diff --git a/.github/workflows/windows-arm64.yml b/.github/workflows/windows-arm64.yml
index 2a8144a5b..2cedc1a57 100644
--- a/.github/workflows/windows-arm64.yml
+++ b/.github/workflows/windows-arm64.yml
@@ -28,8 +28,8 @@ permissions:
 
 jobs:
   windows-arm64:
-    # Immutable supporting workflow revision until the new install contract lands upstream.
-    uses: storytold/craft-common-actions/.github/workflows/windows-arm64.yml@fa5ef18780cf5e7d5d3b8de068de56cffc83cac5
+    # Intentionally tracked at @main (not SHA-pinned) so org-wide CI improvements, security fixes, and build optimizations propagate without PR churn across all craftapp repos.
+    uses: storytold/craft-common-actions/.github/workflows/windows-arm64.yml@main
     with:
       app-name: effectcraft
       app-dir: EffectCraft
diff --git a/AGENTS.md b/AGENTS.md
index 24abee6a1..24287ff9a 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -144,3 +144,8 @@ as PhotoCraft does with `cargo xtask corpus`.
   GitHub profiles). Never hand-edit `contributors.json`.
 - Maintainers refresh the stats with `python3 ../../craftrules/scripts/contributors.py .` (it also
   re-verifies who wrote each `people.toml` entry; `--check` only verifies).
+
+## CI workflows
+- Workflows in `.github/workflows/` call the shared workflows in [`storytold/craft-common-actions`](https://github.com/storytold/craft-common-actions) at `@main`, with their inputs and secrets. No other jobs: if no shared workflow does what's needed, it doesn't go here.
+- Don't add or change CI in a feature or fix PR. If the existing workflows can't build or test a change, link an existing craft-common-actions issue or PR, or open a new issue, or a PR only for a small fix that is safe for every app and does not increase CI time.
+- Some workflow files here still run their own jobs. Don't add to them. Moving a job into craft-common-actions is its own task, never part of another PR, and the job stays here until a shared workflow runs it.
diff --git a/CLAUDE.md b/CLAUDE.md
index 21f2df36b..7bd0e7422 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -30,3 +30,8 @@ EffectCraft is a clean-room, open-source, pure-Rust motion graphics and visual e
 - For UI work, **look at the result**. Headless (no window, works while the user is busy on the machine): `cargo run -p effectcraft-ui-egui --example snapshot -- --out ui.png --step '{"method":"engine.execute","params":{"command":"layer.select","params":{"layers":["#2"]}}}'` (steps are control-channel requests; `--script steps.jsonl`; `{"method":"snap","params":{"path":…}}` for intermediate shots). Or drive the live app via the control channel and take `ui.screenshot` (needs the window visible on screen).
 - After Effects reference: drive AE via ExtendScript (`osascript -e 'tell application "Adobe After Effects 2026" to DoScriptFile "x.jsx"'`) and capture only AE's window (`screencapture -l <windowid>`); keep captures in `plan/aftereffects/ref/` (gitignored), never commit them, never capture the Home screen.
 - Parallel agents: separate git worktrees and `CARGO_TARGET_DIR=target/agent-<name>`; keep every `Cargo.toml` valid (the `crates/*` glob).
+
+## CI workflows
+- Workflows in `.github/workflows/` call the shared workflows in [`storytold/craft-common-actions`](https://github.com/storytold/craft-common-actions) at `@main`, with their inputs and secrets. No other jobs: if no shared workflow does what's needed, it doesn't go here.
+- Don't add or change CI in a feature or fix PR. If the existing workflows can't build or test a change, link an existing craft-common-actions issue or PR, or open a new issue, or a PR only for a small fix that is safe for every app and does not increase CI time.
+- Some workflow files here still run their own jobs. Don't add to them. Moving a job into craft-common-actions is its own task, never part of another PR, and the job stays here until a shared workflow runs it.
diff --git a/Cargo.lock b/Cargo.lock
index 0fb134ab7..e55969e6f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4293,7 +4293,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7d8fae84b431384b68627d0f9b3b1245fcf9f46f6c0e3dc902e9dce64edd1967"
 dependencies = [
  "libc",
- "windows-sys 0.45.0",
+ "windows-sys 0.61.2",
 ]
 
 [[package]]
@@ -4885,9 +4885,9 @@ dependencies = [
 
 [[package]]
 name = "roxmltree"
-version = "0.21.1"
+version = "0.21.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f1964b10c76125c36f8afe190065a4bf9a87bf324842c05701330bba9f1cacbb"
+checksum = "9da7f59328b09405b181fee1018925fad50f157afb43c0c0f5c522c256dd5907"
 dependencies = [
  "memchr",
 ]
@@ -7470,9 +7470,9 @@ dependencies = [
 
