Claude Opus 4.5

Claude Opus 4.5 represents the pinnacle of Anthropic's AI capabilities, designed as their most intelligent model that balances maximum reasoning power with practical performance. Released in November 2025, Opus 4.5 introduces groundbreaking features like the effort parameter for token control and achieves unprecedented efficiency in long-horizon coding tasks. With a more accessible price point than previous Opus models while maintaining superior capability, it's engineered for the most demanding intellectual tasks requiring deep reasoning and complex problem-solving.

Key Features

1. Unique Effort Parameter

Claude Opus 4.5 is the only model supporting the effort parameter, offering unprecedented control:

• Customizable thinking depth: Adjust how many tokens Claude uses for reasoning before responding
• Efficiency optimization: Balance thoroughness with token usage for cost control
• Quality tuning: Increase effort for complex problems, reduce for simpler queries
• Adaptive performance: Fine-tune model behavior for specific use cases

This exclusive feature allows developers to optimize the trade-off between response quality and computational cost on a per-request basis.

2. Exceptional Long-Horizon Coding

Handles extended programming tasks more efficiently than any tested model:

• Higher pass rates: Superior task completion on complex, multi-file projects
• 65% fewer tokens: Achieves better results while using significantly fewer tokens than alternatives
• Sustained quality: Maintains code quality throughout lengthy development sessions
• Architectural planning: Excels at system design and long-term technical decisions

3. Maximum Intelligence

Anthropic's most capable model for complex reasoning:

• Advanced problem-solving: Tackles the most challenging intellectual tasks
• Deep analysis: Comprehensive understanding of complex subjects
• Creative solutions: Novel approaches to difficult problems
• Multi-domain expertise: Strong performance across diverse knowledge areas

4. Extended Context Window

• 200k token context: Substantial context for large documents and codebases
• Consistent performance: Maintains quality throughout the entire context window
• Complex cross-referencing: Handles intricate relationships across large amounts of information

Technical Specifications

• Model Family: Claude 4 Opus
• Developer: Anthropic
• Release Date: November 2025
• Context Window: 200k tokens
• Maximum Output: 8,192 tokens
• Multimodal: Supports text and image inputs
• Special Feature: Effort parameter (exclusive)

Pricing

API Access (per million tokens):

• Input: $5
• Output: $25

More accessible pricing than previous Opus models while delivering enhanced capabilities, making top-tier intelligence more practical for production use.

Performance Highlights

Reasoning and Analysis

• GPQA: Leading performance on graduate-level reasoning
• MATH: Advanced mathematical problem-solving
• Complex reasoning: Unmatched depth for multi-step analytical tasks

Coding Excellence

• Long-horizon tasks: Best efficiency with 65% fewer tokens
• System design: Superior architectural planning capabilities
• Code quality: Maintains excellence throughout extended sessions

Knowledge and Understanding

• MMLU: Comprehensive knowledge across domains
• Specialized expertise: Strong performance in technical fields
• Contextual reasoning: Deep understanding from large documents

Use Cases

Research and Development

• Academic research and literature synthesis
• Scientific hypothesis generation and analysis
• Technical research and innovation
• Complex mathematical modeling

Advanced Software Engineering

• Large-scale system architecture design
• Multi-component application development
• Legacy system modernization
• Critical algorithm development

Strategic Analysis

• Business strategy and planning
• Market analysis and forecasting
• Risk assessment and scenario planning
• Competitive intelligence

Technical Writing

• Comprehensive technical documentation
• Research papers and white papers
• In-depth analysis reports
• Educational content development

Complex Problem-Solving

• Multi-stakeholder decision-making
• Optimization problems
• Root cause analysis
• Strategic planning

Advantages

• Maximum Capability: Anthropic's most intelligent model for demanding tasks
• Effort Parameter: Unique control over reasoning depth and token usage
• Coding Efficiency: Best performance on long-horizon programming with 65% fewer tokens
• Accessible Pricing: More affordable than previous Opus models
• Sustained Quality: Maintains excellence throughout extended interactions
• Deep Reasoning: Unmatched analytical depth for complex problems

Limitations

• Higher Cost: More expensive than Sonnet and Haiku for routine tasks
• Slower Speed: Optimized for quality over speed
• Context Size: 200k tokens vs. Sonnet's 1M beta option
• Overkill for Simple Tasks: Unnecessary capability for basic queries

Comparison with Other Models

vs. Claude Sonnet 4.5: Opus 4.5 offers deeper reasoning and the unique effort parameter, while Sonnet 4.5 provides better coding benchmarks, faster responses, and optional 1M context.

vs. Claude Haiku 4.5: Opus provides maximum intelligence for complex tasks, while Haiku excels at speed and cost for simpler workloads.

vs. Previous Opus Models: More efficient, better pricing, and introduces the effort parameter while maintaining superior capability.

vs. GPT-4 Turbo/o1: Stronger long-horizon coding efficiency and unique effort control, with more consistent reasoning quality.

vs. Gemini Ultra: Superior in coding tasks and offers more granular control through the effort parameter.

Best Practices

When to Use Effort Parameter

• High effort: Complex reasoning, critical decisions, novel problem-solving
• Medium effort: Balanced performance for typical professional tasks
• Low effort: Simple queries, routine operations, draft generation

Optimal Use Cases

• Tasks requiring maximum intelligence and deep analysis
• Long-duration coding projects with complex requirements
• Critical decisions where thoroughness outweighs speed
• Research and analysis requiring comprehensive understanding

Verdict

Claude Opus 4.5 represents the apex of practical AI intelligence, combining Anthropic's most capable reasoning with innovative features like the effort parameter and exceptional long-horizon coding efficiency. The improved pricing makes top-tier AI more accessible while maintaining the quality demanded by the most challenging tasks. Its unique ability to balance thoroughness with efficiency through the effort parameter sets it apart from all alternatives.

Recommended for: Researchers, advanced software architects, strategic analysts, technical writers, organizations requiring maximum AI capability, and complex problem-solving scenarios where quality trumps cost.

Not recommended for: Routine tasks where Sonnet or Haiku suffice, real-time applications requiring low latency, cost-sensitive use cases with simple queries, or projects needing the experimental 1M context window.

Official Resources:

• Announcement: https://www.anthropic.com/news/claude-opus-4-5
• Documentation: https://platform.claude.com/docs/
• API Reference: https://docs.anthropic.com/claude/reference/