Preserve numeric types for literal subtree port values

When literal values are passed to SubTree ports (not blackboard remapping),
detect numeric types (int64_t, double) before storing them in the child
blackboard. Previously all literals were stored as std::string, which caused
type-mismatch errors in Script expressions that tried to do arithmetic.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: L4co77

src/xml_parsing.cpp

@@ -1147,10 +1147,61 @@ void BT::XMLParser::PImpl::recursivelyCreateSubtree(
         }
         else
         {
-          // constant string: just set that constant value into the BB
+          // constant value: set it into the BB with appropriate type
           // IMPORTANT: this must not be autoremapped!!!
           new_bb->enableAutoRemapping(false);
-          new_bb->set(attr_name, static_cast<std::string>(attr_value));
+          const std::string str_value(attr_value);
+
+          // Check if this port has a strongly-typed declaration in the model.
+          // If so, store as string and let the normal convertFromString<T>
+          // mechanism handle type conversion when the node reads the port.
+          bool port_is_strongly_typed = false;
+          if(subtree_model_it != subtree_models.end())
+          {
+            const auto& model_ports = subtree_model_it->second.ports;
+            auto port_it = model_ports.find(attr_name);
+            if(port_it != model_ports.end() && port_it->second.isStronglyTyped())
+            {
+              port_is_strongly_typed = true;
+            }
+          }
+
+          bool stored = false;
+          // Only attempt numeric detection for ports without a declared type,
+          // so that Script expressions can do arithmetic on literal values.
+          if(!port_is_strongly_typed && !str_value.empty())
+          {
+            // Try integer first (no decimal point, no exponent notation)
+            if(str_value.find('.') == std::string::npos &&
+               str_value.find('e') == std::string::npos &&
+               str_value.find('E') == std::string::npos)
+            {
+              try
+              {
+                const int64_t int_val = convertFromString<int64_t>(str_value);
+                new_bb->set(attr_name, int_val);
+                stored = true;
+              }
+              catch(...)
+              {}
+            }
+            // Try double
+            if(!stored)
+            {
+              try
+              {
+                const double dbl_val = convertFromString<double>(str_value);
+                new_bb->set(attr_name, dbl_val);
+                stored = true;
+              }
+              catch(...)
+              {}
+            }
+          }
+          if(!stored)
+          {
+            new_bb->set(attr_name, str_value);
+          }
           new_bb->enableAutoRemapping(do_autoremap);
         }
       }

tests/gtest_subtree.cpp

@@ -974,3 +974,41 @@ TEST(SubTree, NestedDuplicateNames_ShouldFail)
   // Should throw RuntimeError because of duplicate SubTree names
   ASSERT_THROW((void)factory.createTreeFromText(xml_text), RuntimeError);
 }
+
+// Regression test: literal numeric values passed to subtrees should preserve
+// their numeric type so that Script expressions can do arithmetic.
+TEST(SubTree, LiteralNumericPortsPreserveType)
+{
+  // clang-format off
+  static const char* xml_text = R"(
+<root BTCPP_format="4" main_tree_to_execute="MainTree">
+
+    <BehaviorTree ID="MainTree">
+        <Sequence>
+            <SubTree ID="DoMath" int_val="42" dbl_val="3.14" str_val="hello"
+                     remapped_val="{from_parent}" />
+        </Sequence>
+    </BehaviorTree>
+
+    <BehaviorTree ID="DoMath">
+        <Sequence>
+            <ScriptCondition code=" int_val + 1 == 43 " />
+            <ScriptCondition code=" dbl_val > 3.0 " />
+            <ScriptCondition code=" remapped_val + 1 == 101 " />
+        </Sequence>
+    </BehaviorTree>
+
+</root>
+)";
+  // clang-format on
+
+  BehaviorTreeFactory factory;
+
+  auto tree = factory.createTreeFromText(xml_text);
+
+  // Set the remapped parent value as an integer
+  tree.rootBlackboard()->set("from_parent", 100);
+
+  const auto status = tree.tickWhileRunning();
+  ASSERT_EQ(status, NodeStatus::SUCCESS);
+}