diff --git a/src/main/domain/migrator.test.ts b/src/main/domain/migrator.test.ts
new file mode 100644
index 0000000..b214ff2
--- /dev/null
+++ b/src/main/domain/migrator.test.ts
@@ -0,0 +1,122 @@
+import { test, expect, describe, beforeEach, afterEach } from 'vitest';
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import { openDatabase, type DbHandle } from '../infra/db';
+import { migrateJsonToSqlite } from './migrator';
+
+let tmpDir: string;
+let appDataDir: string;
+let db: DbHandle;
+beforeEach(() => {
+    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'migrator-'));
+    appDataDir = path.join(tmpDir, 'appdata');
+    fs.mkdirSync(appDataDir, { recursive: true });
+    db = openDatabase(path.join(tmpDir, 'app.db'));
+});
+afterEach(() => {
+    db.close();
+    try { fs.rmSync(tmpDir, { recursive: true, force: true }); } catch { /* ignore */ }
+});
+
+function writeJson(name: string, payload: unknown): string {
+    const target = path.join(appDataDir, name);
+    fs.writeFileSync(target, JSON.stringify(payload, null, 2), 'utf-8');
+    return target;
+}
+
+describe('migrateJsonToSqlite', () => {
+    test('no JSON files: writes migrations_applied marker', () => {
+        const result = migrateJsonToSqlite({ db, appDataDir });
+        expect(result.configMigrated).toBe(false);
+        expect(result.queueMigrated).toBe(false);
+        expect(result.downloadedVodsCount).toBe(0);
+        expect(result.streamersCount).toBe(0);
+
+        const marker = db.get<{ name: string }>('SELECT name FROM migrations_applied WHERE name = ?', ['v4-to-v5-jsons']);
+        expect(marker?.name).toBe('v4-to-v5-jsons');
+    });
+
+    test('migrates config.json keys into config_kv', () => {
+        writeJson('config.json', {
+            language: 'de',
+            performance_mode: 'speed',
+            metadata_cache_minutes: 30,
+            downloaded_vod_ids: ['1', '2', '3'],
+            auto_record_streamers: ['foo', 'bar'],
+        });
+        const result = migrateJsonToSqlite({ db, appDataDir });
+        expect(result.configMigrated).toBe(true);
+
+        const lang = db.get<{ value: string }>('SELECT value FROM config_kv WHERE key = ?', ['language']);
+        expect(JSON.parse(lang!.value)).toBe('de');
+
+        const perf = db.get<{ value: string }>('SELECT value FROM config_kv WHERE key = ?', ['performance_mode']);
+        expect(JSON.parse(perf!.value)).toBe('speed');
+    });
+
+    test('migrates downloaded_vod_ids', () => {
+        writeJson('config.json', { downloaded_vod_ids: ['100', '200', '300'] });
+        const result = migrateJsonToSqlite({ db, appDataDir });
+        expect(result.downloadedVodsCount).toBe(3);
+        const rows = db.all<{ vod_id: string }>('SELECT vod_id FROM downloaded_vods ORDER BY vod_id');
+        expect(rows.map(r => r.vod_id)).toEqual(['100', '200', '300']);
+    });
+
+    test('migrates streamers from both auto-record and auto-vod-download lists', () => {
+        writeJson('config.json', {
+            auto_record_streamers: ['Alice', '@bob'],
+            auto_vod_download_streamers: ['bob', 'carol'],
+        });
+        const result = migrateJsonToSqlite({ db, appDataDir });
+        expect(result.streamersCount).toBeGreaterThanOrEqual(3);
+
+        const alice = db.get<{ login: string; auto_record: number }>('SELECT login, auto_record FROM streamers WHERE login = ?', ['alice']);
+        expect(alice?.auto_record).toBe(1);
+
+        const bob = db.get<{ login: string; auto_record: number; auto_vod_download: number }>('SELECT login, auto_record, auto_vod_download FROM streamers WHERE login = ?', ['bob']);
+        expect(bob?.auto_record).toBe(1);
+        expect(bob?.auto_vod_download).toBe(1);
+
+        const carol = db.get<{ login: string; auto_vod_download: number }>('SELECT login, auto_vod_download FROM streamers WHERE login = ?', ['carol']);
+        expect(carol?.auto_vod_download).toBe(1);
+    });
+
+    test('migrates download_queue.json items', () => {
+        writeJson('download_queue.json', [
+            { id: 'q1', status: 'pending', streamer: 'foo', vod_id: 'v1', created_at: 1000, updated_at: 1000 },
+            { id: 'q2', status: 'completed', streamer: 'bar', vod_id: 'v2', created_at: 2000, updated_at: 3000, completed_at: 3000 },
+        ]);
+        const result = migrateJsonToSqlite({ db, appDataDir });
+        expect(result.queueMigrated).toBe(true);
+
+        const all = db.all<{ id: string; status: string }>('SELECT id, status FROM queue_items ORDER BY id');
+        expect(all).toHaveLength(2);
+        expect(all[0].status).toBe('pending');
+        expect(all[1].status).toBe('completed');
