Issues

• Mono.fromFuture cancellation should ignore a wrapped CancellationException

  type/bug
  reactor/reactor-core#4415 · Filter by author chemicL opened on Sep 30, 2026

• concatMap (no prefetch) + Mono.fromCallable emits an item twice and drops the next one when request() arrives from another thread

  reactor/reactor-core#4406 · Filter by author henningandersen opened on Sep 22, 2026

• FluxConcatArray leaves a subscription installed during cancellation uncancelled, losing its element

  reactor/reactor-core#4399 · Filter by author duaneg-tp opened on Sep 21, 2026

• Operators.MultiSubscriptionSubscriber.set can install a subscription into a cancelled arbiter

  reactor/reactor-core#4398 · Filter by author duaneg-tp opened on Sep 21, 2026

• Mono.fromSupplier(...).subscribeOn(...) drops the produced value when cancelled

  reactor/reactor-core#4397 · Filter by author duaneg-tp opened on Sep 21, 2026

• publishOn leaves its prefetch queue undiscarded when a cancel drops the pending drain

  reactor/reactor-core#4396 · Filter by author duaneg-tp opened on Sep 21, 2026

• timeout drops an element that races cancellation instead of discarding it

  reactor/reactor-core#4395 · Filter by author duaneg-tp opened on Sep 21, 2026

• refCount() never disconnects when a subscriber cancels during onSubscribe (regression in 3.8.0)

  reactor/reactor-core#4387 · Filter by author davysteegen opened on Sep 8, 2026

• mergeSequential and flatMapSequential do not discard elements buffered in inner queues

  reactor/reactor-core#4379 · Filter by author hunseonglee opened on Sep 3, 2026

• Mono.sequenceEqual does not discard buffered elements on cancellation, error, or mismatch

  reactor/reactor-core#4378 · Filter by author hunseonglee opened on Sep 3, 2026

• bufferTimeout with fairBackpressure emits a partial buffer when downstream demand resumes

  reactor/reactor-core#4377 · Filter by author hunseonglee opened on Sep 3, 2026

• Outdated FOSS used in reactive-streams-jvm

  type/enhancement
  reactor/reactor-core#4368 · Filter by author hirastogi opened on Aug 27, 2026

• Provide a way for library-internal maintenance tasks to opt out of onSchedule decoration

  type/enhancement
  reactor/reactor-core#4338 · Filter by author hocaron opened on Jul 26, 2026

• MonoSingle propagates empty completion after cancellation

  reactor/reactor-core#4330 · Filter by author EnricSala opened on Jul 20, 2026
  1

• bufferWhile does not discard buffer-triggering element despite what the docs says

  reactor/reactor-core#4316 · Filter by author yawningstudent opened on Jul 8, 2026

• flatMap double-counts produced when onErrorContinue resumes a Callable error

  type/bug
  reactor/reactor-core#4290 · Filter by author chemicL opened on Jun 25, 2026

• FluxRefCount: shared upstream connection not released when subscriber cancels before connection is established

  type/bug
  reactor/reactor-core#4289 · Filter by author chemicL opened on Jun 25, 2026
  1

• JSpecify-annotated BiConsumer of onErrorContinue should allow null as its second argument

  reactor/reactor-core#4285 · Filter by author emthrm opened on Jun 19, 2026

• Hosted Javadoc package-list/package-list returns 404 at projectreactor.io/docs/core/release/api/, breaking downstream -link / Dokka builds

  type/documentation
  reactor/reactor-core#4278 · Filter by author naveenkj-nokia opened on Jun 17, 2026

• Validate historySize in SinkManyReplayProcessor#create(int, boolean)

  type/bug
  reactor/reactor-core#4274 · Filter by author chemicL opened on Jun 9, 2026 · General Backlog

• Validate bufferSize and prefetch in operators

  type/bug
  reactor/reactor-core#4273 · Filter by author chemicL opened on Jun 9, 2026 · General Backlog

• Flux.onBackpressureBuffer should validate maxSize

  type/bug
  reactor/reactor-core#4272 · Filter by author chemicL opened on Jun 9, 2026 · General Backlog
  1

• Document reactor-core-micrometer policy on registered metrics

  type/documentation
  reactor/reactor-core#4271 · Filter by author chemicL opened on Jun 9, 2026 · General Backlog
  1

• Document reactor-core-micrometer name and tag operator use

  type/documentation
  reactor/reactor-core#4270 · Filter by author chemicL opened on Jun 9, 2026 · General Backlog

• Operators.multiplyCap should handle 0 properly

  type/bug
  reactor/reactor-core#4269 · Filter by author chemicL opened on Jun 9, 2026 · General Backlog