Claude Opus 4.5 Released: Anthropic's Most Powerful Coding AI Yet

Introduction

On November 24, 2025, Anthropic released Claude Opus 4.5, their most advanced AI model to date. This isn't just an incremental update - it's a significant leap forward in AI-assisted coding, introducing features that fundamentally change how developers interact with AI tools.

Opus 4.5 leads the industry on coding benchmarks, introduces groundbreaking features like the effort parameter and context compaction, and delivers measurable improvements in token efficiency. Enterprise customers are already reporting 50-75% reductions in tool-calling errors.

In this comprehensive overview, we'll break down everything you need to know about Claude Opus 4.5: what's new, how it performs, what it costs, and when you should use it over other Claude models.

What's New in Claude Opus 4.5

The Effort Parameter

One of the most significant additions in Opus 4.5 is the effort parameter, which lets developers customize the balance between speed and capability.

How it works:

• Low effort: Faster responses, good for straightforward tasks
• Medium effort: Balanced mode for everyday development work
• High effort: Maximum capability for complex reasoning and difficult problems

At medium effort, Opus 4.5 matches Sonnet 4.5's performance while using 76% fewer output tokens. At the highest effort setting, it exceeds Sonnet 4.5 by 4.3 percentage points while still using 48% fewer tokens.

This flexibility means you're not paying for maximum compute on simple tasks, but you can unlock full reasoning power when you need it.

Context Compaction

For developers building agentic systems, context compaction is a game-changer. This technology allows Opus 4.5 to maintain coherent understanding across extended sessions without the context window bloating that typically degrades AI performance over time.

Real-world impact:

• Up to 65% fewer tokens required for long-horizon coding tasks
• Consistent performance in 30-minute autonomous coding sessions
• Maintains context coherence across complex, multi-step refactoring operations

This is particularly valuable for tools like Claude Code, where the AI needs to understand an entire codebase and make coordinated changes across many files.

Token Efficiency Improvements

Opus 4.5 delivers significant efficiency gains across the board:

| Metric | Improvement | |--------|-------------| | Long-horizon coding tasks | 65% fewer tokens | | Medium effort vs Sonnet 4.5 | 76% fewer output tokens | | High effort vs Sonnet 4.5 | 48% fewer tokens (with better results) |

These aren't just cost savings - fewer tokens mean faster responses and the ability to tackle larger problems within context limits.

Enhanced Safety and Alignment

Anthropic describes Opus 4.5 as their "most robustly aligned model released to date." The system card highlights several safety improvements:

• Industry-leading resistance to prompt injection attacks
• Lowest concerning behavior scores compared to frontier competitors
• Reduced reward-hacking behavior in agentic scenarios
• Enhanced reliability for critical enterprise deployments

For enterprises handling sensitive code or deploying AI in production environments, these safety improvements are crucial.

Benchmark Performance

Opus 4.5 doesn't just claim to be better - it proves it on industry-standard benchmarks.

SWE-bench Verified

Claude Opus 4.5 leads all frontier models on SWE-bench Verified, the industry's most respected coding evaluation. This benchmark tests real-world software engineering tasks, including:

• Bug fixes in actual open-source repositories
• Multi-file code changes
• Understanding complex codebases
• Writing tests and documentation

Aider Polyglot Benchmark

On the Aider Polyglot benchmark, which tests multi-language coding ability, Opus 4.5 shows a 10.6% improvement over Sonnet 4.5. This benchmark evaluates performance across:

• Python
• JavaScript/TypeScript
• Java
• C++
• Go
• Rust
• Ruby
• PHP

Opus 4.5 leads on 7 of 8 programming languages in SWE-bench Multilingual.

Vending-Bench

For agentic tasks, the Vending-Bench results are particularly impressive. Opus 4.5 delivers 29% higher performance than Sonnet 4.5, demonstrating superior ability to:

• Plan multi-step solutions
• Execute complex workflows autonomously
• Recover from errors gracefully
• Maintain consistency across long task chains

BrowseComp-Plus

On agentic search tasks (BrowseComp-Plus), Opus 4.5 shows "significant gains," reinforcing its strength in scenarios where the AI must independently gather information and make decisions.

