Middleware rewrite target route resolution uses wrong priority

This issue was created by an agent analysing CI failures from the Next.js Deploy Suite (vinext main vs Next.js v16.2.6, 2026-05-20).

Problem

After middleware rewrites a request URL, the rewritten path is matched against the route table with incorrect priority. Dynamic catch-all routes ([id]/[slug]) capture the rewrite target instead of resolving to the correct static or named page.

For example, when middleware rewrites /rewrite-1 to /:

• Expected: The home page renders ("Hello World")
• Actual: The [id] dynamic route captures it, rendering "Dynamic route" with query.id = "rewrite-1"

Expected substring: "Hello World"
Received string:    "...<p class=\"title\">Dynamic route</p>..."

This also affects:

• Rewrites to named pages like /about (renders [id] instead)
• External rewrites (to example.com) resulting in 404 instead of proxying
• fallback: true pages rendering full data immediately instead of the fallback/loading state

Estimated Impact

~35 test failures across the deploy suite.

Affected Test Suites

• test/e2e/middleware-trailing-slash/test/index.test.ts (~10 failures)
• test/e2e/middleware-rewrites/test/index.test.ts (~12 failures)
• test/e2e/basepath/redirect-and-rewrite.test.ts
• test/e2e/app-dir/app-middleware-proxy/app-middleware-proxy.test.ts

Recommendation

1. Reproduce first in vinext's own test suite. Add a test case with a middleware that rewrites to a known static page and a dynamic [id] route. Assert the static page renders, not the dynamic route. Confirm it fails.

2. Study Next.js route matching after rewrites. In Next.js, after a middleware rewrite, the rewritten URL is re-matched against the full route table with proper priority: static routes > predefined dynamic routes > catch-all routes. Search .nextjs-ref/packages/next/src/server/ for how post-rewrite matching works.

3. Fix the post-rewrite route matcher. The rewritten path should go through the full filesystem route resolution, not just dynamic route matching. Static routes and named pages must take priority over dynamic catch-alls.

4. Implement external URL proxying for rewrites. When middleware rewrites to an absolute external URL (e.g., https://example.com), the server should proxy the request to that URL and return the response, rather than matching it against local routes.

5. Check dev/prod parity. Ensure the fix applies to both server/dev-server.ts and server/prod-server.ts.