diff --git a/src/components/HabitGrid.jsx b/src/components/HabitGrid.jsx
index 69b1954..f344a2d 100644
--- a/src/components/HabitGrid.jsx
+++ b/src/components/HabitGrid.jsx
@@ -40,9 +40,19 @@ const HabitGrid = ({ habit, onUpdate, fullView = false }) => {
 
   const handleCellClick = async (date) => {
     const dateStr = formatDate(date);
-    // Always call toggleCompletion (handles local/remote), then update UI
-    await toggleCompletion(habit.id, dateStr);
+    // Optimistically update completions for instant UI
+    const habits = JSON.parse(localStorage.getItem('habitgrid_data') || '[]');
+    const idx = habits.findIndex(h => h.id === habit.id);
+    if (idx !== -1) {
+      const completions = Array.isArray(habits[idx].completions) ? [...habits[idx].completions] : [];
+      const cidx = completions.indexOf(dateStr);
+      if (cidx > -1) completions.splice(cidx, 1); else completions.push(dateStr);
+      habits[idx].completions = completions;
+      localStorage.setItem('habitgrid_data', JSON.stringify(habits));
+    }
     onUpdate();
+    // Sync in background
+    toggleCompletion(habit.id, dateStr);
   };
 
   return (
diff --git a/src/components/MiniGrid.jsx b/src/components/MiniGrid.jsx
index 7e95a1e..bf372ae 100644
--- a/src/components/MiniGrid.jsx
+++ b/src/components/MiniGrid.jsx
@@ -69,8 +69,19 @@ const MiniGrid = ({ habit, onUpdate }) => {
     const dateStr = formatDate(date);
     const isTodayCell = isToday(date);
     const wasCompleted = habit.completions.includes(dateStr);
-    await toggleCompletion(habit.id, dateStr);
+    // Optimistically update completions for instant UI
+    const habits = JSON.parse(localStorage.getItem('habitgrid_data') || '[]');
+    const idx = habits.findIndex(h => h.id === habit.id);
+    if (idx !== -1) {
+      const completions = Array.isArray(habits[idx].completions) ? [...habits[idx].completions] : [];
+      const cidx = completions.indexOf(dateStr);
+      if (cidx > -1) completions.splice(cidx, 1); else completions.push(dateStr);
+      habits[idx].completions = completions;
+      localStorage.setItem('habitgrid_data', JSON.stringify(habits));
+    }
     onUpdate();
+    // Sync in background
+    toggleCompletion(habit.id, dateStr);
     // Only show encouragement toast if validating (adding) today's dot
     if (isTodayCell && !wasCompleted) {
       try {