From the source
Opus 4.5 is described as more polished, faster, and often cheaper due to fewer token-wasting mistakes and higher cache hit rate.
It is limited to a 200k token context window.
Opus 4.5: Better, Faster, Often Cheaper
Amp switched its main model in smart mode to Claude Opus 4.5, replacing Gemini 3.
Capability change
From the source
Claude Opus 4.5 is the new main model in Amp's smart mode, two days after we shipped it for you to try out.
ampcode.com
