Reclaim drain owns its work: invalidation only bumps a generation, and a generation that moved aborts the tick's commit and its release.

src/shell/view/view.cpp

@@ -62,7 +62,9 @@ bool transportBlocksModeSwitch(ReaProject* proj) {
 
 bool modeApplyInProgress() { return g_applying; }
 
-bool applyMode(ViewModeModel& model, const std::string& targetModeId, ReaProject* proj) {
+namespace {
+
+bool applyModeImpl(ViewModeModel& model, const std::string& targetModeId, ReaProject* proj) {
     if (g_applying) return false;  // see ApplyLatch; same fail-closed shape as the guards below
     ApplyLatch latch;
 
@@ -203,12 +205,26 @@ bool applyMode(ViewModeModel& model, const std::string& targetModeId, ReaProject
     // an undo rolling the model back underneath it.
     noteAppliedState(project, model);
 
-    // Every membership, snapshot and active-mode mutation in the system reaches the
-    // project through this call, so this is the whole invalidation surface: what the FX
-    // chains SHOULD be has just changed, and the reclaimer's queue is a cache of that
-    // intent, never state.
-    invalidateFxReclaim();
     return true;
 }
 
+} // namespace
+
+bool applyMode(ViewModeModel& model, const std::string& targetModeId, ReaProject* proj) {
+    const bool applied = applyModeImpl(model, targetModeId, proj);
+
+    // Every membership, snapshot and active-mode mutation in the system reaches the
+    // project through this call, so this is the whole invalidation surface: the
+    // reclaimer's queue is a cache of what the FX chains SHOULD be, never state.
+    //
+    // Dropped on a REFUSAL too, and that is the load-bearing half. Callers mutate the
+    // model FIRST and reapply to make it visible (design_view_actions' tag/untag/
+    // show-both, render_in_place, the load tick), and every one of them discards this
+    // return — so a refusal is exactly the case where the mutation stands and nothing
+    // else would drop a queue that now converges toward the mode the user just left.
+    // The cost when the refusal followed no mutation is one re-derivation on the timer.
+    invalidateFxReclaim();
+    return applied;
+}
+
 } // namespace reasampler