[!WARNING] This plugin comes with no guarantees. You might be banned for breaking the TOS, you might not be. I don't work at Anthropic, nor am I an attorney.
Use your best judgment and don't try to abuse the subscriptions. Plugins like oh-my-openagent are known to trigger bans. Please be careful when using Ralph loops or insanely heavy usage patterns.
[!IMPORTANT] If you are seeing issues, please try to
rm -rf ~/.cache/opencodeand check youropencode.jsonconfig to make sure you're on the latest version.Try this FIRST before making an Issue. Thanks!
An OpenCode plugin that provides Anthropic OAuth authentication, enabling Claude Pro/Max users to use their subscription directly with OpenCode.
Add the plugin to your OpenCode configuration:
{
"plugin": ["@ex-machina/opencode-anthropic-auth"]
}
[!TIP] It is STRONGLY advised that you pin the plugin to a version. This will keep you from getting automatic updates; however, this will protect you from nefarious updates.
This holds true for ANY OpenCode plugin. If you do not pin them, OpenCode will automatically update them on startup. It's a massive vulnerability waiting to happen.
{
"plugin": ["@ex-machina/opencode-anthropic-auth@1.8.0"]
}
The plugin provides three authentication options:
claude.ai for Pro/Max subscribers. Uses your existing subscription at no additional API cost.console.anthropic.com that creates an API key on your behalf.The plugin supports the following environment variables:
| Variable | Description |
|---|---|
ANTHROPIC_BASE_URL |
Override the API endpoint URL (e.g. for proxying). Must be a valid HTTP(S) URL. |
ANTHROPIC_INSECURE |
Set to 1 or true to skip TLS certificate verification. Only effective when ANTHROPIC_BASE_URL is also set. |
For Claude Pro/Max authentication, the plugin:
The Anthropic API for Max subscriptions has specific requirements for the system prompt to identify as Claude Code. The plugin rewrites the system prompt on each request using an anchor-based approach that minimizes what gets changed:
github.com/anomalyco/opencode, opencode.ai/docs) is removed entirely. This is resilient to upstream rewording — as long as the anchor URL appears somewhere in the paragraph, the removal works regardless of surrounding text changes.Everything else in the system prompt is preserved: tone/style guidance, task management instructions, tool usage policy, environment info, skills, user/project instructions, and file paths containing "opencode". The sanitized system prompt is structured as three blocks in system[]: the billing header, the Claude Code identity line, and the remaining system content.
Use bun run dev to test plugin changes locally without publishing to npm:
bun run dev
This does three things:
.opencode/plugins/ so OpenCode loads it as a local plugintsc --watch for automatic rebuilds on source changesAfter starting the dev script, restart OpenCode in this project directory to pick up the local build. Any edits to src/ will trigger a rebuild — restart OpenCode again to load the new version.
Ctrl+C stops the watcher and cleans up the symlink. If the process was killed without cleanup (e.g. kill -9), you can manually remove the symlink:
bun run dev:clean
[!NOTE] If you have the npm version of this plugin in your global OpenCode config, both will load. The local version takes precedence for auth handling.
This project uses changesets for versioning and publishing. See the changeset README for more details.
bun change # create a changeset describing your changes
When changesets are merged to main, CI will automatically open a release PR. Merging that PR publishes to npm.
MIT
$ claude mcp add opencode-anthropic-auth \
-- python -m otcore.mcp_server <graph>