OpenCode Langfuse Plugin

Automatic LLM observability for OpenCode using Langfuse via OpenTelemetry.

Zero-config tracing of sessions, messages, tool calls, costs, and performance.

Installation

npm install opencode-plugin-langfuse
# or
bun add opencode-plugin-langfuse

Setup

1. Get Langfuse Credentials

Sign up at cloud.langfuse.com and create a project.

Go to Settings → API Keys and copy your keys.

2. Configure Environment

export LANGFUSE_PUBLIC_KEY="pk-lf-..."
export LANGFUSE_SECRET_KEY="sk-lf-..."
export LANGFUSE_BASEURL="https://cloud.langfuse.com"  # Optional

3. Enable Plugin + OTEL

In .opencode/opencode.json:

{
  "experimental": {
    "openTelemetry": true
  },
  "plugin": ["opencode-plugin-langfuse"]
}

4. Run OpenCode

That's it! All traces appear automatically in your Langfuse dashboard.

How It Works

This plugin initializes a LangfuseSpanProcessor that captures all OpenTelemetry spans emitted by OpenCode when experimental.openTelemetry is enabled.

OpenCode (OTEL spans) → LangfuseSpanProcessor → Langfuse Dashboard

Environment Variables

| Variable | Required | Default | Description | | --------------------- | -------- | ---------------------------- | ---------------------- | | LANGFUSE_PUBLIC_KEY | Yes | - | Langfuse public key | | LANGFUSE_SECRET_KEY | Yes | - | Langfuse secret key | | LANGFUSE_BASEURL | No | https://cloud.langfuse.com | Self-hosted instance |

Self-Hosting

export LANGFUSE_BASEURL="https://langfuse.yourcompany.com"

See Langfuse self-hosting docs.

Troubleshooting

No traces appearing

1. Verify experimental.openTelemetry: true is set
2. Check credentials: echo $LANGFUSE_PUBLIC_KEY
3. Check Langfuse health: curl https://cloud.langfuse.com/api/public/health

Plugin not loading

• Ensure opencode-plugin-langfuse is in dependencies (not devDependencies)
• Verify .opencode/opencode.json syntax

License

MIT © omercnet

Related

• OpenCode
• Langfuse
• Langfuse OTEL Integration