diff --git a/src/experimental/studio/app.cc b/src/experimental/studio/app.cc
index 55f7a1d5..721ce6a7 100644
--- a/src/experimental/studio/app.cc
+++ b/src/experimental/studio/app.cc
@@ -1233,6 +1233,236 @@ static std::string FormatTimelineTime(double time_in_s) {
   return buf;
 }
 
+void App::TimelineScrubberGui() {
+  // Timeline scrubber: spine + sliding knob widget.
+  const double max_time = tmp_.sim_head_time_;
+  const int hist_size = sim_history_.Size();
+  const int hist_min = 1 - hist_size;  // most negative index (oldest)
+  const int hist_max = 0;              // index 0 = most recent
+  int current_index = sim_history_.GetIndex();
+  const bool locked = (hist_size <= 1);
+
+  // Compute current timestamp for LH label.
+  double curr_time =
+      (has_data() && current_index == sim_history_.GetIndex())
+          ? data()->time
+          : (max_time +
+             current_index *
+                 (has_model() ? model()->opt.timestep : 0.002));
+  if (curr_time < 0.0) curr_time = 0.0;
+
+  const int curr_step = (has_model() && model()->opt.timestep > 0)
+                            ? static_cast<int>(std::round(
+                                  curr_time / model()->opt.timestep))
+                            : 0;
+  const int max_step =
+      (has_model() && model()->opt.timestep > 0)
+          ? static_cast<int>(std::round(max_time / model()->opt.timestep))
+          : 0;
+
+  // Both LH and RH labels aim to be at 3 digits, switching units
+  // independently.
+  std::string lh_top_str = FormatTimelineTime(curr_time);
+  std::string rh_top_str = FormatTimelineTime(max_time);
+  std::string lh_bot_str = "(" + std::to_string(curr_step) + ")";
+  std::string rh_bot_str = "(" + std::to_string(max_step) + ")";
+  const char* lh_top_label = lh_top_str.c_str();
+  const char* rh_top_label = rh_top_str.c_str();
+  const char* lh_bot_label = lh_bot_str.c_str();
+  const char* rh_bot_label = rh_bot_str.c_str();
+
+  // Use slightly smaller text for timeline labels (e.g. 90% scale).
+  ImGui::SetWindowFontScale(0.9f);
+
+  const ImVec2 cursor = ImGui::GetCursorScreenPos();
+  const float spacing = ImGui::GetStyle().ItemSpacing.x;
+  const float base_label_w =
+      std::max(ImGui::CalcTextSize("88.8 ms").x,
+               ImGui::CalcTextSize("88.8 \xC2\xB5s").x);
+  const float curr_lh_w =
+      std::max({base_label_w, ImGui::CalcTextSize(lh_top_label).x,
+                ImGui::CalcTextSize(lh_bot_label).x});
+  if (curr_lh_w > tmp_.timeline_lh_width) {
+    tmp_.timeline_lh_width = curr_lh_w;
+  }
+  const float curr_rh_w =
+      std::max({base_label_w, ImGui::CalcTextSize(rh_top_label).x,
+                ImGui::CalcTextSize(rh_bot_label).x});
+  if (curr_rh_w > tmp_.timeline_rh_width) {
+    tmp_.timeline_rh_width = curr_rh_w;
+  }
+  const float lh_box_w = tmp_.timeline_lh_width;
+  const float rh_box_w = tmp_.timeline_rh_width;
+  const float track_w =
+      std::max(10.0f, ImGui::GetContentRegionAvail().x - lh_box_w -
+                          rh_box_w - spacing * 2.0f);
+
+  const float spine_h = 3.0f;
+  const float knob_w = 12.0f;
+  const float knob_h = 27.0f;  // 1.5x taller than 18.0f
+  const float text_line_h = ImGui::GetTextLineHeight();
+  const float custom_line_spacing =
+      1.0f;  // Decreased spacing between the two lines
+  const float text_2lines_h = text_line_h * 2.0f + custom_line_spacing;
+  const float total_h = std::max(knob_h, text_2lines_h);
+
+  // Vertical center of the track row.
