diff --git a/crates/ui-egui/src/menus.rs b/crates/ui-egui/src/menus.rs
index 951f827d..25b2fc23 100644
--- a/crates/ui-egui/src/menus.rs
+++ b/crates/ui-egui/src/menus.rs
@@ -561,6 +561,7 @@ pub fn invoke(app: &mut EffectcraftApp, ctx: &egui::Context, id: &str, params: V
         }
         "view.fit" => {
             app.ui.viewer.zoom = None;
+            app.ui.viewer.fit_up_to_100 = false;
             app.ui.viewer.pan = [0.0, 0.0];
             return Ok(Value::Null);
         }
diff --git a/crates/ui-egui/src/panels/layer_panel.rs b/crates/ui-egui/src/panels/layer_panel.rs
index e8cae2cd..c0ebf013 100644
--- a/crates/ui-egui/src/panels/layer_panel.rs
+++ b/crates/ui-egui/src/panels/layer_panel.rs
@@ -122,10 +122,11 @@ pub fn show(app: &mut EffectcraftApp, ui: &mut egui::Ui, rect: Rect) {
     // Bottom bar: magnification and View menus.
     p.rect_filled(bar, 0.0, t.panel_bg);
     let mr = Rect::from_min_size(pos2(bar.min.x + 8.0, bar.center().y - 10.0), vec2(80.0, 20.0));
-    if let Some(z) =
-        super::viewer_tools::magnification_menu(app, ui, mr, "layer-mag", "layerPanel.magnification", "layerMagnification", zoom as f32, app.ui.layer_zoom, fit)
+    if let Some((z, up)) =
+        super::viewer_tools::magnification_menu(app, ui, mr, "layer-mag", "layerPanel.magnification", "layerMagnification", zoom as f32, app.ui.layer_zoom, false)
     {
-        app.ui.layer_zoom = z;
+        // The Layer panel keeps no fit mode: Fit up to 100% is the fit, at most 100 %.
+        app.ui.layer_zoom = if up { Some(fit.min(1.0 / ui.ctx().pixels_per_point())) } else { z };
         app.ui.layer_pan = [0.0, 0.0];
     }
     let vx = mr.max.x + 10.0;
diff --git a/crates/ui-egui/src/panels/viewer.rs b/crates/ui-egui/src/panels/viewer.rs
index 9ab13879..cbb842d9 100644
--- a/crates/ui-egui/src/panels/viewer.rs
+++ b/crates/ui-egui/src/panels/viewer.rs
@@ -795,6 +795,8 @@ pub fn show(app: &mut EffectcraftApp, ui: &mut egui::Ui, rect: Rect) {
 
     let (cw, ch) = (comp.width as f32, comp.height as f32);
     let fit = ((area.width() - 40.0) / cw).min((area.height() - 40.0) / ch).max(0.01);
+    // Fit up to 100% follows the panel's size like Fit does, and stops at 100%.
+    let fit = if app.ui.viewer.fit_up_to_100 { fit.min(1.0 / ctx.pixels_per_point()) } else { fit };
     ctx.data_mut(|d| d.insert_temp(egui::Id::new("viewer-fit"), fit));
     let zoom = app.ui.viewer.zoom.unwrap_or(fit);
     let center = area.center() + vec2(app.ui.viewer.pan[0], app.ui.viewer.pan[1]);
@@ -1952,7 +1954,7 @@ pub fn show(app: &mut EffectcraftApp, ui: &mut egui::Ui, rect: Rect) {
 
