@@ -667,6 +667,20 @@ async fn topk_pushdown_does_not_reread_delivered_row_group() {
     // source row emitted twice. The correct answer is the 10 smallest-
     // `event_time` non-empty phrases, matching DuckDB / pushdown-off.
     assert_eq!(output.result_rows, 10, "{}", output.description());
+
+    // The test must actually exercise the runtime prune/rebuild path that
+    // caused #24352 (not just a happy-path scan), otherwise a future default or
+    // optimizer change could let it pass without the bug's precondition. Assert
+    // the dynamic filter pruned at least one row group.
+    let pruned = output
+        .row_groups_pruned_dynamic_filter()
+        .expect("`row_groups_pruned_dynamic_filter` metric must be registered");
+    assert!(
+        pruned >= 1,
+        "test must exercise dynamic RG pruning (the #24352 path); pruned={pruned}\n{}",
+        output.description(),
+    );
+
     let formatted = output.pretty_results();
     for p in [
         "p0", "p4096", "p4097", "p4098", "p4099", "p4100", "p4101", "p4102", "p4103",
 
@@ -342,13 +342,18 @@ impl PushDecoderStreamState {
                 .as_ref()
                 .expect("decoder present")
                 .is_at_row_group_boundary();
-            // Before pruning/rebuilding, align `rg_plan` with the row group the
-            // decoder will actually emit next. arrow-rs silently finishes row
-            // groups whose post-predicate selection is empty without handing back
-            // a reader, so without this sync `rg_plan` trails the decoder by one
-            // and a later rebuild can re-read an already-delivered row group
-            // (#24352).
-            if at_boundary && let Err(e) = self.sync_rg_plan_to_decoder_frontier() {
+            // Only the runtime pruner rebuilds the decoder from `rg_plan`, so
+            // only it needs `rg_plan` kept in sync with the decoder frontier.
+            // arrow-rs silently finishes row groups whose post-predicate
+            // selection is empty without handing back a reader, so without this
+            // sync `rg_plan` trails the decoder by one and a rebuild re-reads an
+            // already-delivered row group (#24352). Gating on the pruner also
+            // avoids the O(remaining row groups) cost of `peek_next_row_group()`
+            // on ordinary scans that never rebuild.
+            if at_boundary
+                && self.row_group_pruner.is_some()
+                && let Err(e) = self.sync_rg_plan_to_decoder_frontier()
+            {
                 return Some((Err(e), self));
             }
             if at_boundary && !self.rg_plan.is_empty() {
 
@@ -126,6 +126,14 @@ set datafusion.execution.parquet.pushdown_filters = true;
 statement ok
 set datafusion.execution.target_partitions = 1;
 
+# Both dynamic-filter switches are on by default; set them explicitly so this
+# test keeps exercising the prune/rebuild path even if the defaults change.
+statement ok
+set datafusion.optimizer.enable_dynamic_filter_pushdown = true;
+
+statement ok
+set datafusion.optimizer.enable_topk_dynamic_filter_pushdown = true;
+
 statement ok
 CREATE TABLE q26_src AS
 SELECT
@@ -177,3 +185,9 @@ RESET datafusion.execution.parquet.pushdown_filters;
 
 statement ok
 RESET datafusion.execution.target_partitions;
+
+statement ok
+RESET datafusion.optimizer.enable_dynamic_filter_pushdown;
+
+statement ok
+RESET datafusion.optimizer.enable_topk_dynamic_filter_pushdown;