diff --git a/src/jira_hub/mirror.py b/src/jira_hub/mirror.py
index cd97480..a8961ef 100644
--- a/src/jira_hub/mirror.py
+++ b/src/jira_hub/mirror.py
@@ -95,20 +95,24 @@ def set_note(conn, key, fields: dict, updated_by: str) -> dict:
     unknown = set(fields) - set(NOTE_FIELDS)
     if unknown:
         raise ValueError(f"неизвестные поля заметки: {', '.join(sorted(unknown))}")
-    cur = get_note(conn, key) or {"key": key}
-    cur.update(fields)
-    cur["updated_at"], cur["updated_by"] = db.now(), updated_by
-    cols = ["key"] + NOTE_FIELDS + ["updated_at", "updated_by"]
-    conn.execute(f"INSERT INTO issue_note({', '.join(cols)}) VALUES ({', '.join('?' * len(cols))}) "
-                 "ON CONFLICT(key) DO UPDATE SET " + ", ".join(f"{c} = excluded.{c}" for c in cols[1:]),
-                 [cur.get(c) for c in cols])
+    with db.transaction(conn):   # чтение, слияние и запись — атомарно (соединение общее для потоков)
+        cur = get_note(conn, key) or {"key": key}
+        cur.update(fields)
+        cur["updated_at"], cur["updated_by"] = db.now(), updated_by
+        cols = ["key"] + NOTE_FIELDS + ["updated_at", "updated_by"]
+        conn.execute(f"INSERT INTO issue_note({', '.join(cols)}) VALUES ({', '.join('?' * len(cols))}) "
+                     "ON CONFLICT(key) DO UPDATE SET " + ", ".join(f"{c} = excluded.{c}" for c in cols[1:]),
+                     [cur.get(c) for c in cols])
     return get_note(conn, key)
 
 
 def rename_note(conn, old_key, new_key) -> None:
     """После создания задачи: заметка с временного ключа переезжает на настоящий (старая запись под новым ключом,
     если вдруг была, уступает место)."""
-    if get_note(conn, old_key) is None:
+    if old_key == new_key:
         return
-    conn.execute("DELETE FROM issue_note WHERE key = ?", (new_key,))
-    conn.execute("UPDATE issue_note SET key = ? WHERE key = ?", (new_key, old_key))
+    with db.transaction(conn):
+        if get_note(conn, old_key) is None:
+            return
+        conn.execute("DELETE FROM issue_note WHERE key = ?", (new_key,))
+        conn.execute("UPDATE issue_note SET key = ? WHERE key = ?", (new_key, old_key))
diff --git a/tests/test_mirror.py b/tests/test_mirror.py
index d281b5c..d825f62 100644
--- a/tests/test_mirror.py
+++ b/tests/test_mirror.py
@@ -69,3 +69,26 @@ def test_list_issues_filters():
     assert [i["key"] for i in mirror.list_issues(conn, {"q": "A-2"})] == ["A-2"]
     assert mirror.list_issues(conn, {"assignee": "ivanov"})[0]["work_kind"] is None
     assert len(mirror.list_issues(conn, None, limit=1)) == 1
+
+
+def test_rename_note_same_key_keeps_note():
+    conn = db.connect(":memory:")
+    mirror.apply_state(conn, [issue("A-1")], [])
+    mirror.set_note(conn, "A-1", {"fact_status": "В работе"}, "x")
+    mirror.rename_note(conn, "A-1", "A-1")
+    assert mirror.get_note(conn, "A-1")["fact_status"] == "В работе"
+
+
+def test_rename_note_missing_is_noop():
+    conn = db.connect(":memory:")
+    mirror.rename_note(conn, "new:404", "A-9")   # заметки нет — не падает
+    assert mirror.get_note(conn, "new:404") is None
+    assert mirror.get_note(conn, "A-9") is None
+
+
+def test_set_note_partial_keeps_other_fields():
+    conn = db.connect(":memory:")
+    mirror.set_note(conn, "A-1", {"work_kind": "разработка", "done_text": "сделано"}, "x")
+    got = mirror.set_note(conn, "A-1", {"fact_status": "Готово"}, "y")
+    assert got["work_kind"] == "разработка" and got["done_text"] == "сделано"
+    assert got["fact_status"] == "Готово" and got["updated_by"] == "y"