Issues

• Scala 2: subclassing Async fails with 'scalaccompat.annotation.unused is missing from the classpath' since 3.7.0

  typelevel/cats-effect#4693 · Filter by author autopeasant opened on Oct 1, 2026

• IO#syncStep drops uncancelable and onCancel from the returned IO, so Resource release is skipped

  🪲 bug
  Bug

  typelevel/cats-effect#4687 · Filter by author tobiajo opened on Sep 18, 2026
  4

• LocalQueue.enqueueBatch spins forever on a dangling steal tag, and the queue becomes permanently unstealable

  🪲 bug
  Bug

  typelevel/cats-effect#4674 · Filter by author GeorgeFlerovsky opened on Aug 27, 2026
  7

• TracingPlatform performs undefined behavior in JS that makes it unusable in Wasm

  🪲 bug
  Bug

  typelevel/cats-effect#4644 · Filter by author sjrd opened on Jul 26, 2026
  9

• MapAtomicCell

  typelevel/cats-effect#4635 · Filter by author vangogh500 opened on Jul 12, 2026
  1

• Integrated Selector: a ready I/O event can go undelivered for seconds while worker threads sit idle

  🪲 bug
  typelevel/cats-effect#4628 · Filter by author sideeffffect opened on Jun 29, 2026
  19

• Resource.eval extra cancellation point

  🪲 bug
  Bug

  typelevel/cats-effect#4627 · Filter by author durban opened on Jun 28, 2026

• Add Fiber#joinOrCancel

  🍄 enhancement
  typelevel/cats-effect#4620 · Filter by author djspiewak opened on Jun 21, 2026 · v3.8.0
  36

• Converge on a single nomenclature for fiber blocking in docs

  📚 docsgood first issue
  typelevel/cats-effect#4597 · Filter by author LukaJCB opened on May 5, 2026

• Cirrus CI shutdown

  ⚙️ infrastructure
  typelevel/cats-effect#4590 · Filter by author durban opened on Apr 15, 2026
  4

  

• Queue.take.timeout(...) loses elements on cancelation

  🪲 bug
  Bug

  typelevel/cats-effect#4571 · Filter by author TomasMikula opened on Mar 19, 2026
  4

• Flaky DispatcherSpec on JS

  typelevel/cats-effect#4541 · Filter by author djspiewak opened on Dec 30, 2025

• SIGPIPE during tests on scala-native

  🪲 bug
  Bug

  typelevel/cats-effect#4527 · Filter by author durban opened on Nov 23, 2025

• TestContext on scala-native is not threadsafe

  🪲 bug
  Bug

  typelevel/cats-effect#4524 · Filter by author durban opened on Nov 18, 2025 · v3.7.next
  6

• Fork-with-finalizer method on GenSpawn

  🍄 enhancement
  Feature

  typelevel/cats-effect#4517 · Filter by author durban opened on Oct 21, 2025
  2

• OutOfMemoryError not propagated when IO originates from CompletableFuture

  🪲 buggood first issue
  Bug

  typelevel/cats-effect#4505 · Filter by author tpetillot opened on Oct 13, 2025 · v3.7.next
  17

• Queue#mapK violates atomicity guarantees

  🪲 bug
  typelevel/cats-effect#4483 · Filter by author djspiewak opened on Sep 5, 2025
  6

• Scala Native + Windows?

  📚 docs
  typelevel/cats-effect#4473 · Filter by author durban opened on Aug 21, 2025 · v3.7.next
  1

• IOAppSuite failure on JDK 25

  typelevel/cats-effect#4471 · Filter by author SethTisue opened on Aug 17, 2025
  2

• AsyncSuite failure on macos-14

  typelevel/cats-effect#4469 · Filter by author djspiewak opened on Aug 11, 2025

• BoundedAsyncQueue performs poorly on Scala Native

  typelevel/cats-effect#4465 · Filter by author reardonj opened on Aug 3, 2025 · v3.7.next
  2

• Can we implement some flavor of interruptible on Native using signals?

  🍄 enhancement
  Feature

  typelevel/cats-effect#4463 · Filter by author armanbilge opened on Jul 30, 2025
  1

• macOS CI build hung again

  typelevel/cats-effect#4456 · Filter by author djspiewak opened on Jul 23, 2025

• SupervisorSuite timeout on Windows

  typelevel/cats-effect#4445 · Filter by author djspiewak opened on Jul 17, 2025
  6

• Add different effect init for Random/SecureRandom

  typelevel/cats-effect#4410 · Filter by author geny200 opened on May 22, 2025
  4