# Flags SDK 4.0.6

- Product: Flags SDK (https://whatsnew.fyi/product/flags-sdk)
- Vendor: Vercel
- Date: 2026-04-03
- Version: 4.0.6
- Original notes: https://github.com/vercel/flags/releases/tag/flags%404.0.6
- Permalink: https://whatsnew.fyi/product/flags-sdk/releases/4.0.6

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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- **changed** — Improve performance by caching next/headers imports to avoid unnecessary event loop iterations in Next.js App Router
- **changed** — Reduce microtask queue overhead in flag evaluation by replacing async IIFE around decide() with direct call and Promise.resolve()

###### Patch Changes

-   c08f3e5: Improve performance by caching `next/headers` imports.

    Previously every flag evaluation in Next.js App Router would run
    `await import("next/headers")`. The imported module is cached by
    the runtime, but we would still go through the event loop unnecessarily.

    Now we cache the resolved module in a local variable so only the
    first call awaits the dynamic import; subsequent calls skip the
    microtask entirely.

-   c08f3e5: Reduce microtask queue overhead in flag evaluation by replacing the async IIFE around `decide()` with a direct call and `Promise.resolve()`.