Production bundle includes ~2.4 MB of dev-only artifacts (next-devtools, .development.js React)

[darrell19]

Description

After running opennextjs-cloudflare build (v1.20.2) with Next.js 15.5.22 and NODE_ENV=production, the resulting Worker bundle at .open-next/server-functions/default/handler.mjs contains ~2.4 MB of development-only artifacts that appear to be dead weight in production.

Artifacts found in production bundle

Path	Raw Size	Notes
next-devtools/index.js	822 KB	Dev tooling — should not be in prod
react-dom-server.edge.development.js	425 KB	.development.js variant
react-dom-server.browser.development.js	424 KB	.development.js variant
react-dom-server-legacy.browser.development.js	395 KB	.development.js variant
react.development.js	present	.development.js variant
react-jsx-runtime.development.js	present	.development.js variant

Total dev-only weight: ~2.4 MB raw

Impact

• Bundle is at ~85% of Workers' 3 MB compressed ceiling (2.5 MB gzipped of the 3 MB limit on the paid plan). These artifacts consume most of the remaining headroom.
• Cold-start amplification — every byte of the bundle is parsed on isolate cold start. Removing ~2.4 MB of dead code would measurably reduce cold-start latency.
• No production code path executes these files — verified by grepping the handler for references. They appear to be bundled defensively or included by the build pipeline without a production/development gate.

Reproduction

npx @opennextjs/cloudflare build   # NODE_ENV=production (the default)
# Inspect the output:
find .open-next/server-functions/default -name "*.development.*" -o -name "next-devtools" | head -20
ls -lh .open-next/server-functions/default/node_modules/next-devtools/
du -sh .open-next/server-functions/default/handler.mjs
gzip -c .open-next/server-functions/default/handler.mjs | wc -c

Question

Is this intentional (some runtime code path conditionally loads these), or is it a bundling oversight that could be gated on NODE_ENV? Is there a configuration flag to exclude them?

Environment

• @opennextjs/cloudflare: 1.20.2
• next: 15.5.22
• Node: 22.x
• OS: Linux (WSL2)
• Cloudflare Workers paid plan