There's another community post with 404 debugging tips that might be helpful. Please give these solutions a try and let us know how it goes.

https://community.vercel.com/t/debugging-404-errors/437

vercel.com

How to debug 404 errors | Vercel Knowledge Base

Learn the systematic steps to identify and resolve 404 issues.

A human should be around soon to offer more advice. But you can also get helpful information quickly by asking v0.

Update — 2026-08-24

Additional testing confirms that this is not an application-level 404.

• Production alias: https://memory-sentinel.vercel.app/ → HTTP 404 → x-vercel-error: NOT_FOUND → server: Vercel

• Production API route: https://memory-sentinel.vercel.app/api/health/supabase → HTTP 404 → x-vercel-error: NOT_FOUND

• No runtime invocation is recorded for requests to the production alias.

• Unique deployment URL: → Vercel Authentication 302 → The deployment itself is reachable.

• Deployment status: → READY → target: production → aliasError: null

• memory-sentinel.vercel.app is listed in the deployment aliases.

• Vercel Domains page: → Valid Configuration

The important distinction is:

Production alias → platform-level NOT_FOUND Unique deployment URL → Authentication 302

Both the homepage and the API route fail before reaching the Next.js runtime.

This appears consistent with a production alias / edge-routing inconsistency rather than an application routing or build-output issue.

Could a Vercel engineer please check the edge routing/provisioning state for memory-sentinel.vercel.app and, if necessary, resync or reprovision the production alias?

I have intentionally not made further application or deployment changes so that the current state can be investigated without additional variables.

Thank you.

Update — 2026-08-24

I performed an additional comparison using the same READY production deployment.

The issue appears to affect only the custom/vanity production alias:

• https://memory-sentinel.vercel.app/ → HTTP 404 → x-vercel-error: NOT_FOUND

• https://memory-sentinel.vercel.app/api/health/supabase → HTTP 404 → x-vercel-error: NOT_FOUND

However, other aliases associated with the same project/deployment route correctly:

• https://memory-sentinel-freemck-7205s-projects.vercel.app/ → HTTP 302 to Vercel Authentication

• https://memory-sentinel-git-main-freemck-7205s-projects.vercel.app/ → HTTP 302 to Vercel Authentication

The 302 responses indicate that these aliases reach Vercel's deployment/authentication layer successfully.

Therefore, the current evidence suggests that:

• The deployment itself is healthy and READY.
• The project routing/build output is valid.
• The runtime is not the cause of the failing request.
• Other production/branch aliases on the same project work.
• Only memory-sentinel.vercel.app returns the platform-level NOT_FOUND.

This appears to isolate the problem to the routing/provisioning of the specific memory-sentinel.vercel.app alias rather than the deployment itself.

Could you please check whether this specific .vercel.app alias needs to be resynchronized or reprovisioned in Vercel's edge routing layer?

I have not changed the project, deployment, or alias configuration while investigating this issue.

Thank you.

The NOT_FOUND code usually means that the page doesn't exist at the provided address. If the entire deployment was not found, the code would be DEPLOYMENT_NOT_FOUND instead.

The 404 debugging tips linked above have a few suggestions. But the first thing I'd like to know is the deployment output for your project since that will tell us more about what paths actually exist.

You can check it in the dashboard if you open the deployment details, go to Source and then Output

You can see in the screenshot that my example has an index (that's the default page shown at the root / path) as well as about, contact, and a blog directory that could contain additional pages. What does the output look like for your project?

Thanks, Amy.

I checked the deployment's Source → Output as requested.

The Output view shows only these five files:

• file.svg
• globe.svg
• next.svg
• vercel.svg
• window.svg

I opened each of them, and they are static SVG assets only.

I do not see an obvious / route, _not-found, or /api/health/supabase route in the Output view.

The deployment is:

dpl_LeZJy6SZaidLR773tWu1hnrqAJf7

Could you please confirm whether this Output indicates that the application routes were not included in the deployment, and what I should check next?

The production alias still returns:

HTTP 404 x-vercel-error: NOT_FOUND

while the unique deployment URL returns Vercel Authentication 302.

Thanks for sharing that. The output shows us which paths exist. I went directly to https://memory-sentinel.vercel.app/file.svg and got a file graphic, so we know the deployment is live.

Now you'll need to look into your code and project configuration to identify why the build doesn't generate the index and other pages you expected. The 404 debugging guide linked in the first reply has some tips to help you figure it out.

I hope that helps!

Hi Freemck,

That Output view is a useful clue. If the deployment output only contains the default SVG assets, then Vercel likely did not deploy the actual Next.js app routes for that deployment. In that case the NOT_FOUND is less likely to be an edge alias problem and more likely a build/project configuration issue.

I’d check these in this order:

1. In the same deployment, open Source and confirm whether Vercel is seeing your package.json, next.config.*, and app/ or pages/ directory.
2. In Project Settings → Build and Deployment, confirm the Framework Preset is Next.js.
3. Check the Root Directory. If your Next app is inside a subfolder, set Root Directory to that folder. If it is at the repo root, Root Directory should usually be empty.
4. Check whether Output Directory is overridden. For a normal Next.js app, I would remove a custom Output Directory override and let Vercel detect it automatically.
5. Redeploy after changing those settings, then check Source → Output again. A healthy Next.js deployment should show more than just the static SVG files.

Vercel’s build settings doc covers the Root Directory and Output Directory behavior here: https://vercel.com/docs/builds/configure-a-build

If the next deployment output still only contains SVGs, can you share the deployment’s detected framework, Root Directory, Build Command, and Output Directory settings?