Claude Opus 5
Current flagship Opus. A generation past 4.8, same list price.
Claude Opus 5 is the current flagship of the Claude line — the deepest-reasoning model Anthropic ships, and the one to use when being wrong is more expensive than the call.
It is not the model most people should run by default. Sonnet 5 carries the same 1M-token context window and costs a fraction as much, and on ordinary work it holds up. Opus 5 earns its price on problems where you want the long tail of findings rather than just the obvious answer, and on long agent chains where one bad step invalidates everything after it.
We sell it at half Anthropic’s list price — $2.50 per million input tokens against $5.00. Same model id, same weights, same API. The point of buying it here is that escalating to the flagship stops being a budget decision.
What it costs you per month
Real-world budget scenarios. Numbers are simple sums — official list price vs llmrelay's 50% off tier.
$0.0152 for a full code review
Rate cards quote price per million tokens, which is not a unit anyone budgets in. So we ran one concrete task and read the billed amount out of our own logs: 875 output tokens, 19.7s, $0.0152.
The same task on Claude Sonnet 5 cost $0.0047 — this model is 3.27× more expensive per task.
One real code review: find a concurrency bug in a Python billing function, identify two lesser issues, and rewrite it correctly. temperature=0, identical prompt to both models. Measured 31 July 2026. The figure is what our billing system actually charged, not an estimate from the rate card. One run, one task — a cost measurement, not a quality benchmark. Full method and both answers side by side →
What it's good at
- +Deepest reasoning in the Claude line
- +Long-horizon agent tasks
- +Strong tool use
Best for
- — Agentic coding
- — Research and analysis
- — Claude Code / Cursor
Tools that ship well with Claude Opus 5
Pick Claude Opus 5 when
- +Review work where you want the smaller findings too, not just the headline bug. That is what it demonstrably gave us for the extra money in our own measurement.
- +Anything where being wrong is expensive: auth logic, schema migrations, payment paths. A second opinion costing a cent or two is not the line item to optimise.
- +Long-horizon agent runs. One poisoned step early can waste an entire chain, which dwarfs the per-call premium.
- +Reproducibility. Model ids in this generation are pinned snapshots rather than moving pointers, so behaviour you validated stays put.
Choose something else when
- !Day-to-day coding. On one real code review Sonnet 5 found every issue that mattered and gave a tighter fix, for roughly a third of the cost.
- !High-volume or looping work — test generation, batch refactors, CI comments. Our measured per-task gap was 3.27x, which at scale is the whole budget rather than a rounding error.
- !Work you are going to read and verify yourself anyway. You are already the review layer.
- !Creative and narrative writing, where Fable 5 is the purpose-built model at the same list price.
Questions people ask about Claude Opus 5
How much does Claude Opus 5 cost?
Anthropic’s list price is $5.00 per million input tokens and $25.00 per million output tokens. On llmrelay it is $2.50 and $12.50 — exactly half list, with no volume commitment and no subscription. Billing is prepaid per token from a single credit pool.
Is Opus 5 worth it over Sonnet 5?
Sometimes, and less often than the marketing implies. We measured one identical code review on 31 July 2026: Opus 5 billed $0.0152 and Sonnet 5 billed $0.0047, a 3.27x gap. Both found the concurrency bug, the SQL injection and the unsafe cache. What the extra money bought was breadth — Opus 5 also caught an unused import, added input validation and explained why the cache made the race worse. Worth it for high-stakes review; not worth it as a default.
Why did Opus 5 cost 3.27x when its rate is only 2.5x higher?
Because it wrote more. On the same prompt at temperature=0 it emitted 875 output tokens against Sonnet 5’s 592, and those extra tokens bill at the higher output rate. That is the gap between cost per token and cost per task, and it is why a rate card understates the real difference between tiers on output-heavy work.
What is the context window on Claude Opus 5?
1,000,000 tokens, with up to 128,000 output tokens. Note that Claude Sonnet 5 has the same 1M window, so long-context work by itself is not a reason to pay the flagship rate.
Can I use Opus 5 with Claude Code, Cursor or Cline?
Yes. We serve an OpenAI-compatible and Anthropic-compatible endpoint, so any tool that lets you set a base URL and an API key works. Point it at https://api.llmrelay.dev/v1 and use the model id claude-opus-5.
Try Claude Opus 5 at half the price
Free to create an account, no subscription, $10 minimum top-up — enough to run this model against a real task and judge quality yourself.
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