diff --git a/Libs/Project/Project.cpp b/Libs/Project/Project.cpp
index e963cdd999e..289e5638749 100644
--- a/Libs/Project/Project.cpp
+++ b/Libs/Project/Project.cpp
@@ -190,6 +190,18 @@ void Project::set_subjects(const std::vector<std::shared_ptr<Subject>>& subjects
   update_subjects();
 }
 
+//---------------------------------------------------------------------------
+void Project::clear_particle_filenames() {
+  for (auto& subject : subjects_) {
+    if (subject->is_fixed()) {
+      continue;  // fixed subjects' particles are pre-existing inputs, not optimize outputs
+    }
+    subject->set_local_particle_filenames({});
+    subject->set_world_particle_filenames({});
+  }
+  update_subjects();
+}
+
 //---------------------------------------------------------------------------
 void Project::update_subjects() {
   originals_present_ = false;
diff --git a/Libs/Project/Project.h b/Libs/Project/Project.h
index a2bd7556952..3677f569050 100644
--- a/Libs/Project/Project.h
+++ b/Libs/Project/Project.h
@@ -83,6 +83,12 @@ class Project {
 
   void update_subjects();
 
+  //! Clear the local and world particle filenames for all non-fixed subjects.
+  /*! Used when an optimization fails or is aborted so that the project isn't left
+   *  referencing particle files that were never written (#2455). Fixed subjects
+   *  keep their filenames since those particles are pre-existing inputs. */
+  void clear_particle_filenames();
+
   //! Return if originals are present
   bool get_originals_present() const;
 
diff --git a/Studio/Optimize/OptimizeTool.cpp b/Studio/Optimize/OptimizeTool.cpp
index 4def54d7e45..a79a39b009d 100644
--- a/Studio/Optimize/OptimizeTool.cpp
+++ b/Studio/Optimize/OptimizeTool.cpp
@@ -227,6 +227,11 @@ void OptimizeTool::handle_optimize_failed() {
   optimization_is_running_ = false;
   Q_EMIT progress(100);
 
+  // The optimizer assigns output particle filenames to each subject during setup, but on
+  // failure those files are never written. Clear them so saving the project doesn't leave
+  // dangling particle references that make it unreadable on reload (#2455).
+  session_->get_project()->clear_particle_filenames();
+
   std::string duration = QString::number(elapsed_timer_.elapsed() / 1000.0, 'f', 1).toStdString();
   SW_LOG("Optimize Failed.  Duration: " + duration + " seconds");
   Q_EMIT optimize_complete();
diff --git a/Testing/ProjectTests/ProjectTests.cpp b/Testing/ProjectTests/ProjectTests.cpp
index c3ad705ba96..2b884dbaf07 100644
--- a/Testing/ProjectTests/ProjectTests.cpp
+++ b/Testing/ProjectTests/ProjectTests.cpp
@@ -51,6 +51,47 @@ TEST(ProjectTests, conversion_to_json_test) {
   compare_projects(project_compare1, project_compare2);
 }
 
+//---------------------------------------------------------------------------
+// #2455: after a failed/aborted optimization, the project should not be left referencing
+// particle files that were never written. clear_particle_filenames() clears them for
+// non-fixed subjects (fixed subjects keep their pre-existing input particles).
+TEST(ProjectTests, clear_particle_filenames_test) {
+  TestUtils::Instance().prep_temp(std::string(TEST_DATA_DIR) + "/project", "project_clear_particle_filenames_test");
+
+  ProjectHandle project = std::make_shared<Project>();
+  project->load("json_read.swproj");
+
+  auto& subjects = project->get_subjects();
+  ASSERT_GE(subjects.size(), 2);
+
+  // mark the first subject fixed; its particles are pre-existing inputs and must be kept
+  subjects[0]->set_fixed(true);
+  ASSERT_FALSE(subjects[1]->get_world_particle_filenames().empty());
+
+  project->clear_particle_filenames();
+
+  // the fixed subject keeps its particle filenames
+  EXPECT_FALSE(subjects[0]->get_local_particle_filenames().empty());
+  EXPECT_FALSE(subjects[0]->get_world_particle_filenames().empty());
+
+  // non-fixed subjects are cleared
+  for (size_t i = 1; i < subjects.size(); i++) {
+    EXPECT_TRUE(subjects[i]->get_local_particle_filenames().empty());
+    EXPECT_TRUE(subjects[i]->get_world_particle_filenames().empty());
+  }
+
+  // and a saved+reloaded project no longer references the missing particle files
+  project->save("cleared.swproj");
+  ProjectHandle reloaded = std::make_shared<Project>();
+  reloaded->load("cleared.swproj");
+  auto reloaded_subjects = reloaded->get_subjects();
+  ASSERT_EQ(reloaded_subjects.size(), subjects.size());
+  for (size_t i = 1; i < reloaded_subjects.size(); i++) {
+    EXPECT_TRUE(reloaded_subjects[i]->get_local_particle_filenames().empty());
+    EXPECT_TRUE(reloaded_subjects[i]->get_world_particle_filenames().empty());
+  }
+}
+
 //---------------------------------------------------------------------------
 TEST(ProjectTests, conversion_to_excel_test) {
   TestUtils::Instance().prep_temp(std::string(TEST_DATA_DIR) + "/project", "project_convert_to_excel_test");