Gave up on trying to get the GOAP algorithm to correctly apply the cost structure to competing choices, and instead I take the resulting action list and simply find the next best one based on cost.

ai.cpp

@@ -162,13 +162,28 @@ namespace ai {
     return state.test(state_id(name));
   }
 
-  AIProfile* profile() {
-    return &AIMGR.profile;
+  ai::Action& EntityAI::best_fit() {
+    dbc::check(plan.script.size() > 0, "empty action plan script");
+    int lowest_cost = plan.script[0].cost;
+    size_t best_action = 0;
+
+    for(size_t i = 0; i < plan.script.size(); i++) {
+      auto& action = plan.script[i];
+      if(!action.can_effect(start)) continue;
+
+      if(action.cost < lowest_cost) {
+        lowest_cost = action.cost;
+        best_action = i;
+      }
+    }
+
+    return plan.script[best_action];
   }
 
   bool EntityAI::wants_to(std::string name) {
     ai::check_valid_action(name, "EntityAI::wants_to");
-    return plan.script.size() > 0 && plan.script[0].name == name;
+    dbc::check(plan.script.size() > 0, "empty action plan script");
+    return best_fit().name == name;
   }
 
   bool EntityAI::active() {
@@ -190,4 +205,9 @@ namespace ai {
   void EntityAI::update() {
     plan = ai::plan(script, start, goal);
   }
+
+  AIProfile* profile() {
+    return &AIMGR.profile;
+  }
+
 }