Anthropic Unveils Claude Sonnet 4.5 – The Leading Coding Model and Powerful Agent Platform
Anthropic announced Claude Sonnet 4.5, touting it as the world’s best coding model and strongest for building complex agents, backed by top benchmark scores, enhanced domain knowledge, improved safety, unchanged pricing, and new features like checkpoints, context editing, memory tools, and an Agent SDK.
Anthropic officially released Claude Sonnet 4.5, claiming it is “the best coding model in the world” and “the strongest model for building complex agents.”
Address: https://www.anthropic.com/claude/sonnet
In the SWE software‑engineering benchmark, Sonnet 4.5 achieved a score of 77.2%, surpassing Claude Opus 4.1 (74.5%) and the previous Sonnet 4 (72.7%). External comparisons show GPT‑5 Codex at 74.5%, GPT‑5 at 72.8%, and Gemini 2.5 Pro at 67.2%.
On the OSWorld benchmark, which evaluates AI performance on real‑world computer tasks, Sonnet 4.5 scored 61.4%, well above Sonnet 4’s 42.2%.
Anthropic states that Sonnet 4.5 can provide near‑instant responses or show extended, step‑by‑step reasoning.
The model demonstrates stronger domain‑specific knowledge and reasoning in finance, law, and medicine.
Safety and consistency assessments also improved: behaviors such as flattery, deception, power‑seeking, and encouragement of delusional thinking have been reduced, and defenses against rapid injection attacks have advanced.
Pricing remains the same as Sonnet 4: $3 per million input tokens and $15 per million output tokens.
Beyond the model release, Anthropic announced several product updates: Claude Code now supports checkpoints, allowing developers to save progress and roll back; the Claude API adds context‑editing and memory tools, enabling agents to run longer and handle more complex tasks; all Claude applications now have access to code execution and file‑creation capabilities.
Anthropic also launched the Claude Agent SDK, letting developers build their own agents on the same infrastructure that powers Claude Code.
In a blog post the company wrote: “We built Claude Code because the development tools we needed didn’t exist at the time. The Agent SDK gives you the same foundation to build powerful tools that solve any problem you’re tackling.”
Author: 场长 https://anthropic.com/engineering/building-agents-with-the-claude-agent-sdk
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