Claude Sonnet 5 vs Opus 4.8 vs Sonnet 4.6: Which Should You Use? (2026)
A clear decision matrix for Claude Sonnet 5 vs Opus 4.8 vs Sonnet 4.6 — benchmarks, pricing, and exactly when to pick each model for coding and agents in 2026.
Short Answer
Use Claude Sonnet 5 as your default; it matches or beats Opus 4.8 on most coding and agentic benchmarks (85.2% versus 80.8% on SWE-bench Verified) at roughly 40% of the cost. Reserve Opus 4.8 for the hardest 10 to 15% of reasoning-heavy tasks. Stop using Sonnet 4.6 entirely, since Sonnet 5 is better on every benchmark and cheaper during launch pricing.
The One-Table Answer
The whole Claude Sonnet 5 vs Opus 4.8 and Sonnet 4.6 decision fits in a single table.
| Sonnet 4.6 | Sonnet 5 | Opus 4.8 | |
|---|---|---|---|
| SWE-bench Verified | 79.6% | 85.2% | 80.8% |
| SWE-bench Pro | 58.1% | 63.2% | 69.2% |
| Terminal-Bench 2.1 | 67.0% | 80.4% | — |
| Input price (per M tok) | $3 | $2 (launch) | $5 |
| Output price (per M tok) | $15 | $10 (launch) | $25 |
| Context window | 1M | 1M | 1M |
| Best for | (retired) | Default for everything | Hardest reasoning |
If you read nothing else: Sonnet 5 is the new default, Opus is the escalation, and Sonnet 4.6 is over. The full launch context is in everything you need to know about Claude Sonnet 5.
Sonnet 5 vs Sonnet 4.6: An Easy Call
This is the clearest decision in the lineup. Sonnet 5 beats Sonnet 4.6 on every dimension:
- SWE-bench Verified: 85.2% versus 79.6%, a 5.6 point gain
- SWE-bench Pro: 63.2% versus 58.1%, a 5.1 point gain
- Terminal-Bench 2.1: 80.4% versus 67.0%, a 13.4 point gain
- BrowseComp: 84.7% versus roughly 60%, a 25 point gain
And here is the kicker. During launch pricing through August 31, 2026, Sonnet 5 costs $2/$10 per million tokens, less than Sonnet 4.6's standard $3/$15. You get a strictly better model for less money. There is no argument for staying on 4.6, and migrating is usually as simple as changing the model ID.
Sonnet 5 vs Opus 4.8: The Interesting One
This is where teams actually have to think. On paper, Sonnet 5 is the mid-tier and Opus 4.8 is the flagship, but the benchmarks blur that line.
Where Sonnet 5 wins or ties
- SWE-bench Verified: 85.2% versus 80.8%, Sonnet 5 is ahead
- Agentic browser and terminal work: comparable, both strong
- Price: $2/$10 versus $5/$25, Sonnet 5 is roughly 60% cheaper
Where Opus 4.8 still wins
- SWE-bench Pro, the hardest multi-file fixes: 69.2% versus 63.2%
- Deep, novel reasoning: complex algorithm design, subtle debugging
- High-stakes analysis where a small edge compounds into large value
The practical rule is default to Sonnet 5, escalate to Opus. Run your agentic pipelines and everyday coding on Sonnet 5. When a task stalls or the quality clearly is not good enough, promote just that task to Opus. Most teams find 85 to 90% of their volume runs fine on Sonnet 5.
Where Haiku 4.5 Fits
Do not forget the budget tier. Haiku 4.5 at $1/$5 per million tokens is the right call for simple, high-volume work: classification, extraction, routing, and short transformations where you do not need multi-step reasoning. It is weaker on agentic tasks, so it is a complement to Sonnet 5 in a routing setup, not a replacement. A well-designed system sends the easy sub-tasks to Haiku and the real work to Sonnet 5.
