diff --git a/src/main/domain/token-store.test.ts b/src/main/domain/token-store.test.ts
new file mode 100644
index 0000000..2337899
--- /dev/null
+++ b/src/main/domain/token-store.test.ts
@@ -0,0 +1,120 @@
+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 { MemorySecureStorage } from '../infra/secure-storage';
+import { createTokenStore, type TokenStore } from './token-store';
+
+let tmpDir: string;
+let db: DbHandle;
+let store: TokenStore;
+beforeEach(() => {
+    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'tokens-'));
+    db = openDatabase(path.join(tmpDir, 'app.db'));
+    store = createTokenStore(db, new MemorySecureStorage());
+});
+afterEach(() => {
+    db.close();
+    try { fs.rmSync(tmpDir, { recursive: true, force: true }); } catch { /* ignore */ }
+});
+
+describe('createTokenStore', () => {
+    test('upsert new account returns record with id > 0', () => {
+        const rec = store.upsert({
+            provider: 'twitch',
+            twitchUserId: 'u1',
+            login: 'alice',
+            accessToken: 'aaa.aaa.aaa',
+        });
+        expect(rec.id).toBeGreaterThan(0);
+        expect(rec.login).toBe('alice');
+        expect(rec.provider).toBe('twitch');
+        expect(rec.twitchUserId).toBe('u1');
+    });
+
+    test('upsert same (provider, twitch_user_id) updates, no duplicate row', () => {
+        store.upsert({ provider: 'twitch', twitchUserId: 'u1', login: 'alice', accessToken: 't1' });
+        const updated = store.upsert({ provider: 'twitch', twitchUserId: 'u1', login: 'alice2', accessToken: 't2' });
+        expect(updated.login).toBe('alice2');
+        const all = store.list('twitch');
+        expect(all).toHaveLength(1);
+        expect(all[0].login).toBe('alice2');
+    });
+
+    test('list() returns all accounts, list(provider) filters', () => {
+        store.upsert({ provider: 'twitch', twitchUserId: 'u1', login: 'a', accessToken: 'x' });
+        store.upsert({ provider: 'twitch', twitchUserId: 'u2', login: 'b', accessToken: 'y' });
+        store.upsert({ provider: 'youtube', twitchUserId: undefined, login: 'c', accessToken: 'z' });
+        expect(store.list()).toHaveLength(3);
+        expect(store.list('twitch')).toHaveLength(2);
+        expect(store.list('youtube')).toHaveLength(1);
+    });
+
+    test('getDefault returns null when nothing default', () => {
+        store.upsert({ provider: 'twitch', twitchUserId: 'u1', login: 'a', accessToken: 'x' });
+        expect(store.getDefault('twitch')).toBeNull();
+    });
+
+    test('upsert with isDefault=true makes it default, demotes siblings', () => {
+        const a = store.upsert({ provider: 'twitch', twitchUserId: 'u1', login: 'a', accessToken: 'x', isDefault: true });
+        const b = store.upsert({ provider: 'twitch', twitchUserId: 'u2', login: 'b', accessToken: 'y', isDefault: true });
+
+        const def = store.getDefault('twitch');
+        expect(def?.id).toBe(b.id);
+
+        const aAgain = store.list('twitch').find(r => r.id === a.id);
+        expect(aAgain?.isDefault).toBe(false);
+    });
+
+    test('setDefault toggles is_default exclusivity within provider', () => {
+        const a = store.upsert({ provider: 'twitch', twitchUserId: 'u1', login: 'a', accessToken: 'x', isDefault: true });
+        const b = store.upsert({ provider: 'twitch', twitchUserId: 'u2', login: 'b', accessToken: 'y' });
+
+        store.setDefault(b.id);
+        expect(store.getDefault('twitch')?.id).toBe(b.id);
+
+        const aAgain = store.list('twitch').find(r => r.id === a.id);
+        expect(aAgain?.isDefault).toBe(false);
+    });
+
+    test('getAccessToken returns decrypted plaintext', () => {
+        const rec = store.upsert({ provider: 'twitch', twitchUserId: 'u1', login: 'a', accessToken: 'super-secret-token' });
+        expect(store.getAccessToken(rec.id)).toBe('super-secret-token');
+    });
+
+    test('getRefreshToken returns null if not provided, value if provided', () => {
+        const noRefresh = store.upsert({ provider: 'twitch', twitchUserId: 'u1', login: 'a', accessToken: 't1' });
+        expect(store.getRefreshToken(noRefresh.id)).toBeNull();
+
+        const withRefresh = store.upsert({
+            provider: 'twitch', twitchUserId: 'u2', login: 'b',
+            accessToken: 't2', refreshToken: 'refresh-xyz',
+        });
+        expect(store.getRefreshToken(withRefresh.id)).toBe('refresh-xyz');
+    });
+
