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/

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Claude Opus 4.5