diff --git a/src/controller/testsuite/test.c b/src/controller/testsuite/test.c
index 013fe1e..88da3ba 100644
--- a/src/controller/testsuite/test.c
+++ b/src/controller/testsuite/test.c
@@ -3757,6 +3757,22 @@ static int worker_house_keeping(void* arg)
     return rc;
 }
 
+/* bug-XXXX (disk fill): the persist_* / config_repl / HA test fixtures create
+ * their WAL/snapshot scratch dirs via mkdtemp("/tmp/xce_..._XXXXXX") but their
+ * teardown only frees the persist_t — the directory is never removed. A full
+ * controller_unit_test run therefore leaves ~28G behind in /tmp in under a
+ * minute, filling a 62G root filesystem. Remove only xce_* DIRECTORIES (never
+ * files — the user's /tmp/xce-mcp binary and the suite's own /tmp/xce_test.log
+ * must survive). Run at suite start (stale leftovers from prior runs) and on
+ * exit via atexit (this run). */
+static void clean_test_scratch_dirs(void)
+{
+    if (system("find /tmp -maxdepth 1 -type d -name 'xce_*' "
+               "-exec rm -rf {} + 2>/dev/null") != 0) {
+        /* non-zero only if find is unavailable; cleanup is best-effort */
+    }
+}
+
 int main(int argc, char* argv[])
 {
     struct arguments arguments;
@@ -3769,6 +3785,11 @@ int main(int argc, char* argv[])
     memset(&arguments, 0x0, sizeof(arguments));
     argp_parse(&argp, argc, argv, 0, 0, &arguments);
 
+    /* Bug-XXXX: remove stale test scratch dirs from prior runs, then ensure
+     * this run's scratch dirs are cleaned on exit. */
+    clean_test_scratch_dirs();
+    atexit(clean_test_scratch_dirs);
+
     if (arguments.verbose != 0) {
         loglevel = verbose_to_loglevel(arguments.verbose);
     }