What happened
Anthropic released Claude Sonnet 5 on June 30, calling it its most agentic mid-tier model to date. It became the default model for Free and Pro users and is available across the Max, Team and Enterprise plans.
Introductory pricing is set at $2 per million input tokens and $10 per million output tokens through August 31, rising to $3 and $15 afterward. The model scores 63.2% on an agentic coding benchmark against Opus 4.8's 69.2%, while slightly outperforming Opus 4.8 on a knowledge-work benchmark. Anthropic also highlighted lower rates of undesirable behavior, hallucination and sycophancy, along with better resistance to prompt injection.
Why it matters
A mid-tier model that lands close to the flagship on many tasks, at a fraction of the cost, changes the math for running agents at scale. Anthropic prices Sonnet 5 below Opus 4.8, GPT-5.5 and Gemini 3.1 Pro.
The safety improvements matter because more capable agents are being handed longer, less supervised tasks. Better prompt-injection resistance directly reduces one of the main risks in autonomous workflows.
MintedBrain take
For most day-to-day agent work, the practical question is where a cheaper model becomes good enough. Sonnet 5 looks like a sensible default; reserve Opus for the harder coding jobs where the benchmark gap actually shows up.
Discussion
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