pi-anthropic-oauth

Use Claude Pro/Max in Pi with browser OAuth.

[!IMPORTANT] This release requires Pi 0.80.8 or later in the 0.80.x release line.

Features

• Claude Pro/Max login from /login
• Automatic token refresh
• Claude Code-compatible OAuth headers and prompt shaping
• No Anthropic API key needed
• Uses Pi's Anthropic model registry
• Adds Claude Opus 4.8 and Claude Fable 5 by default
• Auto-creates ~/.Claude Code → ~/.pi symlink when missing

Quick start

pi install npm:pi-anthropic-oauth

Start Pi, then run Pi's login command:

/login

Choose:

Claude Pro/Max

Complete the browser login. After login, select an Anthropic model in Pi.

When the extension is active, /login includes Claude Pro/Max and Anthropic models show (sub) after OAuth login.

Update with:

pi update npm:pi-anthropic-oauth

[!NOTE] Anthropic auth changes are closely monitored for quick compatibility updates.

System prompt rewriting

When using Claude Pro/Max OAuth, the extension prepends Claude Code identity text and rewrites standalone Pi / pi references in Pi's system prompt to Claude Code. The rewrite mode defaults to aggressive:

PI_ANTHROPIC_OAUTH_REWRITE_MODE=aggressive

Other modes are opt-in and avoid rewriting some technical strings such as paths, package names, or repository names. If OAuth starts failing, switch back to aggressive.

Available modes:

| Mode | Behavior | | ---------------- | ----------------------------------------------------------------------------------------------------------- | | aggressive | Default. Replaces standalone Pi / pi wherever the word-boundary pattern matches. | | path-safe | Avoids replacing Pi / pi immediately after / or \, preserving path segments like /srv/dev/pi-foo. | | technical-safe | Avoids replacing Pi / pi next to common technical-token separators: /, \, ., @, :, _, -. | | custom | Uses PI_ANTHROPIC_OAUTH_REWRITE_PATTERN as the replacement regex. |

Custom patterns can be a regex source or a JavaScript-style regex literal. The g flag is added automatically when omitted:

PI_ANTHROPIC_OAUTH_REWRITE_MODE=custom
PI_ANTHROPIC_OAUTH_REWRITE_PATTERN='(?<![/\\])\b[Pp]i\b'
# or
PI_ANTHROPIC_OAUTH_REWRITE_PATTERN='/\bpi\b/gi'

There is no separate off mode. If you need to disable rewriting entirely, use a custom pattern that never matches, such as (?!). Disabling or weakening the rewrite may affect OAuth compatibility.

Extra models

To add another Anthropic model, create ~/.pi/agent/models.json:

{
  "providers": {
    "anthropic": {
      "baseUrl": "https://api.anthropic.com",
      "apiKey": "unused",
      "api": "anthropic-messages",
      "models": [
        {
          "id": "your-model-id",
          "name": "Your Model Name"
        }
      ]
    }
  }
}

[!NOTE] Opus 4.8 and Fable 5 are included in Pi's built-in Anthropic model catalog.

Pi requires baseUrl, apiKey, and api when defining custom models in models.json. With this extension, requests normally authenticate through Claude Pro/Max OAuth after /login, so apiKey is only a placeholder to satisfy Pi's config requirements and does not need to be a valid Anthropic API key.

Do not use a fake sk-ant-oat... value as the placeholder. If OAuth login has not completed, Pi may try to use that fake token and Anthropic will return 401 Invalid bearer token. Use a harmless placeholder such as "unused", then run /login and choose Claude Pro/Max.

Troubleshooting

• Run /login with no arguments, then choose Claude Pro/Max.
• If local callback login does not complete, paste the final callback URL or code#state when prompted
• If you see 401 Invalid bearer token, remove any fake sk-ant-oat... placeholder from ~/.pi/agent/models.json and log in again
• If something breaks, please open an issue with your Pi version, extension version, and error output

License

MIT