frontend/src/lib/shared/api.server.spec.ts

@@ -0,0 +1,20 @@
+import { describe, it, expect } from 'vitest';
+import { extractErrorCode } from './api.server';
+
+describe('extractErrorCode', () => {
+	it('returns the code string when error has a code property', () => {
+		expect(extractErrorCode({ code: 'DOCUMENT_NOT_FOUND' })).toBe('DOCUMENT_NOT_FOUND');
+	});
+	it('returns undefined when error is undefined', () => {
+		expect(extractErrorCode(undefined)).toBeUndefined();
+	});
+	it('returns undefined when error is null', () => {
+		expect(extractErrorCode(null)).toBeUndefined();
+	});
+	it('returns undefined when error is a plain string', () => {
+		expect(extractErrorCode('oops')).toBeUndefined();
+	});
+	it('returns undefined when error object has no code property', () => {
+		expect(extractErrorCode({ message: 'fail' })).toBeUndefined();
+	});
+});

frontend/src/lib/shared/api.server.ts

@@ -23,3 +23,11 @@ export function createApiClient(fetch: typeof globalThis.fetch) {
 		fetch
 	});
 }
+
+export interface ApiError {
+	code?: string;
+}
+
+export function extractErrorCode(error: unknown): string | undefined {
+	return (error as ApiError | undefined)?.code;
+}

frontend/src/routes/admin/+layout.server.ts

@@ -1,6 +1,6 @@
 import { error } from '@sveltejs/kit';
 import { env } from '$env/dynamic/private';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 import type { components } from '$lib/generated/api';
 
@@ -34,16 +34,16 @@ export async function load({ fetch, locals }) {
 	]);
 
 	if (!usersResult.response.ok) {
-		const code = (usersResult.error as unknown as { code?: string })?.code;
-		throw error(usersResult.response.status, getErrorMessage(code));
+		throw error(usersResult.response.status, getErrorMessage(extractErrorCode(usersResult.error)));
 	}
 	if (!groupsResult.response.ok) {
-		const code = (groupsResult.error as unknown as { code?: string })?.code;
-		throw error(groupsResult.response.status, getErrorMessage(code));
+		throw error(
+			groupsResult.response.status,
+			getErrorMessage(extractErrorCode(groupsResult.error))
+		);
 	}
 	if (!tagsResult.response.ok) {
-		const code = (tagsResult.error as unknown as { code?: string })?.code;
-		throw error(tagsResult.response.status, getErrorMessage(code));
+		throw error(tagsResult.response.status, getErrorMessage(extractErrorCode(tagsResult.error)));
 	}
 
 	let inviteCount = 0;

frontend/src/routes/admin/groups/[id]/+page.server.ts

@@ -1,6 +1,6 @@
 import { error, fail, redirect } from '@sveltejs/kit';
 import type { PageServerLoad, Actions } from './$types';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 
 export const load: PageServerLoad = async ({ params, parent }) => {
@@ -24,8 +24,9 @@ export const actions: Actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { error: getErrorMessage(code) });
+			return fail(result.response.status, {
+				error: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 
 		return { success: true };
@@ -38,8 +39,9 @@ export const actions: Actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { error: getErrorMessage(code) });
+			return fail(result.response.status, {
+				error: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 
 		throw redirect(303, '/admin/groups');

frontend/src/routes/admin/groups/[id]/page.server.spec.ts

@@ -7,7 +7,8 @@ const mockApi = {
 };
 
 vi.mock('$lib/shared/api.server', () => ({
-	createApiClient: () => mockApi
+	createApiClient: () => mockApi,
+	extractErrorCode: (e: unknown) => (e as { code?: string } | undefined)?.code
 }));
 
 beforeEach(() => vi.clearAllMocks());

frontend/src/routes/admin/groups/layout.server.spec.ts

@@ -1,7 +1,10 @@
 import { describe, expect, it, vi, beforeEach } from 'vitest';
 import { load } from './+layout.server';
 
