Claude Opus 5 vs Claude Sonnet 5
Claude Opus 5 vs Claude Sonnet 5
Opus 5 leads on every comparison that resolves. DeepSWE (74.0 vs 54.0), Humanity's Last Exam without tools (54.9 vs 41.3), LiveBench (80.1 vs 76.0), and LiveCodeBench (89.03 vs 82.43) are all confirmed real gaps, independently run on both sides, none of them close — the smallest margin is 4.1 points against a 2.7-point noise floor. SWE-bench Verified and GPQA Diamond both score close together (97.0 vs 79.6, 93.43 vs 88.89) but neither counts as real or tied: both benchmarks are graded saturated on this site, so a close score reflects a ceiling, not evenly matched models. Terminal-Bench 2.1 is independently run on both sides but through different evaluation harnesses (Artificial Analysis for Opus 5, tbench.ai's official board for Sonnet 5) — not a fair comparison even though neither number is a vendor claim. Three benchmarks don't yield a comparable line at all: Agents' Last Exam and ARC-AGI-2 are tracked for Opus 5 only, Toolathlon-Verified for Sonnet 5 only. Sonnet 5's case is price — $2/$10 versus Opus 5's $5/$25, a 60% discount on both input and output — though Sonnet 5's newer tokenizer produces roughly 30% more tokens for the same text, so the effective cost gap runs smaller than the sticker prices alone suggest.
Benchmark by benchmark
| Benchmark | Claude Opus 5 | Claude Sonnet 5 | Signal |
|---|---|---|---|
| Reasoning(no tools) | 54.9independent | 41.3independent | Real gap |
| Terminal ops | 89.1independent | 74.6independent | Setup-dependent |
| Long-horizon coding | 74.0independent | 54.0independent | Real gap |
| Multi-tool chores | Not sourced yet | 71.6independent | |
| Professional work | 27.0independent | Not sourced yet | |
| Bug fixing | 97.0independent | 79.6independent | Tainted |
| Expert science Q&A | 93.4independent | 88.9independent | Tainted |
| Contest coding | 89.0independent | 82.4independent | Real gap |
| Compositional visual reasoning(max) | 90.4independent | Not sourced yet | |
| Composite score across 7 domains | 80.1independent | 76.0independent | Real gap |
Across 10 rows comparing Claude Opus 5 and Claude Sonnet 5: 4 rows carry a confirmed real gap, 0 rows land inside the noise band, and 6 rows carry other caveats — unverified, tainted, or run on mismatched tool setups. Read each row’s Signal label before ranking Claude Opus 5 against Claude Sonnet 5.
Who should pick which
- Coding, reasoning, or agentic work where capability is the constraint → Claude Opus 5 (four confirmed real gaps, 4.1 to 20.0 points each, every number independently run on both sides — none of them close)
- Budget-constrained or high-volume workloads → Claude Sonnet 5 (60% cheaper on both input and output at list price, even after the tokenizer difference is accounted for)
- An existing Sonnet integration already in production → Claude Sonnet 5 (hedged pick: Opus 5's wins are real and not marginal, but if the switching cost exceeds what the performance gap is worth to your workload, that's a legitimate reason to stay put)
Pricing
| Input / 1M tokens | $5.00 | $2.00 |
| Output / 1M tokens | $25.00 | $10.00 |
FAQ
Is Claude Opus 5 better than Claude Sonnet 5?
Opus 5 leads on every comparison that resolves. DeepSWE (74.0 vs 54.0), Humanity's Last Exam without tools (54.9 vs 41.3), LiveBench (80.1 vs 76.0), and LiveCodeBench (89.03 vs 82.43) are all confirmed real gaps, independently run on both sides, none of them close — the smallest margin is 4.1 points against a 2.7-point noise floor. SWE-bench Verified and GPQA Diamond both score close together (97.0 vs 79.6, 93.43 vs 88.89) but neither counts as real or tied: both benchmarks are graded saturated on this site, so a close score reflects a ceiling, not evenly matched models. Terminal-Bench 2.1 is independently run on both sides but through different evaluation harnesses (Artificial Analysis for Opus 5, tbench.ai's official board for Sonnet 5) — not a fair comparison even though neither number is a vendor claim. Three benchmarks don't yield a comparable line at all: Agents' Last Exam and ARC-AGI-2 are tracked for Opus 5 only, Toolathlon-Verified for Sonnet 5 only. Sonnet 5's case is price — $2/$10 versus Opus 5's $5/$25, a 60% discount on both input and output — though Sonnet 5's newer tokenizer produces roughly 30% more tokens for the same text, so the effective cost gap runs smaller than the sticker prices alone suggest.
Which is cheaper, Claude Opus 5 or Claude Sonnet 5?
Claude Sonnet 5 costs less per output token ($10.00 vs $25.00 per 1M tokens, official listed rates).