I’m in over my head and looking for help.
I previously had a CRA + React SPA app with some redirects. A little quirky to get the redirect logic working and I needed to use proxy middleware for some cors issues, but it worked.
But CRA is old and unsupported these days and I can’t upgrade a bunch of dependencies so I migrated to Vite.
Unfortunately I’m hitting some major issues.
It kind of feels like I can get localhost working (yarn dev or vercel dev but not both), or I can get prod running but not local.
Everything works in production using vercel.json rewrites, but in local dev (vercel dev), I’m running into major issues:
• My catch-all rewrite (/(.*) → /) is needed in prod for SPA routing, but it breaks Vite’s historyApiFallback in local dev — causing errors like Manifest: SyntaxError.
• API routes like /api/c sometimes get served as static JS files, not executed, depending on the dev config.
• I’m getting conflicts between Vite’s dev server and Vercel’s dev server over who handles routing.
• Using a proxy in Vite for /api introduces other bugs when run with vercel dev.
I want:
• SPA routing to work cleanly in both dev and prod
• Serverless API routes to work locally without static conflicts
After spending over a day trying to figure it out and fix it I hit a wall. I turned to ChatGPT and used a ton of tokens in Cursor but that just ran in curcles and hit all the same issues.
If it helps, this is what ChatGPT has to say about it.
Why it breaks in Vite:
Vite uses native ES modules + Rollup + its own dev server (powered by connect), which handles routing differently:
- Vite also supports historyApiFallback, but…
- When you run vercel dev, Vite is no longer the top-level server — Vercel is.
- So Vercel’s vercel.json routing logic is applied before Vite even sees the request.
The problem:
In local dev with vercel dev:
- That catch-all rule in vercel.json (/(.*) → /) short-circuits routing before Vite can serve index.html.
- Vite doesn’t get a chance to run its historyApiFallback, so you get weird errors like:
“Manifest: SyntaxError: Unexpected token <”
Which usually means: you expected a .js file, but got HTML (like index.html) instead.
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I’m not good with all this build system stuff and redirects and honestly kind of lost. Any help would be appreciated 