Gateway telemetry can authenticate to Google Cloud with auth.google, and the gateway model list flags 1M-context support

What

The gateway can forward telemetry (usage and performance data in the OpenTelemetry, or OTel, format) to other services listed under telemetry.forward_to. Those destinations used to send only fixed headers you wrote yourself.

• A forward_to entry can now set auth.google, including auth.google.service_account_json, to sign in with a Google service account.
• When it is set, the exporter fetches Google access headers, caches them per destination, removes any Authorization header and adds the Google ones before sending. Other headers you set are kept.
• auth.google requires an https googleapis.com URL and no Authorization header of your own.

Separately, the gateway's model list now marks models whose metadata has supports_1m_beta with supports1m: true. claude-sonnet-4-0, claude-sonnet-4-5, and any config whose environment sets CLAUDE_CODE_DISABLE_1M_CONTEXT are left out.

Why

You can send gateway telemetry straight to Google Cloud collectors without making tokens by hand or writing a helper for headers. The model list change lets gateway users see which models offer the 1M context window.