test(cypher): make bounded trails deterministic

Signed-off-by: King Star <mcxin.y@gmail.com>

Author: jstar0

src/store/store.c

@@ -4750,7 +4750,7 @@ static int store_bfs(cbm_store_t *s, int64_t start_id, const char *direction,
                   * a wide shallow layer consumes every row, so prioritize the
                   * recursive hop (depth-first) while retaining deterministic
                   * ordering in the outer result query. */
-                 "  ORDER BY 2 DESC"
+                 "  ORDER BY 2 DESC, 1 ASC, 3 ASC"
                  "  LIMIT %d"
                  ")"
                  "SELECT DISTINCT n.id, n.project, n.label, n.name, n.qualified_name, "

tests/test_cypher.c

@@ -1807,6 +1807,8 @@ TEST(cypher_exec_var_length_explicit_bound_capped) {
     PASS();
 }
 
+/* Pin the relationship-trail contract: a self-loop edge cannot be reused
+ * within one variable-length trail, so *2..2 yields no fabricated match. */
 TEST(cypher_exec_var_length_no_reuse_self_loop) {
     cbm_store_t *s = cbm_store_open_memory();
     cbm_store_upsert_project(s, "test", "/tmp/test");

tests/test_store_search.c

@@ -1078,6 +1078,69 @@ TEST(store_bfs_trail_warns_when_path_rows_are_truncated) {
     PASS();
 }
 
+TEST(store_bfs_trail_preserves_deeper_match_under_hub_budget) {
+    cbm_store_t *s = cbm_store_open_memory();
+    cbm_store_upsert_project(s, "test", "/tmp/test");
+
+    cbm_node_t root = {.project = "test",
+                       .label = "Function",
+                       .name = "root",
+                       .qualified_name = "test.root"};
+    cbm_node_t branch = {.project = "test",
+                         .label = "Function",
+                         .name = "branch",
+                         .qualified_name = "test.branch"};
+    cbm_node_t target = {.project = "test",
+                         .label = "Function",
+                         .name = "target",
+                         .qualified_name = "test.target"};
+    int64_t root_id = cbm_store_upsert_node(s, &root);
+    int64_t branch_id = cbm_store_upsert_node(s, &branch);
+    int64_t target_id = cbm_store_upsert_node(s, &target);
+
+    cbm_edge_t edge = {
+        .project = "test", .source_id = root_id, .target_id = branch_id, .type = "CALLS"};
+    cbm_store_insert_edge(s, &edge);
+    edge.source_id = branch_id;
+    edge.target_id = target_id;
+    cbm_store_insert_edge(s, &edge);
+
+    /* A high-fanout hub must not consume the bounded CTE before a deeper path
+     * is considered; the depth-first queue should still surface `target`. */
+    enum { LEAF_COUNT = 4100 };
+    for (int i = 0; i < LEAF_COUNT; i++) {
+        char name[32];
+        snprintf(name, sizeof(name), "leaf-%d", i);
+        cbm_node_t leaf = {.project = "test",
+                           .label = "Function",
+                           .name = name,
+                           .qualified_name = name};
+        int64_t leaf_id = cbm_store_upsert_node(s, &leaf);
+        edge.source_id = root_id;
+        edge.target_id = leaf_id;
+        cbm_store_insert_edge(s, &edge);
+    }
+
+    const char *types[] = {"CALLS"};
+    cbm_traverse_result_t result = {0};
+    int rc = cbm_store_bfs_trail(s, root_id, "outbound", types, 1, 2, 5000, &result);
+    ASSERT_EQ(rc, CBM_STORE_OK);
+    ASSERT_TRUE(result.truncated);
+
+    bool saw_target = false;
+    for (int i = 0; i < result.visited_count; i++) {
+        if (result.visited[i].node.id == target_id) {
+            saw_target = true;
+            break;
+        }
+    }
+    ASSERT_TRUE(saw_target);
+
+    cbm_store_traverse_free(&result);
+    cbm_store_close(s);
+    PASS();
+}
+
 /* ── BFS cross-service summary ─────────────────────────────────── */
 
 TEST(store_bfs_cross_service_summary) {
@@ -1597,6 +1660,7 @@ SUITE(store_search) {
     RUN_TEST(store_bfs_with_risk_labels);
     RUN_TEST(store_bfs_reachability_is_not_trail_capped);
     RUN_TEST(store_bfs_trail_warns_when_path_rows_are_truncated);
+    RUN_TEST(store_bfs_trail_preserves_deeper_match_under_hub_budget);
     RUN_TEST(store_bfs_cross_service_summary);
     RUN_TEST(store_glob_to_like);
     RUN_TEST(store_extract_like_hints);