diff --git a/tui/include/trainlog/web_sessions.h b/tui/include/trainlog/web_sessions.h
index 159688b..7489440 100644
--- a/tui/include/trainlog/web_sessions.h
+++ b/tui/include/trainlog/web_sessions.h
@@ -24,6 +24,12 @@ typedef struct TrainlogWebSessionsPageQuery {
     const char *search;
 } TrainlogWebSessionsPageQuery;
 
+/*
+ * CONTRACT: every successful JSON-producing function below transfers one
+ * heap allocation through output_json; the caller owns it and releases it
+ * with free(). Borrowed input strings need only remain valid for the call.
+ */
+
 /*
  * CONTRACT: database and query strings are borrowed for the call. On success,
  * output_json is heap-owned by the caller and must be released with free().
diff --git a/tui/tests/test_web_sessions.c b/tui/tests/test_web_sessions.c
index 46dca42..422c671 100644
--- a/tui/tests/test_web_sessions.c
+++ b/tui/tests/test_web_sessions.c
@@ -143,6 +143,9 @@ static bool creation_replay_revision_and_pagination(void) {
                                           &updated_size) == TRAINLOG_STATUS_OK);
     CHECK(updated_size > 0U);
     CHECK(scalar(database, "SELECT COUNT(*) FROM session_preparation_revisions") == 2);
+    free(detail);
+    detail = NULL;
+    detail_size = 0U;
     CHECK(trainlog_web_sessions_save_json(database,
                                           NULL,
                                           "",