perf:document only router runtime

[TheAlexLichter]

This PR omits the heavy App Router client runtime in production builds when build-time client-reference analysis proves no user client component needs router state.

It rewrites next/link client references to a lightweight document-navigation shim in that case, while conservatively falling back to the full runtime for:

• pages,
• i18n,
• instrumentation,
• server actions,
• external/unknown graph edges,
• next/navigation usage

Note: This only helps apps with client islands that do not pull in next/link, next/form, router hooks, next/router, etc. So “static page plus isolated widgets” benefit from this change.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@vinext/cloudflare@2492

npm i https://pkg.pr.new/vinext@2492

commit: e85ef72

[github-actions]

Example	Preview	Production	Original
app-router-cloudflare	preview	production
pages-router-cloudflare	preview	production
app-router-playground	preview	production	original
realworld-api-rest	preview	production
nextra-docs-template	preview	production
benchmarks	preview	production
hackernews	preview	production	original
workers-cache	preview	production
web	preview	production

[github-actions]

Performance benchmarks

Compared e85ef72 against base 6c7b71e using alternating same-runner rounds. Next.js was unchanged and skipped.

0 improved · 1 regressed · 5 within ±1.5%

Scenario	Framework	Baseline	Current	Change
Client bundle size (gzip)	vinext	126.3 KB	126.4 KB	⚫ +0.1%
Client entry size (gzip)	vinext	120.4 KB	120.5 KB	⚫ +0.1%
Dev server cold start	vinext	2.62 s	2.60 s	⚫ -0.8%
Production build time	vinext	3.13 s	3.19 s	🔴 +1.9%
RSC entry closure size (gzip)	vinext	97.9 KB	98.0 KB	⚫ +0.1%
Server bundle size (gzip)	vinext	164.4 KB	164.5 KB	⚫ +0.1%

View detailed results and traces

_{🟢 improvement · 🔴 regression · ⚫ change below 1.5% · paired base/head}