+    });
+
+    test('idempotent second run', () => {
+        writeJson('config.json', { downloaded_vod_ids: ['1', '2'] });
+        migrateJsonToSqlite({ db, appDataDir });
+        const result2 = migrateJsonToSqlite({ db, appDataDir });
+        expect(result2.alreadyApplied).toBe(true);
+        const count = db.get<{ c: number }>('SELECT COUNT(*) AS c FROM downloaded_vods');
+        expect(count?.c).toBe(2);
+    });
+
+    test('writes .v4-backup of source JSONs', () => {
+        const configPath = writeJson('config.json', { language: 'en' });
+        migrateJsonToSqlite({ db, appDataDir });
+        expect(fs.existsSync(configPath + '.v4-backup')).toBe(true);
+        expect(fs.readFileSync(configPath + '.v4-backup', 'utf-8')).toContain('"language": "en"');
+    });
+
+    test('malformed JSON is logged + skipped', () => {
+        fs.writeFileSync(path.join(appDataDir, 'config.json'), '{ not valid json', 'utf-8');
+        const result = migrateJsonToSqlite({ db, appDataDir });
+        expect(result.configMigrated).toBe(false);
+        expect(result.errors.length).toBeGreaterThan(0);
+        expect(result.errors[0].source).toBe('config.json');
+    });
+});
diff --git a/src/main/domain/migrator.ts b/src/main/domain/migrator.ts
new file mode 100644
index 0000000..373d9b3
--- /dev/null
+++ b/src/main/domain/migrator.ts
@@ -0,0 +1,201 @@
+import * as fs from 'fs';
+import * as path from 'path';
+import type { DbHandle } from '../infra/db';
+import { normalizeLogin } from './config-normalize';
+
+export interface MigratorOptions {
+    db: DbHandle;
+    appDataDir: string;
+}
+
+export interface MigrationError {
+    source: string;
+    message: string;
+}
+
+export interface MigrationResult {
+    alreadyApplied: boolean;
+    configMigrated: boolean;
+    queueMigrated: boolean;
+    downloadedVodsCount: number;
+    streamersCount: number;
+    errors: MigrationError[];
+}
+
+const MIGRATION_NAME = 'v4-to-v5-jsons';
+
+const CONFIG_KV_KEYS = [
+    'language', 'performance_mode', 'metadata_cache_minutes', 'streamlink_quality',
+    'streamlink_disable_ads', 'download_chat_replay', 'capture_live_chat',
+    'discord_webhook_url', 'discord_notify_live_start', 'discord_notify_live_end',
+    'discord_notify_vod_complete', 'discord_notify_vod_auto_queued',
+    'auto_cleanup_enabled', 'auto_cleanup_days', 'auto_cleanup_target',
+    'auto_cleanup_action', 'log_stream_events', 'auto_vod_download_poll_minutes',
+    'auto_vod_max_age_hours', 'auto_resume_live_recording',
+    'auto_merge_resumed_parts', 'delete_parts_after_merge',
+    'auto_record_poll_seconds', 'filename_template_vod', 'filename_template_parts',
+    'filename_template_clip', 'smart_queue_scheduler', 'prevent_duplicate_downloads',
+    'persist_queue_on_restart', 'auto_resume_queue_on_startup',
+    'notify_on_each_completion',
+] as const;
+
+function backupOnce(srcPath: string): void {
+    const backupPath = srcPath + '.v4-backup';
+    if (!fs.existsSync(backupPath)) {
+        fs.copyFileSync(srcPath, backupPath);
+    }
+}
+
+function migrateConfig(db: DbHandle, configPath: string, errors: MigrationError[]): { ok: boolean; vodCount: number } {
+    try {
+        const raw = fs.readFileSync(configPath, 'utf-8');
+        const config = JSON.parse(raw) as Record<string, unknown>;
+
+        let vodCount = 0;
+        db.transaction(() => {
+            for (const key of CONFIG_KV_KEYS) {
+                if (key in config) {
+                    db.run(
+                        "INSERT OR REPLACE INTO config_kv(key, value, updated_at) VALUES (?, ?, strftime('%s','now'))",
+                        [key, JSON.stringify(config[key])]
+                    );
+                }
+            }
+
+            const vodIds = Array.isArray(config.downloaded_vod_ids) ? config.downloaded_vod_ids : [];
+            for (const id of vodIds) {
+                if (typeof id !== 'string' || !id) continue;
+                db.run('INSERT OR IGNORE INTO downloaded_vods(vod_id) VALUES (?)', [id]);
+                vodCount += 1;
+            }
+
+            const autoRec = Array.isArray(config.auto_record_streamers) ? config.auto_record_streamers : [];
+            for (const s of autoRec) {
+                if (typeof s !== 'string' || !s) continue;
+                const login = normalizeLogin(s);
+                if (!login) continue;
+                db.run(
+                    'INSERT INTO streamers(login, auto_record) VALUES (?, 1) ON CONFLICT(login) DO UPDATE SET auto_record = 1',
+                    [login]
+                );
+            }
+
+            const autoDl = Array.isArray(config.auto_vod_download_streamers) ? config.auto_vod_download_streamers : [];
