v4.2.0-RC1

⭐ New Features

• Support the delivery attempt header with CommonDelegatingErrorHandler #4786

🐞 Bug Fixes

• GH-4823: Keep partition pause across child containers #4823
• KafkaAdmin reports topic config alteration failures as 'Failed to obtain topic descriptions' #4820
• ContainerGroupSequencer does not disable autoStartup of containers with an idleEventInterval #4815
• Flaky BatchListenerConversionTests.conversionError() #4809
• AbstractConsumerSeekAware.onPartitionsRevoked() removes other consumers' callbacks #4800
• RoutingKafkaTemplate.partitionsFor() throws UnsupportedOperationException #4796
• KafkaTemplate.receive() returns a record at a different offset when the requested offset is missing #4792
• ReplyingKafkaTemplate reply future times out instead of failing when the send fails #4790
• Share container isInExpectedState() ignores a consumer thread that exited on an error #4788
• Batch nack() after a partial acknowledge commits offsets backwards #4784
• Share consumer ack timeout warning ignores renew() #4782
• DefaultErrorHandler ignores backOffFunction when the default BackOff has no retries #4780
• CommonMixedErrorHandler does not delegate onPartitionsAssigned(), losing records during batch retry #4778
• Deserialization exception headers mapped outbound with Kafka 4.4 clients #4773
• Make ExceptionMatcher cache thread-safe #4756
• ExponentialBackOffWithMaxRetries(0) still retries once #4754
• Mixed and delegating error handlers discard remaining batch records when seekAfterError is false #4752
• AbstractConsumerSeekAware retains callback mappings after unregister #4750
• maxRecoveryFailures skips records in retry topics before they are due #4737
• Retry topics use BackOff.STOP (-1) as a delay when the BackOff has its own limit #4735
• ConcurrentMessageListenerContainer does not report partition pause requests from child containers #4728
• acknowledge() after a partial batch ack commits only the next record #4726
• Retry an immediate ack commit aborted by a pending wakeup #4725
• Cooperative rebalance can leave the partitions a consumer retains permanently unconsumed (async listener) #4708
• Support the two-arg deserialize in DelegatingByTopicDeserializer #4707
• Lambda or method-reference Converter beans break @KafkaListener startup #4591

📔 Documentation

• Fix stale API names in the reference docs #4706

🔨 Dependency Upgrades

• Upgrade micrometer-tracing to 1.8.0-RC1 #4858
• Upgrade micrometer to 1.18.0-RC1 #4857
• Upgrade reactor to 2026.0.0-RC1 #4855
• Upgrade spring-data-bom to 2026.1.0-RC1 #4852
• Upgrade spring-framework to 7.1.0-RC1 #4848
• Bump org.bouncycastle:bcpkix-jdk18on from 1.85 to 1.86 #4838
• Bump gradle-wrapper from 9.8.0 to 9.8.1 #4837
• Bump kotlinVersion from 2.4.20 to 2.4.21 #4836
• Bump com.github.spotbugs:spotbugs-annotations from 4.10.4 to 4.10.5 #4835
• Upgrade to Apache Kafka 4.4.0 #4777
• Bump gradle-wrapper from 9.7.1 to 9.8.0 #4743
• Bump mockitoVersion from 5.23.0 to 5.24.0 #4739
• Bump tools.jackson:jackson-bom from 3.2.2 to 3.2.3 #4720
• Bump org.slf4j:slf4j-api from 2.0.19 to 2.0.20 #4719
• Bump com.fasterxml.jackson:jackson-bom from 2.22.2 to 2.22.3 #4718

❤️ Contributors

Thank you to all the contributors who worked on this release:

@chuuminggg, @kdelay, @ngocnhan-tran1996, and @ohchanKyu