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claude-opus-5vsclaude-sonnet-5Both are available on APICLAN through one OpenAI-compatible endpoint, so switching between them is a one-word change. Here is what each actually costs you, and how much the difference is worth at your volume.
claude-sonnet-5 runs about
60% cheaper than claude-opus-5. Both models are from
the same family.Percentages are easy to shrug off. Put your real monthly volume in and see the number in dollars.
The list-price gap between these two is the widest inside the Claude family: $25 versus $10 per million output tokens. The obvious move when a bill hurts is to drop down a tier. Quite often that is the wrong lever.
We pulled one real session off our own logs: 30 requests, $1.13 charged. 63% of it was cache writes — context being rewritten, producing no output at all. Cache reads cost 10% of the input price. Cache writes cost 125%. Same tokens, twelve times apart, depending only on direction.
A workload shaped like that spends most of its money moving context around, not
generating answers. Moving from claude-opus-5 to
claude-sonnet-5 would have cut that bill by far less than simply
keeping the context stable between calls so the cache gets read instead of
rewritten.
So the order of operations is: look at your cache-write share first. If it is large, fix that. If it is small and output tokens dominate, then the tier change is the real saving and it is worth testing.
We do not publish capability benchmarks, and you should be sceptical of anyone who does. Scores on public benchmarks rarely predict how a model behaves on your codebase, your prompts and your edge cases.
What we can tell you is exactly what each one costs. Run both against a real task from your own workload — switching takes one word — and let the cheaper one win unless it visibly fails.
A practical approach that works well in agent loops: route the bulk of calls to the cheaper model, and escalate to the more expensive one only when the first attempt fails a check. Most workloads are dominated by routine calls, so the blended cost lands close to the cheap model rather than the expensive one.
Same endpoint, same key, same request shape. Only the model string changes.
- model="claude-opus-5",
+ model="claude-sonnet-5",If you have not connected yet, the quickstart takes about thirty seconds — you change your base URL and nothing else.
Prices verified 2026-10-10 and regenerated automatically from live billing data. List prices change; this page follows them.