Neither “all Opus” nor “all Sonnet” is the right call; you have to mix them.
Quick note on versions: Anthropic publicly introduced Opus 4.8 on May 28, 2026. So this comparison looks at Opus 4.8 vs Sonnet 4.6. But the exact model you can switch to in your account still depends on what the Claude interface or Claude Code’s /model command shows.
Capability Differences
Reasoning
The biggest gap between Opus 4.8 and Sonnet 4.6 is reasoning. Anthropic’s own framing of Opus 4.8 is direct: it is stronger than 4.7 on complex coding and agentic tasks, and it is less likely to leave flaws in code it wrote unflagged.
For complex logic, multi-step analysis, or decisions that need several factors weighed at once, Opus pulls ahead clearly. For example, if you ask it to find a hidden race condition, permission flaw, or security issue in a few hundred lines of code, Opus tends to dig deeper. Sonnet is more likely to catch only the surface-level problems.
Instruction Following
On long prompts and rule-heavy tasks, Opus follows instructions noticeably better. Give both models the same style guide, including banned words, tone settings, and structure requirements, and Opus drafts usually need far less cleanup than Sonnet drafts.
Speed
Sonnet is much faster. In practice, it often feels about 2-3x faster than Opus.
Ask a simple question and Sonnet usually finishes in 2-3 seconds. Opus may take 5-8 seconds. When you are having a lot of back-and-forth, that gap becomes very noticeable.
Long-Form Consistency
The difference is biggest when writing long pieces.
At around 2,000 words, Sonnet’s style often starts drifting and slowly falls back to its default voice. Opus can still hold the assigned style beyond 3,000 words.
For long-form writing, such as blog posts, newsletters, and reports, going straight to Opus is a common choice.
Comparison Table
| Comparison | Opus 4.8 | Sonnet 4.6 |
|---|---|---|
| Reasoning | Top-tier, stable long-chain reasoning | Strong, performance close to previous-gen Opus |
| Speed | Slow | Fast (feels 2-3x faster) |
| Instruction following | Excellent | Good |
| Long-form quality | Stable beyond 3,000 words | Often drifts after 2,000 words |
| Cost (API) | High | Low |
| Chinese-language quality | Top-tier | Good |
| Best for | Strategy, analysis, long-form writing, security review | Daily tasks, coding, batches, agent execution |
Recommended Use Cases
When to Use Opus
Long-form writing: For articles over 1,500 words, the quality gap with Opus is obvious.
Complex analysis: Technical architecture reviews, security audits, and multi-angle comparisons. Opus can consider more factors at once, so its conclusions are easier to defend.
Strategy planning: Any situation where you need to weigh tradeoffs and make judgment calls. Opus gives more nuanced suggestions than Sonnet.
Auditing and review: Let Opus review Sonnet’s output. The combination of Sonnet doing the first pass and Opus checking it is usually more stable than running either model alone.
When to Use Sonnet
Daily Q&A: Looking up grammar, asking about concepts, translating sentences. Using Opus here is overkill.
Code writing: For regular functions, API endpoints, and CRUD work, Sonnet’s output is usually close to Opus.
Format conversion: Mechanical tasks like JSON to CSV or Markdown to HTML are where Sonnet is fast and steady.
Batch processing: When you need to run 20 similar tasks, Sonnet’s speed advantage cuts total time by a lot.
API Pricing
The API price gap is not small. For exact numbers, check Anthropic’s official pricing page.
If API users throw everything at Opus, the bill climbs fast. Separate tasks that truly need Opus quality from tasks where Sonnet is enough, and you can cut the bill by a lot.
Subscription plans: Pro $20/month, Max 5x $100/month, and Max 20x $200/month. Pro and above can use Opus; the difference is the usage limit. Max 5x has 5× Pro’s quota; Max 20x has 20×. If you mainly switch models in the web app, you do not need to worry about API pricing. Just pick the model based on the task.
Multi-Agent Division of Labor
When you put Opus and Sonnet into the same agent system, the common split looks like this:
- Opus as the strategy layer: judgment, review, long-form writing, architecture design
- Sonnet as the execution layer: mechanical tasks, code writing, batch processing, format conversion
Specific task allocation:
- Article first draft → Opus
- Format cleanup and layout adjustments → Sonnet
- Code review → Opus
- Code writing → Sonnet (Opus only discusses architecture)
- Summaries and translation → Sonnet
- Security audit → Opus
After running this setup for a while, the benefit becomes clear: Opus’s context window is saved for work that truly needs it, instead of being filled with daily chores. Sonnet runs quickly, so overall throughput improves a lot.
If Sonnet’s output never passes through Opus review, small quality issues can slip out from time to time. For public-facing content, letting Opus take one final look is the safer move. It is slower, but you get the quality assurance.
Penchan’s Experience
My multi-agent workflow is basically Opus + Sonnet + Codex, with other branches for data, automation, and media. The split is close to what I described above: strategy and review go to Opus, execution and batches go to Sonnet, coding goes through the Codex family, and public-facing content gets a final Opus pass. For more on the multi-agent architecture, see OpenClaw Multi-Agent Architecture.
The most painful part of building this system is memory and file structure: how to keep context across agent handoffs and avoid duplicate work. That is mentally harder than picking the model. Keep the core files organized, write the rules as simply as possible, and let the file structure itself act as memory. That is the most useful trick I have found so far.
Further Reading
FAQ
Q: How much better is Opus than Sonnet?
It depends on the task. Opus clearly wins on complex reasoning, long-form writing, and precise instruction following. For simple Q&A, format conversion, and basic coding, the gap is much smaller. Not every task needs Opus-level firepower.
Q: Can I use Opus for free?
Depending on account, region, and traffic, the free plan usually does not include Opus; Opus 4.8 requires Pro ($20/month), Max (from $100/month), or API access.
Q: How different are Opus and Sonnet API prices?
Opus API pricing is several times higher than Sonnet. Check Anthropic’s official pricing page for exact numbers. Subscription users (Pro from $20/month) do not need to think about API pricing; just switch models in the interface.
Q: Can Opus and Sonnet be used together?
Yes, and I recommend it. Give tasks that need deep thinking to Opus, and mechanical tasks to Sonnet. In Claude Code, you can assign different models to different agents.
Q: Should I use Opus or Sonnet for coding?
Sonnet is enough for ordinary coding. Opus is better for architecture design, complex debugging, and refactors that require understanding a lot of context. A common split is: write code with Sonnet, review code with Opus.
— Penchan