loom-event-driven

loom-event-driven is a skill for Claude Code, Codex from cosmix/loom. It costs 25 tokens per session (8,234 once invoked), scanned A, original, MIT.

Architecture guidance for software whose parts communicate through events, such as messages that announce something happened. It covers queues, publish-subscribe systems, event sourcing, CQRS, sagas, and streaming tools such as Kafka or RabbitMQ.

In plain words
What is it for?
Use it when designing asynchronous services, message consumers, event stores, data streams, distributed transactions, delivery guarantees, or changing event formats.
Why use it?
It helps avoid failures caused by duplicate delivery, incorrect ordering, unreliable networks, and distributed operations that do not complete together.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/cosmix/loom/loom-event-driven
Any agent
npx skills add cosmix/loom --skill loom-event-driven
Clone the repo
git clone --depth 1 https://github.com/cosmix/loom

Made for: Claude Code, Codex.

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.

agentmods badge for loom-event-driven

README.md
[![agentmods](https://agentmods.dev/badge/skills/cosmix/loom/loom-event-driven.svg)](https://agentmods.dev/skills/cosmix/loom/loom-event-driven)
Your own site
<a href="https://agentmods.dev/skills/cosmix/loom/loom-event-driven"><img src="https://agentmods.dev/badge/skills/cosmix/loom/loom-event-driven.svg" alt="Measured on agentmods" height="20"></a>
Per session 25 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 8,234 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found 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.

ModelPer sessionOnce invoked
Fable 5 $0.00025 $0.08234
Opus 5 $0.00013 $0.04117
Sonnet 5 $0.00005 $0.01647
Haiku 4.5 $0.00003 $0.00823

Measured yesterday against content hash 561ac6804eb2, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

loom-event-driven scanned grade A with 0 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 yesterday.

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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/loom-event-driven/SKILL.md · 537 lines

How it starts

The opening of the file, as written. The whole thing — 537 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Event-Driven Architecture

Overview

Patterns for decoupling services via events instead of synchronous calls: message queues, pub/sub, event sourcing, CQRS, sagas, and streaming. Scope of THIS skill = the architecture and its distributed-systems traps (delivery semantics, ordering, outbox, schema evolution). For job-queue mechanics — worker pools, scheduling/cron, retry/backoff internals, generic DLQ plumbing — see loom-background-jobs; cross-reference rather than duplicate.

The one law that governs everything below: networked delivery is at-least-once; therefore every consumer must be idempotent. Read the Delivery Semantics section first — most EDA bugs are a violation of it.

Code samples are TypeScript for concreteness; the patterns are language-agnostic. Assume crypto.randomUUID(), a broker client, and a datastore are in scope.


Delivery Semantics — "Exactly-once" Is (Mostly) a Lie

Two-Generals: across an unreliable network you cannot guarantee a message is delivered exactly once. You get to pick a failure mode:

Semantic Mechanism Failure mode Use when
At-most-once fire-and-forget, ack before processing loses messages on crash metrics/telemetry where loss is OK
At-least-once ack after processing, redeliver on no-ack duplicates on retry/redelivery default for everything that matters
"Exactly-once" at-least-once transport + idempotent consumer + dedup none observable any state-changing handler

Exactly-once is an effect you engineer at the consumer, not a transport guarantee you buy. The real recipe:

  1. At-least-once delivery (durable broker, ack after commit).
  2. Idempotent consumer: processing the same message twice == processing it once.
  3. A dedup/idempotency store keyed by a stable message id or business key.

⚠️ Kafka "exactly-once semantics (EOS)" is real but scoped to Kafka. Idempotent producer + transactions give exactly-once for read-topic → process → write-topic-and-offsets inside Kafka. It does not cover external side effects — a DB write, an email, a charge. The moment a handler touches the outside world, you are back to at-least-once and must be idempotent. Never tell a stakeholder Kafka gives you exactly-once for a payment.

Read the full file on GitHub · 537 lines

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.

  1. yesterday Changed · -47 tokens per session 561ac6804eb2
  2. 5d ago First seen · 537 lines · 72 tokens per session scan A dec2fecdd8d7

Subscribe to this mod's changes

loom-event-driven is a skill published in the GitHub repository cosmix/loom (54 stars, last pushed yesterday), licensed MIT. It adds 25 tokens to every session and 8,234 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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