Head-to-head
Claude Opus 5 vs Claude Fable 5: which AI model wins in 2026?
Claude Opus 5 ($25/1M out) and Claude Fable 5 ($50/1M out) are two of the most-used AI models in 2026. Across 8 community votes, Claude Opus 5 leads with 63% approval.
Quick verdict
On Reasoning, Claude Opus 5 and Claude Fable 5 are tied at 5/5. On budget, Claude Opus 5 wins: it starts at $25/1M out versus $50/1M out for Claude Fable 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 Fable 5
- 80.3% on SWE-bench Pro vs 69.2% for Opus 4.8, 58.6% for GPT-5.5 and 54.2% for Gemini 3.1 Pro, roughly 11 points ahead of the next frontier model
- 95.0% on SWE-bench Verified (Opus 4.8: 88.6%, GPT-5.5: 82.6%) and 29.3% on Cognition's FrontierCode Diamond split, more than double Opus 4.8's 13.4%
- Long-horizon autonomy is the real story: Stripe reported a 50-million-line Ruby codebase migration done in one day instead of 2+ months, and Cursor's CEO calls it state of the art on CursorBench
- Field reports match the benchmarks: HN engineers describe it working 'like an actual engineer' (CRDTs with minimal hand-holding, writing its own fuzzers, one 46x allocation reduction), Simon Willison measured 'several days' worth of work' in a single session
- 1M token context window by default plus 128K output, and state-of-the-art vision on dense documents (29.8% on GDP.pdf vs 24.9% for GPT-5.5 and 22.5% for Opus 4.8)
- Refused-before-output requests are not billed, and server-side fallback to Opus 4.8 with fallback credit is built into the API
- Double the price of Opus 4.8 ($10/$50 vs $5/$25) and slow: single requests on hard tasks routinely run many minutes, Simon Willison bluntly calls it 'slow, expensive'
- Dual-use safety classifiers misfire on legitimate work: a medical physicist reported fluid dynamics problems and MRI segmentation code refused as biosecurity risks, with requests silently rerouted to Opus 4.8 (the viral HN thread was titled 'If Claude Fable stops helping you, you'll never know'; Anthropic says under 5% of sessions)
- Rocky launch: US export controls forced Anthropic to suspend access worldwide from June 12 to June 30, 2026, three days after release, with full restoration only on July 1
- Requires 30-day data retention and is not available under zero data retention, a hard blocker for strict-compliance orgs; also no thinking-off mode, raw chain of thought never returned, assistant prefill returns a 400
- Not universally state of the art: GPT-5.5 still leads ARC-AGI-2 (85.0% vs 77.1%), and Andon Labs found unblocked Mythos 5 underperformed both Opus 4.7 and GPT-5.5 on Vending-Bench, with reasoning that optimized for detectability rather than actual harm
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 Fable 5
Take Claude Fable 5 if your workload is genuinely long-horizon: overnight agentic runs, monster migrations, tasks where one multi-hour session replaces days of supervised work. There, the 2x premium over Opus 4.8 pays for itself in task compression, and the benchmarks (80.3% SWE-bench Pro, 11 points clear of the field) are backed by real deployments at Stripe and Cursor. For interactive coding and everyday work, stay on Opus 4.8: 88.6% on SWE-bench Verified at half the price, no classifier misfires, faster turns. Cost-sensitive teams get near-Opus coding from Sonnet 5 at $3/$15 (intro $2/$10 through August 2026). Avoid Fable 5 entirely if your org requires zero data retention or if you work anywhere near biology, medical imaging or security tooling, where the dual-use classifiers still produce false positives and silently swap in Opus 4.8 mid-session.
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 Fable 5
“I do medical imaging research and the bio classifier keeps flagging my MRI segmentation prompts, then it silently falls back to Opus 4.8 mid-session. At $50 per million output tokens I expect to at least know which model actually answered me.”
“Yes it's 2x the price of Opus and yes the turns are slow. But one overnight Fable run replaced what used to be a week of supervising shorter runs. On a per-task basis it's actually the cheapest model we use.”
“The 1M context is real, not marketing. I fed it our entire service mesh config plus six months of incident postmortems and it traced a flaky timeout to a retry policy nobody remembered writing. Opus 4.8 never connected those dots.”
“Gave it a monorepo migration that Opus 4.8 kept stalling on. It ran for about 40 minutes, came back with the whole thing done plus a test harness it wrote for itself. Felt like reviewing a senior engineer's PR, not babysitting a chatbot.”
Keep comparing
Frequently asked questions
Is Claude Opus 5 better than Claude Fable 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 Fable 5?
Claude Opus 5 is cheaper: it starts at $25/1M out, while Claude Fable 5 starts at $50/1M out.
How much do Claude Opus 5 and Claude Fable 5 cost per 1M tokens?
Claude Opus 5: $5/1M in per 1M input tokens, $25/1M out per 1M output tokens. Claude Fable 5: $10/1M in per 1M input tokens, $50/1M out per 1M output tokens.