Claude Opus 5.5 vs Claude Sonnet 5.5: Frontier vs Everyday Default (2026)
Claude Opus 5.5 vs Claude Sonnet 5.5 on verified fields: $4.00/$20.00 vs $2.00/$10.00 per M tokens, the leaderboard's everyday-default label, and a price-ratio caveat. Verdict first.
Verdict: Pick Claude Sonnet 5.5 as the default for everyday coding API work. The leaderboard we verify against calls it “the everyday default,” with quality close to Opus at a lower price. Pick Claude Opus 5.5 when the hardest reasoning or long-form output is the job, and accept the source’s own warning that it carries the highest output price of any frontier model.
Scorecard
Verified fields only, taken from the public coding leaderboard at llm-stats (read 2026-10-14). Anything the leaderboard leaves blank stays blank here. Arena numeric values were not captured for this post and are not printed.
| field | claude opus 5.5 | claude sonnet 5.5 |
|---|---|---|
| leaderboard label | frontier reasoning + nuanced long-form prose | the everyday default |
| source warning | highest output price of any frontier model; not the default for cost-sensitive work | trails Opus on the hardest reasoning and agent benchmarks |
| input / output per M tokens | $4.00 / $20.00 | $2.00 / $10.00 |
| context window (header table) | 1.0M tokens | 1.0M tokens (see the note below) |
How the leaderboard scores these two
The leaderboard combines two signals. The first is arena performance: blind human votes in a coding arena where four randomly sampled models answer the same prompt and the user picks the best output without knowing which model wrote it. Arena ratings use a conservative TrueSkill estimate. The second is benchmark scores such as SWE-bench Verified, which tests real GitHub issue resolution. The page says the arena side carries more weight, because it measures end-to-end coding on open-ended tasks. Both models sit near the top of that list, so the choice comes down to price and task shape, not to a single leaderboard position.
Opus 5.5’s edge
Opus 5.5 is recorded for frontier reasoning and for long-form coherence: voice and structure that hold across thousands of tokens. That matters for long specifications, multi-step agent runs where one early mistake spreads, and synthesis of large documents. The price is the trade. The source names Opus as the highest output-priced frontier model at $20.00 for each million output tokens (llm-stats), and it says Opus is not the default for cost-sensitive workflows. We quote that wording rather than paraphrasing it into a softer claim.
Sonnet 5.5’s edge
Sonnet 5.5 is the entry the source points to first for day-to-day work. It lists at $2.00 input and $10.00 output per million tokens (llm-stats), and the page describes it as competitive with Opus on most non-frontier tasks. The recorded weakness is narrow: it trails Opus on the hardest reasoning and agent benchmarks. If your workload is code review, routine feature work, or high-volume generation, that is the trade most teams accept first.
A note on the price ratio and the context window
The rate card and the “roughly 5x” label do not match. $4.00 against $2.00 and $20.00 against $10.00 are both 2x (llm-stats lists both rates). The page may be describing effective cost in a different way, but it does not explain the method, so this post does not repeat the 5x figure as arithmetic. The context figure has a similar problem. The header table lists 1.0M tokens for Sonnet, while the capsule for Sonnet mentions a 200K context with consistent recall. Before you design a pipeline around either number, open the model pages and confirm the window.
Which job fits which model
- Claude Opus 5.5: frontier-tier jobs where output price is secondary to quality, such as long-form reasoning and the hardest agent work.
- Claude Sonnet 5.5: everyday coding assistance, code review and high-volume API work, where a per-token budget has to stay predictable.
Before you choose: a short checklist
- Take 20 real prompts from your own backlog and run them through both models.
- Count output tokens, not input tokens, when you estimate the bill, because output is where the listed prices diverge most.
- Check whether your task needs the frontier tier at all. Many do not.
- Confirm current rates on the vendor’s pricing page before you commit. Prices move, so treat these figures as a starting point (verified 2026-10-14).
Limits of this comparison
Arena rank is absent here for both models, because those numeric values were not captured in this run. Our own benchmark runs are not included. It does not tell you how either model handles your language, your framework or your codebase style. Those answers come from your own tests.
Context
On the model track of our 2026 ranking, Sonnet is fifth and Opus eighth, each scored with the model-track formula. For the subscription side of the same market, see the Cursor vs GitHub Copilot comparison. Method: /methodology.
FAQ
Which is better, Claude Opus 5.5 or Claude Sonnet 5.5?
On the coding leaderboard we verify against, Opus 5.5 is the frontier-quality entry for frontier reasoning and nuanced long-form prose, while Sonnet 5.5 is labeled the everyday default: quality close to Opus at a fraction of the cost. The same leaderboard warns that Opus has the highest output price of any frontier model and is not the default pick for cost-sensitive work.
How big is the price gap?
The listed rates are $4.00 input / $20.00 output per million tokens for Opus and $2.00 input / $10.00 output for Sonnet, so the listed gap is 2x on both sides. The leaderboard describes Sonnet as roughly 5x cheaper, which does not match its own rate card. Use the listed rates and confirm current prices on the vendor's page (verified 2026-10-14).
Are these tools or models?
Models. They are API entries billed per million tokens, not subscription products. If you want a subscription that works on a whole repository, that is Claude Code, the tool-track entry in our ranking.