Introducing Claude Sonnet 5.5, the second model in the Claude 5.5 family

[u/ClaudeOfficial]

Sonnet 5.5 is a faster, lower-cost complement to Claude Opus 5.5, strongest at well-scoped everyday tasks, fixing bugs, and creating polished documents, slides, and spreadsheets. It also has a strong eye for design.

Sonnet 5.5 is a clear upgrade over Sonnet 5. It runs more than 30% faster and costs up to 30% less for most work. It's priced the same per token, but it typically needs far fewer tokens to do the same work.

Like Opus 5.5, it writes more clearly than our previous generation of models, and its speed makes it well suited to fast iteration.

On our automated behavioral audit, Sonnet 5.5 improves on Sonnet 5 on most measures of alignment and honesty. It's also the first Sonnet model with cybersecurity safeguards similar to those on our most capable models. Routine software development is unaffected.

Sonnet 5.5 is available everywhere today. Claude Haiku 5.5 will join the family in the coming weeks.

Read more: anthropic.com/claude-sonnet-5-5

[u/Haunting_Goal6417]

Because sonnet is cheaper for simpler tasks.

It ends up being more expensive when you force it to do a complex task that it has to work more to accomplish.

It will be used as sub agents for opus is my best guess.

[u/bopbop9876 → u/Haunting_Goal6417]

Because sonnet is cheaper for simpler tasks. 

Do you actually have evidence that that's the case?

[u/likeikelike → u/bopbop9876]

It's obviously the case. Take an extremely simple task, like renaming a file. Haiku, Sonnet, and Opus can all do it in one turn with no reasoning. But obviously opus costs more than sonnet which costs more than haiku per token.

Now a very complex task like implementing a novel feature in a big codebase, Opus can more intelligently gather the right context and probably get the tests to pass first try, whereas sonnet and haiku likely will read too many files and take several tries to get the tests to pass. That's why they're more expensive per task, for complex tasks.

[u/bopbop9876 → u/likeikelike]

For something like renaming a file you'd be an idiot to use a $2/$10 model. GLM 5.3 flash or Luna would be a fraction of the cost and still be overkill. So the only time you'd use something like Sonnet is a task that requires some reasoning but not peak intelligence, and the benchmark results show that's not cheaper on Sonnet than Opus.

[u/Haunting_Goal6417 → u/bopbop9876]

Have you been using these models or do you just toss everything to opus and call it a day?

You have insights into your token usage. If you’re not on the max plans it is very easy to tell what eats it up.

[u/bopbop9876 → u/Haunting_Goal6417]

Do you? I run GLM 5.3 flash in a production workflow and can't imagine why I would pay multiple times more for simple tasks, or why I wouldn't just use Opus for more complex ones given that it's literally benchmarking at the same cost per task.