diff --git a/core/storage/wal.rs b/core/storage/wal.rs
index a5ad02e51..f95c88b3f 100644
--- a/core/storage/wal.rs
+++ b/core/storage/wal.rs
@@ -2842,4 +2842,117 @@ pub mod test {
             );
         }
     }
+
+    #[test]
+    fn test_wal_full_backfills_all() {
+        let (db, _tmp) = get_database();
+        let conn = db.connect().unwrap();
+
+        // Write some data to put frames in the WAL
+        conn.execute("create table test(id integer primary key, value text)")
+            .unwrap();
+        bulk_inserts(&conn, 8, 4);
+
+        // Ensure frames are flushed to the WAL
+        while let IOResult::IO = conn.pager.borrow_mut().cacheflush().unwrap() {
+            conn.run_once().unwrap();
+        }
+
+        // Snapshot the current mxFrame before running FULL
+        let wal_shared = db.maybe_shared_wal.read().as_ref().unwrap().clone();
+        let mx_before = unsafe { (&*wal_shared.get()).max_frame.load(Ordering::SeqCst) };
+        assert!(mx_before > 0, "expected frames in WAL before FULL");
+
+        // Run FULL checkpoint — must backfill *all* frames up to mx_before
+        let result = {
+            let pager = conn.pager.borrow();
+            let mut wal = pager.wal.as_ref().unwrap().borrow_mut();
+            run_checkpoint_until_done(&mut *wal, &pager, CheckpointMode::Full)
+        };
+
+        assert_eq!(result.num_wal_frames, mx_before);
+        assert_eq!(result.num_checkpointed_frames, mx_before);
+
+        // If your caller does truncation/sync after a full backfill, it may keep a guard.
+        // It's fine to release here to avoid holding locks past the test.
+        let mut result = result;
+        result.release_guard();
+    }
+
+    #[test]
+    fn test_wal_full_waits_for_old_reader_then_succeeds() {
+        let (db, _tmp) = get_database();
+        let writer = db.connect().unwrap();
+        let reader = db.connect().unwrap();
+
+        writer
+            .execute("create table test(id integer primary key, value text)")
+            .unwrap();
+
+        // First commit some data and flush (reader will snapshot here)
+        bulk_inserts(&writer, 2, 3);
+        while let IOResult::IO = writer.pager.borrow_mut().cacheflush().unwrap() {
+            writer.run_once().unwrap();
+        }
+
+        // Start a read transaction pinned at the current snapshot
+        {
+            let pager = reader.pager.borrow_mut();
+            let mut wal = pager.wal.as_ref().unwrap().borrow_mut();
+            let (res, _) = wal.begin_read_tx().unwrap();
+            assert!(matches!(res, LimboResult::Ok));
+        }
+        let r_snapshot = {
+            let pager = reader.pager.borrow();
+            let wal = pager.wal.as_ref().unwrap().borrow();
+            wal.get_max_frame()
+        };
+
+        // Advance WAL beyond the reader's snapshot
+        bulk_inserts(&writer, 3, 4);
+        while let IOResult::IO = writer.pager.borrow_mut().cacheflush().unwrap() {
+            writer.run_once().unwrap();
+        }
+        let mx_now = unsafe {
+            (&*db.maybe_shared_wal.read().as_ref().unwrap().get())
+                .max_frame
+                .load(Ordering::SeqCst)
+        };
+        assert!(mx_now > r_snapshot);
+
+        // FULL must return Busy while a reader is stuck behind
+        {
+            let pager = writer.pager.borrow();
+            let mut wal = pager.wal.as_ref().unwrap().borrow_mut();
+            match wal.checkpoint(&pager, Rc::new(RefCell::new(0)), CheckpointMode::Full) {
+                Ok(IOResult::IO) => {
+                    // Drive any pending IO (should quickly become Busy or Done)
+                    writer.run_once().unwrap();
+                    // Call again to see final state
+                    match wal.checkpoint(&pager, Rc::new(RefCell::new(0)), CheckpointMode::Full) {
+                        Err(LimboError::Busy) => {}
+                        other => panic!("expected Busy from FULL with old reader, got {other:?}"),
+                    }
+                }
+                Err(LimboError::Busy) => {}
+                other => panic!("expected Busy from FULL with old reader, got {other:?}"),
+            }
+        }
+
+        // Release the reader, now full mode should succeed and backfill everything
+        {
+            let pager = reader.pager.borrow();
+            let wal = pager.wal.as_ref().unwrap().borrow();
+            wal.end_read_tx();
+        }
+
+        let result = {
+            let pager = writer.pager.borrow();
+            let mut wal = pager.wal.as_ref().unwrap().borrow_mut();
+            run_checkpoint_until_done(&mut *wal, &pager, CheckpointMode::Full)
+        };
+
+        assert_eq!(result.num_wal_frames, mx_now);
+        assert_eq!(result.num_checkpointed_frames, mx_now);
+    }
 }