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typelevel

51 indexed repositories · View on GitHub

cats
Lightweight, modular, and extensible library for functional programming.

Scala · 5465 stars
fs2
Compositional, streaming I/O library for Scala

Scala · 2453 stars
cats-effect
The pure asynchronous runtime for Scala

Scala · 2236 stars
doobie
Functional JDBC layer for Scala.

Scala · 2225 stars
scalacheck
Property-based testing for Scala

Scala · 1964 stars
skunk
A data access library for Scala + Postgres.

Scala · 1667 stars
kind-projector
Compiler plugin for making type lambdas (type projections) easier to write

Scala · 923 stars
frameless
Expressive types for Spark.

Scala · 895 stars
cats-collections
Data structures for pure functional programming in Scala

Scala · 563 stars
kittens
Automatic type class derivation for Cats

Scala · 545 stars
jawn
Jawn is for parsing jay-sawn (JSON)

Scala · 436 stars
log4cats
Logging Tools For Interaction with cats-effect

Scala · 416 stars
sbt-tpolecat
scalac options for the enlightened

Scala · 410 stars
mouse
A small companion to cats

Scala · 376 stars
natchez
functional tracing for cats

Scala · 340 stars
cats-tagless
Library of utilities for tagless final encoded algebras

Scala · 320 stars
fs2-kafka
Functional Kafka Streams for Scala

Scala · 314 stars
cats-mtl
cats transformer type classes.

Scala · 307 stars
fs2-grpc
gRPC implementation for FS2/cats-effect

Scala · 284 stars
cats-parse
A parsing library for the cats ecosystem

Scala · 245 stars
31 more repositories live on View on GitHub

Beginner friendly Everything

Open All

To-do list for 1.0 release? Open

Difficulty 5/5 Over a week Newbie friendliness 30/100

typelevel/toolkit#320 · 2 comments · Opened Apr 17, 2026
Cirrus CI shutdown Open

:gear: infrastructure

typelevel/cats-effect#4590 · 4 comments · 1 assignee · Opened Apr 15, 2026
Feature request: display failed test names under each suite in the summary Open

Difficulty 3/5 1-2 days Newbie friendliness 65/100

typelevel/weaver-test#302 · 3 comments · Opened Apr 14, 2026
Policy against using Copilot integrations on GitHub Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

typelevel/tsc#183 · 8 comments · 1 reaction · Opened Mar 30, 2026
OpenJDK 23 was removed as it has reached its end of life Open

Difficulty 2/5 1-3 hours Newbie friendliness 54/100

typelevel/typelevel-nix#267 · 1 comment · Opened Mar 27, 2026
Release mode does not include inline related optimizer options Open

Difficulty 2/5 1-3 hours Newbie friendliness 72/100

typelevel/sbt-tpolecat#299 · Opened Mar 25, 2026
Make chunk sizes configurable for ProcessBuilder Open

Difficulty 3/5 1-2 days Newbie friendliness 55/100

typelevel/fs2#3701 · Opened Mar 19, 2026
Queue.take.timeout(...) loses elements on cancelation Open

:beetle: bug

Difficulty 4/5 3-5 days Newbie friendliness 48/100

typelevel/cats-effect#4571 · 4 comments · Opened Mar 19, 2026
Stream.merge hangs when one branch is empty + repeat, unresponsive to interruptAfter and IO.cancel Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 55/100

typelevel/fs2#3697 · 1 comment · Opened Mar 16, 2026
Models for AWS Lambda Event Types Open

Difficulty 3/5 1-2 days Newbie friendliness 42/100

typelevel/feral#641 · 1 comment · Opened Mar 12, 2026
Process[IO] that spawns child processes might not respect cancellation Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 35/100

typelevel/fs2#3693 · 1 comment · Opened Mar 10, 2026
`Applicative[OneAnd[ZipLazyList, *]]` works incorrectly Open

Difficulty 5/5 Over a week Newbie friendliness 30/100

typelevel/cats#4840 · Opened Mar 8, 2026
issue: Duplicate path error during build Open

Difficulty 3/5 1-2 days Newbie friendliness 48/100

typelevel/typelevel.github.com#610 · 4 comments · Opened Mar 4, 2026
Rendering of the 404 page is broken Open

Difficulty 3/5 1-2 days Newbie friendliness 42/100

typelevel/typelevel.github.com#602 · 4 comments · Opened Feb 24, 2026
could we upgrade code and the version to support set 2.0.0 rc9 Open

Difficulty 3/5 1-2 days Newbie friendliness 30/100

typelevel/sbt-typelevel#870 · Opened Feb 24, 2026
Make `Hash.fromUniversalHashCode` null safe Open

good first issue

typelevel/cats#4831 · 6 comments · 1 reaction · 1 assignee · Opened Feb 22, 2026
Typeclass instances for `ZipLazyList` and `ZipStream` seem to be unlawful Open

typelevel/cats#4830 · 12 comments · 1 assignee · Opened Feb 22, 2026
Docs: add logs example to the testkit guide Open

documentation good first issue help wanted

Difficulty 2/5 1-3 hours Newbie friendliness 45/100

typelevel/otel4s-sdk#42 · 2 comments · Opened Feb 21, 2026
Extensible Process Control API (pid and Signals) Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

typelevel/fs2#3682 · Opened Feb 20, 2026
Pos contains an absolute path Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

typelevel/doobie#2380 · 2 comments · Opened Feb 20, 2026
Start Contributing Guide pages Open

typelevel/typelevel.github.com#590 · 3 comments · 2 reactions · 1 assignee · Opened Feb 19, 2026
Index HOCON config data in search Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

typelevel/typelevel.github.com#589 · Opened Feb 19, 2026
Consider migrating to http4s-grpc Open

