Avoid check for x-vercel-ai-data-stream

[tom-bywild]

AI SDK is a great package and offers tremendous value! In a business environment, it might not be possible to use custom response headers even from custom endpoints.

This is an issue in case you create a Data Stream endpoint from scratch, where setting x-vercel-ai-data-stream as a response-header is filtered out by the infrastructure (e.g. certain proxies). Getting approval to put the header on an allow-list might not be possible in large enterprises due to security/other concerns or requirements.

Therefore I wanted to ask if there's a hidden option to not have x-vercel-ai-data-stream be present in the response, and still let useChat handle the response accordingly.

[felixtosh]

+1 Implementing right now at a large client - their infra is blocking us with this and I won't get a change approved until 2026. Would be a life safer to have this