Anthropic finally, officially launches Claude Sonnet 5

Anthropic released Claude Sonnet 5 on Tuesday, confirming months of speculation about an upgrade to its mid-tier AI model.

According to the company's official announcement, the new model is designed to be its "most agentic Sonnet model yet." Meaning it is capable of planning, using tools like browsers and terminals, and operating autonomously — all at a level previously reserved for larger, pricier systems.

Anthropic says Sonnet 5 is a substantial improvement on its predecessor, Sonnet 4.6, across reasoning, coding, and knowledge-work benchmarks, and performs close to the company's flagship Opus 4.8 model while costing significantly less to run.

And in an industry increasingly plagued by sticker shock over the price tokens, Sonnet offers a brief respite. The model launches with introductory pricing of $2 per million input tokens and $10 per million output tokens through August 31, after which the standard pricing of $3 per million input tokens and $15 per million output tokens takes effect.

On safety, Anthropic reports Sonnet 5 shows lower rates of hallucination, sycophancy, and other undesirable behaviors than its predecessor, along with improved resistance to prompt-injection attacks. The company noted the model's cybersecurity capabilities remain well below those of its Opus-class and Mythos-class systems, and Sonnet 5 has launched with cyber safeguards enabled by default as a precaution.

Notably absent from Anthropic's announcement: specific figures on those improvements in hallucination rates. The company offers only a general claim of "lower rates" compared to Sonnet 4.6, rather than benchmark data.

The release also made no mention of the model's energy consumption or environmental footprint, a real problem for the AI industry as models grow more capable and computationally intensive.

Sonnet 5 is now available across all Claude plans, including Free, Pro, Max, Team, and Enterprise tiers, as well as via Claude Code and the Claude Platform via the API under the model name claude-sonnet-5.

The release follows weeks of anticipation in the tech press. As we reported in February, reports have been circulating for some time that Anthropic was preparing a Sonnet update positioned to rival Opus-tier performance at a steep discount — a forecast that tracks with Tuesday's official rollout.