+            for (const s of autoDl) {
+                if (typeof s !== 'string' || !s) continue;
+                const login = normalizeLogin(s);
+                if (!login) continue;
+                db.run(
+                    'INSERT INTO streamers(login, auto_vod_download) VALUES (?, 1) ON CONFLICT(login) DO UPDATE SET auto_vod_download = 1',
+                    [login]
+                );
+            }
+        });
+
+        backupOnce(configPath);
+        return { ok: true, vodCount };
+    } catch (e) {
+        errors.push({ source: 'config.json', message: e instanceof Error ? e.message : String(e) });
+        return { ok: false, vodCount: 0 };
+    }
+}
+
+function migrateQueue(db: DbHandle, queuePath: string, errors: MigrationError[]): boolean {
+    try {
+        const raw = fs.readFileSync(queuePath, 'utf-8');
+        const queue = JSON.parse(raw);
+        if (!Array.isArray(queue)) return false;
+
+        const now = Math.floor(Date.now() / 1000);
+        db.transaction(() => {
+            for (const rawItem of queue) {
+                if (!rawItem || typeof rawItem !== 'object') continue;
+                const item = rawItem as Record<string, unknown>;
+                const id = typeof item.id === 'string' ? item.id : null;
+                if (!id) continue;
+                db.run(
+                    `INSERT OR REPLACE INTO queue_items
+                     (id, streamer_login, vod_id, clip_id, title, output_path, status,
+                      progress_pct, error_message, created_at, updated_at, completed_at, payload_json)
+                     VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
+                    [
+                        id,
+                        typeof item.streamer === 'string' ? normalizeLogin(item.streamer) : null,
+                        typeof item.vod_id === 'string' ? item.vod_id : null,
+                        typeof item.clip_id === 'string' ? item.clip_id : null,
+                        typeof item.title === 'string' ? item.title : null,
+                        typeof item.output_path === 'string' ? item.output_path : null,
+                        typeof item.status === 'string' ? item.status : 'pending',
+                        typeof item.progress_pct === 'number' ? item.progress_pct : null,
+                        typeof item.error_message === 'string' ? item.error_message : null,
+                        typeof item.created_at === 'number' ? item.created_at : now,
+                        typeof item.updated_at === 'number' ? item.updated_at : now,
+                        typeof item.completed_at === 'number' ? item.completed_at : null,
+                        JSON.stringify(item),
+                    ]
+                );
+            }
+        });
+
+        backupOnce(queuePath);
+        return true;
+    } catch (e) {
+        errors.push({ source: 'download_queue.json', message: e instanceof Error ? e.message : String(e) });
+        return false;
+    }
+}
+
+export function migrateJsonToSqlite(opts: MigratorOptions): MigrationResult {
+    const { db, appDataDir } = opts;
+    const errors: MigrationError[] = [];
+
+    const existing = db.get<{ name: string }>(
+        'SELECT name FROM migrations_applied WHERE name = ?',
+        [MIGRATION_NAME]
+    );
+    if (existing) {
+        return {
+            alreadyApplied: true,
+            configMigrated: false,
+            queueMigrated: false,
+            downloadedVodsCount: 0,
+            streamersCount: 0,
+            errors: [],
+        };
+    }
+
+    let configMigrated = false;
+    let queueMigrated = false;
+    let downloadedVodsCount = 0;
+
+    const configPath = path.join(appDataDir, 'config.json');
+    if (fs.existsSync(configPath)) {
+        const r = migrateConfig(db, configPath, errors);
+        configMigrated = r.ok;
+        downloadedVodsCount = r.vodCount;
+    }
+
+    const queuePath = path.join(appDataDir, 'download_queue.json');
+    if (fs.existsSync(queuePath)) {
+        queueMigrated = migrateQueue(db, queuePath, errors);
+    }
+
+    const streamersCount = db.get<{ c: number }>('SELECT COUNT(*) AS c FROM streamers')?.c ?? 0;
+
+    db.run(
+        'INSERT INTO migrations_applied(name, payload) VALUES (?, ?)',
+        [
+            MIGRATION_NAME,
+            JSON.stringify({ configMigrated, queueMigrated, downloadedVodsCount, streamersCount, errorCount: errors.length }),
+        ]
+    );
+
+    return {
+        alreadyApplied: false,
+        configMigrated,
+        queueMigrated,
+        downloadedVodsCount,
+        streamersCount,
+        errors,
+    };
+}