---
title: "Introducing Claude Sonnet 5"
description: "Claude Sonnet 5 is introduced as an agentic Sonnet model that plans, uses browser and terminal tools, and operates autonomously. The post says it approaches Opus 4.8 performance at lower prices while improving on Sonnet 4.6 in reasoning, tool use, coding, and knowledge work. Comparisons on BrowseComp and OSWorld-Verified across effort levels show a wider cost-performance range, with higher-effort results matching Opus 4.8 on some tasks. Safety assessments found lower overall undesirable behavior, hallucination, and sycophancy rates than Sonnet 4.6, while default cyber safeguards address dangerous usage; the model is available across all plans and via the Claude API for $2 per million input tokens and $10 per million output tokens."
---

# Introducing Claude Sonnet 5

[Anthropic](https://yomu.fyi/company/anthropic) · Aug 10, 2026

**Type:** Announcement

## Summary

Claude Sonnet 5 is introduced as an agentic Sonnet model that plans, uses browser and terminal tools, and operates autonomously. The post says it approaches Opus 4.8 performance at lower prices while improving on Sonnet 4.6 in reasoning, tool use, coding, and knowledge work. Comparisons on BrowseComp and OSWorld-Verified across effort levels show a wider cost-performance range, with higher-effort results matching Opus 4.8 on some tasks. Safety assessments found lower overall undesirable behavior, hallucination, and sycophancy rates than Sonnet 4.6, while default cyber safeguards address dangerous usage; the model is available across all plans and via the Claude API for $2 per million input tokens and $10 per million output tokens.

## Context

The post positions Sonnet 5 as a response to Opus-class models' stronger recent gains in agentic capabilities and as a lower-cost option whose performance approaches Opus 4.8. It also describes demand for more capable, sustained automation across coding, tool use, computer workflows, and knowledge work.

## Approach / What changed

Sonnet 5 combines planning, browser and terminal tool use, autonomous operation, and selectable effort levels. The post compares it with Sonnet 4.6 and Opus 4.8 on agentic and computer-use evaluations, and launches it with default cyber safeguards that detect and block dangerous usage in real time.

## Takeaways

- Sonnet 5 is described as a substantial improvement over Sonnet 4.6 in reasoning, tool use, coding, and knowledge work, with performance close to Opus 4.8 at lower prices.
- On BrowseComp and OSWorld-Verified, selectable effort levels provide a wider cost-performance range; higher effort can match Opus 4.8 on some tasks.
- Sonnet 5 has lower overall undesirable behavior, hallucination, and sycophancy rates than Sonnet 4.6, while default cyber safeguards address its somewhat stronger performance on dangerous cyber tasks.

**Tags:** [AI Agents](https://yomu.fyi/topic/ai-agents), [Claude](https://yomu.fyi/topic/claude), [Model Evaluation](https://yomu.fyi/topic/model-evaluation), [Security](https://yomu.fyi/topic/security)

- Source: [Anthropic](https://www.anthropic.com/news/claude-sonnet-5)
- Source URL: https://www.anthropic.com/news/claude-sonnet-5
- Ingested by Yomu: 2026-09-09T11:36:43.225Z

[Read original post](https://www.anthropic.com/news/claude-sonnet-5)