diff --git a/src/main.ts b/src/main.ts
index 487ec9f..db754cb 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -9,6 +9,18 @@ import { compareUpdateVersions, isNewerUpdateVersion, normalizeUpdateVersion } f
 import { writeFileAtomicSync } from './main/infra/fs-atomic';
 import { parseDuration, formatDuration, formatDurationDashed } from './main/infra/duration';
 import { tBackend as tBackendCore, type BackendMessageKey } from './main/domain/i18n-backend';
+import {
+    normalizeLogin,
+    normalizeAutoRecordPollSeconds,
+    normalizeAutoRecordList,
+    normalizeStreamlinkQuality,
+    normalizeFilenameTemplate,
+    normalizeMetadataCacheMinutes,
+    normalizePerformanceMode,
+    isPlainObject,
+    VALID_STREAMLINK_QUALITIES,
+    type PerformanceMode,
+} from './main/domain/config-normalize';
 import { CustomClip, MergeGroupItem, MergeGroup, QueueItem, DownloadProgress, DownloadResult } from './types';
 import {
     setDebugLogFn, initToolDirs,
@@ -68,7 +80,6 @@ const DEFAULT_RETRY_DELAY_SECONDS = 5;
 const MIN_FILE_BYTES = 256 * 1024;
 const TWITCH_WEB_CLIENT_ID = 'kimne78kx3ncx6brgo4mv6wki5h1ko';
 
-type PerformanceMode = 'stability' | 'balanced' | 'speed';
 type RetryErrorClass = 'network' | 'rate_limit' | 'auth' | 'tooling' | 'integrity' | 'io' | 'validation' | 'unknown';
 type UpdateCheckSource = 'startup' | 'interval' | 'manual';
 type UpdateDownloadSource = 'auto' | 'manual';
@@ -284,72 +295,15 @@ const defaultConfig: Config = {
     delete_parts_after_merge: false
 };
 
-const AUTO_RECORD_POLL_MIN_SECONDS = 30;
-const AUTO_RECORD_POLL_MAX_SECONDS = 1800;
-function normalizeAutoRecordPollSeconds(value: unknown): number {
-    const parsed = Number(value);
-    if (!Number.isFinite(parsed)) return 90;
-    return Math.max(AUTO_RECORD_POLL_MIN_SECONDS, Math.min(AUTO_RECORD_POLL_MAX_SECONDS, Math.floor(parsed)));
-}
-
-function normalizeAutoRecordList(value: unknown): string[] {
-    if (!Array.isArray(value)) return [];
-    const seen = new Set<string>();
-    const out: string[] = [];
-    for (const v of value) {
-        if (typeof v !== 'string') continue;
-        const cleaned = normalizeLogin(v);
-        if (cleaned && !seen.has(cleaned)) {
-            seen.add(cleaned);
-            out.push(cleaned);
-        }
-    }
-    return out;
-}
-
-// Whitelist of streamlink stream specifiers we surface in Settings. The
-// user's choice is passed to streamlink with "best" appended as a fallback
-// (streamlink supports comma-separated stream lists, picks the first match)
-// so a missing quality on the source stream still produces a download.
-const VALID_STREAMLINK_QUALITIES = ['best', 'source', '1080p60', '720p60', '720p', '480p', 'audio_only'] as const;
-
-function normalizeStreamlinkQuality(value: unknown): string {
-    if (typeof value === 'string' && (VALID_STREAMLINK_QUALITIES as readonly string[]).includes(value)) {
-        return value;
-    }
-    return 'best';
-}
-
+// normalize* helpers + VALID_STREAMLINK_QUALITIES + isPlainObject + normalizeLogin
+// kommen aus ./main/domain/config-normalize. getStreamlinkStreamArg bleibt
+// hier, da es config liest.
 function getStreamlinkStreamArg(): string {
     const choice = normalizeStreamlinkQuality(config.streamlink_quality);
     if (choice === 'best') return 'best';
-    // Fall back to "best" if the chosen rendition isn't offered (e.g. an
-    // older stream archived before that resolution existed).
