diff --git a/backend/src/db/api/project_element_defaults.js b/backend/src/db/api/project_element_defaults.js
index b56c316..aaeea2c 100644
--- a/backend/src/db/api/project_element_defaults.js
+++ b/backend/src/db/api/project_element_defaults.js
@@ -239,12 +239,26 @@ class Project_element_defaultsDBApi extends GenericDBApi {
       return [];
     }
 
+    // Dedupe by element_type (keep first occurrence)
+    // Prevents unique constraint violations if global defaults have duplicates
+    const seenTypes = new Set();
+    const dedupedDefaults = globalDefaults.rows.filter((row) => {
+      if (seenTypes.has(row.element_type)) {
+        console.warn(
+          `Duplicate element_type in global defaults: ${row.element_type} (skipping)`,
+        );
+        return false;
+      }
+      seenTypes.add(row.element_type);
+      return true;
+    });
+
     const now = new Date();
     const currentUserId = options.currentUser?.id || null;
 
     // Create project defaults from global defaults
     const projectDefaults = await this.MODEL.bulkCreate(
-      globalDefaults.rows.map((globalDefault) => ({
+      dedupedDefaults.map((globalDefault) => ({
         projectId,
         element_type: globalDefault.element_type,
         name: globalDefault.name,
diff --git a/backend/src/db/api/projects.js b/backend/src/db/api/projects.js
index 9dff528..e57adc9 100644
--- a/backend/src/db/api/projects.js
+++ b/backend/src/db/api/projects.js
@@ -116,19 +116,12 @@ class ProjectsDBApi extends GenericDBApi {
     const project = await super.create(data, options);
 
     // Auto-snapshot global element defaults to the new project
-    try {
-      const Project_element_defaultsDBApi = require('./project_element_defaults');
-      await Project_element_defaultsDBApi.snapshotGlobalDefaults(project.id, {
-        ...options,
-        transaction,
-      });
-    } catch (error) {
-      // Log but don't fail project creation if snapshot fails
-      console.error(
-        'Failed to snapshot global element defaults to project:',
-        error,
-      );
-    }
+    // Errors propagate to service layer → transaction rollback → proper error to client
+    const Project_element_defaultsDBApi = require('./project_element_defaults');
+    await Project_element_defaultsDBApi.snapshotGlobalDefaults(project.id, {
+      ...options,
+      transaction,
+    });
 
     return project;
   }
diff --git a/backend/src/db/migrations/20260331054340-remove-duplicate-element-type-defaults.js b/backend/src/db/migrations/20260331054340-remove-duplicate-element-type-defaults.js
new file mode 100644
index 0000000..94bfb1b
--- /dev/null
+++ b/backend/src/db/migrations/20260331054340-remove-duplicate-element-type-defaults.js
@@ -0,0 +1,65 @@
+'use strict';
+
+/**
+ * Remove duplicate element_type_defaults rows.
+ * Keeps the oldest entry (by createdAt) for each element_type.
+ * This fixes the unique constraint violation during project creation.
+ */
+module.exports = {
+  async up(queryInterface, Sequelize) {
+    // Find duplicate element_types
+    const duplicates = await queryInterface.sequelize.query(
+      `SELECT element_type, COUNT(*) as count
+       FROM element_type_defaults
+       WHERE "deletedAt" IS NULL
+       GROUP BY element_type
+       HAVING COUNT(*) > 1`,
+      { type: Sequelize.QueryTypes.SELECT },
+    );
+
+    if (duplicates.length === 0) {
+      console.log('No duplicate element_type_defaults found.');
+      return;
+    }
+
+    console.log(
+      `Found ${duplicates.length} element_types with duplicates:`,
+      duplicates.map((d) => d.element_type).join(', '),
+    );
+
+    // For each duplicate element_type, keep oldest and delete others
+    for (const dup of duplicates) {
+      // Get all rows for this element_type, ordered by createdAt
+      const rows = await queryInterface.sequelize.query(
+        `SELECT id, "createdAt"
+         FROM element_type_defaults
+         WHERE element_type = :element_type AND "deletedAt" IS NULL
+         ORDER BY "createdAt" ASC`,
+        {
+          replacements: { element_type: dup.element_type },
+          type: Sequelize.QueryTypes.SELECT,
+        },
+      );
+
+      // Keep the first (oldest), delete the rest
+      const idsToDelete = rows.slice(1).map((r) => r.id);
+
+      if (idsToDelete.length > 0) {
+        await queryInterface.sequelize.query(
+          `DELETE FROM element_type_defaults WHERE id IN (:ids)`,
+          { replacements: { ids: idsToDelete } },
+        );
+        console.log(
+          `Deleted ${idsToDelete.length} duplicate(s) for element_type: ${dup.element_type}`,
+        );
+      }
+    }
+
+    console.log('Duplicate removal complete.');
+  },
+
+  async down(_queryInterface, _Sequelize) {
+    // Cannot restore deleted duplicates
+    console.log('Down migration not applicable - duplicates cannot be restored.');
+  },
+};