Why Moltis Doesn’t Support Anthropic OAuth

A common request is browser-based OAuth login for Anthropic, similar to what Moltis offers for OpenAI Codex and GitHub Copilot. This page explains why that isn’t possible and what to do instead.

TL;DR

Anthropic does not offer an OAuth program for third-party tools. Their OAuth flow is locked to Claude Code and Claude.ai only. The only supported way to use Anthropic models in Moltis is with an API key from the Anthropic Console.

Background

Claude Code (Anthropic’s CLI) authenticates via an OAuth 2.0 PKCE flow against console.anthropic.com. The temporary OAuth token is then exchanged for a permanent API key through an internal endpoint (/api/oauth/claude_cli/create_api_key). The path segment /claude_cli/ signals this is a CLI-specific, internal endpoint — not a public API.

The client ID used by Claude Code (9d1c250a-…) is hard-coded for that single application. Anthropic does not provide a way to register new client IDs for third-party projects.

Anthropic’s Policy

In February 2026 Anthropic updated their Legal and Compliance page with an explicit restriction:

OAuth authentication (used with Free, Pro, and Max plans) is intended exclusively for Claude Code and Claude.ai. Using OAuth tokens obtained through Claude Free, Pro, or Max accounts in any other product, tool, or service — including the Agent SDK — is not permitted and constitutes a violation of the Consumer Terms of Service.

This isn’t just a policy statement — Anthropic deployed server-side enforcement in January 2026. OAuth tokens from consumer plans now return errors outside of Claude Code and Claude.ai:

“This credential is only authorized for use with Claude Code and cannot be used for other API requests.”

Several projects that attempted this approach — including Auto-Claude, Goose, and OpenCode — were forced to drop OAuth and switch to standard API keys.

What About Reusing the Claude Code Client ID?

Even if the OAuth flow and key creation technically succeed today, using Claude Code’s client ID from a different application:

Violates the Consumer Terms of Service (Section 3.7 — no automated access through bots or scripts except via official API keys).
Risks key revocation — Anthropic reserves the right to revoke credentials without prior notice.
Could break at any time — the client ID and internal endpoints are not part of a public, stable API surface.

How to Use Anthropic in Moltis

Go to console.anthropic.com and create an account (or sign in).
Navigate to Settings → API Keys and create a new key.
In Moltis, go to Settings → Providers → Anthropic and paste the key.

Alternatively, set the ANTHROPIC_API_KEY environment variable or add it to your moltis.toml:

[providers.anthropic]
enabled = true
api_key = "sk-ant-api03-..."

This is the method Anthropic officially recommends for all third-party integrations.

Will This Change?

If Anthropic introduces a developer OAuth program with client ID registration in the future, Moltis will adopt it. The generic infrastructure for OAuth-to-API-key exchange already exists in the codebase (the api_key_endpoint field on OAuthConfig), so adding support would be straightforward.

Moltis Documentation