diff --git a/lib/vector-buffers/src/variants/disk_v2/tests/basic.rs b/lib/vector-buffers/src/variants/disk_v2/tests/basic.rs
index 30cb47d3c265b..ef7c7c848729f 100644
--- a/lib/vector-buffers/src/variants/disk_v2/tests/basic.rs
+++ b/lib/vector-buffers/src/variants/disk_v2/tests/basic.rs
@@ -210,7 +210,11 @@ async fn initial_size_correct_with_multievents() {
             writer.close();
 
             // Now drop our buffer and reopen it.
+            // Yield to allow the background finalizer task to observe the closed
+            // stream and release its Arc<Ledger> (and thus the lock file) before
+            // we attempt to reopen the buffer.
             drop(writer);
+            tokio::task::yield_now().await;
             let (writer, mut reader, ledger, usage) =
                 create_default_buffer_v2_with_usage::<_, MultiEventRecord>(data_dir).await;
             drop(writer);
diff --git a/src/sources/file.rs b/src/sources/file.rs
index 62a95db362f10..df51a5a73788a 100644
--- a/src/sources/file.rs
+++ b/src/sources/file.rs
@@ -2462,12 +2462,23 @@ mod tests {
         inner: impl Future<Output = ()>,
     ) -> Vec<Event> {
         assert_source_compliance(&FILE_SOURCE_TAGS, async move {
-            let (tx, rx) = if acking_mode == Acks {
-                let (tx, rx) = SourceSender::new_test_finalize(EventStatus::Delivered);
-                (tx, rx.boxed())
-            } else {
-                let (tx, rx) = SourceSender::new_test();
-                (tx, rx.boxed())
+            let (tx, rx) = match acking_mode {
+                Acks => {
+                    let (tx, rx) = SourceSender::new_test_finalize(EventStatus::Delivered);
+                    (tx, rx.boxed())
+                }
+                Unfinalized => {
+                    // Use Rejected so that events are finalized but checkpoints
+                    // are NOT updated (only Delivered triggers checkpoint updates).
+                    // This avoids a race where the default Delivered status on drop
+                    // could leak checkpoint writes into the next run.
+                    let (tx, rx) = SourceSender::new_test_finalize(EventStatus::Rejected);
+                    (tx, rx.boxed())
+                }
+                NoAcks => {
+                    let (tx, rx) = SourceSender::new_test();
+                    (tx, rx.boxed())
+                }
             };
 
             let (trigger_shutdown, shutdown, shutdown_done) = ShutdownSignal::new_wired();