diff --git a/src/app/api/auth/register-anon/route.js b/src/app/api/auth/register-anon/route.js
index 74068c18..97d1cc0c 100644
--- a/src/app/api/auth/register-anon/route.js
+++ b/src/app/api/auth/register-anon/route.js
@@ -15,6 +15,19 @@ import { verifyInviteToken, InviteVerificationError } from '@/lib/invites/verify
 /** Postgres unique-violation error code. */
 const PG_UNIQUE_VIOLATION = '23505';
 
+/**
+ * @param {string | null} authHeader
+ * @returns {string | null}
+ */
+function getBearerToken(authHeader) {
+	if (typeof authHeader !== 'string') return null;
+
+	const match = authHeader.match(/^Bearer\s+(.+)$/i);
+	const token = match?.[1]?.trim();
+
+	return token || null;
+}
+
 /**
  * Build a service-role Supabase client (bypasses RLS).
  * Mirrors the pattern used by the phone/SMS verify-sms route.
@@ -62,10 +75,10 @@ export async function POST(request) {
 
 		// --- Validate anonymous Bearer session ---
 		const authHeader = request.headers.get('authorization');
-		if (!authHeader) {
+		const token = getBearerToken(authHeader);
+		if (!token) {
 			return NextResponse.json({ error: 'Missing authorization header' }, { status: 401 });
 		}
-		const token = authHeader.replace('Bearer ', '');
 
 		const supabase = await createSupabaseServerClient();
 		const { data: { user: authUser }, error: userError } = await supabase.auth.getUser(token);
diff --git a/src/app/api/auth/register-anon/route.test.js b/src/app/api/auth/register-anon/route.test.js
new file mode 100644
index 00000000..d4bed114
--- /dev/null
+++ b/src/app/api/auth/register-anon/route.test.js
@@ -0,0 +1,73 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+
+const mocks = vi.hoisted(() => ({
+	serverAuthGetUser: vi.fn(),
+	createSupabaseServerClient: vi.fn(() => ({
+		auth: {
+			getUser: mocks.serverAuthGetUser
+		}
+	})),
+	createClient: vi.fn(() => ({})),
+	verifyInviteToken: vi.fn(),
+}));
+
+vi.mock('@/lib/supabase.js', () => ({
+	createSupabaseServerClient: mocks.createSupabaseServerClient
+}));
+
+vi.mock('@supabase/supabase-js', () => ({
+	createClient: mocks.createClient
+}));
+
+vi.mock('@/lib/invites/verify.js', () => ({
+	verifyInviteToken: mocks.verifyInviteToken,
+	InviteVerificationError: class InviteVerificationError extends Error {}
+}));
+
+function registerRequest(authorization) {
+	return new Request('https://example.com/api/auth/register-anon', {
+		method: 'POST',
+		headers: authorization ? { authorization } : {},
+		body: JSON.stringify({
+			inviteToken: 'qci1.payload.signature',
+			username: 'anon-user',
+			publicKey: 'ml-kem-public-key'
+		})
+	});
+}
+
+describe('register-anon bearer authentication', () => {
+	beforeEach(() => {
+		vi.resetModules();
+		vi.clearAllMocks();
+		mocks.serverAuthGetUser.mockResolvedValue({
+			data: { user: null },
+			error: { message: 'invalid session' }
+		});
+	});
+
+	it('normalizes bearer scheme casing and extra spaces before validating the session', async () => {
+		const { POST } = await import('./route.js');
+
+		const response = await POST(registerRequest('bearer   access-token-123  '));
+		const body = await response.json();
+
+		expect(response.status).toBe(401);
+		expect(body.error).toBe('Invalid or expired session');
+		expect(mocks.serverAuthGetUser).toHaveBeenCalledWith('access-token-123');
+		expect(mocks.verifyInviteToken).not.toHaveBeenCalled();
+	});
+
+	it('does not validate an empty bearer header', async () => {
+		const { POST } = await import('./route.js');
+
+		const response = await POST(registerRequest('Bearer   '));
+		const body = await response.json();
+
+		expect(response.status).toBe(401);
+		expect(body.error).toBe('Missing authorization header');
+		expect(mocks.createSupabaseServerClient).not.toHaveBeenCalled();
+		expect(mocks.serverAuthGetUser).not.toHaveBeenCalled();
+		expect(mocks.verifyInviteToken).not.toHaveBeenCalled();
+	});
+});