diff --git a/backend/docs/falukant-character-development.md b/backend/docs/falukant-character-development.md
index 7472c61..8a22aaf 100644
--- a/backend/docs/falukant-character-development.md
+++ b/backend/docs/falukant-character-development.md
@@ -11,6 +11,8 @@ Werte für bestehende Charaktere. Ein Datenbanktrigger initialisiert sie auch f
 neue Charaktere, einschließlich der direkten SQL-Inserts des Daemons für NPCs
 und Neugeborene. Normale Updates, auch das Übergeben von NULL, würfeln bereits
 gespeicherte Werte nicht neu aus. Explizite gültige Änderungen bleiben möglich.
+Die Migration kann auch nach manueller Vorbereitung der Spalten erneut laufen:
+Vorhandene Werte bleiben erhalten, fehlende Spalten und Werte werden ergänzt.
 
 Das vereinfachte Spielmodell verwendet folgende Verteilung:
 
diff --git a/backend/migrations-active/20261104000000-add-character-development-ages.cjs b/backend/migrations-active/20261104000000-add-character-development-ages.cjs
index 665ba61..6573486 100644
--- a/backend/migrations-active/20261104000000-add-character-development-ages.cjs
+++ b/backend/migrations-active/20261104000000-add-character-development-ages.cjs
@@ -5,13 +5,13 @@ module.exports = {
     await queryInterface.sequelize.transaction(async (transaction) => {
       await queryInterface.sequelize.query(`
         ALTER TABLE falukant_data.character
-          ADD COLUMN puberty_start_age SMALLINT,
-          ADD COLUMN fertile_from_age SMALLINT;
+          ADD COLUMN IF NOT EXISTS puberty_start_age SMALLINT,
+          ADD COLUMN IF NOT EXISTS fertile_from_age SMALLINT;
 
         -- Shared by Sequelize and raw daemon INSERTs, including newborns and NPCs.
         -- One real calendar day is one game year. These are game distributions,
         -- not medical predictions or reconstructed medieval population data.
-        CREATE FUNCTION falukant_data.initialize_character_development()
+        CREATE OR REPLACE FUNCTION falukant_data.initialize_character_development()
         RETURNS trigger LANGUAGE plpgsql AS $$
         BEGIN
           IF TG_OP = 'UPDATE' THEN
@@ -30,21 +30,35 @@ module.exports = {
         END;
         $$;
 
+        DROP TRIGGER IF EXISTS initialize_character_development ON falukant_data.character;
         CREATE TRIGGER initialize_character_development
           BEFORE INSERT OR UPDATE ON falukant_data.character
           FOR EACH ROW EXECUTE FUNCTION falukant_data.initialize_character_development();
 
         -- Existing pregnancies and relationships are deliberately untouched.
-        UPDATE falukant_data.character SET puberty_start_age = puberty_start_age;
+        UPDATE falukant_data.character SET puberty_start_age = puberty_start_age
+          WHERE puberty_start_age IS NULL OR fertile_from_age IS NULL;
 
         ALTER TABLE falukant_data.character
           ALTER COLUMN puberty_start_age SET NOT NULL,
-          ALTER COLUMN fertile_from_age SET NOT NULL,
-          ADD CONSTRAINT character_development_ages_valid CHECK (
-            puberty_start_age BETWEEN 8 AND 18
-            AND fertile_from_age > puberty_start_age
-            AND fertile_from_age <= 21
-          );
+          ALTER COLUMN fertile_from_age SET NOT NULL;
+
+        DO $$
+        BEGIN
+          IF NOT EXISTS (
+            SELECT 1 FROM pg_constraint
+            WHERE conrelid = 'falukant_data.character'::regclass
+              AND conname = 'character_development_ages_valid'
+          ) THEN
+            ALTER TABLE falukant_data.character
+              ADD CONSTRAINT character_development_ages_valid CHECK (
+                puberty_start_age BETWEEN 8 AND 18
+                AND fertile_from_age > puberty_start_age
+                AND fertile_from_age <= 21
+              );
+          END IF;
+        END;
+        $$;
       `, { transaction });
     });
   },
diff --git a/backend/tools/characterDevelopment.test.mjs b/backend/tools/characterDevelopment.test.mjs
index 895b62b..4390616 100644
--- a/backend/tools/characterDevelopment.test.mjs
+++ b/backend/tools/characterDevelopment.test.mjs
@@ -71,6 +71,31 @@ test('database migration, persistence and daemon conception paths', {
         await assert.rejects(db.query(`INSERT INTO falukant_data.character
             (puberty_start_age, fertile_from_age) VALUES (12, 11)`));
 
+        await t.test('repeating the migration preserves all existing character data', async () => {
+            const [saved] = await db.query('SELECT * FROM falukant_data.character ORDER BY id');
+            await migration.up(qi);
+            const [repeated] = await db.query('SELECT * FROM falukant_data.character ORDER BY id');
+            assert.deepEqual(repeated, saved);
+        });
+
+        for (const bothColumns of [true, false]) {
+            await t.test(`manually prepared schema with ${bothColumns ? 'both columns' : 'one column'}`, async () => {
+                await migration.down(qi);
+                await db.query(`ALTER TABLE falukant_data.character ADD COLUMN puberty_start_age SMALLINT`);
+                if (bothColumns) {
+                    await db.query(`ALTER TABLE falukant_data.character ADD COLUMN fertile_from_age SMALLINT;
+                        UPDATE falukant_data.character SET fertile_from_age = 13 WHERE id = 1`);
+                }
+                await db.query(`UPDATE falukant_data.character SET puberty_start_age = 10 WHERE id = 1`);
+                await migration.up(qi);
+                const [characters] = await db.query('SELECT * FROM falukant_data.character ORDER BY id');
+                assert.equal(characters[0].puberty_start_age, 10);
+                if (bothColumns) assert.equal(characters[0].fertile_from_age, 13);
+                assert.deepEqual(characters[0].pregnancy_due_at, before[0].pregnancy_due_at);
+                assert.ok(characters.every(c => c.fertile_from_age > c.puberty_start_age));
+            });
+        }
+
         await t.test('daemon checks both parents and preserves already scheduled births', {
             skip: !process.env.DAEMON_SQL_PATH,
         }, async () => {