 [[package]]
 name = "zip"
-version = "9.1.0"
+version = "9.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2886b00003a72c4ccee3f42cfc34908d33b2508a74d827dc2a4244706475c704"
+checksum = "1156b39d142a34b999c2310a50455e0cb3760bf7efad0122f796d813bee26ccb"
 dependencies = [
  "crc32fast",
  "flate2",
diff --git a/crates/ui-egui/src/i18n.rs b/crates/ui-egui/src/i18n.rs
index 14afe59cc..7f4a77989 100644
--- a/crates/ui-egui/src/i18n.rs
+++ b/crates/ui-egui/src/i18n.rs
@@ -1874,7 +1874,7 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("comp.settings", "Composition Settings...", "コンポジション設定..."),
     ("comp.setPosterTime", "Set Poster Time", "ポスター時間を設定"),
     ("comp.trimToWorkArea", "Trim Comp to Work Area", "コンポジションをワークエリアにトリミング"),
-    ("comp.cropToRegionOfInterest", "Crop Comp to Region of Interest", "コンポジションを目標範囲にクロップ"),
+    ("comp.cropToRegionOfInterest", "Crop Comp to Region of Interest", "コンポジションを関心領域にクロップ"),
     ("comp.cropToLayerBounds", "Crop Comp to Selected Layer(s) Bounds", "コンポジションを選択レイヤーの境界にクロップ"),
     ("render.addOutputModule", "Add Output Module", "出力モジュールを追加"),
     ("", "Preview", "プレビュー"),
@@ -1927,7 +1927,7 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("layer.mask.reset", "Reset Mask", "マスクをリセット"),
     ("layer.mask.remove", "Remove Mask", "マスクを削除"),
     ("layer.mask.removeAll", "Remove All Masks", "すべてのマスクを削除"),
-    ("track.mask", "Track Mask", "マスクをトラック"),
+    ("track.mask", "Track Mask", "マスクをトラッキング"),
     ("", "Mode", "モード"),
     ("layer.mask.mode", "None", "なし"),
     ("layer.mask.mode", "Add", "加算"),
@@ -1992,8 +1992,8 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("layer.transform", "Fit to Comp Height", "コンポジションの高さに合わせる"),
     ("layer.autoOrient", "Auto-Orient...", "自動方向..."),
     ("", "Time", "時間"),
-    ("layer.enableTimeRemap", "Enable Time Remapping", "タイムリマップ使用可能"),
-    ("layer.timeReverse", "Time-Reverse Layer", "時間反転レイヤー"),
+    ("layer.enableTimeRemap", "Enable Time Remapping", "時間リマップを有効化"),
+    ("layer.timeReverse", "Time-Reverse Layer", "レイヤーを時間反転"),
     ("layer.timeStretch", "Time Stretch...", "時間伸縮..."),
     ("layer.freezeFrame", "Freeze Frame", "フレームを固定"),
     ("layer.freezeOnLastFrame", "Freeze On Last Frame", "最後のフレームで固定"),
@@ -2061,7 +2061,7 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("layer.trackMatte", "Matte with Layer Above", "上のレイヤーをマットにする"),
     ("layer.trackMatte", "Matte with Layer Below", "下のレイヤーをマットにする"),
     ("", "Layer Styles", "レイヤースタイル"),
-    ("layer.style.options", "Layer Style Options...", "レイヤースタイルオプション..."),
+    ("layer.style.options", "Layer Style Options...", "レイヤースタイルのオプション..."),
     ("layer.style.convertToEditable", "Convert to Editable Styles", "編集可能なスタイルに変換"),
     ("layer.style.showAll", "Show All", "すべてを表示"),
     ("layer.style.removeAll", "Remove All", "すべてを削除"),
@@ -2090,7 +2090,7 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("layer.create", "Convert to Editable Text", "編集可能なテキストに変換"),
     ("layer.create", "Create Shapes from Text", "テキストからシェイプを作成"),
     ("layer.create", "Create Masks from Text", "テキストからマスクを作成"),
-    ("layer.create", "Create Shapes from Vector Layer", "ベクトルレイヤーからシェイプを作成"),
+    ("layer.create", "Create Shapes from Vector Layer", "ベクターレイヤーからシェイプを作成"),
     ("layer.create", "Create Keyframes from Data", "データからキーフレームを作成"),
     ("layer.create", "Null Controllers for Positional Points", "位置のポイント用ヌルコントローラー"),
     ("layer.create", "Null Controllers for Path Points", "パスのポイント用ヌルコントローラー"),
@@ -2140,7 +2140,7 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("layer.applyTextPreset", "Jitter", "ジッター"),
     ("layer.applyTextPreset", "Drop In Lines", "行をドロップイン"),
     ("anim.addKeyframe", "Add Keyframe", "キーフレームを追加"),
-    ("keys.toggleHold", "Toggle Hold Keyframe", "停止したキーフレームの切り替え"),
+    ("keys.toggleHold", "Toggle Hold Keyframe", "ホールドキーフレームの切り替え"),
     ("keys.setMuted", "Mute Keyframes", "キーフレームをミュート"),
     ("keys.setMuted", "Unmute Keyframes", "キーフレームのミュートを解除"),
     ("keys.interpolation", "Keyframe Interpolation...", "キーフレーム補間法..."),
@@ -2156,7 +2156,7 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("layer.sequence", "Sequence Layers...", "シーケンスレイヤー..."),
     ("keys.timeReverse", "Time-Reverse Keyframes", "時間反転キーフレーム"),
     ("", "Animate Text", "テキストをアニメート"),
-    ("layer.enablePerChar3D", "Enable Per-character 3D", "文字ごとの3Dを使用可能にする"),
+    ("layer.enablePerChar3D", "Enable Per-character 3D", "文字ごとの3Dを有効化"),
     ("layer.addTextAnimator", "Anchor Point", "アンカーポイント"),
     ("layer.addTextAnimator", "Position", "位置"),
     ("layer.addTextAnimator", "Scale", "スケール"),
@@ -2168,7 +2168,7 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("layer.addTextAnimator", "RGB", "RGB"),
     ("layer.addTextAnimator", "Hue", "色相"),
     ("layer.addTextAnimator", "Saturation", "彩度"),
-    ("layer.addTextAnimator", "Brightness", "明度"),
+    ("layer.addTextAnimator", "Brightness", "明るさ"),
     ("", "Stroke Color", "線のカラー"),
     ("layer.addTextAnimator", "Stroke Width", "線幅"),
     ("", "Front", "前面"),
@@ -2190,12 +2190,12 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("text.removeAllAnimators", "Remove All Text Animators", "すべてのテキストアニメーターを削除"),
     ("prop.setExpression", "Add Expression", "エクスプレッションを追加"),
     ("essential.addProperty", "Add Property to Essential Graphics", "エッセンシャルグラフィックスにプロパティを追加"),
-    ("prop.separateDimensions", "Separate Dimensions", "次元に分割"),
-    ("track.camera", "Track Camera", "カメラをトラック"),
+    ("prop.separateDimensions", "Separate Dimensions", "次元を分離"),
+    ("track.camera", "Track Camera", "カメラをトラッキング"),
     ("track.warpStabilizer", "Warp Stabilizer VFX", "ワープスタビライザーVFX"),
-    ("track.motion", "Track Motion", "モーションをトラック"),
-    ("track.stabilize", "Stabilize Motion", "モーションをスタビライズ"),
-    ("track.property", "Track this Property", "このプロパティをトラック"),
+    ("track.motion", "Track Motion", "モーションをトラッキング"),
+    ("track.stabilize", "Stabilize Motion", "モーションを安定化"),
+    ("track.property", "Track this Property", "このプロパティをトラッキング"),
     ("anim.reveal", "Reveal Properties with Keyframes", "キーフレームのあるプロパティを表示"),
     ("anim.reveal", "Reveal Properties with Animation", "アニメーションのあるプロパティを表示"),
     ("anim.reveal", "Reveal All Modified Properties", "変更されたすべてのプロパティを表示"),
@@ -2275,7 +2275,7 @@ const JAPANESE: &[(&str, &str, &str)] = &[
     ("window.workspace", "Default", "初期設定"),
     ("window.workspace", "Review", "レビュー"),
     ("window.workspace", "Learn", "学習"),
-    ("window.workspace", "Small Screen", "小画面"),
+    ("window.workspace", "Small Screen", "小さい画面"),
     ("window.workspace", "Standard", "標準"),
     ("window.workspace", "All Panels", "すべてのパネル"),
     ("window.workspace", "Animation", "アニメーション"),
diff --git a/crates/ui-egui/src/i18n/ui.rs b/crates/ui-egui/src/i18n/ui.rs
index c137204e6..fde48fbe6 100644
--- a/crates/ui-egui/src/i18n/ui.rs
+++ b/crates/ui-egui/src/i18n/ui.rs
@@ -455,7 +455,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("None", "なし"),
     ("Not applied: tick it in the list to add it.", "未適用：リストでチェックを入れると追加されます。"),
     ("Not assigned", "未割り当て"),
-    ("Note: Shadows are only cast from layers with Cast Shadows enabled.", "注意：シャドウは「シャドウを投影」が有効なレイヤーからのみ投影されます。"),
+    ("Note: Shadows are only cast from layers with Cast Shadows enabled.", "注意：「シャドウを落とす」が有効なレイヤーだけがシャドウを落とします。"),
     ("Notify", "通知"),
     ("OK", "OK"),
     ("Offset:", "オフセット:"),
@@ -537,7 +537,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("Select a command to change its shortcut.", "ショートカットを変更するコマンドを選択してください。"),
     ("Select a layer to see its effects", "レイヤーを選択するとエフェクトが表示されます"),
     ("Select a layer to see its properties", "レイヤーを選択するとプロパティが表示されます"),
-    ("({}) Selected Objects", "({}) 個の選択されたオブジェクト"),
+    ("({}) Selected Objects", "選択したオブジェクト（{}）"),
     (
         "Select a layer with a mask or shape path (or the path property), or Puppet pins.",
         "マスクまたはシェイプパスのあるレイヤー（またはパスプロパティ）か、パペットピンを選択してください。",
@@ -685,7 +685,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("Import Image Sequence", "画像シーケンスを読み込み"),
     ("Import PDF / Illustrator File", "PDF / Illustratorファイルを読み込み"),
     ("Import Photoshop File", "Photoshopファイルを読み込み"),
-    ("Interpret Unlabeled Alpha As", "ラベルのないアルファを変換"),
+    ("Interpret Unlabeled Alpha As", "ラベルのないアルファの解釈"),
     ("Join the ArtCraft Discord", "ArtCraftのDiscordに参加"),
     ("Mercury GPU Acceleration ({})", "Mercury GPUアクセラレーション（{}）"),
     ("Mercury Software Only", "Mercuryソフトウェアのみ"),
@@ -803,7 +803,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("Cycle Mask Colors", "新規マスクに別のカラーを使用"),
     ("Use Gradients", "グラデーションを使用"),
     ("Menu Bar", "メニューバー"),
-    ("Grids & Guides", "グリッド＆ガイド"),
+    ("Grids & Guides", "グリッドとガイド"),
     ("Gridline Every", "グリッドの間隔"),
     ("Subdivisions", "分割数"),
     ("Style", "スタイル"),
@@ -835,7 +835,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("Ask User", "ユーザーに確認"),
     ("Guess", "推測"),
     ("Ignore", "無視"),
-    ("Straight", "そのまま"),
+    ("Straight", "ストレート"),
     ("Premultiplied", "プリマルチプライ"),
     ("Default Drag Import As", "複数アイテムのドラッグ読み込みの初期設定"),
     ("Footage", "フッテージ"),
@@ -885,7 +885,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("Scripting & Expressions", "スクリプトとエクスプレッション"),
     ("Application Scripting", "アプリケーションのスクリプト"),
     ("Allow Scripts to Write Files and Access Network", "スクリプトによるファイルへの書き込みとネットワークへのアクセスを許可"),
-    ("Warn User When Executing Files", "ファイルの実行時にカーソルに警告"),
+    ("Warn User When Executing Files", "ファイルの実行時にユーザーに警告"),
     ("Enable JavaScript Debugger", "JavaScript デバッガーを使用"),
     ("Expressions Editor", "エクスプレッションエディター"),
     ("Font Size", "フォントサイズ"),
@@ -894,7 +894,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("Auto-complete", "オートコンプリート"),
     ("Bracket Matching", "対応する括弧をハイライト"),
     ("Word Wrap", "折り返し"),
-    ("Show Expression Error Banner", "式のエラーがある場合に警告バナーを表示"),
+    ("Show Expression Error Banner", "エクスプレッションのエラーがある場合に警告バナーを表示"),
     (
         "Expressions use the JavaScript engine. Script errors report their file and line in the Script Console; there is no step debugger.",
         "エクスプレッションはJavaScriptエンジンを使用します。スクリプトのエラーはファイルと行をスクリプトコンソールに報告します。ステップ実行デバッガーはありません。",
@@ -1003,8 +1003,8 @@ const JAPANESE: &[(&str, &str)] = &[
     ("Create Shapes from Vector Layer", "ベクターレイヤーからシェイプを作成"),
     ("Create Shapes from Text", "テキストからシェイプを作成"),
     ("Create Masks from Text", "テキストからマスクを作成"),
-    ("New Mask", "新しいマスク"),
-    ("Center In View", "ビュー内で中央揃え"),
+    ("New Mask", "新規マスク"),
+    ("Center In View", "ビューの中央に配置"),
     ("Fit to Comp", "コンポジションに合わせる"),
     ("Flip Horizontal", "水平方向に反転"),
     ("Flip Vertical", "垂直方向に反転"),
@@ -1033,8 +1033,8 @@ const JAPANESE: &[(&str, &str)] = &[
     ("All Transform Properties", "すべてのトランスフォームプロパティ"),
     ("Line Anchor", "行のアンカー"),
     ("Line Spacing", "行間"),
-    ("Character Offset", "文字オフセット"),
-    ("Character Value", "文字値"),
+    ("Character Offset", "文字のオフセット"),
+    ("Character Value", "文字の値"),
     ("Fill Color: RGB", "塗りの色: RGB"),
     ("Fill Color: Hue", "塗りの色: 色相"),
     ("Fill Color: Saturation", "塗りの色: 彩度"),
@@ -1060,7 +1060,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("ScriptUI Panel", "ScriptUI パネル"),
     ("Lumetri Scopes", "Lumetri スコープ"),
     ("Media Browser", "メディアブラウザー"),
-    ("Content-Aware Fill", "コンテンツに応じた塗り"),
+    ("Content-Aware Fill", "コンテンツに応じた塗りつぶし"),
     ("Create Nulls From Paths", "パスからヌルを作成"),
     ("VR Comp Editor", "VR コンポジションエディター"),
     ("Media Duration", "メディアの長さ"),
@@ -1095,7 +1095,7 @@ const JAPANESE: &[(&str, &str)] = &[
     ("Background Color", "背景色"),
     ("Basic", "基本"),
     ("Shutter Angle", "シャッター角度"),
-    ("Shutter Phase", "シャッター位相"),
+    ("Shutter Phase", "シャッターフェーズ"),
     ("Samples Per Frame", "フレームあたりのサンプル数"),
     ("Adaptive Sample Limit", "適応サンプル数の上限"),
     ("X and Y", "X と Y"),
diff --git a/crates/ui-egui/src/panels/markers_ui.rs b/crates/ui-egui/src/panels/markers_ui.rs
index cc08f223d..03c45d32b 100644
--- a/crates/ui-egui/src/panels/markers_ui.rs
+++ b/crates/ui-egui/src/panels/markers_ui.rs
@@ -296,21 +296,13 @@ fn marker(app: &mut EffectcraftApp, ui: &mut egui::Ui, p: &egui::Painter, comp:
                 hx += 5.0;
             }
         }
-        p.line_segment([pos2(xe, y0), pos2(xe, y0 + h)], Stroke::new(1.0, col));
     }
-    p.add(egui::Shape::convex_polygon(marker_shape(x, y0, h), col, Stroke::NONE));
     if !m.comment.is_empty() {
         // The name sits in a small outlined box beside the flag, as in After Effects. It is drawn in the theme's field
         // colours, so it follows Dark, Darker and Light.
         let galley = p.layout_no_wrap(m.comment.lines().next().unwrap_or_default().to_string(), Tokens::ui(10.0), t.text);
-        let (box_w, mut box_x) = (galley.size().x + 8.0, x + 6.0);
-        // A duration that ends under the box would be hidden by its fill: the box steps past the end cap instead.
-        if let Some(xe) = end
-            && xe > box_x
-            && xe < box_x + box_w
-        {
-            box_x = xe + 3.0;
-        }
+        let box_w = galley.size().x + 8.0;
+        let box_x = name_box_x(x, box_w, end, p.clip_rect());
         let box_rect = Rect::from_min_size(pos2(box_x, y0), vec2(box_w, h.max(galley.size().y + 2.0)));
         p.rect(box_rect, t.radius_sm, t.field_bg, Stroke::new(1.0, t.field_border), egui::StrokeKind::Inside);
         p.galley(pos2(box_rect.min.x + 4.0, box_rect.center().y - galley.size().y / 2.0), galley, t.text);
@@ -385,6 +377,33 @@ fn marker(app: &mut EffectcraftApp, ui: &mut egui::Ui, p: &egui::Painter, comp:
     });
 }
 
