Claude Sonnet

Claude Sonnet is Anthropic’s mid-tier large language model, sitting between the smaller Haiku and the larger Opus in their model family, and balancing output quality against cost and latency.

Anthropic releases models in three tiers: Haiku (fast, cheap, good for classification and quick edits), Sonnet (the production workhorse for most writing and reasoning), and Opus (highest quality, slower, more expensive). Many AI marketing tools use Sonnet for content generation and Haiku for evaluation/scoring — the two-model split lets the tool produce high-quality drafts while keeping per-generation cost manageable.

Sonnet versions iterate over time (Claude 3 Sonnet, Claude 3.5 Sonnet, Claude Sonnet 4, etc.), with each release typically improving instruction following, voice consistency, and reasoning. Tools that pin to an old version may produce worse output than the same prompts against a newer release.

The model behind the AI matters less than how the tool conditions it, but it does matter. Tools using current Sonnet typically produce more consistent voice work than tools using older or smaller models at the same prompting depth.