Anthropic Ships Claude Sonnet 5
Claude Sonnet 5 brings near-Opus performance to a lower-priced Sonnet model. It adds stronger self-checking behavior, agentic coding performance close to Opus 4.8, a 1 million token context window, and a 128,000 token output limit. The model is available now as claude-sonnet-5 in the Claude API and is the new default for Free and Pro plans.
- Anthropic positions the model as the most agentic Sonnet yet, with planning, browser use, terminal use, and longer autonomous runs.
- Safety testing found lower undesirable behavior than Sonnet 4.6 overall, including lower hallucination and sycophancy rates.
- The launch includes cyber safeguards by default because Sonnet 5 is stronger than its predecessor on some cybersecurity-related tasks.
