Configure BoxedCode Skill

Configure BoxedCode

Configure BoxedCode/OpenCode agents with markdown files. Use when creating/customising agents, or when the sandbox prevents operations the user says are legitimate.

About BoxedCode

BoxedCode is a simple wrapper around OpenCode. It provides default config for our available provider/models and lightweight filesystem/network sandboxing to make OpenCode’s tools safer.

Create + customise agents (markdown)

boxedcode writes config to ~/.config/opencode/opencode.jsonc. Don't edit this file to create agents; instead, create markdown files.

1) Choose scope + location

Project scope: .opencode/agent/
Global scope: ~/.config/opencode/agent/

The sandbox prevents you from writing to these locations directly. Present the content to the user and ask them to create files with the content you generate.

2) Create an agent markdown file

File name becomes the agent name (example: review.md → review agent).
Use YAML frontmatter at top; put prompt content after.
Prompts override the default system prompt for that agent.
Frontmatter options are merged with defaults; only specify what you want to change.

Minimal template:

---
description: Reviews code for quality and best practices
mode: subagent
model: github-copilot/claude-sonnet-4.6
temperature: 0.1
tools:
  write: false
  edit: false
  bash: false
---

Focus on:

- Code quality
- Potential bugs
- Performance
- Security

Provide feedback only; do not edit files.

3) Customize frontmatter options

description (required): short, concrete use-case
mode: primary, subagent, or all
model: github-copilot/model-id
temperature: 0.0–1.0
tools: coarse on/off switches for built-in tools (for example write, edit, bash)
permission: fine-grained allow/ask/deny rules per tool or per bash/skill pattern; combines with tools

bash: allow and bash."*": allow are disallowed and overridden by boxedcode to bash."*": ask.

Example with permissions:

---
description: Read-only reviewer
mode: subagent
permission:
  edit: deny
  bash:
    "*": ask
    "git diff": allow
    "git log*": allow
---

Only analyze and suggest changes.

4) Verify

Quit boxedcode and boxedcode --continue to reload config.
boxedcode debug config to see final merged config and troubleshoot.
Invoke subagents directly @agent-name or <tab> to primary agent.

Configure sandbox (box.json)

Sandbox user config file: ~/.nwb/box/box.json. It is merged with the base config.

Network config

network.allowedDomains (array, supports subdomain wildcards *.example.com).
network.deniedDomains (array, checked first).

Filesystem config

Read:

filesystem.denyRead (array).

Write:

filesystem.allowWrite (array).
filesystem.denyWrite (array, takes precedence).

Path syntax:

macOS: git-style globs (*, **, ?, [abc]).
All: absolute or relative; ~ expands to home.

git push

The sandbox prevents auth with git remotes via ssh. Use https remotes with the gh cli credential helper.

gh auth setup-git (one time)

The user can remap any ssh remote-urls to https in via global git config:

# ~/.gitconfig
[url "https://github.com/eeveebank/"]
    insteadOf = "git@github.com:eeveebank/"

You cannot edit this file directly from the sandbox.

Agent Skills: Configure BoxedCode

Install this agent skill to your local

Skill Files