fix(tracing): retain request spans through response streams

[james-elicx]

Summary

• keep the shared BaseServer.handleRequest trace active until a streamed response reaches EOF or is cancelled
• report late response-stream failures through the same framework tracer and preserve Workerd response host state while wrapping bodies
• retain fully buffered response behavior across worker stages, including Workerd-generated Content-Length
• prove late application-span parentage with the real @sentry/nextjs Workerd fixture

Next.js and runtime parity

The request root now covers the response producer lifetime on both Node and Workers. The implementation remains backend-neutral: Sentry/OpenTelemetry and Workers tracing consume the same framework span, with no Sentry runtime code and no required OpenTelemetry dependency.

The Workerd regression deliberately fails with the old plain ResponseInit reconstruction because it double-encodes a manual gzip body. Fully buffered metadata responses remain unwrapped and retain their wire-level Content-Length.

Validation

• vp check
• vp test run tests/request-tracing.test.ts tests/workers-tracing.test.ts tests/after-response-close-worker.test.ts (27 passed)
• vp run vinext#build
• PLAYWRIGHT_PROJECT=cloudflare-sentry-app pnpm run test:e2e (16 passed)
• independent correctness review: clean after addressing response host-state and stream-failure findings
• independent Next.js parity review: clean

Stack parent: #3267

[james-elicx]

/bigbonk review for issues. Please focus on streamed request-span lifetime, failure/cancellation settlement, Workerd Response host-state preservation, and fully-buffered response behavior. You have an 8-minute time limit; report only actionable findings you can establish within it.

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@vinext/cloudflare

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create-vinext-app

npm i https://pkg.pr.new/cloudflare/vinext/create-vinext-app@3268

@vinext/types

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vinext

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@cloudflare/workers-response-store

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commit: b697924

[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 b697924 against base 0bead68 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	129.6 KB	129.7 KB	⚫ +0.0%
Dev server cold start	vinext	3.18 s	3.19 s	⚫ +0.4%
Production build time	vinext	3.46 s	3.47 s	⚫ +0.4%
RSC entry closure size (gzip)	vinext	124.3 KB	124.5 KB	⚫ +0.2%
Server bundle size (gzip)	vinext	214.8 KB	215.1 KB	⚫ +0.1%

View detailed results and traces

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