-vi.mock('$lib/shared/api.server', () => ({ createApiClient: vi.fn() }));
+vi.mock('$lib/shared/api.server', () => ({
+	createApiClient: vi.fn(),
+	extractErrorCode: (e: unknown) => (e as { code?: string } | undefined)?.code
+}));
 
 import { createApiClient } from '$lib/shared/api.server';
 

frontend/src/routes/admin/groups/new/+page.server.ts

@@ -1,6 +1,6 @@
 import { fail, redirect } from '@sveltejs/kit';
 import type { Actions } from './$types';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 
 export const actions: Actions = {
@@ -16,8 +16,9 @@ export const actions: Actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { error: getErrorMessage(code) });
+			return fail(result.response.status, {
+				error: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 
 		throw redirect(303, '/admin/groups');

frontend/src/routes/admin/invites/+page.server.ts

@@ -1,5 +1,5 @@
 import { fail } from '@sveltejs/kit';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 import type { Actions, PageServerLoad } from './$types';
 import type { components } from '$lib/generated/api';
@@ -25,8 +25,7 @@ export const load: PageServerLoad = async ({ url, fetch }) => {
 	let invites: InviteListItem[] = [];
 	let loadError: string | null = null;
 	if (!invitesResult.response.ok) {
-		const code = (invitesResult.error as unknown as { code?: string })?.code;
-		loadError = code ?? 'INTERNAL_ERROR';
+		loadError = extractErrorCode(invitesResult.error) ?? 'INTERNAL_ERROR';
 	} else {
 		invites = (invitesResult.data ?? []) as InviteListItem[];
 	}
@@ -34,8 +33,7 @@ export const load: PageServerLoad = async ({ url, fetch }) => {
 	let groups: UserGroup[] = [];
 	let groupsLoadError: string | null = null;
 	if (!groupsResult.response.ok) {
-		const code = (groupsResult.error as unknown as { code?: string })?.code;
-		groupsLoadError = code ?? 'INTERNAL_ERROR';
+		groupsLoadError = extractErrorCode(groupsResult.error) ?? 'INTERNAL_ERROR';
 	} else {
 		const raw = groupsResult.data ?? [];
 		groups = [...raw].sort((a, b) => a.name.localeCompare(b.name));
@@ -62,8 +60,9 @@ export const actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { createError: code ?? 'INTERNAL_ERROR' });
+			return fail(result.response.status, {
+				createError: extractErrorCode(result.error) ?? 'INTERNAL_ERROR'
+			});
 		}
 
 		return { created: result.data! as InviteListItem };
@@ -78,8 +77,9 @@ export const actions = {
 		const result = await api.DELETE('/api/invites/{id}', { params: { path: { id } } });
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { revokeError: code ?? 'INTERNAL_ERROR' });
+			return fail(result.response.status, {
+				revokeError: extractErrorCode(result.error) ?? 'INTERNAL_ERROR'
+			});
 		}
 
 		return { revoked: id };

frontend/src/routes/admin/layout.server.spec.ts

@@ -1,7 +1,10 @@
 import { describe, expect, it, vi, beforeEach } from 'vitest';
 import { load } from './+layout.server';
 
-vi.mock('$lib/shared/api.server', () => ({ createApiClient: vi.fn() }));
+vi.mock('$lib/shared/api.server', () => ({
+	createApiClient: vi.fn(),
+	extractErrorCode: (e: unknown) => (e as { code?: string } | undefined)?.code
+}));
 
 import { createApiClient } from '$lib/shared/api.server';
 

frontend/src/routes/admin/ocr/+page.server.ts

@@ -1,6 +1,6 @@
 import { error } from '@sveltejs/kit';
 import type { PageServerLoad } from './$types';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 
 export const load: PageServerLoad = async ({ fetch }) => {
@@ -8,8 +8,7 @@ export const load: PageServerLoad = async ({ fetch }) => {
 	const result = await api.GET('/api/ocr/training-info');
 