+fn name_box_x(x: f32, width: f32, end: Option<f32>, clip: Rect) -> f32 {
+    let start = x + 6.0;
+    let right = match end {
+        Some(end) if end > start && end < start + width => end + 3.0,
+        _ => start,
+    };
+    if right + width <= clip.right() {
+        return right;
+    }
+    let left = x - 6.0 - width;
+    if left >= clip.left() {
+        return left;
+    }
+    start
+}
+
+/// Flags and duration handles sit above every name box in their marker strip.
+fn marker_glyphs(p: &egui::Painter, tokens: &Tokens, tm: TMap, marker: &Marker, time: f64, y0: f32, y1: f32) {
+    let color = marker_color(tokens, marker.label);
+    let h = (y1 - y0).min(10.0);
+    p.add(egui::Shape::convex_polygon(marker_shape(tm.x(time), y0, h), color, Stroke::NONE));
+    if marker.duration > Tick(0) {
+        let end = tm.x(time + marker.duration.seconds());
+        p.line_segment([pos2(end, y0), pos2(end, y0 + h)], Stroke::new(1.0, color));
+    }
+}
+
 /// Composition markers in the ruler strip `[y0, y1]`, protected regions over `rows`.
 pub(crate) fn comp_markers(app: &mut EffectcraftApp, ui: &mut egui::Ui, comp: &Comp, tm: TMap, strip: Rect, rows: Rect) {
     let p = ui.painter().with_clip_rect(strip);
@@ -398,6 +417,9 @@ pub(crate) fn comp_markers(app: &mut EffectcraftApp, ui: &mut egui::Ui, comp: &C
     for (i, m) in comp.markers.iter().enumerate() {
         marker(app, ui, &p, comp, tm, m, m.time.seconds(), MarkerRef { layer: None, index: i }, strip.min.y, strip.max.y);
     }
+    for m in &comp.markers {
+        marker_glyphs(&p, &app.tokens, tm, m, m.time.seconds(), strip.min.y, strip.max.y);
+    }
 }
 
 /// The composition marker bin at the right end of the time ruler (`bin`), as in After Effects
@@ -439,6 +461,9 @@ pub(crate) fn layer_markers(app: &mut EffectcraftApp, ui: &mut egui::Ui, clip: R
     for (i, m) in layer.markers.iter().enumerate() {
         marker(app, ui, &p, comp, tm, m, layer.comp_time(m.time).seconds(), MarkerRef { layer: Some(layer.id.0), index: i }, r.min.y + 3.0, r.max.y - 3.0);
     }
+    for m in &layer.markers {
+        marker_glyphs(&p, &app.tokens, tm, m, layer.comp_time(m.time).seconds(), r.min.y + 3.0, r.max.y - 3.0);
+    }
 }
 
 /// The nested comp's markers on a precomp layer's bar (`markers.nested`).
@@ -488,6 +513,21 @@ fn nested_markers(app: &mut EffectcraftApp, ui: &mut egui::Ui, p: &egui::Painter
 mod tests {
     use super::*;
 
+    #[test]
+    fn duration_name_box_stays_visible_near_the_right_clip_edge() {
+        let clip = Rect::from_min_max(pos2(0.0, 0.0), pos2(100.0, 20.0));
+        let x = name_box_x(70.0, 20.0, Some(85.0), clip);
+        assert!(x >= clip.left() && x + 20.0 <= clip.right());
+        assert!(x + 20.0 < 70.0 - 4.0, "the left-hand box must not cover its own marker flag");
+        assert!(85.0 < x || 85.0 > x + 20.0, "the end cap must remain outside the box");
+        assert_eq!(name_box_x(20.0, 20.0, Some(35.0), clip), 38.0);
+        for end in [None, Some(72.0), Some(110.0)] {
+            let x = name_box_x(90.0, 20.0, end, clip);
+            assert!(x >= clip.left() && x + 20.0 <= clip.right(), "all right-edge names must remain visible: {end:?}");
+            assert!(x + 20.0 < 90.0 - 4.0);
+        }
+    }
+
     #[test]
     fn marker_dialog_reads_and_writes_every_field() {
         let mut s = effectcraft_engine::Session::default();
diff --git a/crates/ui-egui/tests/it/gpu_test.rs b/crates/ui-egui/tests/it/gpu_test.rs
new file mode 100644
index 000000000..0156fbb4d
--- /dev/null
+++ b/crates/ui-egui/tests/it/gpu_test.rs
@@ -0,0 +1,43 @@
+//! Shared device-creation gate for the integration-test executable.
+
+static GPU_TEST_LOCK: std::sync::Mutex<()> = std::sync::Mutex::new(());
+
+thread_local! {
+    static HELD: std::cell::Cell<bool> = const { std::cell::Cell::new(false) };
+}
+
+pub(crate) struct Guard {
+    held: Option<std::sync::MutexGuard<'static, ()>>,
+}
+
+impl Drop for Guard {
+    fn drop(&mut self) {
+        if self.held.is_some() {
+            HELD.with(|held| held.set(false));
+        }
+    }
+}
+
+/// GPU-backed harnesses hold this for their whole test; screenshots may enter it again.
+pub(crate) fn lock() -> Guard {
+    let held = if HELD.with(std::cell::Cell::get) {
+        None
+    } else {
+        let guard = GPU_TEST_LOCK.lock().unwrap_or_else(std::sync::PoisonError::into_inner);
+        HELD.with(|held| held.set(true));
+        Some(guard)
+    };
+    Guard { held }
+}
+
+/// Plain harnesses create their GPU renderer lazily on the first screenshot.
+pub(crate) trait RenderSerial {
+    fn render_serialized(&mut self) -> Result<image::RgbaImage, String>;
+}
+
+impl<State> RenderSerial for egui_kittest::Harness<'_, State> {
+    fn render_serialized(&mut self) -> Result<image::RgbaImage, String> {
+        let _device = lock();
+        self.render().map_err(|error| format!("{error:?}"))
+    }
+}
diff --git a/crates/ui-egui/tests/it/main.rs b/crates/ui-egui/tests/it/main.rs
index 7d38e3089..17fe06cae 100644
--- a/crates/ui-egui/tests/it/main.rs
+++ b/crates/ui-egui/tests/it/main.rs
@@ -1,5 +1,6 @@
 //! The crate's integration tests, one binary (each module is a former `tests/<name>.rs`).
 