     return `${choice},best`;
 }
 
-function normalizeFilenameTemplate(template: string | undefined, fallback: string): string {
-    const value = (template || '').trim();
-    return value || fallback;
-}
-
-function normalizeMetadataCacheMinutes(value: unknown): number {
-    const parsed = Number(value);
-    if (!Number.isFinite(parsed)) {
-        return DEFAULT_METADATA_CACHE_MINUTES;
-    }
-
-    return Math.max(1, Math.min(120, Math.floor(parsed)));
-}
-
-function normalizePerformanceMode(mode: unknown): PerformanceMode {
-    if (mode === 'stability' || mode === 'balanced' || mode === 'speed') {
-        return mode;
-    }
-
-    return DEFAULT_PERFORMANCE_MODE;
-}
-
 function normalizeConfigTemplates(input: Config): Config {
     // downloaded_vod_ids is bounded so a long-running app doesn't accumulate
     // an unbounded list across years of downloads. Latest entries kept.
@@ -430,10 +384,6 @@ function recordDownloadedVodId(vodId: string): void {
     saveConfig(config);
 }
 
-function isPlainObject(value: unknown): value is Record<string, unknown> {
-    return typeof value === 'object' && value !== null && !Array.isArray(value);
-}
-
 function loadConfig(): Config {
     try {
         if (fs.existsSync(CONFIG_FILE)) {
@@ -1763,10 +1713,6 @@ async function ensureTwitchAuth(forceRefresh = false): Promise<boolean> {
     return await requestTwitchLogin();
 }
 
-function normalizeLogin(input: string): string {
-    return input.trim().replace(/^@+/, '').toLowerCase();
-}
-
 function formatTwitchDurationFromSeconds(totalSeconds: number): string {
     const seconds = Math.max(0, Math.floor(totalSeconds));
     const h = Math.floor(seconds / 3600);
diff --git a/src/main/domain/config-normalize.test.ts b/src/main/domain/config-normalize.test.ts
new file mode 100644
index 0000000..7cbc4e1
--- /dev/null
+++ b/src/main/domain/config-normalize.test.ts
@@ -0,0 +1,183 @@
+import { test, expect, describe } from 'vitest';
+import {
+    normalizeLogin,
+    normalizeAutoRecordPollSeconds,
+    normalizeAutoRecordList,
+    normalizeStreamlinkQuality,
+    normalizeFilenameTemplate,
+    normalizeMetadataCacheMinutes,
+    normalizePerformanceMode,
+    isPlainObject,
+    VALID_STREAMLINK_QUALITIES,
+} from './config-normalize';
+
+describe('normalizeLogin', () => {
+    test('trim + lowercase', () => {
+        expect(normalizeLogin(' Foo ')).toBe('foo');
+    });
+    test('strips single leading @', () => {
+        expect(normalizeLogin('@foo')).toBe('foo');
+    });
+    test('strips multiple leading @', () => {
+        expect(normalizeLogin('@@@foo')).toBe('foo');
+    });
+    test('preserves @ in middle of string', () => {
+        expect(normalizeLogin('foo@bar')).toBe('foo@bar');
+    });
+    test('empty stays empty', () => {
+        expect(normalizeLogin('')).toBe('');
+    });
+});
+
+describe('normalizeAutoRecordPollSeconds', () => {
+    test('default 90 for non-numeric (NaN producer)', () => {
+        // Number('x') === NaN, Number(undefined) === NaN → default 90.
+        // Number(null) === 0 (finite) → clamp to 30, see boundary test below.