 	if (!result.response.ok) {
-		const code = (result.error as unknown as { code?: string })?.code;
-		throw error(result.response.status, getErrorMessage(code));
+		throw error(result.response.status, getErrorMessage(extractErrorCode(result.error)));
 	}
 
 	return { trainingInfo: result.data! };

frontend/src/routes/admin/ocr/[personId]/+page.server.ts

@@ -1,6 +1,6 @@
 import { error } from '@sveltejs/kit';
 import type { PageServerLoad } from './$types';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 
 export const load: PageServerLoad = async ({ params, fetch }) => {
@@ -10,8 +10,7 @@ export const load: PageServerLoad = async ({ params, fetch }) => {
 	});
 
 	if (!result.response.ok) {
-		const code = (result.error as unknown as { code?: string })?.code;
-		throw error(result.response.status, getErrorMessage(code));
+		throw error(result.response.status, getErrorMessage(extractErrorCode(result.error)));
 	}
 
 	return { history: result.data!, personId: params.personId };

frontend/src/routes/admin/ocr/[personId]/page.server.spec.ts

@@ -3,7 +3,10 @@ import { load } from './+page.server';
 
 const mockApi = { GET: vi.fn() };
 
-vi.mock('$lib/shared/api.server', () => ({ createApiClient: () => mockApi }));
+vi.mock('$lib/shared/api.server', () => ({
+	createApiClient: () => mockApi,
+	extractErrorCode: (e: unknown) => (e as { code?: string } | undefined)?.code
+}));
 
 beforeEach(() => vi.clearAllMocks());
 

frontend/src/routes/admin/ocr/global/+page.server.ts

@@ -1,6 +1,6 @@
 import { error } from '@sveltejs/kit';
 import type { PageServerLoad } from './$types';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 
 export const load: PageServerLoad = async ({ fetch }) => {
@@ -8,8 +8,7 @@ export const load: PageServerLoad = async ({ fetch }) => {
 	const result = await api.GET('/api/ocr/training-info/global');
 
 	if (!result.response.ok) {
-		const code = (result.error as unknown as { code?: string })?.code;
-		throw error(result.response.status, getErrorMessage(code));
+		throw error(result.response.status, getErrorMessage(extractErrorCode(result.error)));
 	}
 
 	return { history: result.data! };

frontend/src/routes/admin/ocr/global/page.server.spec.ts

@@ -3,7 +3,10 @@ import { load } from './+page.server';
 
 const mockApi = { GET: vi.fn() };
 
-vi.mock('$lib/shared/api.server', () => ({ createApiClient: () => mockApi }));
+vi.mock('$lib/shared/api.server', () => ({
+	createApiClient: () => mockApi,
+	extractErrorCode: (e: unknown) => (e as { code?: string } | undefined)?.code
+}));
 
 beforeEach(() => vi.clearAllMocks());
 

frontend/src/routes/admin/ocr/page.server.spec.ts

@@ -3,7 +3,10 @@ import { load } from './+page.server';
 
 const mockApi = { GET: vi.fn() };
 
-vi.mock('$lib/shared/api.server', () => ({ createApiClient: () => mockApi }));
+vi.mock('$lib/shared/api.server', () => ({
+	createApiClient: () => mockApi,
+	extractErrorCode: (e: unknown) => (e as { code?: string } | undefined)?.code
+}));
 
 beforeEach(() => vi.clearAllMocks());
 

frontend/src/routes/admin/tags/[id]/+page.server.ts

@@ -1,6 +1,6 @@
 import { error, fail, redirect } from '@sveltejs/kit';
 import type { PageServerLoad, Actions } from './$types';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 
 export const load: PageServerLoad = async ({ params, parent, url }) => {
@@ -25,8 +25,9 @@ export const actions: Actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { error: getErrorMessage(code) });
+			return fail(result.response.status, {
+				error: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 
 		return { success: true };
@@ -43,8 +44,9 @@ export const actions: Actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { error: getErrorMessage(code) });
+			return fail(result.response.status, {
+				error: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 
 		throw redirect(303, `/admin/tags/${result.data!.id}?merged=1`);
@@ -65,8 +67,9 @@ export const actions: Actions = {
 					});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { error: getErrorMessage(code) });
+			return fail(result.response.status, {
+				error: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 
 		throw redirect(303, '/admin/tags');

