Vibe Check: Sonnet 5.5 Finds Its Place in Claude’s Crowded Family

So why choose Sonnet 5.5? After a week of testing, we think its strongest case isn’t as a substitute for Opus, but as Opus’s companion. At low and medium effort, Sonnet 5.5 is fast, inexpensive, capable, and responsive to direction—well suited to brainstorming, prototyping, design work, and other iterative jobs where you stay involved. When the work becomes long-running or demands high effort, Opus is usually the better handoff.

vs Opus, but this is how I use it: for iterative, quick work, especially design, prototyping, and product work. It’s also nice for quick background jobs. Run it on low or medium effort. Don’t run it on high or extra-high. If your task needs that much effort, move to Opus. Same for long-running tasks. Opus is still a bit more token efficient, and that adds up over a long run.

Nishida

“Sonnet 5.5 cooks! Low and medium are my new daily drivers for design work. It’s a cheaper option with surprisingly great output and it’s fast, which is super important for design iteration. Low and medium can run for surprisingly long stretches depending on your prompt, so you’ll want to be careful there. Max and ultracode effort created incredible results, too, but at that point, you might as well reach for Opus 5.5.”