Difficulty 5/5 Over a week Newbie friendliness 15/100

typelevel/otel4s-sdk#39 · Opened Feb 18, 2026
A Nullable type for scala3 Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

typelevel/cats#4822 · 12 comments · Opened Feb 15, 2026
Unexpected behavior of `NonEmptyList.reduce` for tuples of lists Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

typelevel/cats#4817 · 1 comment · Opened Jan 31, 2026
Files[IO].writeAll creates file when it shouldn't Open

bug

Difficulty 3/5 1-2 days Newbie friendliness 48/100

typelevel/fs2#3667 · 1 comment · Opened Jan 19, 2026
Project Submission: Number Open

projects

Difficulty 5/5 Over a week Newbie friendliness 20/100

typelevel/tsc#179 · Opened Jan 19, 2026
"unspecified error" when Handle.allow refers to a local singleton object Open

Difficulty 4/5 3-5 days Newbie friendliness 42/100

typelevel/cats-mtl#676 · Opened Jan 12, 2026
`.conflateChunks` does not respect the provided chunk limit Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 38/100

typelevel/fs2#3661 · 2 comments · Opened Jan 12, 2026
catsSyntaxEq returns false for equality of positive and negative zero in Option Open

Difficulty 3/5 1-2 days Newbie friendliness 48/100

typelevel/cats#4807 · 4 comments · Opened Jan 8, 2026
3.13.0-M8 Stream.pauseWhen changed behavior when using mergeHaltL Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

typelevel/fs2#3655 · 4 comments · Opened Jan 7, 2026
Get access to the socket file descriptor or generalise getOption to gain access to SO_ORIGINAL_DST in scala native Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 45/100

typelevel/fs2#3653 · 2 comments · Opened Jan 2, 2026
Flaky `DispatcherSpec` on JS Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

typelevel/cats-effect#4541 · Opened Dec 30, 2025
Logo image is rendered incorrectly by Laika Open

Difficulty 1/5 Under an hour Newbie friendliness 48/100

typelevel/cats-mtl#671 · 1 comment · Opened Dec 22, 2025
UnorderedTraverse should extend Functor Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

typelevel/cats#4802 · 4 comments · Opened Dec 20, 2025
OpenTelemetry Semantic Conventions Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

typelevel/natchez-http4s#147 · Opened Dec 17, 2025
Lint for the list monoid Open

Difficulty 4/5 3-5 days Newbie friendliness 38/100

typelevel/typelevel-scalafix#252 · 1 reaction · Opened Dec 16, 2025
Investigate / refresh the `clean` workflow. Open

good first issue

Difficulty 4/5 3-5 days Newbie friendliness 35/100

typelevel/sbt-typelevel#856 · 1 comment · Opened Dec 13, 2025
Logs: support minimum severity Open

logs specification

Difficulty 4/5 3-5 days Newbie friendliness 25/100

typelevel/otel4s-sdk#47 · Opened Dec 12, 2025
Remove or filter weaver log levels Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

typelevel/weaver-test#262 · 2 comments · Opened Dec 10, 2025
Topic subscribers observe different order of messages on concurrent publishers Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 35/100

typelevel/fs2#3646 · Opened Dec 9, 2025
The return value of Topic#publish1 is lying when there's a race condition with Topic closure Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 45/100

typelevel/fs2#3644 · Opened Dec 9, 2025
Add commonly known operators to algebra type classes Open

Difficulty 5/5 Over a week Newbie friendliness 30/100

typelevel/cats#4795 · 6 comments · Opened Nov 25, 2025
SIGPIPE during tests on scala-native Open

:beetle: bug

Difficulty 4/5 3-5 days Newbie friendliness 35/100

typelevel/cats-effect#4527 · Opened Nov 23, 2025
`Raises` and `Handles` aliases on Scala 3? Open

Difficulty 5/5 Over a week Newbie friendliness 25/100

typelevel/cats-mtl#666 · 1 comment · Opened Nov 21, 2025
Set default Java version to 17 if scalaVersion is 3.8.0 or higher Open

Difficulty 3/5 1-2 days Newbie friendliness 35/100

typelevel/sbt-typelevel#851 · 3 comments · 1 reaction · Opened Nov 19, 2025
`TestContext` on scala-native is not threadsafe Open

:beetle: bug

Difficulty 3/5 1-2 days Newbie friendliness 48/100

typelevel/cats-effect#4524 · 6 comments · Opened Nov 18, 2025
Emit a last stream on cancel Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

typelevel/fs2#3636 · Opened Nov 14, 2025
Named version of `mapN` and friends Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

typelevel/cats#4792 · 1 reaction · Opened Nov 14, 2025
Failed test on hash.antisymmetry Open

Difficulty 3/5 1-2 days Newbie friendliness 35/100

typelevel/case-insensitive#513 · Opened Nov 13, 2025

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