Slopometry OpenCode Plugin

Captures OpenCode session events in-process and forwards them to the slopometry CLI for storage, analysis, and mid-session feedback injection.

How It Works

OpenCode (in-process)                    Slopometry (external)
┌─────────────────────┐                  ┌─────────────────────┐
│  Plugin hooks into:  │                  │                     │
│  - tool.execute.*    │  spawn + stdin   │  hook-opencode CLI  │
│  - bus events        │ ──────────────>  │  parses JSON        │
│  - promptAsync()     │  <── stdout ───  │  stores in DB       │
│                      │    (feedback)    │  generates feedback  │
└─────────────────────┘                  └─────────────────────┘

The plugin hooks into OpenCode's in-process event system and spawns slopometry hook-opencode --event-type <type> per event, passing JSON on stdin. This mirrors how slopometry integrates with Claude Code via shell hooks.

Events Captured

Event	Source	Data
pre_tool_use	tool.execute.before hook	tool name, session ID, call ID, args
post_tool_use	tool.execute.after hook	tool name, args, output (truncated), duration_ms
message_updated	message.updated bus event	per-message tokens, cost, model, agent
todo_updated	todo.updated bus event	full todo list with status/priority
subagent_start	session.created bus event (with parentID)	child session ID, parent ID
stop	session.idle bus event	aggregated tokens, cost, transcript via SDK

Feedback Injection

When slopometry returns feedback on stdout (code smells, context coverage warnings), the plugin injects it in two ways:

1. Inline — appended to tool output via tool.execute.after (visible with the tool result)
2. Stop feedback — on session.idle, if slopometry returns smell feedback, the plugin calls client.session.promptAsync() to send a synthetic user message that triggers a new agent turn to address the smells (mirrors Claude Code's blocking stop hook). An awaitingFeedbackTurn flag prevents the follow-up idle from looping, but re-arms for subsequent user turns.

Installation

Prerequisites

• slopometry must be installed and in PATH (uv tool install slopometry or from source)
• OpenCode v1.2+ with plugin support

Method 1: Symlink into OpenCode config (recommended)

Find your OpenCode config directory:

# Usually one of:
# ~/.config/opencode/          (Linux default)
# $XDG_CONFIG_HOME/opencode/   (if XDG_CONFIG_HOME is set)
# ~/.opencode/                 (macOS / fallback)

Create a plugins directory and symlink:

mkdir -p $XDG_CONFIG_HOME/opencode/plugins
ln -sf /path/to/slopometry/plugins/opencode/index.ts \
       $XDG_CONFIG_HOME/opencode/plugins/slopometry.ts

OpenCode auto-discovers plugins/*.ts files in config directories and auto-installs @opencode-ai/plugin (creates a managed package.json and runs bun install in the config dir on startup).

Method 2: file:// in opencode.json

Add the plugin path to opencode.json (project-level or in .opencode/):

{
  "plugin": ["file:///path/to/slopometry/plugins/opencode"]
}

Then ensure dependencies are installed in the plugin directory:

cd /path/to/slopometry/plugins/opencode
bun install

Method 3: slopometry install command

slopometry install --target opencode

This writes the file:// plugin path into opencode.json in the current directory.

Verification

1. Start an OpenCode session and use some tools (file reads, edits, bash commands)
2. Check that slopometry captured events:

   slopometry solo ls
   slopometry latest
   

3. Verify the session shows source=opencode in the database:

   slopometry solo show <session-id>
   

Development

The plugin is a single TypeScript file (index.ts) that exports a Plugin function. It has no build step — OpenCode (Bun) imports .ts files directly.

To iterate on the plugin:

1. Edit index.ts
2. Restart OpenCode (the plugin is loaded on startup)
3. Check slopometry hook-opencode --help for the CLI interface

To test the CLI handler in isolation:

echo '{"tool":"Bash","session_id":"test","call_id":"c1","args":{"command":"ls"}}' \
  | slopometry hook-opencode --event-type pre_tool_use