Returning NextResponse with modified responses and modified NextRequest - next.js

Question

As per the changelists, it's now possible to modify requests in middleware via:
const headers = new Headers(request.headers);
// Add a new request header
headers.set('x-hello-from-middleware', 'foo');
// Delete a request header from the client
headers.delete('x-from-client');
const resp = NextResponse.next({
// New option `request.headers` which accepts a Headers object
// overrides request headers with the specified new ones.
request: {
headers
}
});
This works fine.
It's also possible to add to to the response, such as adding cookies, via:
let response = NextResponse.next();
response.cookies.set({
name: 'access_token',
value: newAccessToken,
expires: expiresString,
path: '/',
});
return response
This also works fine.
Question
I'm having trouble understanding the technique to combine both.
If I modify the request, for returning. Ideally, I would create the headers object, as in the first example, and then add it to the response object in the second example, before returning response. Seems straightforward. Response is an object.
But I specify:
response.request = headers
or
attempt to make an object or response parameters and and add them alongside header parameters like:
const resp = NextResponse.next({
response: responseParams
request: {
headers
}
});
Neither work. I'm missing something obvious I can't find in the documentation. Any idea?

Answer 1

I didn't find a way to directly set response.request headers after declaring response (perhaps it's not possible) but I did overlook I could change the order I was doing things in and missed the obvious that I could also declare a new NextResponse with request variables as its own variable to add cookies to.
e.g.
let response = NextResponse.next({
request: {
headers: requestHeaders,
}
});
response.cookies.set({
name: 'access_token',
value: newAccessToken,
expires: expiresString,
path: '/',
});
return response
This solved the problem.