What Is Claude Sonnet 4.5 and How to Build With It?

TL;DR

Anthropic released Sonnet 4.5, which is five times cheaper than Opus 4.1 while beating it on nearly every benchmark, including topping SWE-bench Verified for software engineering. It shipped alongside Claude Code 2.0, Claude Imagine, a browser extension, context editing, and file creation for sheets, docs, slides, and PDFs.

Transcript

If you don't use cloth, you're falling behind because Enthropic just released Sonet 4.5, Cloth Code 2.0, a new agent SDK, browser use, and so much more. My name is David Andre, and I'm the founder of Vector.ai. Over the last 3 years, I've spent hundreds of hours building software with AI. And in this video, we'll look at the new cloth updates, how ... Read More

Key Insights

• Claude Sonnet 4.5 is exactly five times cheaper than Opus 4.1 while beating it on nearly every benchmark. Because it is a smaller model, it runs noticeably faster while still being more powerful and intelligent, according to the presenter's testing.
• Sonnet 4.5 leads the SWE-bench Verified benchmark for software engineering, scoring better than every other model in the world both without reasoning and with reasoning enabled, making it exceptional at programming tasks.
• Claude Code 2.0 is described as by far the biggest Claude Code update ever, adding checkpoints to revert to a previous conversation state, a revamped terminal interface with a mascot, context editing, and an IDE extension.
• Claude AI can now create and edit sheets, documents, slides, and PDFs directly inside the app, and connect to Google Drive, Gmail, and Calendar through the settings menu in about 20 seconds.
• Claude Imagine is a new way to build software where the app is generated procedurally on pre-built components in real time, acting like its own operating system rather than writing hundreds of lines of code upfront.
• Sonnet 4.5 is the first model aware of its own context window, tracking tokens used and remaining, which causes 'context anxiety' where it rushes tasks and takes shortcuts as it nears its context limit.
• Context editing compacts the oldest, least relevant parts of a conversation into essentials, freeing available context as the conversation progresses toward the latest messages.
• Anthropic released an official browser extension that lets Claude control a browser, take screenshots, read the HTML DOM, and take actions like archiving emails, offered as a privacy-first alternative to data-collecting AI browsers.

Questions & Answers

Q: How much cheaper is Claude Sonnet 4.5 than Opus 4.1?

Claude Sonnet 4.5 is exactly five times cheaper than Opus 4.1, which the presenter notes was already an incredible model. Despite the lower cost, Sonnet 4.5 beats Opus 4.1 on nearly every benchmark. It is also a smaller model, which makes it run significantly faster than Opus 4.1 while at the same time being a more powerful and intelligent model in the presenter's hands-on testing.

Q: How does Claude Sonnet 4.5 perform on software engineering benchmarks?

On the SWE-bench Verified benchmark for software engineering, Claude Sonnet 4.5 is better than everything else in the world right now, scoring highest both without reasoning and with reasoning enabled. In a live test, it built a JavaScript particle app that reacts to mouse movement with magnetism, propulsion, and orbital physics in about 20 seconds, in a single prompt with no corrections or errors, demonstrating its strength at programming.

Q: What is new in Claude Code 2.0?

Claude Code 2.0 is called by far the biggest Claude Code update ever. Major upgrades include checkpoints, a way to go back and access a previous state of the conversation, a new revamped terminal interface with a cool mascot, context editing, and an IDE extension. The presenter says Claude Code has improved massively with this release, packing in a large number of new features at once.

Q: How do you connect Google Drive, Gmail, and Calendar to Claude?

Open Claude AI, create a new chat, and click the settings button, which reveals search options including extended thinking plus connectors for Google Drive, Gmail, and Calendar. If nothing is connected, choose one, click connect, and follow the steps, which takes about 20 seconds. Reload the site, then toggle the connector on. You can then prompt Claude to pull data, such as listing your five most recent Google Docs.

Q: What is Claude Imagine and how does it work?

Claude Imagine is a completely new way of building software, described as vibe coding 2.0. The app you describe is generated on the go using pre-built components rather than writing hundreds of lines of code that must compile. It works procedurally, like its own operating system, generating custom UI in real time one component at a time so you can interact with parts as they build. Access is limited, available at claude.ai/imagine.

Q: What is context anxiety in Claude Sonnet 4.5?

Context anxiety is a term coined by Cognition AI, the creators of Devon, who had early access to Sonnet 4.5. Sonnet 4.5 is the first model aware of its own context window, knowing how many tokens it used and how many remain. As it nears its context limit, it summarizes progress to save tokens but also tends to rush tasks toward completion, taking shortcuts rather than doing a proper job when little context is left.

Q: How does context editing work in Claude?

Context editing compacts the oldest parts of a conversation into their true essentials. A context window contains tokens from tool use, tool results, and conversation. Whatever you send at the very beginning is usually the least relevant, so it gets compressed first. As you progress toward your latest messages, more available context is freed because the oldest portions of the conversation have been compacted, leaving the current state and most recent message intact.

Q: What can the Claude browser extension do?

Anthropic released an official Claude browser extension that lets Claude control your browser. It takes screenshots, reads the HTML DOM to find exact buttons, and takes actions like archiving emails in a Gmail inbox. An orange outline shows Claude is in control. It is presented as a privacy-first alternative to AI browsers like Comet or Dia, which the presenter says collect extensive data. The extension is a pilot available at claude.ai/chrome for a limited number of Max plan users.

Summary & Key Takeaways

• Anthropic released Claude Sonnet 4.5, described as in many ways the best model in the world. It is five times cheaper than Opus 4.1 yet beats it on nearly every benchmark, and it tops the SWE-bench Verified software engineering benchmark both with and without reasoning enabled.

• The launch bundled Claude Code 2.0 with checkpoints, a revamped terminal, context editing, and an IDE extension. Claude AI also gained the ability to create sheets, docs, slides, and PDFs, plus connectors for Google Drive, Gmail, and Calendar set up through the settings menu.

• Claude Imagine generates software procedurally on pre-built components for real-time creative exploration. Sonnet 4.5 uniquely tracks its own context window, causing context anxiety, while a new official browser extension lets Claude control browsers as a privacy-first alternative to data-harvesting AI browsers.