Fastify 5.9.0

OK FASTIFY 5.9.0 JUST DROPPED

Y'all, Fastify 5.9.0 is live on npm RIGHT NOW and it comes with a slick new feature that devs have been quietly asking for. Let's get into it period.

The Big One: request.mediaType

Thanks to @climba03003 (pull #6653), every Fastify request object now has a request.mediaType property. This extracts the media type straight from the Content-Type header -- no more manual parsing. If the header is missing, it returns undefined. Clean. Simple. Perfect.

This means you can finally do content negotiation without bringing in an extra lib.

Housekeeping and Docs Cleanup

@Tony133 cleaned up the ecosystem docs by removing the deprecated leveldb plugin reference (#6661). If you were still holding onto that -- time to let go period.

There are also several dependency bumps and internal maintenance PRs keeping the framework lean and secure. The team is NOT slowing down.

Security Baseline Tightened

This release follows on the heels of 5.8.5 which patched CVE-2026-33806. The Fastify team is taking security seriously -- update or get left behind.

Upgrade now: npm install fastify@latest

Go update rn