Manage Sessions

Sandbox Agent stores sessions in memory only. When the server restarts or the sandbox is destroyed, all session data is lost. It’s your responsibility to persist events to your own database.

Recommended approach

1. Store events to your database as they arrive
2. On reconnect, get the last event’s sequence and pass it as offset
3. The API returns events where sequence > offset

This prevents duplicate writes and lets you recover from disconnects.

Receiving Events

Two ways to receive events: streaming (recommended) or polling.

Streaming

Use streaming for real-time events with automatic reconnection support.

import { SandboxAgentClient } from "sandbox-agent";

const client = new SandboxAgentClient({
  baseUrl: "http://127.0.0.1:2468",
  agent: "mock",
});

// Get offset from last stored event (0 returns all events)
const lastEvent = await db.getLastEvent("my-session");
const offset = lastEvent?.sequence ?? 0;

// Stream from where you left off
for await (const event of client.streamEvents("my-session", { offset })) {
  await db.insertEvent("my-session", event);
}

Polling

If you can’t use streaming, poll the events endpoint:

const lastEvent = await db.getLastEvent("my-session");
let offset = lastEvent?.sequence ?? 0;

while (true) {
  const { events } = await client.getEvents("my-session", {
    offset,
    limit: 100
  });

  for (const event of events) {
    await db.insertEvent("my-session", event);
    offset = event.sequence;
  }

  await sleep(1000);
}

Database options

Choose where to persist events based on your requirements. For most use cases, we recommend Rivet Actors.

	Durable	Real-time	Multiplayer	Scaling	Throughput	Complexity
Rivet Actors	✓	✓	✓	Auto-sharded, one actor per session	Millions of concurrent sessions	Zero infrastructure
PostgreSQL	✓			Manual sharding	Connection pool limited	Connection pools, migrations
Redis		✓		Redis Cluster	High, in-memory	Memory management, Sentinel for failover

Rivet Actors

For production workloads, Rivet Actors provide a managed solution for:

• Persistent state: Events survive crashes and restarts
• Real-time streaming: Built-in WebSocket support for clients
• Horizontal scaling: Run thousands of concurrent sessions
• Observability: Built-in logging and metrics

Actor

import { actor } from "rivetkit";
import { Daytona } from "@daytonaio/sdk";
import { SandboxAgent, SandboxAgentClient, AgentEvent } from "sandbox-agent";

interface CodingSessionState {
  sandboxId: string;
  baseUrl: string;
  sessionId: string;
  events: AgentEvent[];
}

interface CodingSessionVars {
  client: SandboxAgentClient;
}

const daytona = new Daytona();

const codingSession = actor({
  createState: async (): Promise<CodingSessionState> => {
    const sandbox = await daytona.create({
      snapshot: "sandbox-agent-ready",
      envVars: {
        ANTHROPIC_API_KEY: process.env.ANTHROPIC_API_KEY,
        OPENAI_API_KEY: process.env.OPENAI_API_KEY,
      },
      autoStopInterval: 0,
    });

    await sandbox.process.executeCommand(
      "nohup sandbox-agent server --no-token --host 0.0.0.0 --port 3000 &"
    );

    const baseUrl = (await sandbox.getSignedPreviewUrl(3000)).url;
    const sessionId = crypto.randomUUID();

    return {
      sandboxId: sandbox.id,
      baseUrl,
      sessionId,
      events: [],
    };
  },

  createVars: async (c): Promise<CodingSessionVars> => {
    const client = new SandboxAgentClient({
  baseUrl: c.state.baseUrl,
  agent: "mock",
});
    await client.createSession(c.state.sessionId, { agent: "claude" });
    return { client };
  },

  onDestroy: async (c) => {
    const sandbox = await daytona.get(c.state.sandboxId);
    await sandbox.delete();
  },

  run: async (c) => {
    for await (const event of c.vars.client.streamEvents(c.state.sessionId)) {
      c.state.events.push(event);
      c.broadcast("agentEvent", event);
    }
  },

  actions: {
    postMessage: async (c, message: string) => {
      await c.vars.client.postMessage(c.state.sessionId, message);
    },

    getTranscript: (c) => c.state.events,
  },
});

Client

TypeScript

import { createClient } from "rivetkit/client";

const client = createClient();
const session = client.codingSession.getOrCreate(["my-session"]);

const conn = session.connect();
conn.on("agentEvent", (event) => {
  console.log(event.type, event.data);
});

await conn.postMessage("Create a new React component for user profiles");

const transcript = await conn.getTranscript();

React

import { createRivetKit } from "@rivetkit/react";

const { useActor } = createRivetKit();

function CodingSession() {
  const [messages, setMessages] = useState<AgentEvent[]>([]);
  const session = useActor({ name: "codingSession", key: ["my-session"] });

  session.useEvent("agentEvent", (event) => {
    setMessages((prev) => [...prev, event]);
  });

  const sendPrompt = async (prompt: string) => {
    await session.connection?.postMessage(prompt);
  };

  return (
    <div>
      {messages.map((msg, i) => (
        <div key={i}>{JSON.stringify(msg)}</div>
      ))}
      <button onClick={() => sendPrompt("Build a login page")}>
        Send Prompt
      </button>
    </div>
  );
}

PostgreSQL

CREATE TABLE agent_events (
  event_id TEXT PRIMARY KEY,
  session_id TEXT NOT NULL,
  native_session_id TEXT,
  sequence INTEGER NOT NULL,
  time TIMESTAMPTZ NOT NULL,
  type TEXT NOT NULL,
  source TEXT NOT NULL,
  synthetic BOOLEAN NOT NULL DEFAULT FALSE,
  data JSONB NOT NULL,
  UNIQUE(session_id, sequence)
);

CREATE INDEX idx_events_session ON agent_events(session_id, sequence);

Redis

// Append event to list
await redis.rpush(`session:${sessionId}`, JSON.stringify(event));

// Get events from offset
const events = await redis.lrange(`session:${sessionId}`, offset, -1);

Handling disconnects

The event stream may disconnect due to network issues. Handle reconnection gracefully:

async function streamWithRetry(sessionId: string) {
  while (true) {
    try {
      const lastEvent = await db.getLastEvent(sessionId);
      const offset = lastEvent?.sequence ?? 0;

      for await (const event of client.streamEvents(sessionId, { offset })) {
        await db.insertEvent(sessionId, event);
      }
    } catch (error) {
      console.error("Stream disconnected, reconnecting...", error);
      await sleep(1000);
    }
  }
}