     vt::draw_snap(&ctx, &painter, &map, &ectx);
     vt::rulers(app, ui, &map, outer, area);
-    vt::bottom_bar(app, ui, bar, zoom, fit, time, &comp);
+    vt::bottom_bar(app, ui, bar, zoom, time, &comp);
     if err_h > 0.0 {
         super::expr_bar::draw(app, ui, err_bar, cid);
     }
diff --git a/crates/ui-egui/src/panels/viewer_tools.rs b/crates/ui-egui/src/panels/viewer_tools.rs
index 2f7862e2..fa198505 100644
--- a/crates/ui-egui/src/panels/viewer_tools.rs
+++ b/crates/ui-egui/src/panels/viewer_tools.rs
@@ -523,8 +523,8 @@ pub(crate) fn magnification_menu(
     auto_items: &str,
     zoom: f32,
     current: Option<f32>,
-    fit: f32,
-) -> Option<Option<f32>> {
+    fit_up: bool,
+) -> Option<(Option<f32>, bool)> {
     let t = app.tokens;
     let ppp = ui.ctx().pixels_per_point();
     let pop = format!("{id}-pop");
@@ -540,17 +540,20 @@ pub(crate) fn magnification_menu(
         .iter()
         .map(|m| {
             let on = match *m {
-                "Fit" => current.is_none(),
+                "Fit" => current.is_none() && !fit_up,
+                "Fit up to 100%" => current.is_none() && fit_up,
                 s => s.trim_end_matches('%').parse::<f32>().is_ok_and(|v| current.is_some() && (v - cur).abs() < 0.06),
             };
             (m.to_string(), on)
         })
         .collect();
     let i = popup(app, ui, &pop, r, &items, auto_items)?;
+    // `(zoom, fit up to 100 %)`: Fit and Fit up to 100% leave the zoom unset (it follows the
+    // panel size).
     match *MAGS.get(i)? {
-        "Fit" => Some(None),
-        "Fit up to 100%" => Some(Some(fit.min(1.0 / ppp))),
-        s => s.trim_end_matches('%').parse::<f32>().ok().map(|v| Some(v / 100.0 / ppp)),
+        "Fit" => Some((None, false)),
+        "Fit up to 100%" => Some((None, true)),
+        s => s.trim_end_matches('%').parse::<f32>().ok().map(|v| (Some(v / 100.0 / ppp), false)),
     }
 }
 
@@ -583,7 +586,7 @@ pub(crate) fn resolution_label(res: Resolution, scale: f64) -> String {
 /// transparency grid, mask and shape path visibility, region of interest, grid and guide
 /// options, show channel, reset exposure, exposure, take / show snapshot, Fast Previews, the 3D
 /// renderer and view, and the current time.
-pub(crate) fn bottom_bar(app: &mut EffectcraftApp, ui: &mut egui::Ui, bar: Rect, zoom: f32, fit: f32, time: Tick, comp: &Comp) {
+pub(crate) fn bottom_bar(app: &mut EffectcraftApp, ui: &mut egui::Ui, bar: Rect, zoom: f32, time: Tick, comp: &Comp) {
     let t = app.tokens;
     let p = ui.painter().clone();
     p.rect_filled(bar, 0.0, t.panel_bg);
@@ -599,7 +602,7 @@ pub(crate) fn bottom_bar(app: &mut EffectcraftApp, ui: &mut egui::Ui, bar: Rect,
         egui::ScrollArea::horizontal().id_salt("viewer-controls").auto_shrink([false, false]).show(ui, |ui| {
             let row = Rect::from_min_size(ui.max_rect().min, vec2(bar.width(), 30.0));
             let first_control = app.auto.elements.len();
-            let width = bottom_bar_contents(app, ui, row, zoom, fit, time, comp);
+            let width = bottom_bar_contents(app, ui, row, zoom, time, comp);
             ui.allocate_rect(Rect::from_min_size(row.min, vec2(width, row.height())), Sense::hover());
             if let Some(focused) = ui.ctx().memory(|memory| memory.focused())
                 && app.auto.elements.get(first_control..).is_some_and(|controls| controls.iter().any(|control| control.response_id == Some(focused)))
@@ -612,7 +615,7 @@ pub(crate) fn bottom_bar(app: &mut EffectcraftApp, ui: &mut egui::Ui, bar: Rect,
     });
 }
 
-fn bottom_bar_contents(app: &mut EffectcraftApp, ui: &mut egui::Ui, bar: Rect, zoom: f32, fit: f32, time: Tick, comp: &Comp) -> f32 {
+fn bottom_bar_contents(app: &mut EffectcraftApp, ui: &mut egui::Ui, bar: Rect, zoom: f32, time: Tick, comp: &Comp) -> f32 {
     let t = app.tokens;
     let p = ui.painter().clone();
     let cy = bar.center().y;
@@ -621,8 +624,10 @@ fn bottom_bar_contents(app: &mut EffectcraftApp, ui: &mut egui::Ui, bar: Rect, z
 
