Claude Sonnet 4.5

Overview

Claude Sonnet 4.5 is Anthropic's most advanced Sonnet-tier model, available through OpenRouter for broad production use. It is designed as a practical workhorse: stronger than lightweight tiers on hard tasks while remaining faster and cheaper than Opus-class models.

Sonnet 4.5 emphasizes real-world agent workflows, coding quality, and sustained continuity across long sessions. In this platform it is configured with a large context window and is frequently a default choice for teams that need both high capability and operational efficiency.

Capabilities

• Balanced reasoning and speed Combines strong depth with practical latency for production systems
• Agentic coding workflows Supports multi-step coding, tool orchestration, and iterative execution
• Long-context operation Handles large context windows for repository-scale or document-scale tasks
• Instruction reliability Better adherence to complex specifications and constrained prompts
• Multimodal support Supports text-and-image understanding in Claude 4 generation usage

Strengths

• Strong quality-to-cost ratio for production workloads
• Reliable on multi-turn coding and analysis tasks
• Better throughput than Opus tiers in many operational settings
• Effective for agent-based workflows with tool calls
• Good default model for teams with mixed task complexity

Limitations and Considerations

• Still more expensive than Haiku for very high-volume simple tasks
• Not as deep as Opus on the hardest reasoning problems
• Long-context and heavy tool loops can still increase latency and spend
• Task routing is recommended for optimal cost-performance

Best Use Cases

Claude Sonnet 4.5 is ideal for:

• Production coding assistants and developer copilots
• Agent workflows involving planning, tools, and execution
• Security review and specification-driven implementation
• Long-context research and technical summarization
• Enterprise knowledge work requiring balanced cost and quality