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

TL;DR

Claude Sonnet 4.5 is a faster, lower-cost model for building software, creating files, using connected services, and controlling browser tasks. It is five times cheaper than Opus 4.1, leads SWE-bench Verified in the presenter’s comparison, and arrives alongside Claude Code 2.0, Claude Imagine, context editing, and an official browser extension. Read on for the specific capabilities, setup steps, and limitations demonstrated.

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: What is Claude Sonnet 4.5 and how can you build with it?

Claude Sonnet 4.5 is a smaller, faster model that the presenter used to build a JavaScript particle app from a single prompt in about 20 seconds, with no corrections or errors. You can also use it through Claude Code 2.0, create and edit sheets, documents, slides, and PDFs in Claude AI, or explore procedurally generated software with Claude Imagine.

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. The presenter also says it beats Opus 4.1 on nearly every benchmark and runs noticeably faster because it is a smaller model.

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

Claude Sonnet 4.5 leads the SWE-bench Verified software engineering benchmark in the comparison shown, both without reasoning and with reasoning enabled. In a practical test, it created a JavaScript app with particle effects and magnetism, repulsion, and orbital-motion options in about 20 seconds from one prompt.

Q: What is new in Claude Code 2.0?

Claude Code 2.0 adds checkpoints for returning to a previous conversation state, a revamped terminal interface, context editing, and an IDE extension. The presenter describes it as the biggest Claude Code update yet.

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

Create a new Claude chat, open settings, choose Google Drive, Gmail, or Calendar, click connect, and complete the displayed steps. The presenter says setup takes about 20 seconds; afterward, reload the site and toggle the connector on.

Q: What is Claude Imagine and how does it build software?

Claude Imagine generates an app procedurally from pre-built components instead of writing hundreds of lines of code before compilation. It creates custom interface elements in real time as you explore and interact, although access is limited and the resulting software is not reproducible.

Q: What are context anxiety and context editing in Claude Sonnet 4.5?

Context anxiety describes how Sonnet 4.5 tracks its used and remaining context, then may rush or take shortcuts as it approaches the limit. Context editing helps by compacting the oldest, least relevant conversation content into essential information while preserving the current state and recent messages.

Q: What can the official Claude browser extension do?

The official extension lets Claude control a browser by taking screenshots, reading the HTML DOM, locating buttons, and performing actions such as archiving emails. An orange outline indicates when Claude is controlling the browser, and the presenter describes the extension as a privacy-first alternative to data-collecting AI browsers.

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.