diff --git a/asap-query-engine/src/precompute_engine/accumulator_factory.rs b/asap-query-engine/src/precompute_engine/accumulator_factory.rs
index d3b41dc..e6005e9 100644
--- a/asap-query-engine/src/precompute_engine/accumulator_factory.rs
+++ b/asap-query-engine/src/precompute_engine/accumulator_factory.rs
@@ -6,11 +6,12 @@ use crate::precompute_operators::{
 };
 use asap_types::aggregation_config::AggregationConfig;
 
-/// Generate the two boilerplate clone-based `AccumulatorUpdater` methods
+/// Generate the boilerplate `AccumulatorUpdater` extraction methods
+/// (`take_accumulator`/`snapshot_accumulator` clone, `into_accumulator` moves)
 /// for updaters whose inner `acc` field implements `Clone + AggregateCore`.
 /// Not applicable to `IncreaseAccumulatorUpdater` (its `acc` is `Option<_>`
 /// with non-trivial `None` handling).
-macro_rules! impl_clone_accumulator_methods {
+macro_rules! impl_accumulator_methods {
     ($acc_field:ident) => {
         fn take_accumulator(&mut self) -> Box<dyn AggregateCore> {
             let result = Box::new(self.$acc_field.clone());
@@ -21,6 +22,15 @@ macro_rules! impl_clone_accumulator_methods {
         fn snapshot_accumulator(&self) -> Box<dyn AggregateCore> {
             Box::new(self.$acc_field.clone())
         }
+
+        fn into_accumulator(self: Box<Self>) -> Box<dyn AggregateCore> {
+            // Consume the updater and MOVE the accumulator out — no clone.
+            // Avoids the expensive `Clone` (a full msgpack serialize/deserialize
+            // round-trip for sketch accumulators) when a pane is evicted at
+            // window close.
+            let this = *self;
+            Box::new(this.$acc_field)
+        }
     };
 }
 
@@ -42,6 +52,16 @@ pub trait AccumulatorUpdater: Send {
     /// Used by pane-based sliding windows to read shared panes.
     fn snapshot_accumulator(&self) -> Box<dyn AggregateCore>;
 
+    /// Consume the updater and return its accumulator BY MOVE, avoiding the
+    /// `Clone` that `take_accumulator`/`snapshot_accumulator` pay (for sketch
+    /// accumulators that clone is a full msgpack serialize/deserialize
+    /// round-trip). Used by `merge_panes_for_window` when a pane is evicted at
+    /// window close. Default falls back to a clone for updaters that can't
+    /// cheaply move their inner accumulator out.
+    fn into_accumulator(self: Box<Self>) -> Box<dyn AggregateCore> {
+        self.snapshot_accumulator()
+    }
+
     /// Reset internal state for reuse (avoids re-allocation).
     fn reset(&mut self);
 
@@ -83,7 +103,7 @@ impl AccumulatorUpdater for SumAccumulatorUpdater {
         self.update_single(value, timestamp_ms);
     }
 
-    impl_clone_accumulator_methods!(acc);
+    impl_accumulator_methods!(acc);
 
     fn reset(&mut self) {
         self.acc = SumAccumulator::new();
@@ -129,7 +149,7 @@ impl AccumulatorUpdater for MinMaxAccumulatorUpdater {
         self.update_single(value, timestamp_ms);
     }
 
-    impl_clone_accumulator_methods!(acc);
+    impl_accumulator_methods!(acc);
 
     fn reset(&mut self) {
         self.acc = if self.is_max {
@@ -210,6 +230,17 @@ impl AccumulatorUpdater for IncreaseAccumulatorUpdater {
         }
     }
 
+    // Hand-written: consume the updater and MOVE the accumulator out (no clone),
+    // mirroring `take_accumulator`'s `Option::take`. Overriding the default
+    // (which clones via `snapshot_accumulator`) keeps this type consistent with
+    // the macro-generated updaters at window close.
+    fn into_accumulator(self: Box<Self>) -> Box<dyn AggregateCore> {
+        let this = *self;
+        Box::new(this.acc.unwrap_or_else(|| {
+            IncreaseAccumulator::new(Measurement::new(0.0), 0, Measurement::new(0.0), 0)
+        }))
+    }
+
     fn reset(&mut self) {
         self.acc = None;
     }
@@ -250,7 +281,7 @@ impl AccumulatorUpdater for KllAccumulatorUpdater {
         self.update_single(value, timestamp_ms);
     }
 
-    impl_clone_accumulator_methods!(acc);
+    impl_accumulator_methods!(acc);
 
     fn reset(&mut self) {
         self.acc = DatasketchesKLLAccumulator::new(self.k);
@@ -297,7 +328,7 @@ impl AccumulatorUpdater for HllAccumulatorUpdater {
         self.update_single(value, timestamp_ms);
     }
 
-    impl_clone_accumulator_methods!(acc);
+    impl_accumulator_methods!(acc);
 
     fn reset(&mut self) {
         self.acc = HllAccumulator::new(self.precision);
@@ -349,7 +380,7 @@ impl AccumulatorUpdater for MultipleSumAccumulatorUpdater {
         self.acc.update(key.clone(), value);
     }
 
-    impl_clone_accumulator_methods!(acc);
+    impl_accumulator_methods!(acc);
 
     fn reset(&mut self) {
         self.acc = MultipleSumAccumulator::new();
@@ -399,7 +430,7 @@ impl AccumulatorUpdater for MultipleMinMaxAccumulatorUpdater {
         self.acc.update(key.clone(), value);
     }
 
-    impl_clone_accumulator_methods!(acc);
+    impl_accumulator_methods!(acc);
 
     fn reset(&mut self) {
         self.acc = if self.is_max {
@@ -466,7 +497,7 @@ impl AccumulatorUpdater for MultipleIncreaseAccumulatorUpdater {
         }
     }
 
-    impl_clone_accumulator_methods!(acc);
+    impl_accumulator_methods!(acc);
 
     fn reset(&mut self) {
         self.acc = MultipleIncreaseAccumulator::new();
@@ -516,7 +547,7 @@ impl AccumulatorUpdater for CmsAccumulatorUpdater {
         self.acc.inner.update(&key.to_semicolon_str(), value);
     }
 
-    impl_clone_accumulator_methods!(acc);
+    impl_accumulator_methods!(acc);
 
     fn reset(&mut self) {
         self.acc = CountMinSketchAccumulator::new(self.row_num, self.col_num);
@@ -566,7 +597,7 @@ impl AccumulatorUpdater for HydraKllAccumulatorUpdater {
         self.acc.update(key, value);
     }
 
-    impl_clone_accumulator_methods!(acc);
+    impl_accumulator_methods!(acc);
 
     fn reset(&mut self) {
         self.acc = HydraKllSketchAccumulator::new(self.row_num, self.col_num, self.k);
diff --git a/asap-query-engine/src/precompute_engine/worker.rs b/asap-query-engine/src/precompute_engine/worker.rs
index 37fc8f3..e72e604 100644
--- a/asap-query-engine/src/precompute_engine/worker.rs
+++ b/asap-query-engine/src/precompute_engine/worker.rs
@@ -704,10 +704,10 @@ fn merge_panes_for_window(
 
     for (i, &ps) in pane_starts.iter().enumerate() {
         let pane_acc = if i == 0 {
-            // Oldest pane: destructive take + evict
+            // Oldest pane: evict and MOVE the accumulator out (no clone).
             active_panes
                 .remove(&ps)
-                .map(|mut updater| updater.take_accumulator())
+                .map(|updater| updater.into_accumulator())
         } else {
             // Shared pane: non-destructive snapshot
             active_panes