---
title: Start warm workers from a snapshot
sidebarTitle: Warm workers
description: Install a toolchain once and launch clean workers from the captured disk state
icon: "code-branch"
---
Local-only
Package installation often costs more than sandbox boot. This example installs OpenCode once, records the stopped sandbox as an integrity-checked snapshot, and launches fresh workers from that prepared filesystem.
## Start a warm worker
Create the worker verification script that the snapshot will carry into every worker:
```sh verify-worker.sh
#!/bin/sh
set -eu
test "$(id -u)" -ne 0
git init -q
git add .
git -c user.name=microsandbox \
-c user.email=worker@microsandbox.local \
commit -qm "sandbox baseline"
test -z "$(git remote)"
opencode --version
```
Create the preparation script that installs the baseline toolchain:
```sh prepare-worker.sh
#!/bin/sh
set -eu
apt-get update
apt-get install -y --no-install-recommends ca-certificates git
rm -rf /var/lib/apt/lists/*
npm install -g opencode-ai@1.18.4
mkdir -p /workspace/project
chown -R node:node /workspace
opencode --version
```
```sh macOS & Linux
msb run --name agent-base --replace \
--cpus 2 --memory 2G --root-disk 4G \
--script-path prepare-worker:./prepare-worker.sh \
--script-path verify-worker:./verify-worker.sh \
--entrypoint prepare-worker \
node:24-bookworm-slim
```
```powershell Windows
msb run --name agent-base --replace `
--cpus 2 --memory 2G --root-disk 4G `
--script-path prepare-worker:./prepare-worker.sh `
--script-path verify-worker:./verify-worker.sh `
--entrypoint prepare-worker `
node:24-bookworm-slim
```
When the command exits, `agent-base` is stopped and ready to snapshot.
```sh macOS & Linux
msb snapshot create coding-agent-base \
--from-sandbox agent-base \
--integrity
```
```powershell Windows
msb snapshot create coding-agent-base `
--from-sandbox agent-base `
--integrity
```
Verify the captured snapshot before using it:
```sh
msb snapshot verify agent-base:coding-agent-base
```
The snapshot captures the writable disk changes and pins the source image. This disk snapshot does not capture memory, running processes, network state, or environment variables. Owned storage is captured; external directory bindings require explicit destination choices. Integrity verification detects later changes to those captured bytes; it does not attest who built the snapshot or whether its packages are trustworthy.
Snapshots preserve every file written to the guest disk, including shell history, tool configuration, and cached credentials. Build the baseline in a trusted workflow, and never authenticate OpenCode or place registry tokens, source code, or API keys in `agent-base`.
Restore creates an idle detached sandbox with its security, resource, and lifetime controls applied before boot. It requires an unused name; remove a previous stopped worker explicitly before reusing that name. Start each workload separately with `msb exec`.
```sh macOS & Linux
msb restore agent-base:coding-agent-base --name coding-worker-1 \
--cpus 2 --memory 2G \
--user node --security restricted --max-duration 1h
```
```powershell Windows
msb restore agent-base:coding-agent-base --name coding-worker-1 `
--cpus 2 --memory 2G `
--user node --security restricted --max-duration 1h
```
Transfer the committed project tree into the worker:
```sh macOS & Linux
git -C ./my-project archive --format=tar HEAD | \
msb exec --stream --user node \
--rlimit nproc=256 --rlimit nofile=1024 --rlimit fsize=268435456 \
coding-worker-1 -- tar -x -C /workspace/project
```
```powershell Windows
git -C ./my-project archive --format=tar --output=project.tar HEAD
msb cp ./project.tar coding-worker-1:/tmp/project.tar
msb exec --user node `
--rlimit nproc=256 --rlimit nofile=1024 --rlimit fsize=268435456 `
coding-worker-1 -- tar -x -f /tmp/project.tar -C /workspace/project
Remove-Item ./project.tar
```
Create a credential-free Git baseline and verify the worker boundary:
```sh macOS & Linux
msb exec --user node --workdir /workspace/project \
--rlimit nproc=256 --rlimit nofile=1024 --rlimit fsize=268435456 \
coding-worker-1 -- verify-worker
```
```powershell Windows
msb exec --user node --workdir /workspace/project `
--rlimit nproc=256 --rlimit nofile=1024 --rlimit fsize=268435456 `
coding-worker-1 -- verify-worker
```
Start OpenCode after those checks pass:
```sh macOS & Linux
msb exec -t --user node --workdir /workspace/project \
--rlimit nproc=256 --rlimit nofile=1024 --rlimit fsize=268435456 \
coding-worker-1 -- opencode
```
```powershell Windows
msb exec -t --user node --workdir /workspace/project `
--rlimit nproc=256 --rlimit nofile=1024 --rlimit fsize=268435456 `
coding-worker-1 -- opencode
```
Dedicated restore does not accept rootfs patches such as `--copy-dir`, so the worker boots first and receives the committed tree afterward. `git archive` excludes `.git`, checkout credentials, and untracked files such as a local `.env`; review the committed tree for secrets before sending it. Initializing a new repository inside the worker preserves useful diff workflows without copying host remotes or credentials. Each transferred or interactive workload sets its own process, file-descriptor, and per-file limits.
Each launch receives its own writable layer. Changes made by one worker do not modify the snapshot, the host project, or another worker.
This worker uses microsandbox's default public-internet profile so OpenCode can reach a configured provider. For sensitive projects, replace it with a deny-by-default allowlist for the provider and source hosts you need, and use [host-held secrets](/sandboxes/secrets) instead of copying credentials into the worker.
Create more workers by changing the sandbox name:
```sh macOS & Linux
msb restore agent-base:coding-agent-base --name coding-worker-2 \
--user node --security restricted --max-duration 1m
msb exec --user node --timeout 1m \
--rlimit nproc=256 --rlimit nofile=1024 --rlimit fsize=268435456 \
coding-worker-2 -- opencode --version
msb stop coding-worker-2
```
```powershell Windows
msb restore agent-base:coding-agent-base --name coding-worker-2 `
--user node --security restricted --max-duration 1m
msb exec --user node --timeout 1m `
--rlimit nproc=256 --rlimit nofile=1024 --rlimit fsize=268435456 `
coding-worker-2 -- opencode --version
msb stop coding-worker-2
```
Remove the prepared sandbox and workers:
```sh macOS & Linux
msb rm -f agent-base coding-worker-1 coding-worker-2
rm -f prepare-worker.sh verify-worker.sh
```
```powershell Windows
msb rm -f agent-base coding-worker-1 coding-worker-2
Remove-Item prepare-worker.sh, verify-worker.sh
```
Remove the reusable snapshot only when you no longer need it:
```sh
msb snapshot rm agent-base:coding-agent-base
```
## Refresh the baseline
Installed snapshot members are immutable. To update packages, recreate `agent-base`, then capture a new member name and use its group-qualified selector for future workers:
```sh
msb snapshot create coding-agent-base-v2 --from-sandbox agent-base --integrity
msb snapshot verify agent-base:coding-agent-base-v2
```
See [Snapshots](/sandboxes/snapshots) for archive, integrity, and portability details.