fix(cloudflare): stop bundling @vercel/og when it is unused

[mushan0x0]

Fixes #1220 (and the original #1211).

Problem

Next.js's internal externalImport helper emits a dynamic

import("next/dist/compiled/@vercel/og/index.edge.js")

into the app handler even for apps that never use next/og (ImageResponse, opengraph-image, twitter-image, …). Today, when patchVercelOgLibrary decides useOg === false, bundle-server.ts marks that module as external:

external: [
  "./middleware/handler.mjs",
  // Do not bundle og when it is not used
  ...(useOg ? [] : ["next/dist/compiled/@vercel/og/index.edge.js"]),
],

esbuild honors external and leaves the import("…@vercel/og/index.edge.js") call site intact. Wrangler then resolves that external module against node_modules and bundles:

• @vercel/og edge bundle (~800 KiB uncompressed / ~260 KiB gzip)
• resvg.wasm (~1.4 MiB)

…even though the code path is unreachable. For CSR-heavy apps that never use OG images this single dynamic import pushes the Worker over the 3 MiB free-tier gzip limit.

Reproduced on a real Next 16 app with @opennextjs/[email protected] and 1.19.2:

build	wrangler deploy --dry-run
unpatched (useOg=false, external)	14098.57 KiB / gzip 3119.42 KiB ❌
after this PR	11875.51 KiB / gzip 2415.74 KiB ✅

(The same savings were previously achievable only via a post-build regex script that rewrote the emitted handler.)

Fix

When useOg === false, alias the edge entry to the existing throw.js shim instead of marking it external:

external: ["./middleware/handler.mjs"],
alias: {
  ...(useOg
    ? {}
    : {
        "next/dist/compiled/@vercel/og/index.edge.js": path.join(
          buildOpts.outputDir,
          "cloudflare-templates/shims/throw.js"
        ),
      }),
  // …
},

The unreachable dynamic import now resolves to a tiny throw "OpenNext shim" module, and Wrangler no longer drags the real @vercel/og library + resvg.wasm into the Worker bundle. If the dynamic import is ever executed at runtime (which would indicate a bug in patchVercelOgLibrary's useOg detection), the shim throws immediately — the same failure mode users already get from @ampproject/toolbox-optimizer and other shimmed modules, rather than a silent runtime mismatch.

When useOg === true the behavior is unchanged: the real edge build is copied and patched by patchVercelOgLibrary as before.

Why not a config flag?

The original issue proposed an opt-in flag (cloudflare: { disableVercelOg: true }), but the adapter already computes the exact signal it needs (useOg), so this can be done safely with no new config surface.

Validation

• pnpm --filter cloudflare test — 31 files / 317 tests pass.
• pnpm code:checks (prettier + eslint + tsc) — clean.
• End-to-end: built a real app (Next 16.2.4, app/ router, no next/og) against this fork, confirmed handler.mjs no longer contains next/dist/compiled/@vercel/og/index.edge.js and wrangler deploy --dry-run size dropped as shown above.

Changeset

Included as a patch bump under .changeset/drop-unused-vercel-og.md.

[changeset-bot]

🦋 Changeset detected

Latest commit: 8db8d43

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

This PR includes changesets to release 1 package

Name	Type
@opennextjs/cloudflare	Patch

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[vicb]

Great investigation!

LGTM, thank you so much for the fix!

[pkg-pr-new]

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npm i https://pkg.pr.new/@opennextjs/cloudflare@1221

commit: 8db8d43