templates: skip standalone output on Vercel

[devin-ai-integration]

What

Vercel deploys of the openui-cloud template fail because Next 16.3 + Vercel's build adapter skips emitting next-server.js.nft.json when output: "standalone" is set. Vercel ignores standalone output anyway, so the config is only useful for Docker / self-hosting.

Cherry-picked from the openui deploy PR (#1093) so the template fix can land independently of the CLI deploy command.

Changes

• templates/openui-cloud/next.config.ts and templates/openui-cloud/overlays/vercel-eve/next.config.ts: ...(process.env.VERCEL ? {} : { output: "standalone" as const }) — standalone stays on everywhere except Vercel builds.

Test Plan

• Verified locally: diff is byte-identical to the next.config.ts changes on feat/cli-vercel-deploy-split (commit 132cb61), which was validated against a real Vercel deploy in that PR's QA; prettier --check passes.

Checklist

• I linked a related issue, if applicable (cli: add openui deploy for Vercel #1093)
• I updated docs/README when needed (no doc references standalone output)
• I considered backwards compatibility (non-Vercel builds keep output: "standalone")

Link to Devin session: https://app.devin.ai/sessions/435c06221d5647e1ba5fc348879a7b89
Open in Devin Desktop: https://app.devin.ai/desktop/session/435c06221d5647e1ba5fc348879a7b89?variant=devin

[devin-ai-integration]

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Project	Deployment	Actions	Updated
openui-docs	Ready	Preview	Sep 10, 2026 5:51am UTC