Next.js Daily: Safari HMR Fix and Turbopack Improvements

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Good morning. This is Next.js Daily for April 1st, 2026.

Luke Sandberg merged a critical fix for CSS Hot Module Replacement on Safari. The issue stemmed from query string handling in script tags that was interfering with Safari's preload cache, preventing style updates during development. This was causing significant developer experience issues on Safari.

Niklas Mischkulnig contributed Turbopack improvements for targeting older browsers, addressing compatibility issues with legacy JavaScript engines. The team also optimized hot path performance by replacing regex-based file type checks with faster string operations using indexOf and startsWith.

Sandberg also simplified session-dependent task handling in Turbo Tasks, moving from runtime flags to compile-time attributes. This change enables better aggregation number selection and includes new TTL support for HTTP fetch operations that respect Cache-Control headers.

The team upgraded agent evaluation tools to version 0.9.5, adding new tests for Partial Pre-rendering knowledge. These evaluate whether the AI agent correctly decomposes monolithic loading components into granular Suspense boundaries.

Security improvements included pinning 19 GitHub Actions to specific commit SHAs rather than mutable version tags, following security best practices to prevent supply chain attacks.

Documentation updates addressed the breaking change in revalidateTag, which now requires a second argument in Next.js 16. The upgrade guide now includes before-and-after examples to help developers migrate from the single-argument syntax.

Additional work included TypeScript configuration updates for version 6 deprecations, test suite maintenance to address flaky segment cache tests, and improvements to error messages for deprecated experimental configurations.

What's next: The team continues work on Turbopack performance optimizations and Partial Pre-rendering stability improvements.

That's Next.js Daily. We'll be back tomorrow with the latest updates.