Claude Sonnet 5.5 is available on the free plan, unlike Opus 5.5

Anthropic released Claude Sonnet 5.5 on Monday. A week earlier, Opus 5.5 went to paying subscribers only, and free accounts did not get it. Sonnet 5.5 is different. Anthropic's product page says "anyone can chat with Claude using Sonnet 5.5 on Claude.ai, available on web, iOS, and Android," and developer Simon Willison has already tried the new model on a free account. On a paid account in Germany, Sonnet 5.5 was listed in the model picker on Wednesday.

Faster output, same per-token price

According to Anthropic, Sonnet 5.5 generates output more than 30% faster than Sonnet 5 and costs up to 30% less per task. Prices have not changed. Developers still pay $2 per million input tokens and $10 per million output tokens, but the model "typically needs far fewer tokens to do the same work," Anthropic says. In head-to-head runs, it also batched tool calls together more often than Sonnet 5. On several benchmarks, Sonnet 5.5 at Low or Medium effort beats the best Sonnet 5 score for about a tenth of the cost per task.

Medium effort by default in the apps

"In Claude Code and our apps, the default effort is set to Medium, while the Claude Platform defaults to High," Anthropic writes. Paid accounts can raise the effort level in the model picker, which makes answers more thorough and slower. The picker there also lists Fable 5.1, Opus 5.5 and Haiku 4.5. Haiku 5.5 is due in the coming weeks.

Security requests fall back to Sonnet 5

VentureBeat points out that Sonnet 5.5 is the first Sonnet model to launch with cybersecurity safeguards modeled on those of Anthropic's most capable systems. Anthropic says the model's cyber capabilities are a large improvement over Sonnet 5. Finding and fixing bugs in your own code works as before, but "higher-risk cybersecurity tasks will visibly fall back to Sonnet 5." Anthropic takes the same approach with Opus 5.5, which hands sensitive biology and cybersecurity questions to Opus 4.8. On the free plan, Sonnet 5.5 is now the most capable Claude model. OpenAI made its new GPT-6 Luna model available to free users last week, but only in the desktop app.