Use when you need to design or implement Kafka messaging in Spring Boot — including topic design, producer/consumer implementation, JSON serialization with Boot factory customizers, Testcontainers `@ServiceConnection` integration tests, retries and dead-letter topics, idempotency, and error handling. This should trigger for requests such as Add Kafka in Spring Boot; Review Spring Kafka consumers; Improve retries and DLT in Spring Kafka; Configure Spring Kafka topics serializers or listener conta
NewMaintained
Automatic
◆Coding pack
Last verified 8/20/2026
What it changes
Passed 7 of 21 test cases with the skill, and 14 of 21 without it.
Without skill67%
With skill33%
Checks it passed that the model alone missed
Sets ContainerProperties.AckMode to MANUAL
1 fixed17 passed either way4 still failing3 broke
Pass-rate lift
-33 pp
Tokens
+14%
Agent turns
0%
Response time
-6%
Model gemini-3.6-flashMeasured 8/20/2026v118 of 25 cases passed with skill · 21 comparable
Tokens, turns and time describe resource use, not a dollar price.
See it in action
A test case the skill fixed. Same model, same prompt, with and without the skill.
Prompt
We are configuring a Spring Boot Kafka consumer container where message offset committing must be explicitly controlled by the listener calling Acknowledgment.acknowledge() after business logic completes. Modelers suggested using AckMode.RECORD, but that commits automatically. Which AckMode setting must be configured on the ConcurrentKafkaListenerContainerFactory?
What was checked, without and with the skill
Checked
Without skill
With skill
Sets ContainerProperties.AckMode to MANUAL
Missed
Passed
case-11 · gemini-3.6-flash · 8/20/2026 · answers are capped and redacted
What's inside
The instructions your model reads when the skill loads.
SKILL.md42 lines2 files
Spring Boot — Kafka messaging
Apply Spring Kafka guidance with concrete examples for design, implementation, and error handling.
Constraints
Compile before messaging refactors; verify after changes.
MANDATORY: Run ./mvnw compile or mvn compile before applying any change
SAFETY: If compilation fails, stop immediately
VERIFY: Run ./mvnw clean verify or mvn clean verify after applying improvements
BEFORE APPLYING: Read the reference for detailed rules and examples
When to use this skill
Add Kafka in Spring Boot
Review Spring Kafka consumers/producers
Improve retries, dead-letter topics, or idempotency in Spring Kafka
Configure Spring Kafka topics serializers or listener containers
Add Spring Kafka dead-letter topic handling
Workflow
Read reference and assess project context
Read references/314-frameworks-spring-kafka.md and inspect current messaging setup before proposing changes.
Gather scope and decide target improvements
Identify reliability and throughput goals and define the minimum safe set of changes.
Apply framework-aligned changes
Implement/refactor Spring Kafka configuration, producer/consumer logic, and failure handling.
Run verification and report results
Execute build/tests and summarize what changed, what was verified, and follow-up actions.
Use when you need to write unit tests for Spring Boot applications — including pure unit tests with @ExtendWith(MockitoExtension.class) for @Service/@Component, slice tests with @WebMvcTest and @MockitoBean for controllers, @JsonTest for JSON serialization, parameterized tests with @CsvSource/@MethodSource, test profiles, and @TestConfiguration. For framework-agnostic Java use @131-java-testing-unit-testing. For integration tests use @322-frameworks-spring-boot-testing-integration-tests. This sh