fix(cache): preserve Cache Components ownership during probing

[james-elicx]

Capability stack 5/9. Exact head: e2f05581bd12c6e0bd96899a068adfd542e82dc2. Base: #3092.

Full chain: #3108 → #3090 → #3091 → #3092 → #3103 → #3093 → #3094 → #3098 → #3113.

This supersedes #3095, whose stale descendant base caused GitHub to mark it merged without landing anything on main.

Summary

This aligns staged probes with Next.js Cache Components ownership semantics:

• public use cache owns inner fetch(..., { cache: "no-store" }), so that fetch does not demote the enclosing route
• use cache: private marks Cache Components routes dynamic and suspends before private user code or cache-key construction
• the outer prerender owns that suspension, preventing try/catch or Suspense fallbacks from producing a false static classification
• private cache nested inside public use cache or unstable_cache() fails synchronously and cannot persist private output
• legacy unstable_cache entries use a versioned physical namespace, preventing older private output from bypassing the nesting guard
• genuine application 5xx responses remain probe failures
• legacy non-Cache-Components io() continues immediately and remains eligible for static probing, matching Next.js
• ordinary App Router requests avoid probe-only ownership allocation

Next.js references

• test/e2e/app-dir/use-cache/use-cache.test.ts
• test/e2e/app-dir/cache-components-errors/use-cache-private.util.ts
• packages/next/src/server/use-cache/use-cache-wrapper.ts
• packages/next/src/server/request/io.ts

Review guide

1. prerender-work-unit-setup.ts selects legacy versus Cache Components work-unit ownership.
2. cache-runtime.ts enforces public/private cache nesting.
3. cacheability-classification.ts propagates dynamic ownership to the outer render.
4. cacheability-ownership.spec.ts covers Cache Components and seeded legacy cache entries under built workerd.
5. cacheability-probe.spec.ts covers legacy io() parity.

Review size

Layer-only diff against this PR's base: 31 files, +677/-74.

Validation

• Cache Components built-workerd E2E — 1/1
• prior cumulative focused validation through feat(cache): probe Pages Router cacheability #3098 — 2,024/2,024
• current full-stack cumulative changed-file suites — 2,864/2,864
• current full-stack PPR probe/admission/Pages built-workerd E2E — 8/8
• current full-stack vp check and git diff --check
• layer exact-head CI and deploy previews are green

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@vinext/cloudflare@3103

npm i https://pkg.pr.new/create-vinext-app@3103

npm i https://pkg.pr.new/@vinext/types@3103

npm i https://pkg.pr.new/vinext@3103

commit: e2f0558

[github-actions]

Performance benchmarks

Compared bc44dcc against base 6946d43 using alternating same-runner rounds. Next.js was unchanged and skipped.

0 improved · 0 regressed · 6 within ±1.5%

Scenario	Framework	Baseline	Current	Change
Client bundle size (gzip)	vinext	142.2 KB	142.3 KB	⚫ +0.0%
Client entry size (gzip)	vinext	129.5 KB	129.5 KB	⚫ +0.0%
Dev server cold start	vinext	3.34 s	3.34 s	⚫ +0.0%
Production build time	vinext	3.77 s	3.77 s	⚫ +0.2%
RSC entry closure size (gzip)	vinext	118.8 KB	118.9 KB	⚫ +0.2%
Server bundle size (gzip)	vinext	202.1 KB	202.3 KB	⚫ +0.1%

View detailed results and traces

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

[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
static-export	preview	production
web	preview	production