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Metadata streaming: parallel route slot metadata not emitted #1341
Description
This issue was created by an agent analysing CI failures from the Next.js Deploy Suite (vinext
mainvs Next.jsv16.2.6, 2026-05-20).
Problem
Metadata from parallel route slots is not properly emitted or updated:
-
Empty title in parallel routes. When a parallel routes layout sets metadata but does not render
children, the<title>tag is empty instead of containing the layout's metadata. -
Stale metadata on slot navigation. Navigating between pages under a parallel route slot does not update the
<title>tag. It stays on the layout's default title instead of switching to the page-specific title. -
Missing charset meta. The root not-found page renders without
<meta charset="utf-8">when metadata streaming is active.
Expected: "parallel-routes-default layout title"
Received: ""
Expected: "first page - @bar"
Received: "parallel-routes-default layout title"
Expected: 1 // meta[charset="utf-8"] count
Received: 0
Estimated Impact
~8 test failures across the deploy suite.
Affected Test Suites
test/e2e/app-dir/metadata-streaming-parallel-routes/metadata-streaming-parallel-routes.test.ts(2 failures)test/e2e/app-dir/metadata-navigation/metadata-navigation.test.ts(4 failures)test/e2e/app-dir/metadata-streaming/metadata-streaming.test.tstest/e2e/app-dir/metadata-streaming-static-generation/metadata-streaming-static-generation.test.ts(2 failures)
Recommendation
-
Reproduce first in vinext's own test suite. Add a test with parallel routes that set different metadata at each level and verify the correct title renders. Confirm it fails.
-
Study Next.js metadata resolution for parallel routes. The metadata resolution logic needs to walk all slots, not just the
childrenslot, when determining which metadata to emit. -
Fix client-side metadata updates during slot navigation. When navigating within a parallel route slot, the metadata should update to reflect the new page's metadata.
Activity
fix(metadata): emit metadata from parallel route slots (#1399)
james-elicx commentedon May 22, 2026
This may be regressing - observed again in the Next.js Deploy Suite nightly run on 2026-05-22 (vinext
mainvs Next.jsv16.2.6): 8 failures across 5 test suites with symptoms matching this issue.Affected suites this run
test/e2e/app-dir/metadata-navigation/metadata-navigation.test.ts(3 failures)test/e2e/app-dir/metadata-streaming-static-generation/metadata-streaming-static-generation.test.ts(2 failures)test/e2e/app-dir/global-not-found/metadata/metadata.test.ts(1 failures)test/e2e/app-dir/metadata-static-generation/metadata-static-generation.test.ts(1 failures)test/e2e/app-dir/metadata-streaming-parallel-routes/metadata-streaming-parallel-routes.test.ts(1 failures)james-elicx commentedon Jun 8, 2026
Triage update (agent investigation): the localized part of this issue — parallel route slot title emission when a slot layout doesn't render
children— is already fixed onmainby #1399 (fix(metadata): emit metadata from parallel route slots, which refs this issue):app-page-head.tscontributesTitlelogic +tests/app-page-head.test.tscoverage. Verified passing on main for both SSR render and slot-to-slot navigation (@bar/first→@bar/secondupdates the title correctly).The residual deploy-suite failures (
metadata-navigation,metadata-streaming-static-generation,metadata-static-generation,global-not-found/metadata) are a narrower, harder problem:<meta charset="utf-8">/ head ordering under React streaming suspension during production static generation on the not-found path — not reproducible in dev SSR and not a small localized patch. Repro recipe: prod build (vp build+ Workers/static-generation Playwright project) with anot-found.tsx/global-not-found.tsxexportinggenerateMetadata, then assertmeta[charset=utf-8]count === 1 in the streamed HTML. Likely belongs in the static-generation/streaming head emission, notapp-page-head.ts. Leaving open for that residual.james-elicx commentedon Jul 4, 2026
Closing as passing in the Next.js Deploy Suite run https://github.com/cloudflare/vinext/actions/runs/28692899743 (vinext main at
54497d42e7fa0effd567950534a3b6f562c14218, July 4, 2026). The assertions tracked by this issue passed in that run. The run still has unrelated failures, which remain tracked separately.