diff --git a/src/pipeline/pass_k8s.c b/src/pipeline/pass_k8s.c
index 2ba210f49..3dfa35770 100644
--- a/src/pipeline/pass_k8s.c
+++ b/src/pipeline/pass_k8s.c
@@ -760,6 +760,15 @@ static void k8s_kusts_free(k8s_kusts_t *ks) {
     *ks = (k8s_kusts_t){0};
 }
 
+/* qsort for this file's vectors. An empty vector's items is NULL, and glibc
+ * declares qsort's base nonnull, so sorting it is undefined even with n == 0
+ * (UBSan nonnull-attribute on Linux). Fewer than two elements need no sort. */
+static void k8s_qsort(void *base, size_t n, size_t size, int (*cmp)(const void *, const void *)) {
+    if (base && n > 1) {
+        qsort(base, n, size, cmp);
+    }
+}
+
 static int k8s_cmp_str(const void *a, const void *b) {
     return strcmp(*(const char *const *)a, *(const char *const *)b);
 }
@@ -827,9 +836,9 @@ static void k8s_kusts_wire(cbm_pipeline_ctx_t *ctx, k8s_kusts_t *ks, CBMHashTabl
         }
     }
     for (int i = 0; i < ks->count; i++) {
-        qsort(ks->items[i].files, (size_t)ks->items[i].file_n, sizeof(*ks->items[i].files),
-              k8s_cmp_str);
-        qsort(ks->items[i].kids, (size_t)ks->items[i].kid_n, sizeof(int), k8s_cmp_int);
+        k8s_qsort(ks->items[i].files, (size_t)ks->items[i].file_n, sizeof(*ks->items[i].files),
+                  k8s_cmp_str);
+        k8s_qsort(ks->items[i].kids, (size_t)ks->items[i].kid_n, sizeof(int), k8s_cmp_int);
     }
 }
 
@@ -1006,7 +1015,7 @@ static void k8s_bundles_build(cbm_pipeline_ctx_t *ctx, k8s_kusts_t *ks, k8s_bund
     if (!b->names || !b->members || !b->charts) {
         return;
     }
-    qsort(ks->items, (size_t)ks->count, sizeof(*ks->items), k8s_cmp_kust);
+    k8s_qsort(ks->items, (size_t)ks->count, sizeof(*ks->items), k8s_cmp_kust);
     CBMHashTable *by_path = cbm_ht_create(0);
     if (!by_path) {
         return;
@@ -1345,7 +1354,7 @@ static void k8s_paths_sort_unique(k8s_paths_t *v) {
     if (v->count == 0) {
         return;
     }
-    qsort((void *)v->items, (size_t)v->count, sizeof(*v->items), k8s_cmp_str);
+    k8s_qsort((void *)v->items, (size_t)v->count, sizeof(*v->items), k8s_cmp_str);
     int w = SKIP_ONE;
     for (int i = SKIP_ONE; i < v->count; i++) {
         if (strcmp(v->items[w - SKIP_ONE], v->items[i]) != 0) {
@@ -1522,7 +1531,7 @@ static void k8s_deploys_build(cbm_pipeline_ctx_t *ctx, k8s_kusts_t *ks, k8s_bund
             k8s_dir_members(ks, by_path, &manifests, f->deploys[d].dir, seen, d + SKIP_ONE,
                             &members[d], NULL);
         }
-        qsort(keys, un, sizeof(*keys), k8s_cmp_deploy_key);
+        k8s_qsort(keys, un, sizeof(*keys), k8s_cmp_deploy_key);
         /* deploy d reaches deploy e when e sits in a manifest d applies */
         for (int d = 0; d < n; d++) {
             for (int i = 0; i < members[d].count; i++) {
@@ -1626,7 +1635,7 @@ static void k8s_ids_sort_unique(k8s_ids_t *v) {
     if (v->count < PAIR_LEN) {
         return;
     }
-    qsort(v->items, (size_t)v->count, sizeof(*v->items), k8s_cmp_id);
+    k8s_qsort(v->items, (size_t)v->count, sizeof(*v->items), k8s_cmp_id);
     int w = SKIP_ONE;
     for (int i = SKIP_ONE; i < v->count; i++) {
         if (v->items[i] != v->items[w - SKIP_ONE]) {
@@ -1974,7 +1983,7 @@ static void k8s_link_crds(cbm_pipeline_ctx_t *ctx, k8s_bundles_t *b, const k8s_f
         snprintf(order[i].key, sizeof(order[i].key), "%s/%s", f->crds[i].group, f->crds[i].kind);
         order[i].crd = i;
     }
-    qsort(order, (size_t)f->crd_n, sizeof(*order), k8s_cmp_crd_key);
+    k8s_qsort(order, (size_t)f->crd_n, sizeof(*order), k8s_cmp_crd_key);
     for (int i = f->crd_n - SKIP_ONE; i >= 0; i--) {
         cbm_ht_set(by_type, order[i].key, (void *)(intptr_t)(i + SKIP_ONE)); /* first of run */
     }
@@ -2128,7 +2137,7 @@ static int k8s_cmp_match(const void *a, const void *b) {
  * there is one, is the one it selects. */
 static int k8s_draw_matches(cbm_pipeline_ctx_t *ctx, const k8s_record_array_t *recs,
                             const k8s_record_t *svc, k8s_match_t *m, int n) {
-    qsort(m, (size_t)n, sizeof(*m), k8s_cmp_match);
+    k8s_qsort(m, (size_t)n, sizeof(*m), k8s_cmp_match);
     int edges = 0;
     for (int g = 0; g < n;) {
         int end = g;
diff --git a/tests/test_pipeline.c b/tests/test_pipeline.c
index f9a3c8883..ce5659c72 100644
--- a/tests/test_pipeline.c
+++ b/tests/test_pipeline.c
@@ -3524,11 +3524,18 @@ TEST(incremental_shell_deploy_edit_keeps_its_edges) {
 
