Nginx config for single page app with HTML5 App Ca

I'm trying to build a single page app that utilizes HTML5 App Cache, which will cache a whole new version of the app for every distinct URL, thus I must redirect everyone to / and have my app route them afterward (this is the solution used on devdocs.io).

Here's my nginx config. I want all requests to send a file if it exists, redirect to my API at /auth and /api, and redirect all other requests to index.html. Why is the following configuration causing my browser to say that there is a redirect loop? If the user hits location block #2 and his route doesn't match a static file, he's sent to location block #3, which will redirect him to "/" which should hit location block #1 and serve index.html, correct? What is causing the redirect loop here? Is there a better way to accomplish this?

root /files/whatever/public;
index index.html;

# If the location is exactly "/", send index.html.
location = / {
    try_files $uri /index.html;
}

location / {
    try_files $uri @redirectToIndex;
}

# Set the cookie of the initialPath and redirect to "/".
location @redirectToIndex {
    add_header Set-Cookie "initialPath=$request_uri; path=/";
    return 302 $scheme://$host/;
}

# Proxy requests to "/auth" and "/api" to the server.
location ~* (^\/auth)|(^\/api) {
    proxy_pass http://application_upstream;
    proxy_redirect off;
}

That loop message suggests that /files/whatever/public/index.html doesn't exist, so the try_files in location / doesn't find $uri when it's equal to /index.html, so the try_files always internally redirects those requests to the @ location which does the external redirect.

Unless you have a more complicated setup than you've outlined, I don't think you need to do so much. You shouldn't need external redirects (or even internal redirects) or server-side cookie sending for a one-file js app. The regex match for app and api wasn't quite right, either.

root /files/whatever/public;
index index.html;

location / {
    try_files $uri /index.html =404;
}

# Proxy requests to "/auth" and "/api" to the server.
location ~ ^/(auth|api) {
    proxy_pass http://application_upstream;
    proxy_redirect off;
}