From 9b2fcaa53af870b14e1b7a031c2c68749a1b5478 Mon Sep 17 00:00:00 2001
From: Kris Austin <kris.austin@gmail.com>
Date: Fri, 16 Oct 2026 18:12:24 -0500
Subject: [PATCH] fix: "bad allocation" when opening a 2.4 project with a
 custom filament (#16569)

---
 src/libslic3r/Preset.cpp                      |  1 +
 .../libslic3r/test_preset_bundle_loading.cpp  | 31 +++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/src/libslic3r/Preset.cpp b/src/libslic3r/Preset.cpp
index f557348998..4ae928cc95 100644
--- a/src/libslic3r/Preset.cpp
+++ b/src/libslic3r/Preset.cpp
@@ -2293,6 +2293,7 @@ void PresetCollection::load_project_embedded_presets(std::vector<Preset*>& proje
                 BOOST_LOG_TRIVIAL(error) << boost::format("can not find parent for config %1%!")%preset->file;
                 continue;
             }
+            extend_default_config_length(config, false, {});
             preset->config.update_diff_values_to_child_config(config, extruder_id_name, extruder_variant_name, *key_set1, *key_set2);
             //preset->config.apply(std::move(config));
             Preset::normalize(preset->config);
diff --git a/tests/libslic3r/test_preset_bundle_loading.cpp b/tests/libslic3r/test_preset_bundle_loading.cpp
index 47f5c80cca..7ea1452042 100644
--- a/tests/libslic3r/test_preset_bundle_loading.cpp
+++ b/tests/libslic3r/test_preset_bundle_loading.cpp
@@ -985,6 +985,37 @@ TEST_CASE("A user filament synced to the cloud and back keeps its values and uns
     }
 }
 
+TEST_CASE("A project filament storing one value for a per-variant key applies it to every variant", "[Preset][Bundle][Regression]")
+{
+    PresetCollection filaments(Preset::TYPE_FILAMENT, Preset::filament_options(),
+                               static_cast<const PrintRegionConfig &>(FullPrintConfig::defaults()));
+    Preset &parent = add_inmemory_preset(filaments, "Parent Filament");
+    parent.config.set_key_value("filament_extruder_variant", new ConfigOptionStrings({"Direct Drive Standard", "Direct Drive High Flow"}));
+    parent.config.set_key_value("adaptive_pressure_advance_model", new ConfigOptionStrings({"parent standard", "parent high flow"}));
+    parent.config.set_deserialize_strict("pressure_advance", "0.02,0.03");
+    parent.is_system = true;
+
+    // A filament saved before these keys became per-variant lists both variants but stores each key once.
+    const std::string model = "0.025,15.6,5000";
+    DynamicPrintConfig config;
+    config.set_key_value(BBL_JSON_KEY_INHERITS, new ConfigOptionString("Parent Filament"));
+    config.set_key_value("filament_extruder_variant", new ConfigOptionStrings({"Direct Drive Standard", "Direct Drive High Flow"}));
+    config.set_key_value("adaptive_pressure_advance_model", new ConfigOptionStrings({model}));
+    config.set_deserialize_strict("pressure_advance", "0.016");
+    auto embedded                 = std::make_unique<Preset>(Preset::TYPE_FILAMENT, "Project Filament", false);
+    embedded->config              = std::move(config);
+    embedded->is_project_embedded = true;
+
+    std::vector<Preset *>      project_presets{embedded.get()};
+    PresetsConfigSubstitutions substitutions;
+    filaments.load_project_embedded_presets(project_presets, PRESET_FILAMENT_NAME, substitutions, ForwardCompatibilitySubstitutionRule::Disable);
+
+    const Preset *loaded = filaments.find_preset("Project Filament");
+    REQUIRE(loaded != nullptr);
+    CHECK(loaded->config.option<ConfigOptionStrings>("adaptive_pressure_advance_model")->values == std::vector<std::string>{model, model});
+    check_double_vector(loaded->config.option<ConfigOptionFloats>("pressure_advance")->values, {0.016, 0.016});
+}
+
 TEST_CASE("Repeated loads of a user preset directory produce the same presets", "[Preset][Bundle]")
 {
     ScopedTemporaryDir temp_dir;