What is kafka-streams-programming?

A guide for building and troubleshooting Kafka Streams applications. Kafka Streams is a Java or other JVM library for processing data from Kafka topics inside an application.

Use it for KStreams, KTables, data-processing topologies, joins, windows, aggregations, state stores, interactive queries, tests, rebalancing, lag, and deserialization errors.

It helps choose recommendations that match the Kafka environment, since Apache Kafka, Confluent, Confluent Cloud, and WarpStream can differ in versions and security settings.

kafka-streams-programming — Skill for Claude Code by confluentinc

About the project

AI Agent Skills by Confluent is a collection of skills for building Kafka producers, Flink applications, and real-time data-streaming pipelines. Developers use it with coding assistants when creating applications and pipelines on Confluent. The catalogue entries are its skills, plugin, and instruction.

confluentinc/agent-skills · 54 stars · on GitHub

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add confluentinc/agent-skills --skill kafka-streams-programming

Clone the repo

git clone --depth 1 https://github.com/confluentinc/agent-skills

Made for: Claude Code.

Or install streaming-skills-plugin, the plugin that ships this one along with the rest of its 16 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/confluentinc/agent-skills/kafka-streams-programming.svg)](https://agentmods.dev/skills/confluentinc/agent-skills/kafka-streams-programming)

Your own site

<a href="https://agentmods.dev/skills/confluentinc/agent-skills/kafka-streams-programming"><img src="https://agentmods.dev/badge/skills/confluentinc/agent-skills/kafka-streams-programming.svg" alt="Measured on agentmods" height="20"></a>

Per session 113 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 3,732 The whole file, excluding the scripts and references it only reads on demand.

Security scan B 2 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin 98% copy Near-identical to another mod in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00113	$0.03732
Opus 5	$0.00056	$0.01866
Sonnet 5	$0.00023	$0.00746
Haiku 4.5	$0.00011	$0.00373

Measured 7d ago against content hash 5410e6297746, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade B, and why

kafka-streams-programming scanned grade B with 2 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.

The scan reads SKILL.md. This mod also ships 4 executable files (scripts/create-topics.sh, scripts/produce-test-data.sh, scripts/teardown.sh, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Strips warnings and disclaimersmediumAnti-refusal

Omitting safety caveats hides risk from the user and is a common jailbreak preamble.

If user asks for generic stream processing on CC without mentioning KS, briefly offer Flink as alternative. Don't lecture.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

1. `docker compose up -d` and wait for Kafka + SR to be healthy (`docker compose ps`, or curl SR `/subjects`)

Origin

This is a copy

98% identical to kafka-streams-programming — 17 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/kafka-streams-programming/SKILL.md · 212 lines

How it starts

The opening of the file, as written. The whole thing — 212 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Kafka Streams — Architect, Build, Debug

JVM-embedded stream processing library with no separate cluster.

⚠️ IMPORTANT: Lazy-Load References Only

Do NOT read all reference files upfront. Read ONLY what you need, when you need it.

User asks "how do I join two topics?" → Read references/topology-patterns.md § Joins Decision Tree only
User asks "build me a Kafka Streams app" → Read references/build-templates.md when writing build files, not before
User asks "my app is crashing" → Read the specific section in references/debugging.md for that symptom
Most questions need 0-2 reference files total, not all 10

Never read multiple files preemptively "just in case"

Always Confirm Target Environment First

Before answering in any mode (Architect, Build, Debug), confirm the target environment if the user hasn't stated it: Apache Kafka | Confluent Platform | Confluent Cloud | WarpStream. Versions/auth shape every recommendation — KIP-1071 support, SASL config, ACL model, transactional-id expiry, CLI tool names all branch on this. Skip the question only if the user already named the environment.

If the user selects WarpStream: Read references/warpstream-optimization.md and apply its overrides on top of the standard config baseline. Key impacts for Kafka Streams:

EOS has a significant throughput cost — exactly_once_v2 enables idempotent producers internally, which reduces throughput on WarpStream due to limited in-flight request concurrency. Default to at_least_once with downstream deduplication unless the user has a strong need for EOS.
Producer and consumer configs must be overridden (larger batches, higher linger, larger fetches). See the "Kafka Streams Specific" section in the shared reference.
fetch.min.bytes is not supported — do not set it.
replication.factor is cosmetic (always 3) — do not tune it.
Zone-aware routing via client.id with ws_az=<az> suffix is critical for cost.
Latency is higher (~250ms p50 produce vs single-digit ms on Kafka) — set expectations with the user.

Read the full file on GitHub · 212 lines

Files

What ships with it

16 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

7d ago First seen · 212 lines · 113 tokens per session scan B 5410e6297746

Subscribe to this mod's changes

kafka-streams-programming is a skill published in the GitHub repository confluentinc/agent-skills (54 stars, last pushed 3d ago), licensed Apache-2.0. It adds 113 tokens to every session and 3,732 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it B with 2 findings (strips warnings and disclaimers, makes network calls). It is 98% identical to kafka-streams-programming, differing in 17 lines, and is treated as a copy.

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