Head-to-head
Claude Opus 5 vs Claude Sonnet 5: which AI model wins in 2026?
Claude Opus 5 ($25/1M out) and Claude Sonnet 5 ($15/1M out ($10 intro until 2026-08-31)) are two of the most-used AI models in 2026. Across 7 community votes, Claude Opus 5 leads with 63% approval.
Quick verdict
On Reasoning, pick Claude Opus 5: the arena rates it 5/5 against 4.5/5 for Claude Sonnet 5. On budget, Claude Sonnet 5 wins: it starts at $15/1M out ($10 intro until 2026-08-31) versus $25/1M out for Claude Opus 5.
Line-by-line comparison
Strengths and weaknesses
Claude Opus 5
- Ranked #1 in composite intelligence across 190 models on Artificial Analysis at launch, and 43.3% on Frontier-Bench v0.1 vs 34.4% for GPT-5.6 Sol and 33.7% for Claude Fable 5
- 3.9x better than GPT-5.6 Sol on ARC-AGI-3 novel reasoning (30.2% vs 7.8%), and Elo 1861 on GDPval-AA v2 economic knowledge work, ahead of Fable 5 (1747)
- 79.2% on SWE-bench Pro, within a point of Fable 5 (80.0%) and 10 points above Opus 4.8 (69.2%), at half Fable's price; Cursor's co-founder calls it 'near Fable 5 intelligence at Opus speed and cost'
- Same $5/$25 pricing as Opus 4.8 with a bigger window: 1M context is now the default and only tier, with 128K max output and prompt caching from 512 tokens
- Dual-use safety classifiers trigger 85% less often than on Fable 5, and the new default fallback mode avoids the silent mid-session refusals that plagued Fable's launch
- Self-verifies its work without being told, handles mid-conversation tool changes (beta) without busting the prompt cache, and ships day one on Claude.ai, the API, Bedrock, Vertex and Microsoft Foundry
- Notably slow and very verbose: 52.6 output tokens/s and 68 seconds to first token on Artificial Analysis, and it consumed ~100M output tokens during their eval vs a 63M median
- The verbosity is a real-world cost problem: CodeRabbit measured it reading ~50% more and writing ~65% more than reference frontier models per code-review call
- No actual price cut despite the 'cost-efficient' narrative: identical to Opus 4.8 ($5/$25), nearly GPT-5.6 money ($5/$30), and more than 2x comparable Gemini or Grok tiers
- Reviewers describe a 'brilliant but annoying' personality: over-verification, hedging, and occasional refusals of mundane tasks like resolving a merge conflict (Lenny's Newsletter field review)
- Breaking API change for Opus 4.8 migrants: thinking is on by default and cannot be disabled at xhigh or max effort (returns a 400); Fast mode ($10/$50, ~2.5x faster) is API-only, not on Bedrock or Vertex
Claude Sonnet 5
- Large agentic gains over Sonnet 4.6: Terminal-Bench 2.1 80.4% vs 67.0%, OSWorld-Verified 81.2% vs 78.5%, SWE-bench Pro 63.2% vs 58.1%
- Matches Opus 4.8 on knowledge work (GDPval-AA v2: 1,618 vs 1,615) and nearly ties it on Humanity's Last Exam with tools (57.4% vs 57.9%) at 60% of Opus 4.8 pricing (40% during the intro window)
- 1M token context window and 128K max output; introductory pricing of $2/$10 per 1M tokens through Aug 31, 2026
- Persistent self-verifying agent behavior: hands-on reviews note it tests its own code and iterates on hard problems until solved, unlike Sonnet 4.6
- First Sonnet with xhigh effort level and high-resolution vision (2576px images); adaptive thinking enabled by default
- Higher code-review precision than Sonnet 4.6 (38-40% vs 29%), producing fewer false-positive findings
- New tokenizer inflates token counts roughly 30% for the same text (1.0-1.35x per Anthropic; ~1.4x English, ~1.28x Python measured by Simon Willison), raising effective cost despite the unchanged sticker price
- Verbose and token-hungry: ~$2.29 per task vs ~$1.20 for Sonnet 4.6 in independent tests (ranked 101st of 161 for cost efficiency); at high effort cost-per-task can exceed Opus 4.8
- Measurably slower than Sonnet 4.6 on small routine edits and prone to over-engineering simple tasks (CodeRabbit hands-on review)
- Sampling parameters (temperature, top_p, top_k) removed; non-default values return a 400 error, breaking existing pipelines
- Launch sentiment on HN/Reddit was mixed: the '5' label was seen as overpromising, and stricter cybersecurity safeguards can refuse benign security-adjacent work
Cast your verdict
One recommendation per tool per gladiator. It reshapes the crowd score everyone sees.
