Use JetBrains with a sandboxed agent

Keep your JetBrains IDE on your computer and run OpenCode inside a microsandbox. The IDE connects through ACP, a protocol for talking to coding agents. No microsandbox IDE plugin is needed. You need JetBrains AI Assistant.

Create a sandbox

Start with a small test project. Run these commands on your computer:

mkdir -p "$HOME/jetbrains-acp-demo"
cd "$HOME/jetbrains-acp-demo"
git init
REPO_PATH="$(pwd -P)"

msb create --name jetbrains-agent -c 2 -m 4G \
  -v "$REPO_PATH:$REPO_PATH" \
  -v jetbrains-agent-home:/root \
  -w "$REPO_PATH" node:22-bookworm </dev/null

msb exec jetbrains-agent --no-tty -- \
  npm install -g opencode-ai@1.18.32 </dev/null

msb exec jetbrains-agent --no-tty -- sh -c \
  'mkdir -p "$HOME/.config/opencode" && printf "%s\n" "{\"model\": \"opencode/mimo-v2.5-free\"}" > "$HOME/.config/opencode/opencode.json"' </dev/null

The last command writes OpenCode’s configuration to ~/.config/opencode/opencode.json inside the sandbox. OpenCode loads this file on its own, so nothing about the model needs to live in the IDE’s configuration. Edit it there, or copy in an existing opencode.json or opencode.jsonc, when you need more than a model name.Open this project in JetBrains using the same absolute path. The project must have the same path inside and outside the sandbox so the agent can find it.The project folder is shared: changes the agent makes also appear on your computer. The jetbrains-agent-home volume saves the agent’s settings and login. Keep your host home directory unmounted.

Connect the agent

In AI Chat > Add Custom Agent, open ~/.jetbrains/acp.json and add the configuration below. If the file already has agents, merge the entries instead of replacing it.Replace /absolute/path/to/msb with the output of:

command -v msb

{
  "default_mcp_settings": {
    "use_idea_mcp": false,
    "use_custom_mcp": false
  },
  "agent_servers": {
    "OpenCode in microsandbox": {
      "command": "/absolute/path/to/msb",
      "args": [
        "exec", "jetbrains-agent", "--stream",
        "--", "opencode", "acp"
      ]
    }
  }
}

Keep --stream: it lets the IDE and agent exchange messages while the agent runs. Do not replace it with --no-tty or disconnect its stdin.msb exec runs as the sandbox’s default user and sets HOME to that user’s home directory. If your OpenCode configuration belongs to a different user, add "-u", "<user>" before "--".The two MCP settings disable IDE and custom MCP tools, which may run outside the sandbox. These defaults also affect other agents that inherit them. Check that your sandbox agent does not override either setting to true.

Try it in AI Chat

Select OpenCode in microsandbox and send:

Create hello.txt, run ls and uname -s, then read hello.txt back to me.

Check that hello.txt appears in your project and the shell reports Linux.The example model was used with test data. Before opening a real project, choose a provider and model approved for your data, log in inside the sandbox, and replace the model name in the sandbox’s opencode.json:

msb exec jetbrains-agent -- opencode auth login

Your login is saved in the sandbox’s home volume. Do not commit credentials.

Work on more than one project

agent_servers is an object keyed by the name shown in AI Chat, so it takes any number of named entries. It cannot be an array. You have two ways to cover several projects. One sandbox for all projects. The IDE sends each project’s path to the agent when a chat starts, so a single entry works for every project that is mounted at its host path. Mounts are set when the sandbox is created, so add one -v per project:

REPO_A="$(cd /path/to/repo-a && pwd -P)"
REPO_B="$(cd /path/to/repo-b && pwd -P)"

msb create --name jetbrains-agent -c 2 -m 4G \
  -v "$REPO_A:$REPO_A" \
  -v "$REPO_B:$REPO_B" \
  -v jetbrains-agent-home:/root \
  -w "$REPO_A" node:22-bookworm </dev/null

The agent can reach every mounted project, whichever one the IDE has open. A project-level opencode.json still applies only to its own project. A parent directory mounted at its host path, such as -v "$HOME/Dev:$HOME/Dev", covers every project under it with one mount. The agent can then reach everything in that directory. One sandbox per project. Create a sandbox for each project and add one entry per sandbox. The entries differ only in the sandbox name:

