# Encore Pubsub

> Asynchronous messaging in Encore.ts via `Topic` and `Subscription` from `encore.dev/pubsub` — broadcast events, decouple producers from consumers, and run background handlers.

- **Type:** Skill
- **Install:** `agentstack add skill-encoredev-skills-pubsub`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [encoredev](https://agentstack.voostack.com/s/encoredev)
- **Installs:** 0
- **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills)
- **Latest version:** 0.1.0
- **License:** Apache-2.0
- **Upstream author:** [encoredev](https://github.com/encoredev)
- **Source:** https://github.com/encoredev/skills/tree/main/encore/pubsub
- **Website:** https://encore.dev

## Install

```sh
agentstack add skill-encoredev-skills-pubsub
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# Encore Pub/Sub

## Instructions

Pub/Sub is for asynchronous messaging between services. Producers publish events to a `Topic`; consumers attach `Subscription`s to react. Resources must be declared at package level — never inside functions.

## Topics

```typescript
import { Topic } from "encore.dev/pubsub";

interface OrderCreatedEvent {
  orderId: string;
  userId: string;
  total: number;
}

// Package level declaration
export const orderCreated = new Topic("order-created", {
  deliveryGuarantee: "at-least-once",
});
```

### Publishing

```typescript
await orderCreated.publish({
  orderId: "123",
  userId: "user-456",
  total: 99.99,
});
```

### Subscriptions

```typescript
import { Subscription } from "encore.dev/pubsub";

const _ = new Subscription(orderCreated, "send-confirmation-email", {
  handler: async (event) => {
    await sendEmail(event.userId, event.orderId);
  },
});
```

### Message Attributes

Use `Attribute` for fields that should be treated as message attributes (for filtering/ordering):

```typescript
import { Topic, Attribute } from "encore.dev/pubsub";

interface CartEvent {
  cartId: Attribute;  // Used for ordering
  userId: string;
  action: "add" | "remove";
  productId: string;
}

// Ordered topic: events with same cartId delivered in order
export const cartEvents = new Topic("cart-events", {
  deliveryGuarantee: "at-least-once",
  orderingAttribute: "cartId",
});
```

### Topic References

Pass topic access to other code while maintaining static analysis:

```typescript
import { Publisher } from "encore.dev/pubsub";

const publisherRef = orderCreated.ref();

async function notifyOrder(ref: typeof publisherRef, orderId: string) {
  await ref.publish({ orderId, userId: "123", total: 99.99 });
}
```

## Delivery Guarantees

- `at-least-once` (default): may deliver duplicates → handlers must be idempotent.
- `exactly-once`: stricter, capped throughput (AWS 300 msg/s/topic, GCP 3000+ msg/s/region). Does not deduplicate on the publish side.

## Guidelines

- Topics and subscriptions must be declared at package level.
- Subscription handlers must be idempotent (at-least-once delivery is the default).
- Use `Attribute` for fields meant for filtering/ordering, not for arbitrary metadata.
- Don't do heavy synchronous work in `publish` callers — `publish` returns once the message is queued.

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [encoredev](https://github.com/encoredev)
- **Source:** [encoredev/skills](https://github.com/encoredev/skills)
- **License:** Apache-2.0
- **Homepage:** https://encore.dev

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-encoredev-skills-pubsub
- Seller: https://agentstack.voostack.com/s/encoredev
- Browse the marketplace: https://agentstack.voostack.com/browse

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