+  const float row_center_y = cursor.y + total_h * 0.5f;
+  const float track_x0 = cursor.x + lh_box_w + spacing;
+  const float spine_y0 = row_center_y - spine_h * 0.5f;
+  const float spine_y1 = row_center_y + spine_h * 0.5f;
+  const float spine_x0 = track_x0;
+  const float spine_x1 = track_x0 + track_w;
+
+  // Compute knob position [0,1] along the spine.
+  float t = 1.0f;  // Default: pinned to right end.
+  if (!locked) {
+    t = static_cast<float>(current_index - hist_min) /
+        static_cast<float>(hist_max - hist_min);
+  }
+  const float knob_cx = spine_x0 + t * (track_w - knob_w) + knob_w * 0.5f;
+
+  // Invisible interaction button over the full track area.
+  ImGui::SetCursorScreenPos(
+      ImVec2(track_x0, row_center_y - total_h * 0.5f));
+  ImGui::InvisibleButton("##Scrubber", ImVec2(track_w, total_h));
+  const bool hovered = ImGui::IsItemHovered();
+  const bool active = ImGui::IsItemActive();
+
+  // Handle dragging.
+  if (!locked && (active || (hovered && ImGui::IsMouseDown(
+                                            ImGuiMouseButton_Left)))) {
+    const float mouse_x = ImGui::GetIO().MousePos.x;
+    if (!tmp_.scrubber_active) {
+      tmp_.scrubber_active = true;
+      if (std::abs(mouse_x - knob_cx) <= knob_w) {
+        tmp_.scrubber_grab_offset = mouse_x - knob_cx;
+      } else {
+        tmp_.scrubber_grab_offset = 0.0f;
+      }
+    }
+
+    const float effective_mouse_x = mouse_x - tmp_.scrubber_grab_offset;
+    const float raw_t = (effective_mouse_x - spine_x0 - knob_w * 0.5f) /
+                        std::max(1.0f, track_w - knob_w);
+    const float clamped_t = std::clamp(raw_t, 0.0f, 1.0f);
+
+    int new_index = current_index;
+    const float snap_eps = std::max(
+        0.02f, std::min(0.05f, 8.0f / std::max(1.0f, track_w - knob_w)));
+    if (clamped_t <= snap_eps ||
+        effective_mouse_x <= spine_x0 + knob_w * 0.5f + 6.0f) {
+      new_index = hist_min;
+    } else if (clamped_t >= 1.0f - snap_eps ||
+               effective_mouse_x >= spine_x1 - knob_w * 0.5f - 6.0f) {
+      new_index = hist_max;
+    } else {
+      const float inner_t =
+          (clamped_t - snap_eps) / (1.0f - 2.0f * snap_eps);
+      new_index =
+          hist_min +
+          static_cast<int>(std::round(inner_t * (hist_max - hist_min)));
+    }
+
+    if (new_index != current_index) {
+      LoadHistory(new_index);
+      current_index = new_index;
+      t = static_cast<float>(current_index - hist_min) /
+          static_cast<float>(hist_max - hist_min);
+      if (has_data() && current_index == sim_history_.GetIndex()) {
+        curr_time = data()->time;
+        if (curr_time < 0.0) curr_time = 0.0;
+        lh_top_str = FormatTimelineTime(curr_time);
+        lh_top_label = lh_top_str.c_str();
+        const int updated_curr_step =
+            (has_model() && model()->opt.timestep > 0)
+                ? static_cast<int>(
+                      std::round(curr_time / model()->opt.timestep))
+                : 0;
+        lh_bot_str = "(" + std::to_string(updated_curr_step) + ")";
+        lh_bot_label = lh_bot_str.c_str();
+        const float updated_lh_w =
+            std::max({base_label_w, ImGui::CalcTextSize(lh_top_label).x,
+                      ImGui::CalcTextSize(lh_bot_label).x});
+        if (updated_lh_w > tmp_.timeline_lh_width) {
+          tmp_.timeline_lh_width = updated_lh_w;
+        }
+      }
+    }
+  } else {
+    tmp_.scrubber_active = false;
+  }
+
+  // Draw LH labels (two lines, both right-aligned).
