OpenCode Micromanager

An OpenCode plugin that intercepts the full context being sent to the LLM before each request. Opens your editor so you can review the system prompt, message history, and current user message -- and optionally edit the message before it's sent.

Install

Clone into any project directory:

git clone https://github.com/YOUR_USERNAME/opencode-micromanager.git
cd opencode-micromanager

Install plugin dependencies:

cd .opencode && bun install && cd ..

Quick Start

1. Copy the example config to your project root:

cp .micromanager.jsonc .micromanager.jsonc

2. Set your editor (must support a "wait" flag):

export EDITOR='codium -w'   # or 'code -w', 'subl -w', 'zed --wait', etc.

3. Start OpenCode:

opencode

Send any message. Your editor will open with the full LLM context before the request is sent.

How It Works

The plugin hooks into three OpenCode events that fire before each LLM request:

1. experimental.chat.system.transform -- captures the system prompt
2. experimental.chat.messages.transform -- captures the full message history and opens the editor
3. tool.execute.before -- logs tool executions

When the editor opens, you see:

• System Prompt -- all instructions, rules, and agent config being sent
• Message History -- every prior user/assistant turn, including tool calls and outputs
• Current User Message -- the new message (editable)

Edit the text below the last (Current - Editable) header, save, and close. The modified text is sent to the LLM.

Configuration

Edit .micromanager.jsonc in your project root:

{
  "logLevel": "info",
  "enableEditor": true,
  "autoEdit": true,
  // Override the editor command (defaults to $EDITOR env var, then "nano")
  // "editor": "codium -w",
  "showSystemMessages": true,
  "messageTypes": ["user", "assistant"]
}

Option	Default	Description
logLevel	"info"	Log verbosity: debug, info, warn, error
enableEditor	true	Enable the editor feature
autoEdit	false	Open editor automatically for every message
editor	$EDITOR or "code -w"	GUI editor command (must block until closed)
showSystemMessages	true	Include system prompt in editor view
messageTypes	["user", "assistant"]	Message types to intercept

The plugin looks for .micromanager.jsonc first, then .micromanager.json. JSONC comments are supported.

Project Structure

opencode-micromanager/
├── .micromanager.jsonc              # Plugin configuration
├── .opencode/
│   ├── plugins/
│   │   └── message-interceptor.ts   # Plugin source
│   ├── package.json                 # Plugin dependencies
│   └── opencode.json                # OpenCode project config
├── package.json
└── README.md

Building

The plugin loads directly from .opencode/plugins/ as TypeScript. No build step is required for normal use.

To type-check or produce a compiled JS output:

# Using bun (from project root)
bun run build

# Using tsc (from .opencode/)
cd .opencode && bun run build

Editor Notes

OpenCode's TUI controls the terminal, so terminal editors (vim, nano, etc.) will not work. You must use a GUI editor with a "wait" flag that blocks until the file is closed.

Editor	Command
VS Code	code -w
VSCodium	codium -w
Sublime Text	subl -w
Zed	zed --wait

Set it via the $EDITOR environment variable or the editor field in .micromanager.jsonc.

License

MIT