Claude Sonnet 5

• 🆕 Anthropic's first Sonnet of its latest generation, released 2026.
• 📏 1M-token context window, up to 128k output tokens.
• 🧠 Adaptive thinking on by default; manual extended thinking removed.
• 🔧 Built for coding, tool use, and multi-step autonomous agents.
• 👁️ Retains vision, document understanding, function calling, web search.
• 💬 Drop-in upgrade for Sonnet 4.6 across Claude plans and API.
• 🎯 Anthropic reports gains over 4.6 in reasoning, coding, knowledge work.

Anthropic

Anthropic PBC is an American artificial intelligence company headquartered in San Francisco. Structured as a public benefit corporation, the lab develops large language models under the Claude name, with a research emphasis on building reliable, steerable,…

Claude Sonnet 5 is the newest entry in Anthropic's mid-tier Sonnet line and the first Sonnet model of the company's latest generation, positioned for coding, agents, and professional work at scale. It succeeds Claude Sonnet 4.6 and, further back, Claude Sonnet 4.5, while sitting below the flagship Claude Opus 4.8.

Against its direct predecessor, Anthropic describes Sonnet 5 as a substantial improvement in reasoning, tool use, coding, and knowledge work. The platform docs note it is a drop-in upgrade for Sonnet 4.6, with adaptive thinking now enabled by default and manual extended thinking and custom sampling parameters removed. It keeps the 1M-token context window, though each token now covers slightly less text on average.

The stated design goal is to bring near-Opus quality to a lower-priced Sonnet: Anthropic says Sonnet 5 approaches Opus 4.8 on many tasks while covering a wider cost-performance range.

Sonnet 5 is available across Claude plans, in Claude Code, and via the Claude Platform, Amazon Bedrock, Google Cloud, and Microsoft Foundry.