templates(openui-cloud): send openui-template/nextjs User-Agent on server fetches

[devin-ai-integration]

What

Apps scaffolded from the openui-cloud template now send User-Agent: openui-template/nextjs on outbound server-side requests, so template traffic is identifiable.

Changes

• Add src/instrumentation.ts (the Next.js startup hook: register() runs once before any route is served). It wraps globalThis.fetch and sets the User-Agent header, merging existing Request/init headers first:

globalThis.fetch = (input, init) => {
  const headers = new Headers(input instanceof Request ? input.headers : undefined);
  new Headers(init?.headers).forEach((v, k) => headers.set(k, v));
  headers.set("User-Agent", "openui-template/nextjs");
  return baseFetch(input, { ...init, headers });
};

Because it patches global fetch, it covers the raw fetch in /api/frontend-token and the SDK clients (openai, @ai-sdk/openai, @langchain/openai) used by the default route and overlays, overriding their default UA (e.g. OpenAI/JS x.y). No overlay ships its own instrumentation.ts, so this applies to all of them.

Test Plan

• Verified locally: scaffolded a copy of the template, ran next dev, pointed /api/frontend-token and /api/chat at a local echo server, and confirmed both the plain fetch and the openai SDK requests arrived with User-Agent: openui-template/nextjs.
• tsc --noEmit, eslint, and prettier --check pass.

Checklist

• I linked a related issue, if applicable
• I updated docs/README when needed
• I considered backwards compatibility

Link to Devin session: https://app.devin.ai/sessions/649e446c800a420c891a8c304134315a
Open in Devin Desktop: https://app.devin.ai/desktop/session/649e446c800a420c891a8c304134315a?variant=devin
Requested by: @zahlekhan

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring

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Project	Deployment	Actions	Updated
openui-docs	Ready	Preview	Sep 29, 2026 5:37am UTC