+mod gpu_test;
 mod native_menu_text_keys;
 mod render_queue_snapshot;
 mod shared_docking_ui;
diff --git a/crates/ui-egui/tests/it/render_queue_snapshot.rs b/crates/ui-egui/tests/it/render_queue_snapshot.rs
index d054511af..27054119d 100644
--- a/crates/ui-egui/tests/it/render_queue_snapshot.rs
+++ b/crates/ui-egui/tests/it/render_queue_snapshot.rs
@@ -2,6 +2,7 @@
 //! adapter); run with
 //! `RQ_SNAPSHOT=/abs/out.png cargo test -p effectcraft-ui-egui --test it render_queue_snapshot:: -- --ignored`.
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::project::render_queue::RenderStatus;
 use effectcraft_ui_egui::EffectcraftApp;
@@ -34,7 +35,7 @@ fn render_queue_panel_snapshot() {
     h.ctx.data_mut(|d| d.insert_temp(egui::Id::unique("rq-ui"), (ids, None::<u64>)));
     h.state_mut().show_panel(effectcraft_ui_egui::dock::PanelKind::RenderQueue);
     h.run_steps(4);
-    let img = h.render().expect("render");
+    let img = h.render_serialized().expect("render");
     let out = std::env::var("RQ_SNAPSHOT").unwrap_or_else(|_| concat!(env!("CARGO_MANIFEST_DIR"), "/../../target/test-out/render_queue.png").into());
     if let Some(d) = std::path::Path::new(&out).parent() {
         std::fs::create_dir_all(d).unwrap();
@@ -57,7 +58,7 @@ fn templates_dialog_snapshot() {
     let mut h = Harness::builder().with_size(egui::vec2(1400.0, 900.0)).build_eframe(|_| app.take().expect("app"));
     h.run_steps(4);
     assert!(h.state().dialog.is_some(), "the Templates dialog is open");
-    let img = h.render().expect("render");
+    let img = h.render_serialized().expect("render");
     let out = std::env::var("RQ_TEMPLATES_SNAPSHOT").unwrap_or_else(|_| concat!(env!("CARGO_MANIFEST_DIR"), "/../../target/test-out/rq_templates.png").into());
     if let Some(d) = std::path::Path::new(&out).parent() {
         std::fs::create_dir_all(d).unwrap();
diff --git a/crates/ui-egui/tests/it/ui_3d.rs b/crates/ui-egui/tests/it/ui_3d.rs
index a654f745c..0f7a10b7e 100644
--- a/crates/ui-egui/tests/it/ui_3d.rs
+++ b/crates/ui-egui/tests/it/ui_3d.rs
@@ -2,6 +2,7 @@
 //! with wgpu and writes PNGs when `EC_SNAPSHOT_DIR` is set (`cargo test -p effectcraft-ui-egui
 //! --test it ui_3d:: -- --ignored`); the other test only runs the UI logic.
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::render::three_d::View3D;
 use effectcraft_ui_egui::EffectcraftApp;
@@ -109,6 +110,7 @@ fn camera_and_light_dialogs_create_layers() {
 #[test]
 #[ignore = "renders with wgpu; run with --ignored (set EC_SNAPSHOT_DIR to keep PNGs)"]
 fn snapshot() {
+    let _device = crate::gpu_test::lock();
     let dir = std::env::var("EC_SNAPSHOT_DIR").ok();
     let mut h = Harness::builder().with_size(egui::vec2(1600.0, 1000.0)).with_pixels_per_point(1.0).wgpu().build_eframe(|_| app());
     let shots: [(&str, Option<&str>); 4] =
@@ -118,7 +120,7 @@ fn snapshot() {
             h.state_mut().session.execute(c, json!({})).unwrap();
         }
         settle(&mut h);
-        let img = h.render().expect("render");
+        let img = h.render_serialized().expect("render");
         if let Some(d) = &dir {
             img.save(format!("{d}/ui3d_{name}.png")).unwrap();
         }
@@ -126,14 +128,14 @@ fn snapshot() {
     let ctx = h.ctx.clone();
     effectcraft_ui_egui::menus::invoke(h.state_mut(), &ctx, "layer.newCamera", json!({})).unwrap();
     h.run_steps(3);
-    let img = h.render().expect("render");
+    let img = h.render_serialized().expect("render");
     if let Some(d) = &dir {
         img.save(format!("{d}/ui3d_camera_dialog.png")).unwrap();
     }
     h.state_mut().dialog = None;
     effectcraft_ui_egui::menus::invoke(h.state_mut(), &ctx, "layer.newLight", json!({})).unwrap();
     h.run_steps(3);
-    let img = h.render().expect("render");
+    let img = h.render_serialized().expect("render");
     if let Some(d) = &dir {
         img.save(format!("{d}/ui3d_light_dialog.png")).unwrap();
     }
@@ -143,7 +145,7 @@ fn snapshot() {
     h.state_mut().session.execute("layer.select", json!({"layers": ["Card Blue"]})).unwrap();
     effectcraft_ui_egui::menus::invoke(h.state_mut(), &ctx, "timeline.reveal.rotation", json!({})).unwrap();
     settle(&mut h);
-    let img = h.render().expect("render");
+    let img = h.render_serialized().expect("render");
     if let Some(d) = &dir {
         img.save(format!("{d}/ui3d_reveal_rotation.png")).unwrap();
     }
diff --git a/crates/ui-egui/tests/it/ui_blank_context_menus.rs b/crates/ui-egui/tests/it/ui_blank_context_menus.rs
index 52417326f..84080be08 100644
--- a/crates/ui-egui/tests/it/ui_blank_context_menus.rs
+++ b/crates/ui-egui/tests/it/ui_blank_context_menus.rs
@@ -1,4 +1,5 @@
 //! Right-click actions in the blank Project and Timeline areas, and on Timeline property names.
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::project::ItemKind;
 use effectcraft_ui_egui::dock::WorkspaceExt as _;
@@ -20,7 +21,7 @@ fn rect(h: &Harness<'_, EffectcraftApp>, id: &str) -> Rect {
 }
 fn snapshot(h: &mut Harness<'_, EffectcraftApp>, name: &str) {
     if let Ok(dir) = std::env::var("BLANK_CONTEXT_MENU_SNAPSHOTS") {
-        h.render().unwrap().save(format!("{dir}/{name}.png")).unwrap();
+        h.render_serialized().unwrap().save(format!("{dir}/{name}.png")).unwrap();
     }
 }
 fn right_click(h: &mut Harness<'_, EffectcraftApp>, p: Pos2) {
diff --git a/crates/ui-egui/tests/it/ui_camera_tracker.rs b/crates/ui-egui/tests/it/ui_camera_tracker.rs
index 8c4be61a7..619d7c7c5 100644
--- a/crates/ui-egui/tests/it/ui_camera_tracker.rs
+++ b/crates/ui-egui/tests/it/ui_camera_tracker.rs
@@ -3,6 +3,7 @@
 //! The solve is a synthetic one written into the effect (the analysis itself is tested in the
 //! engine and track crates).
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::effects::camera_tracker as ct;
 use effectcraft_engine::track::camtrack::{CameraSolve, ShotType, SolveMethod, SolvedFrame, SolvedPoint};
@@ -186,6 +187,7 @@ fn blender_export_button_opens_python_dialog_and_writes_scene() {
     let shot = std::env::var("EFFECTCRAFT_BLENDER_UI_SNAPSHOT").ok();
     let builder = Harness::builder().with_size(egui::vec2(1600.0, 1000.0));
     let builder = if shot.is_some() { builder.wgpu() } else { builder };
+    let _device = shot.is_some().then(crate::gpu_test::lock);
     let mut h = builder.build_eframe(|_| a);
     h.state_mut().show_panel(PanelKind::EffectControls);
     h.run_steps(5);
@@ -272,6 +274,7 @@ fn settle(h: &mut Harness<'_, EffectcraftApp>) {
 #[test]
 #[ignore = "analyses the demo's 3D Showcase and renders with wgpu; run with --ignored (set EC_SNAPSHOT_DIR to keep PNGs)"]
 fn snapshot_showcase_track() {
+    let _device = crate::gpu_test::lock();
     let dir = std::env::var("EC_SNAPSHOT_DIR").ok();
     let mut s = Session::default();
     s.execute("file.openDemoProject", json!({})).unwrap();
@@ -290,7 +293,7 @@ fn snapshot_showcase_track() {
     h.input_mut().events.push(egui::Event::PointerMoved(r.center() + egui::vec2(12.0, 12.0)));
     h.run_steps(2);
     if let Some(d) = &dir {
-        h.render().expect("render").save(format!("{d}/camera_tracker_hover.png")).unwrap();
+        h.render_serialized().expect("render").save(format!("{d}/camera_tracker_hover.png")).unwrap();
     }
     let sel: Vec<u64> = pts.iter().take(5).filter_map(|i| i.rsplit('.').next()?.parse().ok()).collect();
     h.state_mut().session.execute("camera.selectPoints", json!({"points": sel})).unwrap();
@@ -298,6 +301,6 @@ fn snapshot_showcase_track() {
     h.state_mut().session.execute("layer.select", json!({"layers": ["#3"]})).unwrap();
     settle(&mut h);
     if let Some(d) = &dir {
-        h.render().expect("render").save(format!("{d}/camera_tracker_solid.png")).unwrap();
+        h.render_serialized().expect("render").save(format!("{d}/camera_tracker_solid.png")).unwrap();
     }
 }
diff --git a/crates/ui-egui/tests/it/ui_character_eyedropper.rs b/crates/ui-egui/tests/it/ui_character_eyedropper.rs
index ea2578a0d..ea4eecd99 100644
--- a/crates/ui-egui/tests/it/ui_character_eyedropper.rs
+++ b/crates/ui-egui/tests/it/ui_character_eyedropper.rs
@@ -1,4 +1,5 @@
 //! Character Fill and Stroke can sample a displayed Composition pixel.
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::{Session, commands::text_edit::layer_doc, project::LayerId};
 use effectcraft_ui_egui::{
     EffectcraftApp,
@@ -37,6 +38,7 @@ fn settle(h: &mut Harness<'_, EffectcraftApp>) {
 
 #[test]
 fn character_fill_eyedropper_samples_viewer_and_keeps_text_selection() {
+    let _device = crate::gpu_test::lock();
     let mut s = Session::default();
     s.execute("comp.new", json!({"width": 320, "height": 180, "duration": 2})).unwrap();
     s.execute("layer.newSolid", json!({"name": "Background", "color": "#20c040"})).unwrap();
@@ -64,6 +66,7 @@ fn character_fill_eyedropper_samples_viewer_and_keeps_text_selection() {
 
 #[test]
 fn character_stroke_eyedropper_samples_viewer() {
+    let _device = crate::gpu_test::lock();
     let mut s = Session::default();
     s.execute("comp.new", json!({"width": 320, "height": 180, "duration": 2})).unwrap();
     s.execute("layer.newSolid", json!({"name": "brat green", "color": "#8ACE00"})).unwrap();
@@ -79,7 +82,7 @@ fn character_stroke_eyedropper_samples_viewer() {
     settle(&mut h);
     click_auto(&mut h, "character.stroke.eyedropper");
     if let Ok(dir) = std::env::var("EC_SNAPSHOT_DIR") {
-        h.render().unwrap().save(format!("{dir}/character-eyedropper.png")).unwrap();
+        h.render_serialized().unwrap().save(format!("{dir}/character-eyedropper.png")).unwrap();
     }
     let sample = comp_to_screen(&h.ctx, [20.0, 20.0]).unwrap();
     click(&mut h, sample);
diff --git a/crates/ui-egui/tests/it/ui_dock_resize.rs b/crates/ui-egui/tests/it/ui_dock_resize.rs
index 863fe697e..11ca740cb 100644
--- a/crates/ui-egui/tests/it/ui_dock_resize.rs
+++ b/crates/ui-egui/tests/it/ui_dock_resize.rs
@@ -1,5 +1,6 @@
 //! Shared pane resizing in the full application, including application shortcut ownership.
 
