[codex] Fix wrangler dev suspense streaming

[southpolesteve]

Summary

• Add a local Wrangler dev response wrapper that sets Content-Encoding: identity for streamed loopback App Router responses without explicit body headers.
• Replace whole-line RSC Flight hint buffering with a streaming transform so partial non-hint rows can flow immediately.
• Keep the SSR HTML/RSC embed flush independent of host timers while preserving tick-level batching.

Root Cause

wrangler dev/Miniflare buffers streamed non-SSE responses unless compression is explicitly avoided. The behavior reproduces with a plain ReadableStream route, outside React and vinext rendering. Setting Content-Encoding: identity restores chunk delivery locally.

This aligns with upstream Cloudflare workers-sdk issue #8004, which describes Miniflare aggressively buffering responses and lists Content-Encoding: identity as the workaround.

Validation

• npx vp test run tests/app-ssr-stream.test.ts tests/rsc-streaming.test.ts tests/deploy.test.ts -t "applyLocalDevStreamingHeaders|host timers|createFlightHintFixTransform"
• npx vp check packages/vinext/src/server/worker-utils.ts packages/vinext/src/server/app-router-entry.ts packages/vinext/src/server/app-ssr-stream.ts packages/vinext/src/server/flight-hints.ts packages/vinext/src/entries/app-rsc-entry.ts tests/app-ssr-stream.test.ts tests/rsc-streaming.test.ts tests/deploy.test.ts
• npx vp run vinext#build
• Manual Wrangler repro: before the workaround /streaming buffered until ~830ms; after the workaround the fallback arrived at ~47ms and resolved content at ~834ms.

[southpolesteve]

This might be a sufficient workaround for the reported wrangler dev streaming problem, but I do not think we should treat it as the final answer yet.

The buffering reproduces with a plain ReadableStream response outside React/vinext, and it lines up with the upstream Miniflare buffering issue tracked in cloudflare/workers-sdk#8004. If this is fixed upstream, we should prefer that path and avoid keeping a vinext-specific workaround unless we decide the local-dev compatibility value is worth the extra response-header behavior.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/vinext@879

commit: b08ce9a

[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

[LubomirGeorgiev]

Ref #874