fix(heal): canonicalize checkpoint integrity digest

crates/heal/src/heal/resume/checkpoint.rs

@@ -615,7 +615,18 @@ impl CheckpointManager {
     fn serialize_without_digest(checkpoint: &ResumeCheckpoint) -> Result<Vec<u8>> {
         let mut unsigned = checkpoint.clone();
         unsigned.integrity_digest = None;
-        serde_json::to_vec(&unsigned).map_err(|e| Error::TaskExecutionFailed {
+        let mut value = serde_json::to_value(&unsigned).map_err(|e| Error::TaskExecutionFailed {
+            message: format!("Failed to serialize checkpoint: {e}"),
+        })?;
+        for field in ["processed_objects", "failed_objects", "skipped_objects"] {
+            let Some(values) = value.get_mut(field).and_then(serde_json::Value::as_array_mut) else {
+                return Err(Error::TaskExecutionFailed {
+                    message: format!("Failed to canonicalize checkpoint field: {field}"),
+                });
+            };
+            values.sort_by(|left, right| left.as_str().cmp(&right.as_str()));
+        }
+        serde_json::to_vec(&value).map_err(|e| Error::TaskExecutionFailed {
             message: format!("Failed to serialize checkpoint: {e}"),
         })
     }

crates/heal/src/heal/resume/tests.rs

@@ -1786,6 +1786,24 @@ async fn checkpoint_integrity_survives_missing_legacy_sidecar() {
     temp_dir.close().unwrap();
 }
 
+#[tokio::test]
+async fn checkpoint_integrity_survives_multi_object_reload() {
+    let (temp_dir, disk) = schema_test_disk().await;
+    let task_id = ResumeUtils::generate_task_id();
+    let manager = CheckpointManager::new(disk.clone(), task_id.clone()).await.unwrap();
+    for index in 0..32 {
+        manager.add_processed_object(format!("processed-{index}")).await.unwrap();
+        manager.add_failed_object(format!("failed-{index}")).await.unwrap();
+        manager.add_skipped_object(format!("skipped-{index}")).await.unwrap();
+    }
+    manager.update_position(2, 9).await.unwrap();
+
+    CheckpointManager::load_from_disk(disk, &task_id)
+        .await
+        .expect("a healthy multi-object checkpoint must survive reload");
+    temp_dir.close().unwrap();
+}
+
 #[tokio::test]
 async fn new_checkpoint_manager_rebuilds_an_empty_snapshot() {
     let (temp_dir, disk) = schema_test_disk().await;