{
  "agent_servers": {
    "OpenCode: repo-a": {
      "command": "/absolute/path/to/msb",
      "args": ["exec", "agent-repo-a", "--stream", "--", "opencode", "acp"]
    },
    "OpenCode: repo-b": {
      "command": "/absolute/path/to/msb",
      "args": ["exec", "agent-repo-b", "--stream", "--", "opencode", "acp"]
    }
  }
}

Use this when projects must not see each other’s files. In scripted tests, one OpenCode 1.18.32 process kept a separate working directory and project configuration for each session. Opening several projects from the JetBrains GUI has not been verified. JetBrains supports env only inside an agent entry; there is no global env. Keep shared settings in the sandbox so there is nothing to copy:

OpenCode settings go in the sandbox’s ~/.config/opencode/opencode.json.
Environment variables go on the sandbox: pass -e KEY=value to msb create. To change one on a running sandbox, run msb modify jetbrains-agent -e KEY=value --restart to apply it now, or use --next-start to save it for the next start.

What the sandbox protects

The agent can edit the shared project. ACP also allows agents to ask the IDE to read files or run commands on the host, so running an agent in a sandbox does not automatically keep every tool inside it. The MCP settings above do not disable those ACP requests. Review any MCP servers configured in the agent, too. Do not mount ~/.jetbrains into the sandbox. The IDE reads acp.json on your computer, and the agent does not need it. That file sets the commands the IDE runs on the host, so an agent that can write to it can change what runs outside the sandbox. Scripted tests of OpenCode 1.18.32 kept file and shell operations inside the sandbox and could not read an unmounted host file. Recheck this behavior when changing agents or versions. The JetBrains GUI flow has not been verified, and the IDE can still send project context to the model.

Other options

Override OpenCode settings for one entry

OPENCODE_CONFIG_CONTENT holds OpenCode configuration as a JSON string and takes precedence over the configuration files. Use it when one entry needs a different setting, such as a second entry with another model:

{
  "args": [
    "exec", "jetbrains-agent", "--stream",
    "-e", "OPENCODE_CONFIG_CONTENT",
    "--", "opencode", "acp"
  ],
  "env": {
    "OPENCODE_CONFIG_CONTENT": "{\"model\":\"opencode/mimo-v2.5-free\"}"
  }
}

The -e flag forwards the variable into the sandbox. To load a configuration file from a non-default path instead, forward a path with "-e", "OPENCODE_CONFIG=/path/in/sandbox/opencode.json".

Use Claude Code instead

Install the adapter and Claude Code in the same sandbox, then log in:

msb exec jetbrains-agent --no-tty -- npm install -g \
  @agentclientprotocol/claude-agent-acp@0.81.2 \
  @anthropic-ai/claude-code@2.1.282 </dev/null
msb exec jetbrains-agent -- claude auth login

Complete the browser login and paste the returned code into the guest terminal if prompted.Add an entry under agent_servers with the same command path and these arguments:

{
  "args": ["exec", "jetbrains-agent", "--stream", "--", "claude-agent-acp"]
}

Keep both MCP settings false. The adapter initialized in scripted testing, but authenticated prompts and isolation remain unverified. Its changelog says version 0.18.0 switched to built-in Claude tools; older adapters may behave differently.If using an API key, add "-e", "ANTHROPIC_API_KEY" before "--" to pass it into the sandbox. Values in acp.json’s env only reach the host subprocess unless explicitly forwarded. Prefer the saved guest login to putting keys in this file.

Connect through SSH instead

Authorize your public key:

msb ssh authorize --file ~/.ssh/id_ed25519.pub

Add this to ~/.ssh/config, replacing the msb path:

Host jetbrains-agent.msb
  User root
  IdentityFile ~/.ssh/id_ed25519
  IdentitiesOnly yes
  ProxyCommand /absolute/path/to/msb ssh serve jetbrains-agent --stdio

Verify the host key on first connection. In JetBrains Gateway, enable parsing of ~/.ssh/config and select this host.SSH commands and SFTP were tested. Gateway backend installation and IDE startup remain untested. See SSH and Gateway setup.

​Work on more than one project

​Share settings across entries

​What the sandbox protects

​Other options

Work on more than one project

Share settings across entries

What the sandbox protects

Other options