Anthropic just dropped Claude 4, and it’s making waves – especially if you write code for a living. There are two models to know: Claude 4 Opus and Claude 4 Sonnet. Here’s what matters.
Opus vs Sonnet
Opus is the powerhouse. It’s the most advanced Claude model yet, designed for deep problem solving and long-running tasks. In testing, it ran a 7-hour autonomous coding session without losing context, outperforming GPT-4.1 on SWE-bench with a 72.5% score. That puts it at the top of the current leaderboards.
It also supports “extended thinking,” where it breaks tasks into steps, calls tools like browsers or APIs, then resumes reasoning. This is powerful for complex debugging, long planning, or exploratory coding – but it’s not cheap. Opus costs $15 per million input tokens and $75 per million output.
Sonnet is more budget-friendly ($3 in / $15 out per million tokens) and faster. It still delivers top-tier performance – 72.7% on SWE-bench – and is now powering GitHub Copilot by default. Sonnet supports the same 200K-token context as Opus, and subjectively it does a better job using that context effectively than previous Claude models. In practice, that means fewer redundant questions, better code integration, and smarter reuse of earlier logic.
Our Take
Sonnet 4 is our default for a reason. It’s faster, more precise, and adapts well to real projects. Compared to other models, it generates fewer “patch fix” workarounds and more code that integrates cleanly into the existing structure. It’s also noticeably better at using long context effectively – helpful when finding subtle bugs or reusing earlier definitions.
Opus is powerful, but expensive. We reach for it when Sonnet stalls – especially in deep debugging or thorny refactors. But it’s not practical for everyday use. We’ve seen Opus spend $5–10 on a single task. Great when it works, but Sonnet does the job 90% of the time.
How It Stacks Up
Although Anthropic promises benchmark-leading performance, we haven’t seen the models added to the publicly available benchmark yet — perhaps that will change later. Here are their own measurements:
Claude Sonnet 4:
- Cheaper than GPT-4o and Gemini Pro per input token
- Matches Claude 3.5 in context size (200K tokens)
- Strong at reusing project logic, fewer hallucinations
Claude Opus 4:
- State-of-the-art reasoning and coding accuracy
- High cost, slower inference
- Best for long sessions or agent-like workflows
What’s New
Claude 4 models can now “think” in stages. That means they can pause, perform tool-based reasoning, and return more accurate results. They also support a 200K-token context window, allowing for massive prompts that include entire projects, documentation, or multi-file diffs.
Sonnet shines when it comes to actually using that context. It recalls helper functions, respects naming conventions, and integrates into your codebase with minimal friction. It doesn’t just paste in boilerplate – it understands what fits.
Real-World Use
We’ve used Sonnet extensively in Claude Code. Compared to older models, it’s much better at generating context-aware suggestions. It writes code that feels native to your repo – not just copy-pasted logic, but clean edits that follow existing patterns.
Debugging is also more effective. Claude 4 can trace complex bugs across multiple files, often without needing hints. That’s a direct result of better long-context handling and improved reasoning.
Opus steps in when we’re stuck – especially on vague or multi-layered issues. It’s not the default, because of cost and speed, but in edge cases it can save hours of trial and error.
External Reactions
Claude 4 impressed across the board. Ars Technica reported Opus solved 43% more GitHub issues than GPT-4 on SWE-bench. Wired highlighted its long attention span, pointing to the 7-hour Pokémon agent demo as proof of its sustained planning capabilities.
The Verge focused on real-world dev tools: GitHub Copilot is now using Sonnet by default, with Opus offered in premium tiers. On Hacker News, devs praised Sonnet’s low friction and fast adresponses. A few commenters noted that Opus still struggles with complex tool use, but agree it’s better at sticking with a problem.
Final Word
If you want a fast, cost-effective dev assistant, go with Sonnet. If you’re experimenting with AI agents or need deeper reasoning for complex problems, Opus is there when you need it. Claude 4 raises the bar – and for devs, that means smarter tools and fewer headaches.
