Claude Sonnet 5

Overview

Anthropic's current mid-tier model, released June 30, 2026. Claude Sonnet 5 brings near-Opus coding and agentic capability to the workhorse tier, with a 1M token context window and adaptive thinking on by default.

Why it matters

Sonnet 5 is the default deployment choice for most Claude workloads: it reaches what was Opus-tier quality on coding and agent tasks a generation ago, at $3/M input (with introductory $2/M pricing through August 2026). For engineering leaders, the significance is that the 'good enough for production' bar keeps moving down-market — capability that justified premium pricing in 2025 is now standard at the mid tier. The launch also continued Anthropic's API consolidation: adaptive thinking is the default and fixed thinking budgets are gone, so teams upgrading from Sonnet 4.x should re-baseline token counts and budgets rather than assuming a drop-in swap.