Claude Sonnet 5

Introducing Claude Sonnet 5

Claude Sonnet 5 is built to be the most agentic Sonnet model yet. It can make plans, use tools like browsers and terminals, and run autonomously at a level that, just a few months ago, required larger and more expensive models.

For many developers, the agentic AI era began with Sonnet-class models: Claude Sonnet 3.5, 3.6, and 3.7 were the first models that showed impressive skills in coding and tool use. More recently, though, the clearest gains in agentic capabilities have been in our Opus-class models.

Sonnet 5 narrows the gap: its performance is close to that of Opus 4.8, but at lower prices. It’s a substantial improvement over its predecessor, Sonnet 4.6, on important aspects of agentic performance like reasoning, tool use, coding, and knowledge work:

Our safety assessments found that Sonnet 5 shows an overall lower rate of undesirable behaviors than Sonnet 4.6, and is generally safer to use in agentic contexts. Evaluations also show that it has a much lower ability to perform cybersecurity tasks than our current Opus models.

From today, Claude Sonnet 5 is available across all plans: it is the default model for Free and Pro plans, and is available to Max, Team, and Enterprise users. It’s also available in Claude Code and on the Claude Platform, where it launches with introductory pricing of $2 per million input tokens and $10 per million output tokens through August 31, 2026, after which it will be priced at $3 per million input tokens and $15 per million output tokens. Developers can use claude-sonnet-5

via the Claude API.

Working with Claude Sonnet 5

The charts below compare the performance of Sonnet 5 with Sonnet 4.6 and Opus 4.8 at different effort levels on the agentic search evaluation BrowseComp and the computer use evaluation OSWorld-Verified. Sonnet 5 (orange line) is a strict improvement over Sonnet 4.6 (gray line) and covers a much wider range of cost-performance options than Opus 4.8 (yellow line). It provides substantially improved cost efficiency at medium effort; its higher-effort performance can match Opus 4.8 on some tasks. Between Sonnet 5 and Opus 4.8, users can adjust the effort level to find the right balance of cost and performance.

Feedback from our early access partners has been consistent: Sonnet 5 is much more agentic than its predecessors. Testers described how it finishes complex tasks where previous Sonnet models would stop short, how it checks its own output without explicitly be