+    test('scopes roundtrip as array', () => {
+        const rec = store.upsert({
+            provider: 'twitch', twitchUserId: 'u1', login: 'a',
+            accessToken: 't', scopes: ['user:read:email', 'channel:read:subscriptions'],
+        });
+        expect(rec.scopes).toEqual(['user:read:email', 'channel:read:subscriptions']);
+    });
+
+    test('delete removes the record', () => {
+        const rec = store.upsert({ provider: 'twitch', twitchUserId: 'u1', login: 'a', accessToken: 'x' });
+        store.delete(rec.id);
+        expect(store.list('twitch')).toHaveLength(0);
+        expect(() => store.getAccessToken(rec.id)).toThrow();
+    });
+
+    test('expiresAt roundtrip', () => {
+        const future = Math.floor(Date.now() / 1000) + 3600;
+        const rec = store.upsert({
+            provider: 'twitch', twitchUserId: 'u1', login: 'a',
+            accessToken: 't', expiresAt: future,
+        });
+        expect(rec.expiresAt).toBe(future);
+    });
+});
diff --git a/src/main/domain/token-store.ts b/src/main/domain/token-store.ts
new file mode 100644
index 0000000..9793567
--- /dev/null
+++ b/src/main/domain/token-store.ts
@@ -0,0 +1,203 @@
+import type { DbHandle } from '../infra/db';
+import type { SecureStorage } from '../infra/secure-storage';
+
+export interface TokenRecord {
+    id: number;
+    provider: string;
+    twitchUserId: string | null;
+    login: string | null;
+    displayName: string | null;
+    expiresAt: number | null;
+    scopes: string[];
+    isDefault: boolean;
+    createdAt: number;
+    updatedAt: number;
+}
+
+export interface TokenWriteInput {
+    provider: string;
+    twitchUserId?: string;
+    login?: string;
+    displayName?: string;
+    accessToken: string;
+    refreshToken?: string;
+    expiresAt?: number;
+    scopes?: string[];
+    isDefault?: boolean;
+}
+
+export interface TokenStore {
+    upsert(input: TokenWriteInput): TokenRecord;
+    list(provider?: string): TokenRecord[];
+    getDefault(provider: string): TokenRecord | null;
+    setDefault(id: number): void;
+    getAccessToken(id: number): string;
+    getRefreshToken(id: number): string | null;
+    delete(id: number): void;
+}
+
+interface TokenRow {
+    id: number;
+    provider: string;
+    twitch_user_id: string | null;
+    login: string | null;
+    display_name: string | null;
+    encrypted_access_token: string;
+    encrypted_refresh_token: string | null;
+    expires_at: number | null;
+    scopes_json: string | null;
+    is_default: number;
+    created_at: number;
+    updated_at: number;
+}
+
+function rowToRecord(row: TokenRow): TokenRecord {
+    let scopes: string[] = [];
+    if (row.scopes_json) {
+        try {
+            const parsed = JSON.parse(row.scopes_json);
+            if (Array.isArray(parsed)) {
+                scopes = parsed.filter((s): s is string => typeof s === 'string');
+            }
+        } catch { /* malformed scopes payload — treat as empty */ }
+    }
+    return {
+        id: row.id,
+        provider: row.provider,
+        twitchUserId: row.twitch_user_id,
+        login: row.login,
+        displayName: row.display_name,
+        expiresAt: row.expires_at,
+        scopes,
+        isDefault: row.is_default === 1,
+        createdAt: row.created_at,
+        updatedAt: row.updated_at,
+    };
+}
+
+export function createTokenStore(db: DbHandle, storage: SecureStorage): TokenStore {
+    function getRowOrThrow(id: number): TokenRow {
+        const row = db.get<TokenRow>('SELECT * FROM oauth_accounts WHERE id = ?', [id]);
+        if (!row) throw new Error(`token-store: account id=${id} not found`);
+        return row;
+    }
+
+    return {
+        upsert(input: TokenWriteInput): TokenRecord {
+            const now = Math.floor(Date.now() / 1000);
+            const encryptedAccess = storage.encrypt(input.accessToken);
+            const encryptedRefresh = input.refreshToken !== undefined
+                ? storage.encrypt(input.refreshToken)
+                : null;
+            const scopesJson = input.scopes && input.scopes.length > 0
+                ? JSON.stringify(input.scopes)
+                : null;
+            const isDefault = input.isDefault ? 1 : 0;
+            const twitchUserId = input.twitchUserId ?? null;
+
+            let resultId: number | null = null;
+
+            db.transaction(() => {
+                // Insert or update conditional on UNIQUE(provider, twitch_user_id).
