Anthropic releases Claude Sonnet 5.5 as a cheaper follow-up

Anthropic releases Claude Sonnet 5.5 as the second model in its Claude 5.5 lineup, arriving less than a week after Opus 5.5. The company says the mid-tier model runs more than 30 percent faster than Sonnet 5, costs up to 30 percent less per task, and targets everyday work such as bug fixes, documents, slides, and spreadsheets.

That launch marks a clear then-and-now moment for Anthropic's mid-tier line: Sonnet 5 is the baseline, and Sonnet 5.5 is the follow-up pitched as both quicker and cheaper for most work. For readers tracking how AI products age in public, the story sits neatly alongside other Nostalgia: Then & Now coverage of tech that refreshes a familiar name rather than inventing a new one.

According to Mashable's report on Anthropic's announcement, Sonnet 5.5 is framed as a lower-cost complement to Opus 5.5—not a replacement for it.

Key Takeaways

• Anthropic releases Claude Sonnet 5.5 less than a week after Opus 5.5, as the second Claude 5.5 family model.
• Anthropic says Sonnet 5.5 runs more than 30% faster than Sonnet 5 and can cost up to 30% less per task.
• List pricing matches Sonnet 5, with input and output rates half of Opus 5.5; lower per-task cost is tied to fewer tokens.
• The model is available now across Anthropic's platforms, including AWS, Google Cloud, and Microsoft Azure, via the API as claude-sonnet-5-5.
• Claude Haiku 5.5 is expected in the coming weeks, per Anthropic.

What did Anthropic just launch with Claude Sonnet 5.5?

Anthropic just released Claude Sonnet 5.5, the second model in its Claude 5.5 family. It arrives less than a week after Claude Opus 5.5, continuing a rapid cadence rather than a long quiet stretch between versions.

In Anthropic's description, Sonnet 5.5 is a clear upgrade over Sonnet 5. The company positions it for well-scoped everyday tasks: fixing bugs and producing documents, slides, and spreadsheets. That is a narrower brief than the open-ended work Anthropic still assigns to Opus.

Anthropic also said Claude Haiku 5.5 will arrive in the coming weeks, signaling that Sonnet 5.5 is a mid-line installment in a broader 5.5 rollout, not a one-off refresh.

How does Sonnet 5.5 stack up against Sonnet 5 and Opus 5.5?

Then: Sonnet 5. Now: Sonnet 5.5, which Anthropic says runs more than 30 percent faster and costs up to 30 percent less for most work. On Anthropic's GDPval-AA v2.1 benchmark—measuring real-world work across 44 occupations—Sonnet 5.5 scored 1,844. That is two points behind Opus 5.5 and about 400 points ahead of Sonnet 5.

Anthropic reported that Sonnet 5.5's top score edges out Opus 5.5's, though Opus 5.5 scored higher at every other effort level the company charted. The company also said Sonnet 5.5 is the first Sonnet model to beat Pokémon Red while working only from screenshots—an unusual public proof point for a mid-tier model.

Anthropic cautioned that benchmarks capture only part of a model's abilities. Its own testing and outside testing both found Opus 5.5 still clearly stronger at complex, open-ended work. In other words, the then-and-now upgrade is strongest on speed, cost, and scoped tasks—not a claim that Sonnet now owns every Opus lane.

Early testers pointed to efficiency. In Anthropic's press release, Slack principal engineer Curtis Allen said Sonnet 5.5 beat Sonnet 5 on nearly all of Slack's offline Slackbot evaluations, finishing in fewer steps and with about 14 percent fewer output tokens.

How much does Claude Sonnet 5.5 cost, and where can you try it?

Pricing is the same as Sonnet 5. Anthropic says the input and output rates are half of Opus 5.5's. The lower per-task cost, the company argues, comes from the model needing fewer tokens to finish the same work—not from a cut to the list rate versus Sonnet 5.

Sonnet 5.5 is available now on all of Anthropic's platforms, including Amazon Web Services, Google Cloud, and Microsoft Azure. Developers can access it via the API as claude-sonnet-5-5, with zero data retention.

One migration detail matters for teams already on Sonnet: developers who run Sonnet with thinking off must switch to a new between_tools setting before migrating. That is a practical "now" change on top of the model swap itself.

What safeguards arrive with Sonnet 5.5?

Anthropic said Sonnet 5.5's cybersecurity capabilities are comparable to Opus 5's. For that reason, it is the first Sonnet model to ship with cyber safeguards similar to those on Opus 5.5. Higher-risk cybersecurity requests will visibly fall back to Sonnet 5, while routine bug-fixing is unaffected.

Biology safeguards are unchanged from Sonnet 5. Organizations can apply to the Life Sciences Verification Program for broader access. Sonnet 5.5 is also the first Sonnet model to launch with classifiers designed to block distillation attacks, in which bad actors extract a model's capabilities at scale.

On Anthropic's automated behavioral audit of roughly 1,850 scenarios, Sonnet 5.5 matched or improved on Sonnet 5 on most alignment measures. Opus 5.5 still performed slightly better overall. The company acknowledged that no set of evaluations catches every failure.

Put together, Anthropic releases Claude Sonnet 5.5 as a faster, cheaper mid-tier step after Opus 5.5—not as a full handoff. Compared with Sonnet 5, the company is selling speed, token efficiency, platform availability, and tighter cyber controls, while still pointing heavy, open-ended work toward Opus.