Claude Sonnet 5 Is Not Frontier But Has Its Uses

Anthropic released Claude Sonnet 5 today—a new model that's faster and cheaper, but not frontier. Fable 5 remains the cutting edge. Sonnet 5 costs three dollars per million input tokens compared to five dollars for Opus 4.8, and it's noticeably faster, which helps you stay in a flow state when working quickly. The catch: it's less capable on hard problems. It does excel at one thing—handling prompt injection attempts in coding environments better than previous models. According to LessWrong's Zvi, Sonnet 5 is useful for rapid iteration, simple tasks, and certain AI agent scenarios where its robustness edges out Opus. For most developers' daily work, though, the speed and cost savings don't justify the capability trade-off unless you're doing lots of light queries.

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