": d.wb.active().map(|s| s.name.clone())}))
+}
+
+pub(super) fn step_sheet(s: &mut Session, dir: isize) -> Result<Json> {
+    let d = s.doc()?;
+    let mut i = d.wb.active_sheet();
+    while let Some(next) = i.checked_add_signed(dir) {
+        let Some(sheet) = d.wb.sheet(next) else { break };
+        if sheet.visibility == Visibility::Visible {
+            s.doc_mut()?.wb_switch_sheet(next);
+            return ok();
+        }
+        i = next;
+    }
+    // No visible sheet in this direction: keep the current sheet and its selection.
+    ok()
+}