This is the twenty-first major release in the Cats Effect 3.x lineage. It is fully binary compatible with every 3.x release, and fully source-compatible with every 3.3.x release. Note that source compatibility has been broken with 3.2.x in some minor areas. Scalafixes are available and should be automatically applied by Scala Steward if relevant.

User-Facing Pull Requests

• #2844 – Thread local fallback weak bag (@vasilmkd)
• #2838 – Close cancelation leak in fromCompletableFuture (@TimWSpence)
• #2784 – Create and use java.util.ConcurrentThreadLocalRandom on the same flatMap call (@PiotrBosak)
• #2845, #2826, #2796, #2790, #2504 – Documentation fixes and improvements (@armanbilge, @vasilmkd, @Koroeskohr, @djspiewak, @armanbilge)

Thank you so very much!