A Decision Framework
Ask three questions in order.
| Question | If yes |
|---|---|
| Is this simple, high-volume, cost or latency sensitive? | Haiku 4.5 |
| Is this everyday coding, agentic execution, document work, or research? | Sonnet 5 (about 85% of work) |
| Did Sonnet 5 visibly struggle, or is this high-stakes reasoning? | Opus 4.8 |
That is the entire framework. The full breakdown by task type is in our model selection guide.
Cost Impact of Getting This Right
The pricing gap is large enough that model choice is a real budget lever. Consider a team running 200 million input and 40 million output tokens per month.
| Model | Monthly cost (launch pricing) |
|---|---|
| Sonnet 5 | 200 x $2 + 40 x $10 = $800 |
| Opus 4.8 | 200 x $5 + 40 x $25 = $2,000 |
That is a $1,200 per month difference, or $14,400 per year, for the same workload. If Sonnet 5 handles it at equivalent quality, and for most workloads it does, defaulting to Opus is simply overpaying. We model more scenarios in the pricing guide.
How to Actually Run This in Production
The best-performing teams do not pick one model and forget it. They configure a default and a fallback. Set Sonnet 5 as the default for nearly everything, keep Opus 4.8 available for escalation, and route trivial sub-tasks to Haiku. Add a simple rule: if Sonnet 5 fails a task twice or a human flags the output as insufficient, retry on Opus. This captures most of Opus's quality on the few tasks that need it, without paying Opus prices on the many that do not.
The Bottom Line
For a fresh start in 2026, make Sonnet 5 your default model, keep Opus 4.8 configured as a fallback for hard tasks, and retire Sonnet 4.6. That single configuration captures the best price-performance Anthropic currently offers, and the launch-pricing window through August 31 makes now the ideal moment to standardize on it.
Frequently Asked Questions
Is Claude Sonnet 5 better than Opus 4.8?
On most coding and agentic benchmarks, yes or effectively tied, including a higher SWE-bench Verified score of 85.2% versus 80.8%. Opus 4.8 leads only on the hardest reasoning-heavy tasks like SWE-bench Pro. For the large majority of real workloads, Sonnet 5 is the better default at roughly 40% of the cost, with Opus reserved for escalation.
Should I upgrade from Sonnet 4.6?
Yes, immediately. Sonnet 5 is better on every benchmark, with especially large gains on agentic browser and terminal tasks, and during launch pricing it costs less than Sonnet 4.6's standard rate. You get a strictly better model for less money, and migration is usually just a model-ID change. There is no scenario where staying on 4.6 is the right call.
Which model is cheapest for coding agents?
Sonnet 5 offers the best price-to-performance for agentic coding, delivering near-Opus quality at $2/$10 per million tokens during launch pricing. Haiku 4.5 at $1/$5 is cheaper but noticeably weaker on multi-step work, so it suits simple high-volume tasks rather than autonomous agents. The smart pattern is Sonnet 5 for real agent work with Haiku handling trivial sub-tasks.
When is Opus worth it?
For deep reasoning, hard multi-file refactors with subtle dependencies, difficult debugging, and high-stakes analysis where a small quality gain has large downstream value. In those cases the extra cost of $5/$25 per million tokens is justified. For routine agentic and coding work, Sonnet 5 recovers most of Opus's quality at a fraction of the price, so reserve Opus for escalation.
Do these models share the same context window?
Yes, all three offer a 1 million token input context, so choosing the mid-tier Sonnet 5 does not cost you any context. Both Sonnet 5 and Opus 4.8 handle whole-codebase and long-document work comfortably. The decision therefore comes down to reasoning depth and cost rather than context size, which simplifies the choice considerably.
What is the simplest rule for choosing?
Default to Sonnet 5 for everyday coding, agentic execution, and document work, which is about 85% of real workloads. Use Haiku 4.5 for simple high-volume tasks like classification and extraction. Escalate to Opus 4.8 only when Sonnet 5 visibly struggles or the task demands high-stakes reasoning. And retire Sonnet 4.6 entirely, since Sonnet 5 supersedes it on quality and price.
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