Modular Agents for OpenCode

Define agents as folders with multiple maintainable prompt files.

Features

• Agents as folders instead of single files
• Recursively includes all .md and .txt files
• Supports all agent configuration fields via YAML frontmatter
• Works alongside native single-file agents

Installation

From npm (Recommended)

opencode plugin modular-agents --global

Or add it to your opencode.json:

{
  "plugin": ["modular-agents"]
}

Local Development

Place modular-agents.ts and package.json in:

• .opencode/plugins/ (project level)
• or ~/.config/opencode/plugins/ (global)

Usage

Create folders inside .opencode/agents/ (project) or ~/.config/opencode/agents/ (global).

Folder Structure Example

.opencode/agents/rust-expert/
├── index.md                 # Recommended
├── rules/
│   ├── core.md
│   └── security.md
├── examples/
│   └── good-patterns.md
├── constraints.md
└── test/
    └── index.md             # Included as normal content

index.md – Recommended, Not Strictly Required

• If index.md exists in the folder root, OpenCode parses it (frontmatter + base prompt).
• The plugin then enriches that prompt with all other .md/.txt files found recursively.
• If there is no index.md, the plugin will still create the agent using the folder name and all other files as the prompt. This is useful for trait-only / composable agents.

Example without index.md (trait composition):

.opencode/agents/code-reviewer/
├── pragmatic.txt
├── security-focused.txt
└── concise.txt

This creates an agent called code-reviewer composed purely from the trait files.

How Files Are Merged

• OpenCode handles the index.md (if present).
• The plugin appends every other .md and .txt file (including index.md files inside subfolders).
• YAML frontmatter in additional files is stripped.
• Files are sorted alphabetically by relative path.
• Subfolder index.md files become regular sections (e.g. ### test/index.md).

Resulting Prompt

You are a senior Rust developer...

### constraints.md
...

### rules/core.md
...

### test/index.md
...

This design lets you build large, maintainable agents from smaller reusable pieces.

Limitations

• Changes require restarting the session.
• Best suited for complex or large agents.

License

This project is open source and available under the MIT license.