Concurrent multi-agents: Meh. Haven't found a use for it yet, just like background agents. Guess im just not at that level. It sounds like you can run multiple agents for the same prompt and compare/pick the best result, and/or have them work on different things simulatenously and then go through and approve all diffs together in a single place. Which sounds potentially neat in theory but also like a nightmare in practice, as you said.

New model: wonder how it fares against Claude 4.5 sonnet. I'm guessing Composer1 is considered a premium model too.

Embedded browser: pretty nice, I like being able to open a browser tab without needing Chrome installed.