Claude Fable 5 is an AI model released by Anthropic on Tuesday, Jun 9 2026, 12 days after Claude Opus 4.8. It has a 1M token context window. Benchmark results (shown below) cover BullshitBench v2, SWE-Bench Pro, SWE-Bench Verified, CursorBench v3.1, DeepSWE 1.0, Next.js Evals, and 11 more.
Benchmarks
Nonsense detection
BullshitBench v2Given a confidently-worded but nonsensical prompt, does the AI spot that it makes no sense and push back — instead of playing along and inventing an answer? The score is how often it clearly called out the nonsense. Higher is better.
54%
Agentic coding
SWE-Bench ProCan the AI fix real bugs in real software? It's handed actual problems from open-source projects and has to write code that genuinely solves them. Higher is better.
80.3%
Coding
SWE-Bench VerifiedReal coding tasks pulled from open-source projects — the AI has to find and fix actual bugs. A human-checked version of the original SWE-Bench. Higher is better.
95.5%
Agentic coding
CursorBench v3.1Cursor's own test of harder, real-world coding tasks inside a code editor. Higher is better.
72.9%
Agentic coding
DeepSWE 1.0Artificial Analysis' independent test of deep, agentic software-engineering work — the AI has to plan and carry out substantial coding tasks end to end. Higher is better.
66.1%
Next.js coding
Next.js EvalsVercel's open eval of how well AI coding agents build and migrate real Next.js apps — measured as the share of tasks the agent completes successfully. Higher is better.
92%
Agentic terminal coding
Terminal-Bench 2.1Can the AI work in a command-line terminal — running commands and finishing technical setup tasks the way a developer would? Higher is better.
88%
Web browsing
BrowseCompCan the AI browse the web and track down hard-to-find answers? Higher is better.
86.9%
Multidisciplinary reasoning
Humanity's Last ExamHumanity's Last Exam — extremely hard expert questions across many subjects. “With tools” means the AI is allowed to search the web or run code while answering. Higher is better.
64.5%
with tools
Agentic computer use
OSWorld-VerifiedCan the AI actually operate a computer — clicking, typing, and using real apps — to finish tasks on its own? Higher is better.
85%
Agentic legal work
Harvey's Legal Agent BenchmarkHarvey's test of whether an AI agent can complete real legal work — drafting and reviewing documents, working with spreadsheets and presentations, and navigating files the way a lawyer's assistant would. Higher is better.
11.25%
Tax questions
TaxEval v2A set of real tax questions created by Vals AI — can the AI give accurate answers about tax rules and filings? Higher is better.
76.94%
Medical admin work
MedScribeCan the AI support doctors with their administrative work, like notes and paperwork? Created by Vals AI. Higher is better.
88.52%
Knowledge work
GDPval-AAMeasures how well the AI does economically valuable knowledge work, judged against human experts. Shown as a rating (like a chess Elo) — higher is better.
1932
Knowledge work
GDPval-AA v2economically valuable knowledge work (v2, re-based Elo)
1760
Community preference
Arena Elo (Text)Real people chat with two anonymous AIs side by side and vote for the answer they prefer. Votes become a chess-style Elo rating on arena.ai — it measures which AI people actually like, not test scores. Higher is better.
1509
Community preference (code)
Arena Elo (Code)Like the text arena, but people vote on which AI writes better code. The votes become a chess-style Elo rating on arena.ai. Higher is better.
1649
About Claude Fable 5
Claude Fable 5, released June 9, 2026, is the first model of Anthropic's Claude 5 generation and the debut of the Mythos-class tier that sits above Opus in the lineup. It posted the largest single-release jump in the tracker's dataset: 95.5% on SWE-Bench Verified, 80.3% on SWE-Bench Pro, 88.0% on Terminal-Bench 2.1, and a WebDev Arena coding Elo of 1649 — over 80 points clear of the next model at launch.
Fable 5 ships with a 1M-token context window and leads agentic evaluations including OSWorld-Verified (85.0%) and Artificial Analysis GDPval (1932 Elo). Anthropic offers the same underlying model without additional dual-use safety measures as Claude Mythos 5 to approved organisations. Claude Sonnet 5 followed on June 30, 2026, bringing the 5-series to the mid tier.