+  const float text_y0 = row_center_y - text_2lines_h * 0.5f;
+  const float text_y1 = text_y0 + text_line_h + custom_line_spacing;
+
+  const float lh_top_x =
+      cursor.x + lh_box_w - ImGui::CalcTextSize(lh_top_label).x;
+  ImGui::SetCursorScreenPos(ImVec2(lh_top_x, text_y0));
+  ImGui::TextUnformatted(lh_top_label);
+
+  const float lh_bot_x =
+      cursor.x + lh_box_w - ImGui::CalcTextSize(lh_bot_label).x;
+  ImGui::SetCursorScreenPos(ImVec2(lh_bot_x, text_y1));
+  ImGui::TextUnformatted(lh_bot_label);
+
+  // Draw RH labels (two lines, both left-aligned).
+  const float rh_x0 = track_x0 + track_w + spacing;
+  ImGui::SetCursorScreenPos(ImVec2(rh_x0, text_y0));
+  ImGui::TextUnformatted(rh_top_label);
+
+  ImGui::SetCursorScreenPos(ImVec2(rh_x0, text_y1));
+  ImGui::TextUnformatted(rh_bot_label);
+
+  // Restore window font scale.
+  ImGui::SetWindowFontScale(1.0f);
+
+  // Draw spine and knob on the draw list.
+  ImDrawList* dl = ImGui::GetWindowDrawList();
+  const ImGuiStyle& style = ImGui::GetStyle();
+
+  // Spine.
+  const ImVec4 scrollbar_bg =
+      ImGui::GetStyle().Colors[ImGuiCol_ScrollbarBg];
+  ImGuiCol bg_col_idx;
+  if (active) {
+    bg_col_idx = ImGuiCol_FrameBgActive;
+  } else if (hovered) {
+    bg_col_idx = ImGuiCol_FrameBgHovered;
+  } else {
+    bg_col_idx = (scrollbar_bg.w > 0.01f) ? ImGuiCol_ScrollbarBg
+                                          : ImGuiCol_FrameBg;
+  }
+  const ImU32 spine_col = ImGui::GetColorU32(bg_col_idx);
+  dl->AddRectFilled(ImVec2(spine_x0, spine_y0),
+                    ImVec2(spine_x1, spine_y1), spine_col,
+                    spine_h * 0.5f);
+
+  // Knob rectangle.
+  const float knob_x0 = knob_cx - knob_w * 0.5f;
+  const float knob_x1 = knob_cx + knob_w * 0.5f;
+  const float knob_y0 = row_center_y - knob_h * 0.5f;
+  const float knob_y1 = row_center_y + knob_h * 0.5f;
+
+  ImU32 knob_col;
+  if (active) {
+    knob_col = ImGui::GetColorU32(ImGuiCol_SliderGrabActive);
+  } else if (hovered) {
+    knob_col = ImGui::GetColorU32(ImGuiCol_SliderGrab);
+  } else {
+    knob_col = ImGui::GetColorU32(ImGuiCol_SliderGrab);
+  }
+  dl->AddRectFilled(ImVec2(knob_x0, knob_y0), ImVec2(knob_x1, knob_y1),
+                    knob_col, style.GrabRounding);
+  // Knob border.
+  dl->AddRect(ImVec2(knob_x0, knob_y0), ImVec2(knob_x1, knob_y1),
+              ImGui::GetColorU32(ImGuiCol_Border), style.GrabRounding);
+
+  // Advance layout cursor past this row.
+  ImGui::SetCursorScreenPos(ImVec2(cursor.x, cursor.y + total_h));
+}
+
 void App::ModelOptionsGui() {
   const float min_width = platform::GetExpectedLabelWidth();
   const ImGuiChildFlags child_flags =
@@ -1378,235 +1608,8 @@ void App::ModelOptionsGui() {
       }
       ImGui::SetItemTooltip("%s", "Load next frame from history / Single step");
 
-      // Timeline scrubber: spine + sliding knob widget.
-      {
-        const double max_time = tmp_.sim_head_time_;
-        const int hist_size = sim_history_.Size();
-        const int hist_min = 1 - hist_size;  // most negative index (oldest)
-        const int hist_max = 0;              // index 0 = most recent
-        int current_index = sim_history_.GetIndex();
-        const bool locked = (hist_size <= 1);
-
-        // Compute current timestamp for LH label.