+                // Sqlite's ON CONFLICT braucht den vollstaendigen Konflikt-Ausdruck.
+                db.run(
+                    `INSERT INTO oauth_accounts(
+                        provider, twitch_user_id, login, display_name,
+                        encrypted_access_token, encrypted_refresh_token,
+                        expires_at, scopes_json, is_default, created_at, updated_at
+                     ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+                     ON CONFLICT(provider, twitch_user_id) DO UPDATE SET
+                        login = excluded.login,
+                        display_name = excluded.display_name,
+                        encrypted_access_token = excluded.encrypted_access_token,
+                        encrypted_refresh_token = excluded.encrypted_refresh_token,
+                        expires_at = excluded.expires_at,
+                        scopes_json = excluded.scopes_json,
+                        is_default = excluded.is_default,
+                        updated_at = excluded.updated_at`,
+                    [
+                        input.provider,
+                        twitchUserId,
+                        input.login ?? null,
+                        input.displayName ?? null,
+                        encryptedAccess,
+                        encryptedRefresh,
+                        input.expiresAt ?? null,
+                        scopesJson,
+                        isDefault,
+                        now,
+                        now,
+                    ]
+                );
+
+                // Wenn dieser Eintrag default ist: alle anderen mit gleichem provider auf 0 setzen.
+                if (isDefault === 1) {
+                    db.run(
+                        `UPDATE oauth_accounts
+                         SET is_default = 0, updated_at = ?
+                         WHERE provider = ?
+                           AND NOT (twitch_user_id IS ? AND provider IS ?)`,
+                        [now, input.provider, twitchUserId, input.provider]
+                    );
+                }
+
+                const lookup = db.get<{ id: number }>(
+                    `SELECT id FROM oauth_accounts
+                     WHERE provider = ?
+                       AND (twitch_user_id IS ? OR (twitch_user_id IS NULL AND ? IS NULL))`,
+                    [input.provider, twitchUserId, twitchUserId]
+                );
+                resultId = lookup?.id ?? null;
+            });
+
+            if (resultId === null) throw new Error('token-store: upsert lookup failed');
+            return rowToRecord(getRowOrThrow(resultId));
+        },
+
+        list(provider?: string): TokenRecord[] {
+            const rows = provider
+                ? db.all<TokenRow>('SELECT * FROM oauth_accounts WHERE provider = ? ORDER BY id', [provider])
+                : db.all<TokenRow>('SELECT * FROM oauth_accounts ORDER BY id');
+            return rows.map(rowToRecord);
+        },
+
+        getDefault(provider: string): TokenRecord | null {
+            const row = db.get<TokenRow>(
+                'SELECT * FROM oauth_accounts WHERE provider = ? AND is_default = 1 LIMIT 1',
+                [provider]
+            );
+            return row ? rowToRecord(row) : null;
+        },
+
+        setDefault(id: number): void {
+            const target = getRowOrThrow(id);
+            const now = Math.floor(Date.now() / 1000);
+            db.transaction(() => {
+                db.run(
+                    'UPDATE oauth_accounts SET is_default = 0, updated_at = ? WHERE provider = ?',
+                    [now, target.provider]
+                );
+                db.run(
+                    'UPDATE oauth_accounts SET is_default = 1, updated_at = ? WHERE id = ?',
+                    [now, id]
+                );
+            });
+        },
+
+        getAccessToken(id: number): string {
+            const row = getRowOrThrow(id);
+            return storage.decrypt(row.encrypted_access_token);
+        },
+
+        getRefreshToken(id: number): string | null {
+            const row = getRowOrThrow(id);
+            return row.encrypted_refresh_token
+                ? storage.decrypt(row.encrypted_refresh_token)
+                : null;
+        },
+
+        delete(id: number): void {
+            db.run('DELETE FROM oauth_accounts WHERE id = ?', [id]);
+        },
+    };
+}