frontend/src/routes/admin/tags/[id]/page.server.spec.ts

@@ -8,7 +8,8 @@ const mockApi = {
 };
 
 vi.mock('$lib/shared/api.server', () => ({
-	createApiClient: () => mockApi
+	createApiClient: () => mockApi,
+	extractErrorCode: (e: unknown) => (e as { code?: string } | undefined)?.code
 }));
 
 beforeEach(() => vi.clearAllMocks());

frontend/src/routes/admin/tags/layout.server.spec.ts

@@ -1,7 +1,10 @@
 import { describe, expect, it, vi, beforeEach } from 'vitest';
 import { load } from './+layout.server';
 
-vi.mock('$lib/shared/api.server', () => ({ createApiClient: vi.fn() }));
+vi.mock('$lib/shared/api.server', () => ({
+	createApiClient: vi.fn(),
+	extractErrorCode: (e: unknown) => (e as { code?: string } | undefined)?.code
+}));
 
 import { createApiClient } from '$lib/shared/api.server';
 

frontend/src/routes/admin/users/[id]/+page.server.ts

@@ -1,6 +1,6 @@
 import { error, fail, redirect } from '@sveltejs/kit';
 import type { PageServerLoad, Actions } from './$types';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 import type { components } from '$lib/generated/api';
 
@@ -55,8 +55,9 @@ export const actions: Actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { error: getErrorMessage(code) });
+			return fail(result.response.status, {
+				error: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 
 		return { success: true };
@@ -69,8 +70,9 @@ export const actions: Actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { error: getErrorMessage(code) });
+			return fail(result.response.status, {
+				error: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 
 		throw redirect(303, '/admin/users');

frontend/src/routes/admin/users/[id]/page.server.spec.ts

@@ -4,7 +4,10 @@ vi.mock('$env/dynamic/private', () => ({
 	env: { API_INTERNAL_URL: 'http://localhost:8080' }
 }));
 
-vi.mock('$lib/shared/api.server', () => ({ createApiClient: vi.fn() }));
+vi.mock('$lib/shared/api.server', () => ({
+	createApiClient: vi.fn(),
+	extractErrorCode: (e: unknown) => (e as { code?: string } | undefined)?.code
+}));
 
 import { load, actions } from './+page.server';
 import { createApiClient } from '$lib/shared/api.server';

frontend/src/routes/admin/users/layout.server.spec.ts

@@ -1,7 +1,10 @@
 import { describe, expect, it, vi, beforeEach } from 'vitest';
 import { load } from './+layout.server';
 
-vi.mock('$lib/shared/api.server', () => ({ createApiClient: vi.fn() }));
+vi.mock('$lib/shared/api.server', () => ({
+	createApiClient: vi.fn(),
+	extractErrorCode: (e: unknown) => (e as { code?: string } | undefined)?.code
+}));
 
 import { createApiClient } from '$lib/shared/api.server';
 

frontend/src/routes/admin/users/new/+page.server.ts

@@ -1,6 +1,6 @@
 import { error, fail, redirect } from '@sveltejs/kit';
 import type { PageServerLoad, Actions } from './$types';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 
 export const load: PageServerLoad = async ({ fetch, locals }) => {
@@ -35,8 +35,9 @@ export const actions: Actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { error: getErrorMessage(code) });
+			return fail(result.response.status, {
+				error: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 
 		throw redirect(303, '/admin/users');

frontend/src/routes/aktivitaeten/page.server.spec.ts

@@ -6,7 +6,8 @@ const mockApi = {
 };
 
 vi.mock('$lib/shared/api.server', () => ({
-	createApiClient: () => mockApi
+	createApiClient: () => mockApi,
+	extractErrorCode: (e: unknown) => (e as { code?: string } | undefined)?.code
 }));
 