-        double curr_time =
-            (has_data() && current_index == sim_history_.GetIndex())
-                ? data()->time
-                : (max_time +
-                   current_index *
-                       (has_model() ? model()->opt.timestep : 0.002));
-        if (curr_time < 0.0) curr_time = 0.0;
-
-        const int curr_step = (has_model() && model()->opt.timestep > 0)
-                                  ? static_cast<int>(std::round(
-                                        curr_time / model()->opt.timestep))
-                                  : 0;
-        const int max_step =
-            (has_model() && model()->opt.timestep > 0)
-                ? static_cast<int>(std::round(max_time / model()->opt.timestep))
-                : 0;
-
-        // Both LH and RH labels aim to be at 3 digits, switching units
-        // independently.
-        std::string lh_top_str = FormatTimelineTime(curr_time);
-        std::string rh_top_str = FormatTimelineTime(max_time);
-        std::string lh_bot_str = "(" + std::to_string(curr_step) + ")";
-        std::string rh_bot_str = "(" + std::to_string(max_step) + ")";
-        const char* lh_top_label = lh_top_str.c_str();
-        const char* rh_top_label = rh_top_str.c_str();
-        const char* lh_bot_label = lh_bot_str.c_str();
-        const char* rh_bot_label = rh_bot_str.c_str();
-
-        // Use slightly smaller text for timeline labels (e.g. 90% scale).
-        ImGui::SetWindowFontScale(0.9f);
-
-        const ImVec2 cursor = ImGui::GetCursorScreenPos();
-        const float spacing = ImGui::GetStyle().ItemSpacing.x;
-        const float base_label_w =
-            std::max(ImGui::CalcTextSize("88.8 ms").x,
-                     ImGui::CalcTextSize("88.8 \xC2\xB5s").x);
-        const float curr_lh_w =
-            std::max({base_label_w, ImGui::CalcTextSize(lh_top_label).x,
-                      ImGui::CalcTextSize(lh_bot_label).x});
-        if (curr_lh_w > tmp_.timeline_lh_width) {
-          tmp_.timeline_lh_width = curr_lh_w;
-        }
-        const float curr_rh_w =
-            std::max({base_label_w, ImGui::CalcTextSize(rh_top_label).x,
-                      ImGui::CalcTextSize(rh_bot_label).x});
-        if (curr_rh_w > tmp_.timeline_rh_width) {
-          tmp_.timeline_rh_width = curr_rh_w;
-        }
-        const float lh_box_w = tmp_.timeline_lh_width;
-        const float rh_box_w = tmp_.timeline_rh_width;
-        const float track_w =
-            std::max(10.0f, ImGui::GetContentRegionAvail().x - lh_box_w -
-                                rh_box_w - spacing * 2.0f);
-
-        const float spine_h = 3.0f;
-        const float knob_w = 12.0f;
-        const float knob_h = 27.0f;  // 1.5x taller than 18.0f
-        const float text_line_h = ImGui::GetTextLineHeight();
-        const float custom_line_spacing =
-            1.0f;  // Decreased spacing between the two lines
-        const float text_2lines_h = text_line_h * 2.0f + custom_line_spacing;
-        const float total_h = std::max(knob_h, text_2lines_h);
-
-        // Vertical center of the track row.
-        const float row_center_y = cursor.y + total_h * 0.5f;
-        const float track_x0 = cursor.x + lh_box_w + spacing;
-        const float spine_y0 = row_center_y - spine_h * 0.5f;
-        const float spine_y1 = row_center_y + spine_h * 0.5f;
-        const float spine_x0 = track_x0;
-        const float spine_x1 = track_x0 + track_w;
-
-        // Compute knob position [0,1] along the spine.
-        float t = 1.0f;  // Default: pinned to right end.
-        if (!locked) {
-          t = static_cast<float>(current_index - hist_min) /
-              static_cast<float>(hist_max - hist_min);
-        }
-        const float knob_cx = spine_x0 + t * (track_w - knob_w) + knob_w * 0.5f;
-
-        // Invisible interaction button over the full track area.
