Skip to content
Not available in this workspace
OpenRouterOpenRouter
© 2026 OpenRouter, Inc

Product

  • Chat
  • Rankings
  • Benchmarks
  • Apps
  • Discover
  • Models
  • Collections
  • Providers
  • Pricing
  • Enterprise
  • Labs

Company

  • About
  • Blog
  • Careers
    Hiring
  • Privacy
  • Terms of Service
  • Support
  • Works With OR
  • Data

Developer

  • Documentation
  • API Reference
  • Developer Platform
  • Status

Connect

  • Discord
  • GitHub
  • LinkedIn
  • X
  • YouTube
Favicon for anthropic

Anthropic: Claude Sonnet 4.5

anthropic/claude-sonnet-4.5

Compare

Claude Sonnet 4.5 is Anthropic’s most advanced Sonnet model to date, optimized for real-world agents and coding workflows. It delivers state-of-the-art performance on coding benchmarks such as SWE-bench Verified, with improvements across system design, code security, and specification adherence. The model is designed for extended autonomous operation, maintaining task continuity across sessions and providing fact-based progress tracking.

Sonnet 4.5 also introduces stronger agentic capabilities, including improved tool orchestration, speculative parallel execution, and more efficient context and memory management. With enhanced context tracking and awareness of token usage across tool calls, it is particularly well-suited for multi-context and long-running workflows. Use cases span software engineering, cybersecurity, financial analysis, research agents, and other domains requiring sustained reasoning and tool use.

Modalities

In / Out Price

$3 / $15per 1M

Context

1M

Released

Sep 29, 2025

Knowledge Cutoff

Jan 2025

Compare

About Anthropic: Claude Sonnet 4.5

OpenRouter makes Anthropic: Claude Sonnet 4.5 available through a unified, OpenAI-compatible API using the model ID anthropic/claude-sonnet-4.5. Requests can be routed across 5 providers, including Amazon Bedrock (EU), Anthropic, Google Vertex (US), Claude Platform on AWS and Azure, with automatic failover when an endpoint is unavailable.

Anthropic: Claude Sonnet 4.5 accepts text, images and files such as PDFs and returns text. It has a 1,000,000-token context window and a maximum output of 64,000 tokens.

On OpenRouter, Anthropic: Claude Sonnet 4.5 costs $3.00/M input tokens and $15.00/M output tokens, with separate rates for Cache Read at $0.30/M tokens, Cache Write at $3.75/M tokens and Cache Write (1h) at $6.00/M tokens. Effective pricing can be lower when prompt caching applies. It was released on September 29, 2025; its knowledge cutoff is January 31, 2025.

More models from Anthropic

  • Claude Opus 5 (Fast)
  • Claude Opus 5
  • Claude Sonnet 5

Frequently asked questions

Claude Sonnet 4.5 is Anthropic’s most advanced Sonnet model to date, optimized for real-world agents and coding workflows. It delivers state-of-the-art performance on coding benchmarks such as SWE-bench Verified, with improvements across system design, code security, and specification adherence.

Claude Sonnet 4.5 costs $3.00/M input tokens and $15.00/M output tokens, with separate rates for Cache Read at $0.30/M tokens, Cache Write at $3.75/M tokens and Cache Write (1h) at $6.00/M tokens.

Claude Sonnet 4.5 has a 1,000,000 token context window. It supports up to 64,000 completion tokens.

Yes. Claude Sonnet 4.5 accepts tools and tool_choice for function calling. It also supports structured outputs via a JSON schema in response_format.

Claude Sonnet 4.5 accepts text, images and files such as PDFs as input and returns text.

Claude Sonnet 4.5 is served by 5 providers on OpenRouter: Amazon Bedrock (EU), Anthropic, Google Vertex (US), Claude Platform on AWS and Azure. Requests are routed to the best available provider, with automatic failover to the others, and you can pin or exclude providers with provider routing.

Claude Sonnet 4.5 was released on September 29, 2025. Its knowledge cutoff is January 31, 2025.