openRouter.callModel does not work in Nextjs Production app router

[ryankashi]

	const result = openRouter.callModel({
		model: 'openai/gpt-5.2',
		instructions: 'model instructions!',
		input: 'hi!',
		parallelToolCalls: false,
		tools: [tool1, tool2, tool3...]
	});

Will create the function

	 try {
	 	const textStream = result.getTextStream();
	 	for await (const item of textStream) {
	 		console.log('item:', item);
	 	}
	 } catch (error) {
	 	console.log('got error:', error);
	 }

Causes an error, Unexpected response type from API

To recreate, just create a route.ts on Nextjs 15/16+ , run npm run build -> npm run start.

In production, the function will fail

[ymaxli]

It's this check here checking event stream using class name which may get minified in your production build.

We're seeing the same issue in our project. The workaround is to turn off the class name minification for our build.