The Anthropic provider in BYOK only accepts an API key

The Anthropic provider in BYOK only accepts an API key (sk-ant-) against api.anthropic.com. That means it can only draw on Anthropic Console credits, which are a separate prepaid balance from a Claude Pro/Max subscription, the two don't transfer.

Please add OAuth / subscription-based auth for the Anthropic provider, the same way Claude Code authenticates via `claude login`. Third-party apps that authenticate against a Claude subscription through the Agent SDK currently draw on subscription usage limits, so the mechanism exists.

As it stands, a paying Claude subscriber has no way to use their own plan in Copilot and has to fund a second balance to do the same work (e.g. to use Fable consumption credits).

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| Field | Value |
| --- | --- |
| App version | 1.1.12 |
| OS | Windows 10.0.26200 |
| Theme | GitHub |
| Path | /chat |
| Tenure | Week 15 |

Comienza rastreando el proveedor BYOK Anthropic y comparando su flujo de API key con la forma en que Claude Code se autentica mediante `claude login`. Revisa el comportamiento de autenticación del Agent SDK descrito en el issue. Se considera terminado cuando la autenticación basada en suscripción de Anthropic funciona para los suscriptores de Claude sin requerir un saldo separado de API key.

Escrito por el modelo de indexación a partir del texto del issue.