typelevel/fs2

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Compositional, streaming I/O library for Scala

Stars: 2.5k
Forks: 636
Open beginner issues: 0
Indexed issues: 103
Avg merge: 2d 4h
Merged PRs (30d): 7

Dominant language: Scala
License: No license data
Last GitHub push: Sep 8, 2026
Latest indexed: Sep 19, 2026
Contributing guide: Contributing guide
Code of conduct: Code of conduct
Beginner labels: help wanted good first issue

Beginner friendly Everything

Open All

103 open issues indexed

fs2-io is not closing ports when a DatagramChannel is used Open

bug

Difficulty 3/5 1-2 days Newbie friendliness 58/100

typelevel/fs2#3762 · 2 comments · Opened Sep 3, 2026
TCP connection pool design advice Open

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

typelevel/fs2#3719 · 2 comments · Opened May 1, 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
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
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
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
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
`.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
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
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
Emit a last stream on cancel Open

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

typelevel/fs2#3636 · Opened Nov 14, 2025
Create another version of groupWithin() which won't create a singleton chunk when elements are available in bulk after being idle for a long time Open

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

typelevel/fs2#3608 · Opened Sep 12, 2025
Unexpected behavior of onFinalize behavior Open

bug

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

typelevel/fs2#3607 · 4 comments · 1 reaction · Opened Sep 9, 2025
Add support for QUIC to fs2.io.net Open

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

typelevel/fs2#3605 · 3 reactions · Opened Sep 6, 2025
Test http4s servers fail release bound port on shutdown when using fs2 3.12.0 Open

bug

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

typelevel/fs2#3590 · 5 comments · Opened Aug 21, 2025
hold1 + concurrently releases bracket immediately Open

bug

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

typelevel/fs2#3567 · Opened May 7, 2025
`fs2.interop.flow.PublisherToSubscriberSpec.should cancel upstream if downstream completes` flake Open

bug

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

typelevel/fs2#3542 · 2 comments · Opened Mar 7, 2025
`fs2.interop.flow.PublisherToSubscriberSpec.should have the same output as input` timeout Open

bug

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

typelevel/fs2#3541 · Opened Mar 7, 2025
fs2 gunzip doesn't support concatenated gzip files Open

bug

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

typelevel/fs2#3503 · Opened Nov 19, 2024
Stream hangs on error with broadcastThrough and readOutputStream Open

bug

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

typelevel/fs2#3502 · Opened Nov 19, 2024
parEvalMap resets stream cancellation Open

bug

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

typelevel/fs2#3487 · 1 comment · Opened Oct 1, 2024
parEvalMap and it's variations hang on canceled effect Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 32/100

typelevel/fs2#3486 · 1 comment · Opened Oct 1, 2024
prefetch hangs on a canceled stream Open

bug

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

typelevel/fs2#3485 · 2 comments · Opened Oct 1, 2024
`Pull`'s public api is unsound Open

bug

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

typelevel/fs2#3484 · 1 comment · Opened Sep 28, 2024
zip + uncons + concurrency = scope lookup failure Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 32/100

typelevel/fs2#3478 · 4 comments · Opened Sep 23, 2024
`groupWithin` prematurely closes resources Open

bug

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

typelevel/fs2#3477 · 5 comments · Opened Sep 20, 2024
`Pull#lease`, `Pull.bracketCase` and `Pull.extendScopeTo` are not cancellation safe. Open

bug

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

typelevel/fs2#3474 · 1 reaction · Opened Sep 13, 2024
`fs2.io.Watcher#watch` with a relative path to file causes an NPE Open

bug

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

typelevel/fs2#3472 · 2 comments · Opened Sep 8, 2024
Exception in spawned stream cancels Stream.never but swallows the exception Open

bug

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

typelevel/fs2#3469 · Opened Aug 30, 2024
Premature resource finalization in `Stream.bracket` Open

bug

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

typelevel/fs2#3461 · 3 comments · Opened Aug 8, 2024
`microsite / tlSitePreview` does not show the static website correctly Open

bug

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

typelevel/fs2#3433 · 2 comments · Opened May 14, 2024
Introduce higher-level "network client" APIs Open

feature

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

typelevel/fs2#3419 · 1 comment · 18 reactions · Opened Apr 1, 2024
DatagramSocket read stalls on JVM Open

bug

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

typelevel/fs2#3406 · 2 comments · Opened Mar 5, 2024
failed: fs2.io.net.udp.UdpSuite.udp Open

bug

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

typelevel/fs2#3376 · 1 comment · Opened Jan 18, 2024
Optimize `Stream#evalTapChunk` Open

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

typelevel/fs2#3351 · Opened Nov 29, 2023
Feature request: Dynamic metering of Streams Open

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

typelevel/fs2#3328 · 3 comments · 1 reaction · Opened Nov 1, 2023
parEvalMap messes up unmasking of cancellation Open

bug

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

typelevel/fs2#3311 · Opened Sep 25, 2023
Reactive-streams interop is uncancelable Open

bug

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

typelevel/fs2#3260 · 3 comments · Opened Jul 17, 2023
`fs2.io.readOutputStream` doesn't preserve errors from `cats.data.EitherT` Open

bug

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

typelevel/fs2#3246 · 3 comments · Opened Jun 27, 2023
`interruptWhen` and friends shouldn't cancel downstream processing Open

bug

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

typelevel/fs2#3202 · 7 comments · 2 reactions · Opened Apr 7, 2023
parEvalMap deadlocks when Stream's `F` has extra error channels Open

3.x bug

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

typelevel/fs2#3199 · 3 comments · 1 reaction · Opened Apr 4, 2023
Non-blocking backend for `Process` APIs Open

feature good first issue

typelevel/fs2#3182 · 12 comments · 1 assignee · Opened Mar 24, 2023
Support reading from `ReadCursor` / writing to `WriteCursor` via `Socket` Open

feature

typelevel/fs2#3171 · 2 comments · 1 assignee · Opened Mar 22, 2023
API to directly open TLS connections, instead of upgrading an existing socket Open

feature

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

typelevel/fs2#3138 · 3 comments · Opened Feb 12, 2023
evalFilterNotAsync test flaky Open

bug

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

typelevel/fs2#3133 · Opened Feb 8, 2023
`uncons` and `concurrently` are not friends Open

bug

Difficulty 4/5 3-5 days Newbie friendliness 30/100

typelevel/fs2#3123 · Opened Feb 4, 2023
Unexpected interaction of `Pull.bracketCase` and `Stream`'s `flatMap` Open

bug

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

typelevel/fs2#3118 · Opened Jan 29, 2023
Inserting a map stops propagation of IOLocal Open

bug

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

typelevel/fs2#3103 · 1 comment · Opened Jan 9, 2023

typelevel/fs2

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