+        expect(normalizeAutoRecordPollSeconds('x')).toBe(90);
+        expect(normalizeAutoRecordPollSeconds(undefined)).toBe(90);
+        expect(normalizeAutoRecordPollSeconds({})).toBe(90);
+    });
+    test('null becomes 0 then clamps to 30', () => {
+        expect(normalizeAutoRecordPollSeconds(null)).toBe(30);
+    });
+    test('clamps low to 30', () => {
+        expect(normalizeAutoRecordPollSeconds(5)).toBe(30);
+    });
+    test('clamps high to 1800', () => {
+        expect(normalizeAutoRecordPollSeconds(99999)).toBe(1800);
+    });
+    test('passes valid mid-range', () => {
+        expect(normalizeAutoRecordPollSeconds(120)).toBe(120);
+    });
+    test('floors fractional', () => {
+        expect(normalizeAutoRecordPollSeconds(120.9)).toBe(120);
+    });
+    test('boundary 30 stays', () => {
+        expect(normalizeAutoRecordPollSeconds(30)).toBe(30);
+    });
+    test('boundary 1800 stays', () => {
+        expect(normalizeAutoRecordPollSeconds(1800)).toBe(1800);
+    });
+});
+
+describe('normalizeAutoRecordList', () => {
+    test('empty for non-array', () => {
+        expect(normalizeAutoRecordList(null)).toEqual([]);
+        expect(normalizeAutoRecordList('x')).toEqual([]);
+        expect(normalizeAutoRecordList(undefined)).toEqual([]);
+    });
+    test('empty array stays empty', () => {
+        expect(normalizeAutoRecordList([])).toEqual([]);
+    });
+    test('lowercases + trims + dedupes', () => {
+        expect(normalizeAutoRecordList(['Foo', 'foo', ' BAR '])).toEqual(['foo', 'bar']);
+    });
+    test('strips leading @ (twitch username paste-form)', () => {
+        expect(normalizeAutoRecordList(['@foo', 'foo', '@@bar'])).toEqual(['foo', 'bar']);
+    });
+    test('drops non-string entries', () => {
+        expect(normalizeAutoRecordList(['foo', 123, null, 'bar'])).toEqual(['foo', 'bar']);
+    });
+    test('drops empty strings after normalize', () => {
+        expect(normalizeAutoRecordList(['', '@', '  ', 'foo'])).toEqual(['foo']);
+    });
+});
+
+describe('normalizeStreamlinkQuality', () => {
+    test('all valid values pass through', () => {
+        for (const q of VALID_STREAMLINK_QUALITIES) {
+            expect(normalizeStreamlinkQuality(q)).toBe(q);
+        }
+    });
+    test('invalid string falls back to best', () => {
+        expect(normalizeStreamlinkQuality('foo')).toBe('best');
+    });
+    test('null/undefined/number fall back to best', () => {
+        expect(normalizeStreamlinkQuality(null)).toBe('best');
+        expect(normalizeStreamlinkQuality(undefined)).toBe('best');
+        expect(normalizeStreamlinkQuality(42)).toBe('best');
+    });
+});
+
+describe('normalizeFilenameTemplate', () => {
+    test('valid string used as-is', () => {
+        expect(normalizeFilenameTemplate('{title}.mp4', 'FB')).toBe('{title}.mp4');
+    });
+    test('trims whitespace', () => {
+        expect(normalizeFilenameTemplate('  hi  ', 'FB')).toBe('hi');
+    });
+    test('empty string falls back', () => {
+        expect(normalizeFilenameTemplate('', 'FB')).toBe('FB');
+    });
+    test('whitespace-only falls back', () => {
+        expect(normalizeFilenameTemplate('   ', 'FB')).toBe('FB');
+    });
+    test('undefined falls back', () => {
+        expect(normalizeFilenameTemplate(undefined, 'FB')).toBe('FB');
+    });
+});
+
+describe('normalizeMetadataCacheMinutes', () => {
+    test('default 10 for NaN-producer', () => {
+        expect(normalizeMetadataCacheMinutes('x')).toBe(10);
+        expect(normalizeMetadataCacheMinutes(undefined)).toBe(10);
+        expect(normalizeMetadataCacheMinutes({})).toBe(10);
+    });
+    test('null becomes 0 then clamps to 1', () => {
+        expect(normalizeMetadataCacheMinutes(null)).toBe(1);
+    });
+    test('clamps low to 1', () => {
+        expect(normalizeMetadataCacheMinutes(0)).toBe(1);
+        expect(normalizeMetadataCacheMinutes(-5)).toBe(1);
+    });
+    test('clamps high to 120', () => {
+        expect(normalizeMetadataCacheMinutes(999)).toBe(120);
+    });
+    test('passes valid mid-range', () => {
+        expect(normalizeMetadataCacheMinutes(15)).toBe(15);
+    });
+    test('floors fractional', () => {
