opencode-claude-max-proxy

Use your Claude Max subscription with OpenCode.

The Problem

Anthropic doesn't allow Claude Max subscribers to use their subscription with third-party tools like OpenCode. If you want to use Claude in OpenCode, you have to pay for API access separately - even though you're already paying for "unlimited" Claude.

Your options are:

1. Use Claude's official apps only (limited to their UI)
2. Pay again for API access on top of your Max subscription
3. Use this proxy

The Solution

This proxy bridges the gap using Anthropic's own tools:

OpenCode → Proxy (localhost:3456) → Claude Agent SDK → Your Claude Max Subscription

The Claude Agent SDK is Anthropic's official npm package that lets developers build with Claude using their Max subscription. This proxy simply translates OpenCode's API requests into SDK calls.

Your Max subscription. Anthropic's official SDK. Zero additional cost.

Is This Allowed?

Yes. Here's why:

Concern	Reality
"Bypassing restrictions"	No. We use Anthropic's public SDK exactly as documented
"Violating TOS"	No. The SDK is designed for programmatic Claude access
"Unauthorized access"	No. You authenticate with claude login using your own account
"Reverse engineering"	No. We call query() from their npm package, that's it

The Claude Agent SDK exists specifically to let Max subscribers use Claude programmatically. We're just translating the request format so OpenCode can use it.

~200 lines of TypeScript. No hacks. No magic. Just format translation.

Features

Feature	Description
Zero API costs	Uses your Claude Max subscription, not per-token billing
Full compatibility	Works with any Anthropic model in OpenCode
Streaming support	Real-time SSE streaming just like the real API
Auto-start	Optional launchd service for macOS
Simple setup	Two commands to get running

Prerequisites

1. Claude Max subscription - Subscribe here

2. Claude CLI installed and authenticated:

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

3. Bun runtime:

   curl -fsSL https://bun.sh/install | bash

Installation

git clone https://github.com/rynfar/opencode-claude-max-proxy
cd opencode-claude-max-proxy
bun install

Usage

Start the Proxy

bun run proxy

Run OpenCode

ANTHROPIC_API_KEY=dummy ANTHROPIC_BASE_URL=http://127.0.0.1:3456 opencode

Select any anthropic/claude-* model (opus, sonnet, haiku).

One-liner

bun run proxy & ANTHROPIC_API_KEY=dummy ANTHROPIC_BASE_URL=http://127.0.0.1:3456 opencode

Auto-start on macOS

Set up the proxy to run automatically on login:

cat > ~/Library/LaunchAgents/com.claude-max-proxy.plist << EOF
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>Label</key>
    <string>com.claude-max-proxy</string>
    <key>ProgramArguments</key>
    <array>
        <string>$(which bun)</string>
        <string>run</string>
        <string>proxy</string>
    </array>
    <key>WorkingDirectory</key>
    <string>$(pwd)</string>
    <key>RunAtLoad</key>
    <true/>
    <key>KeepAlive</key>
    <true/>
</dict>
</plist>
EOF

launchctl load ~/Library/LaunchAgents/com.claude-max-proxy.plist

Then add an alias to ~/.zshrc:

echo "alias oc='ANTHROPIC_API_KEY=dummy ANTHROPIC_BASE_URL=http://127.0.0.1:3456 opencode'" >> ~/.zshrc
source ~/.zshrc

Now just run oc to start OpenCode with Claude Max.

Model Mapping

OpenCode Model	Claude SDK
anthropic/claude-opus-*	opus
anthropic/claude-sonnet-*	sonnet
anthropic/claude-haiku-*	haiku

Configuration

Environment Variable	Default	Description
CLAUDE_PROXY_PORT	3456	Proxy server port
CLAUDE_PROXY_HOST	127.0.0.1	Proxy server host

How It Works

1. OpenCode sends a request to http://127.0.0.1:3456/messages (thinking it's the Anthropic API)
2. Proxy receives the request and extracts the messages
3. Proxy calls query() from the Claude Agent SDK with your prompt
4. Claude Agent SDK authenticates using your Claude CLI login (tied to your Max subscription)
5. Claude processes the request using your subscription
6. Proxy streams the response back in Anthropic SSE format
7. OpenCode receives the response as if it came from the real API

The proxy is ~200 lines of TypeScript. No magic, no hacks.

FAQ

Why do I need ANTHROPIC_API_KEY=dummy?

OpenCode requires an API key to be set, but we never actually use it. The Claude Agent SDK handles authentication through your Claude CLI login. Any non-empty string works.

Does this work with other tools besides OpenCode?

Yes! Any tool that uses the Anthropic API format can use this proxy. Just point ANTHROPIC_BASE_URL to http://127.0.0.1:3456.

What about rate limits?

Your Claude Max subscription has its own usage limits. This proxy doesn't add any additional limits.

Is my data sent anywhere else?

No. The proxy runs locally on your machine. Your requests go directly to Claude through the official SDK.

Troubleshooting

"Authentication failed"

Run claude login to authenticate with the Claude CLI.

"Connection refused"

Make sure the proxy is running: bun run proxy

Proxy keeps dying

Use the launchd service (see Auto-start section) which automatically restarts the proxy.

License

MIT

Credits

Built with the Claude Agent SDK by Anthropic.