+use crate::gpu_test::RenderSerial;
 use craft_ui::docking::{Divider, DockArea, Hit};
 use effectcraft_engine::Session;
 use effectcraft_ui_egui::EffectcraftApp;
@@ -16,7 +17,7 @@ fn snapshots(h: &mut Harness<'_, EffectcraftApp>, directory: Option<&std::path::
         let ctx = h.ctx.clone();
         h.state_mut().set_theme(&ctx, theme);
         h.run_steps(3);
-        h.render().unwrap().save(directory.join(format!("effectcraft-{phase}-{name}.png"))).unwrap();
+        h.render_serialized().unwrap().save(directory.join(format!("effectcraft-{phase}-{name}.png"))).unwrap();
     }
     let ctx = h.ctx.clone();
     h.state_mut().set_theme(&ctx, ThemeKind::Dark);
@@ -32,6 +33,7 @@ fn first_size(h: &Harness<'_, EffectcraftApp>) -> f32 {
 
 #[test]
 fn focused_dock_resize_owns_arrows_and_keeps_pointer_dragging() {
+    let _device = crate::gpu_test::lock();
     let mut session = Session::default();
     session.execute("comp.new", json!({"name": "Split test", "width": 160, "height": 90, "duration": 1})).unwrap();
     session.execute("layer.newSolid", json!({"name": "Selected", "color": [1.0, 0.0, 0.0, 1.0]})).unwrap();
diff --git a/crates/ui-egui/tests/it/ui_env_light_gpu.rs b/crates/ui-egui/tests/it/ui_env_light_gpu.rs
index e88f0a2a4..185980fb6 100644
--- a/crates/ui-egui/tests/it/ui_env_light_gpu.rs
+++ b/crates/ui-egui/tests/it/ui_env_light_gpu.rs
@@ -44,6 +44,7 @@ fn same_adapter(name: String) -> eframe::egui_wgpu::WgpuSetup {
 /// viewer's GPU frames change when the light is added.
 #[test]
 fn environment_light_lights_the_scene_on_the_gpu() {
+    let _device = crate::gpu_test::lock();
     let Some(probe) = effectcraft_gpu::Gpu::headless() else {
         eprintln!("no GPU adapter: skipping");
         return;
diff --git a/crates/ui-egui/tests/it/ui_font_search.rs b/crates/ui-egui/tests/it/ui_font_search.rs
index 77984cf6b..44b650be4 100644
--- a/crates/ui-egui/tests/it/ui_font_search.rs
+++ b/crates/ui-egui/tests/it/ui_font_search.rs
@@ -1,4 +1,5 @@
 //! Real keyboard/pointer coverage for the font menus in both text panels.
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::{Session, commands::text_edit::layer_doc, project::LayerId};
 use effectcraft_ui_egui::{EffectcraftApp, dock::PanelKind};
 use egui::{Event, Key, Modifiers, PointerButton};
@@ -29,6 +30,7 @@ fn type_text(h: &mut Harness<'_, EffectcraftApp>, text: &str) {
 
 #[test]
 fn font_search_filters_selects_and_undoes_in_both_panels() {
+    let _device = crate::gpu_test::lock();
     for (panel, prefix) in [(PanelKind::Character, "character.font"), (PanelKind::Properties, "properties.text.font")] {
         let mut s = Session::default();
         s.execute("comp.new", json!({"width": 320, "height": 180})).unwrap();
@@ -56,7 +58,7 @@ fn font_search_filters_selects_and_undoes_in_both_panels() {
         assert!(!rows.is_empty());
         assert!(rows.iter().all(|r| r.label.to_lowercase().contains("jetbrains")));
         if let Ok(dir) = std::env::var("EC_SNAPSHOT_DIR") {
-            h.render().unwrap().save(format!("{dir}/{prefix}-search.png")).unwrap();
+            h.render_serialized().unwrap().save(format!("{dir}/{prefix}-search.png")).unwrap();
         }
         assert_eq!(layer_doc(&h.state().session, LayerId(lid)).unwrap().font, "Inter", "typing only filters");
         key(&mut h, Key::Enter);
@@ -76,7 +78,7 @@ fn font_search_filters_selects_and_undoes_in_both_panels() {
         // Reopening clears the previous query, and mouse selection still works.
         h.run_steps(2);
         if let Ok(dir) = std::env::var("EC_SNAPSHOT_DIR") {
-            h.render().unwrap().save(format!("{dir}/{prefix}-reopened.png")).unwrap();
+            h.render_serialized().unwrap().save(format!("{dir}/{prefix}-reopened.png")).unwrap();
         }
         assert!(h.state().auto.query(&format!("{prefix}.option.")).len() > 1);
         type_text(&mut h, "JetBrains");
diff --git a/crates/ui-egui/tests/it/ui_gpu.rs b/crates/ui-egui/tests/it/ui_gpu.rs
index 643d99492..d5d432db3 100644
--- a/crates/ui-egui/tests/it/ui_gpu.rs
+++ b/crates/ui-egui/tests/it/ui_gpu.rs
@@ -53,6 +53,7 @@ fn small_session() -> Session {
 /// composites on the CPU. The worker is held on a gate so the "preparing" state is observable.
 #[test]
 fn the_interface_draws_and_composites_on_the_cpu_while_the_gpu_compositor_is_built() {
+    let _device = crate::gpu_test::lock();
     if !any_adapter() {
         eprintln!("no wgpu adapter: skipping");
         return;
@@ -111,6 +112,7 @@ fn the_interface_draws_and_composites_on_the_cpu_while_the_gpu_compositor_is_bui
 /// thread, not under the UI: the window keeps drawing on the CPU and says why.
 #[test]
 fn a_compositor_build_that_panics_leaves_the_viewer_on_the_cpu() {
+    let _device = crate::gpu_test::lock();
     if !any_adapter() {
         eprintln!("no wgpu adapter: skipping");
         return;
@@ -153,6 +155,7 @@ fn same_adapter(name: String) -> eframe::egui_wgpu::WgpuSetup {
 
 #[test]
 fn viewer_draws_gpu_frames_that_match_the_cpu() {
+    let _device = crate::gpu_test::lock();
     let Some(probe) = effectcraft_gpu::Gpu::headless() else {
         eprintln!("no GPU adapter: skipping");
         return;
diff --git a/crates/ui-egui/tests/it/ui_guide_layers.rs b/crates/ui-egui/tests/it/ui_guide_layers.rs
index 37158658f..92196f5f1 100644
--- a/crates/ui-egui/tests/it/ui_guide_layers.rs
+++ b/crates/ui-egui/tests/it/ui_guide_layers.rs
@@ -1,6 +1,7 @@
 //! Guide Layer in the layer context menus (Timeline rows and the Composition viewer), a plain item
 //! (no check mark) that toggles the switch on the selection, and the guide mark by a guide layer's
 //! name.
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::project::LayerId;
 use effectcraft_ui_egui::EffectcraftApp;
@@ -45,7 +46,7 @@ fn guide(h: &Harness<'_, EffectcraftApp>, id: LayerId) -> bool {
 
 fn snapshot(h: &mut Harness<'_, EffectcraftApp>, name: &str) {
     if let Ok(dir) = std::env::var("GUIDE_LAYER_SNAPSHOTS") {
-        h.render().unwrap().save(format!("{dir}/{name}.png")).unwrap();
+        h.render_serialized().unwrap().save(format!("{dir}/{name}.png")).unwrap();
     }
 }
 
diff --git a/crates/ui-egui/tests/it/ui_layer_source_picker.rs b/crates/ui-egui/tests/it/ui_layer_source_picker.rs
index 78a0f8821..ca10e4249 100644
--- a/crates/ui-egui/tests/it/ui_layer_source_picker.rs
+++ b/crates/ui-egui/tests/it/ui_layer_source_picker.rs
@@ -3,6 +3,7 @@
 //! Effect Controls' layer parameters (a Displacement Map's layer) pick through the same widget,
 //! and both write an undoable `prop.set`.
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::keyframe::Value;
 use effectcraft_engine::project::LayerId;
@@ -183,6 +184,7 @@ fn effect_controls_layer_param_picks_through_the_shared_widget() {
 #[test]
 #[ignore = "renders with wgpu; run with --ignored (set EC_SNAPSHOT_DIR to keep PNGs)"]
 fn snapshot_source_dropdown_open_and_chosen() {
+    let _device = crate::gpu_test::lock();
     let mut s = Session::default();
     s.execute("comp.new", json!({"name": "Main", "width": 1280, "height": 720, "frameRate": 30, "duration": 5})).unwrap();
     s.execute("comp.settings", json!({"renderer": "advanced3D"})).unwrap();
@@ -200,7 +202,7 @@ fn snapshot_source_dropdown_open_and_chosen() {
     h.run_steps(4);
     let save = |h: &mut Harness<'_, EffectcraftApp>, name: &str| {
         if let Ok(dir) = std::env::var("EC_SNAPSHOT_DIR") {
-            h.render().expect("render").save(format!("{dir}/{name}")).expect("save");
+            h.render_serialized().expect("render").save(format!("{dir}/{name}")).expect("save");
         }
     };
     save(&mut h, "source_unset.png");
diff --git a/crates/ui-egui/tests/it/ui_marker_names.rs b/crates/ui-egui/tests/it/ui_marker_names.rs
index 99adf41f3..190bd77bb 100644
--- a/crates/ui-egui/tests/it/ui_marker_names.rs
+++ b/crates/ui-egui/tests/it/ui_marker_names.rs
@@ -8,16 +8,13 @@ use effectcraft_ui_egui::theme::ThemeKind;
 use egui_kittest::Harness;
 use serde_json::json;
 