The arena’s verdict on Claude Opus 5
Claude Opus 5 is the sane default of the Series 5 range: most of Fable 5's intelligence (and more than Fable on Frontier-Bench and GDPval) at exactly half the token price, with classifiers that trigger 85% less often. If you migrated workloads to Fable 5 for capability but resent the bill or the false-positive refusals, move them here; if you are still on Opus 4.8, the upgrade is 10 SWE-bench Pro points for free. The two honest reasons to look elsewhere: latency and verbosity. At 52.6 tokens/s with 68s to first token it is a poor fit for interactive UX, and its token appetite quietly inflates real costs beyond the sticker price, so budget-sensitive high-volume pipelines still belong on Sonnet 5, Gemini or DeepSeek. Keep Fable 5 only for the longest autonomous runs where its slight SWE-bench Pro edge compounds.
The arena’s verdict on Claude Sonnet 5
Choose Sonnet 5 if you run coding, terminal or computer-use agents and want near Opus 4.8 quality at Sonnet prices, especially during the $2/$10 intro window; it is a strict upgrade over Sonnet 4.6 at low and medium effort. Budget for the new tokenizer and its verbosity: real per-task costs run well above Sonnet 4.6, and at the highest effort levels Opus 4.8 can be the better deal per solved task. Avoid it for latency-sensitive small edits or pipelines that rely on temperature and top_p, which now error. Sonnet 4.6 remains the pragmatic pick for high-volume tiny-diff workloads.
What the crowd says
On Claude Opus 5
“The sticker price is unchanged but my invoice is not: it writes essays where Opus 4.8 wrote answers. 68 seconds to first token killed it for our support chat, we went back to Sonnet 5.”
“Fed it a 40-tab financial model with cross-sheet formulas and asked for a scenario deck. It got the edge cases the analysts missed. For document-heavy enterprise work this is the best model I have used.”
“We moved off Fable 5 because the bio classifier kept flagging our genomics tooling. Opus 5 does the same work at half the price and I have not seen a single silent reroute since.”
“Migrated our agents from Opus 4.8 the day it dropped. Same bill, and tasks that used to stall at the planning stage now just finish. The 10-point SWE-bench jump is not marketing, our merge queue feels it.”
On Claude Sonnet 5
“Cheap per token, pricey per task. Independent tests had it near $2.29 a task vs $1.20 on 4.6, and at high effort it can out-cost Opus 4.8. It will not stop talking.”
“Terminal-Bench going 67 to 80 over Sonnet 4.6 matches what I see. My CI-fix agent went from constant babysitting to mostly hands-off overnight.”
“Matches Opus 4.8 on knowledge work at 60% of the price, and the intro $2/$10 window makes it silly value. My research agent runs on Sonnet 5 now, zero regrets.”
Keep comparing
Frequently asked questions
Is Claude Opus 5 better than Claude Sonnet 5?
The crowd currently sides with Claude Opus 5: 63% recommend it, versus 57% for Claude Sonnet 5 (7 votes). On Reasoning, Claude Opus 5 rates higher (5/5 vs 4.5/5). The right pick depends on your use case. The line-by-line comparison on this page breaks down pricing, key specs and arena ratings.
Which is cheaper, Claude Opus 5 or Claude Sonnet 5?
Claude Sonnet 5 is cheaper: it starts at $15/1M out ($10 intro until 2026-08-31), while Claude Opus 5 starts at $25/1M out.
How much do Claude Opus 5 and Claude Sonnet 5 cost per 1M tokens?
Claude Opus 5: $5/1M in per 1M input tokens, $25/1M out per 1M output tokens. Claude Sonnet 5: $3/1M in ($2 intro until 2026-08-31) per 1M input tokens, $15/1M out ($10 intro until 2026-08-31) per 1M output tokens.