Pricing and Availability

API Pricing

| Token Type | Price | |------------|-------| | Input tokens | $5 per million tokens | | Output tokens | $25 per million tokens |

This represents a significant cost reduction compared to previous Opus versions, making frontier-level performance more accessible for production deployments.

Platform Availability

Claude Opus 4.5 is available across multiple platforms:

• Claude Apps: Web and desktop applications
• Claude API: Direct API access for developers
• Amazon Bedrock: AWS integration
• Google Cloud Vertex AI: GCP integration
• Microsoft Azure: Azure integration
• Claude Code: Desktop application and CLI

Access Methods

• claude-opus-4-5-20251101: Official model ID for API access
• Claude Pro/Max subscriptions: Access through Claude apps
• Enterprise agreements: Custom deployment options

When to Use Opus 4.5 vs Sonnet 4.5

With two powerful models available, choosing the right one depends on your use case.

Use Opus 4.5 When:

• Complex multi-file refactoring: When changes span many files and require deep understanding of the codebase
• Long-running agentic tasks: Tasks that take 10+ minutes and require consistent context
• Difficult debugging: Edge cases and subtle bugs that require extensive reasoning
• Architecture decisions: When you need thorough analysis of trade-offs
• Enterprise-critical code: When you need maximum reliability and safety

Use Sonnet 4.5 When:

• Quick iterations: Rapid prototyping and fast feedback loops
• Straightforward tasks: Clear requirements with obvious implementations
• Cost-sensitive workloads: High-volume tasks where cost per token matters
• Real-time interactions: When response latency is critical

The Effort Parameter Strategy

With Opus 4.5's effort parameter, you can often start with medium effort and escalate to high effort only when needed:

1. Begin complex tasks at medium effort
2. If the output isn't satisfactory, retry at high effort
3. Reserve high effort for the problems that truly demand it

This approach optimizes both cost and quality.

Claude Code Improvements

Alongside Opus 4.5, Anthropic announced significant improvements to Claude Code:

Improved Plan Mode

• Upfront clarifying questions: Claude Code now asks for clarification before starting work
• Editable execution plans: Review and modify the plan before execution
• Better task decomposition: More granular breakdown of complex tasks

Desktop Application

Claude Code is now available in Anthropic's desktop application, bringing terminal-native AI coding to a graphical interface.

Parallel Sessions

Support for parallel local and remote sessions means you can work on multiple codebases or tasks simultaneously.

Enterprise Adoption and Real-World Results

Early enterprise adopters are reporting impressive results:

• 50-75% reduction in tool-calling errors: More reliable API interactions
• Complex multi-codebase refactoring: Successfully handling changes that span multiple repositories
• Self-improving autonomous agents: Breakthroughs in building agents that learn from feedback
• Superior Excel/financial modeling: Strong performance on structured data tasks

These results suggest Opus 4.5 is ready for production enterprise workloads, not just experimentation.

The Competitive Landscape

Opus 4.5 enters a competitive November 2025 market:

• GPT-5.1-Codex-Max (OpenAI): Released November 19, focuses on 24-hour autonomous tasks
• Gemini 3 Pro (Google): Released November 18, emphasizes 1M context and multimodal reasoning

While each model has strengths, Opus 4.5's combination of benchmark leadership, the effort parameter, and context compaction positions it strongly for serious development work.

Getting Started

To start using Claude Opus 4.5:

Via API:

import anthropic

client = anthropic.Anthropic()
message = client.messages.create(
    model="claude-opus-4-5-20251101",
    max_tokens=1024,
    messages=[
        {"role": "user", "content": "Your prompt here"}
    ]
)

Via Claude Code:

claude --model opus

Via Claude Apps: Select "Claude Opus 4.5" from the model dropdown in the web or desktop application.

Conclusion

Claude Opus 4.5 represents a significant milestone in AI-assisted coding. With state-of-the-art benchmark performance, innovative features like the effort parameter and context compaction, and meaningful improvements in safety and reliability, it's positioned as the premier choice for serious development work.

The $5/$25 per million token pricing makes these capabilities accessible, and the wide platform availability (API, Bedrock, Vertex, Azure) means you can integrate Opus 4.5 into your existing infrastructure.

For developers and enterprises looking to maximize their AI coding capabilities, Opus 4.5 is worth serious consideration.

Ready to try Claude Opus 4.5?

• Check out the Claude API
• Explore Claude Code
• Compare AI coding tools