Anthropic has unveiled Claude Sonnet 4.5, calling it the most powerful and capable coding AI model to date.
Quick Summary – TLDR:
- Claude Sonnet 4.5 delivers major upgrades in reasoning, math, and long-duration task handling
- Anthropic debuts a new experimental feature, “Imagine with Claude”, that generates applications on the fly
- New tools include code execution, file creation, checkpoints, and a refreshed VS Code extension
- A new Claude Agent SDK allows developers to build their own powerful AI agents
What Happened?
Anthropic has launched Claude Sonnet 4.5, its latest AI model that the company confidently describes as “the best coding model in the world”. This release not only boosts raw performance in code generation and reasoning, but also introduces a futuristic ability: real-time app creation, turning AI conversations into interactive software experiences.
Introducing Claude Sonnet 4.5—the best coding model in the world.
— Claude (@claudeai) September 29, 2025
It’s the strongest model for building complex agents. It’s the best model at using computers. And it shows substantial gains on tests of reasoning and math. pic.twitter.com/7LwV9WPNAv
Claude Sonnet 4.5 Raises the Bar
Claude Sonnet 4.5 brings a huge leap in performance compared to its predecessor, Claude Sonnet 4. Benchmarks on the SWE-bench Verified evaluation show Claude outperforming earlier models in real-world coding tasks. Its OSWorld score jumped from 42.2% to 61.4%, confirming a major boost in practical computer use.
The model also maintains focus for over 30 hours on complex, multi-step tasks, dramatically extending AI usefulness for long-horizon workflows. This improvement is particularly helpful in domains like software engineering, law, medicine, and finance, where detailed, domain-specific knowledge is critical.
Key Feature Upgrades
Anthropic didn’t just release a new model; it rolled out a full suite of new tools and enhancements:
- Checkpoints in Claude Code: Save and roll back progress easily during coding tasks.
- Refreshed Terminal UI and native VS Code extension.
- File creation within conversations: Generate documents, spreadsheets, and slides directly inside the Claude app.
- Code execution support for real-time programming output.
- Context editing and memory tools in Claude API to enable longer and more complex agent tasks.
These features improve the everyday usability of Claude in real-world developer workflows.
Real-Time Apps with “Imagine with Claude”
One of the biggest surprises in this release is an experimental feature called “Imagine with Claude”. Available as a preview to Claude Max subscribers, it allows the AI to create interactive software on the fly.
In a demo, Claude responded to a prompt about William Shakespeare’s computer by creating a simulated interface that let the user explore apps within a fictional OS. The app was not prewritten; Claude generated code dynamically as the user clicked through the interface. This signals a major step toward on-demand software that responds instantly to user input.
New Claude Agent SDK Now Public
Developers can now access the Claude Agent SDK, the same infrastructure that Anthropic used to build Claude Code. This toolkit gives developers the power to design their own custom AI agents, managing long-running tasks, memory, and permission systems effectively.
Anthropic said the SDK supports a wide variety of applications beyond just coding, opening doors to new possibilities in automation, customer support, internal tools, and more.
Stronger on Safety and Alignment
Claude Sonnet 4.5 also comes with significant improvements in AI alignment and safety. Anthropic says the model shows reduced signs of sycophancy, deception, power-seeking, and delusional behavior. It operates under the company’s AI Safety Level 3 framework, which includes CBRN classifiers that help detect dangerous prompts and limit misuse.
Despite increased safeguards, Claude 4.5 maintains flexibility. Users can switch to Sonnet 4 if safety filters interfere unnecessarily. Anthropic has already reduced false positives tenfold since earlier model versions.
Expanded Access and Pricing
Claude Sonnet 4.5 is now available through:
- Claude API
- Claude Code
- Claude Apps
Pricing remains consistent with Sonnet 4: $3 per million tokens for standard use and $15 per million tokens for extended use.
More users can now access features like the Claude for Chrome extension and file creation tools, as Anthropic expands eligibility beyond Max subscribers.
SQ Magazine Takeaway
Honestly, this is one of the most exciting AI updates we’ve seen this year. Claude Sonnet 4.5 doesn’t just talk a big game. It delivers with real upgrades, useful tools, and even a glimpse into the future of real-time, user-guided software generation. The Agent SDK is a developer’s dream, and the alignment work shows Anthropic is serious about responsible AI. If you’re building anything with code or agents, this is a must-try.
