Claude Sonnet 4.5 (Vertex AI (Anthropic))

Claude Sonnet 4.5 is positioned by Anthropic as a frontier model purpose-built for software engineering and autonomous agent workflows, with the company calling it the strongest coding model in its lineup. It is described as the best model at using computers and shows substantial gains in reasoning and math compared to prior Claude generations. A defining capability is hybrid reasoning, allowing users to choose between fast answers for routine tasks and deeper, more deliberate analysis for complex problems—a design pattern that traces back through the Claude Sonnet lineage beginning with Claude 3.5. Anthropic also presents Claude Sonnet 4.5 as its most aligned frontier release to date, with broad improvements across alignment evaluations relative to earlier Claude models.

In benchmark terms, Anthropic reports state-of-the-art performance on SWE-bench Verified, a real-world software engineering evaluation that draws tasks from actual GitHub repositories and measures a model's ability to resolve genuine code issues within a codebase. This result underpins the model's emphasis on practical coding ability rather than purely academic exercises. The release ships alongside ecosystem upgrades intended to extend what the model can do in production: a native VS Code extension for Claude Code, checkpoints for rolling back agent progress, and a context editing plus memory feature in the Claude API that lets agents sustain longer, more complex work. Together these integrations make Claude Sonnet 4.5 a strong fit for teams building multi-step coding agents, automating developer workflows, or tackling multi-file refactors that require sustained context and tool use.