+        expect(normalizeMetadataCacheMinutes(15.9)).toBe(15);
+    });
+});
+
+describe('normalizePerformanceMode', () => {
+    test('stability passes', () => {
+        expect(normalizePerformanceMode('stability')).toBe('stability');
+    });
+    test('balanced passes', () => {
+        expect(normalizePerformanceMode('balanced')).toBe('balanced');
+    });
+    test('speed passes', () => {
+        expect(normalizePerformanceMode('speed')).toBe('speed');
+    });
+    test('invalid string falls back to balanced', () => {
+        expect(normalizePerformanceMode('foo')).toBe('balanced');
+    });
+    test('null/undefined fall back to balanced', () => {
+        expect(normalizePerformanceMode(null)).toBe('balanced');
+        expect(normalizePerformanceMode(undefined)).toBe('balanced');
+    });
+});
+
+describe('isPlainObject', () => {
+    test('true for object literal', () => {
+        expect(isPlainObject({})).toBe(true);
+        expect(isPlainObject({ a: 1 })).toBe(true);
+    });
+    test('false for array', () => {
+        expect(isPlainObject([])).toBe(false);
+        expect(isPlainObject([1, 2, 3])).toBe(false);
+    });
+    test('false for null', () => {
+        expect(isPlainObject(null)).toBe(false);
+    });
+    test('false for undefined', () => {
+        expect(isPlainObject(undefined)).toBe(false);
+    });
+    test('false for primitives', () => {
+        expect(isPlainObject('x')).toBe(false);
+        expect(isPlainObject(42)).toBe(false);
+        expect(isPlainObject(true)).toBe(false);
+    });
+});
diff --git a/src/main/domain/config-normalize.ts b/src/main/domain/config-normalize.ts
new file mode 100644
index 0000000..df5f9e1
--- /dev/null
+++ b/src/main/domain/config-normalize.ts
@@ -0,0 +1,67 @@
+// Pure normalizer-Helpers fuer Config-Felder. Keine Side-Effects, keine Globals.
+
+export type PerformanceMode = 'stability' | 'balanced' | 'speed';
+
+export const VALID_STREAMLINK_QUALITIES = ['best', 'source', '1080p60', '720p60', '720p', '480p', 'audio_only'] as const;
+
+const AUTO_RECORD_POLL_MIN_SECONDS = 30;
+const AUTO_RECORD_POLL_MAX_SECONDS = 1800;
+const DEFAULT_METADATA_CACHE_MINUTES = 10;
+const DEFAULT_PERFORMANCE_MODE: PerformanceMode = 'balanced';
+
+/** trim + strip leading @ + lowercase. Verbatim aus altem main.ts. */
+export function normalizeLogin(input: string): string {
+    return input.trim().replace(/^@+/, '').toLowerCase();
+}
+
+export function normalizeAutoRecordPollSeconds(value: unknown): number {
+    const parsed = Number(value);
+    if (!Number.isFinite(parsed)) return 90;
+    return Math.max(AUTO_RECORD_POLL_MIN_SECONDS, Math.min(AUTO_RECORD_POLL_MAX_SECONDS, Math.floor(parsed)));
+}
+
+export function normalizeAutoRecordList(value: unknown): string[] {
+    if (!Array.isArray(value)) return [];
+    const seen = new Set<string>();
+    const out: string[] = [];
+    for (const v of value) {
+        if (typeof v !== 'string') continue;
+        const cleaned = normalizeLogin(v);
+        if (cleaned && !seen.has(cleaned)) {
+            seen.add(cleaned);
+            out.push(cleaned);
+        }
+    }
+    return out;
+}
+
+export function normalizeStreamlinkQuality(value: unknown): string {
+    if (typeof value === 'string' && (VALID_STREAMLINK_QUALITIES as readonly string[]).includes(value)) {
+        return value;
+    }
+    return 'best';
+}
+
+export function normalizeFilenameTemplate(template: string | undefined, fallback: string): string {
+    const value = (template || '').trim();
+    return value || fallback;
+}
+
+export function normalizeMetadataCacheMinutes(value: unknown): number {
+    const parsed = Number(value);
+    if (!Number.isFinite(parsed)) {
+        return DEFAULT_METADATA_CACHE_MINUTES;
+    }
+    return Math.max(1, Math.min(120, Math.floor(parsed)));
+}
+
+export function normalizePerformanceMode(mode: unknown): PerformanceMode {
+    if (mode === 'stability' || mode === 'balanced' || mode === 'speed') {
+        return mode;
+    }
+    return DEFAULT_PERFORMANCE_MODE;
+}
+
+export function isPlainObject(value: unknown): value is Record<string, unknown> {
+    return typeof value === 'object' && value !== null && !Array.isArray(value);
+}