opencode-with-claude

Use OpenCode with your Claude Max subscription.

What this is

An OpenCode plugin that runs Meridian (formerly opencode-claude-max-proxy) for you: start OpenCode once and the proxy comes up with it; quit OpenCode and the proxy stops. No separate proxy CLI or Docker container to manage.

Compared to running the proxy yourself:

One process to think about — OpenCode owns the proxy lifecycle (start/stop) instead of you juggling two things.
Several OpenCode windows at once — each instance gets its own proxy on an OS-assigned port, so ports do not collide and you avoid session issues from sharing one proxy across instances.
Explicit session headers — the plugin adds session tracking on outgoing API calls, so the proxy does not have to infer sessions from fingerprints alone.

How It Works

┌─────────────┐              ┌────────────────────┐       ┌─────────────────┐
│  OpenCode   │─────────────▶│  Claude Max Proxy  │──────▶│    Anthropic    │
│  (TUI/Web)  │ :3456 / auto │   (local server)   │  SDK  │    Claude Max   │
│             │◀─────────────│                    │◀──────│                 │
└─────────────┘              └────────────────────┘       └─────────────────┘

Quick Start

The plugin hooks into OpenCode's plugin system. When OpenCode launches, it starts the proxy, configures the Anthropic provider, and cleans everything up on exit.

1. Install the plugin

npm install -g opencode-with-claude

2. Authenticate with Claude (one-time)

npm install -g @anthropic-ai/claude-code
claude login

3. Add to your opencode.json

Global (~/.config/opencode/opencode.json) or project-level:

{
  "$schema": "https://opencode.ai/config.json",
  "plugin": ["opencode-with-claude"],
  "provider": {
    "anthropic": {
      "options": {
        "baseURL": "http://127.0.0.1:3456",
        "apiKey": "dummy"
      }
    }
  }
}

Note: The apiKey is a placeholder — authentication goes through your Claude Max session via claude login, not an API key. The baseURL is the default proxy port. If port 3456 is already in use (e.g., another OpenCode instance), the plugin automatically starts the proxy on a different port and overrides the baseURL at runtime.

3. Run OpenCode

opencode

Troubleshooting

"Claude Code CLI not found"

npm install -g @anthropic-ai/claude-code

"Claude not authenticated"

claude login

This opens a browser for OAuth. Your Claude Max subscription credentials are needed.

"Proxy failed to start"

Check Claude auth: claude auth status
Ensure your internet connection is working
If using a manual port override, check if it's in use: lsof -i :$CLAUDE_PROXY_PORT

Development

Project Structure

opencode-with-claude/
├── src/
│   ├── index.ts           # Plugin entry point
│   ├── proxy.ts           # Proxy lifecycle management
│   └── logger.ts          # Plugin logger
├── test/
│   ├── run.sh             # Test runner
│   └── opencode.json      # Test config
├── package.json
└── tsconfig.json

Build

npm install
npm run build

Test locally

./test/run.sh              # Build and launch OpenCode with the plugin
./test/run.sh --clean      # Remove build artifacts

FAQ

Do I need an Anthropic API key?

No. Claude Max is not authenticated with API keys here. Run claude login once; the proxy uses that session (Agent SDK via OAuth). OpenCode still expects an apiKey field, so the plugin supplies a placeholder — it is not used for real auth.

What if my Claude Max subscription lapses?

The proxy will fail to authenticate. Run claude auth status. You need an active Claude Max plan; see claude.ai for current options and pricing.

Can I run several OpenCode instances at once?

Yes. The first instance uses port 3456 by default; others get a free OS-assigned port, so nothing extra to configure.

Is this the same as using the Anthropic API directly?

Not exactly. OpenCode speaks Anthropic-style HTTP to the local proxy; the proxy maps requests to the Claude Agent SDK and your Claude Max session. Usage limits follow your Max subscription, not Anthropic API billing tiers.

Disclaimer

This project is an unofficial wrapper around Anthropic's publicly available Claude Agent SDK and OpenCode. It is not affiliated with, endorsed by, or supported by Anthropic or OpenCode.

Use at your own risk. The authors make no claims regarding compliance with Anthropic's Terms of Service. It is your responsibility to review and comply with Anthropic's Terms of Service and Authorized Usage Policy. Terms may change at any time.

This project calls publicly available npm packages using your own authenticated account. No API keys are intercepted, no authentication is bypassed, and no proprietary systems are reverse-engineered.

Credits

Built on top of Meridian by @rynfar, which provides the core proxy that bridges the Anthropic Agent SDK to the standard API.

License

MIT