Sonnet[1m] requires extra-usage even on MAX 20x subscription

On a Claude MAX 20x subscription, selecting claude-sonnet-4-6[1m] via /model and sending any prompt returns:

API Error: Extra usage is required for 1M context · run /extra-usage to enable, or /model to switch to standard context

This is one of two things, and either way it needs addressing:

1. A bug — Sonnet 1M should be usable on MAX 20x without opting into extra-usage, and the gating check is misfiring.
2. An undocumented pricing/packaging change — Sonnet 1M has been moved behind /extra-usage for MAX 20x subscribers. If so, no Claude Code changelog, release notes, or subscription page I can find mentions this change. Subscribers have no way to learn about it except by hitting this error.

Please clarify which it is, and if (2), document the change somewhere discoverable (changelog + /model picker + subscription description).

Repro

1. MAX 20x subscription, extra-usage disabled.
2. /model → select claude-sonnet-4-6[1m].
3. Send any prompt.
4. Error above.

Environment

• Platform: Linux
• Subscription: Claude MAX 20x