-        ImGui::SetCursorScreenPos(
-            ImVec2(track_x0, row_center_y - total_h * 0.5f));
-        ImGui::InvisibleButton("##TimelineScrubber", ImVec2(track_w, total_h));
-        const bool hovered = ImGui::IsItemHovered();
-        const bool active = ImGui::IsItemActive();
-
-        // Handle dragging.
-        if (!locked && (active || (hovered && ImGui::IsMouseDown(
-                                                  ImGuiMouseButton_Left)))) {
-          const float mouse_x = ImGui::GetIO().MousePos.x;
-          if (!tmp_.scrubber_active) {
-            tmp_.scrubber_active = true;
-            if (std::abs(mouse_x - knob_cx) <= knob_w) {
-              tmp_.scrubber_grab_offset = mouse_x - knob_cx;
-            } else {
-              tmp_.scrubber_grab_offset = 0.0f;
-            }
-          }
-
-          const float effective_mouse_x = mouse_x - tmp_.scrubber_grab_offset;
-          const float raw_t = (effective_mouse_x - spine_x0 - knob_w * 0.5f) /
-                              std::max(1.0f, track_w - knob_w);
-          const float clamped_t = std::clamp(raw_t, 0.0f, 1.0f);
-
-          int new_index = current_index;
-          const float snap_eps = std::max(
-              0.02f, std::min(0.05f, 8.0f / std::max(1.0f, track_w - knob_w)));
-          if (clamped_t <= snap_eps ||
-              effective_mouse_x <= spine_x0 + knob_w * 0.5f + 6.0f) {
-            new_index = hist_min;
-          } else if (clamped_t >= 1.0f - snap_eps ||
-                     effective_mouse_x >= spine_x1 - knob_w * 0.5f - 6.0f) {
-            new_index = hist_max;
-          } else {
-            const float inner_t =
-                (clamped_t - snap_eps) / (1.0f - 2.0f * snap_eps);
-            new_index =
-                hist_min +
-                static_cast<int>(std::round(inner_t * (hist_max - hist_min)));
-          }
-
-          if (new_index != current_index) {
-            LoadHistory(new_index);
-            current_index = new_index;
-            t = static_cast<float>(current_index - hist_min) /
-                static_cast<float>(hist_max - hist_min);
-            if (has_data() && current_index == sim_history_.GetIndex()) {
-              curr_time = data()->time;
-              if (curr_time < 0.0) curr_time = 0.0;
-              lh_top_str = FormatTimelineTime(curr_time);
-              lh_top_label = lh_top_str.c_str();
-              const int updated_curr_step =
-                  (has_model() && model()->opt.timestep > 0)
-                      ? static_cast<int>(
-                            std::round(curr_time / model()->opt.timestep))
-                      : 0;
-              lh_bot_str = "(" + std::to_string(updated_curr_step) + ")";
-              lh_bot_label = lh_bot_str.c_str();
-              const float updated_lh_w =
-                  std::max({base_label_w, ImGui::CalcTextSize(lh_top_label).x,
-                            ImGui::CalcTextSize(lh_bot_label).x});
-              if (updated_lh_w > tmp_.timeline_lh_width) {
-                tmp_.timeline_lh_width = updated_lh_w;
-              }
-            }
-          }
-        } else {
-          tmp_.scrubber_active = false;
-        }
-
-        // Draw LH labels (two lines, both right-aligned).
-        const float text_y0 = row_center_y - text_2lines_h * 0.5f;
-        const float text_y1 = text_y0 + text_line_h + custom_line_spacing;
-
-        const float lh_top_x =
-            cursor.x + lh_box_w - ImGui::CalcTextSize(lh_top_label).x;
-        ImGui::SetCursorScreenPos(ImVec2(lh_top_x, text_y0));
-        ImGui::TextUnformatted(lh_top_label);
-
-        const float lh_bot_x =
-            cursor.x + lh_box_w - ImGui::CalcTextSize(lh_bot_label).x;
-        ImGui::SetCursorScreenPos(ImVec2(lh_bot_x, text_y1));
-        ImGui::TextUnformatted(lh_bot_label);
-
-        // Draw RH labels (two lines, both left-aligned).
