v3.9.0-alpha2 (2026-07-29)

• Dependency: on Clojars
• Versioning: Break Versioning

EARLY PREVIEW: only for early testers, not suitable for production.

Major performance release. Includes new automatic keyword caching, and many other optimizations that together yield up to 2x faster performance in several common cases.

Intended as a non-breaking release, but touches a lot of core code. As always please test carefully before using for anything important, and please report any unexpected problems - thank you! 🙏

- Peter Taoussanis

Rolling updates

Updating Nippy with a rolling deployment (>1 coexisting Nippy version)?

Then please ensure you update step by step (e.g. v3.5 → v3.6 → v3.7) so that read support is fully deployed before the corresponding writes might happen.

New byte output

v3.9 changes the byte output of several common Nippy data types.

Almost no one should care about this, but mentioning for the tiny minority of users that depend on Nippy's byte output remaining stable.

Since v3.8.1 (2026-07-28)

• [new] Update benchmark results [df391d2]
• [prf] Cache: auto-cache keywords [03725ac]
• [prf] Freeze: enable tight packing by default [2705bb1]
• [prf] Freeze: copy-free compression [e36a2ff]
• [prf] Freeze: fast-path common elements [bbff6c6]
• [prf] Freeze: streamline common paths [50a56ac]
• [prf] Freeze: optimize default header copy [79f17cd]
• [prf] Thaw: direct transient loop for read-into [5f05346]
• [prf] Thaw: decode keywords from bytes [bff8c29]
• [prf] Thaw: build lists directly [5a417fc]
• [prf] Thaw: decode strings in place [2ac10be]
• [prf] Thaw: bulk-build short vectors [7fde2b1]
• [prf] Thaw: avoid header copies [d119f59]
• [prf] Crypto: reduce buffer copies [1b62a1d]
• [prf] Cache: use ArrayList for read-cached [ecb1206]
• [prf] Cache: identity maps for keywords [ac4958e]
• [prf] Cache: use mutable Java state [eecda2d]