[Next.js/dylib] Full production App Route compatibility tracker

[proggeramlug]

Goal

Run a real production Next.js 16 App Route as an app-only Perry dylib, with runtime and stdlib supplied once by separate shared provider images, and pass the same black-box verifier as Node without compatibility fallbacks.

This is the correctness gate required before the Perry-vs-Node 1/10/100 deployment RSS, CPU, and startup comparison is meaningful. The current benchmark is promising but lower-bound-only because it calls userland directly and fabricates the final response.

Fixed reproduction — do not design another app

#8034 contains a complete copy/paste fixture generator pinned to Next.js 16.3.0 / React 19.2.4, plus a 21-request verifier. The app already exercises:

• production next build --webpack output;
• the generated routeModule.handle / AppRouteRouteModule.handle path;
• a re-exported imported GET/POST handler;
• method, pathname, query, headers, and POST body;
• Next's AsyncLocalStorage-backed headers() before and after async continuations;
• a request-time dynamic import;
• a two-chunk streamed NextResponse;
• status, custom response header, and Set-Cookie; and
• 20 distinct concurrent request contexts.

Every child issue uses that app. Smaller compiler/runtime fixtures are welcome for localization, but they cannot replace #8034 as acceptance evidence.

Work items

• [Next.js/dylib] Add a pinned production App Route parity fixture and CI gate #8034 — commit the pinned production fixture and add the app-only-dylib CI gate
• [Next.js/dylib] Preserve NextRequest and nextUrl.searchParams across App Route imports #8036 — preserve NextRequest and nextUrl.searchParams across the production import/re-export boundary
• [Next.js/dylib] Preserve returned NextResponse headers, cookies, and stream across module boundaries #8038 — preserve returned NextResponse status, headers, cookies, and stream
• [Next.js/dylib] Preserve request/work AsyncLocalStorage through concurrent App Routes #8037 — preserve Next request/work AsyncLocalStorage under concurrent App Routes (scoped cut of [parity] node:async_hooks — 113 failing node-suite tests (2026-07-22 baseline) #6764)
• [Next.js/dylib] Make production webpack App Route lazy loading deadlock-free #8039 — make cold/concurrent production webpack route and dynamic-module loading deadlock-free
• [GC/dylib] Install array-growth forwarding for low-address macOS arena allocations #8035 — install array-growth forwarding for valid low-address macOS arena allocations

Existing groundwork to retain

• Next.js 16 standalone app-router bring-up — walls 1–5 (codegen/runtime/HIR fixes) #5438: production .next/server/** discovery and path-based lazy module initialization
• fix(url): route URLSearchParams subclass instances to their native backing #6738: native backing for URLSearchParams subclasses
• fix(gc): root every argument of a cross-module direct call (#7240, by @jdalton) #7252: GC rooting for cross-module call arguments
• Web Streams API: implement ReadableStream + blob.stream() / response.body #237 and Web Fetch: Response.body is a numeric handle, not a ReadableStream | null #1650: Web Streams / Response.body groundwork
• [parity] node:async_hooks — 113 failing node-suite tests (2026-07-22 baseline) #6764: broad node:async_hooks parity inventory

These reduce the work but do not replace the composed production test. If current main already fixes a child behavior, close that child with a #8034 regression proving it rather than with a synthetic-only test.

Suggested execution order

1. Land [Next.js/dylib] Add a pinned production App Route parity fixture and CI gate #8034's Node oracle and a Perry test marked expected-fail, recording the exact current Perry SHA and first failing boundary.
2. Fix [GC/dylib] Install array-growth forwarding for low-address macOS arena allocations #8035 independently so GC diagnostics and stale growth references cannot contaminate later debugging.
3. Make the request enter and survive the real route boundary ([Next.js/dylib] Preserve NextRequest and nextUrl.searchParams across App Route imports #8036).
4. Make cold production modules initialize exactly once ([Next.js/dylib] Make production webpack App Route lazy loading deadlock-free #8039).
5. Make Next's request/work context survive concurrency and continuations ([Next.js/dylib] Preserve request/work AsyncLocalStorage through concurrent App Routes #8037).
6. Carry and drain the real returned response ([Next.js/dylib] Preserve returned NextResponse headers, cookies, and stream across module boundaries #8038).
7. Remove the expected-fail marker and every compatibility branch; run the full stability matrix below.

Items 2–6 may proceed in parallel when their focused fixtures isolate them, but #8034 is the shared final oracle.

Definition of done

• Runtime and stdlib are separate provider files loaded once per process.
• The target app dylib excludes embedded runtime/stdlib implementations and resolves the documented provider ABI.
• Providers load first; the app loads with eager relocation so first-request binding latency is not hidden.
• The production webpack build enters the actual generated App Route module and private handle pipeline.
• [Next.js/dylib] Add a pinned production App Route parity fixture and CI gate #8034's verifier passes on Node and Perry with identical observable status, headers/cookie, and JSON.
• Ten consecutive cold Perry process starts pass; each process passes two verifier runs.
• A 100-iteration run of the 20-way concurrent request batch has zero context leaks, hangs, truncations, or wrong values.
• Normal GC and forced/verified GC runs pass.
• Startup/request stderr contains no skipped-forwarding, unsettled-await, unimplemented, or compatibility-fallback diagnostic.
• A source/test audit finds no direct userland GET invocation, ignored Response, hard-coded output, lazy-module eager-init workaround, or legacy fallback in the Perry path.

Explicitly out of scope

• Turbopack; this first gate pins webpack.
• The final performance verdict and thresholds.
• Eager relocation optimization for 100 unique app images.
• Completing every unrelated async_hooks provider failure in [parity] node:async_hooks — 113 failing node-suite tests (2026-07-22 baseline) #6764.

Once this tracker is green, run the separate performance matrix for 1, 10, and 100 copies of the same real Next deployment, followed by 100 distinct builds, against one Node process per app and a defensible shared-Node topology.

Baseline

The lower-bound observation was recorded with Perry 0.5.1503 at 564c56308d221a51b50308d9165578fbb176e877. Reproduce #8034 on current main before implementing and record that SHA in the test output; do not assume the old baseline identifies the first current failure.

[proggeramlug]

Production App Route replay on exact merged main b0f13fb5 advanced to 91/91 emitted objects, then exposed dedicated final-link blocker #8064 (___perry_wrap_perry_unknown_func duplicated by four split production modules). This is after all #8057 failures cleared. #8034 remains open; no generated route execution or moving/verifier acceptance has occurred yet.