Mithril m.route pushState and static hosting: missing SPA fallback on direct deep-link requests?

Answer

The SPA fails to load on a direct request because the static host returns a 404 for URLs that do not map to a file, and Mithril’s pushState routing expects the HTML page to be served.

Confirmed facts

• Mithril’s default m.route uses the HTML5 History API (pushState) in versions 1.x and 2.x.
• The m.route.mode function toggles between pushState and hash modes; it is client‑side only and does not affect server configuration.
• Without a server rewrite that serves index.html for unknown paths, the browser receives a 404 and the SPA never mounts.

Recommended steps

1. Check the installed Mithril version:

   m.version

   and confirm that m.route.mode exists.
2. Inspect the hosting configuration (Apache .htaccess, Nginx location block, or CDN page rule) for a rule that returns index.html when the requested path does not correspond to a static file.
3. If such a rule is missing, add it:

   # Apache example
   RewriteEngine On
   RewriteCond %{REQUEST_FILENAME} !-f
   RewriteRule ^.*$ /index.html [L]

4. Test a fresh browser session: open an incognito window, navigate directly to a client route such as /users/42, and verify that the network request for index.html is made and that Mithril mounts the route without a full reload.

Alternative – hash routing

Switching to hash‑based routing with m.route.mode('hash') eliminates the need for a rewrite because the fragment after # is not sent to the server. This removes the server‑side dependency but breaks canonical URLs, SEO‑friendly paths, and log visibility.

When to choose hash routing

• The hosting environment cannot be modified (e.g., restrictive CDN that forbids rewrite rules).
• Acceptable trade‑offs include loss of clean URLs and potential duplicate‑content issues.

Next diagnostic

Confirm whether the production host already has a rewrite rule that serves index.html for non‑file requests; if not, the rewrite is the minimal change required.