Burst Sandboxes

Burst Sandboxes are in alpha. They preserve filesystem state across infrastructure restarts, but running processes, in-memory state, terminal sessions, and open network connections may restart.

Burst Sandboxes are lower-cost OpenComputer sandboxes designed for workloads that can recover from a process restart. They expose the same OpenComputer API for commands, files, PTY, preview URLs, images, snapshots, scaling, and lifecycle operations. If OpenComputer receives advance infrastructure interruption notice, the sandbox gets up to 25 seconds to flush state before it restarts on healthy capacity. The sandbox’s filesystem is preserved and made available after resume.

Pricing

Burst Sandboxes are priced roughly 2x cheaper than on-demand sandboxes.

Create a Burst Sandbox

Set burst: true when creating the sandbox.

import { Sandbox } from "@opencomputer/sdk";

const sandbox = await Sandbox.create({
  burst: true,
  memoryMB: 4096,
  timeout: 300,
});

const result = await sandbox.exec.run("echo hello from burst");
console.log(result.stdout);

await sandbox.kill();

from opencomputer import Sandbox

async with await Sandbox.create(
    burst=True,
    memory_mb=4096,
    timeout=300,
) as sandbox:
    result = await sandbox.exec.run("echo hello from burst")
    print(result.stdout)

curl -X POST https://app.opencomputer.dev/api/sandboxes \
  -H "X-API-Key: $OPENCOMPUTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "burst": true,
    "memoryMB": 4096,
    "timeout": 300
  }'

What Happens on Interruption

Infrastructure capacity can be reclaimed or restarted by the cloud provider. When OpenComputer receives advance notice, it notifies the sandbox and starts the burst restart flow. The sandbox receives these environment variables:

OPENSANDBOX_RESUMABLE=true
OPENSANDBOX_RESUME_NOTICE_SECONDS=25

During the notice window, write important state to disk. After resume, restart your process from durable state.

Good Fits

Burst Sandboxes work well for cost-sensitive workloads that can restart from disk:

Batch code execution where failed jobs can be requeued.
CI-style checks, test runners, linters, and formatters.
AI agent tool calls with durable task state outside the sandbox.
Parallel exploration jobs where one attempt can restart.
Development, previews, and experiments where cost matters more than availability.

Poor Fits

Use on-demand sandboxes when process continuity is required:

User-facing interactive sessions where a rare disconnect is still disruptive.
Long-running stateful services that keep important state only in RAM.
Databases, queues, or coordinators running inside the sandbox.
Workloads with strict deadlines and no retry budget.
Any task that cannot safely restart after a partial command failure.

Alpha Limitations

During alpha, Burst Sandboxes have these restrictions:

Capability	Burst alpha behavior
Process state	May restart
Filesystem	Preserved across burst restarts
Notice window	Up to 25 seconds when advance notice is available
Sudden host failure	May resume without advance notice
Capacity	Best effort; create may fail or wait when burst capacity is full

Reliability Pattern

For agent or batch systems, run your work from a small process wrapper and install a restart-notice hook.

Store task state on disk or outside the sandbox.
Write outputs to durable storage as the task progresses.
Install /home/sandbox/.opencomputer/on-restart-notice to flush or checkpoint before restart.
Make your startup command resume from the last durable state.
Use on-demand sandboxes for workloads with no process restart budget.

Example setup:

import { Sandbox } from "@opencomputer/sdk";

const sandbox = await Sandbox.create({
  burst: true,
  timeout: 0,
});

await sandbox.exec.run("mkdir -p /home/sandbox/.opencomputer /home/sandbox/app");

await sandbox.files.write(
  "/home/sandbox/.opencomputer/on-restart-notice",
  `#!/bin/sh
set -eu
echo "restart notice: ${1:-25}s" >> /home/sandbox/app/events.log
touch /home/sandbox/app/restarting
sync
`,
);

await sandbox.exec.run("chmod +x /home/sandbox/.opencomputer/on-restart-notice");

await sandbox.files.write(
  "/home/sandbox/app/worker.sh",
  `#!/bin/sh
set -eu
cd /home/sandbox/app
if [ -f restarting ]; then
  echo "resumed after restart" >> events.log
  rm -f restarting
else
  echo "started" >> events.log
fi

i=$(cat counter 2>/dev/null || echo 0)
while true; do
  i=$((i + 1))
  echo "$i" > counter
  sync
  sleep 5
done
`,
);

await sandbox.exec.run("chmod +x /home/sandbox/app/worker.sh");
await sandbox.exec.background("/home/sandbox/app/worker.sh", {
  maxRunAfterDisconnect: 0,
});

from opencomputer import Sandbox

sandbox = await Sandbox.create(burst=True, timeout=0)

await sandbox.exec.run("mkdir -p /home/sandbox/.opencomputer /home/sandbox/app")

await sandbox.files.write(
    "/home/sandbox/.opencomputer/on-restart-notice",
    """#!/bin/sh
set -eu
echo "restart notice: ${1:-25}s" >> /home/sandbox/app/events.log
touch /home/sandbox/app/restarting
sync
""",
)

await sandbox.exec.run("chmod +x /home/sandbox/.opencomputer/on-restart-notice")

await sandbox.files.write(
    "/home/sandbox/app/worker.sh",
    """#!/bin/sh
set -eu
cd /home/sandbox/app
if [ -f restarting ]; then
  echo "resumed after restart" >> events.log
  rm -f restarting
else
  echo "started" >> events.log
fi

i=$(cat counter 2>/dev/null || echo 0)
while true; do
  i=$((i + 1))
  echo "$i" > counter
  sync
  sleep 5
done
""",
)

await sandbox.exec.run("chmod +x /home/sandbox/app/worker.sh")
await sandbox.exec.background(
    "/home/sandbox/app/worker.sh",
    max_run_after_disconnect=0,
)

When OpenComputer receives notice, it runs the hook with the notice window in seconds. If the sandbox resumes on another worker, start your process again and read the state you wrote under /home/sandbox/app.

Elasticity

Resource tiers and autoscaling

Checkpoints

Save and resume sandbox state

Getting Started

Sandboxes

Browser Sessions

Durable Agent Sessions

Reserved Capacity

CLI

Guides

TypeScript SDK

Python SDK

CLI Reference

API Reference

Resources

Pricing

Create a Burst Sandbox

What Happens on Interruption

Good Fits

Poor Fits

Alpha Limitations

Reliability Pattern

Elasticity

Checkpoints

​Pricing

​Create a Burst Sandbox

​What Happens on Interruption

​Good Fits

​Poor Fits

​Alpha Limitations

​Reliability Pattern

​Related

Elasticity

Checkpoints

Pricing

Create a Burst Sandbox

What Happens on Interruption

Good Fits

Poor Fits

Alpha Limitations

Reliability Pattern

Related