# UNDF: UNDF-2026-000000936
--- a/src/dependency_tree.cpp
+++ b/src/dependency_tree.cpp
@@ -1,5 +1,6 @@
 #include "dependency_tree.h"

 #include <algorithm>
+#include <unordered_set>
 #include <array>
 #include <ostream>

@@ -103,14 +104,15 @@
 void dependency_node::inherit_errors()
 {
     std::stack<dependency_node * > nodes_to_check;
     std::set<mod_id> nodes_visited;

     // ... (BFS traversal) ...
     // BEFORE (CWE-407): cur_errors is a copy of all_errors[error_type],
     //   std::find scans it linearly for each node_error. O(E*N).
+    // Also note: cur_errors is a stale copy, dedup is partially broken.
     //
-            std::vector<std::string> cur_errors = all_errors[error_type];
-            for( auto &node_error : node_errors ) {
-                if( std::find( cur_errors.begin(), cur_errors.end(), node_error ) ==
-                    cur_errors.end() ) {
+            std::unordered_set<std::string> cur_errors_set(
+                all_errors[error_type].begin(), all_errors[error_type].end() );
+            for( const auto &node_error : node_errors ) {
+                if( cur_errors_set.find( node_error ) == cur_errors_set.end() ) {
                     all_errors[cerror.first].push_back( node_error );
+                    cur_errors_set.insert( node_error );
                 }
             }

@@ -157,6 +159,7 @@
 std::vector<dependency_node *> dependency_node::get_dependencies_as_nodes()
 {
     std::vector<dependency_node *> dependencies;
     std::vector<dependency_node *> ret;
+    std::unordered_set<dependency_node *> ret_seen;
     std::set<mod_id> found;

     // ... (BFS collection into dependencies) ...
@@ -188,8 +191,9 @@
     // BEFORE (CWE-407): std::find on ret vector for dedup, O(N^2)
     for( std::vector<dependency_node *>::reverse_iterator it =
              dependencies.rbegin();
          it != dependencies.rend(); ++it ) {
-        if( std::find( ret.begin(), ret.end(), *it ) == ret.end() ) {
+        if( ret_seen.find( *it ) == ret_seen.end() ) {
             ret.push_back( *it );
+            ret_seen.insert( *it );
         }
     }

@@ -216,6 +220,7 @@
 std::vector<dependency_node *> dependency_node::get_dependents_as_nodes()
 {
     std::vector<dependency_node *> dependents;
     std::vector<dependency_node *> ret;
+    std::unordered_set<dependency_node *> ret_seen;
     std::set<mod_id> found;

     // ... (BFS collection into dependents) ...
@@ -244,8 +249,9 @@
     // BEFORE (CWE-407): std::find on ret vector for dedup, O(N^2)
     for( dependency_node *&dependent : dependents ) {
-        if( std::find( ret.begin(), ret.end(), dependent ) == ret.end() ) {
+        if( ret_seen.find( dependent ) == ret_seen.end() ) {
             ret.push_back( dependent );
+            ret_seen.insert( dependent );
         }
     }