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 auth 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"
      }
    }
  }
}

3. Run OpenCode

opencode

Profiles and SDK features

The plugin now reads the same Meridian configuration files the meridian CLI uses, so you can maintain multiple Claude accounts and tune SDK behavior without leaving OpenCode.

Profiles (~/.config/meridian/profiles.json)

Define one or more named profiles (for example, a personal Claude Max account and a work account). The plugin forwards them to Meridian at startup.

[
  {
    "id": "personal",
    "claudeConfigDir": "/Users/me/.config/meridian/profiles/personal"
  },
  {
    "id": "work",
    "claudeConfigDir": "/Users/me/.config/meridian/profiles/work"
  }
]

Active profile (~/.config/meridian/settings.json)

{ "activeProfile": "work" }

activeProfile selects the default profile for any request that does not send an explicit x-meridian-profile header. If the saved id is not in profiles.json (or the file is missing), the plugin logs a warning and falls back to the first configured profile.

SDK features (~/.config/meridian/sdk-features.json)

Meridian reads this file lazily on every request, so overrides take effect without restarting the proxy. The plugin does not need to do anything special for it to work — just edit the file and the next request picks it up. See Meridian's documentation for the full list of adapter keys.

This plugin does not edit Meridian's SDK feature file. When Meridian's default client prompt pass-through is enabled, the plugin scrubs OpenCode-identifying prompt fingerprints with @rynfar/meridian-plugin-opencode-scrub before forwarding. User context such as AGENTS.md and configured instructions is preserved, while cwd is forwarded to Meridian through the process environment.

{
  "opencode": {
    "memory": true,
    "thinking": "enabled",
    "maxBudgetUsd": 0.5
  }
}

Environment overrides

For parity with the meridian CLI:

• MERIDIAN_PROFILES — JSON array of profile objects; wins over profiles.json.
• MERIDIAN_DEFAULT_PROFILE — profile id; wins over settings.activeProfile.

Malformed or missing files never crash the plugin; all parse/IO failures are logged via OpenCode's plugin log and the plugin falls back to no-profile mode.

Switching profiles at runtime

Profile switching through Meridian's HTTP API continues to work — call POST /profiles/active on the proxy URL the plugin prints at startup. The selection is persisted back to settings.json and survives restarts.

Troubleshooting

"Claude Code CLI not found"

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

"Claude not authenticated"

claude auth login
# or (depends of your version)
claude login

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

"Proxy failed to start"

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

Binding the proxy to a non-localhost interface

Meridian binds to 127.0.0.1 by default. If you need it to listen on another interface, set CLAUDE_PROXY_HOST (or Meridian's MERIDIAN_HOST alias) before starting OpenCode:

CLAUDE_PROXY_HOST=0.0.0.0 opencode serve --hostname 0.0.0.0 --port 4098

The plugin still uses loopback internally when you bind to wildcard addresses such as 0.0.0.0 or ::, so local health checks and provider requests remain stable.

Warning

Exposing the proxy beyond localhost makes your authenticated Claude session reachable over the network. Only do this on trusted networks, and prefer firewall rules or other access controls if you open it up.

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 in the Anthropic provider config, so set a placeholder such as "dummy" in opencode.json — 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.

Powered by the Claude Agent SDK by Anthropic and OpenCode.

License

MIT