# Next.js v16.4.0-canary.1

- Product: Next.js (https://whatsnew.fyi/product/next-js)
- Vendor: Vercel
- Date: 2026-08-21
- Version: v16.4.0-canary.1
- Original notes: https://github.com/vercel/next.js/releases/tag/v16.4.0-canary.1
- Permalink: https://whatsnew.fyi/product/next-js/releases/v16.4.0-canary.1
- Labels: Pre-release

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

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- **fixed** — Fix parallelRouteKey parameter name in useSelectedLayoutSegment(s)
- **changed** — Avoid cloning paths in fs watcher if the path is already in a map
- **removed** — Remove generated error codes
- **added** — Add instant validation for unstable_navigation()
- **changed** — Trace graceful-fs calls in Turbopack
- **changed** — Migrate some async blocks to async closures
- **added** — Add scope_unbounded, a scoped execution primitive that allows more work to be discovered
- **added** — Add a Turbopack error for missing root layouts
- **changed** — Improve Partial Prefetching adoption checks
- **changed** — Correct the upper stale bound for App Shell exclusion in cacheLife
- **added** — Add unstable_prefetch() function for Partial Prefetching
- **changed** — Clarify beforeInteractive placement for root layouts
- **fixed** — Give eager import.meta.glob values the ESM namespace

###### Misc Changes

- docs: fix parallelRouteKey parameter name in useSelectedLayoutSegment(s): #97710
- Turbopack: Avoid cloning paths in fs watcher if the path is already in a map: #97655
- Remove generated error codes: #97687
- [PPF] Instant validation for unstable_navigation(): #97309
- Turbopack: trace graceful-fs calls: #97694
- Migrate some async blocks to async closures: #97666
- turbo-tasks: add scope_unbounded, a scoped execution primitive that allows more work to be discovered: #95974
- test: make app-document-import-order more robust: #97682
- Add a Turbopack error for missing root layouts: #97639
- Improve Partial Prefetching adoption checks: #97637
- test: stabilize poisoned proxy error overlay: #97609
- docs: correct the upper stale bound for App Shell exclusion in cacheLife: #97653
- docs: Adapters entry page lists its children pages twice: #97677
- [PPF] unstable_prefetch(): #97622
- [PPF] Scaffold unstable_prefetch(): #97618
- docs: clarify beforeInteractive placement for root layouts: #97643
- fix(turbopack): give eager `import.meta.glob` values the ESM namespace: #96559

###### Credits 

Huge thanks to @marcoshernanz, @bgw, @devjiwonchoi, @lubieowoce, @mischnic, @lukesandberg, @DavidIlie, @aurorascharff, @sokra, and @icyJoseph for helping!