Claude Opus 4.5 Now Available: The Most Intelligent AI Model Comes to just4o.chat

We're thrilled to announce that Claude Opus 4.5, Anthropic's most advanced and intelligent model to date, is now available on just4o.chat. Released today by Anthropic, Opus 4.5 represents a significant leap forward in what AI systems can accomplish, and we're making it accessible to our Studio and Aurora tier subscribers right away.

The Most Capable AI Model in the World

Claude Opus 4.5 isn't just an incremental update—it's a transformative model that sets new standards across multiple domains. Whether you're coding complex applications, conducting deep research, or tackling everyday creative and analytical tasks, Opus 4.5 brings a level of intelligence and understanding that consistently impresses.

What makes Opus 4.5 truly special is how it handles ambiguity and reasons about tradeoffs without requiring hand-holding. Early testers report that when pointed at complex, multi-system problems, Opus 4.5 simply figures out the solution. Tasks that were near-impossible for other models just weeks ago are now within reach. The consistent feedback we've heard is that Opus 4.5 just "gets it."

Benchmark Performance: Leading Across Key Metrics

Claude Opus 4.5 delivers state-of-the-art performance across industry-standard benchmarks, demonstrating its superiority in real-world applications.

Software Engineering Excellence: SWE-bench Verified

On SWE-bench Verified, the gold standard for evaluating AI models on real-world software engineering tasks, Claude Opus 4.5 achieves the highest score among all frontier models. This benchmark tests models on actual GitHub issues from popular open-source repositories, requiring them to understand codebases, identify bugs, and implement working fixes.

What this means for you: Whether you're debugging complex applications, building new features, or refactoring legacy code, Opus 4.5 brings professional-grade software engineering capabilities to your conversations.

Multilingual Coding: SWE-bench Multilingual

Opus 4.5 demonstrates exceptional versatility across programming languages, leading on 7 out of 8 languages tested in SWE-bench Multilingual. From Python and JavaScript to Rust and Go, Opus 4.5 writes cleaner, more efficient code regardless of your technology stack.

What this means for you: No matter what languages your projects use, Opus 4.5 adapts seamlessly to your development environment and coding style.

Agentic Tasks: BrowseComp-Plus

For complex, multi-step tasks that require reasoning, planning, and execution across multiple tools and contexts, Opus 4.5 excels on BrowseComp-Plus evaluations. In Anthropic's testing, combining Opus 4.5's capabilities with advanced context management boosted performance by nearly 15 percentage points, demonstrating the model's effectiveness at long-running research and analytical workflows.

What this means for you: When you need deep research, comprehensive analysis, or tasks that require coordinating multiple sources and steps, Opus 4.5 maintains focus and delivers thorough results.

Security and Alignment: Prompt Injection Resistance

Beyond raw capability, Claude Opus 4.5 is the most robustly aligned frontier model available today. It demonstrates substantial improvements in resisting prompt injection attacks—sophisticated attempts to trick AI models into harmful behavior through deceptive instructions. On Gray Swan's rigorous prompt injection benchmark, Opus 4.5 outperforms all other frontier models.

What this means for you: You can trust Opus 4.5 to stay focused on helping you, even when working with untrusted content or complex instructions. The model maintains its alignment and refuses to be manipulated into problematic behavior.

Remarkable Efficiency: More Intelligence, Fewer Tokens

Despite its dramatically enhanced capabilities, Claude Opus 4.5 achieves better results while using significantly fewer tokens than previous models. This efficiency translates to faster responses and more economical usage without sacrificing quality. In fact, at medium effort levels, Opus 4.5 matches the previous best Sonnet scores while using 76% fewer output tokens.

This efficiency makes premium AI more accessible and sustainable for everyday use, whether you're working on intensive projects or having casual conversations.

How to Access Claude Opus 4.5 on just4o.chat

Claude Opus 4.5 is available immediately as part of Premium+ model suite. You can access it if you're subscribed to our Studio tier ($15/month) or Aurora tier ($25/month), or if you have Premium Credits in your account.

As always with just4o.chat, when you select Claude Opus 4.5 from the model picker in your composer, you get Claude Opus 4.5—every single time. No hidden model switching, no mysterious downgrades, just the transparent, honest AI experience you've come to expect from us.

Why Opus 4.5 Shines on just4o.chat

The combination of Claude Opus 4.5's exceptional intelligence with just4o.chat's unique features creates something truly special. Our personal memory architecture means Opus 4.5 doesn't just understand your current conversation—it knows your context, your preferences, your goals, and your working style from previous interactions.

Add in our custom personas, project organization, and flexible customization options, and Opus 4.5 becomes more than just a powerful AI model. It becomes a companion that truly understands you and grows with you over time, whether you're journaling, coding, researching, planning, or creating.

Ready to Experience the Future of AI?

If you're already on our Studio or Aurora tier, you can start using Claude Opus 4.5 right now. Simply open a new chat or select it from your model picker in any conversation.

Not on Studio or Aurora yet? Consider upgrading your plan to unlock access to Claude Opus 4.5 and all our other Premium+ models. You'll get the most capable AI available today, combined with the personalization, transparency, and control that make just4o.chat different.

New to just4o.chat? You can start for free on our Explorer tier and upgrade whenever you're ready to experience premium models like Opus 4.5. No credit card required to begin.

Experience AI that's not just intelligent—it's honest, personal, and truly yours.

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Technical Details: Claude Opus 4.5 is accessed via the model string claude-opus-4-5-20251101 in Anthropic's API. For more information about Claude Opus 4.5's capabilities and performance, visit Anthropic's announcement.