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feat(app-router): send X-Vinext-Router-Skip on navigation requests [4/6]#841

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NathanDrake2406 wants to merge 4 commits intocloudflare:mainfrom
NathanDrake2406:feat/pr-768-4-skip-header-transport
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feat(app-router): send X-Vinext-Router-Skip on navigation requests [4/6]#841
NathanDrake2406 wants to merge 4 commits intocloudflare:mainfrom
NathanDrake2406:feat/pr-768-4-skip-header-transport

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Summary

PR 4 of 6 — restack of #768. Stacked on #840.

Introduces `buildSkipHeaderValue` and `createRscNavigationRequestHeaders` in `app-elements.ts`. The client-side browser entry now uses the centralized request-header builder for navigation fetches and forwards the current layout flags so subsequent navigations can signal which static layouts the server may omit from the response body.

PR 3's server-side filter remains gated by `supportsFilteredRscStream: false`, so this PR only wires the transport; no behavior change until a later PR flips the gate.

Stack

  1. [1/6] refactor(app-rsc-entry): centralize request-derived page inputs [1/6] #838 — centralize request-derived page inputs
  2. [2/6] feat(app-router): emit per-layout flags in the RSC payload [2/6] #839 — emit per-layout flags in the RSC payload
  3. [3/6] feat(app-router): filter skipped layouts from RSC responses and cached reads [3/6] #840 — filter skipped layouts from RSC responses and cached reads
  4. [4/6] this PR — send X-Vinext-Router-Skip on navigation requests
  5. [5/6] wire build-time layout classification
  6. [6/6] classification reasons sidecar

Test plan

  • `tests/app-elements.test.ts` (35 tests, includes header builder cases)
  • `tests/app-browser-entry.test.ts` (24 tests)

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pkg-pr-new bot commented Apr 14, 2026

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npm i https://pkg.pr.new/vinext@841

commit: 939d4b7

Wire runtime layout classification through renderAppPageLifecycle and
attach the resulting flags as __layoutFlags in the outgoing RSC payload
via buildOutgoingAppPayload. Payload-shape helpers (withLayoutFlags,
isAppElementsRecord, buildOutgoingAppPayload, AppOutgoingElements) live
alongside the existing readAppElementsMetadata so the write and read
boundaries sit next to each other.
…dant clone

- isAppElementsRecord narrowed to Record<string, ReactNode>, but the
  outgoing payload legitimately carries heterogeneous values (ReactNode
  for the rendered tree plus LayoutFlags under __layoutFlags). Widen the
  predicate to Readonly<Record<string, unknown>> so the return type
  matches what the runtime check actually proves.

- buildOutgoingAppPayload spread input.element into a new object before
  passing it to withLayoutFlags, which immediately spreads again. Drop
  the outer copy; withLayoutFlags already guarantees immutability.
…d reads

Introduce app-page-skip-filter.ts with the canonical-bytes guarantee:
the render path always produces the full RSC payload and writes it to
the cache; the egress branch applies a byte-level filter that omits
layouts the client asked to skip, but only if the server independently
classified them as static (computeSkipDecision).

Wire the filter into renderAppPageLifecycle and buildAppPageCachedResponse
so both fresh renders and cache hits honor the skip header. Parse the
incoming X-Vinext-Router-Skip header at the handler scope and thread
the resulting set through render and ISR.

Gate the filter behind supportsFilteredRscStream: false in the generated
entry so this PR is dormant at runtime until the canonical-stream story
is validated. Tests exercise the filter directly by injecting the skip
set into renderAppPageLifecycle options.
Introduce buildSkipHeaderValue and createRscNavigationRequestHeaders
in app-elements. The client-side browser entry now uses the centralized
request-header builder for navigation fetches and forwards the current
layout flags so subsequent navigations can signal which static layouts
the server may omit from the response body.
@NathanDrake2406 NathanDrake2406 force-pushed the feat/pr-768-4-skip-header-transport branch from 3f9be3b to 939d4b7 Compare April 15, 2026 03:46
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