diff --git a/app/service.py b/app/service.py
index 8022b93..098280d 100644
--- a/app/service.py
+++ b/app/service.py
@@ -14,11 +14,18 @@ def list_tasks(status: str | None = None, q: str | None = None) -> list[dict[str
     for task in tasks:
         # Instructor note: intentional bug for the lab.
         # This uses the literal string "status" instead of the query parameter value.
-        if status and task["status"] != "status":
+        if status and task["status"] != status:
             continue
 
         # Instructor note: partial feature for the lab.
         # The route already accepts `q`, but search is not implemented yet.
+        if q:
+            query = q.lower()
+            title = task.get("title", "").lower()
+            description = task.get("description", "").lower()
+            if query not in title and query not in description:
+                continue
+
         filtered.append(task)
 
     return filtered
@@ -53,12 +60,12 @@ def complete_task(task_id: int) -> dict[str, Any] | None:
 
     for task in tasks:
         if task["id"] == task_id:
-            updated_task = dict(task)
-            updated_task["status"] = "done"
-            updated_task["completed_at"] = datetime.now(timezone.utc).isoformat()
+            task["status"] = "done"
+            task["completed_at"] = datetime.now(timezone.utc).isoformat()
+            save_tasks(tasks)
 
             # Instructor note: intentional bug for the lab.
             # The updated task is returned, but the stored list is never updated or saved.
-            return updated_task
+            return task
 
     return None
diff --git a/data/tasks.json b/data/tasks.json
index 8cc3396..7780b8d 100644
--- a/data/tasks.json
+++ b/data/tasks.json
@@ -21,10 +21,10 @@
     "id": 3,
     "title": "Plan workshop agenda",
     "description": "Outline topics for the partner onboarding session.",
-    "status": "open",
+    "status": "done",
     "priority": "medium",
     "created_at": "2026-02-27T11:45:00+00:00",
-    "completed_at": null
+    "completed_at": "2026-07-21T14:00:31.277346+00:00"
   },
   {
     "id": 4,
@@ -35,4 +35,4 @@
     "created_at": "2026-03-01T08:20:00+00:00",
     "completed_at": null
   }
-]
+]
\ No newline at end of file