Claude Sonnet 4.5 (Anthropic)

Claude Sonnet 4.5 was released by Anthropic on September 29, 2025, positioned by the company as their strongest coding model and the strongest option for building complex agents. Anthropic also described it as their best model at using computers and highlighted substantial gains in reasoning and math at launch, framing the release around modern work where code drives every application and tool. The model sits in the Claude Sonnet family, carrying forward Anthropic's assistant-oriented design while pushing further into autonomous, multi-step task execution.

In practical terms, Claude Sonnet 4.5 is aimed at developers and teams building agentic systems, long-running automations, and tools that need to operate across applications. Anthropic shipped it alongside companion updates such as Claude Code checkpoints with rollback, a refreshed terminal interface, a native VS Code extension, and API-level context editing and memory tooling that help agents sustain longer and more complex workflows. The result is a model tuned for sustained reasoning, tool orchestration, and computer-use scenarios where an agent must navigate software environments rather than just answer isolated questions.