-        const float rh_x0 = track_x0 + track_w + spacing;
-        ImGui::SetCursorScreenPos(ImVec2(rh_x0, text_y0));
-        ImGui::TextUnformatted(rh_top_label);
-
-        ImGui::SetCursorScreenPos(ImVec2(rh_x0, text_y1));
-        ImGui::TextUnformatted(rh_bot_label);
-
-        // Restore window font scale.
-        ImGui::SetWindowFontScale(1.0f);
-
-        // Draw spine and knob on the draw list.
-        ImDrawList* dl = ImGui::GetWindowDrawList();
-        const ImGuiStyle& style = ImGui::GetStyle();
-
-        // Spine.
-        const ImVec4 scrollbar_bg =
-            ImGui::GetStyle().Colors[ImGuiCol_ScrollbarBg];
-        ImGuiCol bg_col_idx;
-        if (active) {
-          bg_col_idx = ImGuiCol_FrameBgActive;
-        } else if (hovered) {
-          bg_col_idx = ImGuiCol_FrameBgHovered;
-        } else {
-          bg_col_idx = (scrollbar_bg.w > 0.01f) ? ImGuiCol_ScrollbarBg
-                                                : ImGuiCol_FrameBg;
-        }
-        const ImU32 spine_col = ImGui::GetColorU32(bg_col_idx);
-        dl->AddRectFilled(ImVec2(spine_x0, spine_y0),
-                          ImVec2(spine_x1, spine_y1), spine_col,
-                          spine_h * 0.5f);
-
-        // Knob rectangle.
-        const float knob_x0 = knob_cx - knob_w * 0.5f;
-        const float knob_x1 = knob_cx + knob_w * 0.5f;
-        const float knob_y0 = row_center_y - knob_h * 0.5f;
-        const float knob_y1 = row_center_y + knob_h * 0.5f;
-
-        ImU32 knob_col;
-        if (active) {
-          knob_col = ImGui::GetColorU32(ImGuiCol_SliderGrabActive);
-        } else if (hovered) {
-          knob_col = ImGui::GetColorU32(ImGuiCol_SliderGrab);
-        } else {
-          knob_col = ImGui::GetColorU32(ImGuiCol_SliderGrab);
-        }
-        dl->AddRectFilled(ImVec2(knob_x0, knob_y0), ImVec2(knob_x1, knob_y1),
-                          knob_col, style.GrabRounding);
-        // Knob border.
-        dl->AddRect(ImVec2(knob_x0, knob_y0), ImVec2(knob_x1, knob_y1),
-                    ImGui::GetColorU32(ImGuiCol_Border), style.GrabRounding);
-
-        // Advance layout cursor past this row.
-        ImGui::SetCursorScreenPos(ImVec2(cursor.x, cursor.y + total_h));
-      }
+      // Timeline scrubber.
+      TimelineScrubberGui();
     }
 
     // Keyframe controls.
@@ -2202,13 +2205,7 @@ void App::ToolBarGui() {
     platform::StepControlGui(&step_control_, tmp_.speed_index);
 
     ImGui::SameLine(0, separator_width);
-    ImGui::SetNextItemWidth(120);
-    ImGui::BeginDisabled(std::thread::hardware_concurrency() <= 1);
-    if (ImGui::SliderInt("##NumThreads", &ui_.nthread, 0, 8, "%d threads")) {
-      tmp_.update_threadpool = true;
-    }
-    ImGui::EndDisabled();
-    ImGui::SetItemTooltip("%s", "Number of threads in threadpool");
+    TimelineScrubberGui();
 
     ImGui::TableNextColumn();
 
diff --git a/src/experimental/studio/app.h b/src/experimental/studio/app.h
index a66d5e82..266076cd 100644
--- a/src/experimental/studio/app.h
+++ b/src/experimental/studio/app.h
@@ -232,6 +232,7 @@ class App {
 
   void MainMenuGui();
   void ToolBarGui();
+  void TimelineScrubberGui();
   void StatusBarGui();
   void HelpGui();
   void FileDialogGui();