fix(aws): copy server/instrumentation.js into standalone dir on Next.js 16

[JiahaoZhu11]

Problem

On Next.js 16, open-next build fails during the server-function bundle:

Error: This error should only happen for static 404 and 500 page from page router. Report this if that's not the case.,
        File server/instrumentation.js does not exist
    at computeCopyFilesForPage (.../build/copyTracedFiles.js)
    at copyTracedFiles (...)
    at createServerBundle (...)

Root cause

Next 16's output: "standalone" no longer copies server/instrumentation.js into the standalone output dir (it remains only in .next/server/). In copyTracedFiles, the instrumentation block copies the instrumentation .nft.json trace into standaloneNextDir and then calls computeCopyFilesForPage("instrumentation"), which asserts that server/instrumentation.js exists in standaloneNextDir — so it throws. (Middleware is unaffected because its .js is emitted into the standalone dir.)

Fix

Before the assertion, copy server/instrumentation.js from the build dir into the standalone dir — mirroring the existing .nft.json copy right above it — guarded so it only runs when the file exists in the build dir and isn't already present in the standalone dir. Pre-16 behavior is unchanged, and the instrumentation file ships in the bundle.

Validation

Reproduced on a real pnpm monorepo app: Next.js 16.1.6, App Router, next-intl middleware, @opennextjs/aws@4.0.3, monorepo config (packageJsonPath / appPath / buildOutputPath) + output: "standalone" + outputFileTracingRoot.

• Before: build fails at copyTracedFiles with the error above.
• After (this change applied as a patch to 4.0.3): open-next build completes; the full bundle is produced (server-functions/default, assets, cache, dynamodb-provider, revalidation-function, image-optimization-function, warmer-function); the server-function bundle loads and exports handler; server/instrumentation.js is present in the server-function output.

A patch changeset is included.

🤖 Generated with Claude Code

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🦋 Changeset detected

Latest commit: 2629b67

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@opennextjs/aws	Patch
app-pages-router	Patch

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