     // Magnification.
     let r = Rect::from_min_size(pos2(x, cy - 10.0), vec2(80.0, 20.0));
-    if let Some(z) = magnification_menu(app, ui, r, "vw-mag", "viewer.magnification", "magnification", zoom, app.ui.viewer.zoom, fit) {
+    let fit_up = app.ui.viewer.fit_up_to_100;
+    if let Some((z, up)) = magnification_menu(app, ui, r, "vw-mag", "viewer.magnification", "magnification", zoom, app.ui.viewer.zoom, fit_up) {
         app.ui.viewer.pan = [0.0, 0.0];
+        app.ui.viewer.fit_up_to_100 = up;
         app.ui.viewer.zoom = z;
     }
     x = r.max.x + 4.0;
diff --git a/crates/ui-egui/src/state.rs b/crates/ui-egui/src/state.rs
index 31f94b83..a9ac1639 100644
--- a/crates/ui-egui/src/state.rs
+++ b/crates/ui-egui/src/state.rs
@@ -233,6 +233,8 @@ pub use effectcraft_engine::project::Resolution;
 pub struct ViewerState {
     /// Magnification (1 = 100%); None = fit.
     pub zoom: Option<f32>,
+    /// Fit up to 100%: while fitting (`zoom` is None), the comp is never magnified past 100%.
+    pub fit_up_to_100: bool,
     /// Pan offset in points from the centred position.
     pub pan: [f32; 2],
     pub transparency_grid: bool,
@@ -272,6 +274,7 @@ impl Default for ViewerState {
     fn default() -> Self {
         ViewerState {
             zoom: None,
+            fit_up_to_100: false,
             pan: [0.0, 0.0],
             transparency_grid: false,
             show_masks: true,
diff --git a/crates/ui-egui/tests/ui_viewer.rs b/crates/ui-egui/tests/ui_viewer.rs
index c5289ded..07036ca8 100644
--- a/crates/ui-egui/tests/ui_viewer.rs
+++ b/crates/ui-egui/tests/ui_viewer.rs
@@ -2046,3 +2046,45 @@ fn frame_sits_on_the_physical_pixel_grid() {
         }
     }
 }
+
+/// Magnification ▸ Fit up to 100% keeps fitting as the panel changes size (Maximize Panel), like
+/// Fit, and never magnifies past 100%.
+#[test]
+fn fit_up_to_100_follows_the_maximized_panel() {
+    use effectcraft_ui_egui::dock::PanelKind;
+    let pick = |h: &mut Harness<'_, EffectcraftApp>| {
+        let at = rect(h, "viewer.magnification").center();
+        click(h, at);
+        let at = rect(h, "viewer.magnification.1").center();
+        click(h, at);
+        assert_eq!(h.state().ui.viewer.zoom, None, "a fit mode, not a fixed magnification");
+        assert!(h.state().ui.viewer.fit_up_to_100);
+        h.run_steps(2);
+    };
+    // A comp larger than the panel: it fills the docked panel, then the maximized one.
+    let mut h = Harness::builder().with_size(egui::vec2(1600.0, 1000.0)).build_eframe(|_| {
+        let mut s = Session::default();
+        s.execute("comp.new", json!({"name": "Big", "width": 3840, "height": 2160, "duration": 4})).unwrap();
+        EffectcraftApp::new(s)
+    });
+    h.run_steps(3);
+    pick(&mut h);
+    let docked = rect(&h, "viewer.comp").width();
+    h.state_mut().toggle_maximize(PanelKind::Composition);
+    h.run_steps(3);
+    let area = rect(&h, "viewer.area");
+    let maximized = rect(&h, "viewer.comp");
+    assert!(maximized.width() > docked + 100.0, "{docked} -> {}", maximized.width());
+    assert!(area.contains_rect(maximized), "{maximized:?} in {area:?}");
+    h.state_mut().toggle_maximize(PanelKind::Composition);
+    h.run_steps(3);
+    assert_eq!(rect(&h, "viewer.comp").width(), docked, "and back when the panel is restored");
+    // A comp smaller than the panel stops at 100%.
+    let mut h = harness();
+    pick(&mut h);
+    let ppp = h.ctx.pixels_per_point();
+    assert!(rect(&h, "viewer.comp").width() <= 640.0 / ppp + 0.01);
+    h.state_mut().toggle_maximize(PanelKind::Composition);
+    h.run_steps(3);
+    assert!((rect(&h, "viewer.comp").width() - 640.0 / ppp).abs() < 0.01);
+}