What changed
The Dial was replaced by a per-thread model and effort selector that can be changed mid-thread and shows the billing source. The old settings map to GLM-5.3-Flash (low), Claude Opus 5.5 (medium), GPT-6 Astra (high) and Claude Fable 5.2 (ultra). Switching mid-thread re-reads the thread without cache, so it costs more.
Who it affects
All Amp users.
What to do
Set which model new threads start on in Settings, and avoid switching models mid-thread unless you need to.