Deployments fail at "Deploying outputs..." with no error after Hobby unblock

Every deployment on my Hobby project fails at the "Deploying outputs" stage. The build itself always succeeds, and there is no error message anywhere in the build log. This started immediately after my team was unblocked from a fair-use pause today.

What the log shows

The last two lines of every failed deployment:

Build Completed in /vercel/output [19-26s]
Deploying outputs...

Nothing after that — the deployment flips to ERROR. I pulled all 68 log lines via /api/v2/deployments/{id}/events and not a single line contains "error". The dashboard shows only "An unexpected error occurred when running this build."

Why I am confident it is not my code

I redeployed dpl_22Bq14HS2wBvtM5KUf2nyVjQYMvz — the exact build that was serving production at that moment. It failed identically. The same source that was live could not be redeployed.

A preview-target deployment of that same source also fails at the same line.

What I have ruled out

Account block — /api/v2/teams/{id} returns blocked: null, softBlock: null; the project has disabledAt: null
Build failure — compile, page data collection, static generation (18/18) and the route table all complete in under 30s
Production-specific — preview target fails identically
Code / dependencies — see above

Details

Team: hugh-lkgs-projects (Hobby)
Project: lolinyuk (Next.js 16.2.10)
Failed: dpl_AZhf84Z16XfVK7BxrAQcYoGb7N3J, dpl_HL21Kayiah8WtiQRp8RLsJiX94HN, dpl_996nfVt2eabQ73vjTUmEW8ZjDrWP
Last successful: dpl_22Bq14HS2wBvtM5KUf2nyVjQYMvz (Jul 20)

Current state

I have paused the project so it stops consuming resources on the stale build. I have optimizations committed that I wrote specifically to bring this project back inside Hobby limits, and I cannot ship them.

The agent at /help could not help and told me to open a support case, but on Hobby every Problem Area in the case form (I tried CI/CD → Builds and Accounts → Account Settings) replaces the submit button with "Visit our Community". So I am here.

Has anyone seen deployments fail at "Deploying outputs" with an empty error like this, particularly right after an account unblock?

Solved. Posting the cause in case it saves someone else the afternoon it cost me.

Cause

Hobby allows exactly one function region, and my project had two.

Settings → Functions → Function Region had both iad1 (North America) and icn1 (Asia Pacific) enabled. That configuration was set while the project was on Pro, where multiple regions are allowed. After the plan went back to Hobby, every deployment was rejected — including redeploys of the build that was still serving production, which is what made it look like a platform fault rather than a config one.

How to see it

The build log is useless here: it completes normally and ends at Deploying outputs... with no error line. The dashboard only says "An unexpected error occurred". The real reason is only in the deployment record, which you can read from the browser console while signed in to vercel.com:

await (await fetch('/api/v13/deployments/<dpl_id>?teamId=<team_id>')).json()

That returned:

errorCode: "upgrade_required"
errorLink: "https://vercel.link/multiple-function-regions"
errorStep: "patchBuild"
regions:   ["iad1", "icn1"]

regions having two entries is the whole story.

Fix

Settings → Functions → Function Region, deselect until exactly one region remains, Save, then redeploy. I kept icn1 because my database is in Seoul. Deployment went through immediately — regions: ["icn1"], no error.

Suggestion to Vercel

This failure has no surface signal at all. Two things would have saved hours here: surfacing errorCode / errorLink in the deployment UI instead of the generic message, and warning on the plan-downgrade path when the project's region count exceeds what the new plan allows. There are a lot of "fails at Deploying outputs with no error" threads in this category — I would not be surprised if some are this.