 function buildUrl(search = ''): URL {

frontend/src/routes/briefwechsel/+page.server.ts

@@ -1,6 +1,6 @@
 import { error } from '@sveltejs/kit';
 import type { components } from '$lib/generated/api';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 
 export async function load({ url, fetch, locals }) {
@@ -39,8 +39,7 @@ export async function load({ url, fetch, locals }) {
 				})
 				.then((result) => {
 					if (!result.response.ok) {
-						const code = (result.error as unknown as { code?: string })?.code;
-						throw error(result.response.status, getErrorMessage(code));
+						throw error(result.response.status, getErrorMessage(extractErrorCode(result.error)));
 					}
 					documents = result.data ?? [];
 				})
@@ -49,8 +48,7 @@ export async function load({ url, fetch, locals }) {
 		requests.push(
 			api.GET('/api/persons/{id}', { params: { path: { id: senderId } } }).then((result) => {
 				if (!result.response.ok) {
-					const code = (result.error as unknown as { code?: string })?.code;
-					throw error(result.response.status, getErrorMessage(code));
+					throw error(result.response.status, getErrorMessage(extractErrorCode(result.error)));
 				}
 				const p = result.data as { displayName: string } | undefined;
 				if (p) senderName = p.displayName;
@@ -62,8 +60,7 @@ export async function load({ url, fetch, locals }) {
 		requests.push(
 			api.GET('/api/persons/{id}', { params: { path: { id: receiverId } } }).then((result) => {
 				if (!result.response.ok) {
-					const code = (result.error as unknown as { code?: string })?.code;
-					throw error(result.response.status, getErrorMessage(code));
+					throw error(result.response.status, getErrorMessage(extractErrorCode(result.error)));
 				}
 				const p = result.data as { displayName: string } | undefined;
 				if (p) receiverName = p.displayName;

frontend/src/routes/briefwechsel/page.server.spec.ts

@@ -1,7 +1,10 @@
 import { describe, expect, it, vi, beforeEach } from 'vitest';
 import { load } from './+page.server';
 
-vi.mock('$lib/shared/api.server', () => ({ createApiClient: vi.fn() }));
+vi.mock('$lib/shared/api.server', () => ({
+	createApiClient: vi.fn(),
+	extractErrorCode: (e: unknown) => (e as { code?: string } | undefined)?.code
+}));
 vi.mock('$lib/shared/errors', () => ({
 	getErrorMessage: (code: string) => code ?? 'Unknown error'
 }));

frontend/src/routes/documents/+page.server.ts

@@ -1,5 +1,5 @@
 import { redirect } from '@sveltejs/kit';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 import type { components } from '$lib/generated/api';
 
@@ -103,8 +103,7 @@ export async function load({ url, fetch }) {
 	}
 
 	const errorMessage: string | null = !result.response.ok
-		? (getErrorMessage((result.error as unknown as { code?: string })?.code) ??
-			'Daten konnten nicht geladen werden.')
+		? (getErrorMessage(extractErrorCode(result.error)) ?? 'Daten konnten nicht geladen werden.')
 		: null;
 
 	return {

frontend/src/routes/documents/[id]/+page.server.ts

@@ -1,5 +1,5 @@
 import { error, redirect } from '@sveltejs/kit';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 import { inferredRelationshipLabel } from '$lib/person/relationshipLabels';
 
