Lovable, a developer platform with millions of users, ran Opus 5 on its internal evaluations and noted the gains extend beyond raw scores: "It isn't just better on our hardest agentic coding tasks, up 22% over Opus 4.7, it's steadier, with far less variance run to run," Fabian Hedin said in a statement shared by Anthropic.
The benchmarksIt may sound strange, but Opus beats Fable on almost everything that will matter to the everyday user while not being labeled as Mythos-class like Fable.
On Frontier-Bench v0.1—a benchmark that tests whether AI coding agents can complete real software engineering tasks end-to-end, scored as a percentage of tasks passed—Opus 5 hit 43.3%. Fable 5 came in at 33.7%. OpenAI's GPT-5.6 Sol, Anthropic's main commercial rival, scored 34.4%.
The widest margin is on ARC-AGI-3, a test of genuine problem-solving built around novel puzzles a model couldn't have memorized from training data, scored as a percentage of puzzles solved. Opus 5 hit 30.2%; GPT-5.6 Sol scored 7.8%; and Fable 5 wasn't tested at all. On GDPval-AA v2—a knowledge work benchmark scored via Elo ratings, the chess-style ranking system used to measure relative performance on real professional tasks—Opus 5 reached 1,861 against Fable 5's 1,747 and GPT-5.6 Sol's 1,736.
Zapier tested Opus 5 on AutomationBench, an evaluation that scores whether a model can carry a full business workflow from start to finish without human help. Their verdict: the model "took a raw account-health workbook and ran a full churn-prevention sequence end to end: flagging at-risk accounts, alerting the right owner, and summarizing for retention ops. Previous models didn't pass; Opus 5 hit 100%."
Anthropic is also pitching Opus 5 as a research upgrade. Ultima Genomics, a DNA sequencing company, said the model "behaves more like a careful scientist than any model we've run. It reaches for the right statistical tests to rule out confounders, cross-checks its own results by independent methods, and stays on track through long multi-step analyses."
That said these two areas—legal and health—are the only ones in which Fable 5 excels by a tiny margin.
The release lands a week after Moonshot AI, a Beijing-based startup backed by Alibaba, unveiled Kimi K3—a 2.8-trillion-parameter open-weight model (meaning anyone can download the underlying code to run it independently) that Moonshot describes as the world's largest open AI system. Independent benchmarks consistently place Kimi K3 third overall, behind both Fable 5 and GPT-5.6 Sol, beating those two in specific areas.
Opus 5 is available now via API at $5 per million input tokens and $25 per million output. (Tokens are the basic unit of information an AI model can process in both input and output). A Fast mode running at roughly 2.5 times the default speed is also available, at twice the base price—$10 per million input tokens and $50 per million output.
This release may end the anxiety over Fable 5's lack of public availability. Opus is also available via subscription for everyone.