 /* Deleting the only file that starts a program leaves no Process node
  * behind -- a full index never makes one without a SPAWNS edge. One script
- * (pass_shell.c) and one Python call (pass_spawns.c) go; the program a kept
- * script starts stays. `legacy`: through the full-load route, else the
- * closure-repair route. Returns the Process count after the deletion, or -1;
- * *route: the route taken. */
-static int incremental_spawner_delete(bool legacy, cbm_incremental_route_t *route) {
+ * (pass_shell.c) and one Python call (pass_spawns.c) start programs; the
+ * program a kept script starts stays.
+ * - `legacy`: both go at once, through the full-load route.
+ * - otherwise in two steps: the script alone goes through closure repair,
+ *   then the Python file, whose deletion the Python namespace admission
+ *   declines (a deleted module's names leave its importers' namespaces), so
+ *   it takes the full route.
+ * Returns the Process count after the last deletion, or -1. *route: the route
+ * of the first (or only) step; *after_script and *python_route: the count and
+ * the route after the script-only step and the Python step (two-step mode). */
+static int incremental_spawner_delete(bool legacy, cbm_incremental_route_t *route,
+                                      int *after_script, cbm_incremental_route_t *python_route) {
     char tmp[256];
     snprintf(tmp, sizeof(tmp), "/tmp/cbm_spawngc_XXXXXX");
     if (!cbm_mkdtemp(tmp)) {
@@ -3545,28 +3552,35 @@ static int incremental_spawner_delete(bool legacy, cbm_incremental_route_t *rout
     char path[512];
     snprintf(path, sizeof(path), "%s/hack/a.sh", tmp);
     (void)remove(path);
+    if (!legacy) {
+        *after_script =
+            k8s_inc_index(tmp, db_path) == 0 ? k8s_inc_count(db_path, processes) : -1;
+        *route = cbm_pipeline_incremental_test_last_route();
+    }
     snprintf(path, sizeof(path), "%s/app.py", tmp);
     (void)remove(path);
 #if defined(CBM_INCREMENTAL_TEST_API) && CBM_INCREMENTAL_TEST_API
     if (legacy) {
         cbm_pipeline_incremental_test_force_legacy_partial_once();
     }
-#else
-    (void)legacy;
 #endif
     int after = k8s_inc_index(tmp, db_path) == 0 ? k8s_inc_count(db_path, processes) : -1;
-    *route = cbm_pipeline_incremental_test_last_route();
+    *(legacy ? route : python_route) = cbm_pipeline_incremental_test_last_route();
     th_rmtree(tmp);
     return full == 3 ? after : -1;
 }
 
 TEST(incremental_deleted_spawner_drops_its_process) {
     cbm_incremental_route_t route = CBM_INCREMENTAL_ROUTE_NONE;
-    int left = incremental_spawner_delete(false, &route);
+    cbm_incremental_route_t python_route = CBM_INCREMENTAL_ROUTE_NONE;
+    int after_script = -1;
+    int left = incremental_spawner_delete(false, &route, &after_script, &python_route);
     ASSERT_EQ(route, CBM_INCREMENTAL_ROUTE_CLOSURE_REPAIR);
+    ASSERT_EQ(after_script, 2); /* tool-a gone; tool-b and tool-c stay */
+    ASSERT_EQ(python_route, CBM_INCREMENTAL_ROUTE_FORCED_FULL);
     ASSERT_EQ(left, 1);
 #if defined(CBM_INCREMENTAL_TEST_API) && CBM_INCREMENTAL_TEST_API
-    left = incremental_spawner_delete(true, &route);
+    left = incremental_spawner_delete(true, &route, &after_script, &python_route);
     ASSERT_EQ(route, CBM_INCREMENTAL_ROUTE_LEGACY_PARTIAL);
     ASSERT_EQ(left, 1);
 #endif