-/// One render at a time: two tests creating a GPU device together crash some Vulkan loaders.
-static RENDER: std::sync::Mutex<()> = std::sync::Mutex::new(());
-
 fn close(got: [u8; 4], want: egui::Color32) -> bool {
     got[..3].iter().zip(want.to_array()).all(|(a, b)| a.abs_diff(b) <= 3)
 }
 
 #[test]
 fn the_name_box_follows_the_theme() {
-    let _one_at_a_time = RENDER.lock().unwrap_or_else(std::sync::PoisonError::into_inner);
+    let _one_at_a_time = crate::gpu_test::lock();
     let mut s = Session::default();
     s.execute("comp.new", json!({"name": "Song", "width": 640, "height": 360, "duration": 4})).unwrap();
     s.execute("layer.newSolid", json!({"name": "Bed", "color": "#204060", "width": 640, "height": 360})).unwrap();
@@ -58,7 +55,7 @@ fn the_name_box_follows_the_theme() {
 /// stays visible: the cap is drawn, the bar shows left of it, and the box starts after it.
 #[test]
 fn a_short_duration_stays_visible_beside_the_name_box() {
-    let _one_at_a_time = RENDER.lock().unwrap_or_else(std::sync::PoisonError::into_inner);
+    let _one_at_a_time = crate::gpu_test::lock();
     let mut s = Session::default();
     s.execute("comp.new", json!({"name": "Song", "width": 640, "height": 360, "duration": 4})).unwrap();
     s.execute("layer.newSolid", json!({"name": "Bed", "color": "#204060", "width": 640, "height": 360})).unwrap();
@@ -95,3 +92,29 @@ fn a_short_duration_stays_visible_beside_the_name_box() {
     let fill = at(xe + 3.0 + 2.5, mid);
     assert!(close(fill, tokens.field_bg), "the box begins after the end cap: {fill:?}, field_bg {:?}", tokens.field_bg);
 }
+
+#[test]
+fn a_later_name_box_does_not_hide_an_earlier_duration_cap() {
+    let _one_at_a_time = crate::gpu_test::lock();
+    let mut s = Session::default();
+    s.execute("comp.new", json!({"width": 640, "height": 360, "duration": 4})).unwrap();
+    s.execute("markers.set", json!({"new": true, "time": 1.0, "duration": 0.5, "label": "Red"})).unwrap();
+    s.execute("markers.set", json!({"new": true, "time": 1.3, "comment": "This name overlaps the earlier endpoint", "label": "Blue"})).unwrap();
+    let mut h = Harness::builder().with_size(egui::vec2(1600.0, 1000.0)).build_eframe(move |_| EffectcraftApp::new(s));
+    h.run_steps(5);
+    let a = h.state().auto.find("timeline.marker.0").unwrap().rect;
+    let b = h.state().auto.find("timeline.marker.1").unwrap().rect;
+    let x = |r: [f32; 4]| r[0] + r[2] / 2.0;
+    let end = x(a) + (x(b) - x(a)) * 0.5 / 0.3;
+    let y = a[1] + 1.0 + (a[3] - 1.0).min(10.0) / 2.0;
+    let image = h.render().unwrap();
+    if let Some(dir) = std::env::var_os("MARKER_NAMES_SNAPSHOT") {
+        image.save(std::path::Path::new(&dir).join("marker-overlapping-cap.png")).unwrap();
+    }
+    let scale = image.width() as f32 / 1600.0;
+    let cap = (-1..=1)
+        .map(|offset| image.get_pixel(((end + offset as f32) * scale) as u32, (y * scale) as u32).0)
+        .max_by_key(|pixel| i32::from(pixel[0]) - i32::from(pixel[1]))
+        .unwrap();
+    assert!(i32::from(cap[0]) - i32::from(cap[1]) > 40, "the earlier red duration cap stays above the later name: {cap:?}");
+}
diff --git a/crates/ui-egui/tests/it/ui_media_browser_cache.rs b/crates/ui-egui/tests/it/ui_media_browser_cache.rs
index ddfc53e22..44ca9dd81 100644
--- a/crates/ui-egui/tests/it/ui_media_browser_cache.rs
+++ b/crates/ui-egui/tests/it/ui_media_browser_cache.rs
@@ -1,3 +1,4 @@
+use crate::gpu_test::RenderSerial;
 use std::sync::{
     Arc, Mutex,
     atomic::{AtomicBool, Ordering},
@@ -140,6 +141,6 @@ fn browser_cache_refreshes_filters_navigates_and_recovers_from_errors() {
     assert_eq!(names(&listing(&h, false).1), ["Sub", "Added.csv", "Clip.csv", "From action.csv"]);
     assert!(h.state().auto.find("mediaBrowser.entry.Clip.csv").is_some());
     if let Ok(path) = std::env::var("MEDIA_BROWSER_SNAPSHOT") {
-        h.render().unwrap().save(path).unwrap();
+        h.render_serialized().unwrap().save(path).unwrap();
     }
 }
diff --git a/crates/ui-egui/tests/it/ui_media_browser_copy_path.rs b/crates/ui-egui/tests/it/ui_media_browser_copy_path.rs
index dff60ddd0..8372b2be5 100644
--- a/crates/ui-egui/tests/it/ui_media_browser_copy_path.rs
+++ b/crates/ui-egui/tests/it/ui_media_browser_copy_path.rs
@@ -1,3 +1,4 @@
+use crate::gpu_test::RenderSerial;
 use std::sync::Arc;
 
 use effectcraft_engine::{
@@ -74,7 +75,7 @@ fn file_folder_and_virtual_paths_copy_from_the_context_menu_without_document_cha
         if name == "作品 clip.csv"
             && let Ok(file) = std::env::var("MEDIA_BROWSER_COPY_SNAPSHOT")
         {
-            h.render().unwrap().save(file).unwrap();
+            h.render_serialized().unwrap().save(file).unwrap();
         }
         assert_eq!(click(&mut h, &id, PointerButton::Primary), [path]);
         h.run_steps(3);
diff --git a/crates/ui-egui/tests/it/ui_menus.rs b/crates/ui-egui/tests/it/ui_menus.rs
index 8501f6b52..512f1f376 100644
--- a/crates/ui-egui/tests/it/ui_menus.rs
+++ b/crates/ui-egui/tests/it/ui_menus.rs
@@ -1,6 +1,7 @@
 //! The menu bar from the keyboard, and the app's shortcuts waiting while a menu is open (#279)
 //! (egui_kittest, UI logic only).
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_ui_egui::EffectcraftApp;
 use egui::{Event, Key, Modifiers, Pos2, Rect, pos2, vec2};
@@ -226,7 +227,7 @@ fn relink_is_reachable_through_the_dependencies_menu() {
     h.run_steps(8);
     let relink = h.query_by_label_contains("Relink Missing Footage").unwrap().rect();
     if let Some(path) = std::env::var_os("EFFECTCRAFT_RELINK_MENU_SNAPSHOT") {
-        h.render().unwrap().save(path).unwrap();
+        h.render_serialized().unwrap().save(path).unwrap();
     }
     click_at(&mut h, relink.center());
     assert!(picked.get());
diff --git a/crates/ui-egui/tests/it/ui_panels.rs b/crates/ui-egui/tests/it/ui_panels.rs
index 6d06c6bf7..2c2d650e9 100644
--- a/crates/ui-egui/tests/it/ui_panels.rs
+++ b/crates/ui-egui/tests/it/ui_panels.rs
@@ -2,6 +2,7 @@
 //! registers its automation ids; the Footage panel's buttons edit into the comp; the Progress
 //! panel lists and cancels a job; Lumetri Scopes switch scope through their dropdown.
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_ui_egui::dock::WorkspaceExt as _;
 use std::sync::Arc;
 
