OpenCode plugin that uses your existing Claude Code credentials — no separate login needed.

Claude Code stores OAuth tokens in the macOS Keychain (or ~/.claude/.credentials.json on other platforms). This plugin reads those tokens and writes them to OpenCode's ~/.local/share/opencode/auth.json (on Windows, it writes to both %USERPROFILE%\.local\share\opencode\auth.json and %LOCALAPPDATA%\opencode\auth.json to cover all installation methods), so you don't need to log in twice. It re-syncs every 5 minutes to pick up token refreshes. If a token is near expiry, it runs the Claude CLI to trigger a refresh.

• Claude Code installed and authenticated (run claude at least once)
• OpenCode installed

macOS is preferred (uses Keychain). Linux and Windows work via the credentials file fallback.

Paste this into your AI agent (Claude Code, Cursor, Copilot, etc.):

Fetch https://raw.githubusercontent.com/griffinmartin/opencode-claude-auth/main/installation.md and follow every step exactly as written.

npm install -g opencode-claude-auth

Then add to the plugin array in your opencode.json:

{
  "plugin": ["opencode-claude-auth"]
}

Just run OpenCode. The plugin syncs your Claude Code credentials to OpenCode's auth.json and refreshes them in the background.

The plugin checks these in order:

1. macOS Keychain ("Claude Code-credentials" entry)
2. ~/.claude/.credentials.json (fallback, works on all platforms)

Problem	Solution
"Credentials not found"	Run claude to authenticate with Claude Code first
"Keychain is locked"	Run security unlock-keychain ~/Library/Keychains/login.keychain-db
"Token expired and refresh failed"	The plugin runs claude CLI to refresh automatically. If this fails, re-authenticate manually by running claude
Not working on Linux/Windows	Ensure ~/.claude/.credentials.json exists. Run claude to create it
Keychain access denied	Grant access when macOS prompts you
Keychain read timed out	Restart Keychain Access (can happen on macOS Tahoe)

• Reads OAuth tokens from macOS Keychain (Claude Code-credentials entry) or ~/.claude/.credentials.json fallback
• Writes an anthropic entry to ~/.local/share/opencode/auth.json (on Windows, writes to both %USERPROFILE%\.local\share\opencode\auth.json and %LOCALAPPDATA%\opencode\auth.json) in OpenCode's native OAuth format
• Preserves other provider entries already in auth.json
• Re-syncs credentials every 5 minutes in the background
• When a token is within 60 seconds of expiry, runs claude CLI to trigger a refresh
• If credentials are unavailable or unreadable, the plugin disables itself and OpenCode continues without Claude auth

MIT