feat(tracing): add App response start spans

[james-elicx]

Summary

• add the Next.js-compatible NextNodeServer.startResponse boundary for matched App Pages and Route Handlers through the shared framework tracer
• emit on the first response write while preserving App render parentage, request lifetime, fully-buffered metadata, Workerd response state, and Link provenance
• trace Response Store and Workers Cache HTML/Route Handler replays while keeping App RSC responses untraced, matching Next.js
• run the unchanged @sentry/nextjs fixture through real self-contained Response Store and a focused Workers Cache project

No OpenTelemetry package becomes a vinext dependency, and there is no Sentry-specific framework tracing path.

Stack

Depends on #3270 (feat(tracing): add App segment module spans).

Validation

• vp check
• focused tracing/App unit suites: 187 passed before the final cache-representation additions; final tracing suite: 16 passed
• pnpm --filter @vinext/cloudflare test: 30 passed
• Sentry + self-contained Response Store: 18 passed
• Sentry + Workers Cache replay: 2 passed
• concurrent Response Store and Workers Cache replay projects: 2 passed each
• two independent final reviews: clean

[james-elicx]

/bigbonk review for issues. You have an eight-minute time limit: report all concrete findings within eight minutes, prioritizing response stream lifecycle, Next.js startResponse parity, cache HIT/RSC representation handling, Workerd Response state, and Sentry/Workers tracing architecture.

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[pkg-pr-new]

Open in StackBlitz

@vinext/cloudflare

npm i https://pkg.pr.new/cloudflare/vinext/@vinext/cloudflare@3271

create-vinext-app

npm i https://pkg.pr.new/cloudflare/vinext/create-vinext-app@3271

@vinext/types

npm i https://pkg.pr.new/cloudflare/vinext/@vinext/types@3271

vinext

npm i https://pkg.pr.new/cloudflare/vinext@3271

@cloudflare/workers-response-store

npm i https://pkg.pr.new/cloudflare/vinext/@cloudflare/workers-response-store@3271

commit: 447a9ed

[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
response-store-demo	preview	production
static-export	preview	production
web	preview	production

[github-actions]

Performance benchmarks

Compared 447a9ed against base 09ffc24 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	142.3 KB	142.3 KB	⚫ +0.0%
Client entry size (gzip)	vinext	129.7 KB	129.7 KB	⚫ +0.0%
Dev server cold start	vinext	3.29 s	3.25 s	⚫ -1.0%
Production build time	vinext	3.81 s	3.80 s	⚫ -0.3%
RSC entry closure size (gzip)	vinext	125.3 KB	125.7 KB	⚫ +0.3%
Server bundle size (gzip)	vinext	215.9 KB	216.3 KB	⚫ +0.2%

View detailed results and traces

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