Claude Sonnet 4.5
Anthropic's most capable Sonnet-tier model at launch, tuned heavily for coding and computer use
Claude Sonnet 4.5, released on September 29, 2025, was Anthropic’s highest-scoring Sonnet-tier model on SWE-bench Verified at launch, reaching about 77.2 percent on the full 500-problem set with extended thinking enabled. Anthropic built it heavily around coding and computer use, and testers reported it staying focused on a single complex task for more than 30 hours without losing track of what it was doing. It added context awareness, meaning the model tracks how much of its context window remains during a long conversation and adjusts its behavior as it fills up, which matters for agents running long unattended sessions. It kept Sonnet’s $3/$15 per million token pricing and 200,000 token standard context window, with a 1 million token context window available in beta, making it Anthropic’s primary recommendation for coding agents and long-running automation through the rest of 2025.