@@ -448,7 +449,7 @@ fn panels_snapshot() {
         }
         open(&mut h, panel);
         h.run_steps(3);
-        let img = h.render().expect("render");
+        let img = h.render_serialized().expect("render");
         img.save(format!("{dir}/{panel}{scope}.png")).unwrap();
     }
 }
diff --git a/crates/ui-egui/tests/it/ui_presets_folder.rs b/crates/ui-egui/tests/it/ui_presets_folder.rs
index e11efe944..1bcd9189c 100644
--- a/crates/ui-egui/tests/it/ui_presets_folder.rs
+++ b/crates/ui-egui/tests/it/ui_presets_folder.rs
@@ -1,5 +1,6 @@
 //! Effects & Presets: copy the configured folder path through the contents menu.
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_ui_egui::panels::effects_presets::PresetFile;
 use effectcraft_ui_egui::{ControlRequest, EffectcraftApp, control, dock::PanelKind};
@@ -52,7 +53,7 @@ fn presets_menu_copies_the_configured_folder_without_editing_the_project() {
         click(&mut h, "effects.menu");
         h.run_steps(3);
         if let Ok(path) = std::env::var("PRESETS_FOLDER_SNAPSHOT") {
-            h.render().unwrap().save(path).unwrap();
+            h.render_serialized().unwrap().save(path).unwrap();
         }
         assert_eq!(click(&mut h, "effects.copyPresetsFolderPath"), [expected.as_str()]);
         h.run_steps(2);
@@ -156,7 +157,7 @@ fn shared_preset_rows_search_apply_and_undo_the_selected_definition() {
         assert_eq!(h.state().session.active_comp().unwrap().layers[0].props.prop("transform/opacity").unwrap().value.as_f64(), expected);
         assert_eq!(h.state().session.history.undo.len(), history + 1);
         if let Ok(dir) = std::env::var("PRESET_CACHE_SNAPSHOTS") {
-            h.render().unwrap().save(format!("{dir}/{name}.png")).unwrap();
+            h.render_serialized().unwrap().save(format!("{dir}/{name}.png")).unwrap();
         }
         h.state_mut().session.execute("edit.undo", json!({})).unwrap();
         h.run_steps(2);
diff --git a/crates/ui-egui/tests/it/ui_script_console.rs b/crates/ui-egui/tests/it/ui_script_console.rs
index e705a20b7..9430bc7a2 100644
--- a/crates/ui-egui/tests/it/ui_script_console.rs
+++ b/crates/ui-egui/tests/it/ui_script_console.rs
@@ -1,6 +1,7 @@
 //! Window ▸ Script Console: the panel shows, runs JavaScript through `script.run` (persistent
 //! context) and logs output, results and errors (egui_kittest, UI logic only).
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_ui_egui::EffectcraftApp;
 use effectcraft_ui_egui::dock::PanelKind;
 use egui_kittest::Harness;
@@ -59,7 +60,7 @@ fn script_console_snapshot() {
     }
     h.state_mut().ui.script_console.input = "app.project.numItems".into();
     h.run_steps(3);
-    let img = h.render().expect("render");
+    let img = h.render_serialized().expect("render");
     let out = std::env::var("SC_SNAPSHOT").unwrap_or_else(|_| concat!(env!("CARGO_MANIFEST_DIR"), "/../../target/test-out/script_console.png").into());
     if let Some(d) = std::path::Path::new(&out).parent() {
         std::fs::create_dir_all(d).unwrap();
diff --git a/crates/ui-egui/tests/it/ui_scriptui.rs b/crates/ui-egui/tests/it/ui_scriptui.rs
index 0a924bb65..a905ebc5a 100644
--- a/crates/ui-egui/tests/it/ui_scriptui.rs
+++ b/crates/ui-egui/tests/it/ui_scriptui.rs
@@ -2,6 +2,7 @@
 //! windows (clicks reach the script's handlers), the branching History panel, and the Window /
 //! File ▸ Scripts menus listing scripts (egui_kittest, UI logic only).
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_ui_egui::EffectcraftApp;
 use effectcraft_ui_egui::dock::PanelKind;
 use effectcraft_ui_egui::dock::WorkspaceExt as _;
@@ -210,6 +211,7 @@ fn history_panel_jumps_between_branches() {
 /// onDraw fills of concave paths and real images (drawImage, image controls), rendered.
 #[test]
 fn on_draw_concave_fills_and_images_render() {
+    let _device = crate::gpu_test::lock();
     let dir = std::env::temp_dir().join(format!("effectcraft-scriptui-img-{}", std::process::id()));
     std::fs::create_dir_all(&dir).unwrap();
     let png = dir.join("green.png");
@@ -244,7 +246,7 @@ fn on_draw_concave_fills_and_images_render() {
     let g = &win.root.children[0];
     assert!(matches!(&g.draw[1], effectcraft_engine::scriptui::DrawOp::Image { image: Some(i), .. } if i.src.as_deref() == Some(png.as_str())));
     assert_eq!(win.root.children[1].image.as_ref().and_then(|i| i.src.clone()).as_deref(), Some(png.as_str()));
-    let img = h.render().expect("render");
+    let img = h.render_serialized().expect("render");
     if let Ok(d) = std::env::var("EC_SNAPSHOT_DIR") {
         img.save(format!("{d}/scriptui_paint.png")).unwrap();
     }
diff --git a/crates/ui-egui/tests/it/ui_tabs.rs b/crates/ui-egui/tests/it/ui_tabs.rs
index 5fc3d8598..cc9e56041 100644
--- a/crates/ui-egui/tests/it/ui_tabs.rs
+++ b/crates/ui-egui/tests/it/ui_tabs.rs
@@ -2,6 +2,7 @@
 //! as its own Timeline tab (not a rename, and not in place of the comp shown), the tabs switch and
 //! close comps, and a dragged tab lands where its insertion mark shows.
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::project::ItemId;
 use effectcraft_ui_egui::EffectcraftApp;
@@ -135,7 +136,7 @@ fn tab_drag_snapshot() {
     }
     let dir = concat!(env!("CARGO_MANIFEST_DIR"), "/../../target/test-out");
     std::fs::create_dir_all(dir).unwrap();
-    h.render().expect("render").save(format!("{dir}/tab-drag.png")).unwrap();
+    h.render_serialized().expect("render").save(format!("{dir}/tab-drag.png")).unwrap();
 }
 
 /// A precomp layer's bar shows its comp's markers; a double-click opens that comp at the marker.
diff --git a/crates/ui-egui/tests/it/ui_theme_favorites.rs b/crates/ui-egui/tests/it/ui_theme_favorites.rs
index 1b700f51f..424b28c49 100644
--- a/crates/ui-egui/tests/it/ui_theme_favorites.rs
+++ b/crates/ui-egui/tests/it/ui_theme_favorites.rs
@@ -1,3 +1,4 @@
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::{Session, config::MemoryConfig, prefs::Prefs};
 use effectcraft_ui_egui::{EffectcraftApp, menus};
 use egui::{Event, Modifiers, PointerButton, Pos2, pos2, vec2};
@@ -49,7 +50,7 @@ fn star_controls_save_and_favorite_menu_selects_the_family() {
     assert_eq!(h.state().session.prefs.appearance.favorite_themes, vec!["light"]);
     if let Some(path) = std::env::var_os("FAVORITES_SCREENSHOT_DIR") {
         std::fs::create_dir_all(&path).unwrap();
-        h.render().unwrap().save(std::path::Path::new(&path).join("effectcraft-favorites.png")).unwrap();
+        h.render_serialized().unwrap().save(std::path::Path::new(&path).join("effectcraft-favorites.png")).unwrap();
     }
     assert_eq!(h.state().session.prefs.appearance.appearance_mode, "dark");
     let p = at(&h, "settings.ok");
diff --git a/crates/ui-egui/tests/it/ui_viewer.rs b/crates/ui-egui/tests/it/ui_viewer.rs
index 41cf5fe43..48bc36a44 100644
--- a/crates/ui-egui/tests/it/ui_viewer.rs
+++ b/crates/ui-egui/tests/it/ui_viewer.rs
@@ -2,6 +2,7 @@
 //! interest drawing, rulers and guides, snapping, the shape Pen and motion-path key drags
 //! (egui_kittest, UI logic only).
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::commands::shape_tool::PaintKind;
 use effectcraft_engine::project::LayerId;
@@ -448,7 +449,7 @@ fn mid_drag(h: &mut Harness<'_, EffectcraftApp>, from: Pos2, to: Pos2, mods: egu
         h.input_mut().events.push(Event::PointerMoved(from + (to - from) * (i as f32 / 8.0)));
         h.step();
     }
-    h.render().expect("the mid-drag frame")
+    h.render_serialized().expect("the mid-drag frame")
 }
 
 /// Release the button where the drag left it.
@@ -490,7 +491,7 @@ fn shape_drag_ghost_shows_the_tools_own_shape_while_dragging() {
         h.state_mut().ui.tool = tool;
         settle_viewer(&mut h);
         let (a, b) = (screen(&h, from), screen(&h, to));
-        let before = h.render().expect("the frame before the drag");
+        let before = h.render_serialized().expect("the frame before the drag");
         let mid = mid_drag(&mut h, a, b, egui::Modifiers::default());
         let fill = fill_rgb(&h);
 
@@ -526,7 +527,7 @@ fn shape_drag_ghost_normalises_the_same_way_as_the_release() {
         h.state_mut().ui.tool = Tool::Ellipse;
         settle_viewer(&mut h);
         let (a, b) = (screen(&h, from.map(|v| v as f32)), screen(&h, to.map(|v| v as f32)));
-        let before = h.render().expect("the frame before the drag");
+        let before = h.render_serialized().expect("the frame before the drag");
         // Measured with the button down, so this is the ghost and not the committed shape.
         let mid = mid_drag(&mut h, a, b, mods);
         let on = [centre[0] as f32 + size[0] as f32 / 4.0, centre[1] as f32 + size[1] as f32 / 4.0];
@@ -595,7 +596,7 @@ fn a_layer_drag_moves_the_picture_while_the_button_is_down() {
     h.input_mut().events.push(Event::PointerButton { pos: from, button: egui::PointerButton::Primary, pressed: true, modifiers: Default::default() });
     h.step();
     // Where the layer is not (yet): the plate behind it.
-    let plate = px_at(&h.render().unwrap(), &h, [440.0, 200.0]);
+    let plate = px_at(&h.render_serialized().unwrap(), &h, [440.0, 200.0]);
 
