# Build your first Agent

Build a durable Agent from Constal’s seven primitives, then package, deploy, and invoke it.

Every Constal Agent is composed from `turn`, `ledger`, `commit`, `await`, `spawn`, `map`, and `reduce`. This first Agent introduces `turn`; the runtime commits the returned result as durable truth. Add `ledger` when prior history should shape the next decision. [Learn the Agent language](/docs/foundations/seven-primitives), or choose a production shape from the [Agent patterns catalog](/docs/agents/patterns).

## 1\. Create the Agent

```bash
npm install @constal/sdk
```

```typescript
import { agent } from "@constal/sdk";

export default agent({
  id: "helpful-assistant",
  version: "1.0.0",
  model: "model",
  async onMessage(message, ctx) {
    const turn = await ctx.turn({
      system: "Resolve the request accurately and concisely.",
      objective: message,
    });
    return turn.message.content;
  },
});
```

Commit the generated dependency lockfile and add a `constal.agent.json` manifest whose entry points to this file. Archives contain one manifest, `package.json`, the lockfile, and source; lifecycle scripts and development dependencies are rejected.

## 2\. Upload an immutable deployment

```bash
zip -r agent.zip constal.agent.json package.json src
curl https://platform.constal.ai/v1/deployments \
  -H "Authorization: Bearer $CONSTAL_DEPLOYMENT_KEY" \
  -H "Idempotency-Key: helpful-assistant-1.0.0" \
  -H "Content-Type: application/zip" --data-binary @agent.zip
```

Poll `GET /v1/deployments/:id`. A successful build publishes a pinned executable artifact and immutable deployment revision.

## 3\. Dispatch an event

```bash
curl https://platform.constal.ai/v1/events \
 -H "Authorization: Bearer $CONSTAL_API_KEY" \
 -H "Content-Type: application/json" --data '{
 "v":1,"id":"message-1","type":"message",
 "target":"crn:constal:production:default:default:agent/helpful-assistant",
 "session":"first-session","data":{"message":"Hello"}}'
```

The dispatcher supplies the source Channel. Callers cannot assert source identity in the event body.