diff --git a/src/utils/corsConfig.ts b/src/utils/corsConfig.ts
index a646aeb4..ca1d3a68 100644
--- a/src/utils/corsConfig.ts
+++ b/src/utils/corsConfig.ts
@@ -3,7 +3,7 @@
  *
  * Selects the appropriate CORS middleware options based on environment:
  * - When CORS_ORIGIN is set: allow only those origins (comma-separated)
- * - When unset in production: warn and allow no origins (restrictive default)
+ * - When unset in production: throws an error at startup (hard failure)
  * - When unset outside production: default to localhost:5173 (dev convenience)
  */
 
@@ -28,15 +28,14 @@ export interface CorsConfig {
  * Returns a ready-to-use Hono `cors()` middleware configured for the current
  * environment:
  *  - If `corsOriginEnv` is set (comma-separated), only those origins are allowed.
- *  - If `corsOriginEnv` is unset in production, a warning is logged and an empty
- *    origin list is used (blocks all cross-origin requests).
+ *  - If `corsOriginEnv` is unset in production, throws an `Error` to crash the
+ *    process at startup with a clear, actionable message.
  *  - If `corsOriginEnv` is unset outside production, `http://localhost:5173` is
  *    used as a dev-friendly default.
  */
 export function buildCorsMiddleware({
 	corsOriginEnv,
 	isProduction,
-	warn = console.warn,
 }: CorsConfigOptions): ReturnType<typeof cors> {
 	const origins = corsOriginEnv
 		?.split(',')
@@ -48,12 +47,11 @@ export function buildCorsMiddleware({
 	}
 
 	if (isProduction) {
-		warn(
-			'[Dashboard] WARNING: CORS_ORIGIN is not set in production. ' +
-				'Using restrictive default (no origins allowed). ' +
+		throw new Error(
+			'[Dashboard] CORS_ORIGIN is not set. ' +
+				'This is required in production. ' +
 				'Set CORS_ORIGIN to your frontend URL (e.g., https://dashboard.example.com).',
 		);
-		return cors({ origin: [], credentials: true });
 	}
 
 	// Development default
diff --git a/tests/unit/utils/corsConfig.test.ts b/tests/unit/utils/corsConfig.test.ts
index 8147d400..54d25dec 100644
--- a/tests/unit/utils/corsConfig.test.ts
+++ b/tests/unit/utils/corsConfig.test.ts
@@ -77,40 +77,22 @@ describe('buildCorsMiddleware', () => {
 	});
 
 	describe('when CORS_ORIGIN is not set AND NODE_ENV=production', () => {
-		it('logs a warning at startup', () => {
-			const warn = vi.fn();
-			buildCorsMiddleware({
-				corsOriginEnv: undefined,
-				isProduction: true,
-				warn,
-			});
-
-			expect(warn).toHaveBeenCalledOnce();
-			expect(warn).toHaveBeenCalledWith(
-				expect.stringContaining('CORS_ORIGIN is not set in production'),
-			);
-		});
-
-		it('blocks all cross-origin requests (empty origin list)', async () => {
-			const middleware = buildCorsMiddleware({
-				corsOriginEnv: undefined,
-				isProduction: true,
-				warn: vi.fn(),
-			});
-
-			const res = await fetchWithOrigin(middleware, 'https://any-origin.example.com');
-			expect(res.headers.get('Access-Control-Allow-Origin')).toBeNull();
+		it('throws an error at startup', () => {
+			expect(() =>
+				buildCorsMiddleware({
+					corsOriginEnv: undefined,
+					isProduction: true,
+				}),
+			).toThrowError(/CORS_ORIGIN is not set/);
 		});
 
-		it('also blocks localhost when in production without CORS_ORIGIN', async () => {
-			const middleware = buildCorsMiddleware({
-				corsOriginEnv: undefined,
-				isProduction: true,
-				warn: vi.fn(),
-			});
-
-			const res = await fetchWithOrigin(middleware, 'http://localhost:5173');
-			expect(res.headers.get('Access-Control-Allow-Origin')).toBeNull();
+		it('throws an error with an actionable message', () => {
+			expect(() =>
+				buildCorsMiddleware({
+					corsOriginEnv: undefined,
+					isProduction: true,
+				}),
+			).toThrowError(/Set CORS_ORIGIN to your frontend URL/);
 		});
 	});