     // Drag in small steps, still holding the button, and give the renders a chance to land.
     let mut moved = false;
@@ -606,7 +607,7 @@ fn a_layer_drag_moves_the_picture_while_the_button_is_down() {
         std::thread::sleep(std::time::Duration::from_millis(15));
         // 30 comp px behind the pointer: inside the layer, well away from its outline, its anchor
         // icon and where it started.
-        let at = px_at(&h.render().expect("mid-drag frame"), &h, [320.0 + 200.0 * (i as f32 / 40.0) - 30.0, 200.0]);
+        let at = px_at(&h.render_serialized().expect("mid-drag frame"), &h, [320.0 + 200.0 * (i as f32 / 40.0) - 30.0, 200.0]);
         if i >= 30 && delta(at, plate) > 30 {
             moved = true;
             break;
diff --git a/crates/ui-egui/tests/it/ui_viewers.rs b/crates/ui-egui/tests/it/ui_viewers.rs
index 833ab0a60..bfbcad51e 100644
--- a/crates/ui-egui/tests/it/ui_viewers.rs
+++ b/crates/ui-egui/tests/it/ui_viewers.rs
@@ -2,6 +2,7 @@
 //! comp goes to an unlocked viewer (a new one when every viewer is locked); a click on another
 //! viewer makes it the active one; closing a viewer forgets it.
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_engine::project::ItemId;
 use effectcraft_ui_egui::EffectcraftApp;
@@ -171,5 +172,5 @@ fn viewers_snapshot() {
     h.run_steps(4);
     let dir = concat!(env!("CARGO_MANIFEST_DIR"), "/../../target/test-out");
     std::fs::create_dir_all(dir).unwrap();
-    h.render().unwrap().save(format!("{dir}/viewers.png")).unwrap();
+    h.render_serialized().unwrap().save(format!("{dir}/viewers.png")).unwrap();
 }
diff --git a/crates/ui-egui/tests/it/ui_visual_review.rs b/crates/ui-egui/tests/it/ui_visual_review.rs
index 70cc5ed84..6d079f1f5 100644
--- a/crates/ui-egui/tests/it/ui_visual_review.rs
+++ b/crates/ui-egui/tests/it/ui_visual_review.rs
@@ -1,5 +1,6 @@
 //! Opt-in visual review of every built-in panel, workspaces and common dialogs.
 //! Original fixture; captures are review outputs, not shipped assets.
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_ui_egui::{Dialog, EffectcraftApp, dock::PanelKind};
 use egui_kittest::Harness;
@@ -19,18 +20,18 @@ fn all_ui_review_captures() {
         std::sync::Arc::make_mut(&mut s.project).settings.gpu_acceleration = false;
         let mut h = Harness::builder().with_size(size).build_eframe(|_| EffectcraftApp::new(s));
         h.run_steps(4);
-        h.render().unwrap().save(out.join(format!("{label}-workspace.png"))).unwrap();
+        h.render_serialized().unwrap().save(out.join(format!("{label}-workspace.png"))).unwrap();
         let ctx = h.ctx.clone();
         h.state_mut().set_theme(&ctx, effectcraft_ui_egui::theme::ThemeKind::Light);
         h.run_steps(4);
-        h.render().unwrap().save(out.join(format!("{label}-workspace-light.png"))).unwrap();
+        h.render_serialized().unwrap().save(out.join(format!("{label}-workspace-light.png"))).unwrap();
         h.state_mut().set_theme(&ctx, effectcraft_ui_egui::theme::ThemeKind::Dark);
         for p in PanelKind::ALL {
             h.state_mut().show_panel(p);
             h.state_mut().ui.maximized = Some(p);
             h.run_steps(4);
             assert!(h.state().auto.find(&format!("panel.{}", p.id())).is_some(), "{} opens", p.title());
-            h.render().unwrap().save(out.join(format!("{label}-{}.png", p.id()))).unwrap();
+            h.render_serialized().unwrap().save(out.join(format!("{label}-{}.png", p.id()))).unwrap();
         }
         h.state_mut().ui.maximized = None;
         for (name, dialog) in [
@@ -42,7 +43,7 @@ fn all_ui_review_captures() {
         ] {
             h.state_mut().dialog = Some(dialog);
             h.run_steps(4);
-            h.render().unwrap().save(out.join(format!("{label}-dialog-{name}.png"))).unwrap();
+            h.render_serialized().unwrap().save(out.join(format!("{label}-dialog-{name}.png"))).unwrap();
             h.state_mut().dialog = None;
             h.run_steps(2);
         }
diff --git a/crates/ui-egui/tests/it/ui_web_gpu_storage.rs b/crates/ui-egui/tests/it/ui_web_gpu_storage.rs
index a742226de..024bd1cd0 100644
--- a/crates/ui-egui/tests/it/ui_web_gpu_storage.rs
+++ b/crates/ui-egui/tests/it/ui_web_gpu_storage.rs
@@ -122,6 +122,7 @@ fn cpu_pixels(f: &FrameImage) -> Vec<egui::Color32> {
 
 #[test]
 fn gpu_worker_renders_effect_frames_and_the_disk_cache_survives_a_reload() {
+    let _device = crate::gpu_test::lock();
     let (Some(page_gpu), Some(worker_gpu)) = (Gpu::headless(), Gpu::headless_deferred()) else {
         eprintln!("no GPU adapter: skipped");
         return;
diff --git a/crates/ui-egui/tests/it/ui_web_job_gpu.rs b/crates/ui-egui/tests/it/ui_web_job_gpu.rs
index 9060e1067..8b8914abc 100644
--- a/crates/ui-egui/tests/it/ui_web_job_gpu.rs
+++ b/crates/ui-egui/tests/it/ui_web_job_gpu.rs
@@ -10,10 +10,6 @@ use effectcraft_engine::offload::{Inbox, Offload, Post, WorkerReply, WorkerReque
 use effectcraft_gpu::Gpu;
 use serde_json::json;
 
-/// One device at a time in this test binary: wgpu's OpenGL backend (Mesa llvmpipe on FreeBSD,
-/// Linux without Vulkan) panics or crashes when tests create and drive devices concurrently.
-static GPU_LOCK: Mutex<()> = Mutex::new(());
-
 /// Holds offloaded jobs until the test runs them.
 #[derive(Default)]
 struct Manual(Mutex<Vec<(WorkerRequest, Arc<Inbox>)>>);
@@ -63,7 +59,7 @@ fn page() -> (Session, Arc<Manual>) {
 
 #[test]
 fn render_queue_jobs_render_on_the_worker_gpu() {
-    let _gpu = GPU_LOCK.lock().unwrap_or_else(std::sync::PoisonError::into_inner);
+    let _gpu = crate::gpu_test::lock();
     let Some(g) = Gpu::headless_deferred() else {
         eprintln!("no GPU adapter: skipped");
         return;
@@ -102,7 +98,7 @@ fn render_queue_jobs_render_on_the_worker_gpu() {
 
 #[test]
 fn analyses_render_their_input_on_the_worker_gpu() {
-    let _gpu = GPU_LOCK.lock().unwrap_or_else(std::sync::PoisonError::into_inner);
+    let _gpu = crate::gpu_test::lock();
     let Some(g) = Gpu::headless_deferred() else {
         eprintln!("no GPU adapter: skipped");
         return;
diff --git a/crates/ui-egui/tests/it/ui_workflow_selection.rs b/crates/ui-egui/tests/it/ui_workflow_selection.rs
index 121c2b888..e7bcedb60 100644
--- a/crates/ui-egui/tests/it/ui_workflow_selection.rs
+++ b/crates/ui-egui/tests/it/ui_workflow_selection.rs
@@ -1,4 +1,5 @@
 //! User-reported selection, Project deletion, and render-queue drop regressions.
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::{Session, project::LayerId};
 use effectcraft_ui_egui::{Dialog, EffectcraftApp, dock::PanelKind};
 use egui::{Event, Modifiers, PointerButton, Pos2, Rect, pos2, vec2};
@@ -273,7 +274,7 @@ fn viewer_right_click_targets_hit_and_duplicate_preserves_group() {
         }
         assert!(h.state().frames.is_cached(&key));
         h.run_steps(3);
-        h.render().expect("offscreen context menu render").save(out).unwrap();
+        h.render_serialized().expect("offscreen context menu render").save(out).unwrap();
     }
     h.get_by_label("Duplicate").click();
     h.run_steps(3);
@@ -433,7 +434,7 @@ fn workflow_snapshot() {
     }
     assert!(h.state().frames.is_cached(&key), "current composition rendered before capture");
     h.run_steps(3);
-    h.render().expect("offscreen UI render").save(out).unwrap();
+    h.render_serialized().expect("offscreen UI render").save(out).unwrap();
 }
 
 /// Filled rects painted this frame (flattening nested shape lists).
diff --git a/crates/ui-egui/tests/it/viewer_geometry.rs b/crates/ui-egui/tests/it/viewer_geometry.rs
index e3e4128e8..d57a8aa9e 100644
--- a/crates/ui-egui/tests/it/viewer_geometry.rs
+++ b/crates/ui-egui/tests/it/viewer_geometry.rs
@@ -1,5 +1,6 @@
 //! Inspect the actual viewer's painted colors and pointer-driven control geometry.
 
+use crate::gpu_test::RenderSerial;
 use effectcraft_engine::Session;
 use effectcraft_ui_egui::{
     EffectcraftApp,
@@ -269,10 +270,10 @@ fn viewer_theme_and_width_visual_matrix() {
 }
 
 fn save_stable_snapshot(h: &mut Harness<'_, EffectcraftApp>, path: &str, width: f32) {
-    let image = h.render().unwrap();
+    let image = h.render_serialized().unwrap();
     image.save(path).unwrap();
     h.run_steps(3);
-    let repeated = h.render().unwrap();
+    let repeated = h.render_serialized().unwrap();
     assert!(image == repeated, "settled synthetic viewer pixels must repeat exactly: {path}");
     if width == 900.0 {
         let times: Vec<_> = h