@@ -17,8 +17,7 @@ export async function load({ params, fetch }) {
 	if (docResult.response.status === 401) throw redirect(302, '/login');
 
 	if (!docResult.response.ok) {
-		const code = (docResult.error as unknown as { code?: string })?.code;
-		throw error(docResult.response.status, getErrorMessage(code));
+		throw error(docResult.response.status, getErrorMessage(extractErrorCode(docResult.error)));
 	}
 
 	const document = docResult.data!;

frontend/src/routes/documents/[id]/edit/+page.server.ts

@@ -1,6 +1,6 @@
 import { error, fail, redirect } from '@sveltejs/kit';
 import { env } from '$env/dynamic/private';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { parseBackendError, getErrorMessage } from '$lib/shared/errors';
 
 export async function load({
@@ -30,8 +30,7 @@ export async function load({
 	]);
 
 	if (!docResult.response.ok) {
-		const code = (docResult.error as unknown as { code?: string })?.code;
-		throw error(docResult.response.status, getErrorMessage(code));
+		throw error(docResult.response.status, getErrorMessage(extractErrorCode(docResult.error)));
 	}
 	if (!personsResult.response.ok) {
 		throw error(personsResult.response.status, getErrorMessage('INTERNAL_ERROR'));
@@ -76,8 +75,9 @@ export const actions = {
 		// Fetch current document to preserve all existing fields
 		const docResult = await api.GET('/api/documents/{id}', { params: { path: { id: params.id } } });
 		if (!docResult.response.ok) {
-			const code = (docResult.error as unknown as { code?: string })?.code;
-			return fail(docResult.response.status, { error: getErrorMessage(code) });
+			return fail(docResult.response.status, {
+				error: getErrorMessage(extractErrorCode(docResult.error))
+			});
 		}
 
 		const doc = docResult.data!;

frontend/src/routes/documents/[id]/page.server.spec.ts

@@ -1,6 +1,9 @@
 import { describe, expect, it, vi, beforeEach } from 'vitest';
 
-vi.mock('$lib/shared/api.server', () => ({ createApiClient: vi.fn() }));
+vi.mock('$lib/shared/api.server', () => ({
+	createApiClient: vi.fn(),
+	extractErrorCode: (e: unknown) => (e as { code?: string } | undefined)?.code
+}));
 vi.mock('$env/dynamic/private', () => ({ env: { API_INTERNAL_URL: 'http://test-backend:8080' } }));
 
 import { load } from './+page.server';

frontend/src/routes/documents/page.server.spec.ts

@@ -1,6 +1,9 @@
 import { describe, expect, it, vi, beforeEach } from 'vitest';
 
-vi.mock('$lib/shared/api.server', () => ({ createApiClient: vi.fn() }));
+vi.mock('$lib/shared/api.server', () => ({
+	createApiClient: vi.fn(),
+	extractErrorCode: (e: unknown) => (e as { code?: string } | undefined)?.code
+}));
 
 import { load } from './+page.server';
 import { createApiClient } from '$lib/shared/api.server';

frontend/src/routes/enrich/[id]/+page.server.ts

@@ -1,6 +1,6 @@
 import { error, redirect } from '@sveltejs/kit';
 import { env } from '$env/dynamic/private';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage, parseBackendError } from '$lib/shared/errors';
 
 export async function load({
@@ -31,8 +31,7 @@ export async function load({
 	]);
 
 	if (!docResult.response.ok) {
-		const code = (docResult.error as unknown as { code?: string })?.code;
-		throw error(docResult.response.status, getErrorMessage(code));
+		throw error(docResult.response.status, getErrorMessage(extractErrorCode(docResult.error)));
 	}
 
 	const incompleteCount = countResult.response.ok ? (countResult.data?.count ?? 0) : 0;

frontend/src/routes/geschichten/+page.server.ts

@@ -1,5 +1,5 @@
 import { error } from '@sveltejs/kit';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 import type { components } from '$lib/generated/api';
 import type { PageServerLoad } from './$types';
@@ -25,8 +25,7 @@ export const load: PageServerLoad = async ({ url, fetch }) => {
 	]);
 
 	if (!listResult.response.ok) {
-		const code = (listResult.error as unknown as { code?: string })?.code;
-		throw error(listResult.response.status, getErrorMessage(code));
+		throw error(listResult.response.status, getErrorMessage(extractErrorCode(listResult.error)));
 	}
 
 	const personFilters = personResults

frontend/src/routes/geschichten/[id]/+page.server.ts

@@ -1,5 +1,5 @@
 import { error } from '@sveltejs/kit';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 import type { PageServerLoad } from './$types';
 
