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Claude Sonnet 4.5 is here — highlights, benchmarks, and pricing

Anthropic released Claude Sonnet 4.5 with major coding and agentic upgrades, plus a new Claude Agent SDK. Here’s a concise, source-based recap and what to test in production.

Claude Sonnet 4.5 release highlights

TL;DR

Anthropic has released Claude Sonnet 4.5, calling it their best coding model and strongest model for complex agents and computer use. The launch also introduces major product upgrades (Claude Code improvements, memory tools) and the Claude Agent SDK, while keeping pricing unchanged at $3/$15 per million tokens.

What’s new in Claude Sonnet 4.5

From Anthropic’s announcement, key upgrades include:

  • Best coding model and stronger reasoning/math performance
  • Improved agentic and computer-use capabilities
  • Claude Agent SDK for building long-running agents with memory and permissions tooling
  • Claude Code updates: checkpoints, refreshed terminal UI, VS Code extension
  • Claude app updates: code execution + file creation in-app

Benchmarks & capability claims

Anthropic highlights several improvements and benchmarks:

  • SWE-bench Verified: state-of-the-art coding performance
  • OSWorld: 61.4%, a major jump for real-world computer tasks
  • Long task focus: ability to sustain multi-step work for extended periods

Availability & pricing

  • Available via Claude API, Claude app, Claude Code, and major platforms (including Bedrock and Vertex AI)
  • Pricing unchanged vs Sonnet 4: $3 / $15 per million tokens

Why it matters

If these gains hold in production, Sonnet 4.5 becomes a strong default for:

  • Agentic workflows and tool-using systems
  • Software engineering (codegen, refactors, bug fixing)
  • Computer-use automation with improved stability

How to evaluate in your stack

  1. Run A/B tests on core coding tasks and agent flows.
  2. Measure latency + cost against your current default model.
  3. Check tool-use stability in real workflows (browsing, file ops, CLI tasks).

For model-agnostic routing, see Models, Pricing, and the Blog.

Sources

  • Anthropic announcement: Introducing Claude Sonnet 4.5
  • Reddit (official): Introducing Claude Sonnet 4.5 (r/ClaudeAI)