Anthropic Ships Claude Sonnet 5, Pitching Cheaper Autonomous Agents

Anthropic released Claude Sonnet 5 on June 30, making it the default model on the Free and Pro tiers and, according to the company, its most agentic Sonnet so far. On SWE-bench Verified, Anthropic reports a score of 92.4%. On Terminal-Bench 2.1 it cites 80.4% for Sonnet 5, compared with 74.6% for the larger Opus 4.8 and 67.0% for Sonnet 4.6. That is an unusual case of a mid-tier model scoring higher than a flagship on an agentic benchmark.

The commercial argument is cost. TechCrunch described the launch as a cheaper way to run agents. Introductory pricing is $2 per million input tokens and $10 per million output tokens through August 31, rising afterward to $3 and $15. Anthropic's central claim is that Sonnet 5 can run autonomously at a level that until recently required larger and more expensive models, and engineers should test that claim on their own workloads.

These figures come from Anthropic's own release and third-party writeups, not from independent reproduction. Scores on SWE-bench Verified and Terminal-Bench are sensitive to scaffolding, retries, and harness configuration, so a headline score does not translate directly to a production task without measurement on real code repositories.