@@ -9,8 +9,7 @@ export const load: PageServerLoad = async ({ params, fetch }) => {
 		params: { path: { id: params.id } }
 	});
 	if (!result.response.ok) {
-		const code = (result.error as unknown as { code?: string })?.code;
-		throw error(result.response.status, getErrorMessage(code));
+		throw error(result.response.status, getErrorMessage(extractErrorCode(result.error)));
 	}
 	return { geschichte: result.data! };
 };

frontend/src/routes/geschichten/[id]/edit/+page.server.ts

@@ -1,5 +1,5 @@
 import { error, redirect } from '@sveltejs/kit';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 import type { PageServerLoad } from './$types';
 
@@ -13,8 +13,7 @@ export const load: PageServerLoad = async ({ params, fetch, parent }) => {
 		params: { path: { id: params.id } }
 	});
 	if (!result.response.ok) {
-		const code = (result.error as unknown as { code?: string })?.code;
-		throw error(result.response.status, getErrorMessage(code));
+		throw error(result.response.status, getErrorMessage(extractErrorCode(result.error)));
 	}
 	return { geschichte: result.data! };
 };

frontend/src/routes/page.server.spec.ts

@@ -1,6 +1,9 @@
 import { describe, expect, it, vi, beforeEach } from 'vitest';
 
-vi.mock('$lib/shared/api.server', () => ({ createApiClient: vi.fn() }));
+vi.mock('$lib/shared/api.server', () => ({
+	createApiClient: vi.fn(),
+	extractErrorCode: (e: unknown) => (e as { code?: string } | undefined)?.code
+}));
 
 import { load } from './+page.server';
 import { createApiClient } from '$lib/shared/api.server';

frontend/src/routes/persons/[id]/+page.server.ts

@@ -1,5 +1,5 @@
 import { error } from '@sveltejs/kit';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 
 export async function load({ params, fetch, locals }) {
@@ -32,8 +32,10 @@ export async function load({ params, fetch, locals }) {
 	]);
 
 	if (!personResult.response.ok) {
-		const code = (personResult.error as unknown as { code?: string })?.code;
-		throw error(personResult.response.status, getErrorMessage(code));
+		throw error(
+			personResult.response.status,
+			getErrorMessage(extractErrorCode(personResult.error))
+		);
 	}
 
 	return {

frontend/src/routes/persons/[id]/edit/+page.server.ts

@@ -1,5 +1,5 @@
 import { error, fail, redirect } from '@sveltejs/kit';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 import {
 	normalizePersonType,
@@ -25,8 +25,7 @@ export async function load({ params, fetch, locals }) {
 	]);
 
 	if (!result.response.ok) {
-		const code = (result.error as unknown as { code?: string })?.code;
-		throw error(result.response.status, getErrorMessage(code));
+		throw error(result.response.status, getErrorMessage(extractErrorCode(result.error)));
 	}
 
 	const person = result.data!;
@@ -74,8 +73,9 @@ export const actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { updateError: getErrorMessage(code) });
+			return fail(result.response.status, {
+				updateError: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 
 		throw redirect(303, `/persons/${params.id}`);
@@ -100,8 +100,9 @@ export const actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { mergeError: getErrorMessage(code) });
+			return fail(result.response.status, {
+				mergeError: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 
 		throw redirect(303, `/persons/${targetPersonId}`);
@@ -127,8 +128,9 @@ export const actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { aliasError: getErrorMessage(code) });
+			return fail(result.response.status, {
+				aliasError: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 
 		return { aliasSuccess: true };
@@ -148,8 +150,9 @@ export const actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { aliasError: getErrorMessage(code) });
+			return fail(result.response.status, {
+				aliasError: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 
 		return { aliasSuccess: true };
@@ -166,8 +169,9 @@ export const actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { relationshipError: getErrorMessage(code) });
+			return fail(result.response.status, {
+				relationshipError: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 		return { relationshipSuccess: true };
 	},
@@ -211,8 +215,9 @@ export const actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { relationshipError: getErrorMessage(code) });
+			return fail(result.response.status, {
+				relationshipError: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 		return { relationshipSuccess: true };
 	},
@@ -230,8 +235,9 @@ export const actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { relationshipError: getErrorMessage(code) });
+			return fail(result.response.status, {
+				relationshipError: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 		return { relationshipSuccess: true };
 	}

