Hi Simon,
Composer 1 will be completely retired on March 16, 2026, it will no longer be available as a selectable model on any plan. As the email states, the capacity is being reallocated to serve Composer 1.5, so Composer 1 will not remain available in any form after that date.
All users currently using Composer 1 will be automatically moved to Composer 1.5, which draws from the Auto + Composer usage pool and includes significantly more usage.
Let me know if you have any other questions!
Best,
Mohit