frontend/src/routes/persons/[id]/page.server.spec.ts

@@ -1,7 +1,10 @@
 import { describe, expect, it, vi, beforeEach } from 'vitest';
 import { load } from './+page.server';
 
-vi.mock('$lib/shared/api.server', () => ({ createApiClient: vi.fn() }));
+vi.mock('$lib/shared/api.server', () => ({
+	createApiClient: vi.fn(),
+	extractErrorCode: (e: unknown) => (e as { code?: string } | undefined)?.code
+}));
 
 import { createApiClient } from '$lib/shared/api.server';
 

frontend/src/routes/persons/new/+page.server.ts

@@ -1,5 +1,5 @@
 import { error, fail, redirect } from '@sveltejs/kit';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 import {
 	normalizePersonType,
@@ -57,9 +57,8 @@ export const actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
 			return fail(result.response.status, {
-				error: getErrorMessage(code),
+				error: getErrorMessage(extractErrorCode(result.error)),
 				personType,
 				title,
 				firstName,

frontend/src/routes/profile/+page.server.ts

@@ -1,7 +1,7 @@
 import { fail } from '@sveltejs/kit';
 import { env } from '$env/dynamic/private';
 import type { PageServerLoad, Actions } from './$types';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 
 const apiBase = () => env.API_INTERNAL_URL || 'http://localhost:8080';
@@ -27,8 +27,9 @@ export const actions: Actions = {
 		const result = await api.PUT('/api/users/me', { body });
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { updateError: getErrorMessage(code) });
+			return fail(result.response.status, {
+				updateError: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 
 		return { updateSuccess: true };
@@ -50,8 +51,9 @@ export const actions: Actions = {
 		});
 
 		if (!result.response.ok) {
-			const code = (result.error as unknown as { code?: string })?.code;
-			return fail(result.response.status, { passwordError: getErrorMessage(code) });
+			return fail(result.response.status, {
+				passwordError: getErrorMessage(extractErrorCode(result.error))
+			});
 		}
 
 		return { passwordSuccess: true };

frontend/src/routes/stammbaum/+page.server.ts

@@ -1,5 +1,5 @@
 import { error, redirect } from '@sveltejs/kit';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 
 export async function load({ fetch }) {
@@ -9,8 +9,7 @@ export async function load({ fetch }) {
 	if (result.response.status === 401) throw redirect(302, '/login');
 
 	if (!result.response.ok) {
-		const code = (result.error as unknown as { code?: string })?.code;
-		throw error(result.response.status, getErrorMessage(code));
+		throw error(result.response.status, getErrorMessage(extractErrorCode(result.error)));
 	}
 
 	const network = result.data!;

frontend/src/routes/users/[id]/+page.server.ts

@@ -1,6 +1,6 @@
 import { error } from '@sveltejs/kit';
 import type { PageServerLoad } from './$types';
-import { createApiClient } from '$lib/shared/api.server';
+import { createApiClient, extractErrorCode } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 
 export const load: PageServerLoad = async ({ params, fetch }) => {
@@ -8,8 +8,7 @@ export const load: PageServerLoad = async ({ params, fetch }) => {
 	const result = await api.GET('/api/users/{id}', { params: { path: { id: params.id } } });
 
 	if (!result.response.ok) {
-		const code = (result.error as unknown as { code?: string })?.code;
-		throw error(result.response.status, getErrorMessage(code));
+		throw error(result.response.status, getErrorMessage(extractErrorCode(result.error)));
 	}
 
 	return { profileUser: result.data! };